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

Abstract

Disclosed herein are a sulfide-based all-solid-state battery and a method for manufacturing the same, wherein the sulfide-based all-solid-state battery includes a positive electrode active material coated with a lithium niobate precursor, and the lithium niobate precursor is manufactured by a polyol method with low production cost, so that it improves the safety of the sulfide-based all-solid-state battery and increases its capacity.

Description

Technical Field

[0001] This application claims priority based on U.S. patent application No. 16 / 992,274 filed on August 13, 2020, and incorporates all disclosures in that U.S. patent application as part of this specification.

[0002] The present invention relates to a sulfide-based all-solid-state battery including a positive electrode active material coated with a lithium niobate precursor and a method for manufacturing the same, and more particularly, to a sulfide-based all-solid-state battery including a positive electrode active material coated with a lithium niobate precursor manufactured by a polyol method and a method for manufacturing the same. Background Art

[0003] The advantages of lithium-ion secondary batteries are that they have higher energy density, lower self-discharge rate, and longer lifespan than nickel-manganese dioxide batteries or nickel-cadmium batteries. However, lithium-ion secondary batteries have the following disadvantages: their safety is reduced due to overheating, and their output is low.

[0004] To solve the problems of lithium-ion secondary batteries, all-solid-state batteries have been proposed as an alternative. An all-solid-state battery can be configured to have a structure in which a positive electrode layer including a solid electrolyte and a negative electrode layer are formed on opposite surfaces of an electrolyte layer including a solid electrolyte, and a current collector is coupled to each electrode.

[0005] Based on the raw materials of the solid electrolyte, all-solid-state batteries can be classified as oxide-based all-solid-state batteries, polymer-based all-solid-state batteries, or sulfide-based all-solid-state batteries. Sulfide-based all-solid-state batteries have higher lithium ion conductivity than other all-solid-state batteries. However, the disadvantage of sulfide-based all-solid-state batteries is that they have lower ion conductivity than conventional batteries using liquid electrolytes, and the resistance between the positive electrode, negative electrode, and solid electrolyte is high, resulting in low lifespan and output of sulfide-based all-solid-state batteries, which has not yet been overcome.

[0006] The cathode active material and the sulfide-based solid electrolyte react with each other at the interface between them, forming a resistive material that hinders the operation of the all-solid-state battery. Due to this resistive material, the initial capacity and efficiency of the all-solid-state battery are reduced.

[0007] In conventional all-solid-state batteries, the positive electrode active material is coated with lithium niobate, thereby reducing the reactivity of the positive electrode active material with the sulfide-based solid electrolyte, thereby improving the performance of the all-solid-state battery. In the case of Patent Document 1, the positive electrode active material is coated with lithium niobate while using an organic solvent. Therefore, there is a problem that the residual organic solvent must be completely evaporated before the solid electrolyte is used to prevent it from reacting with the sulfide-based solid electrolyte. In addition, lithium ethoxide and niobium ethoxide are used as raw materials to form lithium niobate. As a result, there are problems with high production costs and extended processing time.

[0008] In the case of coating a positive electrode active material with lithium niobate in a dry state, the lithium niobate is unevenly coated on the positive electrode active material, thereby making it difficult to manufacture an inexpensive, high-performance sulfide-based all-solid-state battery.

[0009] Japanese registered patent No. 4982866 (Patent Document 1). Summary of the Invention

[0010] [Technical Issues]

[0011] The present invention is made in view of the above problems, and the purpose of the present invention is to provide a sulfide-based all-solid-state battery, which is manufactured using a stable and economical method: coating the positive electrode active material with a lithium niobate precursor manufactured by a polyol method.

[0012] [Technical solution]

[0013] According to one aspect of the present invention, the above and other objects can be achieved by providing a positive electrode active material coated with a lithium niobate precursor produced by a polyol method. In addition, a sulfide-based all-solid-state battery including the coated positive electrode active material is provided.

[0014] The coating may be a process of mixing the positive electrode active material and the lithium niobate precursor in a dry state without a separate solvent.

[0015] The coating may be performed by mixing the positive electrode active material and the lithium niobate precursor in a dry state, and performing a heat treatment by heating the mixture to a target temperature at a rate of 5° C. / min and then cooling the mixture naturally.

[0016] The lithium niobate precursor may include lithium niobate and a chelating agent.

[0017] The chelating agent may be at least one selected from citric acid, polyvinylpyrrolidone (PVP), carboxylic acid, and a weak acid containing nitrogen element.

[0018] The lithium niobate precursor may be coated on the positive electrode active material in an amount of 1 nm to 100 nm.

[0019] The positive electrode active material may be lithium cobalt oxide. Lithium cobalt oxide may be used as a positive electrode active material according to an embodiment of the present invention, which may be used in a lithium ion secondary battery or an all-solid-state battery.

[0020] According to another aspect of the present invention, a positive electrode active material coating method is provided, which includes: S1) mixing a polyol and a chelating agent with each other to form a polyol precursor, S2) mixing the polyol precursor with lithium hydroxide and ammonium niobate oxalate hydrate to form a positive electrode active material coating material, and S3) coating the positive electrode active material with the positive electrode active material coating material.

[0021] Step S3) may be to mix the positive electrode active material coating material and the positive electrode active material with each other, and heat-treat the mixture at 450° C. or above for 2 hours.

[0022] Furthermore, the heat treatment may be performed at 450° C. or higher for 2 hours using a method of increasing the temperature to a target temperature at a rate of 5° C. / min and then naturally cooling the temperature down.

[0023] Furthermore, step S2) can be performed in a dry state.

[0024] In the present invention, one or more configurations that do not conflict with each other may be selected and combined from the above-mentioned configurations.

[0025] [Beneficial Effects]

[0026] The present invention provides a sulfide-based all-solid-state battery including a cathode active material having low reactivity with a sulfide-based solid electrolyte and having improved safety.

[0027] The positive electrode active material is uniformly coated with lithium niobate, whereby a sulfide-based all-solid-state battery having low reactivity between the sulfide-based solid electrolyte and the positive electrode active material and having improved performance can be provided.

[0028] Furthermore, by performing a coating method that has been conventionally performed in a wet state in a dry state, an economical manufacturing method with a simplified process can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a flow chart illustrating a method of coating a positive electrode active material with a lithium niobate precursor according to the present invention.

[0030] Figure 2 The chemical formula of the lithium niobate precursor produced by the polyol method is shown.

[0031] Figure 3 This is a scanning electron microscope (SEM) photograph of the lithium niobate precursor produced by the polyol method of the present invention.

[0032] Figure 4FIG. 4 is a scanning electron microscope (SEM) photograph of a positive electrode active material coated with the lithium niobate precursor prepared by the polyol method of the present invention.

[0033] Figure 5 This is a transmission electron microscope (TEM) photograph of the lithium niobate precursor of the present invention.

[0034] Figure 6 FIG1 is a transmission electron microscope (TEM) photograph of a positive electrode active material coated with the lithium niobate precursor of the present invention.

[0035] Figure 7 Graph comparing the specific capacity based on voltage between the sulfide-based all-solid-state battery of the present invention and a sulfide-based all-solid-state battery manufactured using an uncoated positive electrode active material.

[0036] Figure 8 This is a graph comparing the capacity retention rates of the sulfide-based all-solid-state battery of the present invention and a sulfide-based all-solid-state battery manufactured using an uncoated positive electrode active material.

[0037] Figure 9 Graph comparing impedance between the sulfide-based all-solid-state battery of the present invention and a sulfide-based all-solid-state battery manufactured using an uncoated positive electrode active material. DETAILED DESCRIPTION

[0038] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the preferred embodiments of the present invention. However, when describing in detail the operating principles of the preferred embodiments of the present invention, when the detailed description of known functions and configurations incorporated herein may obscure the subject matter of the present invention, the detailed description will be omitted.

[0039] In addition, the same reference numerals are used throughout the drawings to represent components that perform similar functions or operations. Where a component is referred to in the specification as being connected to another component, the component may be directly connected to the other component and may also be indirectly connected to the other component via yet another component. In addition, the inclusion of a certain element does not mean the exclusion of other elements, but rather means that these other elements may be further included unless otherwise specified.

[0040] Furthermore, the description of implementing an element by defining or supplementing an element is applicable to all inventions unless there is a specific limitation, and does not define a specific invention.

[0041] Furthermore, in the description and claims of the invention of this application, the singular form is intended to include the plural form unless otherwise stated.

[0042] In addition, in the description and claims of the invention of this application, "or" includes "and" unless otherwise specified. Therefore, "including A or B" refers to three cases, namely, the case including A, the case including B, and the case including A and B.

[0043] Furthermore, all numerical ranges include the lower value, the upper value and all intermediate values ​​therebetween unless the context clearly dictates otherwise.

[0044] Hereinafter, the present invention will be described in more detail.

[0045] The present invention may include a positive electrode active material coated with a lithium niobate precursor produced by a polyol method.

[0046] Figure 1 1 is a flow chart showing the method of coating a positive electrode active material with a lithium niobate precursor according to the present invention. Figure 1 In FIG, LCO represents a positive electrode active material, and LNO coating represents a lithium niobate precursor produced by a polyol method and coated on the positive electrode active material.

[0047] from Figure 1 As can be seen in Figure 2, the positive electrode active material of the present invention is mixed with the lithium niobate precursor in a dry state without a separate solvent. The present invention is not limited to the mixing method, and any known method can be used. The mixing can be carried out by a conventional mechanochemical reaction. In addition, a conventional stirrer, mixer, planetary ball mill or mortar mixer can be used for mixing. When a planetary ball mill is used, the positive electrode active material and the lithium niobate precursor can be mixed under the conditions of 50 to 500 rpm, 0.1 to 10 hours and 1 to 100 kWH / 1kg.

[0048] Although there is no limitation on the moisture content of each particle as long as the particles are in a dry state, the particles are preferably dried at 120° C. for 6 hours.

[0049] The weight ratio of the lithium niobate precursor to the positive electrode active material is not particularly limited, as long as the lithium niobate precursor is provided in an amount capable of coating 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 2 to 5:98 to 95.

[0050] After the positive electrode active material and the lithium niobate precursor are mixed in a dry state, the mixture may be heat-treated at a temperature above 400° C. As a result of the heat treatment, the bonding force between the lithium niobate precursor and the positive electrode active material is increased, thereby allowing the lithium niobate precursor coated on the positive electrode active material to be in close contact with the positive electrode active material.

[0051] The heat treatment can be performed by increasing the temperature to a target temperature at a rate of 5°C / minute and then cooling it naturally. In this case, the target temperature is preferably not more than 500°C. When heat of 500°C or higher is applied, cobalt from lithium cobalt oxide used as a positive electrode active material may diffuse into the lithium niobate precursor and thus react with the sulfide-based solid electrolyte due to the high temperature.

[0052] After reaching the target temperature, the lithium niobate precursor and the positive active material may be left to stand for 1 to 3 hours until the lithium niobate precursor and the positive active material are naturally cooled to 25°C.

[0053] The heat treatment is performed in a single process because it is necessary to achieve uniform and regular bonding between the lithium niobate precursor and the positive electrode active material and to prevent the formation of empty spaces between the lithium niobate precursor and the positive electrode active material.

[0054] After the heat treatment, the lithium niobate precursor may be coated on the positive electrode active material. The lithium niobate precursor may be coated on the positive electrode active material in an amount of 1 nm to 100 nm.

[0055] The polyol used in the polyol method generally refers to a variety of alcohols containing two or more hydroxyl groups or amine groups per molecule. In addition, the polyol of the present invention may be a material obtained by reacting an initiator having two or more hydroxyl groups or amine groups (i.e., an initiator such as a polyfunctional alcohol or an aromatic amine) with propylene oxide or ethylene oxide.

[0056] Polyols can be generally classified as polyether polyols or polyester polyols, and it is preferred to use polyether polyols rather than polyester polyols (which have low heat resistance and moisture resistance) as the polyol of the present invention.

[0057] The polyol method refers to a fine powder production method in which a salt, hydroxide, or inorganic compound oxide precursor is dissolved in alcohol to form a reducible metal ion and the solution is heated to an appropriate temperature to induce a reduction reaction of the metal ion in the solution.

[0058] Since the polyol solvent used at this time differs in reducing ability and interaction with metal ions depending on its type, the polyol solvent affects the appropriate synthesis temperature setting and the size and shape of the particles synthesized thereafter, and also changes the generated particles into hydroxides or oxides depending on the situation.

[0059] Through the polyol method, the lithium niobate precursor undergoes the following four steps:

[0060] a) reducing metal ions to metal atoms;

[0061] b) nucleation and aggregation of metal atoms;

[0062] c) nucleus growth into metallic nanoparticles; and

[0063] d) Using a stabilizer to stabilize the metal nanoparticles.

[0064] In the initial step, a metal salt as a precursor material is dissolved in a liquid polyol, the dissolved salt is reduced by the polyol, and nanoparticles are generated from the solution through the generation and growth of metal particle nuclei. Subsequently, the metal nanoparticles are stabilized by a stabilizer.

[0065] The lithium niobate precursor formed by the polyol method has a size of 100 nm or less. The lithium niobate precursor having the nanoparticle size described above is formed as a high-concentration colloid. The particles obtained by the polyol method are uniform in size and well dispersed, and no separate reducing agent is required.

[0066] Figure 2 The chemical formula of the lithium niobate precursor formed by the polyol method is shown. Figure 2 The lithium niobate precursor shown can be formed by mixing lithium hydroxide and ammonium niobate oxalate hydrate. Conventional lithium niobate uses lithium ethoxide and niobium ethoxide, which have high unit costs. However, since the lithium niobate precursor of the present invention is formed using a polyol method, lithium niobate can be formed from lithium hydroxide and ammonium niobate oxalate hydrate, which has a lower unit cost than lithium ethoxide and niobium ethoxide.

[0067] Lithium hydroxide and ammonium niobate oxalate hydrate may be mixed to obtain lithium niobate, and the lithium niobate may be mixed with a chelating agent to perform a polyol method for preparing a lithium niobate precursor. The chelating agent may be at least one selected from citric acid, polyvinylpyrrolidone (PVP), a carboxylic acid, and a weak acid containing nitrogen. The chelating agent may account for 1 to 10 parts by weight based on 100 parts by weight of the lithium niobate.

[0068] The positive electrode active material of the present invention may be a sulfur-carbon composite positive electrode active material comprising a porous carbon material, a compound having electrolyte impregnation properties, and sulfur, and at least one of the inner surface or the outer surface of the porous carbon material may be a sulfur-carbon composite material comprising a coating comprising a compound having electrolyte impregnation properties.

[0069] For example, the positive electrode active material can be made of a layered compound such as lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; 1+x Mn 2-x Lithium manganese oxide represented by O4 (wherein x = 0 to 0.33), or lithium manganese oxide such as LiMnO3, LiMn2O3 or LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxide such as LiV3O8, LiV3O4, V2O5 or Cu2V2O7;1-x M x Nickel-type lithium nickel oxide represented by O2 (wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); 2-x M x Lithium manganese composite oxides represented by the formula LiMnO2 (where M = Co, Ni, Fe, Cr, Zn, or Ta, and x = 0.01 to 0.1) or LiMnO4 (where M = Fe, Co, Ni, Cu, or Zn); LiMnO4, in which the Li in the chemical formula is partially substituted with an alkaline earth metal ion; disulfides; or Fe(MoO4)3, NCM622, and mixtures of one or all thereof. Other known materials may be used. Among these, lithium cobalt oxide, which has high energy density, is inexpensive, and is the best choice, is preferably used.

[0070] In addition, the average particle size of the positive electrode active material may be 1 nm to 30 μm, but the average particle size of the positive electrode active material of the present invention is not limited.

[0071] The solid electrolyte of the present invention is a sulfide-based solid electrolyte comprising sulfide-based particles. The surface of the sulfide-based particles may be coated or refined, and a mixture containing the particles is used to produce the sulfide-based solid electrolyte by a dry method or a wet method.

[0072] In the present invention, there is no particular limitation on the sulfide-based particles, and all known sulfide-based materials used in the field of lithium batteries are feasible. Commercial products or materials manufactured by crystallizing amorphous sulfide-based materials can be used as the sulfide-based material.

[0073] Typically, including Li6PS5Cl (LPSCl), sulfo-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 and Li7P3S11 .

[0074] The conductive agent of the present invention is a carbon-based conductive agent and is not particularly limited as long as it exhibits high conductivity without causing any chemical changes in the battery to which it is applied. For example, the conductive agent can be at least one selected from the following: 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 fluorinated carbon powder, aluminum powder, or nickel powder; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0075] The adhesive of the present invention is not particularly limited, and known adhesives can be used. The adhesive can be any one selected from 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 thereof, or can be at least one selected from the following group: N,N-bis[3-(triethoxysilyl)propyl]urea, polyethylene oxide (PEO), poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) co-HFP), conjugated diene rubber latex (such as acrylonitrile styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), methyl methacrylate butadiene styrene (MBR) or butadiene rubber (BR)), carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber and various copolymers or mixtures of two or more thereof.

[0076] The manufacturing method of the sulfide-based all-solid-state battery of the present invention includes: S1) a step of mixing a polyol and a chelating agent with each other to form a polyol precursor, S2) a step of mixing the polyol precursor with lithium hydroxide and ammonium niobate oxalate hydrate to form a positive electrode active material coating material, and S3) a step of coating the positive electrode active material with the positive electrode active material coating material.

[0077] In step S1), no chelating agent may be added.

[0078] In step S2), the mixing can be performed using a dry method without a separate solvent. The dry mixing method has been described above.

[0079] In step S3), the positive electrode active material coating material and the positive electrode active material may be mixed with each other, and the mixture may be heat-treated at 450° C. for 2 hours.

[0080] The heat treatment may be performed using a method of increasing the temperature from 25° C. (room temperature) to a target temperature at a rate of 5° C. / min and decreasing the temperature to 25° C. by natural cooling.

[0081] Figure 3 This is a scanning electron microscope (SEM) photograph of a lithium niobate precursor produced by the polyol method of the present invention. Figure 4 : is a scanning electron microscope (SEM) photograph of a positive electrode active material coated with a lithium niobate precursor produced by the polyol method of the present invention. Figure 3 and 4 As can be seen, the positive electrode active material is uniformly coated with the lithium niobate precursor produced by the polyol method of the present invention. As described above, when the positive electrode active material is uniformly coated with the lithium niobate precursor, the positive electrode active material can be prevented from reacting with the sulfide-based solid electrolyte, thereby improving the performance of the sulfide-based all-solid-state battery. Furthermore, since the positive electrode active material of the sulfide-based all-solid-state battery is applied in a dry state, concerns about the reaction of the sulfide-based solid electrolyte with moisture can be reduced, thereby improving safety and shortening the process.

[0082] This can be done by Figure 5 and 6 Understand in more detail.

[0083] Figure 5 is a transmission electron microscope (TEM) photograph of the lithium niobate precursor of the present invention, Figure 6 FIG1 is a transmission electron microscope (TEM) photograph of a positive electrode active material coated with the lithium niobate precursor of the present invention.

[0084] from Figure 5 It can be seen that the lithium niobate precursor of the present invention can have a uniformly distributed shape through the polyol method.

[0085] exist Figure 5 In the figure, gray, CK, NbL and OK represent Li, C, Nb and O respectively. Figure 5 It can be seen that lithium niobate reacts with the polyol, so that the elements are evenly distributed in the precursor.

[0086] In addition, from Figure 6 As can be seen in FIG, the uniformly distributed lithium niobate precursor (NbL) is coated on the uniformly distributed positive electrode active material (CoK), whereby the positive electrode active material does not react with the sulfide-based solid electrolyte.

[0087] In addition, the present invention provides a battery pack including a sulfide-based all-solid-state battery as a unit cell and a device including the battery pack as a power source. Specifically, the battery pack can be used as a power source for devices that require the ability to withstand high temperatures, long life, high rate characteristics, etc. Preferred examples of the device may include: mobile electronic devices, wearable electronic devices, power tools driven by battery-powered motors, electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and power storage devices. However, the present invention is not limited thereto.

[0088] The structure and manufacturing method of the apparatus are well known in the art to which the present invention pertains, and thus detailed descriptions thereof will be omitted from this specification.

[0089] Figures 7 to 9 The figures show a comparison of the voltage-based specific capacity, capacity retention, and impedance between the sulfide-based all-solid-state battery of the present invention as an embodiment and a battery manufactured using a positive electrode active material without synthesizing a lithium niobate precursor as a comparative example different from the present invention.

[0090] In the case of a sulfide-based all-solid-state battery used as an example, 1) 8.6456 mg of citric acid was placed in 100 ml of triethylene glycol (TEG) and mixed for 20 minutes; 2) the mixture was mixed with 0.4616 mg of lithium hydroxide and 3.0298 mg of ammonium niobate (V) oxalate hydrate at room temperature and synthesized at 230° C. for 3 hours; and 3) the synthesized product was gradually cooled, centrifuged, washed 7 or 8 times with ethanol, and dried in a vacuum oven at 50° C. to 200° C. to form a positive electrode active material coating material; 4) the positive electrode active material LiCoO2 was coated with the positive electrode active material coating material. During the coating, the temperature was increased from room temperature at a rate of 5° C. / minute while the positive electrode active material coating material and the positive electrode active material were mixed with each other using a stirrer, and when the temperature reached 450° C., the temperature was maintained for 3 hours without increasing the temperature; 5) after 3 hours, the positive electrode active material coating material and the positive electrode active material were gradually cooled to room temperature to obtain a coated positive electrode active material.

[0091] 6) Subsequently, the coated positive electrode active material is mixed with carbon black as a conductive agent and polyvinylidene fluoride as a binder, and the mixture is applied to aluminum as the positive electrode current collector. 7) The electrode slurry is evenly distributed on the current collector using a doctor blade and dried in a vacuum oven at 50°C to 200°C to form a positive electrode. The positive electrode, a solid electrolyte layer formed using an LPS-based electrolyte (sulfide-based solid electrolyte), and a negative electrode using copper as the current collector are stacked to form a unit cell.

[0092] In the case of a sulfide-based all-solid-state battery serving as a comparative example, a unit cell was formed using the same method as in Example, except that a positive electrode active material not coated with the positive electrode active material coating material was used.

[0093] Figure 7 This graph compares the voltage-dependent specific capacity of the sulfide-based all-solid-state battery of the present invention with that of a sulfide-based all-solid-state battery manufactured using uncoated positive electrode active material. The cells were charged under CC / CV conditions of 0.1C / 4.15V, 0.02C cutoff, and a 30-minute rest period, and discharged under CC conditions of 0.1C and 3V cutoff. The specific capacity was calculated based on the weight of the positive electrode material and gas diffusion layer, including the positive electrode.

[0094] from Figure 7 It can be seen that in the case of the example, the oxygen reduction curve corresponding to the first cycle is 132 mAh / g, and the oxygen release curve is 120 mAh / g, resulting in a difference of approximately 92.0%. In contrast, the oxygen reduction curve of the comparative example is 108 mAh / g, and the oxygen release curve of the comparative example is 92 mAh / g, resulting in a difference of approximately 86.1% in the initial charge and discharge characteristics. Therefore, it can be seen that the charge and discharge characteristics of the example are excellent.

[0095] Figure 8 This is a graph comparing the capacity retention rates of the sulfide-based all-solid-state battery of the present invention and a sulfide-based all-solid-state battery manufactured using an uncoated positive electrode active material.

[0096] refer to Figure 8 The battery was charged under CC / CV conditions of 0.1C / 4.25V, 0.02C cutoff, and rest for 30 minutes, and discharged under CC conditions of 0.1C and 3V cutoff. Charging and discharging were performed 50 times.

[0097] from Figure 8 It can be seen that in the case of the sulfide-based all-solid-state battery of the embodiment of the present invention, the initial capacity is higher and the capacity retention rate is better than that of the comparative example.

[0098] Figure 9 Graph comparing impedance between the sulfide-based all-solid-state battery of the present invention and a sulfide-based all-solid-state battery manufactured using an uncoated positive electrode active material.

[0099] refer to Figure 9 The unit cells were stored at 60°C for 2 weeks in a fully charged state, then disassembled from the glove box, and the alternating current (AC) impedance of each unit cell was measured.

[0100] from Figure 9It can be seen that in the case of the unit cell of the embodiment, the interface impedance value between the positive electrode and the solid electrolyte is lower than that of the comparative example.

[0101] Therefore, it can be seen that when the positive electrode active material is coated with a lithium niobate precursor produced by a polyol method in a dry state as in the present invention, the performance of the sulfide-based all-solid-state battery is better than when the positive electrode active material is not coated with the lithium niobate precursor.

[0102] Although the present invention has been described in detail, it will be understood by those skilled in the art that the detailed description thereof only discloses the preferred embodiments of the present invention and therefore does not limit the scope of the present invention. Therefore, it will be understood by those skilled in the art that various changes and modifications are possible without departing from the scope and technical ideas of the present invention, and it is obvious that such changes and modifications fall within the scope of the appended claims.

[0103] [Industrial Applicability]

[0104] 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. Therefore, the present invention has industrial applicability.

Claims

1. A sulfide-based all-solid-state battery comprising a positive electrode active material coated with a lithium niobate precursor produced by a polyol method; in, The polyol method comprises the following steps: S1) mixing a polyether polyol and a chelating agent with one another to form a polyol precursor, S2) dry-mixing the polyol precursor with lithium hydroxide and ammonium niobate oxalate hydrate to form a lithium niobate precursor; Wherein, after step S2), the positive electrode active material is coated in the following manner: the positive electrode active material and the lithium niobate precursor are mixed in a dry state without a separate solvent, and heat-treated at 400° C. or above.

2. The sulfide-based all-solid-state battery according to claim 1, wherein: The positive electrode active material was coated in the following manner: the positive electrode active material and the lithium niobate precursor were mixed in a dry state, and the heat treatment was performed by increasing the temperature to a target temperature at a rate of 5° C. / min and naturally cooling the temperature down.

3. The sulfide-based all-solid-state battery according to claim 1, wherein: The lithium niobate precursor includes lithium niobate and a chelating agent.

4. The sulfide-based all-solid-state battery according to claim 3, wherein: The chelating agent is at least one selected from the group consisting of citric acid, polyvinylpyrrolidone (PVP), carboxylic acid, and weak acid containing nitrogen element.

5. The sulfide-based all-solid-state battery according to claim 1, wherein The lithium niobate precursor is coated on the positive electrode active material in an amount of 1 nm to 100 nm.

6. The sulfide-based all-solid-state battery according to claim 1, wherein: The positive electrode active material is lithium cobalt oxide.

7. The sulfide-based all-solid-state battery according to claim 1, wherein: The weight ratio of the lithium niobate precursor to the positive electrode active material is 1 to 10:90 to 99.

8. The sulfide-based all-solid-state battery according to claim 2, wherein: The target temperature does not exceed 500°C.

9. A method for coating a positive electrode active material, the method comprising: S1) mixing a polyether polyol and a chelating agent to form a polyol precursor; S2) dry-mixing the polyol precursor with lithium hydroxide and ammonium niobate oxalate hydrate 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 in the following manner: mixing the positive electrode active material and the positive electrode active material coating material in a dry state without a separate solvent, and performing a heat treatment at 400° C. or above.

10. The method for coating a positive electrode active material according to claim 9, wherein: Step S3) is performed by mixing the positive electrode active material coating material and the positive electrode active material with each other and heat-treating the mixture at 450° C. or above for 2 hours.

11. The method for coating a positive electrode active material according to claim 10, wherein: The heat treatment was performed at 450°C or above for 2 hours by increasing the temperature to the target temperature at a rate of 5°C / min and cooling down naturally.

12. The method for coating a positive electrode active material according to claim 9, wherein: The polyol is triethylene glycol.

13. The method for coating a positive electrode active material according to claim 11, wherein: The target temperature does not exceed 500°C.

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