All-solid-state battery including two solid electrolyte layers

Abstract

The present invention relates to an all-solid-state battery with improved safety and low resistance, comprising a positive electrode, a negative electrode, and a solid electrolyte disposed between the positive electrode and the negative electrode, wherein the solid electrolyte comprises a first solid electrolyte layer containing a binder and a second solid electrolyte layer not containing a binder, and the second solid electrolyte layer faces the negative electrode.

Description

Technical Field

[0001] This application claims priority from Korean Patent Application No. 2021-0041332, filed on March 30, 2021, the disclosure of which is incorporated herein by reference in its entirety.

[0002] The present invention relates to an all-solid-state battery comprising two solid electrolyte layers. More specifically, the present invention relates to an all-solid-state battery comprising two solid electrolyte layers, wherein the adhesion surface between the solid electrolyte layers and the negative electrode is increased, thereby reducing the risk of short circuits in the all-solid-state battery. Background Art

[0003] Rechargeable lithium secondary batteries with high energy density have attracted much attention as a new energy source with environmentally friendly characteristics because they not only significantly reduce the use of fossil fuels but also do not produce by-products due to the use of energy.

[0004] Lithium secondary batteries are also attracting attention as energy sources for devices with high output and high energy density, such as electric vehicles, as well as wearable and portable devices. As a result, research on lithium secondary batteries with high operating voltage and energy density is progressing rapidly.

[0005] As a type of lithium secondary battery, a lithium-ion secondary battery comprising an electrolyte and a separator has the disadvantage of high risk of electrolyte leakage and fire outbreak. As an alternative, an all-solid-state battery has been proposed, which uses a non-flammable solid as an electrolyte and thus has a low risk of fire outbreak and explosion.

[0006] The advantages of all-solid-state batteries are improved safety, high mobility of lithium ions due to the use of solid electrolytes, and reduced thickness of the negative electrode, thereby increasing energy density.

[0007] As a means for improving the energy density of an all-solid-state battery, a negative electrode including no negative electrode mixture layer and consisting only of a current collector has been proposed.

[0008] When the all-solid-state battery configured as described above is charged, lithium is plated on the negative electrode current collector at the portion where the negative electrode current collector and the solid electrolyte layer contact each other, and when the all-solid-state battery is discharged, the lithium plated on the negative electrode current collector is stripped. As a result of repeated charging and discharging, the size of the lithium plated on the negative electrode current collector may gradually increase, thereby allowing lithium dendrites to grow. Lithium dendrites may cause a battery short circuit or may reduce the battery capacity.

[0009] That is, when the contact area between the negative electrode current collector and the solid electrolyte layer is small, lithium plating occurs locally, and thus the possibility of lithium dendrite growth may further increase.

[0010] Related to this,Figure 1 This is a cross-sectional diagram of the solid electrolyte layer and negative electrode in a conventional high-energy-density all-solid-state battery.

[0011] refer to Figure 1 , the solid electrolyte layer 120 is formed on one surface of the negative electrode 140. The solid electrolyte layer 120 is configured in a state where solid electrolyte particles 110 are bound by a binder 130, and is provided on one surface of the negative electrode 140.

[0012] The lithium that moves to the negative electrode 140 through the solid electrolyte particles 110 is plated on the surface of the negative electrode 140; however, the binder 130 located between the solid electrolyte particles 110 and the negative electrode 140 prevents the lithium from moving to the negative electrode.

[0013] exist Figure 1 In the figure, among the solid electrolyte particles in contact with the negative electrode, solid electrolyte particles that allow lithium to move through are indicated by arrows, and solid electrolyte particles whose lithium movement paths are blocked by the binder 130 are indicated by no arrows.

[0014] As described above, if lithium cannot move due to the binder, or the movement speed of lithium is reduced, the resistance of the all-solid-state battery increases.

[0015] Therefore, there is a need to develop an all-solid-state battery configured so that the contact area between the solid electrolyte layer and the negative electrode is increased, thereby making the resistance of the battery low.

[0016] For all-solid-state batteries using sulfide-based solid electrolytes, a method for producing the solid electrolyte layer by pressing without a binder can be used to minimize the resistance of the solid electrolyte layer. However, in this case, the solid electrolyte layer is produced to a thickness of several hundred micrometers, which is not suitable for manufacturing high-energy-density all-solid-state batteries.

[0017] In this regard, Patent Document 1 relates to an all-solid-state battery configured such that an electrolyte layer is provided between a positive electrode layer and a negative electrode layer, the electrolyte layer including a first solid electrolyte layer and a second solid electrolyte layer, and a binder is contained in the first solid electrolyte layer and / or the second solid electrolyte layer.

[0018] The all-solid-state battery of Patent Document 1 includes a sulfide-based solid electrolyte and discloses that the inclusion of a binder can achieve the effect of ensuring the dispersion of sulfide-based solid electrolyte particles and reduce the thickness of the solid electrolyte layer, thereby reducing resistance.

[0019] Patent document 2 relates to an electrolyte layer for an all-solid-state battery, which is configured as a stack of two or more electrolyte layers and the two or more electrolyte layers have different binder contents, and discloses that when a lamination method is used, the substrate is smoothly peeled off from the electrolyte layer and the thickness of the electrolyte layer is appropriately adjusted, thereby minimizing the interface resistance between the electrode layer and the electrolyte layer.

[0020] However, Patent Documents 1 and 2 do not propose a solution to the problem of increased resistance of the all-solid-state battery due to the binder contained in the solid electrolyte layer.

[0021] (Prior art literature)

[0022] (Patent Document 1) Japanese Registered Patent No. 5930035 (June 8, 2016)

[0023] (Patent Document 2) Korean Patent Application Publication No. 2017-0055325 (May 19, 2017) Summary of the Invention

[0024] [Technical Issues]

[0025] The present invention is made in view of the above problems, and an object of the present invention is to provide an all-solid-state battery comprising two solid electrolyte layers, which is configured to prevent the growth of lithium dendrites on the surface of the negative electrode, thereby ensuring the safety of the all-solid-state battery.

[0026] [Technical solution]

[0027] The all-solid-state battery of the present invention for achieving the above-mentioned purpose includes a positive electrode, a negative electrode and a solid electrolyte placed between the positive electrode and the negative electrode, wherein the solid electrolyte is composed of a first solid electrolyte layer containing an adhesive and a second solid electrolyte layer not containing an adhesive, and the second solid electrolyte layer faces the negative electrode.

[0028] The binder can be at least one selected from the group consisting of polytetrafluoroethylene, polyethylene oxide, polyethylene glycol, polyacrylonitrile, polyvinyl chloride, polymethyl methacrylate, polypropylene oxide, polyphosphazene, polysiloxane, polydimethylsiloxane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE), polyvinylidene fluoride-tetrafluoroethylene copolymer (PVDF-TFE), polyvinylene carbonate, polyvinyl pyrrolidone, styrene-butadiene rubber, nitrile rubber and hydrogenated nitrile rubber.

[0029] The first solid electrolyte layer and the second solid electrolyte layer may have the same components except for the binder.

[0030] The thickness of the first solid electrolyte layer may be equal to or greater than the thickness of the second solid electrolyte layer.

[0031] The binder may be contained in the first solid electrolyte layer in an amount of 0.2 wt % to 15 wt % based on the weight of the total solid components contained in the first solid electrolyte layer.

[0032] The first solid electrolyte layer and the second solid electrolyte layer may be in a state of being adhered to each other.

[0033] The negative electrode may not include a negative electrode mixture layer.

[0034] The negative electrode may include a coating and an ion transport layer.

[0035] The solid electrolyte particles located on the surface of the second solid electrolyte layer may be in contact with the negative electrode.

[0036] The present invention provides a battery module comprising the all-solid-state battery as a unit cell.

[0037] In addition, the present invention can provide various combinations of the above-mentioned solutions.

[0038] [Beneficial Effects]

[0039] As apparent from the above description, in the all-solid-state battery of the present invention, the contact area between the solid electrolyte layer and the negative electrode at the interface thereof is increased, thereby preventing local lithium plating on the surface of the negative electrode.

[0040] Therefore, the growth of lithium dendrites on the surface of the negative electrode can be suppressed.

[0041] As a result, the risk of short circuit in the all-solid-state battery is reduced, thereby improving the safety of the all-solid-state battery.

[0042] In addition, the lithium migration path is ensured over a wide range, thereby reducing the resistance of the all-solid-state battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a cross-sectional diagram of the solid electrolyte layer and negative electrode in a conventional high-energy-density all-solid-state battery.

[0044] Figure 2 It is a cross-sectional view of the solid electrolyte layer and the negative electrode in the all-solid-state battery of the present invention. DETAILED DESCRIPTION

[0045] Now, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that the present invention can be easily implemented by those skilled in the art. However, when describing the operating principles of the preferred embodiments of the present invention in detail, when the known functions and structures incorporated herein may obscure the subject matter of the present invention, their detailed description will be omitted.

[0046] In addition, the same reference numerals will be used throughout the drawings to refer to components that perform similar functions or operations. When a component is described in the specification as being connected to another component, not only can the component be directly connected to the other component, but the component can also be indirectly connected to the other component via another component. In addition, the inclusion of a certain element does not mean the exclusion of other elements, but rather means that these other elements may be further included unless otherwise specified.

[0047] In addition, the description embodying elements by limitation or addition can be applied to all inventions unless otherwise limited, and does not limit a specific invention.

[0048] Furthermore, in the description and claims of the present invention, the singular form is intended to include the plural form unless otherwise stated.

[0049] Moreover, in the description and claims of the present invention, "or" includes "and" unless otherwise specified. Therefore, "including A or B" refers to three cases, namely, the case including A, the case including B, and the case including A and B.

[0050] Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0051] The all-solid-state battery of the present invention may include a positive electrode, a negative electrode, and a solid electrolyte placed between the positive electrode and the negative electrode, wherein the solid electrolyte may be composed of a first solid electrolyte layer containing an adhesive and a second solid electrolyte layer not containing an adhesive, and the second solid electrolyte layer may face the negative electrode.

[0052] For example, the positive electrode is manufactured by applying a positive electrode mixture containing a positive electrode active material to a positive electrode current collector and drying the positive electrode mixture. If necessary, the positive electrode mixture may further optionally contain a binder, a conductive agent, and a filler.

[0053] There is no particular limitation on the positive electrode current collector, as long as the positive electrode current collector exhibits high conductivity and does not cause any chemical changes in the battery to which the positive electrode current collector is applied. For example, the positive electrode current collector can be made of stainless steel, aluminum, nickel, titanium or sintered carbon. Alternatively, the positive electrode current collector can be made of aluminum or stainless steel whose surface is treated with carbon, nickel, titanium or silver. In addition, the positive electrode current collector can be formed with a micro-concave-convex pattern on its surface to increase the adhesion of the positive electrode active material. The positive electrode current collector can be constructed into any of various forms, such as a film, a sheet, a foil, a mesh, a porous body, a foam body and a non-woven fabric body.

[0054] The positive electrode active material is a material capable of inducing an electrochemical reaction, and may include at least one of the positive electrode active materials represented by the following Chemical Formulas 1 to 3.

[0055] Li a Co 1-x M x O2 (1)

[0056] Li a Mn 2-y M y O4 (2)

[0057] Li a Fe 1-z M z PO4 (3)

[0058] In the above formula, 0.8≤a≤1.2, 0≤x≤0.8, 0≤y≤0.6, and 0≤z≤0.5, and

[0059] M is at least one selected from the group consisting of Ti, Cd, Cu, Cr, Mo, Mg, Al, Ni, Mn, Nb, V, and Zr.

[0060] That is, the positive active material may include at least one material selected from the group consisting of a lithium metal oxide having a layered structure represented by Chemical Formula 1, a lithium manganese-based oxide having a spinel structure represented by Chemical Formula 2, and a lithium-containing phosphate having an olivine structure represented by Chemical Formula 3.

[0061] Although the type of lithium metal oxide having a layered structure is not limited, for example, at least one selected from the group consisting of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium cobalt nickel oxide, lithium cobalt manganese oxide, lithium manganese nickel oxide, lithium nickel cobalt manganese oxide, and materials obtained by substituting or doping them with another element can be used.

[0062] Lithium nickel cobalt manganese oxide can be made from Li 1+z Ni b Co c Mn 1-(b+c+d) M d O (2-e) A e (wherein, -0.5≤z≤0.5, 0.1≤b≤0.8, 0.1≤c≤0.8, 0≤d≤0.2, 0≤e≤0.2, b+c+d<1, M=Al, Mg, Cr, Ti, Si or Y, and A=F, P or Cl).

[0063] Although the type of the lithium manganese-based oxide having a spinel structure is not limited, for example, at least one selected from the group consisting of lithium manganese oxide, lithium nickel manganese oxide, and materials obtained by substituting or doping them with another element may be used.

[0064] In addition, although the type of the lithium-containing phosphate having an olivine structure is not limited, for example, at least one selected from the group consisting of lithium iron phosphate and materials obtained by substituting or doping the same with another element may be used.

[0065] The other element may be at least one selected from the group consisting of Al, Mg, Mn, Ni, Co, Cr, V, and Fe.

[0066] Binder is a component that helps to bind the active material and the conductive agent and to bind the current collector. Based on the total weight of the mixture containing the positive active material, the amount of the binder added is generally 1% to 30% by weight. For example, the binder may include at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM) rubber, styrene-butadiene rubber, fluororubber and its copolymer.

[0067] The conductive agent is usually added so that the conductive agent accounts for 1% to 30% by weight of the total weight of the mixture containing the positive electrode active material. The conductive agent is not particularly limited as long as the conductive agent exhibits high conductivity without causing any chemical changes in the battery to which the conductive agent is applied. For example, as the conductive agent, graphite such as natural graphite or artificial graphite; carbon black such as ethylene black, acetylene black, Ketjen black, channel black, furnace black, lamp black or thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as fluorocarbon powders, aluminum powders or nickel powders; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives; graphene; or carbon nanotubes.

[0068] Fillers are optional components used to suppress electrode expansion. There are no specific limitations on fillers, as long as they are made of a fibrous material and do not cause chemical changes in the battery to which they are applied. For example, fillers can be polyolefin-based polymers such as polyethylene or polypropylene, or fibrous materials such as glass fiber or carbon fiber.

[0069] In a specific example, the negative electrode may be composed of only the negative electrode current collector without including the negative electrode mixture layer.

[0070] The negative electrode current collector is generally manufactured to have a thickness of 3 μm to 500 μm. There is no particular limitation on the negative electrode current collector as long as the negative electrode current collector exhibits high conductivity and does not cause any chemical changes in the battery to which the negative electrode current collector is applied. For example, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium or sintered carbon. Alternatively, the negative electrode current collector may be made of copper or stainless steel whose surface is treated with carbon, nickel, titanium or silver, or an aluminum-cadmium alloy. In addition, the negative electrode current collector may be formed with a micro-concave-convex pattern on its surface in the same manner as the positive electrode current collector to improve the binding force of the negative electrode active material. The negative electrode current collector may be constructed in any of various forms, such as a film, a sheet, a foil, a mesh, a porous body, a foam body and a non-woven fabric body.

[0071] In one embodiment, the negative electrode may include a negative electrode current collector and lithium metal formed on at least one surface of the negative electrode current collector by coating. The method of adding the lithium metal is not particularly limited. For example, the lithium metal may be added using a deposition method selected from the group consisting of thermal deposition, electron beam deposition, chemical vapor deposition, and physical vapor deposition.

[0072] Figure 2 It is a cross-sectional view of the solid electrolyte layer and the negative electrode in the all-solid-state battery of the present invention.

[0073] refer to Figure 2 , the solid electrolyte layer 220 is provided on one surface of the negative electrode 240. The solid electrolyte layer 220 is configured to have a double-layer structure including a first solid electrolyte layer 221 and a second solid electrolyte layer 222.

[0074] First solid electrolyte layer 221 includes binder 230 , while second solid electrolyte layer 222 does not. Second solid electrolyte layer 222 is disposed to face negative electrode 240 . Solid electrolyte particles 210 located on the surface of second solid electrolyte layer 222 are in contact with negative electrode 240 .

[0075] The binder plays a role in ensuring the bonding between the solid electrolyte particles and the bonding with the electrode, however, the binder may reduce the mobility of lithium ions. In particular, if Figure 1 The binder at the interface between the second solid electrolyte layer 222 and the negative electrode 240 as shown in the solid electrolyte layer and the negative electrode causes lithium plating to occur only on a local area of ​​the negative electrode surface, which easily generates lithium nuclei and increases the possibility of lithium dendrite formation.

[0076] Therefore, in the present invention, the second solid electrolyte layer in contact with the negative electrode is constructed without a binder, wherein the solid electrolyte particles in the outermost layer of the second solid electrolyte layer facing the negative electrode can directly contact the negative electrode. This increases the contact surface between the negative electrode and the solid electrolyte particles. In other words, as indicated by the arrows, lithium can move from all the solid electrolyte particles in the outermost layer to the negative electrode 240.

[0077] In the above structure, the occurrence of lithium dendrites is suppressed, thereby reducing the occurrence of short circuit in the all-solid-state battery.

[0078] For example, the binder may include at least one selected from the group consisting of polytetrafluoroethylene, polyethylene oxide, polyethylene glycol, polyacrylonitrile, polyvinyl chloride, polymethyl methacrylate, polypropylene oxide, polyphosphazene, polysiloxane, polydimethylsiloxane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE), polyvinylidene fluoride-tetrafluoroethylene copolymer (PVDF-TFE), polyvinylene carbonate, polyvinyl pyrrolidone, styrene-butadiene rubber, nitrile rubber and hydrogenated nitrile rubber.

[0079] The binder may be contained in the first solid electrolyte layer at 0.2 to 15 wt %, specifically 1 to 10 wt %, more specifically 1 to 5 wt % based on the weight of the total solid components contained in the first solid electrolyte layer.

[0080] If the binder content is less than 0.2 wt%, the bonding force between the solid electrolyte particles is low, making it difficult to form a solid electrolyte layer, and short circuits may easily occur, which is undesirable. If the binder content is greater than 15 wt%, the ionic conductivity may be greatly reduced, which is also undesirable.

[0081] Considering the fact that the binder is used to ensure the bonding force between solid electrolyte particles in the solid electrolyte layer 220, in order to ensure the shape stability of the solid electrolyte layer, the thickness of the first solid electrolyte layer including the binder may be equal to or greater than that of the second solid electrolyte layer.

[0082] For example, the thickness of the first solid electrolyte layer may be 100% to 1000% of the thickness of the second solid electrolyte layer, specifically greater than 100% to 500% of the thickness of the second solid electrolyte layer.

[0083] In addition, if the total thickness of the solid electrolyte layer is too large, resistance may increase, and if the total thickness of the solid electrolyte layer is too small, low strength and insulation may become problems. Therefore, the total thickness of the solid electrolyte layer may be 20 μm to 100 μm.

[0084] In one specific example, the minimum thickness of the first solid electrolyte layer may be 10 μm, and the minimum thickness of the second solid electrolyte layer may be 10 μm. That is, if the second solid electrolyte layer is thicker than the first solid electrolyte layer, a favorable effect can be achieved in terms of ensuring ion conductivity, but the adhesion of the solid electrolyte layer is low, and thus handling of the solid electrolyte layer may be difficult, which is undesirable.

[0085] The first solid electrolyte layer and the second solid electrolyte layer serve as an ion transport path between the positive electrode and the negative electrode. In order to prevent a decrease in ionic conductivity, the first solid electrolyte layer and the second solid electrolyte layer can be fully adhered to each other across the entire interface between them.

[0086] In a specific example, the first solid electrolyte layer and the second solid electrolyte layer may have the same components except for the binder.

[0087] For example, the solid electrolytes contained in the first solid electrolyte layer and the second solid electrolyte layer may be identical in kind to each other, and each solid electrolyte may be any one selected from the group consisting of a sulfide-based solid electrolyte, an oxide-based solid electrolyte, and a polymer-based solid electrolyte.

[0088] The sulfide-based solid electrolyte may be a compound containing sulfur atoms (S), exhibiting ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and exhibiting electronic insulation. Preferably, the sulfide-based solid electrolyte contains at least Li, S, and P as elements and exhibits lithium ion conductivity; however, depending on the purpose or circumstances, elements other than Li, S, and P may be included.

[0089] Specifically, as sulfide-based inorganic solid electrolytes, Li6PS5Cl, Li2S-P2S5, Li2S-P2S5-LiCl, Li2S-P2S5-H2S, Li2S-P2S5-H2S-LiCl, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2SLi2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SiS2-LiCl, Li2S-P2S5-SnS, Li 2S-P2S5-Al2S3, Li2S-GeS2, Li2S-GeS2-ZnS, Li2S-Ga2S3, Li2S-GeS2-Ga2S3, Li2S-GeS2-P2S5, Li2S-GeS2-Sb2S5, Li2S-GeS2-Al2S3, Li2S- SiS2, Li2S-Al2S3, Li2S-SiS2-Al2S3, Li2S-SiS2-P2S5, Li2S-SiS2-P2S5-LiI, Li2S-SiS2-LiI, Li2S-SiS2-Li4SiO4, Li2S-SiS2-Li3PO4, or Li 10 GeP2S 12 .

[0090] As a method for synthesizing sulfide-based inorganic solid electrolyte materials, an amorphization method can be used. Examples of amorphization methods include mechanical grinding, solution methods, and melting and rapid cooling methods. Since processing can be performed at room temperature (25°C), the manufacturing process can be simplified.

[0091] The oxide-based solid electrolyte may be a compound containing oxygen atoms (O), exhibiting ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and exhibiting electronic insulation.

[0092] As the oxide-based solid electrolyte, for example, Li xa La ya TiO3 (xa=0.3 to 0.7 and ya=0.3 to 0.7) (LLT), Li xb La yb Zr zb M bb mb O nb (Among them, M bbis at least one of Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, and Sn, xb satisfies 5 ≤ xb ≤ 10, yb satisfies 1 ≤ yb ≤ 4, zb satisfies 1 ≤ zb ≤ 4, mb satisfies 0 ≤ mb ≤ 2, and nb satisfies 5 ≤ nb ≤ 20), Li xc B yc M cc zc O nc (where M cc is at least one of C, S, Al, Si, Ga, Ge, In, and Sn, xc satisfies 0 ≤ xc ≤ 5, yc satisfies 0 ≤ yc ≤ 1, zc satisfies 0 ≤ zc ≤ 1, and nc satisfies 0 ≤ nc ≤ 6), Li xd (Al, Ga) yd (Ti, Ge) zd Si ad P md O nd (where 1 ≤ xd ≤ 3, 0 ≤ yd ≤ 1, 0 ≤ zd ≤ 2, 0 ≤ ad ≤ 1, 1 ≤ md ≤ 7, and 3 ≤ nd ≤ 13), Li (3-2xe) M ee xe D ee O (where xe represents a number from 0 to 0.1, M ee represents a divalent metal atom, and D ee represents a halogen atom or a combination of two or more halogen atoms), Li xf Si yf O zf (1 ≤ xf ≤ 5, 0 < yf ≤ 3, and 1 ≤ zf ≤ 10), Li xg S yg O zg (1 ≤ xg ≤ 3, 0 < yg ≤ 2, and 1 ≤ zg ≤ 10), Li3BO3 - Li2SO4, Li2O - B2O3 - P2O5, Li2O - SiO2, Li6BaLa2Ta2O 12 、Li3PO (4-3 / 2w) N w (w < 1), Li having a lithium superionic conductor (LISICON) - type crystal structure 3.5 Zn 0.25 GeO4, La having a perovskite - type crystal structure 0.55 Li 0.35 TiO3, LiTi2P3O having a sodium superionic conductor (NASICON) - type crystal structure 12 、Li 1+xh+yh (Al, Ga) xh [[ID=6�]](Ti, Ge) 2-xh Si yh P3-yh O 12 (where 0≤xh≤1 and 0≤yh≤1), or Li7La3Zr2O having a garnet crystal structure 12 (LLZ). Alternatively, a phosphorus compound including Li, P, and O may be used. For example, lithium phosphate (Li3PO4), LiPON in which a portion of the oxygen in lithium phosphate is replaced by nitrogen, or LiPOD may be used. 1 (D 1 is at least one selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Ag, Ta, W, Pt and Au. Alternatively, LiA 1 ON(A 1 is at least one selected from Si, B, Ge, Al, C and Ga).

[0093] The polymer-based solid electrolyte may be a solid polymer electrolyte formed by adding a polymer resin to an independently solvated lithium salt, or a polymer gel electrolyte formed by impregnating a polymer resin with an organic electrolyte solution containing an organic solvent and a lithium salt.

[0094] Solid polymer electrolyte is not particularly limited, as long as solid polymer electrolyte is made of, for example, an ion-conductive polymer material and is generally used as a solid electrolyte material for all-solid-state batteries. Examples of solid polymer electrolytes may include polyether polymers, polycarbonate polymers, acrylic polymers, polysiloxane polymers, phosphazene polymers, polyethylene oxide, polyethylene derivatives, alkylene oxide derivatives, phosphate polymers, poly-stirred lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ionic dissociation groups. Alternatively, solid polymer electrolyte may include branched copolymers, comb-like polymer resins, and cross-linked polymer resins formed by copolymerizing an amorphous polymer (such as polymethyl methacrylate (PMMA), polycarbonate, polysiloxane, and / or phosphazene) as a comonomer in the main chain of polyethylene oxide (PEO) as a polymer resin.

[0095] The polymer gel electrolyte includes an organic electrolyte containing a lithium salt and a polymer resin, wherein the content of the organic electrolyte may be 60 to 400 parts by weight based on the weight of the polymer resin. Although the polymer resin used in the polymer gel electrolyte is not limited to a specific component, it may include, for example, polyvinyl chloride (PVC)-based resins, polymethyl methacrylate (PMMA)-based resins, polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP).

[0096] The present invention provides a battery module including the all-solid-state battery as a unit cell, and the battery module can be used as an energy source for medium and large-sized equipment requiring high-temperature stability, long cycle characteristics, and high capacity characteristics.

[0097] Examples of medium and large-sized equipment include power tools driven by battery-powered motors, electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters), electric golf carts, and energy storage systems. However, the present invention is not limited thereto.

[0098] Hereinafter, the present invention will be described with reference to the following examples. These examples are provided only to facilitate easier understanding of the present invention and should not be construed as limiting the scope of the present invention.

[0099] <Production Example 1>

[0100] To manufacture a solid electrolyte layer, argyrodite (Li6PS5Cl) as a solid electrolyte and polytetrafluoroethylene as a binder were dispersed in anisole at a weight ratio of 95:5 and stirred to manufacture a first solid electrolyte layer slurry.

[0101] A polyethylene terephthalate (PET) release film was coated with the first solid electrolyte layer slurry, and the first solid electrolyte layer slurry was dried at 100° C. for 12 hours under vacuum to manufacture a first solid electrolyte layer having a thickness of 50 μm.

[0102] Argentite, a solid electrolyte, was dispersed and stirred in anisole to produce a second solid electrolyte layer slurry. A polyethylene terephthalate release film was coated with the second solid electrolyte layer slurry and dried at 100°C under vacuum for 12 hours to produce a second solid electrolyte layer with a thickness of 30 μm.

[0103] The second solid electrolyte layer is stacked on one surface of the first solid electrolyte layer to produce a solid electrolyte layer.

[0104] <Production Example 2>

[0105] A solid electrolyte layer was manufactured using the same method as in Manufacturing Example 1, except that, unlike in Manufacturing Example 1, the first solid electrolyte layer was manufactured to have a thickness of 30 μm.

[0106] <Production Example 3>

[0107] A solid electrolyte layer composed only of the first solid electrolyte layer having a thickness of 50 μm produced according to Production Example 1 was produced.

[0108] <Reference example>

[0109] Instead of separately manufacturing the solid electrolyte layer, argyrodite powder was filled in a Ti mold, and the ionic conductivity of the argyrodite powder was measured.

[0110] <Experimental Example 1> Ionic Conductivity of Solid Electrolyte Layer

[0111] In order to measure the ionic conductivity of each solid electrolyte layer manufactured according to Manufacturing Examples 1 to 3 and the argyrodite powder of the reference example, the solid electrolyte layer was placed between Ni current collectors, the solid electrolyte layer and the Ni current collector were placed in an aluminum bag, and the aluminum bag was sealed under a vacuum state to manufacture an all-solid-state battery.

[0112] The all-solid-state battery was fixed on a fixture, a pressure of 10 MPa was applied, and the ionic conductivity was measured using impedance spectroscopy. The results are shown in Table 1 below.

[0113] [Table 1]

[0114] Ionic conductivity (mS / cm) Production Example 1 0.6 Production Example 2 0.7 Production Example 3 0.4 Reference Example 2.0

[0115] Referring to Table 1 above, it can be seen that the measured ionic conductivity of the argyrodite of the reference example is 2.0 mS / cm, which is high, while the ionic conductivity of each of Manufacturing Examples 1 to 3 including the first solid electrolyte layer containing a binder is reduced.

[0116] This is because a binder added to impart adhesion between argyrodite particles during the production of the solid electrolyte is interposed between the argyrodite particles, thereby reducing ion conductivity.

[0117] The solid electrolytes of each of Production Examples 1 and 2 including the second solid electrolyte layer containing no binder exhibited higher ion conductivity than the solid electrolyte of Production Example 3 composed only of the first solid electrolyte layer containing a binder.

[0118] Therefore, in order to minimize the decrease in ionic conductivity, in particular to increase the contact between the negative electrode and the solid electrolyte layer at the interface between the negative electrode and the solid electrolyte layer where Li plating / stripping occurs during charge and discharge, it is preferred to provide a first solid electrolyte layer containing a binder and a second solid electrolyte layer without a binder at the same time.

[0119] <Example 1>

[0120] In order to manufacture the positive electrode for all-solid-state batteries, LiNi 0.8 Co 0.1 Mn 0.1O2, argyrodite (Li6PS5Cl) as a solid electrolyte, furnace black as a conductive agent, and polytetrafluoroethylene as a binder were dispersed in anisole at a weight ratio of 77.5:19.5:1.5:1.5 and stirred to produce a positive electrode slurry. This positive electrode slurry was coated on an aluminum current collector with a thickness of 14 μm by doctor blade coating and dried at 100°C for 12 hours under vacuum to produce a positive electrode.

[0121] To produce an all-solid-state battery anode consisting of a coating layer and an ion transport layer, Ag was sputtered onto a 10 μm-thick nickel current collector to a size of 30 nm, forming a coating layer consisting of an Ag layer. Subsequently, a slurry of a mixture of acetylene black and polyvinylidene fluoride in a weight ratio of 97:3 was applied to the Ag layer to form an ion transport layer, and the ion transport layer was dried to produce an anode with a multilayer structure.

[0122] To manufacture a solid electrolyte layer, argyrodite (Li6PS5Cl) as a solid electrolyte and polytetrafluoroethylene as a binder were dispersed in anisole at a weight ratio of 95:5 and stirred to manufacture a first solid electrolyte layer slurry.

[0123] The first solid electrolyte layer slurry was coated on a polyethylene terephthalate (PET) release film and dried at 100° C. for 12 hours under a vacuum state to form a first solid electrolyte layer with a thickness of 50 μm.

[0124] Argentinite, a solid electrolyte, was dispersed and stirred in anisole to produce a second solid electrolyte layer slurry. The slurry was then coated onto a polyethylene terephthalate release film and dried at 100°C for 12 hours under vacuum to form a 30 μm thick second solid electrolyte layer.

[0125] The second solid electrolyte layer is stacked on one surface of the first solid electrolyte layer to produce a solid electrolyte layer.

[0126] The solid electrolyte layer is placed between the positive electrode and the negative electrode so that the second solid electrolyte layer faces the negative electrode and the first solid electrolyte layer faces the positive electrode, the positive electrode, the solid electrolyte layer and the negative electrode are placed in an aluminum bag, and the aluminum bag is hermetically sealed to manufacture an all-solid-state battery.

[0127] <Example 2>

[0128] An all-solid-state battery was manufactured using the same method as in Example 1, except that, unlike in Example 1, the thickness of the first solid electrolyte layer was 30 μm.

[0129] <Comparative Example 1>

[0130] An all-solid-state battery was manufactured using the same method as in Example 1, except that, unlike in Example 1, the solid electrolyte layer consisted of only a first solid electrolyte layer having a thickness of 50 μm.

[0131] <Comparative Example 2>

[0132] An all-solid-state battery was manufactured using the same method as in Example 1, except that, unlike in Example 1, the solid electrolyte layer consisted only of a second solid electrolyte layer having a thickness of 30 μm.

[0133] <Comparative Example 3>

[0134] An all-solid-state battery was manufactured using the same method as in Example 1, except that, unlike in Example 1, a solid electrolyte layer was placed between the positive electrode and the negative electrode so that the first solid electrolyte layer faced the negative electrode and the second solid electrolyte layer faced the positive electrode.

[0135] <Experimental Example 2>

[0136] All-solid-state batteries manufactured according to Example 1, Example 2, and Comparative Examples 1 to 3 were prepared, charged to 4.25 V at 0.05 C and discharged to 3.0 V at 0.05 C in a constant current-constant voltage mode at 60° C., and the initial charge and discharge capacities and their efficiencies were measured.

[0137] Furthermore, in order to evaluate the life characteristics of the all-solid-state battery, five charging and discharging cycles were performed in a voltage range of 4.25 V to 3.0 V under 0.1 C charge / 0.1 C discharge conditions.

[0138] The measured initial charge capacity, initial discharge capacity, charge and discharge efficiency, and retention rate of each all-solid-state battery are shown in Table 2 below.

[0139] In Table 2 below, the initial charge capacity and the initial discharge capacity represent the charge capacity and the discharge capacity at the first cycle, respectively, and the charge and discharge efficiency represents the ratio of the discharge capacity to the charge capacity measured at the first cycle. Also, in Table 2 below, the retention rate represents the ratio of the discharge capacity measured at the fifth cycle to the discharge capacity measured at the first cycle.

[0140] [Table 2]

[0141]

[0142] Referring to Table 2 above, it can be seen that the all-solid-state batteries of Examples 1 and 2 have higher charge and discharge efficiency than the all-solid-state battery of Comparative Example 1. The reason for this appears to be that, as can be seen from Experimental Example 1 above, the ion conductivity of the solid electrolyte layer including the first solid electrolyte layer and the second solid electrolyte layer is higher than the ion conductivity of the solid electrolyte layer consisting only of the first solid electrolyte layer.

[0143] In the all-solid-state battery of Comparative Example 2 in which the solid electrolyte layer consists only of a second solid electrolyte layer containing no adhesive, the strength of the solid electrolyte layer is low, which poses great difficulties in manufacturing the all-solid-state battery, and a short circuit occurs during initial charging, making evaluation impossible.

[0144] When comparing the life characteristics, the retention rate of each of Example 1 and Example 2 is higher than that of Comparative Example 1.

[0145] Moreover, when Example 1 and Example 2 are compared with Comparative Example 3, in Example 1 and Example 2, since the second solid electrolyte layer without a binder is arranged to face the negative electrode, the contact between the solid electrolyte particles and the negative electrode is increased, thereby delaying the formation of lithium dendrites, and thus the retention rate can be maintained higher.

[0146] As described above, the all-solid-state battery of the present invention can include a structure in which the contact area between the solid electrolyte layer and the negative electrode is increased, thereby suppressing a decrease in ion conductivity, and thus providing an all-solid-state battery with improved life characteristics.

[0147] Those skilled in the art to which the present invention pertains will appreciate that, based on the above description, various applications and modifications are possible within the scope of the present invention.

[0148] (Description of Reference Signs)

[0149] 110, 210: Solid electrolyte particles

[0150] 120, 220: solid electrolyte layer

[0151] 130, 230: Adhesive

[0152] 140, 240: negative electrode

[0153] 221: First solid electrolyte layer

[0154] 222: Second solid electrolyte layer.

Claims

1. An all-solid-state battery, comprising: positive electrode; negative electrode; as well as A solid electrolyte disposed between the positive electrode and the negative electrode, wherein The solid electrolyte is composed of a first solid electrolyte layer containing a binder and a second solid electrolyte layer not containing a binder, and A second solid electrolyte layer faces the negative electrode; Wherein, the negative electrode does not include a negative electrode mixture layer; wherein the solid electrolyte particles located on the surface of the second solid electrolyte layer are in contact with the negative electrode; The solid electrolyte contained in the second solid electrolyte layer includes any one selected from the group consisting of a sulfide-based solid electrolyte and an oxide-based solid electrolyte.

2. The all-solid-state battery according to claim 1, wherein: The binder is at least one selected from the group consisting of polytetrafluoroethylene, polyethylene oxide, polyethylene glycol, polyacrylonitrile, polyvinyl chloride, polymethyl methacrylate, polypropylene oxide, polyphosphazene, polysiloxane, polydimethylsiloxane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE), polyvinylidene fluoride-tetrafluoroethylene copolymer (PVDF-TFE), polyvinylene carbonate, polyvinyl pyrrolidone, styrene-butadiene rubber, nitrile rubber and hydrogenated nitrile rubber.

3. The all-solid-state battery according to claim 1, wherein: The first solid electrolyte layer and the second solid electrolyte layer have the same components except for the binder.

4. The all-solid-state battery according to claim 1, wherein: The thickness of the first solid electrolyte layer is equal to or greater than the thickness of the second solid electrolyte layer.

5. The all-solid-state battery according to claim 1, wherein: The binder is contained in the first solid electrolyte layer in an amount of 0.2 wt % to 15 wt % based on the weight of the total solid components contained in the first solid electrolyte layer.

6. The all-solid-state battery according to claim 1, wherein: The first solid electrolyte layer and the second solid electrolyte layer are in a state of being adhered to each other.

7. The all-solid-state battery according to claim 1, wherein: The thickness of the first solid electrolyte layer is greater than 100% to 500% of the thickness of the second solid electrolyte layer.

8. The all-solid-state battery according to claim 1, wherein: The negative electrode includes a coating layer and an ion transport layer.

9. The all-solid-state battery according to claim 1, wherein: The solid electrolyte contained in the first solid electrolyte layer includes any one selected from the group consisting of a sulfide-based solid electrolyte, an oxide-based solid electrolyte, and a polymer-based solid electrolyte. 10 . A battery module comprising the all-solid-state battery according to claim 1 as a unit cell.

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