All-solid rechargeable battery

Abstract

An all-solid rechargeable battery is provided. The all-solid rechargeable battery according to one embodiment comprises: a plurality of unit cells, each formed by stacking a negative electrode, a solid electrolyte layer and a positive electrode; and ceramic insulating layers provided between the negative electrodes of at least neighboring unit cells and on the negative electrode positioned at the outermost side of all the unit cells.

Description

All-solid-state secondary battery

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

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

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

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

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

[0006] One embodiment provides an all-solid-state secondary battery that prevents damage due to external impact. One embodiment provides an all-solid-state secondary battery in which a ceramic insulating layer prevents direct short circuiting between the positive and negative electrodes when the cell is damaged by external impact, thereby reducing the amount of heat generated due to the short circuit.

[0007] One embodiment provides an all-solid-state secondary battery that effectively lowers temperature by assisting heat dissipation when heat generation occurs.

[0008] An all-solid-state secondary battery according to one embodiment comprises unit cells formed by stacking a cathode, a solid electrolyte layer, and an anode, and a plurality of unit cells, and ceramic insulating layers provided on the cathodes located at least between the cathodes of adjacent unit cells and at the outermost portion of all the unit cells.

[0009] Each of the above unit cells may include a positive electrode current collector positioned in the middle, a positive electrode active material layer sequentially laminated on each of both sides of the positive electrode current collector forming the positive electrode, the solid electrolyte layer, a negative electrode active material layer forming the negative electrode, and a negative electrode current collector.

[0010] The above ceramic insulating layers may be provided on the outer surface of the negative electrode current collector.

[0011] Among the neighboring unit cells, a first cell includes the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode collector, which are sequentially laminated on each of both sides of the positive electrode collector, and a second cell neighboring the first cell includes the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode collector, which are sequentially laminated on each of both sides of the positive electrode collector, and a ceramic insulating layer positioned between the first cell and the second cell among the ceramic insulating layers may be arranged as a single layer between a pair of the negative electrode collectors.

[0012] The above ceramic insulating layer may include at least one of alumina and boehmite and a binder.

[0013] The above ceramic insulating layer may contain 5 to 10 wt% of binder and 90 to 95 wt% of ceramic particles.

[0014] The thickness of the above ceramic insulating layer may be 10㎛ to 20㎛.

[0015] Each of the above unit cells may include a positive electrode active material layer sequentially laminated on one side of a positive electrode current collector forming the positive electrode, the solid electrolyte layer, a negative electrode active material layer forming the negative electrode, and a negative electrode current collector.

[0016] Among the above-described neighboring unit cells, a first cell includes the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode collector, which are sequentially laminated on one surface of the positive electrode collector, and a second cell neighboring the first cell includes the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode collector, which are sequentially laminated on one surface of the positive electrode collector, and among the above-described ceramic insulating layers, a ceramic insulating layer positioned between the positive electrode collector of the first cell and the negative electrode collector of the second cell may be arranged as a single layer.

[0017] An all-solid-state secondary battery according to one embodiment includes a laminate formed by laminating a negative electrode, a solid electrolyte layer, and a positive electrode, and a ceramic insulating layer including a conductive material provided on the opposite side of the solid electrolyte layer of the negative electrode located at the outermost part of the laminate.

[0018] The laminate may include a positive electrode current collector positioned in the middle, a positive electrode active material layer sequentially laminated on each of both sides of the positive electrode current collector forming the positive electrode, the solid electrolyte layer, a negative electrode active material layer forming the negative electrode, and a negative electrode current collector.

[0019] The above ceramic insulating layer may contain 30 to 95 wt% of ceramic, 0.1 to 30 wt% of conductive material, and 1 to 40 wt% of binder.

[0020] The above ceramic insulating layer may contain 80 to 90 wt% of ceramic, 5 to 10 wt% of conductive material, and 5 to 10 wt% of binder.

[0021] In a penetration test of a through pin, the temperature measurement area in the laminate includes the central portion where the through pin is inserted and the peripheral portion at least 30 mm away from the through pin, and the heat dissipation characteristics can be compared by the temperature difference ratio between the central portion and the peripheral portion.

[0022] The temperature difference ratio between the central portion and the peripheral portion may be 9 to 39%.

[0023] The temperature difference ratio between the central portion and the peripheral portion may be 9 to 12%.

[0024] The maximum temperature ratio in the central part above can be 15 to 35%.

[0025] The maximum temperature ratio in the central part above can be 15-16%.

[0026] One embodiment has ceramic insulating layers including ceramic material between and on the outermost surface of a plurality of unit cells, thereby preventing damage due to external impact and preventing electrical short circuit between the cathode and the anode by the ceramic material in the event of damage.

[0027] One embodiment is that when a cell is damaged by an external impact, the ceramic insulating layer can prevent direct short circuit between the anode and cathode, thereby reducing the amount of heat generated due to the short circuit.

[0028] In one embodiment, the ceramic insulating layer prevents damage to the negative electrode current collector when damaged by an external impact, and can prevent damage to all negative electrode current collectors provided in each of the unit cells.

[0029] In one embodiment, the ceramic insulating layer can protect the cathode current collector from gases generated within the plurality of unit cells and can minimize porosity and gas permeability due to rolling.

[0030] One embodiment has ceramic insulating layers including a conductive material and a ceramic material on the outermost layer of the laminate, thereby preventing damage due to external impact, and in case of damage, preventing electrical short-circuiting between the cathode and anode by the ceramic material, and when heat generation occurs, the conductive material helps dissipate heat, thereby effectively lowering the temperature.

[0031] Figure 1 is a cross-sectional view showing an all-solid-state secondary battery according to one embodiment.

[0032] FIG. 2 is a cross-sectional view showing the formation of a lithium metal layer of an all-solid-state secondary battery according to one embodiment.

[0033] Figure 3 is a longitudinal cross-sectional view showing an all-solid-state secondary battery according to a first embodiment of the present invention.

[0034] Figure 4 is a longitudinal cross-sectional view showing an all-solid-state secondary battery according to a second embodiment of the present invention.

[0035] Figure 5 is a graph showing the temperature relationship over time when a nail is penetrated through an all-solid-state secondary battery.

[0036] Figure 6 is a graph showing the voltage relationship over time when a nail is penetrated in an all-solid-state secondary battery.

[0037] Figure 7 is a cross-sectional view showing an all-solid-state secondary battery according to a third embodiment of the present invention.

[0038] Figure 8 is a plan view showing the position where a penetration pin penetrates a laminate during a penetration experiment in the 11th to 14th experimental examples of the present invention and the second comparative example.

[0039] Figure 9 is a graph showing the temperature change over time in the central and peripheral parts through which the through pin penetrates in the 11th and 12th experimental examples of Figure 7.

[0040] 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.

[0041] 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.

[0042] To clearly illustrate various layers and regions in the drawings, their thicknesses are enlarged, and similar parts are designated by the same drawing reference numerals throughout the specification. When an element such as a layer, film, region, or plate is said to be "over" or "on" another element, this includes not only the case where it is "directly over" the other element, but also the case where there is another element in between. Conversely, when an element is said to be "directly over" another element, it means that there is no other element in between.

[0043] 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.

[0044] Cathode for all-solid-state secondary batteries

[0045] In one embodiment, a positive electrode for an all-solid-state secondary battery is provided, comprising a current collector and a positive electrode active material layer positioned on the current collector, wherein the positive electrode active material layer comprises at least one of a positive electrode active material, a sulfide-based solid electrolyte, a binder, and a conductive material. However, without limitation thereto, the positive electrode for an all-solid-state secondary battery may comprise more or less components than the components described above.

[0046] In one embodiment, the positive electrode for the all-solid-state secondary battery is manufactured by applying a positive electrode composition including at least one of a positive electrode active material, a sulfide-based solid electrolyte, a binder, and a conductive agent to a current collector, followed by drying and rolling.

[0047] positive electrode active material

[0048] The above-mentioned positive electrode active material can be applied without limitation as long as it is generally used in all-solid-state secondary batteries. For example, the above-mentioned positive electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium, and may include a compound represented by any one of the following chemical formulas.

[0049] Li a A 1-b X b D2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5);

[0050] 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);

[0051] Li a E 1-b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0052] Li a E 2-b Xb O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05);

[0053] 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);

[0054] 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);

[0055] 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);

[0056] 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);

[0057] 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);

[0058] Li a Ni 1-b-c Mr b X c O 2-αT2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α < 2);

[0059] The a Nor b E c G d O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1);

[0060] The a Nor b Co c Mn d G e O2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤0.5, 0.001 ≤ e ≤ 0.1);

[0061] The a NiG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0062] The a CoG b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0063] The a Mn 1-b G b O2(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0064] The a Mn2G b O4(0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1);

[0065] The a Mn 1-g G g PO4(0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5);

[0066] QO2; QS2; LiQS2;

[0067] V2O5; LiV2O5;

[0068] LiZO2;

[0069] LiNiVO4;

[0070] Li (3-f) J2(PO4)3(0 ≤ f ≤ 2);

[0071] Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2);

[0072] Li a FePO4(0.90 ≤ a ≤ 1.8).

[0073] 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.

[0074] 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).

[0075] The above positive electrode active material may include a lithium nickel-based oxide represented by the following chemical formula 1, a lithium cobalt-based oxide represented by the following chemical formula 2, a lithium iron phosphate-based compound represented by the following chemical formula 3, or a combination thereof.

[0076] [Chemical Formula 1]

[0077] Li a1 Ni x1 M 1 y1 M 2 1-x1-y1 O2

[0078] 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.

[0079] [Chemical Formula 2]

[0080] Li a2 Co x2 M 3 1-x2 O2

[0081] 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.

[0082] [Chemical Formula 3]

[0083] Li a3 Fe x3 M 4 (1-x3) PO4

[0084] 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.

[0085] 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.

[0086] 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.

[0087] Sulfide-based solid electrolyte

[0088] 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.

[0089] 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.

[0090] 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, thereby finely agitating them and mixing 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] In one embodiment, the positive electrode active material layer may include 50 wt% to 99.35 wt% of the positive electrode active material, 0.5 wt% to 35 wt% of the sulfide-based solid electrolyte, 0.1 wt% to 10 wt% of the fluorine-based resin binder, and 0.05 wt% to 5 wt% of the vanadium oxide, based on 100 wt% of the positive electrode active material layer. When this content range is satisfied, the positive electrode for an all-solid-state secondary battery can implement high capacity and high ionic conductivity while maintaining high adhesiveness, and the viscosity of the positive electrode composition can be maintained at an appropriate level, thereby improving processability.

[0097] bookbinder

[0098] 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.

[0099] Challenge

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] All-solid-state secondary battery

[0105] In one embodiment, an all-solid-state secondary battery is provided, which includes the aforementioned positive electrode and negative electrode and a solid electrolyte layer positioned between the positive electrode and negative electrode. The all-solid-state secondary battery may also be referred to as an all-solid-state battery or an all-solid-state lithium secondary battery.

[0106] Fig. 1 is a cross-sectional view of an all-solid-state secondary battery according to one embodiment. Referring to Fig. 1, the all-solid-state secondary battery (100) may have a structure in which an electrode assembly in which a negative electrode (400) including a negative electrode collector (401) and a negative electrode active material layer (403), a solid electrolyte layer (300), and a positive electrode (200) including a positive electrode active material layer (203) and a positive electrode collector (201) are laminated is housed in a case such as a pouch. The all-solid-state secondary battery (100) may further include an elastic layer (500) on the outer side of at least one of the positive electrode (200) and the negative electrode (400). Although Fig. 1 illustrates one electrode assembly including a negative electrode (400), a solid electrolyte layer (300), and a positive electrode (200), an all-solid-state battery may be manufactured by laminating two or more electrode assemblies.

[0107] cathode

[0108] An anode for an all-solid-state battery may include, for example, a current collector and a layer of anode active material positioned on the current collector. The layer of anode active material includes a cathode active material and may further include a binder, a conductive material, and / or a solid electrolyte.

[0109] The above negative active material may include a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

[0110] 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.

[0111] As the above lithium metal alloy, an alloy of lithium and one or more metals selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0112] As the material capable of doping and dedoping the lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used, and the Si-based negative electrode active material may be silicon, a silicon-carbon composite, or SiO. x(0<x<2), Si-Q 합금(상기 Q는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 15족 원소, 16족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Si은 아님), 상기 Sn계 음극 활물질로는 Sn, SnO2, Sn-R 합금(상기 R은 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 15족 원소, 16족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Sn은 아님) 등을 들 수 있고, 또한 이들 중 적어도 하나와 SiO2를 혼합하여 사용할 수도 있다. 상기 원소 Q 및 R로는 Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, 및 이들의 조합으로 이루어진 군에서 선택되는 것을 사용할 수 있다.

[0113] 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.

[0114] The average particle diameter (D50) of the above silicon particles may be 10 nm to 20 μm, for example, 10 nm to 500 nm. The silicon particles may exist in an oxidized form, and at this time, the atomic content ratio of Si:O in the silicon particles, which indicates the degree of oxidation, may be 99:1 to 33:67. The silicon particles may be SiO x It can be a particle, in which case SiO x In the range of x, it can be greater than 0 and less than 2. Here, the average particle diameter (D50) is measured by a particle size analyzer using laser diffraction and means the diameter of particles having a cumulative volume of 50% by volume in the particle size distribution.

[0115] The above Si-based negative electrode active material or Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material. The mixing ratio of the Si-based negative electrode active material or Sn-based negative electrode active material and the carbon-based negative electrode active material can be 1:99 to 90:10 by weight.

[0116] 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.

[0117] 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.

[0118] The above binder serves to adhere the negative active material particles well to each other and also to adhere the negative active material well to the current collector. The binder may include an insoluble binder, a water-soluble binder, or a combination thereof.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] The negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and a combination thereof.

[0124] 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.

[0125] FIG. 2 is a schematic cross-sectional view of an all-solid-state secondary battery including a precipitation-type negative electrode according to one embodiment. Referring to FIG. 2, the precipitation-type negative electrode (400') may include a current collector (401) and a negative electrode coating layer (405) positioned on the current collector. An all-solid-state battery including such a precipitation-type negative electrode (400') starts initial charging in a state in which no negative electrode active material is present, and upon charging, high-density lithium metal or the like is precipitated between the current collector (401) and the negative electrode coating layer (405) to form a lithium metal layer (404), which may function as a negative electrode active material. Accordingly, in an all-solid-state battery that has been charged at least once, the precipitation-type negative electrode (400') may include a current collector (401), a lithium metal layer (404) positioned on the current collector, and a negative electrode coating layer (405) positioned on the metal layer. The above lithium metal layer (404) refers to a layer in which lithium metal, etc. is precipitated during the charging process of the battery, and may be referred to as a metal layer or a negative electrode active material layer.

[0126] The above cathode coating layer (405) may include a metal, a carbon material, or a combination thereof that acts as a catalyst.

[0127] The metal may include, for example, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, zinc, or a combination thereof, and may be composed of one type of these or may be composed of an alloy of several types. When the metal is present in the form of particles, the average particle diameter (D50) thereof may be about 4 μm or less, for example, 10 nm to 4 μm.

[0128] 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.

[0129] When the above-described negative electrode coating layer (405) includes both the metal and the carbon material, the mixing ratio of the metal and the carbon material may be, for example, a weight ratio of 1:10 to 2:1. In this case, the precipitation of lithium metal can be effectively promoted and the characteristics of the all-solid-state battery can be improved. The above-described negative electrode coating layer (405) may include, for example, a carbon material supported with a catalytic metal, or may include a mixture of metal particles and carbon material particles.

[0130] The above cathode coating layer (405) may include, for example, the metal and amorphous carbon, in which case it can effectively promote the precipitation of lithium metal.

[0131] The above cathode coating layer (405) may further include a binder, and the binder may be a conductive binder. In addition, the above cathode coating layer (405) may further include general additives such as fillers, dispersants, and ionic conductive agents.

[0132] 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 ㎛.

[0133] The above-described precipitated negative electrode (400') may further include, for example, a thin film on the surface of the current collector, i.e., between the current collector and the negative electrode coating layer. The thin film may include an element capable of forming an alloy with lithium. The element capable of forming an alloy with lithium may be, for example, gold, silver, zinc, tin, indium, silicon, aluminum, bismuth, etc., and may be composed of one type thereof or may be composed of multiple types of alloys. The thin film may further flatten the precipitated form of the lithium metal layer (404) and further improve the characteristics of the all-solid-state battery. The thin film may be formed by, for example, a vacuum deposition method, a sputtering method, a plating method, etc. The thickness of the thin film may be, for example, 1 nm to 500 nm.

[0134] solid electrolyte layer

[0135] The solid electrolyte layer (300) may include a sulfide-based solid electrolyte, an oxide-based solid electrolyte, etc. The specific details of the sulfide-based solid electrolyte and the oxide-based solid electrolyte are as described above.

[0136] In one example, the solid electrolyte included in the positive electrode (200) and the solid electrolyte included in the solid electrolyte layer (300) may include the same compound or different compounds. For example, when both the positive electrode (200) and the solid electrolyte layer (300) include an argyrodite-type sulfide-based solid electrolyte, the overall performance of the all-solid-state secondary battery may be improved. In addition, for example, when both the positive electrode (200) and the solid electrolyte layer (300) include the above-described coated solid electrolyte, the all-solid-state secondary battery may implement high capacity and high energy density while implementing excellent initial efficiency and lifespan characteristics.

[0137] Meanwhile, the average particle diameter (D50) of the solid electrolyte included in the positive electrode (200) may be smaller than the average particle diameter (D50) of the solid electrolyte included in the solid electrolyte layer (300). In this case, the energy density of the all-solid-state battery can be maximized while increasing the mobility of lithium ions, thereby improving the overall performance. For example, the average particle diameter (D50) of the solid electrolyte included in the positive electrode (200) may be 0.1 ㎛ to 1.0 ㎛, or 0.1 ㎛ to 0.8 ㎛, and the average particle diameter (D50) of the solid electrolyte included in the solid electrolyte layer (300) may be 1.5 ㎛ to 5.0 ㎛, or 2.0 ㎛ to 4.0 ㎛, or 2.5 ㎛ to 3.5 ㎛. When this particle size range is satisfied, the energy density of the all-solid-state secondary battery can be maximized while lithium ion transport is facilitated, resistance is suppressed, and the overall performance of the all-solid-state secondary battery can be improved. Here, the average particle diameter (D50) of the solid electrolyte can be measured using a particle size analyzer using laser diffraction. Alternatively, the particle size can be measured by selecting 20 or so random particles from a microscope image such as a scanning electron microscope, obtaining a particle size distribution, and calculating the D50 value from this.

[0138] The above solid electrolyte layer may further include a binder in addition to the solid electrolyte. At this time, the binder may be styrene butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, an acrylate polymer, or a combination thereof, but is not limited thereto, and any binder used in the relevant technical field may be used. The acrylate polymer may be, for example, butyl acrylate, polyacrylate, polymethacrylate, or a combination thereof.

[0139] The above solid electrolyte layer can be formed by adding a solid electrolyte to a binder solution, coating the same on a base film, and drying the same. The solvent of the binder solution may be isobutyryl isobutyrate, xylene, toluene, benzene, hexane, or a combination thereof. Since the solid electrolyte layer formation process is widely known in the art, a detailed description thereof will be omitted.

[0140] The thickness of the solid electrolyte layer may be, for example, 10 ㎛ to 150 ㎛.

[0141] The above solid electrolyte layer may further include an alkali metal salt, and / or an ionic liquid, and / or a conductive polymer.

[0142] 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.

[0143] The above lithium salts include, for example, LiSCN, LiN(CN)2, Li(CF3SO2)3C, LiC4F9SO3, LiN(SO2CF2CF3)2, LiCl, LiF, LiBr, LiI, LiB(C2O4)2, LiBF4, LiBF3(C2F5), lithium bis(oxalato)borate (LiBOB), lithium oxalyldifluoroborate (LIODFB), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(trifluoro methanesulfonyl)imide (LiTFSI, LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide (LiFSI, It may include LiN(SO2F)2), LiCF3SO3, LiAsF6, LiSbF6, LiClO4 or mixtures thereof.

[0144] In addition, the lithium salt may be an imide-based one, and for example, the imide-based lithium salt may include lithium bis(trifluoro methanesulfonyl)imide (LiTFSI, LiN(SO2CF3)2), lithium bis(fluorosulfonyl)imide (LiFSI, LiN(SO2F)2). The lithium salt may maintain or improve ionic conductivity by appropriately maintaining chemical reactivity with an ionic liquid.

[0145] The above ionic liquid has a melting point below room temperature and is a salt or room-temperature molten salt that is liquid at room temperature and consists only of ions.

[0146] The above ionic liquid may be a compound including a) one or more cations selected from ammonium-based, pyrrolidinium-based, pyridinium-based, pyrimidinium-based, imidazolium-based, piperidinium-based, pyrazolium-based, oxazolium-based, pyridazinium-based, phosphonium-based, sulfonium-based, triazolium-based, and mixtures thereof, and b) one or more anions selected from BF4-, PF6-, AsF6-, SbF6-, AlCl4-, HSO4-, ClO4-, CH3SO3-, CF3CO2-, Cl-, Br-, I-, BF4-, SO4-, CF3SO3-, (FSO2)2N-, (C2F5SO2)2N-, (C2F5SO2)(CF3SO2)N-, and (CF3SO2)2N-.

[0147] 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.

[0148] In the above solid electrolyte layer, the weight ratio of the solid electrolyte and the ionic liquid may be 0.1:99.9 to 90:10, for example, 10:90 to 90:10, 20:80 to 90:10, 30:70 to 90:10, 40:60 to 90:10, or 50:50 to 90:10. A solid electrolyte layer satisfying the above range can maintain or improve ionic conductivity by improving the electrochemical contact area with the electrode. Accordingly, the energy density, discharge capacity, rate characteristics, etc. of the all-solid-state battery can be improved.

[0149] The above-mentioned all-solid-state battery may be a unit battery having a structure of positive electrode / solid electrolyte layer / negative electrode, a bi-cell having a structure of positive electrode / solid electrolyte layer / negative electrode / solid electrolyte layer / positive electrode, or a laminated battery in which the structure of the unit battery is repeated.

[0150] The shape of the above-mentioned all-solid-state battery is not particularly limited, and may be, for example, coin-shaped, button-shaped, sheet-shaped, stacked, cylindrical, flat, etc. In addition, the above-mentioned all-solid-state battery can be applied to large-scale batteries used in electric vehicles, etc. For example, the above-mentioned all-solid-state battery can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it can be used in fields requiring large amounts of power storage, and for example, it can be used in electric bicycles or power tools.

[0151] One example is an all-solid-state secondary battery using a sulfide-based solid electrolyte. Because solid electrolytes cannot be used in an exposed state, they require isolation from the atmosphere. To achieve this, the all-solid-state secondary battery is manufactured by enclosing it in an outer body made of a laminate film or other rigid material.

[0152] However, since the cathode, solid electrolyte layer, anode, and elastic sheet are laminated on the laminate film, the alignment of the laminated elastic sheets may be misaligned during the vacuum process during sealing. In addition, the presence of air bubbles during lamination may make it difficult to provide uniform pressure to the cathode / solid electrolyte layer / anode.

[0153] When an all-solid-state secondary battery is not uniformly pressurized from the outside during discharge, the movement speed of lithium ions may decrease, which may lower the discharge efficiency. In addition, when pressurization is applied locally, lithium ions may move to the pressurized area, which may lower the discharge efficiency.

[0154] One embodiment enhances Coulombic efficiency even when the thickness of the negative electrode fluctuates due to charging and discharging. To this end, one embodiment is configured to eliminate bubble formation between the laminated structure of the negative electrode, the solid electrolyte layer, and the positive electrode, and the elastic sheet. Furthermore, one embodiment is configured to eliminate bubble formation between unit cells when stacking multiple unit cells.

[0155] Fig. 3 is a cross-sectional view illustrating an all-solid-state secondary battery according to a first embodiment of the present invention. Referring to Fig. 3, the all-solid-state secondary battery of the first embodiment includes unit cells (10) and ceramic insulating layers (20). The unit cells (10) are formed by stacking a negative electrode (30), a solid electrolyte layer (40), and a positive electrode (50). The all-solid-state secondary battery of Fig. 3 is formed in a bi-cell structure.

[0156] Each of the unit cells (10) is formed by having a positive electrode (50) in the middle of the stacking direction, a solid electrolyte layer (40) on the upper and lower sides of the positive electrode (50), and a negative electrode (30) on the solid electrolyte layer (40). The positive electrode (50) includes a positive electrode current collector (51) and a positive electrode active material layer (52) laminated on both sides thereof. The negative electrode (30) includes a negative electrode current collector (31) and a negative electrode active material layer laminated on one surface thereof.

[0157] Accordingly, each of the unit cells (10) is formed by sequentially stacking a positive electrode current collector (51) in the middle of the stacking direction, and a positive electrode active material layer (52), a solid electrolyte layer (40), a negative electrode active material layer, and a negative electrode current collector (31) on each of the two sides.

[0158] As illustrated in Fig. 3, when the negative electrode (30) is a precipitation-type negative electrode, it may include a negative electrode coating layer (33) positioned on the negative electrode current collector (31). Initial charging begins in a state in which no negative electrode active material is present, and during charging, high-density lithium metal or the like is precipitated between the negative electrode current collector (31) and the negative electrode coating layer (33) to form a lithium metal layer (34), which can serve as a negative electrode active material layer.

[0159] Accordingly, in an all-solid-state battery that has been charged more than once, the precipitation-type negative electrode (30) may include a negative electrode current collector (31), a lithium metal layer (34) positioned on the negative electrode current collector (31), and a negative electrode coating layer (33) positioned on the lithium metal layer (34). The lithium metal layer (34) 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.

[0160] The unit cells (10) are stacked in the direction of stacking the cathode (30), the solid electrolyte layer (40), and the anode (50). The unit cells (10) are formed in at least two units and are arranged adjacent to each other.

[0161] Ceramic insulating layers (20) are arranged between the negative electrodes (30) of adjacent unit cells (10) and are laminated on the negative electrodes (30) located on the outermost sides of the unit cells (10). For example, a first cell (101) among the adjacent unit cells (10) includes a positive electrode active material layer (52), a solid electrolyte layer (40), a lithium metal layer (34) acting as a negative electrode active material layer, and a negative electrode collector (31) sequentially laminated on each of both sides of a positive electrode current collector (51).

[0162] The second cell (102) adjacent to the first cell (101) includes a positive electrode active material layer (52), a solid electrolyte layer (40), a lithium metal layer (34) acting as a negative electrode active material layer, and a negative electrode current collector (31) sequentially laminated on each side of the positive electrode current collector (51). At this time, among the ceramic insulating layers (20), the ceramic insulating layer (20) located between the first cell (101) and the second cell (102) is arranged as a single layer between a pair of negative electrode current collectors (31, 31).

[0163] Ceramic insulating layers (20) are provided on the opposite side of the solid electrolyte layer (40) of the negative electrode (30). When the all-solid-state secondary battery is damaged by an external force, for example, penetration or collision, the positive electrode (50) and the negative electrode (30) may be electrically short-circuited. At this time, the ceramic insulating layer (20) protects the unit cells (10) as a functional layer at the outermost part of the unit cells (10), thereby reducing the heat generation of the unit cells (10).

[0164] When forming an all-solid-state secondary battery by stacking a plurality of unit cells (10), a ceramic insulating layer (20) is arranged between the unit cells (10), thereby preventing the positive electrodes (50) and negative electrodes (30) of adjacent unit cells (10) from directly contacting each other beyond each unit cell (10). As a result, thermal runaway due to collapse of the lithium metal layer (34) acting as the positive electrode active material layer (52) and the negative electrode active material layer can be prevented.

[0165] The ceramic insulating layer (20) can prevent direct short circuit between the anode (50) and cathode (30) when the cell is damaged by external impact, thereby reducing the amount of heat generated due to the short circuit. For example, the ceramic insulating layer (20) is formed by including ceramic particles and a binder. For example, the ceramic particles may be alumina or boehmite.

[0166] In the ceramic insulating layer (20), ceramic particles provide insulation to prevent short circuit between the anode (50) and cathode (30).

[0167] Below, the results of the first to fourth experimental examples and the first comparative example, which confirmed the ratio of binder to ceramic particles forming the ceramic insulating layer (20) and the short-circuit resistance ratio indicating the resulting insulation, are as shown in Table 1.

[0168] Ceramic insulation layerCeramic insulation layer thicknessCeramic particle size (D50)Binder ratioShort circuit resistance ratioFirst comparative preliminary application---1First experimental example Application10㎛2㎛5Wt%123.58Second experimental example Application10㎛3㎛5Wt%133.77Third experimental example Application20㎛2㎛5Wt%658.65Fourth experimental example Application10㎛2㎛10.0Wt%137.3

[0169] As can be seen from the first to third experimental examples, the short-circuit resistance ratio indicating the insulation property is most greatly affected by the thickness of the ceramic insulating layer (20). The thickness of the ceramic insulating layer (20) can be compared by comparing the first and third experimental examples. The thickness of the ceramic insulating layer (20) can be implemented between a minimum of 5 ㎛ and 50 ㎛. If the thickness is less than a minimum of 5 ㎛, a meaningful short-circuit resistance ratio cannot be obtained due to insufficient insulation. If the thickness exceeds a minimum of 50 ㎛, ceramic particles and binder are used excessively compared to securing additional insulation property.

[0170] The thicknesses of Experimental Examples 1 to 4 range from 10 μm to 20 μm. The thickness range of 10 μm to 20 μm allows for an appropriate short-circuit resistance ratio to be achieved with an appropriate amount of ceramic particles and binder. Compared to Comparative Example 1, which did not apply a ceramic insulating layer, Experimental Examples 1 to 4 have significantly higher short-circuit resistance ratios.

[0171] As an example, the ceramic insulating layer (20) includes 5 to 10 wt% of binder and 90 to 95 wt% of ceramic particles. The thickness of the ceramic insulating layer (20) can be compared by comparing the first and third experimental examples. It can be seen that the short-circuit resistance ratio increases as the ceramic insulating layer (20) becomes thicker.

[0172] In addition, looking at Experimental Examples 1 to 3, it can be seen that the thicker the ceramic insulating layer (20), the greater the short-circuit resistance ratio. When the binder ratio was 5 to 10 wt%, it did not have a significant effect on the experiment.

[0173] Figure 5 is a graph showing the temperature relationship over time during nail penetration of an all-solid-state secondary battery. Referring to Figure 5, the third experimental example applying a ceramic insulating layer (20) exhibits excellent penetration characteristics, as the temperature does not rise during nail penetration, compared to the first comparative example not applying a ceramic insulating layer. The penetration evaluation conditions for temperature are room temperature, a nail pin diameter of 3 mm, and a nail penetration speed of 50 mm / sec.

[0174] Figure 6 is a graph showing the voltage relationship over time during nail penetration of an all-solid-state secondary battery. Referring to Figure 6, the third experimental example applying a ceramic insulating layer (20) exhibits superior penetration characteristics, recovering and maintaining a voltage level slightly lower than before nail penetration, compared to the first comparative example not applying a ceramic insulating layer. The penetration evaluation conditions for voltage are room temperature, a nail pin diameter of 3 mm, and a nail penetration speed of 50 mm / sec.

[0175] In this way, when the ceramic insulating layer (20) is applied, the short-circuit resistance ratio increases, which means that safety is improved. In other words, when the short-circuit resistance ratio increases, penetration performance and impact performance are improved.

[0176] Fig. 4 is a cross-sectional view showing an all-solid-state secondary battery according to a second embodiment of the present invention. Referring to Fig. 4, each of the unit cells (210) is formed by including a solid electrolyte layer (240) on one side of a positive electrode (250) and an anode (230) on the solid electrolyte layer (240). The positive electrode (250) includes a positive electrode current collector (251) and a positive electrode active material layer (252) laminated on one surface thereof. The negative electrode (230) includes a negative electrode current collector (231) and a lithium metal layer (234) laminated on one surface thereof and acting as a negative electrode active material layer.

[0177] Accordingly, each of the unit cells (210) is formed by sequentially laminating a positive electrode active material layer (252), a solid electrolyte layer (240), a negative electrode coating layer (233), a lithium metal layer (234) that acts as a negative electrode active material layer and also forms lithium metal precipitation during charging, and a negative electrode current collector (231) on one surface of a positive electrode current collector (251).

[0178] The unit cells (210) are stacked in the direction of stacking the cathode (230), the solid electrolyte layer (240), and the anode (250). At least two unit cells (210) are formed and arranged adjacent to each other.

[0179] Ceramic insulating layers (220) are arranged between the positive electrodes (250) and negative electrodes (230) of the adjacent unit cells (210), and are laminated on the negative electrodes (230) located on the outermost sides of the unit cells (210). For example, among the adjacent unit cells (210), the first cell (211) includes a positive electrode active material layer (252), a solid electrolyte layer (240), a negative electrode coating layer (233), a lithium metal layer (234) acting as a negative electrode active material layer, and a negative electrode current collector (231) sequentially laminated on one surface of a positive electrode current collector (251).

[0180] The second cell (212) adjacent to the first cell (211) includes a positive electrode active material layer (252), a solid electrolyte layer (240), a negative electrode coating layer (233), a lithium metal layer (234) acting as a negative electrode active material layer, and a negative electrode current collector (231) sequentially laminated on one surface of a positive electrode current collector (251). At this time, among the ceramic insulating layers (220), the ceramic insulating layer (220) positioned between the positive electrode current collector (251) of the first cell (211) and the negative electrode current collector (231) of the second cell (212) is arranged as a single layer.

[0181] Ceramic insulating layers (220) are provided on the side opposite the solid electrolyte layer (40) of the outermost cathode (230) and on the side opposite the solid electrolyte layer (40) of the anode (250). When the all-solid-state secondary battery is damaged by an external force, for example, penetration or collision, the cathode (250) and the anode (230) may be electrically short-circuited. At this time, the ceramic insulating layer (220) protects the unit cells (210) as a functional layer at the outermost part of the unit cells (210), thereby reducing the heat generation of the unit cells (210).

[0182] When forming an all-solid-state secondary battery by stacking a plurality of unit cells (210), a ceramic insulating layer (220) is arranged between the unit cells (210), thereby preventing the positive electrodes (250) and negative electrodes (230) of neighboring unit cells (210) beyond each unit cell (210) from directly contacting each other. As a result, thermal runaway due to collapse of the lithium metal layer (234) acting as the positive electrode active material layer (252) and the negative electrode active material layer can be prevented.

[0183] The ceramic insulating layer (220) can effectively lower the temperature of the unit cells (210) by helping to dissipate heat when heat is generated in the unit cells (210). For example, the ceramic insulating layer (220) is formed by including ceramic particles and a binder. For example, the ceramic particles may be alumina or boehmite.

[0184] In the ceramic insulating layer (220), ceramic particles provide insulation to prevent short circuits between the anode (250) and cathode (230). The ceramic insulating layer (220) can prevent direct short circuits between the anode (250) and cathode (230) when the cell is damaged by external impact, thereby reducing the amount of heat generated due to the short circuit.

[0185] Fig. 7 is a cross-sectional view illustrating an all-solid-state secondary battery according to a third embodiment of the present invention. Referring to Fig. 7, the all-solid-state secondary battery of one embodiment includes a laminate (110) and ceramic insulating layers (120). The laminate (110) is formed by laminating a negative electrode (130), a solid electrolyte layer (140), and a positive electrode (150). The all-solid-state secondary battery of Fig. 7 is formed in a bi-cell structure.

[0186] The laminate (110) is formed by having a positive electrode (150) in the middle of the stacking direction, a solid electrolyte layer (140) on the upper and lower sides of the positive electrode (150), and a negative electrode (130) on the solid electrolyte layer (140). The positive electrode (150) includes a positive electrode current collector (151) and a positive electrode active material layer (152) laminated on both sides thereof. The negative electrode (130) includes a negative electrode current collector (131) and a negative electrode active material layer laminated on one surface thereof.

[0187] Therefore, the laminate (110) is formed by sequentially laminating a positive electrode current collector (150) in the middle of the lamination direction, and a positive electrode active material layer (152), a solid electrolyte layer (140), a negative electrode active material layer, and a negative electrode current collector (131) on each of its two sides.

[0188] As illustrated in Fig. 7, when the negative electrode (130) is a precipitation-type negative electrode, it may include a negative electrode coating layer (133) positioned on the negative electrode current collector (131). Initial charging begins in a state in which no negative electrode active material is present, and during charging, high-density lithium metal or the like is precipitated between the negative electrode current collector (131) and the negative electrode coating layer (133) to form a lithium metal layer (134), which may function as a negative electrode active material layer.

[0189] Accordingly, in an all-solid-state battery that has been charged more than once, the precipitated negative electrode (130) may include a negative electrode current collector (131), a lithium metal layer (134) positioned on the negative electrode current collector (131), and a negative electrode coating layer (133) positioned on the lithium metal layer (134). The lithium metal layer (134) 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.

[0190] Ceramic insulating layers (120) are laminated on both outermost sides of the laminate (110). The ceramic insulating layers (120) are provided on the opposite side of the solid electrolyte layer (140) of the negative electrode (130). When the all-solid-state secondary battery is damaged by an external force, for example, penetration by a through pin (P) (see FIG. 8) or collision, the positive electrode (150) and the negative electrode (130) may be electrically short-circuited. At this time, the ceramic insulating layers (120) protect the laminate (110) as a functional layer at the outermost side of the laminate (110), thereby reducing the heat generation of the laminate (110).

[0191] The ceramic insulating layers (120) can effectively lower the temperature of the laminate (110) by helping to dissipate heat when heat is generated in the laminate (110). For example, the ceramic insulating layers (120) are formed by including a conductive material, a ceramic material, and a binder. For example, the ceramic material may be alumina or boehmite.

[0192] In the ceramic insulating layers (120), the ceramic material provides insulation to prevent short circuits between the anode (150) and cathode (130), and the conductive material provides thermal conductivity to help dissipate heat, thereby preventing thermal runaway. In addition, the ceramic insulating layers (120) protect the cathode current collector (131) from gases generated within the laminate (110), and minimize pores and gas permeability due to rolling.

[0193] Below, the results of the 11th to 14th experimental examples and the second comparative example, which confirmed the insulation, thermal conductivity, and heat dissipation according to the composition ratio of the conductive material and ceramic material forming the ceramic insulating layers (120), are as shown in Table 2. The penetration experiment was conducted at room temperature, the diameter of the penetration pin (P) was 3 mm, and the penetration speed of the penetration pin (P) was 50 mm / sec.

[0194] When evaluating penetration, there are some differences between the cells of the all-solid-state battery, but the all-solid-state battery reaches the maximum temperature within 20 seconds immediately after penetration. Since the temperature difference is the largest when the maximum temperature is reached, Experimental Examples 11 to 14 and Comparative Example 2 measured the temperature within 30 seconds immediately after penetration of the all-solid-state battery, thereby obtaining the temperature difference ratio between the central and peripheral regions and the maximum temperature ratio in the central region.

[0195] Ceramic insulation layerCeramic insulation layer thicknessConductive material ratioBinder ratioCentral and periphery temperature difference ratioCentral maximum temperature ratioSecond comparative preliminary application---100%100%11th experimental example application5㎛-5wt%39%35%12th experimental example application5㎛5wt%5wt%11%16%13th experimental example application5㎛5wt%10wt%12%16%14th experimental example application5㎛10wt%5wt%9%15%

[0196] As can be seen in the second comparative example and the 11th to 14th experimental examples, it can be seen that the ceramic insulating layer (120) has a great influence on the thermal conductivity and heat dissipation in the laminate of the second comparative example without applying the ceramic insulating layer (120) and the laminate (110) of the 11th to 14th experimental examples with applying the ceramic insulating layer (120). That is, the ceramic insulating layer (120) has a great influence on the temperature difference ratio between the central part (P1) and the peripheral part (P2) that exhibit thermal conductivity and heat dissipation, and the central part maximum temperature ratio. In addition, as can be seen in the 11th to 14th experimental examples, it can be seen that the conductive material has a great influence on the thermal conductivity and heat dissipation in the laminate of the 11th experimental example without applying the conductive material and the laminate (110) of the 12th to 14th experimental examples with applying the conductive material. In other words, the ratio of the temperature difference between the central part (P1) and the peripheral part (P2), which exhibit thermal conductivity and heat dissipation, and the ratio of the maximum temperature in the central part have the greatest influence on the ratio of the conductive material.

[0197] A comparison of the proportion of the conductive material in the ceramic insulating layer (120) can be obtained by comparing Experimental Example 12 and Experimental Example 14. As an example, the conductive material in the ceramic insulating layer (120) can be implemented in an amount between 0.1 and 30 wt%.

[0198] When the ceramic content is less than 30 wt%, the electrical insulation performance of the ceramic insulating layer (120) may deteriorate due to the lack of ceramic. When the ceramic content is more than 95 wt%, the heat dissipation and thermal conductivity performance may deteriorate due to the excessive ceramic content, resulting in the lack of conductive material in the ceramic insulating layer (120).

[0199] When the content of the conductive material is less than 0.1 wt%, the content of the conductive material is insufficient, and thus the ceramic insulating layer (120) cannot sufficiently provide heat dissipation and thermal conductivity performance. When the content of the conductive material exceeds 30 wt%, the electrical insulation performance of the ceramic insulating layer (120) may be deteriorated due to the excessive content of the conductive material.

[0200] When the binder content is less than 1 wt%, the bonding performance between the ceramic particles and the conductive material particles in the ceramic insulating layer (120) may deteriorate due to a lack of binder. When the binder content exceeds 40 wt%, the heat dissipation and thermal conductivity performance of the conductive material in the ceramic insulating layer (120) may deteriorate due to an excess of binder.

[0201] In Experimental Example 12, the ceramic insulating layer includes 90 wt% of ceramic, 5 wt% of conductive material, and 5 wt% of binder. In Experimental Example 13, the ceramic insulating layer includes 85 wt% of ceramic, 5 wt% of conductive material, and 10 wt% of binder. In Experimental Example 14, the ceramic insulating layer includes 85 wt% of ceramic, 10 wt% of conductive material, and 5 wt% of binder. That is, referring to Experimental Examples 12 to 14, the ceramic insulating layer may include 80 to 90 wt% of ceramic, 5 to 10 wt% of conductive material, and 5 to 10 wt% of binder.

[0202] Fig. 8 is a plan view showing the position where the through pin penetrates the laminate during the penetration experiment in the 11th to 14th experimental examples of the present invention and the second comparative example. Referring to Fig. 8, during the penetration experiment of the through pin (P), the temperature measurement area in the laminate includes the central portion (P1) where the through pin (P) is inserted and the peripheral portion (P2) at least 30 mm away from the through pin (P). The difference in heat dissipation characteristics, i.e., the difference in thermal conductivity characteristics, can be compared by the temperature difference between the central portion (P1) and the peripheral portion (P2).

[0203] As disclosed in Table 2, the difference in thermal conductivity characteristics can be expressed as the temperature difference ratio between the central portion (P1) and the peripheral portion (P2) and the central portion maximum temperature ratio. In the second comparative example, the temperature difference ratio between the central portion (P1) and the peripheral portion (P2) is 100%, and the central portion maximum temperature ratio is 100%. In contrast, in the eleventh experimental example, the temperature difference ratio between the central portion (P1) and the peripheral portion (P2) is 39%, and the central portion maximum temperature ratio is 35%.

[0204] In the second comparative example, since there is no ceramic insulating layer, the temperature of the central part (P1) is very high, and since the heat dissipation characteristics, i.e. the thermal conductivity characteristics, are low, the temperature difference ratio between the central part (P1) and the peripheral part (P2) is very large.

[0205] In contrast, Experimental Example 11 applied a ceramic insulating layer without a conductive material, so the electrical short circuit was partially prevented by the ceramic insulating layer, thereby reducing the amount of heat generated. Accordingly, the maximum temperature of the central portion (P1) was reduced by approximately 35% compared to the maximum temperature of the central portion (P1) of Comparative Example 2.

[0206] Fig. 9 is a graph showing the temperature change over time in the central and peripheral portions through which the through pin penetrates in the 11th and 12th experimental examples of Fig. 7. Referring to Fig. 9, since there is no conductive material in the ceramic insulating layer when the through pin (P) penetrates, it is difficult for the generated heat to dissipate to the outside, and it is also difficult for the heat to be transferred in the horizontal direction, that is, from the central portion (P1) to the peripheral portion (P2). Therefore, the heat generated locally in the central portion (P1) remains in the central portion (P1), resulting in a relatively high temperature compared to the 12th to 14th experimental examples. The 11th experimental example has lower heat dissipation and heat transfer performance than the 12th to 14th experimental examples.

[0207] In Experimental Example 12, since a conductive material was applied to the ceramic insulating layer (120), the heat generated when the penetration of the through pin (P) begins is dissipated to the outside through the conductive material, so that the maximum temperature of the central portion (P1) is relatively lower than that of Experimental Example 11. That is, in Experimental Example 12, it can be observed that the slope of the temperature rise is gradually increased due to heat dissipation and heat transfer in the horizontal direction.

[0208] In the 11th experimental example, the temperature difference between the central part (P1) and the peripheral part (P2) of the penetration of the through pin (P) is large, and in contrast, in the 12th experimental example, the temperature difference between the central part (P1) and the peripheral part (P2) of the penetration of the through pin (P) is small. Therefore, the effect of the conductive material in the ceramic insulating layer (120) can be confirmed.

[0209] The above description is only one embodiment for implementing the all-solid-state secondary battery according to the present disclosure, and the present disclosure is not limited to the above-described embodiment, and as claimed in the following claims, it will be understood that the technical spirit of the present disclosure encompasses a range in which various modifications can be implemented without departing from the gist of the present disclosure by anyone having ordinary skill in the art to which the invention pertains.

[0210] (Explanation of symbols)

[0211] 10, 210: Unit cell 20, 220: Ceramic insulating layer

[0212] 30, 230: Cathode 31, 231: Cathode current collector

[0213] 33, 233: Cathode coating layer 34, 234: Lithium metal layer

[0214] 40, 240: Solid electrolyte layer 50, 250: Anode

[0215] 51, 251: positive electrode current collector 52, 252: positive electrode active material layer

[0216] 110: Laminate 120: Ceramic insulating layer

[0217] 130: Cathode 131: Cathode current collector

[0218] 133: Cathode coating layer 134: Lithium metal layer

[0219] 140: Solid electrolyte layer 150: Anode

[0220] 151: Cathode current collector 152: Cathode active material layer

[0221] P: Through pin P1: Center

[0222] P2: Periphery

Claims

1. Unit cells formed by stacking a cathode, a solid electrolyte layer, and an anode, and provided in multiple numbers; and Ceramic insulating layers provided on the cathodes located at least between the cathodes of neighboring unit cells and at the outermost portion of all the unit cells An all-solid-state secondary battery comprising:

2. In paragraph 1, Each of the above unit cells is The positive electrode current collector located in the middle, and An all-solid-state secondary battery comprising a positive electrode active material layer sequentially laminated on each side of a positive electrode current collector forming the positive electrode, the solid electrolyte layer, a negative electrode active material layer forming the negative electrode, and a negative electrode current collector.

3. In paragraph 2, The above ceramic insulating layers An all-solid-state secondary battery provided on the outer surface of the above-mentioned negative electrode collector.

4. In paragraph 2 Among the above neighboring unit cells, the first cell is It includes the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode collector, which are sequentially laminated on each of both sides of the positive electrode collector, The second cell adjacent to the first cell above is It includes the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode collector, which are sequentially laminated on each of both sides of the positive electrode collector, Among the above ceramic insulating layers, the ceramic insulating layer located between the first cell and the second cell An all-solid-state secondary battery, wherein the cathode current collector is arranged in a single layer between a pair of the above-described cathode current collectors.

5. In paragraph 1, The above ceramic insulating layer An all-solid-state secondary battery comprising at least one of alumina and boehmite and a binder.

6. In paragraph 1, An all-solid-state secondary battery comprising the ceramic insulating layer, 5 to 10 wt% of a binder, and 90 to 95 wt% of ceramic particles.

7. In paragraph 1, An all-solid-state secondary battery having a thickness of the ceramic insulating layer of 5 μm to 50 μm.

8. In paragraph 1, Each of the above unit cells is An all-solid-state secondary battery comprising a positive electrode active material layer sequentially laminated on one side of a positive electrode current collector forming the positive electrode, the solid electrolyte layer, a negative electrode active material layer forming the negative electrode, and a negative electrode current collector.

9. In paragraph 8 Among the above neighboring unit cells, the first cell is It includes the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode collector sequentially laminated on one side of the positive electrode current collector, The second cell adjacent to the first cell above is It includes the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode collector sequentially laminated on one side of the positive electrode collector, Among the above ceramic insulating layers, the ceramic insulating layer located between the positive electrode collector of the first cell and the negative electrode collector of the second cell All-solid-state secondary batteries placed on the first floor.

10. A laminate formed by laminating a cathode, a solid electrolyte layer, and an anode; and A ceramic insulating layer including a conductive material provided on the opposite side of the solid electrolyte layer of the cathode located at the outermost part of the laminate An all-solid-state secondary battery comprising:

11. In paragraph 10, The above laminate The positive electrode current collector located in the middle, and An all-solid-state secondary battery comprising a positive electrode active material layer sequentially laminated on each side of the positive electrode current collector forming the positive electrode, the solid electrolyte layer, a negative electrode active material layer forming the negative electrode, and a negative electrode current collector.

12. In paragraph 10, An all-solid-state secondary battery, wherein the ceramic insulating layer comprises 30 to 95 wt% of ceramic, 0.1 to 30 wt% of conductive material, and 1 to 40 wt% of binder.

13. In paragraph 10, An all-solid-state secondary battery, wherein the ceramic insulating layer comprises 80 to 90 wt% of ceramic, 5 to 10 wt% of conductive material, and 5 to 10 wt% of binder.

14. In paragraph 10, When testing the penetration of the through pin, the temperature measurement area in the laminate is The central part into which the above-mentioned through pin is inserted, and Including the periphery at least 30 mm away from the above-mentioned through pin, An all-solid-state secondary battery, which compares heat dissipation characteristics based on the temperature difference ratio between the central portion and the peripheral portion.

15. In paragraph 14, An all-solid-state secondary battery having a temperature difference ratio between the central portion and the peripheral portion of 9 to 39%.

16. In paragraph 14, An all-solid-state secondary battery having a temperature difference ratio between the central portion and the peripheral portion of 9 to 12%.

17. In paragraph 14, An all-solid-state secondary battery having a maximum temperature ratio of 15 to 35% in the central portion.

18. In paragraph 14, An all-solid-state secondary battery having a maximum temperature ratio of 15 to 16% in the central portion.

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