Solid electrolyte membrane, all-solid-state battery comprising same, and solid electrolyte membrane preparation method

Abstract

The present invention relates to a solid electrolyte membrane and an all-solid-state battery comprising same, and more specifically, comprises: a first solid electrolyte having a particle form and having a first average particle diameter; and a second solid electrolyte having a fine particle form and having a long axis length of 1 μm or less, wherein the first average particle diameter is 2 μm to 10 μm, and the weight ratio of the second solid electrolyte to the total weight of the first and second solid electrolytes is 10 wt% to 30 wt%.

Description

Solid electrolyte membrane, all-solid-state battery including the same, and method for manufacturing the solid electrolyte membrane

[0001] The present invention relates to a solid electrolyte membrane, an all-solid-state battery including the same, and a method for manufacturing the solid electrolyte membrane.

[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, which replace the electrolyte with a solid electrolyte, have been proposed. By eliminating the use of flammable liquid electrolytes, 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 significantly improve safety compared to lithium-ion batteries, which use liquid electrolytes.

[0005]

[0006] The problem to be solved by the present invention is to provide a solid electrolyte membrane having excellent rate characteristics and excellent lifespan.

[0007] Another problem to be solved by the present invention is to provide a method for manufacturing a solid electrolyte membrane having excellent rate characteristics and excellent lifespan.

[0008]

[0009] According to the concept of the present invention, a solid electrolyte membrane comprises: a first solid electrolyte having a particle shape and a first average particle size; and a second solid electrolyte having a fine particle shape and a major axis length of 1 μm or less, wherein the first average particle size is 2 μm to 10 μm, and the weight ratio of the second solid electrolyte to the total weight of the first and second solid electrolytes may be 10 wt% to 30 wt%.

[0010] According to the concept of the present invention, an all-solid-state battery may comprise: the solid electrolyte membrane; a positive electrode comprising a positive current collector and a positive active material layer; and a negative electrode comprising a negative current collector and a coating layer.

[0011] A method for manufacturing a solid electrolyte membrane according to the concept of the present invention may include: preparing a sulfide-based solid electrolyte; mixing the sulfide-based solid electrolyte with a binder to form a solid electrolyte slurry; and applying the solid electrolyte slurry to a substrate. Preparing the sulfide-based solid electrolyte may include: mixing raw materials in powder form to form a mixture, wherein the raw materials in powder form include a sulfur precursor, a phosphorus precursor, and a halogen precursor; calcining the mixed mixture; and performing a grinding process on the calcined mixture to form a first solid electrolyte in particulate form and a second solid electrolyte in fine powder form. The grinding process may be controlled such that the second solid electrolyte is 10 wt% to 30 wt% of the total weight of the first and second solid electrolytes.

[0012]

[0013] The solid electrolyte membrane according to the present invention can optimize the grain boundary of the solid electrolyte and the porosity of the solid electrolyte membrane by including a solid electrolyte in particulate form and a solid electrolyte in fine particle form in an appropriate ratio. This can improve the rate characteristics and lifespan characteristics of the all-solid-state battery.

[0014] By using the method for manufacturing a solid electrolyte membrane according to the present invention, an electrolyte membrane with excellent rate characteristics and lifespan characteristics can be manufactured.

[0015]

[0016] FIG. 1 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0017] FIG. 2 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0018] FIGS. 3 and FIGS. 4 are a plan view and a cross-sectional view, respectively, of an all-solid-state battery according to an embodiment of the present invention.

[0019] FIG. 5 is a cross-sectional view of an all-solid-state battery according to one embodiment of the present invention.

[0020] FIG. 6 is a cross-sectional view of an all-solid-state battery including a gasket structure according to one embodiment of the present invention.

[0021] Figure 7 is an enlarged cross-sectional view of the M region of Figure 1.

[0022] FIG. 8 is a scanning electron microscope (SEM) image of a solid electrolyte membrane according to an embodiment of the present invention.

[0023] FIG. 9 is a flowchart illustrating a method for manufacturing a solid electrolyte membrane according to embodiments of the present invention.

[0024] FIG. 10 is a scanning electron microscope (SEM) image of a solid electrolyte membrane according to an embodiment of the present invention.

[0025] Figure 11 is a diagram showing the results of image processing on the SEM image of Figure 10.

[0026]

[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] As used herein, “combination thereof” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the components.

[0033] Unless otherwise defined herein, the particle size may be the average particle size. In addition, the particle size refers to the average particle size (D50), which means the diameter of particles with a cumulative volume of 50% by volume in a particle size distribution. The average particle size (D50) can be measured by a method well known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope (TEM) photograph or a scanning electron microscope (SEM) photograph. Alternatively, the average particle size (D50) value can be obtained by measuring with a measuring device that utilizes dynamic light-scattering, performing data analysis to count the number of particles for each particle size range, and calculating from the counted number. Alternatively, the average particle size (D50) value can be obtained by measuring with a laser diffraction method. When measuring by laser diffraction, more specifically, after the particles to be measured are dispersed in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves of approximately 28 kHz at an output of 60 W, and the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0034] FIG. 1 is a cross-sectional view of an all-solid-state battery (10) according to one embodiment of the present invention.

[0035] Referring to FIG. 1, an all-solid-state battery (10) according to one embodiment includes a cathode layer (100), a cathode layer (200) facing the cathode layer (100), and a solid electrolyte membrane (300) disposed between the cathode layer (100) and the cathode 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 cathode layer (100) and the solid electrolyte membrane (300) or between the cathode layer (200) and the solid electrolyte membrane (300).

[0036] An anode layer (100) of one embodiment includes an anode current collector (110) and an anode active material layer (120) disposed on the anode current collector (110). The anode active material layer (120) may include an anode active material, a solid electrolyte, a conductive material, and a binder.

[0037] The cathode current collector (110) can provide a reference surface on which the cathode active material layer (120) is arranged. The cathode 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.

[0038] Meanwhile, unlike as illustrated in FIG. 1, the positive current collector (110) may be omitted in one embodiment of the present invention. Although not illustrated, a carbon layer with a thickness of 0.1 μm to 4 μm may be further disposed between the positive current collector (110) and the positive active material layer (120) to increase the bonding strength between the positive current collector (110) and the positive active material layer (120).

[0039] The cathode active material layer (120) may include a cathode active material, a solid electrolyte, a conductive material, and a binder.

[0040] The cathode active material is a material that can reversibly absorb and desorb lithium ions. The cathode active material 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, and lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide. The cathode active materials may be used alone or as a mixture of two or more.

[0041] Lithium transition metal oxides are, 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 a Ni 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-fIt is a compound represented by any one of Fe2(PO4)3 (0≤f≤2) or LiFePO4. In such compounds, the uppercase “A” is Ni, Co, Mn, or a combination thereof; the uppercase “B” is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; the uppercase “D” is O, F, S, P, or a combination thereof; the uppercase “E” is Co, Mn, or a combination thereof; the uppercase “F” is F, S, P, or a combination thereof; the uppercase “G” is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; the uppercase “Q” is Ti, Mo, Mn, or a combination thereof; the uppercase “I” is Cr, V, Fe, Sc, Y, or a combination thereof; and the uppercase “J” is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0042] The cathode active material 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 and metal atomic layers are alternately and regularly arranged in a specific direction, thereby forming a two-dimensional plane for each atomic layer. The "cubic rock salt type structure" represents a sodium chloride (NaCl type) structure, which is a type of crystal structure; specifically, it exhibits a structure in which face-centered cubic lattices (fcc) formed by cations and anions, respectively, are offset from each other by half the ridge of the unit lattice. Lithium transition metal oxides having such a layered rock salt type structure, for example, LiNi x Co y Al z O2(NCA) or LiNi x Co y Mn zO2(NCM) (0 <x<1,0<y<1, 0<z<1, x+y+z=1) 등의 삼원계 리튬전이금속산화물일 수 있다. 양극활물질이 층상암염형 구조를 갖는 삼원계 리튬전이금속산화물을 포함하는 경우, 전고체 전지(10)의 에너지 밀도가 커지고 열안정성이 향상될 수 있다.

[0043] The aforementioned compound contained in the cathode active material may be covered by a coating layer (not shown). The cathode active material may also be a mixture of the aforementioned compound and the compound to which the coating layer is added. Meanwhile, the coating layer added to the surface of the cathode active material may include, for example, oxides, hydroxides, oxyhydroxides, oxycarbonates, or hydroxycarbonates of the following coating elements. The compounds forming this coating layer are 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 cathode active material. The method for forming the coating layer is, for example, spray coating or immersion.

[0044] When the positive electrode active material is a ternary lithium transition metal oxide such as NCA or NCM and contains nickel (Ni), the capacity density of the all-solid-state battery (10) is increased, and the metal leaching of the positive electrode active material in the charged state can be reduced. As a result, the cycle characteristics of the all-solid-state battery (10) in the charged state are improved. Meanwhile, “cycle characteristics” is a characteristic that indicates the degree of deterioration of the all-solid-state battery (10) due to charging and discharging of the all-solid-state battery (10). An all-solid-state battery (10) with high cycle characteristics has a small degree of deterioration due to charging and discharging, while an all-solid-state battery (10) with low cycle characteristics may have a large degree of deterioration due to charging and discharging.

[0045] The shape of the cathode active material may include particle shapes such as a sphere or an ellipsoid, for example. The particle size and content of the cathode active material are not particularly limited.

[0046] The solid electrolyte may have a particle shape. The solid electrolyte may be dispersed between the positive electrode active materials. The solid electrolyte 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).

[0047] 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-xI x It may be an argyrodite-type compound including at least one selected from (0≤x≤2). In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0048] Alternatively, sulfide-based solid electrolytes are Li 7-a M a PS 6-c X c (0≤a≤2, (0≤c≤2) may be an argyrodite-type compound containing, where X may be F, Br, Cl, or a combination thereof. M may be scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), It may be indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), or a combination thereof.

[0049] 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 can be 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.

[0050] The solid electrolyte included in the positive electrode active material layer (120) may have a smaller average particle size (D50) compared to the solid electrolyte (SE1) included in the solid electrolyte membrane (300). For example, the average 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 average particle size (D50) of the solid electrolyte (SE1) included in the solid electrolyte membrane (300). Meanwhile, the average particle size (D50) may be a median diameter measured using a laser particle size distribution meter.

[0051] The positive electrode active material layer (120) includes a conductive material. The conductive material may have conductivity without causing chemical changes in the all-solid-state battery (10), thereby increasing the conductivity of the positive electrode active material and the solid electrolyte.

[0052] The conductive material may include a carbon-based material. For example, the conductive material may include one or more selected from graphite, carbon black, acetylene black, carbon nanofibers, and carbon nanotubes.

[0053] The positive active material layer (120) may further include a binder. The binder may include a material for bonding the positive active material, solid electrolyte, and conductive material included in the positive active material layer (120), and for improving the bonding strength with the positive current collector (110). The binder may include, for example, polyvinylidene fluoride, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate.

[0054] Based on 100 parts by weight of the total positive active material, solid electrolyte, conductive material, and binder, the positive active material layer (120) may contain 85 parts by weight or more and 92 parts by weight or less of the positive active material. Based on 100 parts by weight of the total positive active material, solid electrolyte, conductive material, and binder, the positive active material layer (120) may contain 0.5 parts by weight or more and 1.5 parts by weight or less of the binder.

[0055] Based on 100 parts by weight of solid electrolyte, the positive active material layer (120) may contain 1 part by weight or more and 50 parts by weight or less of a conductive material. If the conductive material is included in the positive active material layer (120) in an amount less than 1 part by weight based on 100 parts by weight of solid electrolyte, the proportion of the conductive material decreases, and the electrical conductivity of the positive active material layer (120) may decrease. If the conductive material is included in the positive active material layer (120) in an amount exceeding 50 parts by weight based on 100 parts by weight of solid electrolyte, the proportion of the conductive material is excessively high, and a coating layer covering the surface of the solid electrolyte may not be properly formed.

[0056] The cathode active material layer (120) may further include additives such as fillers, coating agents, dispersants, and ion conductive aids in addition to the cathode active material, solid electrolyte, conductive agent, and binder described above.

[0057]

[0058] Referring to FIG. 1, the negative electrode layer (200) may include a negative electrode current collector (210) and a negative electrode coating layer (220) disposed on the negative electrode current collector (210). The negative electrode coating layer (220) may include a negative electrode active material and a binder.

[0059] The negative electrode current collector (210) may provide a reference surface on which the negative electrode coating layer (220) is placed. The negative electrode current collector (210) may include, for example, a material that does not react with lithium, that is, does not form any alloys or compounds with lithium. The material constituting the negative electrode current collector (210) may be, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not necessarily limited to these, and any material used as an electrode current collector is possible. The thickness of the negative electrode current collector may be 1 to 20 μm, for example 5 to 15 μm, for example 7 to 10 μm.

[0060] 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) is, for example, in the form of a plate or foil. Meanwhile, in one embodiment, the negative electrode current collector (210) may be omitted.

[0061] The cathode active material included in the cathode coating layer (220) may have a particle shape. The intermediate particle size average diameter (D50) of the cathode active material having a particle shape may be, for example, 4 µm or less, 2 µm or less, 1 µm or less, or 900 nm or less. The intermediate particle size average diameter (D50) of the cathode active material may be, for example, 10 nm to 4 µm, 10 nm to 2 µm, or 10 nm to 900 nm. As the cathode active material has an intermediate particle size average diameter (D50) within this range, the reversible absorption and / or desorption of lithium during charging and discharging may be more easily facilitated. Meanwhile, the intermediate particle size average diameter (D50) may be a median diameter measured using a laser particle size distribution meter.

[0062] The negative electrode active material may include, for example, at least one selected from a carbon-based negative electrode active material and a metal or metalloid negative electrode active material.

[0063] The carbon-based negative electrode active material may be amorphous carbon, in particular. Examples of amorphous carbon include, but are not limited to, carbon black (CB), acetylene black (AB), furnace black (FB), ketjen black (KB), and graphene. Amorphous carbon is carbon that has no crystallinity or very low crystallinity, and is distinguished from crystalline carbon or graphitic carbon.

[0064] The metal or metalloid negative electrode active material includes, but is not necessarily limited to, one or more 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 may be a metal negative electrode active material or a metalloid negative electrode active material that forms an alloy or compound with lithium. On the other hand, nickel (Ni) does not form an alloy with lithium and therefore is not a metal negative electrode active material.

[0065] The cathode coating layer (220) includes one type of cathode active material among these cathode active materials, or includes a mixture of a plurality of different cathode active materials. For example, the cathode coating layer (220) may include only amorphous carbon, or may include one or more 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).

[0066] In one embodiment, the negative electrode coating layer (220) may comprise a mixture of amorphous carbon and one or more 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 mixing ratio of the mixture of amorphous carbon and gold (Au), etc., may be, for example, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1 by weight, but is not necessarily limited to these ranges and may be selected according to the required characteristics of the all-solid-state battery (10). By having the negative electrode active material have such a composition, the cycle characteristics of the all-solid-state battery (10) may be further improved.

[0067] The binder included in the cathode coating layer (220) is, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited to these. The binder may include a single binder or a plurality of different binders.

[0068] By including a binder in the cathode coating layer (220), the cathode coating layer (220) can be stably formed on the cathode current collector (210). That is, the bonding strength between the cathode coating layer (220) and the cathode current collector (210) can be increased. In addition, cracking of the cathode coating layer (220) is suppressed despite volume changes and / or relative position changes of the cathode coating layer (220) during the charging and discharging process. If the cathode coating layer (220) does not include a binder, the cathode coating layer (220) can be easily separated from the cathode current collector (210). As the cathode coating layer (220) detaches from the cathode current collector (210), the cathode current collector (210) may come into contact with the solid electrolyte layer in the exposed portion of the cathode current collector (210), and accordingly, the possibility of a short circuit occurring increases.

[0069] The negative electrode coating layer (220) is manufactured, for example, by providing a mixture in which the materials constituting the negative electrode coating layer (220) are dispersed onto the negative electrode current collector (210). Since a binder is included in the materials constituting the negative electrode coating layer (220), stable dispersion of the negative electrode active material in the mixture is possible. For example, when applying the mixture onto the negative electrode current collector (210) by screen printing, it is possible to suppress clogging of the screen (e.g., clogging by aggregates of the negative electrode active material) by the binder.

[0070] The cathode coating layer (220) may further include other additives in addition to the cathode active material and binder. The cathode coating layer (220) may further include, for example, fillers, coating agents, dispersants, ion conductive aids, etc.

[0071] 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 all-solid-state battery (10).

[0072] If the thickness of the cathode coating layer (220) is reduced, for example, the charging capacity of the cathode coating layer (220) may also be reduced. The charging capacity of the cathode coating layer (220) is, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, 5% or less, or 2% or less compared to the charging capacity of the positive active material layer (120). The charging capacity of the cathode coating layer (220) is, for example, 0.1% to 50%, 0.1% to 40%, 0.1% to 30%, 0.1% to 20%, 0.1% to 10%, 0.1% to 5%, or 0.1% to 2% compared to the charging capacity of the positive active material layer (120). If the charging capacity of the cathode coating layer (220) is excessively small, the thickness of the cathode coating layer (220) becomes very thin, and the same defect as the aforementioned defect that occurs when the thickness of the cathode coating layer (220) becomes excessively thin may occur. If the charging capacity of the cathode coating layer (220) increases excessively, the same defect as the aforementioned defect that occurs when the thickness of the cathode coating layer (220) increases excessively may occur.

[0073] For example, the charge capacity of the positive active material layer (120) can be obtained by multiplying the charge capacity density (mAh / g) of the positive active material by the mass of the positive active material in the positive active material layer (120). If the positive active material layer (120) contains various types of positive active materials, the value [charge capacity density × mass] is calculated for each positive active material, and the sum of these values ​​of the positive active materials is the charge capacity of the positive active material layer (120). The charge capacity of the negative coating layer (220) can also be calculated in the same way. That is, the charge capacity of the negative coating layer (220) is obtained by multiplying the charge capacity density (mAh / g) of the negative active material by the mass of the negative active material in the negative coating layer (220). When the negative electrode coating layer (220) contains various types of negative electrode active materials, the value [charge capacity density × mass] is calculated for each negative electrode active material, and the sum of these values ​​of the negative electrode active materials is the capacity of the negative electrode coating layer (220). Here, the charge capacity density of the positive electrode active material and the negative electrode active material may be the capacity estimated using an all-solid-state half-cell using lithium metal as the counter electrode. The charge capacity of the positive electrode active material layer (120) and the negative electrode coating layer (220) can be directly measured by measuring the charge capacity using an all-solid-state half-cell. By dividing the measured charge capacity by the mass of each active material, the charge capacity density can be obtained. Meanwhile, in this specification, the “charge capacity” of the positive electrode active material layer (120) and the negative electrode coating layer (220) refers to the initial charge capacity measured during the first cycle of charging.

[0074] Meanwhile, although not shown, a carbon layer may be further included to improve adhesion between the cathode coating layer (220) and the solid electrolyte membrane (300).

[0075] Referring to FIG. 1, a solid electrolyte membrane (300) is positioned between the anode layer (100) and the cathode layer (200). The solid electrolyte membrane (300) will be described later with reference to FIG. 7.

[0076]

[0077] FIG. 2 is a cross-sectional view of an all-solid-state battery (10) according to another embodiment of the present invention.

[0078] Referring to FIG. 2, the solid electrolyte membrane (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 anode layer (100), and the second solid electrolyte layer (320) may be adjacent to the cathode layer (200).

[0079] 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 the second thickness (TK2).

[0080]

[0081] FIG. 3 is a plan view of an all-solid-state battery (10) according to another embodiment of the present invention. FIG. 4 is a cross-sectional view along the line A-A' of FIG. 3. In this embodiment, detailed descriptions of technical features that overlap with those previously described with reference to FIG. 1 and FIG. 2 are omitted, and differences are described in detail.

[0082] Referring to FIGS. 3 and 4, the area of ​​the anode layer (100) and the area of ​​the cathode layer (200) may differ 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 superimposed within the cathode layer (200).

[0083] In one embodiment of the present invention, the first solid electrolyte layer (310) may have substantially the same area as the anode layer (100). The second solid electrolyte layer (320) may have substantially the same area as the cathode layer (200).

[0084] Specifically, the first solid electrolyte layer (310) may have a first width (WI1) in the 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).

[0085] 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.

[0086]

[0087] FIG. 5 is a cross-sectional view along line A-A' of FIG. 3, intended to illustrate an all-solid-state battery according to another embodiment of the present invention.

[0088] 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 increase further during charging of the all-solid-state battery (10). The negative electrode coating layer (220) acts as a protective layer for the lithium metal layer (400) and, at the same time, can suppress the growth of lithium dendrites from the lithium metal layer (400).

[0089] The lithium metal layer (400) may be a thin metal film containing lithium or a lithium alloy. The lithium alloy is not limited to, for example, Li-Al alloy, Li-Sn alloy, Li-In alloy, Li-Ag alloy, Li-Au alloy, Li-Zn alloy, Li-Ge alloy, Li-Si alloy, etc., and any alloy used as a lithium alloy is possible. 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.

[0090] 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).

[0091]

[0092] FIG. 6 is a cross-sectional view illustrating an all-solid-state battery according to another embodiment of the present invention.

[0093] Referring to FIG. 6, the all-solid-state battery (10) may include a gasket structure (400). The gasket structure (400) can fill the step difference on the side of the all-solid-state battery (10) caused by the difference in area between the first laminate and the second laminate. The gasket structure (400) can surround the sides of the first laminate of the all-solid-state battery (10) along the first and second directions (D1, D2). For example, the thickness of the gasket structure (400) may be substantially the same as the thickness of the first laminate. This prevents damage to the step difference on the side of the all-solid-state battery even when the first laminate and the second laminate, which have different areas, are laminated and pressed. "Substantially the same thickness" may be defined as a thickness sufficient to prevent damage to the step difference on the side of the all-solid-state battery even when the first laminate and the second laminate, which have different areas, are laminated and pressed.

[0094]

[0095] FIG. 7 is an enlarged view of a cross-section of a solid electrolyte membrane (300) according to one embodiment of the present invention, which is an enlarged view of area M of FIG. 1. Referring to FIG. 7, the solid electrolyte membrane (300) may include a first solid electrolyte (SE1) having a particle form and a second solid electrolyte (SE2) having a fine powder form.

[0096] When the solid electrolyte membrane (300) contains a large amount of solid electrolyte in the form of particles (average particle size 2 μm to 10 μm), the ion conductivity in the powder state may be excellent. However, after being formed into a solid electrolyte membrane, a large amount of unfilled pores may exist between the solid electrolyte particles, and this may act as resistance during cell operation, thereby degrading the capacity characteristics or rate characteristics of the cell.

[0097] When the solid electrolyte membrane (300) contains a large amount of solid electrolyte in the form of fine particles (fine particles with a long axis length of 1 μm or less), the pores of the manufactured solid electrolyte membrane may be reduced, and the resistance due to the pores may be reduced. However, in this case, the grain boundaries of the particles increase, which may increase the occurrence of side reactions. If side reactions increase, the lifespan characteristics of the battery may be degraded.

[0098] The solid electrolyte membrane (300) according to the present invention can have excellent life characteristics along with excellent capacity and rate characteristics by including a first solid electrolyte (SE1) having a particle form and a second solid electrolyte (SE2) having a fine powder form in an appropriate ratio.

[0099] In one embodiment, the weight ratio of the second solid electrolyte to the total weight of the first and second solid electrolytes may be 10 wt% to 30 wt%, or 20 wt% to 30 wt%. When the content of the second solid electrolyte satisfies the range described above, the all-solid-state battery may have excellent rate characteristics and life characteristics.

[0100] A solid electrolyte membrane (300) according to one embodiment may have a porosity of 1% to 5%, 2% to 5%, or 2% to 4% as measured by a scanning electron microscope (SEM) image. Such porosity may be a characteristic that the solid electrolyte membrane possesses by including an appropriate amount of fine particles. In one embodiment, the porosity may be obtained by performing image processing on an SEM image of a pressurized solid electrolyte membrane (e.g., using the Image J program). Specifically, by performing image processing on an SEM image to separate solid electrolyte particles, the porosity may be measured by considering the remaining portion of the total area, excluding the portion occupied by the solid electrolyte particles, as a porosity.

[0101] In this specification, a fine-form solid electrolyte may refer to a solid electrolyte with a size of 1 μm or less. The size of the solid electrolyte may refer to the length of the major axis measured by scanning electron microscopy. The fine-form solid electrolyte does not have a fixed shape and may have various sizes and shapes within a range not exceeding 1 μm. The fine-form solid electrolyte may be identified during the membrane manufacturing process. Referring to FIG. 8, in the state of the manufactured membrane, the fine-form solid electrolyte may exist in the form of aggregates clustered together.

[0102] In one embodiment, the first average particle diameter of the first solid electrolyte may be 2 μm to 10 μm, 2 μm to 6 μm, or 2 μm to 4 μm. If the first average particle diameter is excessively small, the life characteristics of the all-solid-state battery may deteriorate due to an increase in particle boundaries within the solid electrolyte membrane. If the first average particle diameter is excessively large, the capacity characteristics and rate characteristics of the all-solid-state battery may deteriorate due to an increase in pores in the solid electrolyte membrane. If the first average particle diameter satisfies the above-described range, the all-solid-state battery may have excellent life and capacity characteristics. Meanwhile, the first average particle diameter may be a median diameter measured using a laser particle size distribution analyzer.

[0103] Each of the first and second solid electrolytes (SE1, SE2) may be a sulfide-based solid electrolyte. The sulfide-based solid electrolyte may include at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements. For example, the sulfide-based solid electrolyte may include a material including Li2S-P2S5. When using a sulfide-based solid electrolyte material including Li2S-P2S5, the mixing molar ratio of Li2S and P2S5 may be, for example, in the range of Li2S:P2S5=50:50 to 90:10.

[0104] 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 It may be an argyrodite-type compound including at least one selected from (0≤x≤2). In particular, the sulfide-based solid electrolyte may be an argyrodite-type compound including at least one selected from Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0105] Alternatively, sulfide-based solid electrolytes are Li 7-a M a PS 6-c X c It may be an argyrodite-type compound containing (0≤a≤2, 0≤c≤2). Here, X may be F, Br, Cl, or a combination thereof. M is scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), technetium (Tc), rhenium (Re), iron (Fe), ruthenium (Ru), osmium (Os), cobalt (Co), rhodium (Rh), iridium (Ir), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), mercury (Hg), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi) or these. It could be a combination.

[0106] The density of the argyrodite-type solid electrolyte may be 1.5 g / cc to 2.0 g / cc. When 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 is, for example, 15 GPa to 35 GPa.

[0107] The solid electrolyte membrane (300) may further include a binder (BND). The binder (BND) included in the solid electrolyte membrane (300) is, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited thereto. For example, the binder (BND) may include at least one selected from the group consisting of styrene butadiene rubber, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyvinyl alcohol, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, and polymethyl methacrylate. The content of the binder (BND) of the solid electrolyte membrane (300) may be 0.5 to 10 parts by weight per 100 parts by weight of the solid electrolyte membrane.

[0108]

[0109] Hereinafter, a method for manufacturing a solid electrolyte membrane according to embodiments of the present invention will be described in more detail.

[0110] A method for manufacturing a solid electrolyte membrane according to one embodiment may include preparing a sulfide-based solid electrolyte; mixing the sulfide-based solid electrolyte and a binder to manufacture a solid electrolyte membrane; and applying the solid electrolyte slurry.

[0111] Referring to FIG. 9, preparing a sulfide-based solid electrolyte comprises mixing raw materials in powder form to form a mixture (S100), calcining the mixed mixture (S200), and performing a grinding process on the calcined mixture to form a first solid electrolyte in the form of particles and a second solid electrolyte in the form of fine powder (S300), wherein the grinding process can be controlled so that the second solid electrolyte is 10 wt% to 30 wt% of the total weight of the first and second solid electrolytes.

[0112] The raw materials in powder form can be mixed (S100). For example, the raw materials can be processed by melt quenching or mechanical milling.

[0113] In the melt-quenching method, starting materials can be mixed and formed into pellets. The pellets can be reacted at a predetermined reaction temperature and under vacuum conditions. For example, the reaction temperature can be 400°C to 1000°C, preferably 800°C to 900°C. For example, the reaction time can be 0.1 hour to 12 hours, preferably 1 hour to 12 hours. Thereafter, the pellets can be quenched. For example, the quenching temperature can be 10°C or lower, preferably 0°C or lower. For example, the quenching rate can be 1°C / sec to 10,000°C / sec, preferably 1°C / sec to 1000°C / sec.

[0114] In the mechanical milling method, the raw materials can be stirred using a ball mill or the like. For example, the stirring speed can be 300 rpm to 10,000 rpm, 350 rpm to 5,000 rpm, or 370 rpm to 1,000 rpm. For example, the stirring time can be 10 to 1,000 hours, 10 to 100 hours, or 10 to 30 hours. The stirring speed and stirring time are not particularly limited, but a fast stirring speed can accelerate the production speed of the solid electrolyte, and a long stirring time can increase the production rate of the solid electrolyte. The stirring can be performed under an inert atmosphere. The inert atmosphere can be, for example, an atmosphere containing nitrogen, argon, neon, helium, or a combination thereof.

[0115] To obtain the desired solid electrolyte, the stoichiometric molar ratio of the powdered raw materials can be changed, and the content of each powdered raw material can be changed.

[0116] The powder-state raw materials may include sulfur (S) precursors, phosphorus (P) precursors, etc. For example, the powder-state raw materials may include Li2S, P2S5, etc. The powder-state raw materials may further include halogen precursors, metal precursors, etc. For example, the halogen precursors may include fluorine (F) precursors, chlorine (Cl) precursors, bromine (Br) precursors, iodine (I) precursors, etc. For example, the metal precursors may include magnesium (Mg) precursors, silver (Ag) precursors, copper (Cu) precursors, etc.

[0117] The mixed mixture can be calcined under an inert atmosphere (S200). For example, the inert atmosphere can be an atmosphere containing nitrogen, argon, neon, helium, or a combination thereof. The calcination can be performed at a predetermined temperature. For example, the calcination temperature can be from 0°C to 1000°C. For example, the calcination time can be from 1 hour to 48 hours.

[0118] The calcined mixture can be pulverized (S300). The pulverization method is not particularly limited, and can be dry pulverization or wet pulverization in a solvent. Examples of pulverization equipment that can be used include a planetary mill, a ball mill, a jet mill, a hammer mill, and a rotary mill. The calcined mixture can be pulverized using two or more pulverization methods.

[0119] In one embodiment, the grinding process may include a primary particle size control step of the solid electrolyte through dry milling, and a fine powder content control step through wet milling.

[0120] For example, a jet mill can be used for dry milling, and the milling speed of the jet mill can be about 100 rpm to 10,000 rpm, 500 rpm to 10,000 rpm, or 1,000 rpm to 10,000 rpm. The milling time of the jet mill can be 0.5 hours to 50 hours, 1 hour to 30 hours, or 1 hour to 24 hours. Dry milling can be performed at 0.1 MPa to 10 MPa, 1 MPa to 5 MPa, or 1 MPa to 3 MPa.

[0121] For example, a planetary mill containing zirconia balls may be used for wet milling. The stirring speed of the wet milling may be 300 rpm to 10,000 rpm, 350 rpm to 5,000 rpm, or 370 rpm to 1,000 rpm. The time of the wet milling may be, for example, 3 to 10 hours, 4 to 20 hours, or 5 to 10 hours. The wet milling may be performed in a solvent, and the solvent may be a non-polar solvent such as xylene or toluene.

[0122] As described above, the desired content of fine powder can be achieved by controlling the type and process conditions of the grinding process.

[0123] In the solid electrolyte manufactured as described above, the content of the second solid electrolyte in a fine powder form may be 10 wt% to 30 wt% with respect to the total weight of the first and second solid electrolytes. In the solid electrolyte, the average particle diameter of the first solid electrolyte in a particle form may be 2 μm to 4 μm.

[0124]

[0125] Hereinafter, the present invention will be described in more detail through examples. However, these examples are intended to exemplify the present invention and the scope of the present invention is not limited to these examples.

[0126]

[0127] Example 1

[0128] (Solid Electrolyte Manufacturing)

[0129] As raw materials for a sulfide-based solid electrolyte, Li2S powder, P2S5 powder, and LiCl powder were prepared in stoichiometric ratios to have a composition of Li6PS5Cl. The above raw materials and zirconia balls with a diameter of 5 mm were placed in a container with an internal volume of 70 ml, milled with a ball milling machine at room temperature under an Ar atmosphere for 24 hours, and reacted mechanochemically to form a mixture.

[0130] The above mixture was placed in a carbon crucible and subjected to a first heat treatment (sintering) process at 450°C to 550°C for 5 to 10 hours under an Ar atmosphere to manufacture a solid electrolyte precursor.

[0131] The obtained precursor was coarsely ground to adjust the particle size to several tens of μm, and then finely ground.

[0132] First, the particle size is controlled primarily by dry grinding the solid electrolyte precursor using a jet mill. Dry grinding was performed for 4 hours at an ejection pressure and side pressure of approximately 2 MPa and a stirring speed of 3,000 rpm.

[0133] First, a solid electrolyte with controlled particle size and zirconia balls were placed in a xylene solvent and ball milled using a planetary mill. Ball milling was performed at 450 rpm for 4 hours. The powder obtained through milling was dried in a vacuum oven at 80°C for 2 hours.

[0134] The content of fine particles with a major axis length of 1 μm or less in the manufactured sulfide-based solid electrolyte was 10 wt%, and the average particle diameter (D50) of the solid electrolyte in particle form excluding the fine particles was approximately 3 μm.

[0135]

[0136] (All-solid-state battery manufacturing)

[0137] (1) Preparation of solid electrolyte membrane

[0138] A solid electrolyte slurry was prepared by adding the above-prepared solid electrolyte to an isobutylyl isobutylate binder solution to which an acrylate-based polymer was added (solid content: 50 wt%, mixing ratio of solid electrolyte to binder: 98.7: 1.3 wt%).

[0139] The above solid electrolyte solution was applied to a heterogeneous polytetrafluoroethylene film and dried at 60°C for 2 hours to produce a solid electrolyte layer having a thickness of 100 μm.

[0140] (2) Manufacturing of cathode layer

[0141] A 10-μm-thick Ni foil was prepared as a negative electrode current collector. In addition, carbon black (CB) with a primary particle diameter of approximately 30 nm and silver (Ag) particles with an average particle diameter of approximately 60 nm were prepared as negative electrode active materials. 0.25 g of a mixed powder of carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1 was placed in a container, and 2 g of an NMP solution containing 7 wt% PVDF binder (Kureha #9300) was added thereto to prepare a mixed solution. Next, NMP was gradually added to the mixed solution while stirring the mixed solution to prepare a slurry. The prepared slurry was applied to a Ni foil using a bar coater and dried in a convection oven at 80°C for 10 minutes to obtain a laminate. The obtained laminate was vacuum-dried at 100°C for more than 8 hours, i.e., for 10 hours. A cathode layer was manufactured by forming a cathode coating layer on a cathode current collector through the above process.

[0142] (3) Manufacturing of anode layer

[0143] LiNi as a cathode active material 0.8 Co 0.15 Mn 0.05O2(NCM) was prepared. Li6PS5Cl solid electrolyte (D50=1 um or less, crystalline) in the form of argyrodite was used as a solid electrolyte. Polytetrafluoroethylene (PTFE) binder (Teflon binder from DuPont) was prepared as a binder. Carbon black (CB) and carbon nanofibers (CNF) were prepared as conductive agents. These materials were mixed with a xylene solvent in a weight ratio of positive electrode active material: solid electrolyte: carbon black: carbon nanofiber: binder = 85.5:10:1.5:1.5:1.5, and the positive electrode active material composition was molded into a sheet shape, and then vacuum dried at 40°C for 8 hours to manufacture a positive electrode sheet.

[0144] (4) All-solid manufacturing

[0145] A laminate was prepared by placing a solid electrolyte layer between the positive and negative electrode layers. The prepared laminate was hot-plate pressed at 80°C and a pressure of 500 MPa for 10 minutes to produce an all-solid-state battery. This pressurization process sintered the solid electrolyte layer, thereby improving battery characteristics. The thickness of the pressed positive active material layer was approximately 80 μm, the thickness of the negative active material layer was 7 μm, and the thickness of the solid electrolyte layer was 60 μm.

[0146]

[0147] Example 2

[0148] (Solid Electrolyte Manufacturing)

[0149] A solid electrolyte was prepared in the same manner as in Example 1, except that the solid electrolyte with controlled particle size was milled in a planetary mill at 450 rpm for 8 hours.

[0150] The content of fine particles with a major axis length of 1 μm or less in the manufactured sulfide-based solid electrolyte was 20 wt%, and the average particle diameter (D50) of the solid electrolyte in particle form excluding the fine particles was approximately 3 μm.

[0151] (All-solid-state battery manufacturing)

[0152] An all-solid-state battery was manufactured using the same method as in Example 1.

[0153]

[0154] Example 3

[0155] (Solid Electrolyte Manufacturing)

[0156] A solid electrolyte was prepared in the same manner as in Example 1, except that the solid electrolyte with controlled particle size was milled in a planetary mill at 450 rpm for 18 hours.

[0157] The content of fine particles with a major axis length of 1 μm or less in the manufactured sulfide-based solid electrolyte was 30 wt%, and the average particle diameter (D50) of the solid electrolyte in particle form excluding the fine particles was approximately 3 μm.

[0158] (All-solid-state battery manufacturing)

[0159] An all-solid-state battery was manufactured using the same method as in Example 1.

[0160]

[0161] Example 4

[0162] (Solid Electrolyte Manufacturing)

[0163] For primary particle size control, a solid electrolyte was prepared in the same manner as in Example 1, except that the solid electrolyte precursor was milled using a jet mill at an eject pressure and side pressure of approximately 2 MPa and a stirring speed of 3000 rpm for 10 hours.

[0164] The content of fine particles with a major axis length of 1 μm or less in the manufactured sulfide-based solid electrolyte was 20 wt%, and the average particle diameter (D50) of the solid electrolyte in particle form excluding the fine particles was approximately 2.5 μm.

[0165] (All-solid-state battery manufacturing)

[0166] An all-solid-state battery was manufactured using the same method as in Example 1.

[0167]

[0168] Example 5

[0169] (Solid Electrolyte Manufacturing)

[0170] For primary particle size control, a solid electrolyte was prepared in the same manner as in Example 1, except that the solid electrolyte precursor was milled using a jet mill at an eject pressure and side pressure of approximately 2 MPa and a stirring speed of 3000 rpm for 15 hours.

[0171] The content of fine particles with a major axis length of 1 μm or less in the manufactured sulfide-based solid electrolyte was 20 wt%, and the average particle diameter (D50) of the solid electrolyte in particle form excluding the fine particles was approximately 2.1 μm.

[0172] (All-solid-state battery manufacturing)

[0173] An all-solid-state battery was manufactured using the same method as in Example 1.

[0174]

[0175] Comparative Example 1

[0176] (Preparation of solid electrolyte)

[0177] A solid electrolyte was prepared in the same manner as in Example 1, except that the solid electrolyte with controlled particle size was milled in a planetary mill at 450 rpm for 36 hours.

[0178] The content of fine particles having a major axis length of 1 μm or less in the manufactured sulfide-based solid electrolyte was 50 wt%, and the average particle diameter (D50) of the solid electrolyte in particle form excluding the fine particles was approximately 3 μm.

[0179] (All-solid-state battery manufacturing)

[0180] An all-solid-state battery was manufactured using the same method as in Example 1.

[0181]

[0182] Comparative Example 2

[0183] (Preparation of solid electrolyte)

[0184] A solid electrolyte was prepared in the same manner as in Example 1, except that the solid electrolyte with controlled particle size was milled in a planetary mill at 450 rpm for 2 hours.

[0185] The content of fine particles having a major axis length of 1 μm or less in the manufactured sulfide-based solid electrolyte was 5 wt%, and the average particle diameter (D50) of the solid electrolyte in particle form excluding the fine particles was approximately 3 μm.

[0186] (All-solid-state battery manufacturing)

[0187] An all-solid-state battery was manufactured using the same method as in Example 1.

[0188]

[0189] Comparative Example 3

[0190] (Preparation of solid electrolyte)

[0191] A solid electrolyte was prepared in the same manner as in Example 1, except that the solid electrolyte with controlled particle size was milled in a planetary mill at 450 rpm for 30 hours.

[0192] The content of fine particles having a major axis length of 1 μm or less in the manufactured sulfide-based solid electrolyte was 40 wt%, and the average particle diameter (D50) of the solid electrolyte in particle form excluding the fine particles was approximately 3 μm.

[0193] (All-solid-state battery manufacturing)

[0194] An all-solid-state battery was manufactured using the same method as in Example 1.

[0195]

[0196] Table 1 below shows the grinding conditions of the solid electrolytes of Examples 1 to 5 and Comparative Examples 1 to 3 described above.

[0197] Classification 1st Milling (for Jet Mill) 2nd Milling (for Ball Mill) Eject and Side Pressure Stirring Speed Time (hr) Stirring Speed Time (hr) Example 1 2 MPa 3000 rpm 4450 rpm 4 Example 2 2 MPa 3000 rpm 4450 rpm 8 Example 3 2 MPa 3000 rpm 4450 rpm 18 Example 4 2 MPa 3000 rpm 10450 rpm 8 Example 5 2 MPa 3000 rpm 15450 rpm 8 Comparative Example 12 MPa 3000 rpm 4450 rpm 36 Comparative Example 22 MPa 3000 rpm 4450 rpm 2 Comparative Example 32 MPa 3000 rpm 4450 rpm 30

[0198] Evaluation Example 1: Porosity of solid electrolyte membrane

[0199] The porosity of the solid electrolyte membrane manufactured in Example 3 was measured. The porosity was measured by performing image processing on SEM images of the pressurized solid electrolyte membrane (using the Image J program). Specifically, the solid electrolyte (including both fine and particle forms) was selected by performing image processing on the SEM images, and the porosity was calculated by considering the remaining area, excluding the area occupied by the solid electrolyte, as pores.

[0200] Referring to Fig. 10, which is an SEM image of the solid electrolyte membrane, and Fig. 11, which is an image of Fig. 10 after image processing, it can be seen that in the solid electrolyte membrane prepared in Example 3, the image-processed solid electrolyte accounts for 97.1% and the remaining portion accounts for 2.9%, so the porosity is 2.9%.

[0201]

[0202] Evaluation Example 2: Battery Capacity Characteristics Evaluation

[0203] Rate characteristics were evaluated for all-solid-state batteries according to Examples 1 to 5 and Comparative Examples 1 to 3.

[0204] To verify the cell rate characteristics, the discharge capacity of each of the all-solid-state batteries of the examples and comparative examples was investigated. The charge-discharge test was performed by placing the all-solid-state batteries in a constant temperature bath at 60°C.

[0205] The battery was charged at a constant current of 0.1 C for 10 hours until the battery voltage became 4.25 V, and then discharged at a constant current of 0.1 C for 10 hours until the battery voltage became 2.5 V (the first cycle). Subsequently, the battery was charged at a constant current of 0.1 C for 10 hours until the battery voltage became 4.25 V, and then discharged at a constant current of 0.33 C for 3 hours until the battery voltage became 2.5 V (the second cycle). Subsequently, the battery was charged at a constant current of 0.1 C for 10 hours until the battery voltage became 4.25 V. Subsequently, the battery was discharged at a constant current of 0.5 C for 2 hours until the battery voltage became 2.5 V (the third cycle). Subsequently, the battery was charged at a constant current of 0.1 C for 10 hours until the battery voltage became 4.25 V. Next, discharge was performed for 1 hour at a constant current of 1C until the battery voltage reached 2.5 V (4th cycle).

[0206] The rate characteristics were calculated according to the following mathematical formula 1, and the results are shown in Table 2.

[0207] <Mathematical Formula 1>

[0208] Rate characteristics [%] = [0.33C discharge capacity / 0.1C discharge capacity] × 100

[0209]

[0210] Evaluation Example 3: Battery Life Characteristics Evaluation

[0211] The life characteristics of the all-solid-state batteries according to Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated. Charge and discharge tests were performed by placing the all-solid-state batteries in a 60°C constant temperature chamber.

[0212] The first cycle involved charging at a constant current of 0.33 C for approximately 3 hours until the battery voltage reached 4.25 V. Afterwards, discharging was performed at a constant current of 0.33 C for approximately 3 hours until the battery voltage reached 2.5 V.

[0213] After the second cycle, charging and discharging were performed up to 100 cycles under the same conditions as the first cycle. The capacity retention rate was calculated using the following mathematical equation (2), and the results are shown in Table 2.

[0214] <Mathematical Formula 2>

[0215] Capacity retention rate [%] = [Discharge capacity at the 100th cycle / Discharge capacity at the 1st cycle] × 100

[0216]

[0217] ClassificationMedian particle size (㎛)Fine powder content (wt%)Rate evaluation0.33C / 0.1C(%)Capacity retention @100cycle(%)Example 131092.199.1Example 232093.299.6Example 333094.899.8Example 42.52095.299.8Example 52.12095.599.7Comparative example 135095.689.9Comparative example 23590.288.5Comparative example 334095.690.1

[0218] Referring to Table 1, it can be confirmed that the lithium secondary batteries according to the examples have significantly superior life characteristics while having similar level of rate characteristics compared to the lithium secondary batteries according to the comparative examples.

[0219] While the 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, the embodiments described above should be understood to be illustrative in all respects and not restrictive.

Claims

1. A first solid electrolyte having a particle shape and a first average particle diameter (D50); and A second solid electrolyte having a differential shape and a major axis length of 1 μm or less, The above first average particle diameter (D50) is 2 μm to 10 μm, The weight ratio of the second solid electrolyte to the total weight of the first and second solid electrolytes is 10 wt% to 30 wt%, Solid electrolyte membrane.

2. In paragraph 1, The weight ratio of the second solid electrolyte to the total weight of the first and second solid electrolytes is 20 wt% to 30 wt%, Solid electrolyte membrane.

3. In paragraph 1, The above first average particle diameter (D50) is 2 μm to 4 μm, Solid electrolyte membrane.

4. In paragraph 1, The porosity of the above solid electrolyte membrane is 1% to 5%, Solid electrolyte membrane.

5. In paragraph 1, Each of the first and second solid electrolytes is a sulfide-based solid electrolyte. Solid electrolyte membrane.

6. In paragraph 1, Each of the first and second solid electrolytes is Li 7-x PS 6-x Cl x (0≤x≤2), Li 7-x PS 6-x Br x (0≤x≤2), Li 7-x PS 6-x I x (0≤x≤2), and Li 7-y M1 y PS 6-z M2 z Including one or more selected from among The above M1 is one or more elements selected from groups 3 to 15 of the periodic table, The above M2 is one or more elements selected from group 17 of the periodic table, 0≤x≤2, 0≤y≤2, and 0≤z≤2, Solid electrolyte membrane.

7. In paragraph 1, Including more binders, Solid electrolyte membrane.

8. In paragraph 7, The content of the above binder is 1 to 5 parts by weight based on 100 parts by weight of the solid electrolyte. Solid electrolyte membrane.

9. Solid electrolyte membrane according to Article 1; A cathode comprising a cathode current collector and a cathode active material layer; and A cathode including a cathode current collector and a coating layer; All-solid-state battery.

10. In paragraph 9, The above positive electrode active material layer includes a positive electrode active material and a solid electrolyte. All-solid-state battery.

11. In paragraph 9, The above coating layer comprises a metal and a carbon-based material. All-solid-state battery.

12. In paragraph 9, The negative electrode further includes a lithium metal layer between the negative electrode current collector and the coating layer. All-solid-state battery.

13. Preparing a sulfide-based solid electrolyte; Forming a solid electrolyte slurry by mixing the above sulfide-based solid electrolyte and a binder; and Including applying the above solid electrolyte slurry to a substrate, Preparing the above sulfide-based solid electrolyte: Mixing raw materials in a powder state to form a mixture, wherein the raw materials in a powder state include a sulfur precursor, a phosphorus precursor, and a halogen precursor; calcining the above mixed mixture; and Comprising performing a pulverization process on the above-mentioned mixture to form a first solid electrolyte in the form of particles and a second solid electrolyte in the form of fine powder, The above grinding process is controlled so that the second solid electrolyte is 10 wt% to 30 wt% based on the total weight of the first and second solid electrolytes. Method for manufacturing a solid electrolyte membrane.

14. In paragraph 13, The above grinding process is dry grinding, and a jet mill is used as equipment. Method for manufacturing a solid electrolyte membrane.

15. In paragraph 14, The above dry grinding is performed at a speed of 1,000 rpm to 10,000 rpm for 1 to 24 hours. Method for manufacturing a solid electrolyte membrane.

16. In paragraph 13, The above grinding process is a wet grinding process, and a planetary mill equipment is used. Method for manufacturing a solid electrolyte membrane.

17. In paragraph 16, The above wet grinding is performed at a speed of 350 rpm to 5000 rpm for 4 to 20 hours. Method for manufacturing a solid electrolyte membrane.

18. In paragraph 13, The porosity of the above solid electrolyte membrane is 1% to 5%, Method for manufacturing a solid electrolyte membrane.

Images