All-solid rechargeable battery

Abstract

The all-solid rechargeable battery according to an embodiment comprises: a plurality of all-solid cells in which unit cells each comprising a positive electrode, a solid electrolyte layer, and a negative electrode are alternately stacked with first elastic members; second elastic members positioned between adjacent all-solid cells; an exterior which accommodates the plurality of all-solid cells and second elastic members; and a third elastic member positioned between the exterior and the outermost all-solid cell, which is positioned at the outermost side among the plurality of all-solid cells, wherein the compressive strengths of the first elastic member and the second elastic member are different.

Description

All-solid-state secondary battery

[0001] The present disclosure relates to 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 embodiments are intended to provide an all-solid-state secondary battery that can prevent damage to a solid electrolyte layer by uniformly pressurizing and prevent short circuits between the positive and negative electrodes, thereby reducing the failure rate and improving performance.

[0004] According to one embodiment, an all-solid-state secondary battery includes a plurality of all-solid-state cells in which unit cells including a cathode, a solid electrolyte layer, and an anode and a first elastic member are alternately laminated; a second elastic member positioned between adjacent all-solid-state cells; an outer body accommodating the plurality of all-solid-state cells and the second elastic member; and a third elastic member positioned between an outermost all-solid-state cell positioned at the outermost end among the plurality of all-solid-state cells and the outer body, wherein the first elastic member and the second elastic member have different compressive strengths.

[0005] The compressive strengths of the first elastic member, the second elastic member, and the third elastic member may be different from each other.

[0006] When the compressive strength of the first elastic member is P1, the compressive strength of the second elastic member is P2, and the compressive strength of the third elastic member is P3, P1 < P2 < P3 may be satisfied.

[0007] When the size of the restorability of the first elastic member is R1, the size of the restorability of the second elastic member is R2, and the size of the restorability of the third elastic member is R3, R1 < R2 < R3 may be satisfied.

[0008] When the thickness of the first elastic member is T1, the thickness of the second elastic member is T2, and the thickness of the third elastic member is T3, T1 < T2 < T3 may be satisfied.

[0009] The second elastic member and the third elastic member may have adhesiveness.

[0010] The first elastic member may have heat dissipation properties, and the second elastic member and the third elastic member may have heat insulation properties.

[0011] The compressive strengths of the second elastic member and the third elastic member may be the same.

[0012] The above-mentioned all-solid-state cell may further include a pouch member that accommodates the unit cell and the first elastic member.

[0013] According to embodiments, a first elastic member alternately stacked with unit cells, a second elastic member positioned between all-solid-state cells, and a third elastic member positioned between the outermost all-solid-state cell and the outer body are included, and by differently controlling the compressive strengths of the first elastic member, the second elastic member, and the third elastic member, the pressure applied to the solid electrolyte layer when the all-solid-state cell is pressurized can be made uniform. Accordingly, the stress applied to the solid electrolyte layer can be minimized, thereby preventing damage to the solid electrolyte layer.

[0014] Therefore, it is possible to reduce the failure rate of an all-solid-state secondary battery and improve its performance by preventing short circuits between the positive and negative electrodes located on both sides of the solid electrolyte layer.

[0015] In addition, by uniformly applying pressure to the solid electrolyte layer when pressurizing the all-solid-state cell, the discharge efficiency can be improved.

[0016] Figure 1 is a cross-sectional view of an all-solid-state battery.

[0017] Figure 2 is a cross-sectional view of an all-solid-state battery including a precipitated negative electrode.

[0018] Figure 3 is a cross-sectional view of an all-solid-state secondary battery according to one embodiment.

[0019] Figure 4 is an enlarged cross-sectional view of part A of Figure 3.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] Cathode for all-solid-state secondary batteries

[0025] In one embodiment, a positive electrode for an all-solid-state secondary battery is provided, which includes a current collecting layer and a positive electrode active material layer positioned on the current collecting layer, wherein the positive electrode active material layer includes at least one of a positive electrode active material, a sulfide-based solid electrolyte, a binder, and a conductive material. However, without limitation thereto, the positive electrode for an all-solid-state secondary battery may include more or less components than the components described above.

[0026] In one embodiment, a positive electrode for an all-solid-state secondary battery is manufactured by applying a positive electrode composition including at least one of a positive electrode active material, a sulfide-based solid electrolyte, a binder, and a conductive material to a current collecting layer, followed by drying and rolling.

[0027] positive electrode active material

[0028] The cathode active material can be applied without limitation as long as it is one commonly used in all-solid-state secondary batteries. For example, the cathode active material may be a compound capable of reversible lithium intercalation and deintercalation, and may include a compound represented by any of the following chemical formulas.

[0029] Li a A 1-b X b D2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5);

[0030] 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);

[0031] Li a HAVE BEEN 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0032] Li a HAVE BEEN 2-b X b O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0033] 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);

[0034] 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);

[0035] 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);

[0036] 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);

[0037] Li a Ni 1-b-c Mr b X c O 2-αT α (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 O 2-α T2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2);

[0039] Li a Ni b HAVE BEEN c G d O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1);

[0040] Li a Ni b Co c Mr 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);

[0041] Li a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0042] Li a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0043] Li a Mr 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0044] Li a Mn2G b O4(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0045] Li a Mr 1-g G gPO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5);

[0046] QO2; QS2; LiQS2;

[0047] V2O5; LiV2O5;

[0048] LiZO2;

[0049] LiNiVO4;

[0050] Li (3-f) J2(PO4)3(0 ≤ f ≤ 2);

[0051] Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2);

[0052] Li a FePO4(0.90 ≤ a ≤ 1.8).

[0053] 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.

[0054] 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).

[0055] 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.

[0056] [Chemical Formula 1]

[0057] Li a1 Ni x1 M 1 y1 M 2 1-x1-y1 O2

[0058] 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.

[0059] [Chemical Formula 2]

[0060] Li a2 Co x2 M 3 1-x2 O2

[0061] 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.

[0062] [Chemical Formula 3]

[0063] Li a3 Fe x3 M 4 (1-x3) PO4

[0064] 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.

[0065] 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.

[0066] 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.

[0067] Sulfide-based solid electrolyte

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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 the electrode layer and the 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] bookbinder

[0078] 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.

[0079] Challenge

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] All-solid-state secondary battery

[0085] 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.

[0086] Figure 1 is a cross-sectional view of an all-solid-state battery.

[0087] 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.

[0088] cathode

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] The average particle diameter (D50) of the 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 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 are 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] Figure 2 is a cross-sectional view of an all-solid-state battery including a precipitated negative electrode.

[0107] 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.

[0108] The cathode coating layer (45) may include a metal, 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 of these or an alloy of several types. When the metal is present in the form of particles, the average particle diameter (D50) 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 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.

[0112] 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.

[0113] 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.

[0114] 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 ㎛.

[0115] 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.

[0116] solid electrolyte layer

[0117] 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.

[0118] 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.

[0119] Meanwhile, the average particle diameter (D50) of the solid electrolyte included in the positive electrode (20) may be smaller than the average particle diameter (D50) of the solid electrolyte included in the solid electrolyte layer (30). 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 (20) may be 0.1 ㎛ to 1.0 ㎛, or 0.1 ㎛ to 0.8 ㎛, and the average particle diameter (D50) of the solid electrolyte included in the solid electrolyte layer (30) may be 1.5 ㎛ to 5.0 ㎛, or 2.0 ㎛ to 4.0 ㎛, or 2.5 ㎛ to 3.5 ㎛. When 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 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.

[0121] 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.

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

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

[0124] The alkali metal salt may be, for example, a lithium salt. The content of the lithium salt in the solid electrolyte layer may be greater than 1 M, for example, from 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.

[0125] 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] 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.

[0127] 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.

[0128] The ionic liquid may be a compound comprising a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, triazolium, 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, 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.

[0130] 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.

[0131] 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 / cathode / solid electrolyte layer / cathode, or a laminated battery in which the structure of the unit cell is repeated.

[0132] 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.

[0133] Hereinafter, an all-solid-state secondary battery according to one embodiment will be described with reference to FIGS. 3 and 4.

[0134] FIG. 3 is a cross-sectional view of an all-solid-state secondary battery according to one embodiment, and FIG. 4 is an enlarged cross-sectional view of part A of FIG. 3.

[0135] As illustrated in FIGS. 3 and 4, an all-solid-state secondary battery according to one embodiment is a secondary battery capable of being charged and discharged, and includes a plurality of all-solid-state cells (100), a second elastic member (200), an outer body (300), and a third elastic member (400).

[0136] A single all-solid-state cell (100) may include a plurality of unit cells (110), a plurality of first elastic members (120), and a pouch member (130). The unit cells (110) and the first elastic members (120) may be alternately stacked. Here, the unit cell (110) may include a positive electrode (111), a solid electrolyte layer (112), and a negative electrode (113). Here, the positive electrode (111) may include a cathode, and the negative electrode (113) may include an anode.

[0137] In the embodiment illustrated in FIG. 3, a structure in which four unit cells (110) and five first elastic members (120) are laminated is illustrated, but it is not necessarily limited thereto, and a variety of unit cells may be laminated.

[0138] The positive electrode (111) may include a positive electrode current collecting layer (111a) and a positive electrode active material layer (111b) positioned on both sides of the positive electrode current collecting layer (111a).

[0139] The positive electrode current collecting layer (111a) may have a plate shape or a foil shape. The positive electrode current collecting layer (111a) may include any one selected from aluminum (Al), indium (In), copper (Cu), magnesium (Mg), stainless steel (SUS), titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), germanium (Ge), and lithium (Li).

[0140] The positive electrode active material layer (111b) may be formed by coating on both sides of the positive electrode current collecting layer (111a). However, it is not necessarily limited thereto and may be formed using various methods such as transfer. The positive electrode active material layer (111b) may include any one selected from lithium salts such as lithium nickel cobalt manganese oxide (NCM), lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium manganate, and lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfur, iron oxide, or vanadium oxide.

[0141] The cathode (113) may include a cathode current collecting layer (113a) and a cathode coating layer (113b) positioned on one surface of the cathode current collecting layer (113a). The cathode coating layer (113b) may be positioned between the cathode current collecting layer (113a) and the solid electrolyte layer (112).

[0142] The negative electrode current collecting layer (113a) may have a plate shape or a foil shape. The negative electrode current collecting layer (113a) may include various known metals and compounds that do not react with lithium. The negative electrode current collecting layer (113a) may include any one selected from stainless steel (SUS), copper (Cu), titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni).

[0143] The cathode coating layer (113b) may include, but is not limited to, silver (Ag) and carbon (C). For example, the cathode coating layer (113b) may have a structure in which particles formed of a metal or semiconductor including at least one of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn) are contained in a carbon layer including at least one of carbon black (CB), furnace black (FB), acetylene black (AB), ketjen black (KB), and graphene. When charging an all-solid-state secondary battery, lithium is precipitated between the negative electrode current collecting layer (113a) and the negative electrode coating layer (113b), so that a lithium metal layer is formed between the negative electrode current collecting layer (113a) and the negative electrode coating layer (113b). After discharging the all-solid-state secondary battery, the lithium precipitated between the negative electrode current collecting layer (113a) and the negative electrode coating layer (113b) is removed, so that the negative electrode current collecting layer (113a) and the negative electrode coating layer (113b) can come into direct contact. In this way, the thickness of the negative electrode (113) may change when charging and discharging the all-solid-state secondary battery, and this change in the thickness of the negative electrode (113) may change the pressure applied to the solid electrolyte layer (112), thereby causing stress to be generated in the solid electrolyte layer (112).

[0144] The solid electrolyte layer (112) may be positioned between the positive electrode (111) and the negative electrode (113). That is, the solid electrolyte layer (112) may be positioned between the positive electrode active material layer (111b) and the negative electrode coating layer (113b).

[0145] The solid electrolyte layer (112) may include, but is not limited to, various known sulfide-based solid electrolyte materials. For example, the solid electrolyte layer (112) may be Li2S-P2S5, Li2S-P2S5-LiX (X is a halogen element, for example, I, Cl), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (m, n are positive numbers, Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-LipMOq (p, q are positive numbers, M is P, Si, Ge, It may include one of B, Al, Ga, and In. The solid electrolyte layer (112) may include at least one of an amorphous and a crystalline layer.

[0146] In this embodiment, the unit cell (110) is described based on a unit cell having a bi-cell structure in which a positive electrode active material layer (111b), a solid electrolyte layer (112), and a negative electrode (113) are sequentially laminated on both sides of the positive electrode current collecting layer (111a), but is not necessarily limited thereto, and a unit cell (110) having a mono-cell structure in which a positive electrode active material layer (111b), a solid electrolyte layer (112), and a negative electrode (113) are sequentially laminated on one side of the positive electrode current collecting layer (111a) is also possible. Here, the upper and lower positional relationship is set based on the Z direction.

[0147] The first elastic member (120) may be made of an elastic material such as rubber, elastomer, or foam. The foam may include a urethane foam having a closed cell structure.

[0148] The pouch member (130) can accommodate a plurality of unit cells (110) and a plurality of first elastic members (120) therein. The pouch member (130) can seal the plurality of unit cells (110) and the plurality of first elastic members (120) by accommodating them therein and blocking outside air from entering the plurality of unit cells (110). The pouch member (130) is formed by hermetically bonding the edges of a pair of pouch sheets, each of which has an insulating resin containing a thermosetting polymer applied to its inner surface, so as to accommodate a plurality of unit cells (110) and a plurality of first elastic members (120).

[0149] The second elastic member (200) can be positioned between adjacent all-solid cells (100).

[0150] The second elastic member (200) may be made of an elastic material such as rubber, elastomer, or foam. The foam may include a urethane foam having a closed cell structure.

[0151] The outer body (300) can accommodate a plurality of all-solid-state cells (100), a second elastic member (200), and a third elastic member (400) therein. The outer body (300) can be made of a laminate film or a rigid material. The outer body (300) can include a first outer body (310) positioned at the uppermost portion of the plurality of all-solid-state cells (100) that are stacked, and a second outer body (320) positioned at the lowermost portion of the plurality of all-solid-state cells (100) that are stacked.

[0152] The third elastic member (400) may be positioned between the outermost all-solid-state cell (110t) among the plurality of all-solid-state cells (100) and the outer body (300). The third elastic member (400) may include a third upper elastic member (410) positioned between the outermost all-solid-state cell (110t) and the first outer body (310), and a third lower elastic member (420) positioned between the outermost all-solid-state cell (110t) and the second outer body (320).

[0153] The third elastic member (400) may be made of an elastic material such as rubber, elastomer, or foam. The foam may include a urethane foam having a closed cell structure, etc. Since the third elastic member (400) functions as a pressing member that improves the adhesion of the all-solid-state cell (100), a separate pressing device is not required. Accordingly, the overall weight of the all-solid-state secondary battery can be reduced, and the energy density of the all-solid-state secondary battery can be improved.

[0154] Here, the compressive strengths of the first elastic member (120), the second elastic member (200), and the third elastic member (400) may be different from each other. That is, when the compressive strength of the first elastic member (120) is P1, the compressive strength of the second elastic member (200) is P2, and the compressive strength of the third elastic member (400) is P3, the compressive strengths of the elastic members (120, 200, 400) can be expressed by the following mathematical expression 1.

[0155] [Mathematical Formula 1]

[0156] P1 < P2 < P3

[0157] For example, if the compression ratio is 10% of the initial thickness, P1 may be 2 MPa, P2 may be 2.5 MPa, and P3 may be 3 MPa.

[0158] Here, the compressive strength (MPa) is a value from CFD (Compression Force Deflection), and represents the compressive strength when the elastic layer is physically compressed by 10%. The load was obtained after compressing the specimen to 10% of the original thickness at a compression ratio of 0.6 mm / min using a compression tester, and is calculated using the following mathematical equation 2.

[0159] [Equation 2]

[0160] Compressive strength (MPa) = [Load at 10% compression (kgf)] / [Area of ​​test piece (㎠)] × 0.1

[0161] In particular, based on a compression ratio of 10%, P2: P3 may be 1: 1~3. In addition, the second elastic member (200) may have a compression ratio of 5 to 20% when P2 is 2 to 4 MPa, and the third elastic member (400) may have a compression ratio of 5 to 15% when P3 is 2 to 4 MPa. In addition, the static use limit of the elastic member refers to the compressive strength when the elastic member is compressed and stopped or compressed for a long period of time. The static use limit of the second elastic member (200) may be 3 MPa at a compression ratio of 13% or less, and the static use limit of the third elastic member (400) may be 6 MPa at a compression ratio of 13% or less. The dynamic load of the elastic member refers to the compressive strength when the compression ratio of the elastic member continuously changes. The dynamic load of the second elastic member (200) may be 9 MPa at a compression ratio of 16% or less, and the dynamic load of the third elastic member (400) may be 9 MPa at a compression ratio of 16% or less.

[0162] In this way, by differently controlling the compressive strengths of the first elastic member (120), the second elastic member (200), and the third elastic member (400), the pressure applied to the solid electrolyte layer (112) when the all-solid-state cell (100) is pressurized can be made uniform, and the pressure applied to the solid electrolyte layer (112) when the all-solid-state cell (100) is pressurized can be made uniform. Accordingly, the stress applied to the solid electrolyte layer (112) can be minimized, thereby preventing damage to the solid electrolyte layer (112).

[0163] In addition, when the size of the restorability of the first elastic member (120) is R1, the size of the restorability of the second elastic member (200) is R2, and the size of the restorability of the third elastic member (400) is R3, the sizes of the restorability of the elastic members (120, 200, 400) can be expressed by the following mathematical expression 3.

[0164] [Equation 3]

[0165] R1 < R2 < R3

[0166] Here, the resilience (%) can be measured as the ratio of the stress at the initial point after compression to the initial laminated thickness. It is calculated using the following mathematical equation 4.

[0167] [Equation 4]

[0168] Recovery rate (%) = (Stress at 2 MPa point after additional CFD 10% compression after compression to 2 MPa) / (2 MPa) × 100

[0169] In addition, when the thickness of the first elastic member (120) is T1, the thickness of the second elastic member (200) is T2, and the thickness of the third elastic member (400) is T3, the thicknesses of the elastic members (120, 200, 400) can be expressed by the following mathematical expression 5.

[0170] [Equation 5]

[0171] T1 < T2 < T3

[0172] In this way, the all-solid-state secondary battery according to one embodiment includes a first elastic member (120) alternately stacked with unit cells (110), a second elastic member (200) positioned between the all-solid-state cells (100), and a third elastic member (400) positioned between the outermost all-solid-state cells (110t) and the outer body (300), and by differently controlling the compressive strengths of the first elastic member (120), the second elastic member (200), and the third elastic member (400), the pressure applied to the solid electrolyte layer (112) when the all-solid-state cell (100) is pressed can be made uniform. Accordingly, the stress applied to the solid electrolyte layer (112) can be minimized, thereby preventing damage to the solid electrolyte layer (112).

[0173] Therefore, by preventing a short circuit between the positive electrode (111) and the negative electrode (113) located on both sides of the solid electrolyte layer (112), the failure rate of the all-solid-state secondary battery can be reduced and the performance can be improved.

[0174] In addition, by uniformly applying pressure to the solid electrolyte layer (112) when pressurizing the all-solid-state cell (100), the discharge efficiency can be improved.

[0175] Meanwhile, the second elastic member (200) and the third elastic member (400) have an adhesive strength of 30 to 1000 gf / inch based on a 180-degree peel strength (i.e., when the peel speed is 300 mm / min), and thus can have adhesiveness. To this end, the second elastic member (200) and the third elastic member (400) themselves may be made of an adhesive material, or an adhesive material may be transferred to the surfaces of the second elastic member (200) and the third elastic member (400).

[0176] Here, the peel strength is defined as the adhesive strength of the adhesive layer laminated to the elastic sheet, and can be measured by laminating the PET film to the elastic sheet and at a speed of 300 mm / min in the 180 degree direction.

[0177] In addition, when the thermal conductivity of the first elastic member (120) is H1, the thermal conductivity of the second elastic member (200) is H2, and the thermal conductivity of the third elastic member (400) is H3, the thermal conductivity of the elastic members (120, 200, 400) can be expressed by the following mathematical expression 6.

[0178] [Equation 6]

[0179] H1 > H2 > H3

[0180] Here, thermal conductivity (w / mk) is defined as the thermal conductivity of the elastic sheet, and an example of measuring thermal conductivity is as follows.

[0181] The elastic sheet is manufactured into a specimen with a size of 2 cm x 2 cm in length x width, and the thermal conductivity in the horizontal direction is measured using TPS2200 (manufacturer: Hot Disk) according to ISO22007-2, and the thermal conductivity in the vertical direction is measured using TIM-1300 (manufacturer: Analysis Tech) according to ASTM5470.

[0182] Accordingly, since the first elastic member (120) has a thermal conductivity of 0.6 to 4 w / mk at 25°C, the first elastic member (120) can have heat dissipation properties. Accordingly, heat generated inside the all-solid-state cell can be easily released to the outside, thereby preventing damage to the all-solid-state cell due to heat.

[0183] In addition, since the second elastic member (200) and the third elastic member (400) have a thermal conductivity of 0.01 to 0.4 W / mk at 25°C, the second elastic member (200) and the third elastic member (400) can have thermal insulation properties. Accordingly, heat transfer between adjacent all-solid-state cells can be minimized, thereby preventing damage to adjacent all-solid-state cells due to heat generated in some of the all-solid-state cells.

[0184] Here, the heat dissipation and insulation properties of the elastic member (120, 200, 400) can be controlled by controlling the amount of filler injected into the foam material.

[0185] Meanwhile, in the above embodiment, the characteristics of the second elastic member (200) and the third elastic member (400) are different, but a structure in which the characteristics of the second elastic member (200) and the third elastic member (400) are the same is also possible.

[0186] That is, the compressive strength (P2) of the second elastic member (200) and the compressive strength (P3) of the third elastic member (400) may be the same, the magnitude of the restorability (R2) of the second elastic member (200) and the magnitude of the restorability (R3) of the third elastic member (400) may be the same, the thickness (T2) of the second elastic member (200) and the thickness (T3) of the third elastic member (400) may be the same, and the thermal conductivity (H2) of the second elastic member (200) and the thermal conductivity (H3) of the third elastic member (400) may be the same.

[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 plurality of all-solid-state cells in which unit cells including a positive electrode, a solid electrolyte layer, and a negative electrode and a first elastic member are laminated; A second elastic member positioned between adjacent said all-solid cells; An outer body housing the plurality of all-solid-state cells and the second elastic member; and A third elastic member positioned between the outermost all-solid cell located at the outermost end of the above plurality of all-solid cells and the outer body. Including, An all-solid-state secondary battery, wherein the compressive strengths of the first elastic member and the second elastic member are different from each other.

2. In paragraph 1, An all-solid-state secondary battery, wherein the compressive strengths of the first elastic member, the second elastic member, and the third elastic member are different from each other.

3. In paragraph 2, When the compressive strength of the first elastic member is P1, the compressive strength of the second elastic member is P2, and the compressive strength of the third elastic member is P3, An all-solid-state secondary battery where P1 < P2 < P3.

4. In paragraph 3, When the size of the restorability of the first elastic member is R1, the size of the restorability of the second elastic member is R2, and the size of the restorability of the third elastic member is R3, An all-solid-state secondary battery with R1 < R2 < R3.

5. In paragraph 4, When the thickness of the first elastic member is T1, the thickness of the second elastic member is T2, and the thickness of the third elastic member is T3, An all-solid-state secondary battery with T1 < T2 < T3.

6. In paragraph 2, An all-solid-state secondary battery, wherein the second elastic member and the third elastic member have an adhesive strength of 30 to 1000 gf / inch based on a 180-degree peel strength standard (measured at a speed of 300 mm / min).

7. In paragraph 2, The above first elastic member has a thermal conductivity of 0.6 to 4 W / mk at 25°C, An all-solid-state secondary battery, wherein the second elastic member and the third elastic member have thermal conductivity of 0.01 to 0.4 W / mk at 25°C.

8. In paragraph 1, An all-solid-state secondary battery, wherein the compressive strengths of the second elastic member and the third elastic member are the same.

9. In paragraph 1, An all-solid-state secondary battery, wherein the all-solid-state cell further includes a pouch member that accommodates the unit cell and the first elastic member.

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