All-solid-state battery including two solid electrolyte layers and method for manufacturing the same

Abstract

The present invention relates to an all-solid-state battery including a positive electrode, a negative electrode, and a solid electrolyte interposed between the positive electrode and the negative electrode, the solid electrolyte comprising a first solid electrolyte layer containing a binder and a second solid electrolyte layer not containing a binder, the second solid electrolyte layer facing the negative electrode, and the all-solid-state battery having improved safety and low resistance.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0187611 filed on Dec. 24, 2021, and all contents disclosed in the documents of the Korean patent application are incorporated herein by reference in their entirety.

[0002] The present invention relates to an all-solid-state battery including two solid electrolyte layers and a method for manufacturing the same. Specifically, the present invention relates to an all-solid-state battery including two solid electrolyte layers and a method for manufacturing the same, which reduce the risk of short circuit of the all-solid-state battery by increasing the adhesion surface between the solid electrolyte layer and the negative electrode.

Background Art

[0003] Rechargeable lithium secondary batteries, which have a high energy density, not only can significantly reduce the use of fossil fuels but also do not generate by-products due to energy use, and thus are attracting attention as a new environmentally friendly energy source.

[0004] The lithium secondary battery is attracting attention not only as an energy source for wearable devices or portable devices but also for devices with high output and high energy density such as electric vehicles. Therefore, the research and development speed for increasing the operating voltage and energy density of lithium secondary batteries is accelerating.

[0005] As a type of the lithium secondary battery, a lithium-ion secondary battery including an electrolyte solution and a separator has drawbacks such as a high risk of electrolyte solution leakage and fire. As an alternative to this, an all-solid-state battery using a non-flammable solid as an electrolyte to reduce the risk of fire and explosion has been proposed.

[0006] The all-solid-state battery not only improves safety but also includes a solid electrolyte, so that the migration speed of lithium ions is fast, and the energy density increases by reducing the thickness of the negative electrode.

[0007] As a means of increasing the energy density of all-solid-state batteries, a form of the negative electrode composed only of a current collector without a negative electrode mixture layer has been proposed.

[0008] When such an all-solid-state battery is charged, lithium is deposited (plating) on the negative electrode current collector at the portion where the negative electrode current collector and the solid electrolyte layer are in contact. When the all-solid-state battery is discharged, the lithium deposited on the negative electrode current collector is desorbed (stripping). In this way, the size of the lithium deposited on the negative electrode current collector gradually increases by repeated charge and discharge, and lithium dendrites can grow. The lithium dendrites may cause a short circuit or a decrease in capacity of the battery.

[0009] That is, the smaller the contact surface between the negative electrode current collector and the solid electrolyte layer, the more locally lithium deposition (plating) occurs, so the possibility of lithium dendrite growth can be increased.

[0010] In this regard, FIG. 1 is a cross-sectional view of the solid electrolyte layer and the negative electrode of a conventional all-solid-state battery for high energy density.

[0011] Referring to FIG. 1, a solid electrolyte layer 120 is formed on one surface of a negative electrode 140. The solid electrolyte layer 120 is composed of solid electrolyte particles 110 bound by a binder 130 and is disposed on one surface of the negative electrode 140.

[0012] Lithium that has moved to the negative electrode 140 through the solid electrolyte particles 110 adheres to the surface of the negative electrode 140, but the binder 130 between the solid electrolyte particles 110 and the negative electrode 140 prevents lithium from moving to the negative electrode.

[0013] In FIG. 1, among the solid electrolyte particles in contact with the negative electrode, those through which lithium can move are indicated by arrows, and the solid electrolyte particles whose lithium movement paths are blocked by the binder 130 are not indicated by arrows.

[0014] Thus, if lithium cannot move or the migration speed decreases due to the binder, the resistance of the all-solid-state battery will increase.

[0015] Therefore, it is necessary to develop an all-solid-state battery with reduced resistance by increasing the contact area between the solid electrolyte layer and the negative electrode.

[0016] In the case of an all-solid-state battery to which a sulfide-based solid electrolyte is applied, in order to minimize the resistance of the solid electrolyte layer itself, there is a method of manufacturing it in a form in which the solid electrolyte layer is pressure-bonded without a binder. In such a case, since it is manufactured so that the thickness of the solid electrolyte layer becomes about several hundred micrometers, it is not a suitable form for manufacturing an all-solid-state battery for high energy density.

[0017] In this regard, Patent Document 1 relates to an all-solid-state battery in which an electrolyte layer is disposed between a positive electrode layer and a negative electrode layer, the electrolyte layer includes 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, by including a binder, can obtain the effect of ensuring the dispersing force of the sulfide-based solid electrolyte particles, and discloses that the thickness of the solid electrolyte layer can be reduced to reduce the resistance.

[0019] Patent Document 2 relates to an electrolyte layer for a pre-solid battery in which two or more electrolyte layers are laminated, and the two or more electrolyte layers have different binder contents. When applying the lamination method, it discloses that the interfacial resistance between the electrode layer and the electrolyte layer can be minimized by smoothly detaching the base material from the electrolyte layer and appropriately adjusting the thickness of the electrolyte layer.

[0020] However, Patent Document 1 and Patent Document 2 do not present a method for solving the problem that the resistance of the all-solid-state battery increases due to the binder contained in the solid electrolyte layer.

Prior Art Documents

Patent Document

[0021]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0022] The present invention is for solving the above problems, and aims to provide a all-solid-state battery including two types of solid electrolyte layers and a manufacturing method thereof, so as to prevent the growth of lithium dendrites on the surface of the negative electrode and ensure the safety of the all-solid-state battery.

Means for Solving the Problems

[0023] The all-solid-state battery according to the present invention for achieving such an object includes a positive electrode, a negative electrode, and a solid electrolyte interposed between the positive electrode and the negative electrode, and 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 the second solid electrolyte layer can face the negative electrode.

[0024] The binder can be one or more 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), polyvinylidene carbonate, polyvinylpyrrolidinone, styrene - butadiene rubber, nitrile - butadiene rubber, and Hydrogenated nitrile butadiene rubber.

[0025] The remaining constituent components of the first solid electrolyte layer and the second solid electrolyte layer excluding the binder may be the same as each other.

[0026] The thickness of the first solid electrolyte layer may be the same as or greater than the thickness of the second solid electrolyte layer.

[0027] The content of the binder contained in the first solid electrolyte layer can be 0.2% by weight to 15% by weight based on the weight of the total solid content contained in the first solid electrolyte layer.

[0028] The first solid electrolyte layer and the second solid electrolyte layer can be in an adhered state.

[0029] The negative electrode may not include a negative electrode mixture layer.

[0030] The negative electrode can include a coating layer and an ion conduction layer.

[0031] The solid electrolyte particles on the surface of the second solid electrolyte layer can contact the negative electrode.

[0032] The present invention provides a battery module including the all-solid-state battery as a unit cell.

[0033] The present invention provides a method for manufacturing the all-solid-state battery.

[0034] Specifically, it includes: (a) a step of manufacturing a first solid electrolyte layer slurry and a second solid electrolyte layer slurry; (b) a step of coating the first solid electrolyte layer slurry and the second solid electrolyte layer slurry on respective release films; (c) a step of drying the first solid electrolyte layer slurry coating layer and the second solid electrolyte layer slurry manufactured in step (b) to form a first solid electrolyte layer and a second solid electrolyte layer; (d) a step of laminating and pressing the first solid electrolyte layer and the second solid electrolyte layer so that they face each other; (e) a step of removing the release film to obtain a solid electrolyte layer; and (f) a step of assembling an all-solid-state battery by disposing the solid electrolyte layer between a positive electrode and a negative electrode, and the second solid electrolyte layer can be disposed so as to face the negative electrode.

[0035] Step (d) can be performed by a hydrostatic pressure pressing method.

[0036] The pressure during hydrostatic pressing can be 10 MPa to 100 MPa.

[0037] The temperature in the step (d) can be 5 °C to 150 °C.

[0038] The present invention can also be provided in a form in which various combinations of the means for solving the above problems are made.

Effects of the Invention

[0039] As described above, the all-solid-state battery according to the present invention can prevent local lithium plating from occurring on the surface of the negative electrode by increasing the contact surface at the interface between the solid electrolyte layer and the negative electrode.

[0040] Therefore, it is possible to suppress the growth of lithium dendrites on the surface of the negative electrode.

[0041] Therefore, as a result of reducing the risk of short circuit of the all-solid-state battery, the safety can be improved.

[0042] Also, by widely securing the lithium migration path, the resistance of the all-solid-state battery can be lowered.

Brief Description of the Drawings

[0043]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0044] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, in which a person having ordinary skill in the art to which the present invention pertains can easily carry out the present invention. However, in describing the operation principle of the preferred embodiment of the present invention in detail, detailed description of related well-known functions or configurations will be omitted if it is determined that such detailed description may unnecessarily obscure the gist of the present invention.

[0045] In addition, the same reference numerals are used throughout the drawings for parts having similar functions and actions. Throughout the specification, when a part is said to be connected to another part, this includes not only the case where the part is directly connected to another part, but also the case where the part is indirectly connected via another element between the two parts. In addition, when a part includes a certain component, it does not mean that the other component is excluded, but that the part may further include the other component, unless otherwise specified.

[0046] Furthermore, descriptions that limit or add specific elements are applicable to all inventions and are not limited to a particular invention unless otherwise specified.

[0047] Furthermore, throughout the description of the present invention and the claims, the singular includes the plural unless otherwise stated.

[0048] In addition, throughout the description of the present invention and the claims, unless otherwise specified, "or" includes "and." Therefore, "including A or B" means three cases: including A, including B, or including both A and B.

[0049] The invention will now be explained with reference to the drawings and in conjunction with detailed embodiments.

[0050] The all-solid-state battery according to the present invention includes a positive electrode, a negative electrode, and a solid electrolyte interposed between the positive electrode and the negative electrode, and the solid electrolyte may be composed of a first solid electrolyte layer containing a binder and a second solid electrolyte layer not containing a binder, and the second solid electrolyte layer may face the negative electrode.

[0051] The positive electrode is manufactured, for example, by applying a positive electrode mixture containing a positive electrode active material onto a positive electrode current collector and then drying it. The positive electrode mixture may further selectively contain a binder, a conductive material, a filler, etc., if necessary.

[0052] The positive electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or a material obtained by surface-treating the surface of aluminum or stainless steel with carbon, nickel, titanium, silver, etc. can be used. In addition, the positive electrode current collector can also form fine irregularities on its surface to enhance the adhesive force of the positive electrode active material, and various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven fabric bodies, etc. are possible.

[0053] The positive electrode active material is a substance that can cause an electrochemical reaction, and can contain at least one of the positive electrode active materials represented by the following formulas 1 to 3.

[0054] Li a Co 1-x M x O2(1) Li a Mn 2-y M y O4(2) Li a Fe 1-z M z PO4(3)

[0055] In the above formula, 0.8 ≦ a ≦ 1.2; 0 ≦ x ≦ 0.9; 0 ≦ y ≦ 0.6, 0 ≦ z ≦ 0.5, M is one or more selected from the group consisting of Ti, Cd, Cu, Cr, Mo, Mg, Al, Ni, Nb, Mn, V, and Zr.

[0056] That is, the positive electrode active material can contain one or more substances selected from the group consisting of a layered lithium metal oxide represented by Formula 1, a spinel-structured lithium manganese-based oxide represented by Formula 2, and an olivine-structured lithium-containing phosphate represented by Formula 3.

[0057] The layered lithium metal oxide is not limited to its type, and examples thereof include one or more 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 substances in which other elements are substituted or doped into these.

[0058] The lithium nickel-cobalt-manganese oxide is Li 1+z Ni b Co C Mn 1-(b+c+d) M d O (2-e) A e (where -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) and can be expressed.

[0059] The spinel-structured lithium manganese-based oxide is also not limited to its type, and examples thereof include one or more selected from the group consisting of lithium manganese oxide, lithium nickel manganese oxide, and substances in which other elements are substituted or doped into these.

[0060] In addition, the olivine-structured lithium-containing phosphate is also not limited to its type, and examples thereof include lithium iron phosphate and those in which other elements are substituted or doped into this.

[0061] The other element(s) may be one or more elements selected from the group consisting of Al, Mg, Mn, Ni, Co, Cr, V, and Fe.

[0062] The binder is a component that helps bind the active material and the conductive material and bind to the current collector. Usually, it is added in an amount of 1 wt% to 30 wt% based on the total weight of the mixture containing the positive electrode active material. Examples of such binders include one or more 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 rubber (EPDM rubber), styrene-butylene rubber, fluorine rubber, and copolymers thereof.

[0063] The conductive material is usually added in an amount of 1 wt% to 30 wt% based on the total weight of the mixture containing the positive electrode active material. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, graphite such as natural graphite and artificial graphite; carbon black such as ethylene black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, graphene, and carbon nanotubes can be used.

[0064] The filler is a component that suppresses the expansion of the electrode and can be selectively used. It is not particularly limited as long as it is a material that does not cause a chemical change in the battery. For example, polyolefin polymers such as polyethylene and polypropylene; fibrous substances such as glass fibers and carbon fibers are used.

[0065] In one specific example, the negative electrode may not include a negative electrode mixture layer and may be composed of only a negative electrode current collector.

[0066] The negative electrode current collector is generally manufactured to have a thickness of 3 μm to 500 μm. Such a negative electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, or a surface-treated product of copper or stainless steel with carbon, nickel, titanium, silver, etc. on its surface, or an aluminum-cadmium alloy can be used. Similarly to the positive electrode current collector, fine irregularities can be formed on the surface to strengthen the binding force of the negative electrode active material, and various forms such as films, sheets, foils, nets, porous bodies, foams, and non-woven fabrics can be used.

[0067] In one specific example, the negative electrode can be composed of a negative electrode current collector and lithium metal coated on at least one surface of the negative electrode current collector. The method of adding the lithium metal is not particularly limited. For example, it can be added by a vapor deposition method selected from the group consisting of thermal vapor deposition, E-beam (e-beam) vapor deposition, chemical vapor deposition, and physical vapor deposition.

[0068] Alternatively, the negative electrode can have a multilayer structure including a coating layer and an ion transfer layer formed on the negative electrode current collector. As the coating layer, for example, a silver (Ag) coating layer can be formed, and as the ion transfer layer, for example, it can include a binder such as electrically conductive acetylene black or polyvinylidene fluoride.

[0069] FIG. 2 is a cross-sectional view of a solid electrolyte layer and a negative electrode in the all-solid-state battery according to the present invention.

[0070] Referring to FIG. 2, a solid electrolyte layer 220 is provided on one surface of the negative electrode 240. The solid electrolyte layer 220 has a two-layer laminated structure composed of a first solid electrolyte layer 221 and a second solid electrolyte layer 222.

[0071] The first solid electrolyte layer 221 contains a binder 230, and the second solid electrolyte layer 222 does not contain a binder and is arranged to face the negative electrode 240. Therefore, the solid electrolyte particles 210 on the surface of the second solid electrolyte layer 222 come into contact with the negative electrode 240.

[0072] While the binder secures the binding force of the solid electrolyte particles and functions to improve the adhesive force with the electrode, it may also reduce the mobility of lithium ions. In particular, as in the solid electrolyte layer and the negative electrode shown in FIG. 1, if lithium cannot move to the negative electrode due to the binder 130 at the contact surface between the solid electrolyte layer 120 and the negative electrode 140, lithium plating occurs only in a part where lithium can move. In this way, lithium nuclei are formed where lithium plating occurs, increasing the possibility of the generation of lithium dendrites.

[0073] Therefore, in the present invention, since the second solid electrolyte layer in contact with the negative electrode is configured not to contain a binder, all of the solid electrolyte particles 210 in the outermost layer facing the negative electrode in the second solid electrolyte layer can be in direct contact with the negative electrode. Thus, the contact surface between the negative electrode 240 and the solid electrolyte particles 210 can be increased. That is, as indicated by the arrow, lithium can move from all of the solid electrolyte particles 210 in the outermost layer of the second solid electrolyte layer 222 to the negative electrode 240.

[0074] By having such a structure, the generation of lithium dendrites can be suppressed and the occurrence of a short circuit in the all-solid-state battery can be reduced.

[0075] The binder can include one or more selected from the group consisting of, for example, 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), polyvinylidene carbonate, polyvinylpyrrolidinone, styrene - butadiene rubber, nitrile - butadiene rubber, and Hydrogenated nitrile butadiene rubber.

[0076] The content of the binder included in the first solid electrolyte layer can be 0.2 wt% to 15 wt%, specifically 1 wt% to 10 wt%, and more specifically 1 wt% to 5 wt% based on the weight of the total solid content included in the first solid electrolyte layer.

[0077] When the content of the binder is less than 0.2% by weight, the binding force between the solid electrolyte particles becomes low, making it difficult to form a solid electrolyte layer and prone to short circuits. When it is more than 15% by weight, the ionic conductivity can be significantly reduced, which is not preferable.

[0078] Considering that the binder functions to ensure the binding force of the solid electrolyte particles, for the morphological safety of the solid electrolyte layer, the thickness of the first solid electrolyte layer 221 containing the binder can be the same as or thicker than the thickness of the second solid electrolyte layer 222.

[0079] For example, the thickness of the first solid electrolyte layer can be formed in the range of 100% or more to 1,000% or less based on the thickness of the second solid electrolyte layer, and specifically, it can be formed in the range of more than 100% to 500% or less.

[0080] Also, when the total thickness of the solid electrolyte layer is too thick, the resistance may increase, and when it is too thin, low strength and insulation may become problems. Therefore, the range of the total thickness of the solid electrolyte layer can be in the range of 20 μm to 100 μm.

[0081] In one specific example, the minimum thickness of the first solid electrolyte layer can be 10 μm, and the minimum thickness of the second solid electrolyte layer can be 10 μm. That is, when the second solid electrolyte layer is relatively thicker than the first solid electrolyte layer, an advantageous effect can be obtained in terms of ensuring ionic conductivity. However, it is not preferable because the adhesion force of the solid electrolyte layer may be weak and difficult to handle.

[0082] Since the first solid electrolyte layer and the second solid electrolyte layer function as an ion transfer path between the positive electrode and the negative electrode, in order to prevent the ionic conductivity from decreasing, they can be configured to be completely adhered to each other across the entire interface.

[0083] In one specific example, the first solid electrolyte layer and the second solid electrolyte layer can be configured such that the remaining components excluding the binder are the same as each other.

[0084] For example, the types of the solid electrolytes included in the first solid electrolyte layer and the second solid electrolyte layer are the same, and may be any one selected from the group consisting of sulfide-based solid electrolytes, oxide-based solid electrolytes, and polymer-based solid electrolytes.

[0085] The sulfide-based solid electrolyte may be a compound that contains a sulfur atom (S), has ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and has electron insulation. The sulfide-based solid electrolyte preferably contains at least Li, S, and P as elements and has lithium ion conductivity, but may contain elements other than Li, S, and P depending on the purpose or circumstances.

[0086] Specific examples of the sulfide-based inorganic solid electrolyte include, for example, Li6PS5Cl, Li2S-P2S5, Li2S-P2S5-LiCl, Li2S-P2S5-H2S, Li2S-P2S5-H2S-LiCl, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SiS2-LiCl, Li2S-P2S5-SnS, Li2S-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, and Li 10 GeP2S 12 and the like can be used.

[0087] As a method for synthesizing the sulfide-based inorganic solid electrolyte material, an amorphization method can be used. Examples of the amorphization method include a mechanical milling method, a solution method, or a melt quenching method. This is because processing at normal temperature (25 °C) becomes possible, simplifying the manufacturing process.

[0088] The oxide-based solid electrolyte may be a compound that contains oxygen atoms (O), has ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and has electron insulation.

[0089] As the oxide-based solid electrolyte, for example, Li xa La ya TiO3 (xa = 0.3 to 0.7, ya = 0.3 to 0.7) (LLT), Li xb La yb Zr zb M bb mb O nb (M bb is at least one element among Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, and Sn, 5 ≤ xb ≤ 10, 1 ≤ yb ≤ 4, 1 ≤ zb ≤ 4, 0 ≤ mb ≤ 2, 5 ≤ nb ≤ 20), Li xc B yc M cc zc O nc (M cc is at least one element among C, S, Al, Si, Ga, Ge, In, and Sn, 0 ≤ xc ≤ 5, 0 ≤ yc ≤ 1, 0 ≤ zc ≤ 1, 0 ≤ nc ≤ 6), Li xd (Al, Ga) yd (Ti, Ge) zd Si ad P md O nd (However, 1 ≤ xd ≤ 3, 0 ≤ yd ≤ 1, 0 ≤ zd ≤ 2, 0 ≤ ad ≤ 1, 1 ≤ md ≤ 7, 3 ≤ nd ≤ 13), Li (3-2xe) M ee xe D ee O (xe represents a number from 0 or more to 0.1 or less, M ee represents a divalent metal atom. D eerepresents a halogen atom or a combination of two or more halogen atoms), Li xf Si yf O zf (1 ≤ xf ≤ 5, 0 < yf ≤ 3, 1 ≤ zf ≤ 10), Li xg S yg O zg (1 ≤ xg ≤ 3, 0 < yg ≤ 2, 1 ≤ zg ≤ 10), Li3BO3 - Li2SO4, Li2O - B2O3 - P2O5, Li2O - SiO2, Li6BaLa2Ta2O 12 、Li3PO (4-3 / 2w) N w (where w < 1), Li having a LISICON (Lithium super ionic conductor) 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 NASICON (Natrium superionic conductor) type crystal structure 12 、Li 1+xh+yh (Al, Ga) xh (Ti, Ge) 2-xh Si yh P 3-yh O 12 (however, 0 ≤ xh ≤ 1, 0 ≤ yh ≤ 1), Li7La3Zr2O having a garnet type crystal structure 12 (LLZ), etc. can be mentioned. Alternatively, a phosphorus compound containing Li, P, and O can also be used. For example, lithium phosphate (Li3PO4), LiPON in which part of the oxygen in lithium phosphate is substituted with nitrogen, LiPOD 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, etc.) can be mentioned. Alternatively, LiA 1 ON (A 1 is at least one selected from Si, B, Ge, Al, C, and Ga, etc.) can also be used.

[0090] The polymer solid electrolyte can be a solid polymer electrolyte formed by adding a polymer resin to a solvated lithium salt independently, or a polymer gel electrolyte obtained by incorporating an organic electrolyte solution containing an organic solvent and a lithium salt into a polymer resin.

[0091] For example, the solid polymer electrolyte is an ion conductivity material and is not particularly limited as long as it is a polymer material commonly used as a solid electrolyte material for all-solid-state batteries. The solid polymer electrolyte can include, for example, polyether-based polymers, polycarbonate-based polymers, acrylate-based polymers, polysiloxane-based polymers, phosphazene-based polymers, polyethylene oxide, polyethylene derivatives, alkylene oxide derivatives, phosphate ester polymers, polyadipic lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, or polymers containing ionic dissociation groups. Alternatively, the solid polymer electrolyte is a polymer resin, and can include branched copolymers obtained by copolymerizing amorphous polymers such as polymethyl methacrylate (PMMA), polycarbonate, polysiloxane, and / or phosphazene as comonomers in a PEO (polyethylene oxide) main chain, comb-like polymer resins, and crosslinked polymer resins.

[0092] The polymer gel electrolyte contains an organic electrolyte solution containing a lithium salt and a polymer resin, and the organic electrolyte solution can contain 60 to 400 parts by weight based on the weight of the polymer resin. The polymer applied to the polymer gel electrolyte is not limited to specific components, and can include, for example, polyvinyl chloride (PVC), poly(methyl methacrylate) (PMMA), polyacrylonitrile (PAN), poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride - hexafluoropropylene) (PVDF - HFP), etc.

[0093] The manufacturing method of the all-solid-state battery according to the present invention includes: (a) manufacturing a first solid electrolyte layer slurry and a second solid electrolyte layer slurry; (b) coating the first solid electrolyte layer slurry and the second solid electrolyte layer slurry on respective release films; (c) drying the first solid electrolyte layer slurry coating layer and the second solid electrolyte layer slurry manufactured in the step (b) to form a first solid electrolyte layer and a second solid electrolyte layer; (d) laminating and pressing the first solid electrolyte layer and the second solid electrolyte layer so that they face each other; (e) removing the release film to obtain a solid electrolyte layer; and (f) assembling an all-solid-state battery by disposing the solid electrolyte layer between a positive electrode and a negative electrode, and the second solid electrolyte layer can be disposed to face the negative electrode.

[0094] The step (d) can be carried out by a hydrostatic pressure pressing method so as to adhere uniformly over the entire contact surface between the first solid electrolyte layer and the second solid electrolyte layer.

[0095] In this way, the pressure when pressing the first solid electrolyte layer and the second solid electrolyte layer by hydrostatic pressure can be in the range of 10 MPa to 100 MPa, specifically 20 MPa to 50 MPa. When the hydrostatic pressure is lower than 10 MPa, the adhesive force between the first solid electrolyte layer and the second solid electrolyte layer may be weak and layer separation may occur. When it is higher than 100 MPa, the solid electrolyte layer may become too hard and break, which is not preferable.

[0096] The temperature of the step (d) can be carried out within the range of 5°C to 150°C, specifically, it can be pressed at 25°C to 80°C.

[0097] When the temperature range is lower than 5°C, there is a problem that the pressing efficiency drops. When it is higher than 150°C, there are problems such as material deformation or decomposition, which is not preferable.

[0098] 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 devices that require high-temperature safety, long cycle characteristics, and large-capacity characteristics.

[0099] Examples of the medium and large-sized devices include power tools powered by battery motors; electric vehicles such as electric vehicles (EV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV); electric two-wheel vehicles including electric bicycles (E-bike) and electric scooters (Escooter); electric golf carts; power systems, etc., but are not limited thereto.

[0100] Hereinafter, embodiments of the present invention will be described with reference to examples, which are for easier understanding of the present invention and the scope of the present invention is not limited thereby.

[0101] <Production Example 1> To produce the solid electrolyte layer, a first solid electrolyte layer slurry was produced by dispersing argyrodite (Li6PS5Cl) as a solid electrolyte and polytetrafluoroethylene as a binder in anisole at a weight ratio of 95:5 and stirring.

[0102] After coating the first solid electrolyte layer slurry on a polyethylene terephthalate (PET) release film, it was vacuum dried at 100 °C for 12 hours to produce a first solid electrolyte layer with a thickness of 50 μm.

[0103] After manufacturing the second solid electrolyte layer slurry by dispersing argyrodite alone in anisole and stirring it as a solid electrolyte, coating this on a polyethylene terephthalate release film, and then drying it under vacuum at 100 °C for 12 hours, a second solid electrolyte layer with a thickness of 30 μm was manufactured.

[0104] The second solid electrolyte layer was laminated on one surface of the first solid electrolyte layer to manufacture a solid electrolyte layer.

[0105] <Production Example 2> A solid electrolyte layer was manufactured in the same manner as in Production Example 1, except that in Production Example 1, it was manufactured such that the thickness of the first solid electrolyte layer was 30 μm.

[0106] <Production Example 3> A solid electrolyte layer composed only of the first solid electrolyte layer with a thickness of 50 μm manufactured in Production Example 1 was manufactured.

[0107] <Reference Example> Without manufacturing a solid electrolyte layer separately, argyrodite powder was filled in a Ti mold and the ionic conductivity was measured.

[0108] <Experimental Example 1> Ionic Conductivity of Solid Electrolyte Layer To measure the ionic conductivity of the solid electrolyte layers manufactured in Production Examples 1 to 3 and the argyrodite powder in the reference example, a solid-state battery was manufactured by interposing the solid electrolyte layer between Ni current collectors and sealing it in an aluminum pouch under vacuum.

[0109] The all-solid-state battery was fastened to a jig, a pressure of 10 MPa was applied, the ionic conductivity was measured by impedance spectroscopy, and the results are shown in Table 1 below.

[0110]

Table 1

[0111] Referring to Table 1 above, although the ionic conductivity of the argyrodite itself in the reference example was measured as high as 2.0 mS / cm, it can be seen that the ionic conductivity decreased in the case of Production Examples 1 to 3 including the first solid electrolyte layer containing the binder.

[0112] This is because the binder added to impart adhesion between argyrodite particles during the production of the solid electrolyte was interposed between the argyrodite particles, resulting in a decrease in ionic conductivity.

[0113] The solid electrolytes of Production Examples 1 and 2 including the second solid electrolyte layer not containing the binder exhibit higher ionic conductivity compared to the solid electrolyte of Production Example 3 composed only of the first solid electrolyte layer containing the binder.

[0114] Therefore, in order to minimize the decrease in ionic conductivity and increase the contact between the solid electrolyte layer and the negative electrode, particularly at the interface between the negative electrode and the solid electrolyte layer where lithium deposition / depletion (Li plating / stripping) occurs during charge and discharge, it is preferable to configure the first solid electrolyte layer containing the binder and the second solid electrolyte layer not containing the binder together.

[0115] <Example 1> To produce a positive electrode for an all-solid-state battery, LiNi 0.8 Co 0.1 Mn 0.1 O2, argyrodite (Li6PS5Cl) as the solid electrolyte, furnace black as the conductive material, and polytetrafluoroethylene as the 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. The positive electrode slurry was applied to a 14-μm-thick aluminum current collector with a doctor blade and then vacuum dried at 100 °C for 12 hours to produce a positive electrode.

[0116] To manufacture a negative electrode for an all-solid-state battery including a coating layer and an ion conduction layer, a coating layer made of an Ag layer was formed by sputtering Ag to a size of 30 nm on a nickel current collector with a thickness of 10 μm. Then, a slurry in which acetylene black and polyvinylidene fluoride were mixed at a weight ratio of 97:3 was coated on the Ag layer to form an ion conduction layer, and by drying, a negative electrode having a multilayer structure was manufactured.

[0117] To manufacture a solid electrolyte layer, a first solid electrolyte layer slurry was manufactured by dispersing argyrodite (Li6PS5Cl) as a solid electrolyte and polytetrafluoroethylene as a binder in anisole at a weight ratio of 95:5 and stirring.

[0118] After coating the first solid electrolyte layer slurry on a polyethylene terephthalate (PET) release film, it was vacuum dried at 100 °C for 12 hours to manufacture a first solid electrolyte layer with a thickness of 50 μm.

[0119] After manufacturing a second solid electrolyte layer slurry by dispersing argyrodite alone as a solid electrolyte in anisole and stirring, this was coated on a polyethylene terephthalate release film, and then vacuum dried at 100 °C for 12 hours to manufacture a second solid electrolyte layer with a thickness of 30 μm.

[0120] The second solid electrolyte layer was laminated on one surface of the first solid electrolyte layer, and pressed at a pressure of 50 MPa at 25 °C using cold isostatic press to manufacture a solid electrolyte layer.

[0121] In this way, the release film was removed from the laminated solid electrolyte layer and placed between the positive electrode and the negative electrode.

[0122] An all-solid-state battery was manufactured by arranging the second solid electrolyte layer to face the negative electrode and the first solid electrolyte layer to face the positive electrode in the solid electrolyte layer interposed between the positive electrode and the negative electrode, placing it in an aluminum pouch, and sealing.

[0123] <Example 2> A all-solid-state battery was manufactured in the same manner as in Example 1, except that the thickness of the first solid electrolyte layer was 30 μm in Example 1.

[0124] <Example 3> A all-solid-state battery was manufactured in the same manner as in Example 1, except that in Example 1, cold isostatic pressing was used to press and laminate at a pressure of 20 MPa at 25°C.

[0125] <Example 4> A all-solid-state battery was manufactured in the same manner as in Example 1, except that in Example 1, hot isostatic pressing was used instead of cold isostatic pressing to press and laminate at a pressure of 20 MPa at 80°C.

[0126] <Comparative Example 1> A all-solid-state battery was manufactured in the same manner as in Example 1, except that in Example 1, the all-solid-state battery was composed only of a first solid electrolyte layer having a thickness of 50 μm for the solid electrolyte layer.

[0127] <Comparative Example 2> A all-solid-state battery was manufactured in the same manner as in Example 1, except that in Example 1, the all-solid-state battery was composed only of a second solid electrolyte layer having a thickness of 30 μm for the solid electrolyte layer.

[0128] <Comparative Example 3> A all-solid-state battery was manufactured in the same manner as in Example 1, except that in Example 1, in the solid electrolyte layer interposed between the positive electrode and the negative electrode, the first solid electrolyte layer faced the negative electrode and the second solid electrolyte layer faced the positive electrode.

[0129] <Comparative Example 4> A all-solid-state battery was manufactured in the same manner as in Example 1, except that in Example 1, cold isostatic pressing was used to press and laminate at a pressure of 200 MPa at 25°C.

[0130] <Comparative Example 5> A all-solid-state battery was manufactured in the same manner as in Example 1, except that in Example 1, cold isostatic pressing was used to press at a pressure of 5 MPa at 25°C for lamination.

[0131] <Comparative Example 6> A all-solid-state battery was manufactured in the same manner as in Example 1, except that in Example 1, instead of cold isostatic pressing, roll pressing was used to press at 25°C for lamination.

[0132] <Comparative Example 7> A all-solid-state battery was manufactured in the same manner as in Example 1, except that in Example 1, instead of cold isostatic pressing, hot pressing (uniaxial pressing) was used to press at a pressure of 50 MPa at 25°C for lamination.

[0133] <Experimental Example 2> The all-solid-state batteries manufactured in Examples 1 to 4 and Comparative Examples 1 to 7 were prepared, charged at 0.05 C in a constant current-constant voltage mode up to 4.25 V at 60°C, and discharged at 0.05 C up to 3.0 V, thereby measuring the initial charge and discharge capacities and efficiency.

[0134] Also, in order to evaluate the life characteristics of the all-solid-state battery, charging / discharging was performed 5 times under the conditions of charging at 0.1 C and discharging at 0.1 C in a voltage range of 4.25 V to 3.0 V.

[0135] The initial charge capacity, initial discharge capacity, charge-discharge efficiency, and retention rate measured in this way are shown in Table 2 below.

[0136] In Table 2 below, the initial charge capacity and initial discharge capacity are the charge capacity and discharge capacity of one cycle, and the charge-discharge efficiency means the efficiency of the discharge capacity with respect to the charge capacity measured in one cycle. Also, in Table 2 below, the retention rate is the discharge capacity measured in 5 cycles with respect to the discharge capacity measured in one cycle.

[0137]

Table 2

[0138] Referring to Table 2 above, it can be confirmed that the all-solid-state batteries of Examples 1 to 4 exhibit higher charge-discharge efficiency and retention rate than the all-solid-state battery of Comparative Example 1. As confirmed in Experimental Example 1 above, this is presumably due to the improved ionic conductivity of the solid electrolyte layer including the first solid electrolyte layer and the second solid electrolyte layer as compared to the solid electrolyte layer composed of only the first solid electrolyte layer.

[0139] The all-solid-state battery of Comparative Example 2, which was composed of only the second solid electrolyte layer without a binder, had a weak solid electrolyte layer, making it impossible to manufacture the all-solid-state battery itself.

[0140] In the case of Comparative Example 4, where the two-layer solid electrolyte layer was pressed at 200 MPa for lamination, the produced solid electrolyte layer became too hard and broke, resulting in it being unusable. In the case of Comparative Example 5, where it was pressed at 5 MPa, the pressing force was too low and the two layers were not adhered and separated. Therefore, it can be seen that when manufacturing the two-layer solid electrolyte layer by the hydrostatic pressure method, an appropriate pressure must be applied.

[0141] On the other hand, in the cases of Comparative Example 6, where pressing was performed using a roll press, and Comparative Example 7, where pressing was performed using a hot press, the two-layer solid electrolyte layer was adhered together as a single unit, but since the adhesion surface was not uniform, a short circuit occurred during charging. Therefore, it was difficult to apply to the all-solid-state battery.

[0142] Comparing the life characteristics, Examples 1 to 4 show very excellent retention rate results compared to Comparative Example 1.

[0143] Also, when comparing Examples 1 to 4 with Comparative Example 3, in Examples 1 to 4, 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 increases, and as a result, the formation of lithium dendrites can be delayed, so the retention rate can be maintained at a high level.

[0144] As described above, since the all-solid-state battery according to the present invention includes a structure in which the contact surface between the solid electrolyte layer and the negative electrode is expanded, it is possible to provide an all-solid-state battery with improved life characteristics by reducing the decrease in ionic conductivity.

[0145] Those having ordinary knowledge in the field to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above content.

Explanation of Reference Numerals

[0146] 110, 210 Solid electrolyte particles 120, 220 Solid electrolyte layers 130, 230 Binders 140, 240 Negative electrodes 221 First solid electrolyte layer 222 Second solid electrolyte layer

Claims

1. comprising a positive electrode, a negative electrode, and a solid electrolyte interposed between the positive electrode and the negative electrode, the solid electrolyte consists of a first solid electrolyte layer containing a binder and a second solid electrolyte layer not containing a binder, the second solid electrolyte layer faces the negative electrode, an all-solid-state battery in which the remaining components of the first solid electrolyte layer and the second solid electrolyte layer excluding the binder are identical to each other.

2. The binder is one or more 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), polyvinylidene carbonate, polyvinylpyrrolidinone, styrene - butadiene rubber, nitrile - butadiene rubber, and hydrogenated nitrile - butadiene rubber. The all-solid-state battery according to Claim 1.

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

4. The all-solid-state battery according to claim 1, wherein the content of the binder contained in the first solid electrolyte layer is 0.2% by weight to 15% by weight based on the weight of the total solid content contained in the first solid electrolyte layer.

5. The all-solid-state battery according to claim 1, wherein the first solid electrolyte layer and the second solid electrolyte layer are in an adhered state.

6. The all-solid-state battery according to claim 1, wherein the negative electrode does not include a negative electrode mixture layer.

7. The all-solid-state battery according to claim 1, wherein the negative electrode includes a coating layer and an ion conduction layer.

8. The all-solid-state battery according to claim 1, wherein the solid electrolyte particles on the surface of the second solid electrolyte layer are in contact with the negative electrode.

9. A battery module including the all-solid-state battery according to any one of claims 1 to 8 as a unit cell.

10. An all-solid-state battery manufacturing method including a positive electrode, a negative electrode, and a solid electrolyte interposed between the positive electrode and the negative electrode, wherein the solid electrolyte includes 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, comprising: (a) manufacturing a first solid electrolyte layer slurry and a second solid electrolyte layer slurry; (b) coating the first solid electrolyte layer slurry and the second solid electrolyte layer slurry on respective release films; (c) drying the first solid electrolyte layer slurry coating layer and the second solid electrolyte layer slurry coating layer manufactured in step (b) to form a first solid electrolyte layer and a second solid electrolyte layer. (d) laminating and pressing the first solid electrolyte layer and the second solid electrolyte layer so that they face each other; (e) removing the release film to obtain a solid electrolyte layer; (f) assembling a all-solid-state battery by disposing the solid electrolyte layer between a positive electrode and a negative electrode; and A method for manufacturing an all-solid-state battery, wherein the second solid electrolyte layer is disposed so as to face the negative electrode.

11. The method for manufacturing an all-solid-state battery according to claim 10, wherein the step (d) is performed by a hydrostatic pressing method.

12. The method for manufacturing an all-solid-state battery according to claim 11, wherein the pressure during hydrostatic pressing is 10 MPa to 100 MPa.

13. The method for manufacturing an all-solid-state battery according to claim 10, wherein the temperature in the step (d) is 5°C to 150°C.

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