Solid electrolyte and all-solid-state battery comprising same

Abstract

The present invention relates to a sulfide-based solid electrolyte and an all-solid-state battery comprising same. More specifically, the sulfide-based solid electrolyte comprises core particles and shell particles disposed on the surfaces of the core particles. The core particles include a compound represented by chemical formula 1 and having an argyrodite crystal structure. The shell particles include a compound represented by chemical formula 2 and having an argyrodite crystal structure.

Description

Solid electrolyte and all-solid-state battery containing the same

[0001] The present invention relates to a sulfide-based solid electrolyte and an all-solid-state battery including the same.

[0002]

[0003] Recent industrial demands have led to the active development of batteries with high energy density and safety. For example, lithium-ion batteries are being used not only in information and communication devices, but also in the automotive sector. Safety is particularly important in the automotive sector, as it is directly related to life.

[0004] Recently, all-solid-state batteries have been proposed, replacing the electrolyte in lithium-ion batteries with a solid electrolyte. By eliminating the use of flammable organic dispersion media, all-solid-state batteries significantly reduce the risk of fire or explosion in the event of a short circuit. Therefore, these all-solid-state batteries can offer superior safety.

[0005]

[0006] The problem to be solved by the present invention is to provide a solid electrolyte with improved rate characteristics.

[0007]

[0008] According to the concept of the present invention, a solid electrolyte may include a central particle and a shell particle on the surface of the central particle. The central particle may include a compound represented by the following chemical formula 1 and having an argyrodite crystal structure.

[0009] <Chemical Formula 1>

[0010] Li 7-a1 M1 a1 PS 6-c1 X1 c1

[0011] In chemical formula 1, M1 is Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn or a combination thereof, X1 is Cl, Br or a combination thereof, and a1 and c1 can each be a real number between 0 and 2.

[0012] The above shell particle is represented by the following chemical formula 2 and may include a compound having an argyrodite crystal structure.

[0013] <Chemical Formula 2>

[0014] Li 7-a2 M2 a2 PS 6-b2-c2 I b2 X c2

[0015] In chemical formula 2, M2 is Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn or a combination thereof, X2 is Cl, Br or a combination thereof, a2, b2 and c2 are each a real number between 0 and 2, b2 is greater than c2, and the sum of b2 and c2 may be less than or equal to 2.

[0016] According to another concept of the present invention, an all-solid-state battery may include a positive electrode layer; a negative electrode layer; and a solid electrolyte layer between the positive electrode layer and the negative electrode layer. The solid electrolyte layer may include: a first solid electrolyte layer including a sulfide-based solid electrolyte having an argyrodite crystal structure; and a second solid electrolyte layer including the above-described solid electrolyte. The first solid electrolyte layer may be adjacent to the positive electrode layer, and the second solid electrolyte layer may be adjacent to the negative electrode layer.

[0017]

[0018] According to embodiments of the present invention, a solid electrolyte may include a core particle and a shell particle surrounding its surface. The shell particle is rich in iodine (I), thereby protecting the core particle and enhancing the reduction stability of the solid electrolyte.

[0019] According to embodiments of the present invention, an all-solid-state battery may include a double-layer structure comprising the aforementioned solid electrolyte and a sulfide-based solid electrolyte. This prevents lithium dendrite formation from the negative electrode layer and suppresses side reactions in the negative electrode layer. Consequently, the all-solid-state battery of the present invention may have improved cell characteristics.

[0020]

[0021] Figure 1 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0022] Figure 2 is an enlarged cross-sectional view of area M of Figure 1.

[0023] Figure 3 is a plan view of an all-solid-state battery according to another embodiment of the present invention.

[0024] Figure 4 is a cross-sectional view taken along line A-A' of Figure 3.

[0025] FIG. 5 is a cross-sectional view taken along line A-A' of FIG. 3 to explain an all-solid-state battery according to another embodiment of the present invention.

[0026] Figure 6 shows the results of XRD spectra for each of the first solid electrolyte manufactured in Example 1 and the second solid electrolyte manufactured in Example 2.

[0027]

[0028] To fully understand the structure and effects of the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and subject to various modifications. However, the description of these embodiments is provided solely to ensure a complete disclosure of the present invention and to fully inform those skilled in the art of the invention of the scope of the invention.

[0029] In this specification, when a component is referred to as being on another component, it means that it can be formed directly on the other component, or a third component may be interposed between them. Furthermore, in the drawings, the thicknesses of the components are exaggerated for the sake of clarity. Parts designated by the same reference numerals throughout the specification represent the same components.

[0030] Embodiments described herein will be described with reference to cross-sectional and / or plan views, which are ideal illustrations of the present invention. In the drawings, the thicknesses of films and regions are exaggerated for the purpose of effectively explaining the technical contents. Accordingly, the regions illustrated in the drawings have a schematic nature, and the shapes of the regions illustrated in the drawings are intended to illustrate specific shapes of regions of the device and are not intended to limit the scope of the invention. Although terms such as first, second, and third are used to describe various components in various embodiments of the present specification, these components should not be limited by such terms. These terms are used only to distinguish one component from another. The embodiments described and illustrated herein also include complementary embodiments thereof.

[0031] The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise. As used herein, the words "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components.

[0032]

[0033] Fig. 1 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention. Fig. 2 is an enlarged cross-sectional view of area M of Fig. 1.

[0034] Referring to FIG. 1, an all-solid-state battery (10) according to one embodiment may include a positive electrode layer (100), a negative electrode layer (200) facing the positive electrode layer (100), and a solid electrolyte layer (300) disposed between the positive electrode layer (100) and the negative electrode layer (200). However, the present invention is not limited thereto, and the all-solid-state battery (10) may further include an additional functional layer, such as an adhesion enhancing layer, disposed between the positive electrode layer (100) and the solid electrolyte layer (300) or between the negative electrode layer (200) and the solid electrolyte layer (300).

[0035] The positive electrode layer (100) of one embodiment may include a positive electrode current collector (110) and a positive electrode active material layer (120) disposed on the positive electrode current collector (110). Referring to FIG. 2, the positive electrode active material layer (120) may include a positive electrode active material (PAM), a third solid electrolyte (SE3), a conductive material, and a binder.

[0036] The positive electrode current collector (110) can provide a reference surface on which the positive electrode active material layer (120) is arranged. The positive electrode current collector (110) can include a plate or foil including, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof.

[0037] Meanwhile, unlike that illustrated in FIG. 1, in one embodiment of the present invention, the positive electrode current collector (110) may be omitted. Although not illustrated, a carbon layer having a thickness of 0.1 μm to 4 μm may be additionally disposed between the positive electrode current collector (110) and the positive electrode active material layer (120) to increase the bonding strength between the positive electrode current collector (110) and the positive electrode active material layer (120).

[0038] Referring to FIG. 2, the positive electrode active material (PAM) may include a material that can reversibly absorb and desorb lithium ions. The positive electrode active material (PAM) may include a plurality of particles. The positive electrode active material (PAM) may include, but is not necessarily limited to, lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide. The positive electrode active material (PAM) may be used alone or as a mixture of two or more.

[0039] Lithium transition metal oxides include, for example, Li a A 1-b B b D2(0.90≤a≤1, 0≤b≤0.5), Li a E 1-b B b O 2-c D c (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05), LiE 2-b B b O 4-c D c (0≤b≤0.5, 0≤c≤0.05), Li a Ni 1-b-c Co b B c D α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Ni 1-b-c Co b B c O 2-α F α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li aNor 1-b-c Mn b B c D α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2), Li a Nor 1-b-c Mn b B c O 2-α F α (0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2), Li a Nor b E c G d O2(0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1), Li a Nor b Co c Mn d GeO2(0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1), Li a NiG b O2(0.9≤a≤1, 0.001≤b≤0.1), Li a CoG b O2(0.90≤a≤1, 0.001≤b≤0.1), Li a MnG b O2(0.90≤a≤1, 0.001≤b≤0.1), Li a Mn2GbO4(0.90≤a≤1, 0.001≤b≤0.1), QO2, QS2, LiQS2, V2O5, LiV2O5, LiIO2, LiNiVO4, Li 3-f J2(PO4)3(0≤f≤2), Li 3-fA compound represented by any one of Fe2(PO4)3(0≤f≤2), LiFePO4. In these compounds, the capital letter “A” is Ni, Co, Mn, or a combination thereof, the capital letter “B” is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof, the capital letter “D” is O, F, S, P, or a combination thereof, the capital letter “E” is Co, Mn, or a combination thereof, the capital letter “F” is F, S, P, or a combination thereof, the capital letter “G” is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof, the capital letter “Q” is Ti, Mo, Mn, or a combination thereof, the capital letter “I” is Cr, V, Fe, Sc, Y, or a combination thereof, and the capital letter “J” is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0040] The cathode active material (PAM) may include, for example, a lithium salt of a transition metal oxide having a layered rock salt type structure among the lithium transition metal oxides described above. The "layered rock salt type structure" is, for example, a cubic rock salt type structure. <111> It is a structure in which oxygen atomic layers and metal atomic layers are alternately and regularly arranged in a direction, and thereby each atomic layer forms a two-dimensional plane. The "cubic rock salt structure" refers to the sodium chloride type (NaCl type) structure, which is a type of crystal structure, and specifically refers to a structure in which the face-centered cubic lattice (fcc) formed by each cation and anion is arranged with a displacement of half of the ridge of the unit lattice. Lithium transition metal oxides having this layered rock salt structure include, for example, LiNi x Co y Al z O2(NCA) or LiNi x Co y Mnz O2(NCM) (0 <x<1,0<y<1, 0<z<1, x+y+z=1) 등의 삼원계 리튬전이금속산화물일 수 있다. 양극 활물질이 층상암염형 구조를 갖는 삼원계 리튬전이금속산화물을 포함하는 경우, 전고체 전지(10)의 에너지 밀도가 커지고 열안정성이 향상될 수 있다.

[0041] The above-described compound included in the positive electrode active material (PAM) may be covered by a coating layer (not shown). The positive electrode active material (PAM) may also be a mixture of the above-described compound and a compound to which a coating layer is added. Meanwhile, the coating layer added to the surface of the positive electrode active material (PAM) may include, for example, an oxide, a hydroxide, an oxyhydroxide, an oxycarbonate, or a hydroxycarbonate of the coating elements below. The compound forming the coating layer may be amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer may include, for example, Li2O-ZrO2 (LZO). The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the positive electrode active material (PAM). The method for forming the coating layer may include, for example, spray coating, dipping, etc.

[0042] When the positive electrode active material (PAM) contains nickel (Ni) as a ternary lithium transition metal oxide such as NCA or NCM, for example, the capacity density of the all-solid-state battery (10) can be increased, thereby reducing metal dissolution of the positive electrode active material (PAM) in a charged state. As a result, the cycle characteristics of the all-solid-state battery (10) in a charged state are improved. Meanwhile, the "cycle characteristics" are characteristics indicating the degree to which the all-solid-state battery (10) is deteriorated by charge / discharge of the all-solid-state battery (10). An all-solid-state battery (10) with high cycle characteristics may have a small degree of deterioration of the all-solid-state battery (10) due to charge / discharge, and an all-solid-state battery (10) with low cycle characteristics may have a large degree of deterioration of the all-solid-state battery (10) due to charge / discharge.

[0043] The positive electrode active material (PAM) may have a particle shape such as a sphere or an ellipsoid, for example. The particle size and content of the positive electrode active material (PAM) are not particularly limited.

[0044] Referring to FIG. 2, the third solid electrolyte (SE3) may have a particle shape. The third solid electrolyte (SE3) may be dispersed between the positive electrode active materials (PAM). The third solid electrolyte (SE3) may include a sulfide-based solid electrolyte having excellent lithium ion conductivity characteristics. Examples of the sulfide-based solid electrolyte include Li2S-P2S5, Li2S-P2S5-LiX (X is a halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (m, n are positive numbers, capital letter “Z” represents Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q(p, q are positive numbers, capital letter “M” is one of P, Si, Ge, B, Al, Ga In), Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I x It may include at least one selected from (0≤x≤2).

[0045] Sulfide-based solid electrolytes include, for example, Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), and Li 7-x PS 6-x I x (0≤x≤2) may be an argyrodite-type compound including at least one selected from. In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I. The density of the argyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or more, the internal resistance of the all-solid-state battery is reduced, and the defect of the solid electrolyte membrane being penetrated and short-circuited due to the formation of lithium dendrites can be prevented. The elastic modulus of the solid electrolyte may be, for example, 15 GPa to 35 GPa.

[0046] The third solid electrolyte (SE3) in the positive electrode active material layer (120) may have a smaller median particle size (D50) than the first and second solid electrolytes (SE1, SE2) in the solid electrolyte layer (300) to be described later. For example, the median particle size (D50) of the solid electrolyte included in the positive electrode active material layer (120) may be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less of the median particle size (D50) of the solid electrolyte included in the solid electrolyte layer (300). Meanwhile, the median particle size (D50) may be a median diameter measured using a laser particle size distribution meter.

[0047] The positive electrode active material layer (120) may include a conductive material. The conductive material may have conductivity without causing a chemical change in the all-solid-state battery (10), thereby increasing the conductivity of the positive electrode active material (PAM) and the third solid electrolyte (SE3). The conductive material may include a carbon-based material. The conductive material may include, for example, one or more selected from graphite, carbon black, acetylene black, carbon nanofibers, and carbon nanotubes.

[0048] The positive electrode active material layer (120) may further include a binder. The binder may bind the positive electrode active material (PAM), the third solid electrolyte (SE3), and the conductive material within the positive electrode active material layer (120) to each other. The binder may include a material for improving the bonding strength between the positive electrode active material layer (120) and the positive electrode current collector (110). The binder may include, for example, polyvinylidene fluoride, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0049] Based on 100 parts by weight of the total of the positive electrode active material (PAM), the third solid electrolyte (SE3), the conductive agent, and the binder, the positive electrode active material layer (120) may include 85 parts by weight or more and 92 parts by weight or less of the positive electrode active material (PAM). Based on 100 parts by weight of the total of the positive electrode active material (PAM), the third solid electrolyte (SE3), the conductive agent, and the binder, the positive electrode active material layer (120) may include 0.5 parts by weight or more and 1.5 parts by weight or less of the binder.

[0050] Based on 100 parts by weight of the third solid electrolyte (SE3), the positive electrode active material layer (120) may include 1 part by weight or more and 50 parts by weight or less of a conductive material. When the conductive material is included in the positive electrode active material layer (120) in an amount of less than 1 part by weight based on 100 parts by weight of the third solid electrolyte (SE3), the proportion of the conductive material may decrease, thereby lowering the electrical conductivity of the positive electrode active material layer (120). When the conductive material is included in the positive electrode active material layer (120) in an amount of more than 50 parts by weight based on 100 parts by weight of the third solid electrolyte (SE3), the proportion of the conductive material may be excessively high, so that a covering layer covering the surface of the third solid electrolyte (SE3) may not be properly formed.

[0051] The positive electrode active material layer (120) may further include additives such as fillers, coating agents, dispersants, and ion conductive aids in addition to the above-described positive electrode active material (PAM), third solid electrolyte (SE3), conductive agent, and binder.

[0052] The negative electrode layer (200) may include a negative electrode current collector (210) and a negative electrode coating layer (220) on the negative electrode current collector (210). The negative electrode current collector (210) may provide a reference surface on which the negative electrode coating layer (220) is disposed. The negative electrode current collector (210) may include, for example, a material that does not react with lithium, i.e., does not form an alloy or a compound with lithium. For example, the negative electrode current collector (210) may include at least one metal selected from the group consisting of copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni). The thickness of the negative electrode current collector (210) may be 1 μm to 20 μm, more specifically 5 μm to 15 μm, and more specifically 7 μm to 10 μm.

[0053] The negative electrode current collector (210) may be composed of one of the above-described metals, or may include an alloy or coating material of two or more metals. The negative electrode current collector (210) may have, for example, a plate shape or a foil shape. Meanwhile, in one embodiment, the negative electrode current collector (210) may be omitted.

[0054] The negative electrode coating layer (220) can allow lithium metal to grow between it and the negative electrode current collector (210) when the all-solid-state battery (10) is charged. The negative electrode coating layer (220) can act as a protective layer for the lithium metal and simultaneously suppress the precipitation and growth of lithium dendrites.

[0055] The cathode coating layer (220) may include a metal and carbon. For example, the cathode coating layer (220) may include at least one metal selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The cathode coating layer (220) may include at least one carbon selected from the group consisting of carbon black, acetylene black, furnace black, ketjen black, and graphene. In one embodiment, the cathode coating layer (220) may include a mixture of carbon black and silver (Ag).

[0056] The cathode coating layer (220) may further include additives other than metal and carbon. The cathode coating layer (220) may further include, for example, at least one additive selected from the group consisting of a binder, a filler, a coating agent, a dispersant, and an ion conductive additive.

[0057] The negative electrode coating layer (220) may have a smaller thickness than the positive electrode active material layer (120). The thickness of the negative electrode coating layer (220) may be, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the thickness of the positive electrode active material layer (120). The thickness of the negative electrode coating layer (220) may be, for example, 1 um to 20 um, 2 um to 10 um, or 3 um to 7 um. If the thickness of the negative electrode coating layer (220) is too thin, lithium dendrites formed between the negative electrode coating layer (220) and the negative electrode current collector (210) may cause the negative electrode coating layer (220) to collapse, thereby deteriorating the cycle characteristics of the all-solid-state battery (10). If the thickness of the cathode coating layer (220) increases excessively, the energy density of the all-solid-state battery (10) may decrease and the internal resistance of the all-solid-state battery (10) due to the cathode coating layer (220) may increase, thereby deteriorating the cycle characteristics of the cell.

[0058] Meanwhile, although not shown, a carbon layer may be further included to improve adhesion between the cathode coating layer (220) and the solid electrolyte layer (300).

[0059] A solid electrolyte layer (300) may be provided between the positive electrode layer (100) and the negative electrode layer (200). The solid electrolyte layer (300) may include a sulfide-based solid electrolyte having excellent lithium ion conductivity characteristics. The solid electrolyte in the solid electrolyte layer (300) may be the same as or different from any one of the materials included in the third solid electrolyte (SE3) in the positive electrode active material layer (120) described above.

[0060] The solid electrolyte layer (300) may include a first solid electrolyte layer (310) and a second solid electrolyte layer (320). The first solid electrolyte layer (310) may be adjacent to the positive electrode layer (100), and the second solid electrolyte layer (320) may be adjacent to the negative electrode layer (200).

[0061] Referring to FIG. 2, the first solid electrolyte layer (310) may include a first solid electrolyte (SE1). The first solid electrolyte (SE1) may have a particle shape such as a sphere or ellipsoid.

[0062] The first solid electrolyte (SE1) may include a sulfide-based solid electrolyte. The first solid electrolyte (SE1) may be amorphous, crystalline, or a mixture thereof. In addition, the solid electrolyte may include, for example, at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements among the above-described sulfide-based solid electrolyte materials. For example, the solid electrolyte may be a material including Li2S-P2S5. When using a sulfide-based solid electrolyte material including Li2S-P2S5 to form the solid electrolyte, the mixing molar ratio of Li2S and P2S5 is, for example, in the range of Li2S:P2S5=50:50 to 90:10.

[0063] In one embodiment, the first solid electrolyte (SE1) is Li 7-a M a PS 6-c X c It may be an argyrodite-type compound containing . Here, X may be Cl, Br, or a combination thereof. M may be Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn, or a combination thereof. Each of a and c may be a real number between 0 and 2.

[0064] The density of the argyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or more, the internal resistance of the all-solid-state battery is reduced, and the defect of the solid electrolyte membrane being penetrated and short-circuited due to the formation of lithium dendrites can be prevented. The elastic modulus of the first solid electrolyte (SE1) is, for example, 15 GPa to 35 GPa.

[0065] The first solid electrolyte layer (310) may further include a binder. The binder included in the solid electrolyte layer (300) may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited thereto. The binder of the first solid electrolyte layer (310) may be the same as or different from the binder included in the positive electrode active material layer (120) or the binder included in the negative electrode coating layer (220).

[0066] Referring to FIG. 2, the second solid electrolyte layer (320) may include a second solid electrolyte (SE2). The second solid electrolyte (SE2) may have a particle shape such as a sphere or ellipsoid.

[0067] According to embodiments of the present invention, the second solid electrolyte (SE2) may include a central particle (CPA) and shell particles (SPA) on the surface of the central particle (CPA). The average particle diameter of the central particle (CPA) may be larger than the average particle diameter of the shell particle (SPA). For example, the average particle diameter of the central particle (CPA) may be 5 to 100 times the average particle diameter of the shell particle (SPA).

[0068] The shell particles (SPA) can form a shell surrounding the surface of the central particle (CPA). In other words, the second solid electrolyte (SE2) can have a core-shell structure. The shell particles (SPA) can completely surround the surface of the central particle (CPA) or partially surround the surface of the central particle (CPA).

[0069] The central particle (CPA) and the shell particle (SPA) may have different compositions. In one embodiment, the central particle (CPA) may include a sulfide-based solid electrolyte. The central particle (CPA) may include the argyrodite-type compound described above in the first solid electrolyte (SE1). The composition of the central particle (CPA) may be substantially the same as or different from the composition of the first solid electrolyte (SE1).

[0070] The shell particle (SPA) may include a sulfide-based solid electrolyte rich in iodine (I). For example, the shell particle (SPA) may include Li 7-a M a PS 6-b-c I b X c may include a compound of, wherein X may be Cl, Br, or a combination thereof. M may be Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn, or a combination thereof. Each of a, b, and c may be a real number between 0 and 2. b may be greater than c. The sum of b and c may be less than or equal to 2. In one embodiment, b may be between 0.5 and 2. c may be between 0 and 0.5.

[0071] The iodine (I) content of the shell particle (SPA) may be greater than the iodine (I) content of the central particle (CPA). The iodine (I) content of the shell particle (SPA) may be greater than the iodine (I) content of the first solid electrolyte (SE1) described above. The iodine (I) content of the shell particle (SPA) may be 2 to 100 times the iodine (I) content of the central particle (CPA).

[0072] The second solid electrolyte (SE2) can have improved reduction stability through a core-shell structure between the central particle (CPA) and the shell particle (SPA). The second solid electrolyte (SE2) can be in direct contact with the negative electrode coating layer (220). As a result, the second solid electrolyte (SE2) can suppress lithium dendrites formed between the negative electrode coating layer (220) and the negative electrode current collector (210). The second solid electrolyte (SE2) can effectively suppress negative electrode side reactions. As a result, the cell performance of the all-solid-state battery (10) according to the present invention can be improved.

[0073] Referring back to FIG. 1, the first solid electrolyte layer (310) and the second solid electrolyte layer (320) may have different thicknesses. The first solid electrolyte layer (310) may have a first thickness (TK1), and the second solid electrolyte layer (320) may have a second thickness (TK2). The first thickness (TK1) may be greater than the second thickness (TK2). For example, the first thickness (TK1) may be 2 to 100 times greater than the second thickness (TK2).

[0074]

[0075] Fig. 3 is a plan view of an all-solid-state battery according to another embodiment of the present invention. Fig. 4 is a cross-sectional view taken along line A-A' of Fig. 3. In this embodiment, detailed descriptions of technical features that overlap with those previously described with reference to Figs. 1 and 2 will be omitted, and differences will be described in detail.

[0076] Referring to FIGS. 3 and 4, the area of ​​the anode layer (100) and the area of ​​the cathode layer (200) may be different from each other. Specifically, the area of ​​the cathode layer (200) may be larger than the area of ​​the anode layer (100). The anode layer (100) may be completely overlapped within the cathode layer (200).

[0077] In one embodiment of the present invention, the first solid electrolyte layer (310) may have substantially the same area as the positive electrode layer (100). The second solid electrolyte layer (320) may have substantially the same area as the negative electrode layer (200).

[0078] Specifically, the first solid electrolyte layer (310) may have a first width (WI1) in a first direction (D1). The second solid electrolyte layer (320) may have a second width (WI2) in the first direction (D1). The first width (WI1) may be smaller than the second width (WI2). The first solid electrolyte layer (310) may have a third width (WI3) in the second direction (D2). The second solid electrolyte layer (320) may have a fourth width (WI4) in the second direction (D2). The third width (WI3) may be smaller than the fourth width (WI4).

[0079] The all-solid-state battery (10) according to the present embodiment can be manufactured by forming a first laminate of a positive electrode layer (100) and a first solid electrolyte layer (310), forming a second laminate of a negative electrode layer (200) and a second solid electrolyte layer (320), and then laminating the first laminate and the second laminate.

[0080] FIG. 5 is a cross-sectional view taken along line A-A' of FIG. 3 to explain an all-solid-state battery according to another embodiment of the present invention. Referring to FIG. 5, the negative electrode layer (200) of the all-solid-state battery (10) may further include a lithium metal layer (400) between the negative electrode current collector (210) and the negative electrode coating layer (220). The thickness of the lithium metal layer (400) may further increase when the all-solid-state battery (10) is charged. The negative electrode coating layer (220) serves as a protective layer for the lithium metal layer (400), and at the same time, may suppress the growth of lithium dendrites from the lithium metal layer (400).

[0081] The lithium metal layer (400) may be a metal thin film containing lithium or a lithium alloy. The lithium alloy may include, but is not limited to, a Li-Al alloy, a Li-Sn alloy, a Li-In alloy, a Li-Ag alloy, a Li-Au alloy, a Li-Zn alloy, a Li-Ge alloy, a Li-Si alloy, etc., and any lithium alloy may be used. The lithium metal layer (400) may contain one of these alloys or lithium. Alternatively, the lithium metal layer (400) may contain various types of alloys.

[0082] The lithium metal layer (400) may have a fifth width (WI5) in the first direction (D1). The fifth width (WI5) may be equal to or greater than the first width (WI1). The fifth width (WI5) may be equal to or less than the second width (WI2). For example, the fifth width (WI5) may be greater than the first width (WI1) and less than the second width (WI2).

[0083]

[0084] Example 1: Preparation of the first solid electrolyte

[0085] Li2S, P2S5, LiCl, LiBr r are the target compositions. 5.4 PS 4.4 Cl 0.8 Br 0.8After weighing each, mechanical milling treatment was performed by mixing in a ball mill for 20 hours using a high energy mill (Pulnerisette 7) equipment. The mechanical milling treatment was performed for 20 hours at a rotation speed of 380 rpm, at room temperature, and in an argon atmosphere.

[0086] Li obtained from the above mechanical milling treatment 5.4 PS 4.4 Cl 0.8 Br 0.8 A first solid electrolyte was obtained by heat-treating 300 mg of the powder material of the composition at 450°C for 12 hours in a vacuum atmosphere.

[0087]

[0088] Example 2: Preparation of a second solid electrolyte

[0089] The first solid electrolyte of Example 1 was mixed with an iodine compound. The mixture was heat-treated to obtain a second solid electrolyte with a core-shell structure. The second solid electrolyte had a central particle of Li. 5.4 PS 4.4 Cl 0.8 B r0.8 It has a composition of Li and the shell particles are 5.4 PS 4.4 Cl 0.7 Br 0.85 I 0.05 It has the composition of .

[0090]

[0091] Manufacturing example: Manufacturing of all-solid-state batteries

[0092] (positive electrode active material)

[0093] Cathode active material LiNi0.8Co0. 15 Mn0. 05 O2 (NCM) powder was prepared.

[0094] (bipolar layer)

[0095] LiNi0.8Co0 as the positive electrode active material described above. 15 Mn0. 05O2 (NCM) powder was prepared. A crystalline argyrodite-based solid electrolyte (Li6PS5Cl) was prepared as a solid electrolyte. A polytetrafluoroethylene (PTFE) binder (Teflon binder from DuPont) was prepared as a binder. Carbon nanofibers (CNF) were prepared as a conductive material. These materials were mixed in a weight ratio of positive electrode active material: solid electrolyte: conductive material: binder = 84.2:11.5:2.9:1.4, and the mixture was formed into a large sheet shape to manufacture a positive electrode sheet. The manufactured positive electrode sheet was pressed onto a positive electrode current collector made of 18 μm thick carbon-coated aluminum foil to manufacture a positive electrode layer. The thickness of the positive electrode active material layer included in the positive electrode layer was approximately 100 μm.

[0096] (cathode layer)

[0097] Lithium metal with a thickness of approximately 30㎛ was used as the cathode layer.

[0098] (First solid electrolyte layer)

[0099] A mixture was prepared by adding 1 part by weight of a styrene-butadiene rubber (SBR) binder to 100 parts by weight of the first solid electrolyte manufactured in Example 1. Xylene and diethylbenzene were added to the mixture and stirred to prepare a slurry. The prepared slurry was applied onto a nonwoven fabric using a blade coater and dried in air at 40°C to obtain a laminate. The obtained laminate was vacuum-dried at 40°C for 12 hours. A first solid electrolyte layer was manufactured through the above process.

[0100] (Second solid electrolyte layer)

[0101] In Example 2, a mixture was prepared by adding 1 part by weight of a styrene-butadiene rubber (SBR) binder to 100 parts by weight of the second solid electrolyte. Xylene and diethylbenzene were added to the mixture and stirred to prepare a slurry. The prepared slurry was applied onto a nonwoven fabric using a blade coater and dried in air at 40°C to obtain a laminate. The obtained laminate was vacuum-dried at 40°C for 12 hours. A second solid electrolyte layer was prepared through the above process.

[0102] (Manufacturing of all-solid-state batteries)

[0103] A first solid electrolyte layer was placed on the positive electrode layer. A second solid electrolyte layer was placed on the negative electrode layer. These layers were laminated to prepare a laminate. The prepared laminate was plate pressed at 25°C and a pressure of 100 MPa for 10 minutes to produce an all-solid-state battery.

[0104]

[0105] Comparative example

[0106] An all-solid-state battery was manufactured in the same manner as described above, except that the second solid electrolyte layer using the second solid electrolyte of Example 2 was omitted.

[0107]

[0108] Evaluation Example 1: Ionic Conductivity Measurement

[0109] The powder of the first solid electrolyte of Example 1 and the powder of the second solid electrolyte of Example 2 were each placed in a mold with a diameter of 10 mm and pressed at a pressure of 350 MPa to form pellets. An indium (In) thin film was coated on both sides of the pellets to prepare a sample for measuring ionic conductivity. The impedance of the prepared sample was measured using an AUTOLAB PGSTAT30 (Metrohm Autolab Co. Ltd.) potentiostat, and a Nyquist plot was plotted, from which the ionic conductivity was measured at 25°C.

[0110] The measured ionic conductivity is shown in Table 1 below.

[0111] Solid electrolyte composition ionic conductivity (mS / cm) Example 1 Li 5.4 PS 4.4 Cl 0.8 Br 0.8 2.7 Example 2Li 5.4 PS 4.4 Cl 0.7 Br 0.85 I 0.05 2.1

[0112] As shown in Table 1, the ionic conductivity of the second solid electrolyte manufactured in Example 2 was excellent at 1 mS / cm or more.

[0113]

[0114] Evaluation Example 2: XRD Analysis

[0115] XRD spectra were measured for each of the first solid electrolyte manufactured in Example 1 and the second solid electrolyte manufactured in Example 2, and the results are shown in Fig. 6. Referring to Fig. 6, it was found that each of the first solid electrolyte and the second solid electrolyte had an argyrodite crystal structure.

[0116]

[0117] Evaluation Example 3: Rate Characteristic Evaluation

[0118] The charge-discharge characteristics of the all-solid-state battery of the comparative example and the all-solid-state battery according to the embodiment of the present invention were evaluated by the following charge-discharge test. The charge-discharge test was performed by placing the all-solid-state battery in a constant temperature bath at 45°C.

[0119] The battery was charged at a constant current of 0.1 C for approximately 10 hours until the battery voltage reached 4.25 V, and then charged at a constant voltage of 4.25 V until the current reached 0.05 C, followed by a 10-minute rest period, and then discharged at a constant current of 0.1 C for approximately 10 hours until the battery voltage reached 2.5 V, followed by a 10-minute rest period. (1st cycle).

[0120] The battery was charged at a constant current of 0.1C for approximately 10 hours until the battery voltage reached 4.25V, and then charged at a constant voltage of 4.25V until the current reached 0.05C, followed by a 10-minute rest period, and then discharged at a constant current of 0.33C for approximately 10 hours until the battery voltage reached 2.5V, followed by a 10-minute rest period. (2nd cycle).

[0121] The battery was charged at a constant current of 0.1C for approximately 10 hours until the battery voltage reached 4.25V, and then charged at a constant voltage of 4.25V until the current reached 0.05C, followed by a 10-minute rest period, and then discharged at a constant current of 1.0C for approximately 10 hours until the battery voltage reached 2.5V, followed by a 10-minute rest period. (Cycle 3)

[0122] The rate characteristics were calculated according to Equation 1 below and are shown in Table 2 below.

[0123] <Formula 1>

[0124] Rate characteristic (%) = (discharge capacity of the 3rd cycle / discharge capacity of the 2nd cycle) × 100

[0125] Comparative Example: Preventive Capacity (mAh / g) 1st Cycle 196.5204.8 2nd Cycle 178.2190.6 3rd Cycle 147171.3 Rate Characteristics (%) 82.589.9

[0126] As shown in Table 2 above, it was found that the all-solid-state battery including the second solid electrolyte layer had significantly improved rate characteristics. It was found that the all-solid-state battery including the solid electrolyte according to the present invention had very excellent rate characteristics.

[0127] While embodiments of the present invention have been described with reference to the attached drawings, the present invention may be implemented in other specific forms without altering the technical spirit or essential features thereof. Therefore, it should be understood that the embodiments described above are exemplary in all respects and are not limiting.

Claims

1. Central particle; and Including shell particles on the surface of the above central particle, The above central particle is represented by the following chemical formula 1 and includes a compound having an argyrodite crystal structure, <Chemical Formula 1> There 7-a1 M1 a1 PS 6-c1 X1 c1 In chemical formula 1, M1 is Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn or a combination thereof, X1 is Cl, Br or a combination thereof, a1 and c1 are each real numbers between 0 and 2, The above shell particles are represented by the following chemical formula 2 and include a compound having an argyrodite crystal structure, <Chemical Formula 2> The 7-a2 M2 a2 PS 6-b2-c2 I b2 X c2 In chemical formula 2, M2 is Na, K, Fe, Mg, Ca, Ag, Cu, Zr, Zn or a combination thereof, X2 is Cl, Br or a combination thereof, a2, b2 and c2 are each a real number between 0 and 2, b2 is greater than c2, and the sum of b2 and c2 is less than or equal to 2. Solid electrolyte.

2. In paragraph 1, A solid electrolyte wherein the iodine (I) content of the shell particles is greater than the iodine (I) content of the central particles.

3. In paragraph 2, A solid electrolyte, wherein the iodine (I) content of the shell particles is 2 to 100 times the iodine (I) content of the central particles.

4. In paragraph 1, b2 is 0.5 to 2, C2 is a solid electrolyte with a value between 0 and 0.

5.

5. In paragraph 1, The above shell particle comprises a plurality of shell particles, A solid electrolyte in which the plurality of shell particles constitute a shell covering the surface of the central particle.

6. Bipolar layer; cathode layer; and Including a solid electrolyte layer between the positive electrode layer and the negative electrode layer, The above solid electrolyte layer: A first solid electrolyte layer comprising a sulfide-based solid electrolyte having an argyrodite crystal structure; and A second solid electrolyte layer comprising the solid electrolyte of claim 1, The first solid electrolyte layer is adjacent to the positive electrode layer, An all-solid-state battery, wherein the second solid electrolyte layer is adjacent to the cathode layer.

7. In paragraph 6, The above negative electrode layer includes a negative electrode current collector and a negative electrode coating layer on the negative electrode current collector, An all-solid-state battery, wherein the second solid electrolyte layer is in direct contact with the negative electrode coating layer.

8. In paragraph 7, The above cathode coating layer: At least one metal selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn); and An all-solid-state battery comprising at least one carbon selected from the group consisting of carbon black, acetylene black, furnace black, ketjen black, and graphene.

9. In paragraph 7, An all-solid-state battery, wherein the negative electrode layer further includes a lithium metal layer between the negative electrode current collector and the negative electrode coating layer.

10. In paragraph 9, The first solid electrolyte layer has a first width, The second solid electrolyte layer has a second width, The lithium metal layer has a third width, An all-solid-state battery, wherein the third width is greater than the first width and smaller than the second width.

11. In paragraph 6, The above positive electrode layer includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector, An all-solid-state battery, wherein the first solid electrolyte layer is in direct contact with the positive electrode active material layer.

12. In paragraph 6, An all-solid-state battery, wherein the iodine (I) content of the shell particles is greater than the iodine (I) content of the sulfide-based solid electrolyte of the first solid electrolyte layer.

13. In paragraph 6, The first solid electrolyte layer has a first width, The second solid electrolyte layer has a second width, An all-solid-state battery, wherein the second width is greater than the first width.

14. In paragraph 6, The first solid electrolyte layer has a first thickness, The second solid electrolyte layer has a second thickness, An all-solid-state battery, wherein the second thickness is smaller than the first thickness.

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