All-solid-state battery comprising bilayer solid electrolyte and method of manufacturing same

Abstract

The present invention provides an all-solid-state battery including a bilayer solid electrolyte and a method for manufacturing the same, the all-solid-state battery being capable of improving robustness of an electrolyte layer while suppressing a thermal runaway phenomenon and exhibiting excellent electrochemical characteristics. The all-solid-state battery includes a negative electrode; a first solid electrolyte layer on the negative electrode; a second solid electrolyte layer on the first solid electrolyte layer; and a positive electrode on the second solid electrolyte layer. The first solid electrolyte layer contains an inorganic flame retardant, and the second solid electrolyte layer contains an endothermic flame retardant.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0154681, filed with the Korean Intellectual Property Office on November 4, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to an all-solid-state battery comprising a double-layer solid electrolyte and a method for manufacturing the same, which improves the robustness of the electrolyte layer while suppressing thermal runaway. Background Technology

[0004] Lithium-ion batteries are widely used in various fields, such as electric vehicles and portable electronic devices, but some safety issues remain. Specifically, to improve energy density, cathode materials with high nickel (Ni) content are primarily used. However, this lowers the pyrolysis initiation temperature, increases heat generation, and thus increases the risk of thermal runaway. Furthermore, silicon (Si) anodes are also used to increase theoretical capacity. Silicon anodes undergo significant volume expansion during charging / discharging, and prolonged charging / discharging can lead to lithium metal deposition, causing internal short circuits and triggering thermal runaway.

[0005] Therefore, all-solid-state batteries have attracted significant attention as next-generation energy storage devices because they employ a solid electrolyte, unlike existing lithium-ion batteries, which can reduce the risk of electrolyte leakage or fire. However, all-solid-state batteries also present safety challenges, such as thermal runaway. In particular, due to the multi-layered structure of all-solid-state batteries, maintaining thermal and mechanical stability between the positive and negative electrodes is difficult. Therefore, there is a need to develop an all-solid-state battery that can maintain energy density and performance while ensuring thermal and mechanical stability. Summary of the Invention

[0006] The present invention aims to solve the above-mentioned problems existing in the prior art, while fully retaining the advantages achieved by the prior art.

[0007] One aspect of the present invention relates to an all-solid-state battery comprising a bilayer solid electrolyte and a method thereof, the battery being able to improve the robustness of the electrolyte layer while suppressing thermal runaway.

[0008] More specifically, the present invention aims to improve the robustness of the electrolyte layer by using a first solid electrolyte layer containing an inorganic flame retardant, and to reduce the heating initiation temperature by using a second solid electrolyte layer containing an endothermic flame retardant, thereby suppressing thermal runaway.

[0009] The technical problems to be solved by the present invention are not limited to those described above. Those skilled in the art will clearly understand from the following description any other technical problems not mentioned herein.

[0010] According to one aspect of the present invention, an all-solid-state battery comprising a double-layer solid electrolyte and a method thereof is provided.

[0011] More specifically, (1) the present invention provides an all-solid-state battery, comprising: a negative electrode; a first solid electrolyte layer located on the negative electrode; a second solid electrolyte layer located on the first solid electrolyte layer; and a positive electrode located on the second solid electrolyte layer. The first solid electrolyte layer contains an inorganic flame retardant, and the second solid electrolyte layer contains an endothermic flame retardant.

[0012] (2) The present invention provides an all-solid-state battery as in (1), wherein the inorganic flame retardant includes at least one selected from LLZO, LATP, SiO2, ZnO, SnO2, Mn3O4, Sn2P2O7, aluminum oxide, magnesium oxide, zeolite, zirconium compounds, calcium salts and boron compounds.

[0013] (3) The present invention provides an all-solid-state battery as in (1) or (2), wherein the first solid electrolyte layer contains an inorganic flame retardant content in the range of 20 wt% to 50 wt% based on the weight of the solid electrolyte contained in the first solid electrolyte layer.

[0014] (4) The present invention provides an all-solid-state battery as described in any one of (1) to (3), wherein the heat-absorbing flame retardant comprises at least one selected from Mg(OH)2, Al(OH)3, Sb2O3, H3BO3, Fe(OH)3, CaCO3, Ca(OH)2, Zn(OH)2, NaOH, calcium magnesium hydroxide, hydrotalcite, boehmite, talc, sodium aluminum oxide, calcium sulfate hydrate and magnesium sulfate hydrate.

[0015] (5) The present invention provides an all-solid-state battery as described in any one of (1) to (4), wherein the content of the heat-absorbing flame retardant in the second solid electrolyte layer is in the range of 5 wt% to 20 wt% based on the weight of the solid electrolyte contained in the second solid electrolyte layer.

[0016] (6) The present invention provides an all-solid-state battery as described in any one of (1) to (5), wherein the ratio of the thickness of the first solid electrolyte layer to the thickness of the second solid electrolyte layer is 1:9 to 9:1.

[0017] (7) The present invention provides an all-solid-state battery as described in any one of (1) to (6), wherein the sum of the thickness of the first solid electrolyte layer and the thickness of the second solid electrolyte layer is 10 μm to 120 μm.

[0018] (8) The present invention provides an all-solid-state battery as described in any one of (1) to (7), wherein the first solid electrolyte layer and the second solid electrolyte layer each further comprise an adhesive.

[0019] (9) The present invention provides an all-solid-state battery as in (8), wherein the content of binder is in the range of 0.5 wt% to 5 wt% based on the weight of the solid electrolyte of the first solid electrolyte layer and the second solid electrolyte layer, respectively.

[0020] (10) The present invention provides an all-solid-state battery as in (8) or (9), wherein the adhesive comprises at least one selected from polybutadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), polyimide (PI), polyvinylidene fluoride (PVDF) and ethylene propylene diene monomer (EPDM).

[0021] (11) The present invention provides a method for manufacturing an all-solid-state battery, the method comprising the following steps: manufacturing an all-solid-state battery, wherein a negative electrode, a first solid electrolyte layer, a second solid electrolyte layer and a positive electrode are stacked in sequence (S0), wherein the first solid electrolyte layer contains an inorganic flame retardant and the second solid electrolyte layer contains a heat-absorbing flame retardant.

[0022] (12) The present invention provides a method for manufacturing an all-solid-state battery as in (11), wherein the steps of manufacturing an all-solid-state battery include: manufacturing a negative electrode assembly by sequentially stacking a negative electrode, a first solid electrolyte layer and a second solid electrolyte layer; and stacking the negative electrode assembly and a positive electrode such that the second solid electrolyte layer faces the positive electrode.

[0023] (13) The present invention provides a method for manufacturing an all-solid-state battery as in (12), wherein the negative electrode assembly is manufactured using a wet-on-wet or wet-on-dry method.

[0024] (14) The present invention provides a method for manufacturing an all-solid-state battery as in (11), wherein the steps of manufacturing an all-solid-state battery include: manufacturing a positive electrode assembly by sequentially stacking a positive electrode, a second solid electrolyte layer and a first solid electrolyte layer; and stacking the positive electrode assembly and a negative electrode such that the first solid electrolyte layer faces the negative electrode.

[0025] (15) The present invention provides a method for manufacturing an all-solid-state battery as in (14), wherein the positive electrode assembly is manufactured by a wet-on-wet or wet-on-dry scheme.

[0026] (16) The present invention provides a method for manufacturing an all-solid-state battery as in (11), wherein the steps of manufacturing an all-solid-state battery include: manufacturing a negative electrode assembly including a negative electrode and a first solid electrolyte layer; manufacturing a positive electrode assembly including a positive electrode and a second solid electrolyte layer; and stacking the negative electrode assembly and the positive electrode assembly such that the first solid electrolyte layer and the second solid electrolyte layer face each other.

[0027] (17) The present invention provides a method for manufacturing an all-solid-state battery as in (16), wherein the negative electrode assembly or the positive electrode assembly is each manufactured by a wet-on-wet or wet-on-dry scheme.

[0028] (18) The present invention provides an all-solid-state battery, comprising: a negative electrode; a first solid electrolyte layer located on the negative electrode; a second solid electrolyte layer located on the first solid electrolyte layer; and a positive electrode located on the second solid electrolyte layer, wherein the first solid electrolyte layer comprises at least one component selected from LLZO, LATP, SiO2, ZnO, SnO2, Mn3O4, Sn2P2O7, aluminum oxide, magnesium oxide, zeolite, zirconium compounds, calcium salts and boron compounds, and wherein the second solid electrolyte layer comprises at least one component selected from Mg(OH)2, Al(OH)3, Sb2O3, H3BO3, Fe(OH)3, CaCO3, Ca(OH)2, Zn(OH)2, NaOH, calcium magnesium hydroxide, hydrotalcite, boehmite, talc, sodium aluminum oxide, calcium sulfate hydrate and magnesium sulfate hydrate.

[0029] (19) The present invention provides an all-solid-state battery as in (18), wherein the first solid electrolyte layer contains at least one component in a content ranging from 20 wt% to 50 wt% based on the weight of the solid electrolyte contained in the first solid electrolyte layer.

[0030] (20) The present invention provides an all-solid-state battery as in (18), wherein the second solid electrolyte layer contains at least one component in a content ranging from 5 wt% to 20 wt% based on the weight of the solid electrolyte contained in the second solid electrolyte layer. Attached Figure Description

[0031] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings:

[0032] Figure 1 This is a graph showing the differential scanning calorimetry (DSC) results of all-solid-state batteries according to embodiments and comparative examples of the present invention;

[0033] Figure 2 This is a graph illustrating the robustness characteristics of an all-solid-state battery according to embodiments and comparative examples of the present invention, measured by a Saicas device;

[0034] Figure 3A This is a graph illustrating the charge / discharge characteristics of an all-solid-state battery according to embodiments and comparative examples of the present invention;

[0035] Figure 3B This is a graph showing the capacity retention rate (%) of all-solid-state batteries according to embodiments and comparative examples of the present invention as a function of the number of cycles;

[0036] Figure 4A This is a diagram showing a cross-section of an all-solid-state battery according to an embodiment of the present invention after impact, obtained through CT analysis. Figure 4B This is a diagram showing a cross-section of an all-solid-state battery according to a comparative example after impact, obtained through CT analysis;

[0037] Figure 5 This is a schematic cross-sectional view of an all-solid-state battery according to an embodiment of the present invention. Detailed Implementation

[0038] The invention will be described in more detail below.

[0039] The terms or words used in this specification and claims should not be interpreted as in their usual dictionary meanings, but rather as being based on the principles of the invention, which the inventors can properly define to best interpret the invention, and as being associated with the technical scope of the invention.

[0040] All-solid-state batteries

[0041] This invention provides an all-solid-state battery, comprising: a negative electrode; a first solid electrolyte layer disposed on the negative electrode; a second solid electrolyte layer disposed on the first solid electrolyte layer; and a positive electrode disposed on the second solid electrolyte layer. The first solid electrolyte layer contains an inorganic flame retardant, and the second solid electrolyte layer contains an endothermic flame retardant.

[0042] The components of the all-solid-state battery according to the present invention will be described in detail below.

[0043] negative electrode

[0044] According to the present invention, the negative electrode can be in the form of a negative electrode active material layer coated on the negative electrode current collector.

[0045] The negative electrode current collector gathers current to allow electrons to move to the external circuitry of the all-solid-state battery. It can provide higher conductivity, thus enabling rapid electron movement. The type of negative electrode current collector includes a variety of materials, without limitation, as long as these materials have conductivity and do not cause chemical changes in the all-solid-state battery. For example, the material may preferably include at least one selected from copper, stainless steel, aluminum, nickel, titanium, sintered carbon, materials obtained by surface treatment of copper or stainless steel surfaces with carbon, nickel, titanium, or silver, and aluminum-cadmium alloys.

[0046] The negative electrode active material layer may include a negative electrode active material, an adhesive for fixing the negative electrode active material, a conductive material for improving electronic conductivity, and a solid electrolyte.

[0047] The negative electrode active material can include a variety of materials, without limitation, as long as these materials are suitable for the negative electrode. Preferably, the negative electrode active material can include at least one selected from lithium metal, graphite, silicon, lithium titanium oxide (LTO), graphite, and carbon nanotubes (CNTs). More preferably, the negative electrode active material can include silicon and graphite.

[0048] The adhesive can include various materials, without specific limitations, as long as these materials can fix the negative electrode active material layer. Preferably, the adhesive can include at least one selected from: polybutadiene rubber, polyimide, ethylene propylene diene monomer (EPDM) rubber, polytetrafluoroethylene (PTFE), polyethylene oxide (PEO), polyethylene glycol, polyacrylonitrile, polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polypropylene oxide (PPO), polyphosphazene, polysiloxane, polydimethylsiloxane, polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE), polyvinylidene fluoride-tetrafluoroethylene copolymer (PVDF-TFE), polyvinyl carbonate, polyvinylpyrrolidone (PVP), styrene-butadiene rubber (SBR), nitrile rubber (NBR), and hydrogenated NBR. More specifically, the adhesive can include polybutadiene rubber.

[0049] The conductive material contained in the negative electrode active material layer can include various conductive materials without specific limitations, as long as these conductive materials can improve the conductivity of the negative electrode active material layer without causing chemical changes. For example, the conductive material may preferably include at least one selected from: carbon materials, such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers and carbon nanotubes; metallic materials containing copper, nickel, aluminum or silver in the form of metal powder or metal fibers; and conductive polymers, such as polystyrene derivatives.

[0050] Solid electrolytes can be inorganic solid electrolytes, such as sulfide solid electrolytes, oxide solid electrolytes, or halide solid electrolytes, or solid polymer electrolytes.

[0051] Sulfide solid electrolytes can be various general-purpose sulfide solid electrolytes and are not particularly limited. Preferably, the sulfide solid electrolyte may include at least one selected from the following: Li₂S-P₂S₅, Li₂S-P₂S₅-LiI, Li₂S-P₂S₅-LiCl, Li₂S-P₂S₅-LiBr, Li₂S-P₂S₅-Li₂O, Li₂S-P₂S₅-Li₂O-LiI, Li₂S-SiS₂, Li₂SSiS₂-LiI, Li₂S-SiS₂-LiBr, Li₂S-SiS₂-LiCl, Li₂S-SiS₂-B₂S₃-LiI, Li₂S-SiS₂-P₂S₅-LiI, Li₂S-B₂S₃, Li₂S-P₂S₅-Zm S n (where "m" and "n" are positive numbers; Z is one of Ge, Zn, and Ga), Li2S - GeS2, Li2S - SiS2 - Li3PO4, Li2S - SiS2 - Li x MO y (where "x" and "y" are positive numbers; M is one of P, Si, Ge, B, Al, Ga, In), and Li 10 GeP2S 12 .

[0052] The oxide - based solid electrolyte can be various common oxide - based solid electrolytes without special restrictions. Preferably, the oxide - based solid electrolyte can include at least one selected from the following: 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 TiyO3 (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, Li3PO4, Li x Ti y (PO4)3(0 < x < 2, 0 < y < 3), Li x Al y Ti z (PO4)3(0 < x < 2, 0 < y < 1, 0 < z < 3), Li 1+x+y (Al,Ga) x (Ti,Ge) 2-x Si y P 3-y O 12 (0 ≤ x ≤ 1 and 0 ≤ y ≤ 1), Li x La y TiO3(0 < x < 2 and 0 < y < 3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O - Al2O3 - SiO2 - P2O5 - TiO2 - GeO2, Li 3+x La3M2O 12 (M = Te, Nb or Zr; 0 ≤ x ≤ 10), and Li7La3Zr2-x Ta x O 12 (0 < x < 2; LLZ - Ta).

[0053] The solid polymer electrolyte can be various common solid polymer electrolytes without particular limitation. Preferably, the solid polymer electrolyte can include at least one selected from the following: polyethylene oxide, poly(diallyldimethylammonium)(TFSI), Cu3N, Li3N, LiPON, Li3PO4, Li2S·SiS2, Li2S·GeS2·Ga2S3, Li2O·11Al2O3, Na2O·11Al2O3, (Na,Li) 1+x Ti 2-x Al x (PO4)3(0.1 ≤ x ≤ 0.9), Li 1+x Hf 2-x Al x (PO4)3(0.1 ≤ x ≤ 0.9), Na3Zr2Si2PO 12 , Li3Zr2Si2PO 12 , Na5ZrP3O 12 , Na5TiP3O 12 , Na3Fe2P3O 12 , Na4NbP3O 12 , sodium - silicate, Li 0.3 La 0.5 TiO3, Na5MSi4O 12 (M is a rare earth element, such as Nd, Gd or Dy) Li5ZrP3O 12 , Li5TiP3O 12 , Li3Fe2P3O 12 , Li4NbP3O 12 , Li 1+x (M,Al,Ga) x (Ge 1-y Ti y ) 2-x (PO4)3(x ≤ 0.8; 0 ≤ y ≤ 1.0; M is Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm or Yb), Li 1+x+y Q x Ti 2-x Si y P 3-y O 12 (0 < x ≤ 0.4; 0 < y ≤ 0.6; Q is Al or Ga), Li6BaLa2Ta2O 12 , Li7La3Zr2O 12 , Li5La3Nb2O 12, Li5La3M2O 12 (where M is Nb or Ta) and Li 7+x A x La 3-x Zr2O 12 (0 < x < 3; A is Zn).

[0054] Halide solid electrolytes can include Li element, M element (where "M" is a metal other than lithium), and X element (where "X" is a halogen). In this case, "X" can be, for example, F, Cl, Br, and I. In particular, in halide solid electrolytes, "X" is preferably at least one of Br and Cl. In addition, M can be, for example, a metal element such as Sc, Y, B, Al, Ga, and In.

[0055] The first solid electrolyte layer

[0056] According to the present invention, the first solid electrolyte layer includes a solid electrolyte and an inorganic flame retardant with high particle strength, and can maintain robustness even when the volume of the negative electrode expands significantly and lithium metal is deposited. In this case, the solid electrolyte can be applied in the same way as the solid electrolyte contained in the negative electrode.

[0057] The inorganic flame retardant can include various materials without specific limitations, as long as these materials are materials with flame retardant properties based on inorganic materials with high particle strength and can provide thermal stability for all-solid-state batteries. For example, the inorganic flame retardant can preferably include at least one selected from LLZO, LATP, SiO2, ZnO, SnO2, Mn3O4, Sn2P2O7, alumina, magnesia, zeolite, zirconium compounds, calcium salts, and boron compounds. More preferably, the inorganic flame retardant can include LATP.

[0058] Based on the solid electrolyte contained in the first solid electrolyte layer, the content of the inorganic flame retardant can be in the range of 20 wt% to 50 wt%, and more preferably in the range of 25 wt% or 30 wt% to 45 wt% or 40 wt%. When the content of the inorganic flame retardant is within the above range, the inorganic flame retardant can improve the thermal stability of the first solid electrolyte layer, reduce the risk of thermal runaway of all-solid-state batteries, and improve the mechanical properties of all-solid-state batteries without reducing electrical properties such as ionic conductivity or voltage characteristics.

[0059] The first solid electrolyte layer according to the present invention can also include an adhesive. When the first solid electrolyte layer further includes an adhesive, the mechanical strength and durability of the first solid electrolyte layer can be improved, and the overall performance and overall lifespan of all-solid-state batteries can be enhanced. In this case, the adhesive can be applied in the same way as the adhesive that can be contained in the negative electrode.

[0060] Based on the solid electrolyte included in the first solid electrolyte layer, the binder content can range from 0.5 wt% to 5 wt%, more preferably from 2 wt% to 4 wt%. When the binder content is within the above range, the bonding between solid electrolyte particles can be enhanced to optimize the mechanical strength and structural stability of the first solid electrolyte layer, thereby improving the durability of the all-solid-state battery. Furthermore, the binder can provide structural stability without interrupting ion conduction pathways. Therefore, the binder can maintain the electrochemical performance of the all-solid-state battery while improving its charge / discharge efficiency.

[0061] Second solid electrolyte layer

[0062] The second solid electrolyte layer according to the invention may include a solid electrolyte and a heat-absorbing flame retardant to prevent heat from the positive electrode from being transferred to the entire battery, since the heat is first absorbed by the heat-absorbing flame retardant, thereby suppressing thermal runaway in all-solid-state batteries. In this case, the solid electrolyte can be used in the same way as a solid electrolyte that can be included in the negative electrode.

[0063] The heat-endothermic flame retardant can include various materials, without specific limitations, as long as these materials are commonly used as heat-endothermic flame retardants. Preferably, the heat-endothermic flame retardant can include at least one selected from Mg(OH)2, Al(OH)3, Sb2O3, H3BO3, Fe(OH)3, CaCO3, Ca(OH)2, Zn(OH)2, NaOH, calcium magnesium hydroxide, hydrotalcite, boehmite, talc, sodium aluminum oxide, calcium sulfate hydrate, and magnesium sulfate hydrate. More preferably, the heat-endothermic flame retardant can include Al(OH)3. Furthermore, since the reaction mechanism involves halogenated flame retardants, halogenated flame retardants can also be used in this invention.

[0064] Based on the solid electrolyte included in the second solid electrolyte layer, the content of the heat-absorbing flame retardant can be in the range of 5 wt% to 20 wt%, more preferably in the range of 7 wt% to 15 wt%. When the content of the heat-absorbing flame retardant is within the above range, the heat-absorbing flame retardant can improve the thermal stability of the second solid electrolyte layer, reduce the risk of thermal runaway in all-solid-state batteries, and improve the mechanical properties of all-solid-state batteries without reducing electrical properties such as ionic conductivity or voltage characteristics.

[0065] The second solid electrolyte layer according to the invention may further include an adhesive. When the second solid electrolyte layer also includes an adhesive, the mechanical strength and durability of the second solid electrolyte layer can be improved, and the overall performance and lifespan of the all-solid-state battery can be enhanced. The adhesive can be used in the same way as adhesives that can be included in the negative electrode and adhesives that can be included in the first solid electrolyte layer.

[0066] According to the present invention, the ratio of the thickness of the first solid electrolyte layer to the thickness of the second solid electrolyte layer can be in the range of 1:9 to 9:1. Preferably, the ratio can be in the range of 2:8 to 8:2 or 3:7 to 7:3. When this ratio meets the corresponding range, the onset temperature of the exothermic reaction can be reduced, thereby reducing the heat generated. Therefore, the thermal stability of the all-solid-state battery can be further improved. In addition, the durability of the electrolyte layer can also be improved.

[0067] The combined thickness of the first and second solid electrolyte layers can range from 10 μm to 120 μm, preferably from 30 μm to 80 μm. When the combined thickness meets the corresponding range, the ionic conductivity can be optimized to maintain the electrochemical performance of the all-solid-state battery, while uniformly maintaining the charge / discharge rate or energy density. Furthermore, it can maintain shock or deformation resistance, ensuring battery durability. Additionally, it can ensure higher energy density and optimize the contact area with the electrodes to maximize the performance of the all-solid-state battery.

[0068] positive electrode

[0069] The positive electrode according to the present invention can be in the form of coating a positive electrode active material layer onto a positive electrode current collector, and the positive electrode active material layer may include a positive electrode active material, a binder, a conductive material, and a solid electrolyte. The binder, conductive material, and solid electrolyte can be used in the same way as binders, conductive materials, and solid electrolytes that can be included in a negative electrode.

[0070] The positive electrode active material can include various materials without specific limitations, as long as these materials are active materials used in the positive electrode. For example, the positive electrode may preferably include at least one selected from lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium iron phosphate (LFP), nickel cobalt manganese oxide (NCM), nickel cobalt aluminum oxide (NCA), and lithium nickel manganese oxide (LNMO). More preferably, the positive electrode active material may include lithium cobalt manganese oxide.

[0071] Methods for manufacturing all-solid-state battery anodes

[0072] This invention provides a method (or manufacturing process) for manufacturing an all-solid-state battery, comprising manufacturing an all-solid-state battery (S0) having a structure in which a negative electrode, a first solid electrolyte layer, a second solid electrolyte layer, and a positive electrode are stacked in sequence. The first solid electrolyte layer contains an inorganic flame retardant, and the second solid electrolyte layer contains an endothermic flame retardant.

[0073] The manufacturing method of the present invention will be described in detail below.

[0074] "S0" may include the following steps: manufacturing a negative electrode assembly formed by sequentially stacking a negative electrode, a first solid electrolyte layer, and a second solid electrolyte layer (S1); and stacking the negative electrode assembly and a positive electrode such that the second solid electrolyte layer faces the positive electrode. The negative electrode assembly may be manufactured using a wet-on-wet or wet-on-dry method.

[0075] When manufacturing a negative electrode assembly using a wet-on-wet process, "S0" may include the following steps: coating a negative electrode slurry onto a negative electrode current collector; and, while the negative electrode slurry coated onto the negative electrode current collector is still wet, sequentially coating a first solid electrolyte slurry and a second solid electrolyte slurry and drying them.

[0076] When manufacturing a negative electrode assembly using a wet-on-dry method, "S0" may include the following steps: forming a negative electrode by coating a negative electrode slurry onto a negative electrode current collector and drying it; forming a first solid electrolyte layer by coating a first solid electrolyte slurry onto the negative electrode and drying it; and coating a second solid electrolyte slurry onto the first solid electrolyte layer and drying it.

[0077] Furthermore, "S0" may include the following steps: manufacturing a positive electrode assembly, which is formed by sequentially stacking a positive electrode, a second solid electrolyte layer, and a first solid electrolyte layer (S1'); and stacking the positive electrode assembly and the negative electrode such that the first solid electrolyte layer faces the negative electrode. The positive electrode assembly may be manufactured using a wet-on-wet method or a wet-on-dry method.

[0078] When manufacturing a positive electrode assembly using a wet-on-wet method, "S0" may include the following steps: coating a positive electrode slurry onto a positive electrode current collector; and, while the positive electrode slurry coated onto the positive electrode current collector is still wet, sequentially coating a second solid electrolyte slurry and a first solid electrolyte slurry and drying them.

[0079] When manufacturing a positive electrode assembly using a wet-on-dry method, "S0" may include the following steps: forming a positive electrode by coating a positive electrode slurry onto a positive electrode current collector and drying it; forming a second solid electrolyte layer by coating a second solid electrolyte slurry onto the positive electrode and drying it; and coating a first solid electrolyte slurry onto the second solid electrolyte layer and drying it.

[0080] Furthermore, "S0" may include the following steps: manufacturing a negative electrode assembly including a negative electrode and a first solid electrolyte layer (S1"); manufacturing a positive electrode assembly including a positive electrode and a second solid electrolyte layer (S2"); and stacking the positive electrode assembly and the negative electrode assembly such that the first solid electrolyte layer and the second solid electrolyte layer face each other (S3"). The negative electrode assembly or the positive electrode assembly may be manufactured using a wet-on-wet method or a wet-on-dry method.

[0081] When manufacturing a negative electrode assembly or a positive electrode assembly using a wet-on-wet process, "S0" may include the following steps: coating a negative electrode slurry onto a negative electrode current collector; while the negative electrode slurry coated onto the negative electrode current collector is still wet, sequentially coating a first solid electrolyte slurry and drying it; coating a positive electrode slurry onto a positive electrode current collector; while the positive electrode slurry coated onto the positive electrode current collector is still wet, sequentially coating a second solid electrolyte slurry and drying it.

[0082] When manufacturing a negative electrode assembly or a positive electrode assembly using a wet-on-dry method, "S0" may include the following steps: coating a negative electrode slurry onto a negative electrode current collector and drying it to form a negative electrode; coating a first solid electrolyte slurry onto the negative electrode and drying it to form a first solid electrolyte layer; coating a positive electrode slurry onto a positive electrode current collector and drying it to form a positive electrode; and coating a second solid electrolyte slurry onto the positive electrode and drying it to form a second solid electrolyte layer.

[0083] The drying step in the negative or positive electrode assembly can be a step of evaporating the solvent of each slurry to retain only the solid components, and can include various methods without specific limitations, as long as the solvent can be effectively removed. The drying step can preferably be carried out in a temperature range of 60°C to 120°C, more preferably in a range of 70°C to 110°C.

[0084] Implementation

[0085] The embodiments of the present invention will be described in more detail below. However, the following embodiments are for illustrative purposes only, and the scope of the present invention is not limited to the following embodiments.

[0086] Implementation Method 1

[0087] (S1) The negative electrode is manufactured by the following steps: coating a negative electrode slurry onto a Ni foil negative electrode current collector. The negative electrode slurry is composed of 58.8 wt% Si-Gr composite material (as the negative electrode active material), 39.2 wt% sulfide solid electrolyte, 2 wt% polybutadiene rubber (as a binder), and butyl butyrate; drying the resulting structure.

[0088] (S2) The first solid electrolyte layer is formed by the following steps: coating the negative electrode with a first solid electrolyte layer slurry, the first solid electrolyte layer slurry being a mixture of 30 wt% LATP (as an inorganic flame retardant), 3 wt% polybutadiene rubber (as an adhesive), and butyl butyrate (as a solvent); and drying the resulting structure at 90°C.

[0089] (S3) The second solid electrolyte layer is formed by the following steps: coating the first solid electrolyte layer with a second solid electrolyte layer slurry, the second solid electrolyte layer slurry being a mixture of 15 wt% Al(OH)3 (as a heat-absorbing flame retardant), 3 wt% polybutadiene rubber (as an adhesive), and butyl butyrate (as a solvent); and drying the resulting structure at 90°C.

[0090] (S4) The positive electrode is formed by the following steps: coating a positive electrode slurry onto an Al foil positive electrode current collector. The positive electrode slurry is composed of 77.12 wt% NCM 811 (as the positive electrode active material), 19.28 wt% sulfide solid electrolyte, 2 wt% polybutadiene rubber (as a binder), and 1.5 wt% spherical carbon (as a conductive material) mixed with butyl butyrate (as a solvent); and drying the resulting structure.

[0091] (S5) The positive electrode on the second solid electrolyte layer is rolled to form an all-solid-state battery.

[0092] In this case, the ratio of the thickness of the second solid electrolyte layer to the thickness of the first solid electrolyte layer is adjusted to 7:3.

[0093] Implementation Method 2

[0094] The all-solid-state battery was manufactured using the same method as in Embodiment 1, except that the ratio of the thickness of the second solid electrolyte layer to the thickness of the first solid electrolyte layer was adjusted to 1:1.

[0095] Implementation Method 3

[0096] The all-solid-state battery was manufactured using the same method as in Embodiment 1, except that the ratio of the thickness of the second solid electrolyte layer to the thickness of the first solid electrolyte layer was adjusted to 3:7.

[0097] Comparative Example 1

[0098] The all-solid-state battery is manufactured using the same method as in Embodiment 1, except that instead of “S2” and “S3” in Embodiment 1, the solid electrolyte layer is formed by coating a solid electrolyte slurry prepared from a mixture of 97 wt% sulfide-based solid electrolyte and 3 wt% polybutadiene and butyl butyrate, and then drying the result.

[0099] Comparative Example 2

[0100] The all-solid-state battery was manufactured using the same method as in Embodiment 1, except that, instead of (S2) and (S3) in Embodiment 1, the solid electrolyte layer was formed by coating a solid electrolyte slurry obtained by mixing 15 wt% Al(OH)3 (as an endothermic flame retardant), 30 wt% LATP (as an inorganic flame retardant), and 3 wt% polybutadiene rubber (as an adhesive) with butyl butyrate (as a solvent), and then drying it.

[0101] Experimental Example 1: Analysis of Battery Thermal Characteristics

[0102] In this experiment, the batteries manufactured in the embodiments and preparation examples were charged to 100% SOC, and their thermal characteristics were analyzed by differential scanning calorimetry (DSC). The experiment was conducted under an argon atmosphere, with a heating rate of 5 °C / min, and a temperature range of 25 °C to 350 °C. The analytical results (ionic conductivity [mS / cm], heating onset temperature [ °C], and calorific value [J / g]) are shown in Table 1 below. The calorific value based on temperature is presented as a graph, as shown below. Figure 1 As shown.

[0103] Table 1

[0104] Ionic conductivity [mS / cm] Heating onset temperature [°C] Calorific value [J / g] Implementation Method 1 1.91 187.4 897.8 Implementation Method 2 2.64 186.53 916.4 Implementation Method 3 2.57 180.75 930.5 Comparative Example 1 3.04 174.66 993.1

[0105] Refer to Table 1 and Figure 1 As can be seen, Embodiment 1 exhibits the highest onset temperature and the lowest calorific value, thus maximizing thermal stability. Furthermore, it can be seen that Embodiments 2 and 3 exhibit higher onset temperatures and lower calorific values ​​compared to Comparative Example 1. Therefore, it can be demonstrated that, compared to existing batteries containing a solid electrolyte layer, batteries with a bilayer solid electrolyte comprising both an endothermic flame retardant and a ceramic flame retardant (similar to the present invention) achieve greater improvement in thermal stability.

[0106] Experimental Example 2: The robustness of the electrolyte layer was improved as determined by testing.

[0107] In this experiment, the degree of improvement in electrolyte layer robustness was determined by measuring the resistance of the electrolyte layer in the all-solid-state batteries manufactured in the embodiments and comparative examples. The experiment was conducted using a "Saicas" apparatus under conditions of a horizontal force of 1 N, a depth of 2 μm, a front angle of 20°, a shear angle of 45°, and a vertical velocity of 5 μm / s. The change in resistance over time was measured, and the results are shown in the form of a graph, as follows: Figure 2 As shown.

[0108] from Figure 2As can be seen, compared to the comparative examples, the battery according to the embodiments of the present invention exhibits greater improvement in robustness. In other words, comparative examples 1 and 2, which contain a solid electrolyte layer with a single-layer structure, are inferior to the embodiments in terms of disturbance rejection. By providing a bilayer solid electrolyte containing a heat-absorbing flame retardant and a ceramic flame retardant, the present invention demonstrates better robustness of the electrolyte layer.

[0109] Experiment Example 3: Determination of Battery Electrochemical Characteristics

[0110] In this experiment, the electrochemical characteristics of all-solid-state batteries manufactured according to the embodiments and comparative examples were evaluated. In this experiment, the charge / discharge conditions were maintained in the range of 2.0V to 4.25V at a temperature of 30°C, formation was performed at 0.05C in two cycles, and charge / discharge was performed at 0.2C. Therefore, as Figure 3A and 3B As shown, the charge / discharge curves and the capacity retention rate (%) are presented as a function of the number of cycles.

[0111] from Figure 3A As can be seen, compared to the comparative example, the battery according to the embodiment of the present invention exhibits a similar charging capacity and a higher discharging capacity. Therefore, it can be seen that the battery according to the embodiment of the present invention exhibits charging / discharging performance similar to that of the existing comparative example. Furthermore, from... Figure 3B It can be seen that even with increased cycle count, the battery according to the embodiment of the present invention maintains its capacity excellently, while the battery according to the comparative example experiences a sharp and continuous capacity decrease during the initial cycle. Therefore, it can be seen that the battery according to the embodiment of the present invention exhibits a stable capacity retention rate compared to the comparative example. Thus, it can be seen that by providing a bilayer solid electrolyte comprising an endothermic flame retardant and a ceramic flame retardant, the present invention achieves charge / discharge characteristics and capacity retention rates similar to those of conventional batteries.

[0112] Experiment Example 4: Determination of Improved Battery Stability

[0113] In this experiment, an impact test was conducted using an all-solid-state battery manufactured according to the embodiment and comparative example. The experiment was performed by dropping a 9.1 kg weight with a diameter of 15.8 mm from a height of 61 cm onto the battery with 97% SOC. The cross-section of the all-solid-state battery was measured by CT analysis after the experiment. The experimental results are as follows: Figure 4A and 4B As shown.

[0114] from Figure 4A and 4BIt can be seen that in the all-solid-state battery according to the present invention, the electrolyte layer does not rupture even under external impact. However, it can be seen that in the all-solid-state battery according to the comparative example, the battery and the solid electrolyte layer rupture together under external impact. Therefore, it can be seen that by providing a bilayer solid electrolyte comprising a heat-absorbing flame retardant and a ceramic flame retardant, the stability of the battery is improved.

[0115] The all-solid-state battery according to the present invention comprises a bilayer structure of a first solid electrolyte layer and a second solid electrolyte layer. The first solid electrolyte layer contains an inorganic flame retardant with higher particle strength, maintaining robustness even if the negative electrode volume expands significantly and lithium metal is deposited; the second solid electrolyte layer contains an endothermic flame retardant to improve the thermal stability of the positive electrode portion. Therefore, the all-solid-state battery will not be damaged even under external impact, thereby improving stability; even with repeated cycling, it can exhibit a higher capacity retention rate than existing all-solid-state batteries; and it can better suppress thermal runaway than existing all-solid-state batteries.

[0116] While the invention has been described above with reference to exemplary embodiments and accompanying drawings, it is not limited thereto. Various modifications and alterations can be made by those skilled in the art without departing from the spirit and scope of the invention as claimed in the claims.

Claims

1. An all-solid-state battery, comprising: negative electrode; A first solid electrolyte layer is located on the negative electrode; A second solid electrolyte layer, which is located on top of the first solid electrolyte layer; and The positive electrode is located on the second solid electrolyte layer. The first solid electrolyte layer contains an inorganic flame retardant, and The second solid electrolyte layer contains an endothermic flame retardant.

2. The all-solid-state battery according to claim 1, wherein the inorganic flame retardant comprises at least one selected from LLZO, LATP, SiO2, ZnO, SnO2, Mn3O4, Sn2P2O7, aluminum oxide, magnesium oxide, zeolite, zirconium compounds, calcium salts and boron compounds.

3. The all-solid-state battery according to claim 1, wherein the content of the inorganic flame retardant in the first solid electrolyte layer is in the range of 20 wt% to 50 wt% based on the weight of the solid electrolyte contained in the first solid electrolyte layer.

4. The all-solid-state battery according to claim 1, wherein the heat-absorbing flame retardant comprises at least one selected from Mg(OH)2, Al(OH)3, Sb2O3, H3BO3, Fe(OH)3, CaCO3, Ca(OH)2, Zn(OH)2, NaOH, calcium magnesium hydroxide, hydrotalcite, boehmite, talc, sodium aluminum oxide, calcium sulfate hydrate, and magnesium sulfate hydrate.

5. The all-solid-state battery according to claim 1, wherein, based on the weight of the solid electrolyte contained in the second solid electrolyte layer, the content of the heat-absorbing flame retardant in the second solid electrolyte layer is in the range of 5 wt% to 20 wt%.

6. The all-solid-state battery according to claim 1, wherein the ratio of the thickness of the first solid electrolyte layer to the thickness of the second solid electrolyte layer is 1:9 to 9:

1.

7. The all-solid-state battery according to claim 1, wherein the sum of the thickness of the first solid electrolyte layer and the thickness of the second solid electrolyte layer is 10 μm to 120 μm.

8. The all-solid-state battery according to claim 1, wherein the first solid electrolyte layer and the second solid electrolyte layer each further comprise an adhesive.

9. The all-solid-state battery of claim 8, wherein the binder content is in the range of 0.5 wt% to 5 wt% based on the weight of the solid electrolyte in each of the first solid electrolyte layer and the second solid electrolyte layer.

10. The all-solid-state battery according to claim 8, wherein the adhesive comprises at least one selected from polybutadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), polyimide (PI), polyvinylidene fluoride (PVDF), and ethylene propylene diene monomer (EPDM).

11. A method for manufacturing an all-solid-state battery, the method comprising the following steps: In manufacturing the all-solid-state battery, the negative electrode, the first solid electrolyte layer, the second solid electrolyte layer, and the positive electrode are stacked in sequence. The first solid electrolyte layer contains an inorganic flame retardant, and The second solid electrolyte layer contains an endothermic flame retardant.

12. The method of claim 11, wherein the step of manufacturing the all-solid-state battery comprises the following steps: A negative electrode assembly is manufactured by sequentially stacking the negative electrode, the first solid electrolyte layer, and the second solid electrolyte layer; and The negative electrode assembly and the positive electrode are stacked such that the second solid electrolyte layer faces the positive electrode.

13. The method of claim 12, wherein the negative electrode assembly is manufactured using a wet-on-wet or wet-on-dry configuration.

14. The method of claim 11, wherein the step of manufacturing the all-solid-state battery comprises the following steps: A positive electrode assembly is manufactured by sequentially stacking the positive electrode, the second solid electrolyte layer, and the first solid electrolyte layer; and The positive electrode assembly and the negative electrode are stacked such that the first solid electrolyte layer faces the negative electrode.

15. The method of claim 14, wherein the positive electrode assembly is manufactured using a wet-on-wet or wet-on-dry configuration.

16. The method of claim 11, wherein the step of manufacturing the all-solid-state battery comprises the following steps: Manufacturing the negative electrode assembly comprising the negative electrode and the first solid electrolyte layer; Manufacturing the positive electrode assembly comprising the positive electrode and the second solid electrolyte layer; and The negative electrode assembly and the positive electrode assembly are stacked such that the first solid electrolyte layer and the second solid electrolyte layer face each other.

17. The method of claim 16, wherein the negative electrode assembly or the positive electrode assembly is each manufactured using a wet-on-wet or wet-on-dry method.

18. An all-solid-state battery, comprising: negative electrode; A first solid electrolyte layer is located on the negative electrode; A second solid electrolyte layer, which is located on top of the first solid electrolyte layer; and The positive electrode is located on the second solid electrolyte layer. The first solid electrolyte layer comprises at least one component selected from LLZO, LATP, SiO2, ZnO, SnO2, Mn3O4, Sn2P2O7, aluminum oxide, magnesium oxide, zeolite, zirconium compounds, calcium salts, and boron compounds. The second solid electrolyte layer contains at least one component selected from Mg(OH)2, Al(OH)3, Sb2O3, H3BO3, Fe(OH)3, CaCO3, Ca(OH)2, Zn(OH)2, NaOH, calcium magnesium hydroxide, hydrotalcite, boehmite, talc, sodium aluminum oxide, calcium sulfate hydrate, and magnesium sulfate hydrate.

19. The all-solid-state battery of claim 18, wherein, based on the weight of the solid electrolyte contained in the first solid electrolyte layer, the first solid electrolyte layer contains at least one component in an amount ranging from 20 wt% to 50 wt%.

20. The all-solid-state battery of claim 18, wherein, based on the weight of the solid electrolyte contained in the second solid electrolyte layer, the second solid electrolyte layer contains at least one component in an amount ranging from 5 wt% to 20 wt%.

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