Binder composition for sulfide-based solid electrolyte, slurry composition for sulfide-based solid electrolyte, method for manufacturing same, and solid electrolyte sheet and all-solid-state battery manufactured using same

Abstract

The present invention relates to a binder composition for a sulfide-based solid electrolyte comprising: a binder including a repeating unit derived from vinylidene fluoride, a repeating unit derived from trifluoroethylene, and a repeating unit derived from chlorotrifluoroethylene; and a non-aqueous solvent.

Description

Binder composition for sulfide-based solid electrolytes, slurry composition for sulfide-based solid electrolytes, method for manufacturing the same, solid electrolyte sheet manufactured using the same, and all-solid-state battery

[0001] The present invention relates to a binder composition for a sulfide-based solid electrolyte, a slurry composition for a sulfide-based solid electrolyte, a method for manufacturing the same, a solid electrolyte sheet manufactured using the same, and an all-solid-state battery.

[0002] This application claims priority to Korean Patent Application No. 10-2024-0190718, filed on December 19, 2024, the entire contents of which are incorporated herein by reference.

[0003] With the recent increase in demand for electric vehicles, the demand for high-energy, high-output lithium-ion batteries is also rising. Lithium-ion batteries have the advantage of higher energy density and greater capacity per unit area compared to nickel-manganese or nickel-cadmium batteries.

[0004] However, conventional lithium-ion batteries mainly used flammable organic liquid electrolytes as electrolytes, which caused safety issues such as overheating. Recently, all-solid-state batteries using non-flammable solid electrolytes have been gaining attention.

[0005] All-solid-state batteries are batteries that ensure safety by replacing liquid electrolytes, which cause explosions, with solid electrolytes, thereby eliminating the use of flammable solvents within the battery and preventing any ignition or explosion caused by the decomposition reaction of conventional electrolytes. The theoretical energy density of all-solid-state batteries is 2,600 Wh / kg, which is a high level of energy density compared to conventional lithium-ion batteries.

[0006] Inorganic solid electrolytes are generally used in all-solid-state batteries. Among solid electrolytes, sulfides are characterized by high ionic conductivity and relative flexibility, making it easy to form solid-solid interfaces. Additionally, they are stable with respect to active materials, leading to various ongoing studies on sulfide-based solid electrolytes.

[0007] Currently, solid electrolytes are manufactured by producing sheets based on pellets or slurries compressed at high temperature and high pressure. However, to ensure the uniformity and flexibility of solid electrolyte sheets and to mass-produce solid electrolytes, technology to increase the sheet area is required. Accordingly, a wet-based process using organic solvents is required for the manufacture of sulfide-based solid electrolytes.

[0008] One objective of the present invention is to provide a PVDF-based binder composition dissolved in an ester-based solvent.

[0009] Another objective of the present invention is to provide a sulfide-based solid electrolyte slurry composition comprising the aforementioned binder composition and a method for manufacturing the same.

[0010] Another objective of the present invention is to provide a sulfide-based solid electrolyte sheet with a large surface area and uniformity and flexibility, including the aforementioned sulfide-based solid electrolyte slurry composition, and a method for manufacturing the same.

[0011] Another objective of the present invention is to provide an all-solid-state battery comprising the aforementioned solid electrolyte sheet.

[0012] A binder composition for a sulfide-based solid electrolyte according to one embodiment of the present invention comprises: a binder comprising repeating units derived from vinylidene fluoride, repeating units derived from trifluoroethylene, and repeating units derived from chlorotrifluoroethylene; and an ester-based solvent.

[0013] The above ester-based solvent may include at least one of isobutyl isobutyrate, isobutyl butyrate, amyl butyrate, ethyl hexanoate, hexyl acetate, hexyl propionic acid, isoamyl butyrate, and isoamyl isovalerate.

[0014] The content of the binder may be 3 to 15 weight percent based on the total binder composition.

[0015] A slurry composition for a sulfide-based solid electrolyte according to another embodiment of the present invention comprises: a sulfide-based solid electrolyte comprising a Li element, a P element, and an S element; a binder composition; and a solvent having a specific gravity of 0.8 to 3.0; and may comprise a binder comprising repeating units derived from vinylidene fluoride, repeating units derived from trifluoroethylene, and repeating units derived from chlorotrifluoroethylene; and an ester-based solvent.

[0016] The average particle size of the above sulfide-based solid electrolyte may be 2 to 10 μm.

[0017] The above solvent may include at least one of isobutyl isobutyrate, isobutyl butyrate, n-butyl butyrate, diisobutyl ketone, isoamyl butyrate, isoamyl isovalerate, amyl butyrate, hexyl acetate, 2-ethylhexyl acetate, hexyl butyrate, ethylhexanoate, hexyl propionate, hexylhexanoate, isopropylbenzene, and dimethyl dimethyl carbonate.

[0018] A method for preparing a slurry composition for a sulfide-based solid electrolyte according to another embodiment of the present invention comprises the steps of: preparing a first mixed solution by adding a sulfide-based solid electrolyte containing a Li element, a P element, and an S element to a solvent having a specific gravity of 0.8 to 3.0 and mixing; and preparing a second mixed solution by adding a binder composition to the first mixed solution and mixing; and may include a binder comprising a repeating unit derived from vinylidene fluoride, a repeating unit derived from trifluoroethylene, and a repeating unit derived from chlorotrifluoroethylene; and an ester-based solvent.

[0019] The content of the above sulfide-based solid electrolyte may be 80 to 95 weight percent based on the total slurry composition.

[0020] The above sulfide-based solid electrolyte and solvent may be mixed in a ratio of 2:1 to 1:1.

[0021] The content of the binder composition may be 5 to 20 weight percent based on the total slurry composition.

[0022] The step of preparing the first and second mixed solutions may be performed by mixing using a mechanical mixer.

[0023] The above mixer may be mixed for 1 to 5 minutes at a rotational speed of 500 to 2000 rpm.

[0024] The step of preparing the second mixed solution may be repeated 2 to 3 times.

[0025] A method for manufacturing a solid electrolyte sheet according to another embodiment of the present invention comprises: a step of preparing a sheet; a step of applying a sulfide-based solid electrolyte slurry composition onto the sheet and casting to obtain a solid electrolyte sheet; and a step of drying the obtained solid electrolyte sheet first and then vacuum drying it second; wherein the sulfide-based solid electrolyte slurry composition comprises a sulfide-based solid electrolyte containing a Li element, a P element, and an S element, a binder composition, and a solvent having a specific gravity of 0.8 to 3.0, and the binder composition comprises a binder containing repeating units derived from vinylidene fluoride, repeating units derived from trifluoroethylene, and repeating units derived from chlorotrifluoroethylene, and an ester-based solvent.

[0026] During the first drying step above, the drying temperature may be 60 to 100℃, and the drying time may be 5 to 15 minutes.

[0027] During the above secondary drying, the drying temperature may be 40 to 80℃, and the drying time may be 4 to 10 hours.

[0028] The thickness of the solid electrolyte sheet may be 40 to 170 μm.

[0029] A solid-state battery according to another embodiment of the present invention comprises: a positive electrode layer; a negative electrode layer; and a solid electrolyte sheet manufactured by the aforementioned manufacturing method disposed between the positive electrode layer and the negative electrode layer.

[0030] The present invention can improve the chemical stability of a sulfide-based solid electrolyte when preparing a sulfide-based solid electrolyte slurry composition by using a binder composition in which a PVDF-based binder with improved polarity is dissolved in an ester-based solvent.

[0031] The present invention can improve the adhesion, uniformity, and flexibility of the sheet, as well as increase the surface area, by including a sulfide-based solid electrolyte slurry composition having the aforementioned advantages when manufacturing a sulfide-based solid electrolyte sheet.

[0032] Figure 1 is an image showing the low dispersion of a PVDF-TrFE binder according to one comparative example of the present invention.

[0033] Figure 2 is an image of the result of stirring a PVDF-TrFE binder according to one comparative example of the present invention at low and high temperatures.

[0034] Figure 3 is an image showing gelation occurring when a PVDF-TrFE binder according to one comparative example of the present invention is dissolved in a solvent.

[0035] Figure 4 is an image of a solid electrolyte sheet prepared after dissolving a PVDF-TrFE-CTFE binder according to one embodiment of the present invention in various solvents.

[0036] In this specification, terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used solely to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the invention.

[0037] The technical terms used herein are for the reference of specific embodiments only and are not intended to limit the invention. The singular forms used herein include plural forms unless phrases clearly indicate otherwise. As used in the specification, the meaning of "comprising" specifies certain characteristics, areas, integers, steps, actions, elements, and / or components, and does not exclude the presence or addition of other characteristics, areas, integers, steps, actions, elements, and / or components.

[0038] When it is stated that one part is "on" or "on" another part, it may be directly on or on the other part, or another part may be involved in between. In contrast, when it is stated that one part is "directly on" another part, no other part is interposed in between.

[0039] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with relevant technical literature and the present disclosure, and are not interpreted in an ideal or highly formal sense unless otherwise defined.

[0040] Also, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

[0041] In this specification, the term “combination(s) of these” described in the Markush-type expression means one or more mixtures or combinations selected from the group consisting of the components described in the Markush-type expression, and means including any one or more selected from the group consisting of said components.

[0042] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0043] Binder composition for sulfide-based solid electrolytes

[0044] A binder composition for a sulfide-based solid electrolyte according to one embodiment of the present invention comprises: a binder comprising repeating units derived from vinylidene fluoride, repeating units derived from trifluoroethylene, and repeating units derived from chlorotrifluoroethylene; and a non-aqueous solvent. When the binder comprises repeating units derived from trifluoroethylene (TrFE), flexibility and chemical resistance may be improved compared to when a single PVDF binder is used. On the other hand, when the binder comprises only vinylidene fluoride (VDF) copolymer, problems such as reduced flexibility and reduced performance at high temperatures may occur. When chlorotrifluoroethylene (CTFE) is included in the binder, there may be an advantage in that the mechanical properties and chemical resistance of the binder are improved. Specifically, the molar mass (Mw) of the binder composition may be 400 to 600 kg / mol.

[0045] In one embodiment, the non-aqueous solvent may include at least one of an ester-based solvent, a cyclic carbonate ester-based solvent, an ether-based solvent, a nitrile-based solvent, a tertiary amine-based solvent, and a thiol-based solvent, but is not limited thereto, and any solvent capable of uniformly dissolving the binder may be used.

[0046] In one embodiment, the ester-based solvent may include at least one of isobutyl isobutyrate, isobutyl butyrate, amyl butyrate, ethyl hexanoate, hexyl acetate, hexyl propionate, isoamyl butyrate, and isoamyl isovalerate, but is not limited thereto, and any solvent that can be dissolved in a binder to improve the chemical stability of a sulfide-based solid electrolyte may be used.

[0047] In one embodiment, the content of the binder may be 3 to 15 weight percent based on the total binder composition, and specifically 8 to 10 weight percent. When the content of the binder satisfies the above range, the chemical stability of the sulfide-based solid electrolyte composition can be improved, and deterioration or performance degradation during long-term storage can be prevented. On the other hand, if the content of the binder is too low, the bonding force with the sulfide-based solid electrolyte composition weakens, which may cause problems such as a significant decrease in physical strength and durability. In addition, if the content of the binder is too high, the viscosity becomes very high, which may cause problems such as reduced processability and decreased durability of the sulfide-based solid electrolyte.

[0048] Sulfide-based solid electrolyte slurry composition

[0049] A sulfide-based solid electrolyte slurry composition according to another embodiment of the present invention comprises: a sulfide-based solid electrolyte comprising a Li element, a P element, and an S element; a binder composition; and a solvent having a specific gravity of 0.8 to 3.0; wherein the binder composition comprises a binder comprising repeating units derived from vinylidene fluoride, repeating units derived from trifluoroethylene, and repeating units derived from chlorotrifluoroethylene; and a non-aqueous solvent. The specific gravity of the solvent may specifically be 0.85 to 2.5 and more specifically 0.87 to 1.8.

[0050] In another embodiment, the non-aqueous solvent may include at least one of an ester-based solvent, a cyclic carbonate ester-based solvent, an ether-based solvent, a nitrile-based solvent, a tertiary amine-based solvent, and a thiol-based solvent, but is not limited thereto, and any solvent capable of uniformly dissolving the binder may be used.

[0051] In another embodiment, the ester-based solvent may include at least one of isobutyl isobutyrate, isobutyl butyrate, amyl butyrate, ethyl hexanoate, hexyl acetate, hexyl propionate, isoamyl butyrate, and isoamyl isovalerate, but is not limited thereto, and any solvent that can be dissolved in a binder to improve the chemical stability of a sulfide-based solid electrolyte may be used.

[0052] In another embodiment, the average particle size of the sulfide-based solid electrolyte may be 2 to 10 μm, specifically 3 to 5 μm. When the average particle size satisfies the above range, there may be advantages such as improved ionic conductivity of the sulfide-based solid electrolyte and increased contact area between the electrode and the solid electrolyte during solid electrolyte manufacturing, thereby improving interfacial stability. On the other hand, if the average particle size is too small, the ionic conductivity may decrease. Additionally, if the particle size is too large, the contact area with the electrode decreases, which may lead to interfacial instability.

[0053] In another embodiment, the solvent may comprise, but is not limited to, at least one of isobutyl isobutyrate, isobutyl butyrate, n-butyl butyrate, diisobutyl ketone, isoamyl butyrate, isoamyl isovalerate, amyl butyrate, hexyl acetate, 2-ethylhexyl acetate, hexyl butyrate, ethyl hexanoate, hexyl propionate, hexyl hexanoate, isopropyl benzene, and dimethyl dimethyl carbonate. Any solvent capable of improving the chemical stability of sulfide-based solid electrolytes can be used.

[0054] Method for preparing a sulfide-based solid electrolyte slurry composition

[0055] A method for preparing a sulfide-based solid electrolyte slurry composition according to another embodiment of the present invention comprises the steps of: preparing a first mixed solution by adding a sulfide-based solid electrolyte containing a Li element, a P element, and an S element to a solvent having a specific gravity of 0.8 to 3.0 and mixing; and preparing a second mixed solution by adding a binder composition to the first mixed solution and mixing; wherein the binder composition comprises a binder comprising repeating units derived from vinylidene fluoride, repeating units derived from trifluoroethylene, and repeating units derived from chlorotrifluoroethylene; and a non-aqueous solvent. The specific gravity of the solvent may specifically be 0.85 to 2.5 and more specifically 0.87 to 1.8.

[0056] In another embodiment, the non-aqueous solvent may include at least one of an ester-based solvent, a cyclic carbonate ester-based solvent, an ether-based solvent, a nitrile-based solvent, a tertiary amine-based solvent, and a thiol-based solvent, but is not limited thereto, and any solvent capable of uniformly dissolving the binder may be used.

[0057] In another embodiment, the ester-based solvent may include at least one of isobutyl isobutyrate, isobutyl butyrate, amyl butyrate, ethyl hexanoate, hexyl acetate, hexyl propionate, isoamyl butyrate, and isoamyl isovalerate, but is not limited thereto; any solvent that can be dissolved in a binder to improve the chemical stability of a sulfide-based solid electrolyte may be used.

[0058] In another embodiment, the content of the sulfide-based solid electrolyte may be 80 to 95 weight% based on the total slurry composition, specifically 85 to 92 weight%. If the content of the sulfide-based solid electrolyte satisfies the above range, the lifespan and stability can be improved during the manufacture of an all-solid-state battery. On the other hand, if the content of the sulfide-based solid electrolyte is too low, the ionic conductivity may decrease, and the performance of the all-solid-state battery may decrease. In addition, if the content of the sulfide-based solid electrolyte is too high, the mechanical strength of the sulfide-based solid electrolyte slurry may decrease, which may cause cracks or defects during the manufacturing process. The sulfide-based solid electrolyte may include one or more selected from Li2S-P2S5-LiX (where X is a halogen element), Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-GeS2, and Li2S-SiS2-Li3PO4.

[0059] In another embodiment, the sulfide-based solid electrolyte and the solvent can be mixed in a ratio of 2:1 to 1:1, specifically in a ratio of 1.7:1 to 1.5:1. When the mixing ratio of the sulfide-based solid electrolyte and the solvent satisfies the above range, the performance of the electrolyte can be optimized through uniform mixing between the sulfide-based solid electrolyte and the solvent. On the other hand, if the mixing ratio of the sulfide-based solid electrolyte and the solvent deviates from the above range, the balance between the ionic conductivity of the sulfide-based solid electrolyte and the fluidity of the solvent is disrupted, which may result in a problem of reduced chemical stability.

[0060] In another embodiment, the content of the binder composition may be 5 to 20 weight percent based on the total slurry composition, specifically 10 to 15 weight percent. When the content of the binder composition satisfies the above range, the binder is uniformly dispersed within the sulfide-based solid electrolyte slurry composition, which improves inter-particle bonding strength and may have the advantage of excellent physical properties. On the other hand, if the content of the binder composition is too low, the inter-particle bonding strength may be weakened. In addition, if the content of the binder composition is too high, excessive aggregation occurs, resulting in uneven dispersion, and the viscosity becomes too high, which may reduce workability.

[0061] In another embodiment, the step of preparing the first and second mixed solutions may be performed using a mechanical mixer, but is not limited thereto, and any device capable of uniformly mixing the first and second mixed solutions may be used.

[0062] In another embodiment, the mixer can mix for 1 to 5 minutes at a rotational speed of 500 to 2000 rpm, and specifically, mix for 2 to 4 minutes at a rotational speed of 800 to 1700 rpm. When the rotational speed and mixing time satisfy the above ranges, the material is uniformly dispersed, which can improve the conductivity and stability of the solid electrolyte. On the other hand, if the rotational speed is too low and the mixing time is too short, the material is mixed unevenly, which may reduce the conductivity of the solid electrolyte. In addition, if the rotational speed is too fast or the mixing time is too long, excessive heat is generated, which may cause thermal decomposition of the sulfide-based solid electrolyte and reduce its stability, and the particles may be damaged, leading to a deterioration in physical properties.

[0063] In another embodiment, the step of preparing the second mixed solution may be repeated two to three times. When the second mixed solution is prepared repeatedly, the particles are uniformly dispersed, which can improve the ionic conductivity of the solid electrolyte.

[0064] Solid electrolyte sheet and manufacturing method

[0065] A solid electrolyte sheet according to another embodiment of the present invention comprises the steps of: preparing a sheet; applying a sulfide-based solid electrolyte slurry composition onto the sheet and casting to obtain a solid electrolyte sheet; and drying the obtained solid electrolyte sheet first and then vacuum drying it second; wherein the sulfide-based solid electrolyte slurry composition comprises a sulfide-based solid electrolyte comprising a Li element, a P element, and an S element, a binder composition, and a solvent having a specific gravity of 0.8 to 3.0, and the binder composition comprises a binder comprising repeating units derived from vinylidene fluoride, repeating units derived from trifluoroethylene, and repeating units derived from chlorotrifluoroethylene, and a non-aqueous solvent. The specific gravity of the solvent may specifically be 0.85 to 2.5 and more specifically 0.87 to 1.8.

[0066] In another embodiment, the non-aqueous solvent may include at least one of an ester-based solvent, a cyclic carbonate ester-based solvent, an ether-based solvent, a nitrile-based solvent, a tertiary amine-based solvent, and a thiol-based solvent, but is not limited thereto, and any solvent capable of uniformly dissolving the binder may be used.

[0067] In another embodiment, the ester-based solvent may include at least one of isobutyl isobutyrate, isobutyl butyrate, amyl butyrate, ethyl hexanoate, hexyl acetate, hexyl propionate, isoamyl butyrate, and isoamyl isovalerate, but is not limited thereto; any solvent that can be dissolved in a binder to improve the chemical stability of a sulfide-based solid electrolyte may be used.

[0068] In another embodiment, the drying temperature during the first drying may be 60 to 100°C and the drying time may be 5 to 15 minutes, and specifically, the drying temperature may be 75 to 85°C and the drying time may be 7 to 10 minutes.

[0069] In another embodiment, the drying temperature during the second drying may be 40 to 80°C and the drying time may be 4 to 10 hours, and specifically, the drying temperature may be 55 to 65°C and the drying time may be 5 to 7 hours.

[0070] If the above-mentioned first drying temperature, second drying temperature, first drying time, and second drying time satisfy the above ranges, there may be an advantage in that the stability of the solid electrolyte is increased by effectively removing the solvent within the sulfide-based solid electrolyte sheet. On the other hand, if the above-mentioned first drying temperature and second drying temperature are too low or the first drying time and second drying time are too short, the solvent is not sufficiently removed, which may lower the conductivity of the solid electrolyte and cause performance degradation during the manufacture of an all-solid-state battery. In addition, if the above-mentioned first drying temperature and second drying temperature are too high or the first drying time and second drying time are too long, the sheet may be exposed to excessive heat, causing structural damage, and the physical properties of the solid electrolyte may change, leading to performance degradation.

[0071] In another embodiment, the thickness of the solid electrolyte sheet may be 40 to 170 μm, specifically 60 to 167 μm. When the thickness of the solid electrolyte sheet satisfies the above range, the energy density of the solid electrolyte sheet is optimized, which can maximize capacity during the manufacture of an all-solid-state battery and reduce the risk of electrical short circuits, thereby improving the safety of the all-solid-state battery. On the other hand, if the thickness of the solid electrolyte sheet is too thin, it may be easily damaged by external pressure or impact, and the possibility of an electrical short circuit between the negative and positive electrodes may increase, thereby reducing the safety of the all-solid-state battery. Additionally, if the thickness of the solid electrolyte sheet is too thick, the ion movement path becomes longer, which may lead to reduced conductivity and a decrease in the charging and discharging efficiency of the all-solid-state battery.

[0072] A solid electrolyte sheet according to another embodiment of the present invention is manufactured by the solid electrolyte sheet manufacturing method described above.

[0073] All-solid-state battery

[0074] A solid-state battery according to another embodiment of the present invention comprises: a positive electrode layer; a negative electrode layer; and the aforementioned solid electrolyte sheet disposed between the positive electrode layer and the negative electrode layer.

[0075] (Bipolar layer)

[0076] More specifically, the anode layer may include an anode current collector and an anode active material layer disposed on the anode current collector.

[0077] The above-mentioned positive active material layer may further include, for example, a positive active material and, optionally, a solid electrolyte. The solid electrolyte included in the positive active material layer may be the same as or different from the solid electrolyte according to one embodiment of the present invention, and may be the same as or different from the solid electrolyte included in the solid electrolyte layer.

[0078] The cathode active material is a material capable of reversibly absorbing and desorbing lithium ions. The cathode active material may be, for example, 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, but is not necessarily limited to these; any material used as a cathode active material in the relevant technical field is acceptable. The cathode active material may be a single material or a mixture of two or more materials.

[0079] The above lithium transition metal oxide is, for example, Li a A 1-b B b D2(wherein 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B bO 2-c D c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B b O 4-c D c (In the above equation, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B c D α (In the above equation, 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 (In the above equation, 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 F2(wherein 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 (In the above equation, 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 O 2-α F α (In the above equation, 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 O 2-αF2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d GeO2(wherein the above formula, 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(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4(wherein 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-f)Fe2(PO4)3(0 ≤ f ≤ 2); a compound represented by any one of the chemical formulas of LiFePO4. In such a compound, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. A compound having a coating layer added to the surface of such a compound may also be used, and a mixture of the compound described above and a compound having a coating layer added may also be used. The coating layer applied to the surface of such compounds comprises, for example, a coating element compound of an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of a coating element. The compounds forming this coating layer are amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. 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 coating method is, for example, spray coating or immersion. Since specific coating methods are well understood by those skilled in the art, a detailed explanation will be omitted.

[0080] The positive active material layer may include, for example, a binder. The binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to these, and any binder used in the relevant technical field is acceptable.

[0081] The positive active material layer may include, for example, a conductive material. The conductive material may include, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, etc., but is not limited to these, and any material used as a conductive material in the relevant technical field is acceptable.

[0082] The positive active material layer may further include additives such as fillers, coating agents, dispersants, and ion-conducting aids in addition to the positive active material, solid electrolyte, binder, and conductive material described above, for example.

[0083] As fillers, coating agents, dispersants, ion-conducting auxiliary agents, etc. that may be included in the positive electrode active material layer, known materials generally used in electrodes of all-solid-state secondary batteries can be used.

[0084] The positive current collector may be a plate or foil made of, 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 alloys thereof. The thickness of the positive current collector may be, for example, 1 µm to 100 µm, 1 µm to 50 µm, 5 µm to 25 µm, or 10 µm to 20 µm.

[0085] (Cathode layer)

[0086] More specifically, the above cathode layer may include a cathode current collector and a cathode active material layer disposed on the cathode current collector.

[0087] The above-mentioned cathode active material layer may include, for example, a cathode active material and a binder, and may optionally further include a solid electrolyte as needed.

[0088] The above-mentioned negative electrode active material may include, for example, a carbon-based negative electrode active material, a metal / metallic negative electrode active material, or a combination thereof.

[0089] The carbon-based cathode active material may be amorphous carbon, crystalline carbon, or a mixture or composite thereof. The amorphous carbon may be, for example, carbon black (CB), acetylene black (AB), furnace black (FB), Kettjen black (KB), graphene, etc., but is not necessarily limited to these, and any material classified as amorphous carbon in the relevant technical field is acceptable. Amorphous carbon is carbon that does not have crystallinity or has very low crystallinity, and is distinguished from crystalline carbon or graphite-based carbon. The crystalline carbon may be, for example, natural graphite, artificial graphite, or a combination thereof.

[0090] The metal / metallic anode active material comprises one or more selected from the group consisting of lithium (Li), gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), but is not necessarily limited to these, and any metal anode active material or metallic anode active material that forms an alloy or compound with lithium in the relevant technical field is acceptable.

[0091] The binder included in the negative electrode active material layer may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited to these, and any binder used in the relevant technical field is acceptable. The binder may be composed of a single binder or a plurality of different binders.

[0092] The cathode active material layer is stabilized on the cathode current collector by including a binder. In addition, cracking of the cathode active material layer is suppressed despite volume changes and / or relative positional changes of the cathode active material layer during the charging and discharging process.

[0093] The negative electrode active material layer may further include additives used in conventional all-solid-state batteries, such as fillers, coating agents, dispersants, ion conductivity aids, etc.

[0094] The all-solid-state battery may further include a second negative electrode active material layer disposed between the negative electrode current collector and the negative electrode active material layer upon charging. The second negative electrode active material layer may be deposited between the negative electrode current collector and the negative electrode current collector during the charging process, or may be further disposed on the negative electrode active material layer during electrode assembly. This second negative electrode active material layer may be a metal layer comprising lithium or a lithium alloy. The lithium alloy may be, for example, 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, but is not limited thereto; any alloy used as a lithium alloy in the relevant technical field is acceptable. The second negative electrode active material layer may be composed of one of these alloys and / or lithium, or may be composed of various types of alloys and / or lithium.

[0095] The negative electrode current collector may be composed of, for example, a material that does not react with lithium, that is, does not form either an alloy or a compound. The negative electrode current collector may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not necessarily limited to these; any material used as an electrode current collector in the relevant technical field is acceptable. The negative electrode current collector may be composed of one of the metals described above, or may be composed of an alloy or coating material of two or more metals. The negative electrode current collector may be, for example, in the form of a plate or a foil.

[0096] When the above-mentioned cathode active material layer includes a solid electrolyte, the solid electrolyte included in the above-mentioned cathode active material layer may be the same as or different from the solid electrolyte according to one embodiment of the present invention, and may be the same as or different from the solid electrolyte included in the solid electrolyte layer.

[0097] (Solid electrolyte layer)

[0098] The above solid electrolyte layer can be manufactured by mixing and drying the aforementioned solid electrolyte and binder, or by rolling the aforementioned solid electrolyte powder into a certain shape under a pressure of 1 ton to 10 ton.

[0099] At this time, the solid electrolyte may be in the form of a powder or a molded article. The solid electrolyte in the form of a molded article may be, for example, in the form of pellets, sheets, thin films, etc., but is not necessarily limited to these and may have various forms depending on the application.

[0100] The above solid electrolyte layer may, if necessary, further include a solid electrolyte such as a conventional sulfide-based solid electrolyte and / or an oxide-based solid electrolyte in addition to the aforementioned solid electrolyte.

[0101] The above binder is, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polyvinyl alcohol, etc., but is not limited to these, and any binder used in the relevant technical field is acceptable. The binder of the solid electrolyte layer may be of the same type as or different from the binders of the anode layer and the cathode layer.

[0102] Another embodiment of the present invention provides an electric vehicle comprising the all-solid-state battery.

[0103] The embodiments of the present invention will be described in more detail below through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited by the following examples.

[0104] Example 1

[0105] 1-1. Binder Composition

[0106] A binder composition was prepared by dissolving a PVDF-TrFE-CTFE binder in the solvent isobutyl isobutyrate (IBIB) at 10 wt%.

[0107] 1-2. Sulfide-based solid electrolyte slurry

[0108] A sulfide-based solid electrolyte slurry composition was prepared by introducing 90 wt% of a Li6PS5Cl sulfide-based solid electrolyte with a particle size of 3 μm, 3.5 ml of solvent (solvent name), and 10 wt% of the binder composition prepared in Example 1-1 into a container in a glove box under an argon (Ar) atmosphere and mechanically mixing with zirconia balls (diameter: 5 mm) at room temperature. A Thinky Mixer was used for mechanical mixing, and the sulfide-based solid electrolyte slurry was prepared by mixing for 1 to 4 minutes at a rotational speed of 1000 to 2000 rpm.

[0109] 1-3. Fabrication of Sulfide-Based Solid Electrolyte Sheets

[0110] The sulfide-based solid electrolyte slurry prepared in Examples 1-2 was applied to a PET release film (thickness: 85 μm) and cast with a manual doctor blade to a solid electrolyte thickness of 100 μm. Subsequently, it was first dried at 80°C for 10 minutes under vacuum, and after obtaining the sheet, it was secondarily vacuum dried at 60°C for 6 hours to completely remove the solvent, thereby producing a sulfide-based solid electrolyte sheet.

[0111] 1-4. Manufacturing of All-Solid State Batteries

[0112] A solid electrolyte sheet prepared in Examples 1-3 was loaded into a jig for evaluating all-solid-state batteries, and after applying pressure of 300 MPa or more to achieve a thickness of approximately 185 μm, a positive electrode plate was placed on one side and a secondary pressure was applied to fabricate the positive electrode. Subsequently, a Li-In alloy was placed on the other side and an appropriate pressure was applied to fabricate an all-solid-state battery for evaluation.

[0113] Examples 2 to 14

[0114] Binder composition

[0115] A binder composition was prepared in the same manner as Example 1-1 based on the type of binder, solvent, and binder content described in Examples 2 to 14 of Table 1 below.

[0116] Sulfide-based solid electrolyte slurry

[0117] A sulfide-based solid electrolyte slurry was prepared in the same manner as in Examples 1-2, except that a binder composition prepared based on the type of binder, solvent, and binder content described in Examples 2 to 14 of Table 1 below was used.

[0118] Sulfide-based solid electrolyte sheet

[0119] A sulfide-based solid electrolyte sheet was prepared in the same manner as in Examples 1-3, except that a sulfide-based solid electrolyte slurry prepared based on the contents described in Examples 2 to 14 of Table 1 below was used.

[0120] All-solid-state battery

[0121] All-solid-state batteries were manufactured using the same method as in Examples 1-4, except that sulfide-based solid electrolyte sheets manufactured based on the contents described in Examples 2 to 14 of Table 1 below were used.

[0122] Comparative Example 1

[0123] 1-1. Binder Composition

[0124] A binder composition was prepared by dissolving an NBR binder in the solvent isobutyl isobutyrate (IBIB) at 10% by weight.

[0125] 1-2. Sulfide-based solid electrolyte slurry

[0126] A sulfide-based solid electrolyte slurry was prepared in the same manner as in Example 1-2, except that the binder composition prepared in Comparative Example 1-1 was used.

[0127] 1-3. Fabrication of Sulfide-Based Solid Electrolyte Sheets

[0128] A sulfide-based solid electrolyte sheet was prepared in the same manner as in Example 1-3, except that the sulfide-based solid electrolyte slurry prepared in Comparative Example 1-2 was used.

[0129] 1-4. Manufacturing of All-Solid State Batteries

[0130] An all-solid-state battery was manufactured in the same manner as in Example 1-4, except that the sulfide-based solid electrolyte sheet prepared in Comparative Example 1-3 was used.

[0131] Comparative Examples 2 to 6

[0132] Binder composition

[0133] A binder composition was prepared in the same manner as Example 1-1 based on the type of binder, solvent, and binder content described in Comparative Examples 2 to 6 of Table 1 below.

[0134] Sulfide-based solid electrolyte slurry

[0135] A sulfide-based solid electrolyte slurry was prepared in the same way as in Examples 1-2, except that a binder composition prepared based on the binder type, solvent, and binder content described in Comparative Examples 2 to 6 of Table 1 below was used.

[0136] Sulfide-based solid electrolyte sheet

[0137] A sulfide-based solid electrolyte sheet was prepared in the same manner as in Examples 1-3, except that a sulfide-based solid electrolyte slurry prepared based on the contents described in Comparative Examples 2 to 6 of Table 1 below was used.

[0138] All-solid-state battery

[0139] All-solid-state batteries were manufactured using the same method as Examples 1-4, except that sulfide-based solid electrolyte sheets manufactured based on the contents described in Comparative Examples 2 to 6 of Table 1 below were used.

[0140] Experimental Example

[0141] The ionic conductivity, electronic conductivity, and potential stability of sulfide-based solid electrolyte sheets according to one embodiment and a comparative example of the present invention were measured. Specifically, the solid electrolyte sheets prepared in one embodiment and a comparative example of the present invention and two stainless steel pieces were assembled into a pressure cell. AC impedance measurements were performed at 1x10 6 The impedance value was measured while applying an alternating potential of 10 mV in the frequency range of Hz to 1 mHZ, and the ionic conductivity value was obtained based on Equation 1 below.

[0142] [Equation 1]

[0143] Ionic conductivity (σ) = L / (R x S)

[0144] In the above Equation 1, R is the resistance of the solid electrolyte sheet, L is the thickness of the solid electrolyte sheet, and S is the area of ​​the solid electrolyte sheet.

[0145] In addition, electronic conductivity was measured using chronoamperometry by applying a potential of 0.1 V for 20 minutes. The potential stability of the solid electrolyte sheet was measured in the range of 0 to 6 V using linear sweep voltammetry, and the current was 0.1 mA·cm² -2 When it occurred below, it was considered electrochemically stable, and the results are shown in Table 1.

[0146] Binder Binder content (wt%) Solvent thickness (μm) Ionic conductivity (mS / cm) Electronic conductivity (S / cm) Potential stability (4.25 V (vs. ref)) Comparative Example 1 NBR10 Isobutyl Isobutyrate (IBIB) 800.123.75 X 10 -8 Stability Comparison Example 2 PVDF-TrFE10 IsobutylButyrate (IBB) 128 0.2 1 1.67 X 10 -10 Stability Comparison Example 3 PVDF-TrFE10 Isobutyl Isobutyrate (IBIB) 153 0.32 2.88 X 10 -10 Stability Comparison Example 4 PVDF-TrFE 10 Amyl Butyrate (AB) 160 0.05 1.41 X 10 -10 Stability Comparison Example 5 PVDF-TrFE10 Ethyl hexanoate(EH)85 0.14 1.07 X 10 -9 Stability Comparison Example 6 PVDF-TrFE 10 Hexyl acetate (HA) 10 0.05 1.05 X 10 -9 Stability Comparison Example 7 PVDF-TrFE10 Hexyl propionate (HP) 138 0.24 3.81 X 10 -10 Stabilization Example 1 PVDF-TrFE-CTFE 10 Isobutyl Isobutyrate (IBIB) 1100 0.87 6.81 X 10 -9Stabilization Example 2 PVDF-TrFE-CTFE 10 IsobutylButyrate (IBB) 620.732.56 X 10 -8 Stabilization Example 3 PVDF-TrFE-CTFE 10 IsoamylButyrate (IAB) 17 10.48 9.86 X 10 -10 Stabilization Example 4 PVDF-TrFE-CTFE 10 Isoamyl Isovalerate (IAIV) 630.544.39 X 10 -8 Stable Example 5PVDF-TrFE-CTFE10Amyl Butyrate(AB)790.604.36 -8 Stabilization Example 6 PVDF-TrFE-CTFE 10 Ethyl hexanoate(EH) 560.49 1.19 X 10 -8 Stabilization Example 7 PVDF-TrFE-CTFE 10 Hexyl acetate (HA) 167 0.77 6.78 X 10 -10 Stabilization Example 8 PVDF-TrFE-CTFE 10 Hexyl propionate (HP) 880.841.18 X 10 -9 Stabilization Example 9 PVDF-TrFE-CTFE5 Isobutyl Isobutyrate (IBIB)831.007.43 X 10 -9 Stable Example 10PVDF-TrFE-CTFE5IsobutylButyrate(IBB)641.113.46 -9 Stabilization Example 11 PVDF-TrFE-CTFE5 IsoamylButyrate (IAB) 104 1.00 6.44 X 10 -9 Stabilization Example 12 PVDF-TrFE-CTFE5 Ethyl hexanoate(EH)2500 0.43 3.04 X 10 -9 Stabilization Example 13 PVDF-TrFE-CTFE5 Hexyl acetate (HA) 1830.266.76 X 10 -10 Stabilization Example 14 PVDF-TrFE-CTFE5 Hexyl Propionate (HP) 1200.341.6 X 10 -9 stability

[0147] Referring to Table 1, it can be confirmed that the binders of Examples 1 to 14, which contain repeating units derived from vinylidene fluoride (VDF), trifluoroethylene (TrFE), and chlorotrifluoroethylene (CTFE), exhibit superior ionic conductivity compared to Comparative Examples 1 to 6. Furthermore, although Example 1 and Comparative Example 1 both use Isobutyl Isobutyrate (IBIB) as the binder composition solvent, it can be confirmed that the ionic conductivity is excellent despite the fact that the thickness of the solid electrolyte sheet in Example 1 is thicker than that of Comparative Example 1. Through this, it can be seen that using a PVDF-TrFE-CTFE-based binder improves ionic conductivity even though the resistance increases due to the thickness of the solid electrolyte sheet. It can be seen that the binders of Comparative Examples 2 to 6, which contain repeating units derived from vinylidene fluoride (VDF) and trifluoroethylene (TrFE), have low dispersion and thus reduced ionic conductivity, as shown in the image of the sheet dispersion in Fig. 1. Additionally, referring to Fig. 2, the binders of Comparative Examples 2 to 6 are stirred at high temperatures (120°C) but are difficult to stir at low temperatures (60°C). Since stirring under high-temperature conditions is not suitable for the large-area sheet process, a problem may arise where mass production is impossible. Furthermore, it can be seen that the binders of Comparative Examples 2 to 6 are not suitable for mass production because gelation occurs when dissolved in a solvent at room temperature, as shown in Fig. 3.On the other hand, referring to FIG. 4, the binder composition in which PVDF-TrFE-CTFE binder is dissolved at 10 wt% in a solvent of Isobutyl Isobutyrate (IBIB), Isobutyl Butyrate (IBB), Isoamyl Butyrate (IAB), Ethyl hexanoate (EH), or Hexyl Acetate (HA), as in Examples 1 to 3, 6, and 7, forms a slurry with excellent dispersibility as shown in FIG. 4, which enables smooth casting during sheet manufacturing and confirms that a uniform film is obtained after drying.

[0148] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention.

[0149] Therefore, the substantive scope of the present invention shall be defined by the appended claims and their equivalents.

Claims

1. A binder comprising repeating units derived from vinylidene fluoride, repeating units derived from trifluoroethylene, and repeating units derived from chlorotrifluoroethylene; and A binder composition for sulfide-based solid electrolytes comprising a non-aqueous solvent.

2. In Paragraph 1, A binder composition for a sulfide-based solid electrolyte, wherein the above-mentioned non-aqueous solvent comprises at least one of an ester-based solvent, a cyclic carbonate ester-based solvent, an ether-based solvent, a nitrile-based solvent, a tertiary amine-based solvent, and a thiol-based solvent.

3. In Paragraph 2, The above ester-based solvent is a binder composition for a sulfide-based solid electrolyte comprising at least one of isobutyl isobutyrate, isobutyl butyrate, amyl butyrate, ethyl hexanoate, hexyl acetate, hexyl propionic acid, isoamyl butyrate, and isoamyl isovalerate.

4. In Paragraph 1, A binder composition for a sulfide-based solid electrolyte, wherein the content of the binder is 3 to 15 weight percent based on the total binder composition.

5. Sulfide-based solid electrolyte containing Li, P, and S elements; Binder composition; and A solvent having a specific gravity of 0.8 to 3.0; comprising, A slurry composition for a sulfide-based solid electrolyte, wherein the binder composition comprises: a binder comprising repeating units derived from vinylidene fluoride, repeating units derived from trifluoroethylene, and repeating units derived from chlorotrifluoroethylene; and a non-aqueous solvent.

6. In Paragraph 5, A slurry composition for a sulfide-based solid electrolyte, wherein the average particle size of the sulfide-based solid electrolyte is 2 to 10 μm.

7. In Paragraph 5, The above solvent is a slurry composition for a sulfide-based solid electrolyte comprising at least one of isobutyl isobutyrate, isobutyl butyrate, n-butyl butyrate, diisobutyl ketone, isoamyl butyrate, isoamyl isovalerate, amyl butyrate, hexyl acetate, 2-ethylhexyl acetate, hexyl butyrate, ethylhexanoate, hexyl propionate, hexylhexanoate, isopropylbenzene, and dimethyl dimethyl carbonate.

8. Step to prepare the sheet; A step of obtaining a solid electrolyte sheet by applying a sulfide-based solid electrolyte slurry composition onto the sheet and casting it; and The method comprises the step of performing a second vacuum drying of the obtained solid electrolyte sheet after a first drying step, and A method for manufacturing a solid electrolyte sheet, wherein the sulfide-based solid electrolyte slurry composition comprises a sulfide-based solid electrolyte containing Li, P, and S elements, a binder composition, and a solvent having a specific gravity of 0.8 to 3.0, and the binder composition comprises a binder containing repeating units derived from vinylidene fluoride, repeating units derived from trifluoroethylene, and repeating units derived from chlorotrifluoroethylene, and a non-aqueous solvent.

9. In Paragraph 8, A method for manufacturing a solid electrolyte sheet, wherein the drying temperature during the first drying step is 60 to 100℃ and the drying time is 5 to 15 minutes.

10. In Paragraph 8, A method for manufacturing a solid electrolyte sheet, wherein the drying temperature during the second drying is 40 to 80℃ and the drying time is 4 to 10 hours.

11. In Paragraph 8, A method for manufacturing a solid electrolyte sheet, wherein the thickness of the solid electrolyte sheet is 40 to 170 μm.

12. A solid electrolyte sheet manufactured according to any one of claims 8 to 11.

Images