A sulfide base all-solid-state battery comprising cathode active material coated with lithium niobite precursor and method of manufacturing the same

Abstract

The present invention relates to a sulfide-based all-solid-state battery comprising a positive electrode active material coated with a lithium niobate precursor manufactured by a polyol process that increases the capacity of the sulfide-based all-solid-state battery, improves safety, and lowers production costs, and a method for manufacturing the same.

Description

Technology Field

[0001] The present invention relates to a sulfide-based all-solid-state battery comprising a positive electrode active material coated with a lithium niobate precursor and a method for manufacturing the same. Specifically, it relates to a sulfide-based all-solid-state battery comprising a positive electrode active material coated with a lithium niobate precursor produced by a polyol process and a method for manufacturing the same. Background Technology

[0002] Lithium-ion secondary batteries have the advantages of high energy density, low self-discharge rate, and long lifespan compared to nickel-manganese or nickel-cadmium batteries, but they are pointed out as disadvantages such as safety issues regarding overheating and low power output.

[0003] All-solid-state batteries are being proposed as an alternative to overcome the problems of lithium-ion secondary batteries. An all-solid-state battery may be structured such that an electrolyte layer containing a solid electrolyte, a positive electrode layer containing a solid electrolyte, and a negative electrode layer containing a solid electrolyte are formed on both sides of the electrolyte layer, and a current collector is coupled to each electrode.

[0004] All-solid-state batteries can be classified into oxide-based, polymer-based, and sulfide-based types depending on the raw materials of the solid electrolyte. Sulfide-based all-solid-state batteries exhibit superior lithium-ion conductivity compared to other battery types. Nevertheless, they have not yet overcome the disadvantages of reduced lifespan and output resulting from lower ion conductivity and higher electric resistance between the anode, cathode, and solid electrolyte compared to conventional batteries using liquid electrolytes.

[0005] The positive electrode active material and the sulfide-based solid electrolyte react with each other at the interface to form a resistive material that hinders the operation of the all-solid-state battery. This resistive material causes problems such as a decrease in the initial capacity and reduced efficiency of the all-solid-state battery.

[0006] All-solid-state batteries according to the prior art improve the performance of the all-solid-state battery by coating the positive electrode active material with lithium niobate to reduce reactivity with the sulfide-based solid electrolyte. Patent Document 1 coats the positive electrode active material with lithium niobate using an organic solvent. There is a problem in that the solid electrolyte must be used after completely evaporating the residual organic solvent so as not to react with the sulfide-based solid electrolyte. In addition, there is a problem in that the production cost is high and the process is lengthy because lithium ethoxide and niobium ethoxide are used as starting materials to form lithium niobate.

[0007] When coating a positive electrode active material with lithium niobate, if the coating is performed in a dry manner, there is a disadvantage that the lithium niobate cannot uniformly coat the positive electrode active material, which makes it difficult to manufacture a sulfide-based all-solid-state battery at a low cost and with high performance. Prior art literature

[0008] Japanese Registered Patent Publication No. 4982866 The problem to be solved

[0009] The present invention aims to solve the above-mentioned problems by providing a sulfide-based all-solid-state battery in a stable and economical manner by coating a positive electrode active material using a lithium niobate precursor manufactured by a polyol process. means of solving the problem

[0010] To solve the above-mentioned problems, the present invention provides a positive electrode active material coated with a lithium niobate precursor manufactured by a polyol process. Furthermore, the invention provides a sulfide-based all-solid-state battery comprising the coated positive electrode active material.

[0011] The above coating may be a dry mixing of the positive electrode active material and the lithium niobate precursor without a separate solvent.

[0012] The above coating may be heat-treated by mixing the above positive active material and the lithium niobate precursor dry, raising the temperature by 5°C per minute to reach a target temperature, and then cooling it naturally.

[0013] The above lithium niobate precursor may include lithium niobate and a chelating agent.

[0014] The above chelating agent may be one or more of the group including citric acid, PVP, carboxylic acid, and weak acid containing a nitrogen element.

[0015] The above lithium niobate precursor can be coated on the above positive active material to a thickness of 1 nm to 100 nm or less.

[0016] In addition, the above-mentioned positive electrode active material may be lithium cobalt oxide. As the above-mentioned lithium cobalt oxide is the positive electrode active material according to one embodiment of the present invention, a positive electrode active material capable of being utilized in a lithium-ion secondary battery or an all-solid-state battery may be used.

[0017] The present invention may include a method for coating a positive electrode active material, comprising: S1) mixing a polyol and a chelating agent to form a polyol precursor; S2) mixing lithium hydroxide and ammonium niobate oxalate hydrate with the polyol precursor to form a positive electrode active material coating material; and S3) coating a positive electrode active material with the positive electrode active material coating material.

[0018] Step S3) above may involve mixing the positive active material coating material and the positive active material, and then heat-treating the mixture at 450°C or higher for 2 hours.

[0019] In addition, the heat treatment at 450°C or higher for 2 hours may be performed by raising the temperature by 5°C per minute to reach the target temperature, and then cooling it naturally.

[0020] In addition, the above S2) step can be carried out dry.

[0021] The present invention may select and combine one or more non-conflicting configurations among the above configurations. Effects of the invention

[0022] The present invention provides a sulfide-based all-solid-state battery comprising a coated electrode active material having low reactivity between the sulfide-based solid electrolyte and the cathode active material and improved safety.

[0023] A sulfide-based all-solid-state battery with improved performance can be provided by uniformly coating the above-mentioned positive electrode active material with lithium niobate, thereby reducing the reactivity between the sulfide-based solid electrolyte and the positive electrode active material.

[0024] In addition, by performing the coating method, which was previously performed in a wet manner, in a dry manner, a manufacturing method that is simple and economical is provided. Brief explanation of the drawing

[0025] FIG. 1 is a flowchart relating to a method of coating a positive electrode active material with a lithium niobate precursor according to the present invention. Figure 2 is the chemical formula of a lithium niobate precursor prepared by a polyol process. Figure 3 is a scanning electron microscope (SEM) image of lithium niobate produced by the polyol process according to the present invention. Figure 4 is a scanning electron microscope (SEM) image of a positive electrode active material coated with lithium niobate prepared by a polyol process according to the present invention. Figure 5 is a transmission electron microscope (TEM) image of a lithium niobate precursor according to the present invention. Figure 6 is a transmission electron microscope (TEM) image of a positive electrode active material coated with a lithium niobate precursor according to the present invention. Figure 7 is a graph comparing the specific capacity according to voltage of a sulfide-based all-solid-state battery according to the present invention and a sulfide-based all-solid-state battery manufactured with an uncoated positive electrode active material. Figure 8 is a graph comparing the capacity retention rates of a sulfide-based all-solid-state battery according to the present invention and a sulfide-based all-solid-state battery manufactured with an uncoated positive electrode active material. Figure 9 is a graph comparing the impedance values ​​of a sulfide-based all-solid-state battery according to the present invention and a sulfide-based all-solid-state battery manufactured with an uncoated positive electrode active material. Specific details for implementing the invention

[0026] Embodiments that enable a person skilled in the art to easily practice the present invention are described in detail below with reference to the attached drawings. However, in describing the operating principles of preferred embodiments of the present invention in detail, if it is determined that a specific description of related known functions or configurations may unnecessarily obscure the essence of the present invention, such detailed description is omitted.

[0027] In addition, the same reference numerals are used for parts having similar functions and operations throughout the drawings. Throughout the specification, when a part is described as being connected to another part, this includes not only cases where they are directly connected, but also cases where they are indirectly connected with other elements in between. Furthermore, unless specifically stated otherwise, the inclusion of a certain component does not exclude other components but implies that additional components may be included.

[0028] Furthermore, descriptions that specify components by limiting or adding them may be applied to all inventions unless otherwise specifically limited, and are not limited to a particular invention.

[0029] In addition, throughout the description of the invention and claims of this application, items indicated in the singular include cases where they are plural unless otherwise noted.

[0030] In addition, throughout the description of the invention and the claims of the present invention, "or" includes "and" unless otherwise noted. Therefore, "comprising A or B" means all three of the above cases: including A, including B, or including both A and B.

[0031] In addition, all numerical ranges include the values ​​at both ends and all intermediate values ​​in between, unless explicitly stated to be excluded.

[0032] The present invention is described in more detail below.

[0033] The present invention may include a positive electrode active material coated with a lithium niobate precursor manufactured by a polyol process.

[0034] FIG. 1 is a flowchart relating to a method of coating a positive electrode active material with a lithium niobate precursor according to the present invention.

[0035] As can be seen in FIG. 1, the positive electrode active material according to the present invention is mixed dry with a lithium niobate precursor without a separate solvent. The mixing method is not specifically limited in the present invention, and known methods may be used. It may be carried out through a conventional mechano-chemical reaction. In addition, conventional stirrers, mixers, planetary ball mills, mortar mixers, etc., may be used for mixing. When using a planetary ball mill, the lithium niobate precursor and the positive electrode active material can be mixed at 50 to 500 revolutions / min, 0.1 to 10 hours, and 1 to 100 kWh / 1 kg.

[0036] There is no limit to the moisture content of each particle when dry, but it is preferable to dry each particle at 120°C for 6 hours.

[0037] At this time, the weight ratio of the lithium niobate precursor to the positive electrode active material is sufficient if the lithium niobate precursor is in an amount sufficient to coat the positive electrode active material. For example, the weight ratio of the lithium niobate precursor to the positive electrode active material may be 1 to 10 : 90 to 99. Preferably, it may be 2 to 5 : 98 to 95.

[0038] After dry mixing the lithium niobate precursor and the positive electrode active material, the mixture can be heat-treated at 400°C or higher. Due to the heat treatment described above, the bonding force between the lithium niobate precursor and the positive electrode active material increases, causing the coated lithium niobate precursor to adhere closely to the positive electrode active material.

[0039] The heat treatment described above may be a method of raising the temperature by 5°C per minute to reach the target temperature and then allowing it to cool naturally. At this time, it is desirable that the target temperature not exceed 500°C. If heat of 500°C or higher is applied, the cobalt in the lithium cobalt oxide used as the positive electrode active material may diffuse into the lithium niobate precursor due to the high temperature and react with the sulfide-based solid electrolyte.

[0040] At this time, the lithium niobate precursor and the positive electrode active material that have reached the target temperature can be naturally cooled to 25°C while left as they are for 1 to 3 hours.

[0041] This heat treatment is carried out as a single process to ensure that the lithium niobate precursor and the positive electrode active material bond evenly and uniformly, and to prevent any voids from forming between the lithium niobate precursor and the positive electrode active material.

[0042] After the above heat treatment, the lithium niobate precursor can be coated onto the positive electrode active material. The lithium niobate precursor can be coated onto the positive electrode active material to a thickness of 1 nm to 100 nm or less.

[0043] The polyol used in the above polyol process is a general term for alcohols containing two or more hydroxyl groups in their molecules. In addition, the polyol according to the present invention may be a substance obtained by reacting propylene oxide or ethylene oxide with an initiator having two or more hydroxyl groups, such as a polyfunctional alcohol or an aromatic amine.

[0044] The above polyols can be broadly classified into polyether polyols and polyester polyols, and according to the present invention, it is preferable to use polyether polyols rather than polyester polyols, which are susceptible to heat and moisture.

[0045] The above polyol process refers to a method for manufacturing fine powder in which a salt, hydroxide, or an inorganic oxidizing compound precursor is dissolved in these alcohols to form reducible metal ions, and then the solution is heated to an appropriate temperature to induce a reduction reaction of the metal ions within the solution.

[0046] The polyol solvent used at this stage creates differences in reducing power and interaction with metal ions depending on its type, which affects the setting of the appropriate synthesis temperature and subsequently influences the size and shape of the synthesized particles; in some cases, it may even transform the resulting particles into hydroxides and oxides.

[0047] Through the above polyol process, the lithium niobate precursor undergoes the following four steps.

[0048] a) Metal ions are reduced to metal atoms;

[0049] b) Aggregation into the nuclear shape of metal atoms;

[0050] c) Growth of the nucleus into metal nanoparticles;

[0051] d) Stabilization of metal nanoparticles by a stabilizer;

[0052] In the first step, a metal salt, acting as a precursor, is dissolved in a liquid polyol. After the dissolved salt is reduced by the polyol, nano-sized particles are generated from the solution through the nucleation and growth processes of the metal particles. Subsequently, the metal nanoparticles are stabilized by a stabilizer.

[0053] The lithium niobate precursor formed by the polyol process has a size of 100 nm or less. As described above, the lithium niobate precursor with nano-sized particles is formed as a high-concentration colloid, and the polyol process has the advantage of having a uniform particle size and excellent dispersion, and not requiring a separate reducing agent.

[0054] Figure 2 shows the chemical formula of a lithium niobate precursor formed by the polyol process described above. The lithium niobate precursor shown in Figure 2 can be formed by mixing lithium hydroxide and ammonium niobate oxalate hydrate. Lithium niobate according to the prior art used lithium ethylate and niobium ethylate, which have high unit costs, but the lithium niobate precursor according to the present invention can be formed using lithium hydroxide and ammonium niobate oxalate hydrate, which have lower unit costs than the lithium ethylate and niobium ethylate, because it is formed through a polyol process.

[0055] Lithium niobate can be obtained by mixing the above lithium hydroxide and ammonium niobate oxalate hydrate, and a polyol process of the lithium niobate precursor can be performed by mixing a chelating agent with the above lithium niobate. The chelating agent may be one or more of the group consisting of citric acid, PVP, carboxylic acid, and weak acid containing a nitrogen element. The chelating agent may be included in an amount of 1 to 10 parts by weight per 100 parts by weight of the lithium niobate.

[0056] The positive electrode active material according to the present invention is a sulfur-carbon composite positive electrode active material comprising a porous carbon material; a compound having electrolyte impregnation properties; and sulfur, wherein at least one of the inner and outer surfaces of the porous carbon material may be a sulfur-carbon composite comprising a coating layer having electrolyte impregnation properties.

[0057] The above positive active material is, for example, in addition to the above positive active material particles, a layered compound such as lithium nickel oxide (LiNiO2) or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 ~ 0.3); chemical formula LiMn 2-x M x Lithium manganese complex oxides represented by O2 (where M = Co, Ni, Fe, Cr, Zn, or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu, or Zn); LiMn2O4 in which part of the Li in the chemical formula is substituted with alkaline earth metal ions; disulfide compounds; Fe2(MoO4) 3, It may be composed of NCM622 and any one of these or a mixture thereof, and also includes other known materials. Among these, it is preferable to use lithium cobalt oxide, which has high energy density, is inexpensive, and is the most superior.

[0058] In addition, the average particle size of the above-mentioned positive active material is not limited in the present invention, but may have an average particle size of 1 nm to 30 µm.

[0059] The solid electrolyte according to the present invention is a sulfide-based solid electrolyte and includes sulfide-based particles. The surface of the sulfide-based particles may be coated or modified for use, and a sulfide-based solid electrolyte is manufactured by passing a mixture containing the particles through a dry or wet process.

[0060] The above-mentioned sulfide-based particles are not specifically limited in the present invention and any known sulfide-based material used in the field of lithium batteries may be used. The above-mentioned sulfide-based material may be purchased commercially or manufactured by subjecting an amorphous sulfide-based material to a crystallization process.

[0061] Representative examples include Li6PS5Cl (LPSCl) and Thio-LISICON(Li 3.25 Ge 0.25 P 0.75 S4), Li2S-P2S5-LiCl, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5, Li3PS4, Li7P3S 11 , LiI-Li2S-B2S3, Li3PO4-Li2S-Si2S, Li3PO4-Li2S-SiS2, LiPO4-Li2S-SiS, Li 10 GeP2S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li7P3S 11 Includes the back

[0062] The conductive material according to the present invention is carbon-based, and the conductive material is not particularly limited as long as it possesses conductivity without causing chemical changes in the battery. Examples include graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as carbon fluoride, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. Any one or more of these may be selected from the group consisting of such materials.

[0063] The binder according to the present invention is not specifically limited in the present invention, and known methods may be used. Any one selected from the group consisting of N,N-bis[3-(triethoxysilyl)propyl]urea, polyethylene oxide (PEO), poly(vinylidene fluoride) (PVDF), and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP), or a mixture of two or more of these; N,N-bis[3-(triethoxysilyl)propyl]urea, polyethylene oxide (PEO), poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP); conjugated diene rubber latex such as acrylonitrile styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), methyl butadiene rubber methacrylate (MBR), butadiene rubber (BR); carboxymethylcellulose (CMC); starch, It may be any one selected from the group consisting of hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene ter polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, various copolymers, etc., or a mixture of two or more of these.

[0064] A sulfide-based all-solid-state battery according to the present invention comprises the steps of: S1) mixing a polyol and a chelating agent to form a polyol precursor; S2) mixing lithium hydroxide and ammonium niobate oxalate hydrate with the polyol precursor to form a positive active material coating material; and S3) coating a positive active material with the positive active material coating material.

[0065] At this time, a chelating agent may not be added in step S1).

[0066] The above step S2) can be mixed using a dry method without a separate solvent. The dry mixing method is as described above.

[0067] In step S3) above, the positive active material coating material and the positive active material are mixed, and then heat-treated at 450°C for 2 hours.

[0068] When performing the above heat treatment, the heat treatment can be carried out by raising the temperature by 5°C per minute starting from room temperature of 25°C to reach the target temperature, and then naturally cooling it down to 25°C.

[0069] Figure 3 is a scanning electron microscope (SEM) image of lithium niobate produced by the polyol process according to the present invention, and Figure 4 is a scanning electron microscope (SEM) image of a positive electrode active material coated with lithium niobate produced by the polyol process according to the present invention. As can be seen in Figures 3 and 4, it can be seen that the lithium niobate precursor produced by the polyol process according to the present invention uniformly coats the positive electrode active material. When the lithium niobate precursor uniformly coats the positive electrode active material as described above, the performance of the sulfide-based all-solid-state battery can be improved by preventing the positive electrode active material from reacting with the sulfide-based solid electrolyte. Furthermore, by coating the positive electrode active material of the sulfide-based all-solid-state battery in a dry state, the concern that the sulfide-based solid electrolyte may react with moisture can be reduced, thereby improving safety and shortening the process.

[0070] This can be seen in more detail through Figures 5 and 6.

[0071] FIG. 5 is a transmission electron microscope (TEM) image of a lithium niobate precursor according to the present invention, and FIG. 6 is a transmission electron microscope (TEM) image of a positive electrode active material coated with a lithium niobate precursor according to the present invention.

[0072] As can be seen in FIG. 5, the lithium niobate precursor according to the present invention may have a shape that is evenly distributed after undergoing a polyol process.

[0073] As can be seen in Fig. 5, Grey, CK, NbL, and OK in Fig. 5 are each Li, C, Nb, and O, and lithium niobate reacts with the polyol, so that each element is evenly distributed in the precursor.

[0074] In addition, as shown in Fig. 6, the evenly distributed lithium niobate precursor (NbL) is evenly coated onto the evenly distributed positive electrode active material (CoK), so that the positive electrode active material does not react with the sulfide-based all-solid-state battery.

[0075] The present invention also provides a battery pack comprising a sulfide-based all-solid-state battery according to the present invention as a unit cell, and a device comprising the battery pack as a power source. Specifically, the battery pack can be used as a power source for a device requiring high temperature safety, long cycle characteristics, and high rate characteristics. Preferred examples of such devices include mobile electronic devices, wearable electronic devices, power tools powered by a battery-based motor; electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or power storage devices, but are not limited thereto.

[0076] Since the structure of these devices and the method of manufacturing them are known in the art, a detailed description thereof is omitted in this specification.

[0077] In FIGS. 7 to 9, a sulfide-based all-solid-state battery according to the present invention was formed as an example, and a battery in which the positive active material was not synthesized with a lithium niobate precursor as in the present invention was formed as a comparative example, and then the specific capacity, capacity retention rate, and impedance values ​​according to the voltage were compared.

[0078] The sulfide-based all-solid-state battery used as an example was prepared by 1) adding 8.6456 mg of citric acid to 100 ml of triethylene glycol (TEG) and mixing the mixture for 20 minutes, 2) mixing 0.4616 mg of lithium hydroxide and 3.0298 mg of ammonium niobate (v) oxalate hydrate at room temperature, synthesizing the mixture at 230°C for 3 hours, 3) gradually cooling the mixture, separating it with a centrifuge, washing it 7 to 8 times with ethanol, and drying it in a vacuum oven at 50°C to 200°C to form a positive electrode active material coating. 4) LiCoO2, which is the positive electrode active material, was coated with the above positive electrode active material coating. At this time, the coating was prepared by mixing the positive active material coating agent and the positive active material in a stirrer, increasing the temperature from room temperature by 5°C increments until it reached 450°C, at which point the temperature was maintained for 3 hours without further increasing. 5) After 3 hours had elapsed, the positive active material coating agent and the positive active material were gradually cooled from room temperature to obtain the coated positive active material.

[0079] 6) Subsequently, the coated positive active material was mixed with carbon black, a conductive material, and polyvinylidene fluoride, a binder, and then applied onto aluminum, which serves as the positive current collector. 7) The electrode slurry was uniformly dispersed onto the current collector using a doctor blade, and then dried in a vacuum oven at 50°C to 200°C to form a positive electrode. A unit cell was formed by stacking the positive electrode with a solid electrolyte layer formed using an LPS-based electrolyte, which is a sulfide-based solid electrolyte, and a negative electrode using copper as the current collector.

[0080] The sulfide-based all-solid-state battery used as a comparative example formed a unit cell in the same manner as the example, except that a positive active material not coated with the positive active material coating material as described above was used.

[0081] Figure 7 is a graph comparing the specific capacity according to voltage of a sulfide-based all-solid-state battery according to the present invention and a sulfide-based all-solid-state battery manufactured with an uncoated positive electrode active material. At this time, the unit cells were charged (CC / CV): 0.1C / 4.15V, 0.02C cut-off, rest 30min, and discharged (CC): 0.1C, 3V cut-off. The specific capacity value was calculated based on the weight including the positive electrode material and the gas diffusion layer.

[0082] As can be seen in Fig. 7, the oxygen reduction curve corresponding to the first cycle of the example is 132 mAh / g and the oxygen release curve is 120 mAh / g, showing a difference of about 92.0%, whereas the oxygen reduction curve of the comparative example is 108 mAh / g and the oxygen release curve is 92 mAh / g, showing a difference of about 86.1% in the initial charge / discharge characteristics, so it can be confirmed that the charge / discharge characteristics according to the example are superior.

[0083] Figure 8 is a graph comparing the capacity retention rates of a sulfide-based all-solid-state battery according to the present invention and a sulfide-based all-solid-state battery manufactured with an uncoated positive electrode active material.

[0084] In Fig. 8, charging and discharging were performed 50 times with (CC / CV): 0.1C / 4.25V, 0.02C cut-off, rest 30min, and discharging (CC): 0.1C, 3V cut-off.

[0085] As can be seen in FIG. 8, the sulfide-based all-solid-state battery according to the embodiment of the present invention not only has a higher initial capacity than the comparative example but also has a superior capacity retention rate compared to the comparative example.

[0086] Figure 9 is a graph comparing the impedance values ​​of a sulfide-based all-solid-state battery according to the present invention and a sulfide-based all-solid-state battery manufactured with an uncoated positive electrode active material.

[0087] In Fig. 9, the AC impedance was measured for the unit cells disassembled in a glove box after storing the unit cells in a fully charged state at a temperature of 60°C for two weeks.

[0088] As can be seen in Fig. 9, the unit cell according to the embodiment has a lower interfacial resistance value between the anode and the solid electrolyte than the comparative example.

[0089] Therefore, it can be confirmed that when a positive electrode active material is dry-coated with a lithium niobate precursor manufactured by a polyol process as in the present invention, the performance of the sulfide-based all-solid-state battery is superior compared to the case where it is not coated with a lithium niobate precursor.

[0090] As specific parts of the present invention have been described in detail above, it is obvious to those skilled in the art that such specific descriptions are merely preferred embodiments and do not limit the scope of the present invention, and that various changes and modifications are possible within the scope and concept of the present invention, and that such variations and modifications fall within the scope of the appended claims.

Claims

Claim 1 A sulfide-based all-solid-state battery comprising a positive electrode active material coated with a lithium niobate precursor manufactured by a polyol process, wherein the polyol precursor is manufactured by mixing a polyol and a chelating agent, the lithium niobate precursor is formed by mixing lithium hydroxide and ammonium niobate oxalate hydrate with the polyol precursor to form a lithium niobate precursor and then drying, and the coating is performed by dry mixing the positive electrode active material and the lithium niobate precursor without a separate solvent and then heat-treating at 400°C or higher. Claim 2 delete Claim 3 delete Claim 4 A sulfide-based all-solid-state battery according to claim 1, wherein the coating is heat-treated by dry mixing of the positive active material and the lithium niobate precursor, raising the temperature by 5°C per minute to reach a target temperature, and then cooling it naturally. Claim 5 A sulfide-based all-solid-state battery according to claim 1, wherein the lithium niobate precursor comprises lithium niobate and a chelating agent. Claim 6 In claim 5, the chelating agent is one or more of the group comprising citric acid, PVP, carboxylic acid, and a weak acid containing a nitrogen element, in a sulfide-based all-solid-state battery. Claim 7 In claim 1, the lithium niobate precursor is coated on the positive electrode active material to a thickness of 1 nm to 100 nm or less in a sulfide-based all-solid-state battery. Claim 8 In claim 1, the positive active material is a sulfide-based all-solid-state battery in which lithium cobalt oxide is the positive active material. Claim 9 S1) a step of forming a polyol precursor by mixing a polyol and a chelating agent; S2) a step of forming a lithium niobate precursor by mixing lithium hydroxide and ammonium niobate oxalate hydrate with the polyol precursor and then drying to form a positive electrode active material coating material; and S3) a step of coating a positive electrode active material by dry mixing the positive electrode active material with the positive electrode active material coating material without a separate solvent and then heat treating at 400°C or higher; comprising a method for coating a positive electrode active material. Claim 10 In claim 9, the above step S3) is a method for coating an anode active material by mixing the anode active material coating material and the anode active material, and then heat-treating the mixture at 450°C or higher for 2 hours. Claim 11 In claim 10, the heat treatment at 450°C or higher for 2 hours is a method of coating an anode active material by raising the temperature by 5°C per minute to reach a target temperature, and then cooling it naturally. Claim 12 In claim 9, the above step S2) is a method for coating an anode active material that proceeds dry.

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