All-solid-state rechargeable battery

Abstract

One embodiment relates to an all-solid-state rechargeable battery comprising: a positive electrode that comprises a positive electrode current collector, a positive electrode active material layer located on the positive electrode current collector, and a safety functional layer located on the positive electrode active material layer; a negative electrode; and a solid electrolyte layer located between the positive electrode and the negative electrode, wherein the positive electrode active material layer comprises a positive electrode active material and a sulfide-based solid electrolyte, the safety functional layer comprises an olivine-based positive electrode active material, and the solid electrolyte layer comprises the sulfide-based solid electrolyte.

Description

All-solid-state secondary battery

[0001] It is about all-solid-state secondary batteries.

[0002] Lithium secondary batteries, which boast high energy density and portability, are primarily used as power sources for mobile information terminals such as mobile phones, laptops, and smartphones. Recently, active research is underway to utilize high-energy-density lithium secondary batteries as power sources for hybrid and electric vehicles, or as power storage devices.

[0003] Commercially available lithium secondary batteries use electrolytes containing flammable organic solvents, posing safety concerns that can lead to explosions or fires in the event of collisions, penetrations, or other problems. Therefore, semi-solid or all-solid-state batteries, which avoid the use of electrolytes, are being proposed. All-solid-state batteries are comprised entirely of solid materials, specifically those that utilize solid electrolytes. These all-solid-state batteries are safe, eliminating the risk of electrolyte leakage and explosion, and offer the advantage of being easy to manufacture in thin forms.

[0004] An all-solid-state secondary battery is provided that can effectively improve the safety of a battery by reducing the heat generation of the battery and preventing thermal runaway.

[0005] In one embodiment, an all-solid-state secondary battery is provided, comprising: a positive electrode including a positive electrode current collector, a positive electrode active material layer positioned on the positive electrode current collector, and a safety functional layer positioned on the positive electrode active material layer; a negative electrode; and a solid electrolyte layer positioned between the positive electrode and the negative electrode, wherein the positive electrode active material layer includes a positive electrode active material and a sulfide-based solid electrolyte, the safety functional layer includes an olivine-based positive electrode active material, and the solid electrolyte layer includes the sulfide-based solid electrolyte.

[0006] An all-solid-state secondary battery according to an embodiment can effectively improve the safety of the battery by reducing the heat generation of the battery and preventing thermal runaway.

[0007] Figures 1 and 2 are cross-sectional views schematically showing an all-solid-state secondary battery according to one embodiment.

[0008] Below, specific implementation examples are described in detail so that those skilled in the art can easily implement the present invention. However, the present invention can be implemented in various different forms and is not limited to the implementation examples described herein.

[0009] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0010] “Combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0011] It should be understood that terms such as "include," "comprise," or "have" are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0012] 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.

[0013] “Layer” includes not only shapes formed on the entire surface when observed in a plan view, but also shapes formed on some surfaces.

[0014] The average particle size can be measured by methods well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with transmission electron microscope images or scanning electron microscope images. Alternatively, the average particle size can be obtained by measuring using dynamic light scattering, performing data analysis, counting the number of particles for each particle size range, and calculating from the counted number. Unless otherwise defined, the average particle size is the diameter (D) of the particles in the particle size distribution that have a cumulative volume of 50% by volume. 50 ) can mean. In addition, unless otherwise defined, the average particle size is obtained by measuring the size (diameter or length of major axis) of about 20 particles randomly in a scanning electron microscope image to obtain a particle size distribution, and the diameter (D) of the particle having a cumulative volume of 50% by volume in the particle size distribution 50 ) may be taken as the average particle diameter.

[0015] “Or” is not interpreted as exclusive, for example, “A or B” is interpreted as including A, B, A+B, etc.

[0016] “Metal” is interpreted as a concept that includes common metals, transition metals, and metalloids (semi-metals).

[0017] In one embodiment, an all-solid-state secondary battery is provided, comprising a positive electrode, a negative electrode, and a solid electrolyte layer positioned between the positive electrode and the negative electrode.

[0018] FIG. 1 is a cross-sectional view of an all-solid-state secondary battery according to an embodiment. Referring to FIG. 1, the all-solid-state secondary battery (100) may have a structure in which an electrode assembly is housed in a battery case, in which a cathode (200) including a cathode current collector (401) and a cathode active material layer (403), a solid electrolyte layer (300), and a cathode current collector (201); a cathode active material layer (203) positioned on the cathode current collector; and a safety functional layer (205) positioned on the cathode active material layer are laminated. The all-solid-state secondary battery (100) may further include an elastic layer (500) on the outer side of at least one of the cathode (200) and the cathode (400). Although one electrode assembly including a cathode (400), a solid electrolyte layer (300), and anode (200) is illustrated in FIG. 1, two or more electrode assemblies may be stacked, and an all-solid-state secondary battery may be manufactured by stacking 2 to 200, 3 to 100, 4 to 50, or other electrode assemblies.

[0019] anode

[0020] In one embodiment, an all-solid-state secondary battery (100) is provided, which includes a positive electrode (200) including a positive electrode current collector (201), a positive electrode active material layer (203) positioned on the positive electrode current collector, and a safety functional layer (205) positioned on the positive electrode active material layer.

[0021] The above-mentioned positive electrode active material layer includes a positive electrode active material and a sulfide-based solid electrolyte, the above-mentioned safety functional layer includes an olivine-based positive electrode active material, and the above-mentioned solid electrolyte layer includes a sulfide-based solid electrolyte. The above-mentioned safety functional layer may further include a sulfide-based solid electrolyte.

[0022] The sulfide-based solid electrolyte of the positive electrode active material layer and the sulfide-based solid electrolyte of the solid electrolyte layer may be the same or different. In addition, when the safety functional layer further includes the sulfide-based solid electrolyte, the sulfide-based solid electrolyte of the positive electrode active material layer, the sulfide-based solid electrolyte of the safety functional layer, and the sulfide-based solid electrolyte of the solid electrolyte layer may be the same or different.

[0023] Safety functional layer

[0024] The above safety functional layer (205) includes an olivine-based positive electrode active material.

[0025] Olivine-based cathode active materials are cathode active materials with a hexahedral shape. Compared to cathode active materials with a layered structure, they have superior lattice structure stability, less crystal structure deterioration even when lithium ions escape during discharge, and excellent thermal stability.

[0026] An all-solid-state battery according to one embodiment includes a safety functional layer including the olivine-based positive electrode active material, thereby reducing the amount of heat generated by the battery when a short circuit occurs between the positive electrode and the negative electrode due to an internal short circuit or damage (penetration, collision, etc.) caused by an external force, and preventing direct contact between the positive electrode active material layer and the negative electrode, thereby preventing thermal runaway due to collapse of the active material.

[0027] The above olivine-based positive electrode active material may be a lithium transition metal phosphate, and may include, for example, lithium iron phosphate, lithium manganese iron phosphate, lithium manganese phosphate, lithium titanium phosphate, or a combination thereof.

[0028] The above olivine-based positive electrode active material can be specifically represented by Chemical Formula 1, Chemical Formula 2, Chemical Formula 3, Chemical Formula 4, or Chemical Formula 5.

[0029] [Chemical Formula 1]

[0030] Li a1 Fe (1-x1) M 1 x1PO4

[0031] In chemical formula 1, 0.90≤a1≤1.5, 0≤x1≤0.4, and M 1 is Al, Ca, Ce, Cr, Cu, Co, La, Mg, Mo, Nb, Ni, Sn, Sr, V, W, Y, Zn, Zr, or a combination thereof.

[0032] A compound represented by chemical formula 1 may be referred to as lithium iron phosphate. In chemical formula 1, for example, 0.90≤a1≤1.2, or 0.95≤a1≤1.1, and 0≤x1≤0.3, 0≤x1≤0.2, 0≤x1≤0.1, or 0 <x1≤0.05일 수 있다. 예를 들어 a1=1 및 x1=0일 경우 화학식 1은 LiFePO4로 표현될 수 있다.

[0033] [Chemical Formula 2]

[0034] Li a2 Mn x2 Fe (1-x2-y2) M 2 y2 PO4

[0035] In chemical formula 2, 0.90≤a2≤1.5, 0.1≤x2≤0.9, M 2 is Al, Ca, Ce, Cr, Cu, Co, La, Mg, Mo, Nb, Ni, Sn, Sr, V, W, Y, Zn, Zr, or a combination thereof.

[0036] The compound represented by chemical formula 2 may be referred to as lithium manganese iron phosphate. In chemical formula 2, for example, 0.90≤a2≤1.2, or 0.95≤a2≤1.1, and 0.2≤x2≤0.8, 0.3≤x2≤0.7, or 0.4≤x2≤0.6. The compound represented by chemical formula 2 may be, for example, LiMn 0.9 Fe 0.1 PO4, LiMn 0.8 Fe 0.2 PO4, LiMn 0.7 Fe 0.3 PO4, LiMn 0.6 Fe 0.4 PO4, LiMn0.5 Fe 0.5 PO4, LiMn 0.4 Fe 0.6 PO4, LiMn 0.3 Fe 0.7 PO4, LiMn 0.2 Fe 0.8 PO4, or LiMn 0.1 Fe 0.9 It could be PO4, etc.

[0037] [Chemical Formula 3]

[0038] Li a3 Mn (1-x3) M 3 x3 PO4

[0039] In chemical formula 3, 0.90≤a3≤1.5, 0≤x3≤0.4, and M 3 is Al, Ca, Ce, Cr, Cu, Co, La, Mg, Mo, Nb, Ni, Sn, Sr, V, W, Y, Zn, Zr, or a combination thereof.

[0040] The compound represented by chemical formula 3 may be referred to as lithium manganese phosphate. In chemical formula 3, for example, 0.90≤a3≤1.2, or 0.95≤a3≤1.1, and 0≤x3≤0.3, 0≤x3≤0.2, 0≤x3≤0.1, or 0 <x3≤0.05일 수 있다. 예를 들어 a3=1 및 x3=0일 경우 화학식 3는 LiMnPO4로 표현될 수 있다.

[0041] [Chemical Formula 4]

[0042] Li a4 Ti (2-x4) M 4 x4 (PO4)3

[0043] In chemical formula 4, 0.90≤a4≤1.5, 0≤x4≤0.4, and M 4 is Al, Ca, Ce, Cr, Cu, Co, La, Mg, Mo, Nb, Ni, Sn, Sr, V, W, Y, Zn, Zr, or a combination thereof.

[0044] The compound represented by chemical formula 4 may be referred to as lithium titanium phosphate. In chemical formula 4, for example, 0.90≤a4≤1.2, or 0.95≤a4≤1.1, and 0≤x4≤0.3, 0≤x4≤0.2, 0≤x4≤0.1, or 0 <x4≤0.05일 수 있다. 예를 들어 a4=1 및 x4=0일 경우 화학식 4은 LiTi2(PO4)3로 표현될 수 있다.

[0045] [Chemical Formula 5]

[0046] Li a5 Ti (1-x5) M 5 x5 PO5

[0047] In chemical formula 5, 0.90≤a5≤1.5, 0≤x5≤0.4, and M 5 is Al, Ca, Ce, Cr, Cu, Co, La, Mg, Mo, Nb, Ni, Sn, Sr, V, W, Y, Zn, Zr, or a combination thereof.

[0048] The compound represented by chemical formula 5 may be referred to as lithium titanium phosphate. In chemical formula 5, for example, 0.90≤a5≤1.2, or 0.95≤a5≤1.1, and 0≤x5≤0.3, 0≤x5≤0.2, 0≤x5≤0.1, or 0 <x5≤0.05일 수 있다. 예를 들어 a5=1 및 x5=0일 경우 화학식 5은 LiTiPO5로 표현될 수 있다.

[0049] As a specific example, the above olivine-based positive electrode active material is LiFePO4, LiMn 0.7 Fe 0.3 PO4, LiMn 0.6 Fe 0.4 PO4, LiMn 0.5 Fe 0.5 PO4, LiMn 0.4 Fe 0.6 PO4, LiMn 0.3 Fe 0.7 It may include PO4, LiMnPO4, LiTiPO5, LiTi2(PO4)3, or a combination thereof.

[0050] The above olivine-based positive electrode active material may be a type of primary particle, and its average particle diameter (D 50 ) may be, for example, 10 nm to 2 μm, for example, 50 nm to 1.5 μm, 100 nm to 1.0 μm, 100 nm to 900 nm, or 100 nm to 600 nm. When the average particle diameter of the olivine-based positive electrode active material satisfies the above range, the safety of the battery can be maximized.

[0051] Here, the average particle size is obtained by randomly measuring the size (diameter or length of major axis) of about 20 particles in scanning electron microscope images of positive electrode active materials to obtain a particle size distribution, and the diameter (D) of the particles having a cumulative volume of 50% by volume in the particle size distribution 50 ) may be taken as the average particle diameter.

[0052] The above olivine-based positive electrode active material may be included in an amount of 70 wt% to 99.9 wt% based on 100 wt% of the safety functional layer, for example, 70 wt% to 95 wt%, or 75 wt% to 95 wt%. When the above range is satisfied, an all-solid-state secondary battery having excellent effects of reducing heat generation and preventing thermal runaway of the battery can be realized.

[0053] The above safety functional layer (205) may further include a sulfide-based solid electrolyte. A detailed description of the sulfide-based solid electrolyte will be described later in the section on the solid electrolyte layer (300).

[0054] The sulfide-based solid electrolyte of the above safety functional layer has an average particle diameter (D 50 ) may be small particles of 0.1㎛ to 1.9㎛.

[0055] The above sulfide-based solid electrolyte may be included in an amount of 1 wt% to 30 wt%, 3 wt% to 30 wt%, 5 wt% to 30 wt%, or 5 wt% to 25 wt%, based on 100 wt% of the safety functional layer (205). When included in the above content range, the ion conductivity of the safety functional layer can be secured while effectively implementing the safety of the battery.

[0056] The weight ratio of the olivine-based positive electrode active material and the sulfide-based solid electrolyte included in the safety functional layer may be 70:30 to 97:3, for example, 75:25 to 97:3, or 75:25 to 95:5. When the above weight ratio is satisfied, the safety of the battery can be effectively implemented while securing the ion conductivity of the safety functional layer.

[0057] The safety functional layer (205) may optionally further include a binder and / or a conductive material. The binder may be further included in the safety functional layer (205) to facilitate adhesion of the olivine-based positive electrode active material particles to each other and to facilitate adhesion of the olivine-based positive electrode active material to the positive electrode active material layer. The conductive material may impart conductivity to the safety functional layer (205).

[0058] A specific description of the above binder and the above conductive material will be described later in the section on the positive electrode active material layer (203).

[0059] The content of the binder in the safety functional layer (205) may be comprised in an amount of 0.1 wt% to 25 wt% based on 100 wt% of the safety functional layer, for example, 0.1 wt% to 20 wt%, or 0.5 wt% to 15 wt%. When the above range is satisfied, the safety of the battery can be secured while improving the adhesive strength between the olivine-based positive electrode active material particles in the safety functional layer.

[0060] The content of the conductive material in the safety functional layer (205) may be comprised in a range of 0 wt% to 20 wt% with respect to 100 wt% of the safety functional layer, for example, 1 wt% to 15 wt%, or 2 wt% to 15 wt%. When the above range is satisfied, conductivity can be imparted to the safety functional layer while ensuring the safety of the battery.

[0061] The thickness of the safety functional layer (205) may be 1 µm to 15 µm, for example, 1 µm to 10 µm, 5 µm to 10 µm, or 5 µm to 8 µm. When the above thickness range is satisfied, an all-solid-state secondary battery with excellent safety can be realized.

[0062] positive electrode active material layer

[0063] The above positive electrode active material layer includes a positive electrode active material and a sulfide-based solid electrolyte, and may optionally include a binder and / or a conductive material.

[0064] The above-mentioned positive electrode active material may 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, may include a lithium transition metal composite oxide, and may include a compound represented by any one of the following chemical formulas.

[0065] Li a A 1-b X b D2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5);

[0066] 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);

[0067] Li a E 1-b X b O 2-c Dc (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0068] 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);

[0069] 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);

[0070] 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);

[0071] 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);

[0072] 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);

[0073] 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);

[0074] 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);

[0075] 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);

[0076] 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);

[0077] Li a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0078] Li a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0079] Li a Mr 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0080] Li a Mn2G b O4(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0081] Li a Mr 1-g G g PO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5);

[0082] QO2; QS2; LiQS2;

[0083] V2O5; LiV2O5;

[0084] LiZO2;

[0085] LiNiVO4;

[0086] Li (3-f) J2(PO4)3(0 ≤ f ≤ 2);

[0087] Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2);

[0088] Li a FePO4(0.90 ≤ a ≤ 1.8).

[0089] 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.

[0090] 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).

[0091] The positive electrode active material may include, for example, a lithium nickel-based oxide represented by the following chemical formula 6, a lithium cobalt-based oxide represented by the following chemical formula 7, a lithium iron phosphate-based compound represented by the following chemical formula 8, a cobalt-free lithium nickel-manganese-based oxide represented by the following chemical formula 9, or a combination thereof, and as a specific example, it may include a lithium nickel-based oxide represented by the following chemical formula 6 or a lithium cobalt-based oxide represented by the following chemical formula 7.

[0092] [Chemical Formula 6]

[0093] Li a6 Ni x6 M 6 y6 M 7 z6 O 2-b6 X b6

[0094] In the above chemical formula 6, 0.9≤a6≤1.8, 0.3≤x6≤1, 0≤y6≤0.7, 0≤z6≤0.7, 0.9≤x6+y6+z6≤1.1, and 0≤b6≤0.1, and M 6 and M 7 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0095] In the above chemical formula 6, 0.6≤x6≤1, 0≤y6≤0.4, and 0≤z6≤0.4, or 0.8≤x6≤1, 0≤y6≤0.2, and 0≤z6≤0.2.

[0096] [Chemical Formula 7]

[0097] Li a7 Co x7 M 8 y7 O 2-b7 X b7

[0098] In the above chemical formula 7, 0.9≤a7≤1.8, 0.7≤x7≤1, 0≤y7≤0.3, 0.9≤x7+y7≤1.1, and 0≤b7≤0.1, and M 8 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P and S.

[0099] [Chemical Formula 8]

[0100] Li a8 Fe x8 M 9 y8 PO 4-b8 X b8

[0101] In the above chemical formula 8, 0.9≤a8≤1.8, 0.6≤x8≤1, 0≤y8≤0.4, and 0≤b8≤0.1, and M 9 is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is one or more elements selected from the group consisting of F, P and S.

[0102] [Chemical Formula 9]

[0103] Li a9 Ni x9 Mn y9 M 10 z9 O 2-b9 X b9

[0104] In the above chemical formula 9, 0.9≤a9≤1.8, 0.8≤x9<1, 0 <y9≤0.2, 0≤z9≤0.2, 0.9≤x9+y9+z9≤1.1, 및 0≤b9≤0.1이고 M 10is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0105] 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, 1 μm to 20 μm, 1 μm to 18 μm, 3 μm to 15 μm, or 5 μm to 15 μm. For example, the positive electrode active material may include small particles having an average particle diameter (D50) of 1 μm to 9 μm and large particles having an average particle diameter (D50) of 10 μm to 25 μm. A positive electrode active material having such a particle diameter range can be harmoniously mixed with other components within a positive electrode active material layer and can realize high capacity and high energy density. Here, the average particle diameter may be obtained by selecting 20 or so random particles from a scanning electron microscope image of the positive electrode active material, measuring their particle diameters (diameter, major axis, or major axis length), obtaining a particle size distribution, and then taking the diameter (D50) of particles having a cumulative volume of 50% by volume from the particle size distribution as the average particle diameter.

[0106] 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.

[0107] Meanwhile, the positive electrode active material may include a buffer layer on the particle surface. The buffer layer may be expressed as a coating layer, a protective layer, etc., and may play a role in lowering the interfacial resistance between the positive electrode active material and the sulfide-based solid electrolyte particles. For example, the buffer layer may include a lithium-metal-oxide, wherein the metal may be one or more elements selected from the group consisting of Al, B, Ca, Ce, Cr, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ta, V, W, and Zr. The lithium-metal-oxide is excellent in lowering the interfacial resistance between the positive electrode active material and the solid electrolyte particles while improving the performance of the positive electrode active material by facilitating the movement of lithium ions and electron conduction.

[0108] The positive electrode active material may be included in an amount of 55 wt% to 99 wt% based on 100 wt% of the positive electrode active material layer, for example, 65 wt% to 95 wt%, or 75 wt% to 91 wt%.

[0109] The positive electrode active material layer (203) includes a sulfide-based solid electrolyte, and a detailed description thereof will be described later in the section on the solid electrolyte layer (300).

[0110] The sulfide-based solid electrolyte of the above positive electrode active material layer has an average particle diameter (D 50 ) may be small particles of 0.1㎛ to 1.9㎛.

[0111] With respect to 100 wt% of the above positive electrode active material layer, the sulfide-based solid electrolyte may be included in an amount of 0.1 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%.

[0112] In addition, in the positive electrode active material layer, the positive electrode active material may be included in an amount of 65 wt% to 99 wt% and the sulfide-based solid electrolyte in an amount of 1 wt% to 35 wt%, based on the total weight of the positive electrode active material and the sulfide-based solid electrolyte, for example, the positive electrode active material may be included in an amount of 80 wt% to 90 wt% and the sulfide-based solid electrolyte in an amount of 10 wt% to 20 wt%. When the sulfide-based solid electrolyte is included in the positive electrode in such an amount, the efficiency and life characteristics of the all-solid-state battery can be improved without reducing the capacity.

[0113] The above binder is included in the positive electrode active material layer (203), thereby serving to attach positive electrode active material particles well to each other and also to attach the positive electrode active material well to the current collector.

[0114] The binder may include, but is not limited to, a polymer including polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, or a combination thereof.

[0115] The content of the binder in the positive electrode active material layer (203) may be approximately 0.1 wt% to 5 wt% with respect to 100 wt% of the positive electrode active material layer.

[0116] The above-described positive electrode active material layer (203) may further include a conductive material. The conductive material is used to provide conductivity to the electrode, and any material that does not cause a chemical change and is electronically conductive in the battery to be formed may be used. Examples of conductive materials that may be used include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or conductive materials including mixtures thereof.

[0117] The content of the conductive material in the positive electrode active material layer may be 0 wt% to 3 wt%, 0.01 wt% to 2 wt%, or 0.1 wt% to 1 wt% with respect to 100 wt% of the positive electrode active material layer.

[0118] Aluminum foil may be used as the above-mentioned positive electrode collector (201), but is not limited thereto.

[0119] solid electrolyte layer

[0120] The solid electrolyte layer (300) includes a solid electrolyte, and the solid electrolyte includes a sulfide-based solid electrolyte.

[0121] 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 pMO q (p, q are integers, and M is P, Si, Ge, B, Al, Ga or In), or a combination thereof.

[0122] A sulfide-based solid electrolyte 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. The ionic conductivity can be further improved by further including other components such as SiS2, GeS2, and B2S3.

[0123] Methods for mixing sulfur-containing raw materials for producing sulfide-based solid electrolytes include mechanical milling or the solution method. Mechanical milling involves placing raw materials in a ball mill reactor and vigorously stirring them to finely atomize and mix them. Using the solution method, the 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.

[0124] According to one embodiment, sulfide-based solid electrolyte particles can be manufactured through, for example, a first heat treatment in which sulfur-containing raw materials are mixed and calcined at 120°C to 350°C, and a second heat treatment in which the first heat treatment result is mixed and calcined at 350°C to 800°C. The first heat treatment and the second heat treatment can each be performed in an inert gas or nitrogen atmosphere. The first heat treatment can be performed for 1 to 10 hours, and the second heat treatment can be performed for 5 to 20 hours. The first heat treatment can have the effect of milling small raw materials, and the second heat treatment can synthesize the final solid electrolyte. Through two or more such heat treatments, a high-performance sulfide-based solid electrolyte with high ionic conductivity and robustness can be obtained, and such a solid electrolyte can be said to be suitable for mass production. The temperature of the first heat treatment may be, for example, 150°C to 330°C, or 200°C to 300°C, and the temperature of the second heat treatment may be, for example, 380°C to 700°C, or 400°C to 600°C.

[0125] For example, the sulfide-based solid electrolyte particles may include argyrodite-type sulfides. The argyrodite-type sulfide-based solid electrolyte has 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 secondary battery including the same can have improved battery performance, such as rate characteristics, Coulombic efficiency, and cycle life characteristics.

[0126] The argyrodite-type sulfide-based solid electrolyte may include, for example, a compound represented by the chemical formula 10 below.

[0127] [Chemical Formula 10]

[0128] (Li a M 11 b M 12 c )(P d M 13 e )(S f M 14 g )X h

[0129] In the above chemical formula 10, 4≤a≤8, and M 11 is Mg, Cu, Ag, or a combination thereof, and 0≤b<0.5, and M 12 is Na, K, or a combination thereof, 0≤c<0.5, and M 13 is Sn, Zn, Si, Sb, Ge, or a combination thereof, and 0 <d<4, 0≤e<1 이고, M 14 is O, SO n , or a combination thereof, and 1.5≤n≤5, 3≤f≤12, 0≤g<2, and X is F, Cl, Br, I, or a combination thereof, and 0≤h≤2.

[0130] For example, in chemical formula 10, a halide element (X) may be included as an essential element, in which case 0 <h≤2로 표시될 수 있다. 일 예로 화학식 10에 M 11 Elements may be required, in which case 0 <b<0.5로 표시될 수 있다. 화학식 10에서 M 13 can be understood as an element substituted in place of P and 0 <e<1일 수 있다. 화학식 10에서 M 14 is substituted in the S position, for example, 0 <g<2일 수 있으며 S의 비율인 f는 예를 들어 3≤f≤7일 수 있다. M 14 Go SO n If SO n It can be, for example, S4O6, S3O6, S2O3, S2O4, S2O5, S2O6, S2O7, S2O8, SO4, or SO5, and can be, for example, SO4.

[0131] For example, in chemical formula 10, a+b+c+h=7, d+e=1, and f+g+h=6.

[0132] As a specific example, argyrodite-type sulfide-based solid electrolytes include Li3PS4 and Li7P3S. 11 , Li7PS6, Li6PS5Cl, Li6PS5Br, Li 5.8 PS 4.8 Cl 1.2 , Li 6.2 PS 5.2 Br 0.8 , Li 5.75 PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )PS 4.75 Cl 1.25 , (Li 5.72 Cu 0.03 )PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )P(S 4.70 (SO4) 0.05 )Cl 1.25 , (Li 5.69 Cu 0.06 )P(S 4.60 (SO4) 0.15 )Cl 1.25 , (Li 5.72 Cu 0.03 )P(S 4.725 (SO4) 0.025 )Cl 1.25 , (Li 5.72 Na 0.03 )P(S 4.725 (SO4) 0.025 )Cl 1.25 , Li 5.75 P(S 4.725 (SO4) 0.025 )Cl 1.25 , or combinations thereof, but are not limited thereto.

[0133] An argyrodite-type sulfide-based solid electrolyte can be manufactured by mixing raw materials such as lithium sulfide, phosphorus sulfide, and optionally lithium halide. After mixing these, a heat treatment may be performed. The heat treatment may be performed at a temperature in the range of 400°C to 600°C, for example, 450°C to 500°C, or 460°C to 490°C, and for 5 to 30 hours, 10 to 24 hours, or 15 to 20 hours. When heat treating under the above conditions, ionic conductivity can be maximized. The heat treatment may include, for example, two or more heat treatment steps. Here, manufacturing an argyrodite-type sulfide-based solid electrolyte may include, for example, a first heat treatment of mixing raw materials and calcining at 120°C to 350°C, and a second heat treatment of mixing the first heat treatment resultant again and calcining at 350°C to 800°C.

[0134] Average particle diameter (D) of sulfide-based solid electrolyte particles 50 ) may be, for example, 0.1 ㎛ to 5.0 ㎛ or 0.1 ㎛ to 3.0 ㎛, may be small particles of 0.1 ㎛ to 1.9 ㎛, or may be large particles of 2.0 ㎛ to 5.0 ㎛. The sulfide-based solid electrolyte particles may be a mixture of small particles having an average particle size of 0.1 ㎛ to 1.9 ㎛ and large particles having an average particle size of 2.0 ㎛ to 5.0 ㎛.

[0135] The average particle size of sulfide-based solid electrolyte particles can be measured from electron microscope images, for example, by measuring the size (diameter or major axis length) of about 20 particles in a scanning electron microscope image to obtain a particle size distribution, where D 50 It may have been calculated.

[0136] The sulfide-based solid electrolyte may be included in an amount of 90 wt% to 99 wt% based on 100 wt% of the solid electrolyte layer, for example, 95 wt% to 99 wt%.

[0137] The above solid electrolyte layer may further include an oxide-based solid electrolyte, a halide-based solid electrolyte, or a combination thereof.

[0138] Oxide-based solid electrolytes include, 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 mixtures thereof.

[0139] The solid electrolyte layer may further include, for example, a halide-based solid electrolyte. The halide-based solid electrolyte contains a halogen element as a main component, and may mean that the ratio of the halide element to all elements constituting the solid electrolyte is 50 mol% or more, 70 mol% or more, 90 mol% or more, or 100 mol%. For example, the halide-based solid electrolyte may not contain a sulfur element.

[0140] The halide-based solid electrolyte may contain lithium element, a metal element other than lithium, and a halogen element. The metal element other than lithium may be Al, As, B, Bi, Ca, Cd, Co, Cr, Fe, Ga, Hf, In, Mg, Mn, Ni, Sb, Sc, Sn, Ta, Ti, Y, Zn, Zr, or a combination thereof. The halogen element may be F, Cl, Br, I, or a combination thereof, and may be Cl, Br, or a combination thereof. The halide-based solid electrolyte may contain, for example, Li a M1X6 (M is Al, As, B, Bi, Ca, Cd, Co, Cr, Fe, Ga, Hf, In, Mg, Mn, Ni, Sb, Sc, Sn, Ta, Ti, Y, Zn, Zr, or a combination thereof, X is F, Cl, Br, I, or a combination thereof, and 2≤a≤3) can be represented. The halide-based solid electrolyte may be, for example, Li2ZrCl6, Li 2.7 Y 0.7 Zr 0.3 Cl6, Li 2.5 Y 0.5 Zr 0.5 Cl6, Li 2.5 In 0.5 Zr 0.5 Cl6, Li2In 0.5 Zr 0.5 Cl6, Li3YBr6, Li3YCl6, Li3YBr2Cl4, Li3YbCl6, Li 2.6 Hf 0.4 Yb 0.6Cl6, or combinations thereof, but is not limited thereto.

[0141] The solid electrolyte layer may further include a binder. Binders include, for example, nitrile-butadiene rubber, hydrogenated nitrile-butadiene rubber, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluoroelastomer, natural rubber, polydimethylsiloxane, polyethylene oxide, polyvinylpyrrolidone, polyvinylpyridine, chlorosulfonated polyethylene, polyvinyl alcohol, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, polyamideimide, polyimide, poly(meth)acrylate, polyacrylonitrile, polystyrene, polyurethane, and the like. copolymers, or combinations thereof.

[0142] The binder may be included in an amount of 0.1 wt% to 3 wt% based on 100 wt% of the solid electrolyte layer, for example, 0.5 wt% to 2 wt%, or 0.5 wt% to 1.5 wt%. When the binder is included in the above range, the components within the solid electrolyte layer can be well combined without lowering the ionic conductivity of the solid electrolyte, thereby improving the durability and reliability of the battery.

[0143] The solid electrolyte layer may optionally further comprise an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0144] 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.

[0145] The lithium salt may be applied without limitation on type, and may include, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiSCN, LiN(CN)2, lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, or a combination thereof.

[0146] For example, the lithium salt may be an imide-based lithium salt such as LiTFSI, LiFSI, LiBETI, or a combination thereof. The imide-based lithium salt can maintain or improve ionic conductivity by appropriately maintaining chemical reactivity with the ionic liquid.

[0147] 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.

[0148] The ionic liquid comprises a) one or more cations selected from ammonium, pyrrolidinium, pyridinium, pyrimidinium, imidazolium, piperidinium, pyrazolium, oxazolium, pyridazinium, phosphonium, sulfonium, trizolium, and mixtures thereof, and b) BF4. - , PF6 - , AsF6 - , SbF6 - , AlCl4 - , HSO4 - , ClO4 - , CH3SO3 - , CF3CO2 - , Cl - , Br -, I - , BF4 - , SO4 - , CF3SO3 - , (FSO2)2N - , (C2F5SO2)2N - , (C2F5SO2)(CF3SO2)N - , and (CF3SO2)2N - It may be a compound containing one or more anions selected from among.

[0149] 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.

[0150] In the solid electrolyte layer, the weight ratio of the solid electrolyte to 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 secondary battery can be improved.

[0151] The thickness of the solid electrolyte layer (300) may be 5 μm to 200 μm, for example, 20 μm to 150 μm, or 40 μm to 100 μm.

[0152] cathode

[0153] An anode for an all-solid-state secondary battery comprises a current collector and a negative electrode active material layer positioned on the current collector. The negative electrode active material layer comprises a negative electrode active material, may further comprise a binder and / or a conductive material, and may optionally comprise the solid electrolyte described above.

[0154] The above negative electrode active material includes 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.

[0155] 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.

[0156] As the above lithium metal alloy, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0157] 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 alloy (wherein Q is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn-based negative electrode active materials include Sn, SnO2, Sn-R alloy (wherein R is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), and at least one of these may be mixed with SiO2 for use. The above elements Q and R may be selected from the group consisting of 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, and combinations thereof.

[0158] For example, the negative active material may include silicon-carbon composite particles. The average particle diameter (D50) of the silicon-carbon composite particles may be, for example, 0.5 μm to 20 μm. The average particle diameter (D50) is measured by a particle size analyzer and refers to the diameter of particles having a cumulative volume of 50% by volume in a particle size distribution. With respect to 100 wt% of the silicon-carbon composite particles, silicon may be included in an amount of 10 wt% to 60 wt% and carbon may be included in an amount of 40 wt% to 90 wt%. The silicon-carbon composite particles may include, for example, a core including silicon particles and a carbon coating layer positioned on a surface of the core. The average particle diameter (D50) of the silicon particles in the core may be, for example, 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles may exist as silicon alone, in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon is SiO x (0 <x<2)로 표시될 수 있다. 또한, 상기 탄소 코팅층의 두께는 약 5 nm 내지 100 nm일 수 있다.

[0159] For example, the silicon-carbon composite particle may include a core including silicon particles and crystalline carbon, and a carbon coating layer located on the surface of the core and including amorphous carbon. For example, in the silicon-carbon composite particle, the amorphous carbon may not be present in the core but may be present only in the carbon coating layer. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof, and the amorphous carbon may be formed from coal pitch, mesophase pitch, petroleum pitch, coal oil, petroleum heavy oil, or a polymer resin (phenol resin, furan resin, polyimide resin, etc.). At this time, the content of the crystalline carbon may be 10 wt% to 70 wt%, and the content of the amorphous carbon may be 20 wt% to 40 wt% with respect to 100 wt% of the silicon-carbon composite particle.

[0160] In the above silicon-carbon composite particle, the core may include a void in the central portion. The radius of the void may be 30% to 50% of the radius of the silicon-carbon composite particle.

[0161] The silicon-carbon composite particles described above can effectively suppress problems such as volume expansion, structural collapse, or particle crushing due to charge and discharge, thereby preventing the phenomenon of conductive path disconnection, realizing high capacity and high efficiency, and are advantageous for use under high voltage or fast charging conditions.

[0162] 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. When the Si-based negative electrode active material or Sn-based negative electrode active material and the carbon-based negative electrode active material are used in combination, the mixing ratio can be 1:99 to 90:10 by weight.

[0163] 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.

[0164] 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.

[0165] 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 collector. The binder may be an insoluble binder, a water-soluble binder, or a combination thereof.

[0166] The above-mentioned non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, an ethylene propylene copolymer, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0167] 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.

[0168] When a water-soluble binder is used as the negative electrode binder, a cellulose-based compound capable of imparting viscosity as a type of thickener may be further included. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or an alkali metal salt thereof. The alkali metal may be Na, K, or Li. 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.

[0169] The above conductive material is used to provide conductivity to the electrode, and in the battery to be formed, any material that does not cause a chemical change and is electronically conductive can be used. Examples of conductive materials that can be used include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials including copper, nickel, aluminum, silver, etc. and in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or conductive materials including mixtures thereof.

[0170] The negative electrode current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0171] As another example, the negative electrode for an all-solid-state secondary battery may be a precipitation-type negative electrode. The precipitation-type negative electrode may refer 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 or deposited on the negative electrode when the battery is charged, and this acts as a negative electrode active material.

[0172] Fig. 2 is a schematic cross-sectional view of an all-solid-state secondary battery including a precipitation-type negative electrode. 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 secondary 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 during charging, high-density lithium metal is precipitated or deposited between the current collector (401) and the negative electrode coating layer (405) or on 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 secondary battery that has been charged more than once, the precipitation-type negative electrode (400') may include, for example, 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 lithium metal layer (404) 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, a lithium layer, a lithium deposition layer, or a negative electrode active material layer.

[0173] In this case, the aforementioned area or first solid electrolyte layer can be said to be a surface in contact with the cathode coating layer (405).

[0174] The above cathode coating layer (405) may be referred to as a lithium electrodeposition induction layer or a cathode catalyst layer, and may include a metal, carbon material, or a combination thereof that acts as a catalyst.

[0175] The metal may be a lithium-philic metal, and 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 several types of alloys. When the metal is present in the form of particles, the average particle diameter (D50) thereof may be about 4 μm or less, and may be, for example, 10 nm to 4 μm.

[0176] 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.

[0177] 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 secondary 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.

[0178] The above-described cathode coating layer (405) may include, for example, the above-described lithium-philic metal and amorphous carbon, in which case the precipitation of the lithium metal may be effectively promoted. As a specific example, the cathode coating layer (405) may include a composite in which a lithium-philic metal is supported on amorphous carbon.

[0179] The above cathode coating layer (405) may further include a binder, and the binder may be, for example, a conductive binder. In addition, the above cathode coating layer (405) may further include general additives such as fillers, dispersants, and ionic conductive agents.

[0180] 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 ㎛.

[0181] 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 planarize the precipitated form of the lithium metal layer (404) and further improve the characteristics of the all-solid-state secondary 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.

[0182] The lithium metal layer (404) may include lithium metal or a lithium alloy. The lithium alloy may be, for example, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, or a Li-Si alloy.

[0183] The thickness of the lithium metal layer (404) may be 1 μm to 500 μm, 1 μm to 200 μm, 1 μm to 100 μm, or 1 μm to 50 μm. If the thickness of the lithium metal layer (404) is too thin, it may be difficult to perform the role of a lithium storage, and if it is too thick, the battery volume may increase and performance may deteriorate.

[0184] When such a precipitation-type cathode is applied, the cathode coating layer (405) can play a role in protecting the lithium metal layer (404) and suppressing the precipitation growth of lithium deadlight. Accordingly, short-circuiting and capacity reduction of the all-solid-state battery can be suppressed, and the life characteristics can be improved.

[0185] The above-mentioned all-solid-state secondary battery may be a unit cell having a structure of positive electrode / solid electrolyte layer / negative electrode, a bi-cell having a structure of negative electrode / solid electrolyte layer / positive electrode / solid electrolyte layer / negative electrode, or a laminated battery in which the structure of the unit cell is repeated.

[0186] The shape of the above-mentioned all-solid-state secondary 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 secondary battery can be applied to large-scale batteries used in electric vehicles, etc. For example, the above-mentioned all-solid-state secondary battery can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it can be used in fields requiring a large amount of power storage, and for example, it can be used in electric bicycles or power tools, etc. In addition, the above-mentioned all-solid-state secondary battery can be used in various fields such as portable electronic devices.

[0187] Hereinafter, examples and comparative examples of the present invention are described. The following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples.

[0188] Example 1-1

[0189] 1. Manufacturing of the anode

[0190] LiNi 0.945 Co 0.04 Al 0.015 O2 positive electrode active material 84.9 wt%, argyrodite type solid electrolyte of Li6PS5Cl (D 50 =1㎛) 13.61 wt%, PVdF binder 1 wt%, carbon nanotube conductive material 0.35 wt%, and hydrogenated nitrile butadiene rubber (HNBR) 0.14 wt% as a dispersant were mixed in an isobutyryl isobutyrate (IBIB) solvent to prepare a positive electrode composition. This was applied to a positive electrode current collector and dried to form a positive electrode active material layer.

[0191] A safety functional layer composition was prepared by mixing 1 part by weight of PVdF binder with 100 parts by weight of LiFePO4, applying the composition onto the positive electrode active material layer, and drying to form a safety functional layer with a thickness of approximately 1 μm. Thereafter, a positive electrode was prepared by hydrostatic pressing (WIP; 500 Mpa, 85°C, 30 min).

[0192] 2. Manufacturing of all-solid-state secondary batteries

[0193] Carbon black with a primary particle size of about 30 nm and an average particle size (D 50 ) was prepared by mixing silver (Ag) having a diameter of approximately 60 nm in a weight ratio of 3:1, and 0.25 g of the above complex was added to 2 g of an NMP solution containing 7 wt% of polyvinylidene fluoride binder and mixed to prepare a negative electrode coating layer composition. This was applied onto a negative electrode current collector and then dried, thereby preparing a deposition-type negative electrode in which a negative electrode coating layer was formed on the current collector.

[0194] Argyrodite-type solid electrolyte of Li6PS5Cl (D 50 =3㎛) was added to an IBIB solvent containing an acrylic binder and mixed to prepare a composition for forming a solid electrolyte layer. The composition includes 98.5 wt% of the solid electrolyte and 1.5 wt% of the binder. The composition was cast on a release film and dried at room temperature to prepare a solid electrolyte layer.

[0195] The prepared positive electrode, negative electrode, and solid electrolyte layers were cut, a solid electrolyte layer was laminated on the positive electrode, and then a negative electrode was laminated on top of that. This was sealed in a pouch shape and subjected to high-temperature hydrostatic pressing at 80°C and 500 MPa for 30 minutes to manufacture an all-solid-state secondary battery.

[0196] Example 1-2

[0197] A positive electrode and an all-solid-state secondary battery were manufactured in substantially the same manner as in Example 1-1, except that the thickness of the safety functional layer in the manufacture of the positive electrode was changed to 5 μm.

[0198] Example 1-3

[0199] A positive electrode and an all-solid-state secondary battery were manufactured in substantially the same manner as in Example 1-1, except that the thickness of the safety functional layer in the manufacture of the positive electrode was changed to 8 μm.

[0200] Comparative Example 1-1

[0201] A positive electrode and an all-solid-state secondary battery were manufactured in substantially the same manner as in Example 1-1, except that the thickness of the safety functional layer in the manufacture of the positive electrode was changed to 10 μm.

[0202] Comparative Example 1-2

[0203] A positive electrode and an all-solid-state secondary battery were manufactured in substantially the same manner as in Example 1-1, except that a positive electrode was manufactured by forming only a positive electrode active material layer on a current collector without introducing a safety functional layer.

[0204]

[0205] Example 2-1

[0206] 1. Manufacturing of the anode

[0207] LiNi 0.945 Co 0.04 Al 0.015 O2 positive electrode active material 84.9 wt%, argyrodite type solid electrolyte of Li6PS5Cl (D 50 =1㎛) 13.61 wt%, PVdF binder 1 wt%, carbon nanotube conductive material 0.35 wt%, and hydrogenated nitrile butadiene rubber (HNBR) 0.14 wt% as a dispersant were mixed in an isobutyryl isobutyrate (IBIB) solvent to prepare a positive electrode composition. This was applied to a positive electrode current collector and dried to form a positive electrode active material layer.

[0208] Other than that, the positive electrode and the all-solid-state secondary battery were manufactured in substantially the same manner as in Example 1-1.

[0209] Example 2-2

[0210] A positive electrode and an all-solid-state secondary battery were manufactured in substantially the same manner as in Example 2-1, except that the weight ratio of LiFePO4 and Li6PS5Cl in the safety functional layer of the positive electrode was changed to 90:10.

[0211] Example 2-3

[0212] A cathode and an all-solid-state secondary battery were manufactured in substantially the same manner as in Example 2-1, except that the weight ratio of LiFePO4 and Li6PS5Cl in the safety functional layer of the cathode was changed to 85:15.

[0213] Example 2-4

[0214] A positive electrode and an all-solid-state secondary battery were manufactured in substantially the same manner as in Example 2-1, except that the weight ratio of LiFePO4 and Li6PS5Cl in the safety functional layer of the positive electrode was changed to 80:20.

[0215] Example 2-5

[0216] A positive electrode and an all-solid-state secondary battery were manufactured in substantially the same manner as in Example 2-1, except that the weight ratio of LiFePO4 and Li6PS5Cl in the safety functional layer of the positive electrode was changed to 75:25.

[0217] Comparative Example 2-1

[0218] A positive electrode and an all-solid-state secondary battery were manufactured in substantially the same manner as in Example 2-1, except that a positive electrode was manufactured by forming only a positive electrode active material layer on a current collector without introducing a safety functional layer.

[0219]

[0220] Example 3-1

[0221] 1. Manufacturing of the anode

[0222] LiNi 0.945 Co 0.04 Al 0.015 O2 positive electrode active material 84.9 wt%, argyrodite type solid electrolyte of Li6PS5Cl (D 50=1㎛) 13.61 wt%, PVdF binder 1 wt%, carbon nanotube conductive material 0.35 wt%, and hydrogenated nitrile butadiene rubber (HNBR) 0.14 wt% as a dispersant were mixed in an isobutyryl isobutyrate (IBIB) solvent to prepare a positive electrode composition. This was applied to a positive electrode current collector and dried to form a positive electrode active material layer.

[0223] Other than that, the positive electrode and the all-solid-state secondary battery were manufactured in substantially the same manner as in Example 1-1.

[0224] Examples 3-2 to 3-5

[0225] A cathode and an all-solid-state secondary battery were manufactured in substantially the same manner as in Example 3-1, except that the content of the CNT conductive material in the safety functional layer of the cathode was changed as shown in Table 3 below.

[0226] Comparative Example 3-1

[0227] A positive electrode and an all-solid-state secondary battery were manufactured in substantially the same manner as in Example 3-1, except that the content of the CNT conductive material in the safety functional layer of the positive electrode was changed to 10 parts by weight.

[0228] Comparative Example 3-2

[0229] A positive electrode and an all-solid-state secondary battery were manufactured in substantially the same manner as in Example 3-1, except that a positive electrode was manufactured by forming only a positive electrode active material layer on a current collector without introducing a safety functional layer.

[0230]

[0231] (Example of evaluation)

[0232] Evaluation Example 1-1: High-Rate Characteristic Evaluation

[0233] The all-solid-state secondary batteries manufactured in Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-2 were charged to 4.25 V at a constant current of 0.1 C and to a constant voltage of 0.05 C at 45°C to measure the charge capacity, and then discharged to 2.5 V at a constant current of 0.1 C to measure the discharge capacity.

[0234] Next, the all-solid-state secondary battery was charged to 4.25 V at a constant current of 0.1 C at 45°C and to 0.05 C at a constant voltage to measure the charge capacity, and then discharged to 2.5 V at a constant current of 1.0 C to measure the discharge capacity.

[0235] The ratio of the discharge capacity at 1.0C to the discharge capacity at 0.1C was calculated and presented as rate characteristics (%) in Table 1 below.

[0236] Evaluation Example 1-2: Life Characteristics Evaluation

[0237] Following the above evaluation example 1-1, the life characteristics of the all-solid-state secondary battery were evaluated by repeating 300 cycles of 0.33C charging and 0.33C discharging in a voltage range of 2.5 V to 4.25 V at 45°C.

[0238] The ratio of the discharge capacity after 300 cycles to the initial discharge capacity was calculated and presented as the capacity retention rate (%) in Table 1 below. A battery was judged to be good only when the capacity retention rate (%) was maintained at 80% or higher.

[0239] Evaluation Example 1-3: Penetration Safety Evaluation

[0240] The all-solid-state secondary batteries manufactured in Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-2 were charged to 4.25 V at a constant current of 0.1 C and a constant voltage of 0.05 C at 45°C.

[0241] After the above-mentioned charged solid-state secondary battery was left at room temperature for 1 hour, a penetration safety evaluation was conducted.

[0242] In the penetration safety evaluation, a stainless steel nail with a diameter of 3 mm was used to penetrate the center of the all-solid-state secondary battery at a penetration speed of 50 mm / s. If no ignition occurred, it was evaluated as 'OK', and if ignition occurred, it was evaluated as 'NG', and the results are shown in Table 1 below.

[0243] Safety Function Layer Composition Thickness (㎛) Rate Characteristics (1C / 0.1C, %) Capacity Retention Rate (%, @ 300cyc, 45℃) Penetration Safety Evaluation Example 1-1 LiFePO4 184.28 3.3 OK Example 1-2 LiFePO4 583.98 3.1 OK Example 1-3 LiFePO4 882.18 1.4 OK Comparative Example 1-1 LiFePO4 1071.87 5.1 OK Comparative Example 1-2 -087.38 5.2 NG

[0244] Referring to Table 1, it can be confirmed that the all-solid-state secondary batteries of Examples 1-1 to 1-3 have superior penetration safety compared to Comparative Example 1-2, while the rate characteristics and capacity retention rate of the batteries are at the same level as Comparative Example 1-2.

[0245] Additionally, in the case of Comparative Example 1-1, it can be confirmed that the thickness of the safety functional layer is excessively thick, and thus the rate characteristics and capacity retention rate of the battery are lower than those of the examples.

[0246]

[0247] Evaluation Example 2-1: High-Rate Characteristic Evaluation

[0248] The all-solid-state secondary batteries manufactured in Examples 2-1 to 2-5 and Comparative Example 2-1 were charged to 4.25 V at a constant current of 0.1 C and to a constant voltage of 0.05 C at 45°C to measure the charge capacity, and then discharged to 2.5 V at a constant current of 0.1 C to measure the discharge capacity.

[0249] Next, the all-solid-state secondary battery was charged to 4.25 V at a constant current of 0.1 C at 45°C and to 0.05 C at a constant voltage to measure the charge capacity, and then discharged to 2.5 V at a constant current of 1.0 C to measure the discharge capacity.

[0250] The ratio of the discharge capacity at 1.0C to the discharge capacity at 0.1C was calculated and presented as rate characteristics (%) in Table 2 below.

[0251] Evaluation Example 2-2: Life Characteristics Evaluation

[0252] Following Evaluation Example 1, the all-solid-state secondary batteries manufactured in Examples 2-1 to 2-5 and Comparative Example 2-1 were subjected to 300 cycles of 0.33C charging and 0.33C discharging in a voltage range of 2.5 V to 4.25 V at 45°C to evaluate their lifespan characteristics.

[0253] The ratio of the discharge capacity after 300 cycles to the initial discharge capacity was calculated and presented as the capacity retention rate (%) in Table 2 below. A capacity retention rate (%) of 80% or more was considered good.

[0254] Evaluation Example 2-3: Penetration Safety Evaluation

[0255] The all-solid-state secondary batteries manufactured in Examples 2-1 to 2-5 and Comparative Example 2-1 were charged to 4.25 V at a constant current of 0.1 C and a constant voltage of 0.05 C at 45°C.

[0256] After the above-mentioned charged solid-state secondary battery was left at room temperature for 1 hour, a penetration safety evaluation was conducted.

[0257] In the penetration safety evaluation, a stainless steel nail with a diameter of 3 mm was used to penetrate the center of the all-solid-state secondary battery at a penetration speed of 50 mm / s. If no ignition occurred, it was evaluated as 'OK', and if ignition occurred, it was evaluated as 'NG'. The results are shown in Table 2 below.

[0258] Safety Function Layer LiFePO4: Li6PS5Cl Rate Characteristics (1C / 0.1C, %) Capacity Retention (%, @300cyc, 45℃) Penetration Safety Evaluation Example 2-195: 585.884.1 OK Example 2-290: 1086.184.4 OK Example 2-385: 1586.984.9 OK Example 2-480: 2087.385.2 OK Example 2-575: 2587.285.1 OK Comparative Example 2-1-87.385.2 NG

[0259] Referring to Table 2, it can be confirmed that the all-solid-state secondary batteries of Examples 2-1 to 2-5 have superior penetration safety compared to Comparative Example 2-1, while the rate characteristics and capacity retention rate of the batteries are at the same level as Comparative Example 2-1.

[0260] Evaluation Example 3-1: High-Rate Characteristic Evaluation

[0261] The all-solid-state secondary batteries manufactured in Examples 3-1 to 3-5 and Comparative Examples 3-1 to 3-2 were charged to 4.25 V at a constant current of 0.1 C and to a constant voltage of 0.05 C at 45°C to measure the charge capacity, and then discharged to 2.5 V at a constant current of 0.1 C to measure the discharge capacity.

[0262] Next, the all-solid-state secondary battery was charged to 4.25 V at a constant current of 0.1 C at 45°C and to 0.05 C at a constant voltage to measure the charge capacity, and then discharged to 2.5 V at a constant current of 1.0 C to measure the discharge capacity.

[0263] The ratio of the discharge capacity at 1.0C to the discharge capacity at 0.1C was calculated and presented as rate characteristics (%) in Table 3 below.

[0264] Evaluation Example 3-2: Life Characteristics Evaluation

[0265] Following the above Evaluation Example 3-1, the precursor secondary batteries manufactured in Examples 3-1 to 3-5 and Comparative Examples 3-1 to 3-2 were subjected to 300 cycles of 0.33C charging and 0.33C discharging in a voltage range of 2.5 V to 4.25 V at 45°C to evaluate the life characteristics.

[0266] The ratio of the discharge capacity after 300 cycles to the initial discharge capacity was calculated and presented as the capacity retention rate (%) in Table 3 below. A battery was judged to be good only when the capacity retention rate (%) was maintained at 80% or higher.

[0267] Evaluation Example 3-3: Penetration Safety Evaluation

[0268] The all-solid-state secondary batteries manufactured in Examples 3-1 to 3-5 and Comparative Examples 3-1 to 3-2 were charged at 45°C with a constant current of 0.1 C to 4.25 V and a constant voltage of 0.05 C.

[0269] After the above-mentioned charged solid-state secondary battery was left at room temperature for 1 hour, a penetration safety evaluation was conducted.

[0270] In the penetration safety evaluation, a stainless steel nail with a diameter of 3 mm was used to penetrate the center of the all-solid-state secondary battery at a penetration speed of 50 mm / s. If no ignition occurred, it was evaluated as 'OK', and if ignition occurred, it was evaluated as 'NG'. The results are shown in Table 3 below.

[0271] Safety Function Layer Composition Rate Characteristics (1C / 0.1C, %) Capacity Retention Rate (%, @300cyc, 45℃) Penetration Safety Evaluation LiFePO4: Li6PS5Cl Conductive Material Content (Parts by Weight) Example 3-185: 150.585.383.9 OK Example 3-285: 151.085.884.2 OK Example 3-385: 151.586.284.6 OK Example 3-485: 152.086.584.5 OK Example 3-585: 155.086.984.9 OK Comparative Example 3-185: 151087.185.1NG Comparative Example 3-2-87.385.2NG

[0272] Referring to Table 3, it can be confirmed that in the case of the all-solid-state secondary batteries of Examples 3-1 to 3-5, penetration safety is superior to that of Comparative Examples 3-1 to 3-2, while the rate characteristics and capacity retention of the batteries are at the same level as those of Comparative Examples 3-1 to 3-2. In the case of Comparative Example 3-1, it can be confirmed that the penetration safety is inferior to that of the Examples because the content of the conductive material included in the safety functional layer is excessive.

[0273]

[0274] Although the preferred embodiments 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 concepts defined in the following claims also fall within the scope of the present invention.

[0275]

[0276] (Explanation of symbols)

[0277] 100: All-solid-state secondary battery 200: Cathode

[0278] 201: Cathode current collector 203: Cathode active material layer

[0279] 205: Safety functional layer 300: Solid electrolyte layer

[0280] 400: Cathode 401: Cathode current collector

[0281] 403: Negative active material layer 400': Precipitation type negative electrode

[0282] 404: Lithium metal layer 405: Cathode coating layer

[0283] 500: Elastic layer

Claims

1. A positive electrode comprising a positive electrode current collector, a positive electrode active material layer located on the positive electrode current collector, and a safety functional layer located on the positive electrode active material layer; A negative electrode; A all-solid-state secondary battery comprising a solid electrolyte layer located between the positive electrode and the negative electrode, wherein the positive electrode active material layer comprises a positive electrode active material and a sulfide-based solid electrolyte, the safety functional layer comprises an olivine-based positive electrode active material, and the solid electrolyte layer comprises a sulfide-based solid electrolyte. All-solid-state secondary battery.

2. According to claim 1, the olivine-based positive electrode active material comprises lithium iron phosphate, lithium manganese iron phosphate, lithium manganese phosphate, lithium titanium phosphate, or a combination thereof. All-solid-state secondary battery.

3. According to claim 1, the olivine-based positive electrode active material is represented by the following Chemical Formula 1, Chemical Formula 2, Chemical Formula 3, Chemical Formula 4, or Chemical Formula 5. All-solid-state secondary battery: [Chemical Formula 1] Li a1 Fe (1-x1) M 1 x1 PO 4 In chemical formula 1, 0.90≤a1≤1.5, 0≤x1≤0.4, and M 1 is Al, Ca, Ce, Cr, Cu, Co, La, Mg, Mo, Nb, Ni, Sn, Sr, V, W, Y, Zn, Zr, or a combination thereof, [Chemical Formula 2] Li a2 Mn x2 Fe (1-x2-y2) M 2 y2 P.O. 4 In chemical formula 2, 0.90≤a2≤1.5, 0.1≤x2≤0.9, M 2 is Al, Ca, Ce, Cr, Cu, Co, La, Mg, Mo, Nb, Ni, Sn, Sr, V, W, Y, Zn, Zr, or a combination thereof, [Chemical Formula 3] Li a3 Mn (1-x3) M 3 x3 PO 4 In chemical formula 3, 0.90≤a3≤1.5, 0≤x3≤0.4, and M 3 is Al, Ca, Ce, Cr, Cu, Co, La, Mg, Mo, Nb, Ni, Sn, Sr, V, W, Y, Zn, Zr, or a combination thereof, [Chemical Formula 4] Li a4 You (2-x4) M 4 x4 (PO 4 ) 3 In chemical formula 4, 0.90≤a4≤1.5, 0≤x4≤0.4, and M 4 is Al, Ca, Ce, Cr, Cu, Co, La, Mg, Mo, Nb, Ni, Sn, Sr, V, W, Y, Zn, Zr, or a combination thereof, [Chemical Formula 5] Li a5 You (1-x5) M 5 x5 PO 5 In chemical formula 5, 0.90≤a5≤1.5, 0≤x5≤0.4, and M 5 is Al, Ca, Ce, Cr, Cu, Co, La, Mg, Mo, Nb, Ni, Sn, Sr, V, W, Y, Zn, Zr, or a combination thereof.

4. According to claim 1, The above olivine-based cathode active material is LiFePO 4 , LiMn 0.7 Fe 0.3 PO 4 , LiMn 0.6 Fe 0.4 PO 4 , LiMn 0.5 Fe 0.5 PO 4 , LiMn 0.4 Fe 0.6 PO 4 , LiMn 0.3 Fe 0.7 PO 4 , LiMnPO 4 , LiTiPO 5 , LiTi 2 (PO 4 ) 3 , or a combination thereof, an all-solid-state secondary battery.

5. According to claim 1, the average particle diameter (D50) of the olivine-based positive electrode active material is 10 nm to 2 μm. All-solid-state secondary battery.

6. According to claim 1, the olivine-based positive electrode active material is contained in an amount of 70% to 99.9% by weight based on 100% by weight of the safety functional layer. All-solid-state secondary battery.

7. According to claim 1, the safety functional layer further comprises a sulfide-based solid electrolyte. All-solid-state secondary battery.

8. According to claim 7, the sulfide-based solid electrolyte is contained in an amount of 1% to 30% by weight based on 100% by weight of the safety functional layer. All-solid-state secondary battery.

9. According to claim 7, the weight ratio of the olivine-based positive electrode active material and the sulfide-based solid electrolyte contained in the safety functional layer is 70:30 to 97:

3. All-solid-state secondary battery.

10. According to claim 7, The average particle size (D) of the sulfide-based solid electrolyte included in the above safety functional layer 50 ) is an all-solid-state secondary battery having a thickness of 0.1 μm to 1.9 μm.

11. According to claim 1, the safety functional layer further comprises a conductive material. All-solid-state secondary battery.

12. According to claim 11, the conductive material comprises a carbon-based material, a metal-based material, a conductive polymer, or a mixture thereof. All-solid-state secondary battery.

13. According to claim 11, The above-mentioned challenge material is an all-solid-state secondary battery including carbon nanotubes, carbon nanofibers, or a combination thereof.

14. In Article 11, An all-solid-state secondary battery, wherein the above-mentioned challenge material is included in an amount of 0.5 wt% to 15 wt% with respect to 100 wt% of the safety functional layer.

15. In paragraph 1, The above safety functional layer further includes a binder, An all-solid-state secondary battery, wherein the binder comprises a polymer including polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, or a combination thereof.

16. In paragraph 15, An all-solid-state secondary battery, wherein the binder is included in an amount of 0.1 wt% to 25 wt% based on 100 wt% of the safety functional layer.

17. In paragraph 1, The positive electrode active material included in the positive electrode active material layer is an all-solid-state secondary battery including a lithium nickel-based oxide represented by the following chemical formula 6 or a lithium cobalt-based oxide represented by the following chemical formula 7: [Chemical formula 6] Li a6 Ni x6 M 6 y6 M 7 z6 O 2-b6 X b6 In the above chemical formula 6, 0.9≤a6≤1.8, 0.3≤x6≤1, 0≤y6≤0.7, 0≤z6≤0.7, 0.9≤x6+y6+z6≤1.1, and 0≤b6≤0.1, and M 6 and M 7 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S. [Chemical formula 7] Li a7 Co x7 M 8 y7 O 2-b7 X b7 In the above chemical formula 7, 0.9≤a7≤1.8, 0.7≤x7≤1, 0≤y7≤0.3, 0.9≤x7+y7≤1.1, and 0≤b7≤0.1, and M 8 is at least one element selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sn, Sr, Ti, V, W, Y, Zn and Zr, and X is at least one element selected from the group consisting of F, P, and S.

18. In paragraph 1, An all-solid-state secondary battery, wherein the average particle diameter (D50) of the positive electrode active material included in the positive electrode active material layer is 1 ㎛ to 25 ㎛.

19. In paragraph 7, An all-solid-state secondary battery, wherein the sulfide-based solid electrolyte of the positive electrode active material layer, the sulfide-based solid electrolyte of the safety functional layer, and the sulfide-based solid electrolyte of the solid electrolyte layer are the same as or different from each other, and each includes an argyrodite-type sulfide.

20. In Article 19, The above azirodite-type sulfide is an all-solid-state secondary battery comprising a compound represented by the following chemical formula 10: [Chemical Formula 10] (Li a M 11 b M 12 c )(P d M 13 e )(S f M 14 g )X h In the above chemical formula 10, 4≤a≤8, and M 11 is Mg, Cu, Ag, or a combination thereof, and 0≤b<0.5, and M 12 is Na, K, or a combination thereof, 0≤c<0.5, and M 13 is Sn, Zn, Si, Sb, Ge, or a combination of these, and 0 <d<4, 0≤e<1 이고, M 14 is O, SO n , or a combination thereof, and 1.5≤n≤5, 3≤f≤12, 0≤g<2, and X is F, Cl, Br, I, or a combination thereof, and 0≤h≤2.

21. In Article 19, The above argyrodite type sulfide is Li 3 PS 4 , Li 7 P 3 S 11 , Li 7 PS 6 , Li 6 PS 5 Cl, Li 6 PS 5 Br, Li 5.8 PS 4.8 Cl 1.2 , Li 6.2 PS 5.2 Br 0.8 , Li 5.75 PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )PS 4.75 Cl 1.25 , (Li 5.72 Cu 0.03 )PS 4.75 Cl 1.25 , (Li 5.69 Cu 0.06 )P(S 4.70 (SO 4 ) 0.05 )Cl 1.25 , (Li 5.69 Cu 0.06 )P(S 4.60 (SO 4 ) 0.15 )Cl 1.25 , (Li 5.72 Cu 0.03 )P(S 4.725 (SO 4 ) 0.025 )Cl 1.25 , (Li 5.72 Na 0.03 )P(S 4.725 (SO 4 ) 0.025 )Cl 1.25 , Li 5.75 P(S 4.725 (SO 4 ) 0.025 )Cl 1.25 , or a combination thereof, an all-solid-state secondary battery.

22. In paragraph 1, The sulfide-based solid electrolyte of the above positive electrode active material layer has an average particle diameter (D 50 ) is 0.1㎛ to 1.9㎛, and the sulfide-based solid electrolyte of the solid electrolyte layer has an average particle diameter (D 50 ) is an all-solid-state secondary battery having a thickness of 2 μm to 5 μm.

23. In paragraph 1, An all-solid-state secondary battery, wherein the above-mentioned sulfide-based solid electrolyte is included in an amount of 0.1 wt% to 35 wt% with respect to 100 wt% of the above-mentioned positive electrode active material layer.

24. In paragraph 1, An all-solid-state secondary battery, wherein the thickness of the safety function layer is 1 ㎛ to 15 ㎛.

25. In paragraph 1, An all-solid-state secondary battery, wherein the solid electrolyte layer has a thickness of 5 ㎛ to 200 ㎛.

26. In paragraph 1, An all-solid-state secondary battery, comprising: a negative electrode; a negative electrode coating layer positioned on the negative electrode collector and containing a carbon material, a lithium-philic metal, or a combination thereof; and a lithium metal layer positioned between the negative electrode collector and the negative electrode coating layer and formed by charging.

Images