Synthesis of Nanostructured Zirconium Phosphate

Abstract

Synthesis of Nanostructured Zirconium Phosphate The present invention relates to a method for producing zirconium phosphate by flame spray pyrolysis, zirconium phosphate obtained by this method, and its use in batteries, in particular for encapsulating lithium mixed oxide particles.

Description

Technical Field

[0001] The present invention relates to a method for producing zirconium phosphate by a flame spray pyrolysis method, zirconium phosphate obtained by this method, and its use in a battery, particularly for encapsulating lithium mixed oxide particles.

Background Art

[0002] Lithium-ion secondary batteries are one of the most important batteries currently in use. A lithium-ion secondary battery generally consists of an anode made of a carbon material or a lithium metal alloy, a cathode made of a lithium metal oxide, an electrolyte in which a lithium salt is dissolved in an organic solvent, and a separator that allows lithium ions to pass between the positive and negative electrodes during the charge and discharge processes.

[0003] Recently, there has been significant progress in using solid electrolytes instead of liquid electrolytes in order to develop secondary batteries with improved essential safety and energy density. Among such systems, lithium secondary batteries equipped with electrodes made of lithium metal or lithium metal alloys are considered to provide a high energy density and be particularly suitable. Such all-solid-state lithium-ion secondary batteries need to have excellent ionic conductivity at the interface between the electrode active material and the electrolyte in order to have the required load characteristics. This high ionic conductivity can be achieved by coating the surface of the active electrode material with some lithium-containing compounds such as LiTi2(PO4)3, as described in Japanese Patent No. 4982866.

[0004] A common major problem with cathode materials is aging degradation and the accompanying performance degradation during cycling. This phenomenon is particularly relevant to high-nickel NMC. During cycling, the cathode material is affected by several electrochemical degradation mechanisms. Ni in a highly delithiated state 4+The crystal structure becomes unstable due to the reduction and the formation of phases such as NiO due to oxygen loss, and surface changes such as the rearrangement of transition metals. This phase transition has been associated with the initial cracking of cathode particles and subsequent particle disintegration. Furthermore, the electrolyte decomposes at the reactive surface of NMC, and the electrolyte decomposition products accumulate at the interface, increasing the resistance. Additionally, the conductive salt LiPF6 commonly used in liquid electrolytes reacts with trace amounts of H2O contained in all commercially available formulations to form HF. The resulting acidic HF causes lattice strain in the cathode material by dissolving transition metal ions from the surface of the cathode material into the electrolyte. All of these degradation mechanisms lead to a decrease in capacity, performance, and cycle life. Surface coating of the cathode active material has proven to be a very important way to address this aging problem by suppressing direct contact between the surface of the active material and the liquid electrolyte.

[0005] International Publication No. WO 2021 / 089886 describes a method for producing lithium zirconium phosphate using lithium, phosphorus, and zirconium compounds as precursors and by flame spray pyrolysis. The method described in this document is suitable for producing lithium zirconium phosphate with acceptable optical properties, but the throughput is limited if it is necessary to make the desired product as white as possible. When the flow rate of the gas stream introduced into the flame pyrolysis is set to a high value, a gray product that is not suitable for industrial use is produced. The gray characteristics are the result of incomplete combustion of the precursor and are caused by carbon residues in the product. In particular, due to the increasing demand for electronic devices and energy storage devices, there is an increasing demand for materials with optimized characteristics that can be obtained on an industrial scale with high throughput.

[0006] A promising material that can also be used in batteries is zirconium phosphate. K. Min et al. described a lithium-reactive coating with metal phosphates in Sci Rep. 2017;7:7151. Cobalt phosphate, manganese phosphate, and iron phosphate are considered to be excellent coating materials at the interface of cathode active materials for lithium-reactive coatings.

[0007] U.S. Patent Application Publication No. 2007 / 0224483 describes the preparation of precursor organic solutions of tetravalent metal phosphates and pyrophosphates of various metals. An important property of these solutions is that when the solvent evaporates, the above compounds are formed and the compounds can be inserted into the pores of porous membranes, within polymer membranes, and at the electrode interfaces of fuel cells.

[0008] Furthermore, the general strategy described in the literature for obtaining a cathode material coated with zirconium pyrophosphate requires a cumbersome wet chemical process involving long reaction times and subsequent drying and high-temperature calcination steps. Such a wet chemical method for zirconium pyrophosphate is described by Maati Houda et al. in Catalysis Letters, Volume 148, Number 2, pages 699 - 711 (Diastereoselective synthesis of [β]-aminoketones by one-pot three-component Mannich reaction using nanostructured zirconium pyrophosphate catalysts).

[0009] In such a wet chemical process, powders of zirconium pyrophosphate with a wide particle size distribution and an unfavorable tapping density are produced. In particular, when used in electrodes and batteries, specific property profiles are required that cannot be achieved with wet chemically produced materials. Wet chemically produced materials usually have higher density strong aggregates, resulting in low dispersibility, and these materials are disadvantageously coated non-uniformly on the electrodes of the battery.

[0010] Therefore, these methods are not only time-consuming and costly but also do not provide materials for use in batteries and are thus not suitable for industrial applications.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

[0012] The problem addressed by the present invention is to provide an improved method for the industrial production of nanosized and nanostructured zirconium phosphate that can be easily used in batteries. [Means for Solving the Problems]

[0013] Specifically, this method should provide zirconium phosphate particles with a relatively small particle size, a high BET surface area, and a low tapping density.

[0014] Spray pyrolysis is a known method for producing various metal oxides and certain metal salts.

[0015] In spray pyrolysis, metal compounds in the form of fine droplets are introduced into a high-temperature region where they are oxidized and / or hydrolyzed to obtain the corresponding metal oxides or salts. A special form of this method is flame spray pyrolysis in which droplets are supplied to a flame formed by the ignition of a fuel gas and an oxygen-containing gas.

[0016] During the experiment, surprisingly, it was found that by using a special combination of a precursor and a solvent, zirconium diphosphate with desired particle properties can be directly prepared by flame spray pyrolysis. Manufactured by the flame process, the nanostructured zirconium pyrophosphate produced by the pyrolysis method exhibits a narrow particle size distribution with unimodality, combined with excellent dispersibility during the dry coating process. This causes complete deagglomeration of strongly aggregated zirconium diphosphate aggregates, and ultimately enables the formation of a complete and homogeneous zirconium diphosphate coating layer around the lithium mixed oxide cathode particles produced by dry coating of the powder. This high-intensity dry coating method is very time-efficient. Furthermore, the materials of the present invention exhibit a high affinity for reacting with residual lithium ion-containing species on the surface of the cathode active material. Otherwise, the residual lithium ion-containing species would interfere with the function of the battery. Without being bound by theory, it is expected that the lithium ion-containing species will react with zirconium diphosphate to partially form lithium zirconium diphosphate, a generally known battery material.

[0017] Zirconium diphosphate The present invention relates to in the form of strongly aggregated primary particles, with a BET surface area (DIN 9277:2014) of 5 m 2 / g to 100 m 2 / g, and a number average particle size d 50 measured by static light scattering (SLS) of 0.03 μm to 2 μm, and a tapping density (DIN ISO 787-11:1995) of 20 g / L to 200 g / L, and provides zirconium diphosphate produced by a pyrolysis method of the general formula ZrP2O7.

[0018] The zirconium diphosphate of the present invention can be obtained by the method of the present invention described below.

[0019] The zirconium diphosphate produced by the pyrolysis method of the present invention has a surface area of 5 m 2 / g to 100 m 2 / g, preferably 7 m2 / g to 80 m 2 / g, more preferably 15 m 2 / g to 60 m 2 / g has a BET surface area. The BET surface area can be measured by nitrogen adsorption by the Brunauer-Emmett-Teller method in accordance with DIN 9277:2014.

[0020] The zirconium phosphate produced by the thermal decomposition method of the present invention is in the form of strongly aggregated primary particles having a number average diameter of typically 1 to 100 nm, preferably 3 to 70 nm, more preferably 5 to 50 nm, as measured by transmission electron microscopy (TEM). This number average diameter can be measured by calculating the average size of at least 500 particles analyzed by TEM.

[0021] The number average particle diameter d of zirconium phosphate in an aggregated or weakly aggregated form, if necessary, obtained by measuring by static light scattering (SLS) after subjecting a mixture consisting of 5% by weight of particles and 95% by weight of an aqueous solution of sodium pyrophosphate at 0.5 g / L to ultrasonic treatment at 25°C for more than 300 seconds 50 is about 0.03 μm to 2 μm, more preferably 0.04 μm to 1 μm, and even more preferably 0.05 μm to 0.5 μm.

[0022] Weak aggregates and some strong aggregates can be broken by pulverizing or ultrasonic treating the particles, and as a result, particles having a small particle size and a narrow particle size distribution are obtained.

[0023] The zirconium phosphate produced by the thermal decomposition method according to the present invention has a tapping density of 20 g / L to 200 g / L, preferably 25 g / L to 150 g / L, more preferably 30 g / L to 100 g / L, and even more preferably 40 g / L to 80 g / L. The tapping density of a powdery or coarse-grained granular material can be measured in accordance with DIN ISO 787-11:1995 "General test methods for pigments and extenders - Part 11: Measurement of tapped volume and apparent density after tapping". This includes the measurement of the apparent density of the bed after agitation and tapping.

[0024] Method for producing zirconium phosphate The present invention further provides a method for producing zirconium phosphate of the present invention by flame spray pyrolysis, - at least one zirconium compound selected from carboxylates, each of these zirconium carboxylates having 5 to 20 carbon atoms, - organic phosphoric acid, - a solvent containing less than 10% by weight of water and provides a method of subjecting a solution containing the same to flame spray pyrolysis.

[0025] In the flame spray pyrolysis method of the present invention, usually, a solution of a zirconium compound (metal precursor) and a phosphorus source in the form of fine droplets is introduced into a flame formed by ignition of a fuel gas and an oxygen-containing gas. The metal precursor used is oxidized and / or hydrolyzed together with the phosphorus source to obtain the corresponding zirconium phosphate.

[0026] By this reaction, first, highly dispersed substantially spherical primary particles are formed, which aggregate in a further process of the reaction to form strong aggregates. Thereafter, the strong aggregates can accumulate into weak aggregates. Weak aggregates can usually be relatively easily separated into strong aggregates by the introduction of energy, but strong aggregates cannot be further decomposed without intensive introduction of energy. The resulting strongly aggregated compound can be called "fumed" or "produced by pyrolysis" zirconium phosphate.

[0027] The flame spray pyrolysis method is generally described in, for example, WO 2015 / 173114 pamphlet.

[0028] The flame spray pyrolysis method of the present invention preferably includes the following steps: a) a step of atomizing a solution of a zirconium compound with a spray gas to obtain an aerosol, b) a step of reacting the aerosol in a reaction space of a reactor using a flame obtained by ignition of a mixture of a fuel gas and an oxygen-containing gas to obtain a reaction stream, c) A step of cooling the reaction stream; d) Subsequently, a step of removing the solid zirconium phosphate from the reaction stream.

[0029] Examples of the fuel gas include hydrogen, methane, ethane, natural gas and / or carbon monoxide. It is particularly preferred to use hydrogen. The fuel gas is particularly used in embodiments where a high crystallinity of the zirconium phosphate to be produced is desired.

[0030] The oxygen-containing gas is generally air or oxygen-enriched air. The oxygen-containing gas is particularly used, for example, in embodiments where a high BET surface area of the zirconium phosphate to be produced is desired. The total amount of oxygen is generally selected to be at least sufficient for the complete conversion of the fuel gas and the metal precursor.

[0031] To obtain an aerosol, the vaporized solution containing the metal precursor can be mixed with a spray gas such as nitrogen, air, and / or other gases. The resulting fine droplets of the aerosol preferably have an average droplet size of 1 to 120 μm, particularly preferably 30 to 100 μm. The droplets are usually generated using single or multiple material nozzles. The solution may be heated to increase the solubility of the metal precursor and obtain a viscosity suitable for atomization of the solution.

[0032] The metal precursor used in the method of the present invention contains at least one zirconium carboxylate each having 5 to 20 carbon atoms. The zirconium carboxylates used in the method of the present invention can be linear, branched or cyclic pentanoates (C5), hexanoates (C6), heptanoates (C7), octanoates (C8), nonanoates (C9), decanoates (D10), undecanoates (C11), dodecanoates (C12), tridecanoates (C13), tetradecanoates (C14), pentadecanoates (C15), hexadecanoates (C16), heptadecanoates (C17), octadecanoates (C18), nonadecanoates (C19), icosanoates (C20) of lithium and / or zirconium, and mixtures thereof. Most preferably, zirconium 2-ethylhexanoate (C8) is used.

[0033] The metal precursors used can include other salts of zirconium such as nitrates, carbonates, chlorides, bromides, or other organometallic compounds such as alkoxides, for example ethoxides, n-propoxides, isopropoxides, n-butoxides and / or tert-butoxides.

[0034] The term "organic phosphoric acid" in the context of this specification refers to all compounds having at least one group (R) having at least one carbon atom bonded to the phosphorus atom of the unit P(=O) via an oxygen atom, for example, compounds of the general formula (RO)3P(=O) or (RO)(P(=O))2 (wherein R is a group having at least one carbon atom, for example methyl or ethyl).

[0035] The organic phosphoric acids used in the method of the present invention are preferably selected from phosphonic acid (H3PO3), orthophosphoric acid (H3PO4), metaphosphoric acid (HPO3), pyrophosphoric acid (H4P2O7), esters of polyphosphoric acid, and mixtures thereof.

[0036] The organic phosphoric acid can be selected from alkyl esters such as methyl, ethyl, propyl, butyl, hexyl, aryl esters such as phenyl, mixed alkyl / aryl esters, and mixtures thereof. The organic phosphoric acid is preferably an ester having a group with 1 to 10 carbon atoms, most preferably an alkyl group having 1 to 10 carbon atoms.

[0037] Surprisingly, it has been found that using organic phosphoric acid as a phosphorus source is important for obtaining small zirconium phosphate particles with a high BET surface area and a low tapping density.

[0038] The solvent mixture used in the method of the present invention can be selected from the group consisting of linear or cyclic saturated or unsaturated aliphatic or aromatic hydrocarbons, carboxylic acid esters, ethers, alcohols, carboxylic acids, and mixtures thereof.

[0039] The solvent mixture used in the present invention contains less than 10% by weight of water, preferably less than 5% by weight of water, more preferably less than 3% by weight of water, still more preferably less than 2% by weight of water, and still more preferably less than 1% by weight of water. Due to the low water content, undesirable hydrolysis of zirconium carboxylate in the metal precursor solution is prevented.

[0040] The total metal content of zirconium in the metal precursor solution is preferably 1% to 30% by weight, more preferably 2% to 20% by weight, and still more preferably 3% to 15% by weight. "Total metal content" means the total weight ratio of all zirconium contained in the metal precursor in the solution used.

[0041] The solvent mixture used in the method of the present invention may further contain a chelating agent, that is, a compound capable of forming two or more coordination bonds with metal ions. Examples of such chelating agents include diamines such as ethylenediamine and ethylenediaminetetraacetic acid (EDTA), and 1,3-dicarbonyl compounds such as acetylacetone and alkyl acetylacetate. Most preferably, acetylacetone is used as such a chelating agent.

[0042] In the presence of such a chelating agent, it was observed that the zirconium compound had improved solubility and no precipitation occurred even after a relatively long storage period.

[0043] In the method of the present invention, by using a special combination of a metal precursor, a phosphorus source, and a solvent, good solubility of all precursors is ensured, and the desired particle properties of the resulting zirconium phosphate (such as small particle size, high BET surface area, and low tapping density, etc.) are achieved. The method of the present invention can further include a heat treatment step of the zirconium phosphate produced by flame spray pyrolysis. This further heat treatment is preferably carried out at a temperature of 200 °C to 1200 °C, more preferably 250 °C to 1100 °C, and even more preferably 350 °C to 900 °C. By the heat treatment according to the method of the present invention, heat-treated zirconium phosphate having desired properties, particularly a desired crystal structure, is obtained.

[0044] The method of the present invention can include a step of further grinding the heat-treated zirconium phosphate, preferably a step of grinding with a ball mill. Ball mill grinding is preferably carried out in a suitable solvent such as ethanol or isopropanol, for example, by ZrO2 balls with a diameter of about 0.5 mm.

[0045] Use of zirconium phosphate in a lithium-ion battery The present invention further provides the use of the zirconium phosphate of the present invention in a lithium-ion battery, particularly as a component of a solid electrolyte of a lithium-ion battery, as an additive to a liquid or gel electrolyte, or as a component of an electrode of a lithium-ion battery.

[0046] The present invention further provides a lithium-ion battery comprising the zirconium phosphate of the present invention or zirconium phosphate obtained by the method of the present invention.

[0047] The lithium-ion battery of the present invention can include an active positive electrode (cathode), an anode, a separator, and an electrolyte containing a lithium-containing compound.

[0048] The positive electrode (cathode) of a lithium-ion battery typically includes a current collector and an active cathode material layer formed on the current collector.

[0049] The current collector can be aluminum foil, copper foil, nickel foil, stainless steel foil, titanium foil, a polymer substrate coated with a conductive metal, or a combination thereof.

[0050] The active cathode material includes materials that can reversibly insert / extract lithium ions and are well known in the art. Such active cathode materials can include transition metal oxides, for example, mixed oxides containing Ni, Co, Mn, V or other transition metals and, optionally, lithium. Preferred mixed lithium transition metal oxides used as active cathode materials are selected from the group consisting of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium nickel manganese cobalt oxide (NMC), lithium nickel cobalt aluminum oxide, lithium nickel manganese oxide, lithium iron phosphate, lithium manganese oxide, or mixtures thereof.

[0051] The anode of a lithium-ion battery can include any suitable material commonly used in lithium-ion secondary batteries that can reversibly insert / extract lithium ions. Typical examples include crystalline carbon such as plate-like, flake-like, spherical or fibrous natural or artificial graphite; amorphous carbon such as soft carbon, hard carbon, mesophase pitch carbide, calcined coke, or carbonaceous materials including mixtures thereof. Additionally, lithium metal, a lithium layer, or a conversion material (e.g., Si or Sn) can be used as the anode active material.

[0052] The present invention further provides an electrode such as a cathode or an anode for a lithium-ion battery containing zirconium phosphate of the present invention. Specifically, the zirconium phosphate of the present invention can be a dopant or a coating material for the electrode.

[0053] During the thorough experimental process, surprisingly, it was found that zirconium phosphate produced by the thermal decomposition method can be successfully used as a coating for mixed lithium transition metal oxides applicable as cathodes of lithium batteries.

[0054] The present invention thus provides a method for producing a coated mixed lithium transition metal oxide by subjecting a mixed lithium transition metal oxide and zirconium phosphate produced by the thermal decomposition method to dry mixing.

[0055] Dry mixing Dry mixing is understood to mean that no liquid is added or used during the mixing process, that is, for example, a plurality of substantially dry powders are mixed together. However, there may be trace amounts of moisture or liquids other than water in the mixing raw materials, or the mixing raw materials may contain water of crystallization. The dry mixing process of the present invention has several advantages compared to a mixing process including wet coating, for example, coating with a dispersion containing a metal oxide. In such a wet coating process, a solvent is necessarily used, and it is necessary to evaporate the solvent after the coating process is completed. Therefore, the dry coating process of the present invention is simpler and more economical than the wet coating process known from the prior art. On the other hand, it has been found that the dry coating process of the present invention also provides a better distribution of zirconium phosphate particles on the surface of an active material such as a mixed lithium transition metal oxide.

[0056] Dry mixing can be carried out, for example, in a mixing unit having a specific power of 0.05 to 1.5 kW per 1 kg of the mixing material. When the specific power used is less than 0.05 kW per 1 kg of the mixed anode material, the distribution of zirconium phosphate on the upper part of the active material particles becomes non-uniform, and there is a possibility that it will not firmly bond to the core material of the active material particles. When the specific power exceeds 1.5 kW per 1 kg of the mixed anode material, it will lead to a decrease in electrochemical properties. Furthermore, the coating becomes brittle and there is a risk of being easily damaged. The nominal power of the mixing unit can vary widely, for example, from 0.1 kW to 1000 kW. Therefore, a laboratory-scale mixing unit with a nominal power of 0.1 - 5 kW or a production-scale mixing unit with a nominal power of 10 - 1000 kW can be used. The nominal power is the maximum absolute power stated on the nameplate of the mixing unit. The volume of the mixing unit can vary widely. For example, the volume of the mixing unit can be in the range of 0.1 L to 2.5 m 3 It can be in the range of. For example, a laboratory-scale mixing unit can have a volume of 0.1 - 10 L, and a production-scale mixing unit can have a volume of 0.1 - 2.5 m 3 It can have a volume of. Preferably, in the method of the present invention, the forced-action mixer is used in the form of a powerful mixer equipped with high-speed mixing tools. It has been found that the best results are obtained when the speed of the mixing tools is 5 - 30 m / s, more preferably 10 - 25 m / s. Examples of commercially available mixing units suitable for the method of the present invention include Henschel mixers and Eirich mixers. The Eirich mixer can be, for example, a high-intensity Eirich mixer. The mixing time can vary. Preferably, it can be 0.1 - 120 minutes, more preferably 0.2 - 60 minutes, and most preferably 0.5 - 10 minutes.

[0057] After mixing, the mixture may be heat-treated to improve the bonding between the coating and the active material particles. However, this treatment is optional in the method of the present invention. This is because, in this method, the zirconium phosphate produced by the pyrolysis method and nanostructured adheres to the active material particles with sufficient strength. When the mixture is heat-treated, the temperature is typically in the range of 200 to 1000 °C and for a maximum of 48 hours. The heat treatment can be carried out in the presence of different types of gases such as nitrogen, oxygen, forming gas, etc. The present invention further provides an electrolyte for a lithium-ion battery containing the zirconium phosphate of the present invention.

[0058] The electrolyte of the lithium-ion battery can be in the form of a liquid, a gel, or a solid.

[0059] The liquid electrolyte of the lithium-ion battery can include all suitable organic solvents commonly used in lithium-ion batteries, such as anhydrous ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate, methyl ethyl carbonate, diethyl carbonate, γ-butyrolactone, dimethoxyethane, fluoroethylene carbonate, vinyl ethylene carbonate, or mixtures thereof.

[0060] The gel electrolyte contains a gelling polymer.

[0061] The solid electrolyte of the lithium-ion battery can include oxides, such as lithium metal oxides, sulfides, phosphates, or solid polymers.

[0062] Liquid or polymer gel electrolytes for lithium-ion batteries usually contain lithium salts. Examples of such lithium salts include lithium hexafluorophosphate (LiPF6), lithium bis(2-(trifluoromethylsulfonyl))imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), Li2SiF6, lithium triflate, LiN(SO2CF2CF3)2, lithium nitrate, lithium bis(oxalato)borate, lithium cyclo-difluoromethane-1,1-bis(sulfonyl)imide, lithium cyclo-hexafluoropropane-1,1-bis(sulfonyl)imide, and mixtures thereof.

[0063] Lithium-ion batteries, particularly lithium-ion batteries with liquid or gel electrolytes, can also include a separator that prevents direct contact between two electrodes that could lead to an internal short circuit.

[0064] The material of the separator can include polyolefin resins, fluorinated polyolefin resins, polyester resins, polyacrylonitrile resins, cellulose resins, non-woven fabrics, or mixtures thereof. Preferably, the material includes polyolefin resins such as polyethylene or polypropylene-based polymers, fluorinated resins such as polyvinylidene fluoride polymers or polytetrafluoroethylene, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyacrylonitrile resins, cellulose resins, non-woven fabrics, or mixtures thereof.

[0065] The lithium-ion battery of the present invention may include a liquid electrolyte, a gel electrolyte, or a solid electrolyte. A liquid mixture of a lithium salt and an organic solvent that is not cured, polymerized, or crosslinked is referred to as a "liquid electrolyte" in the present invention. A gel or solid mixture containing a cured, polymerized, or crosslinked compound or a mixture thereof, a solvent as necessary, and a lithium salt is referred to as a "gel electrolyte". Such a gel electrolyte can be produced by polymerization or crosslinking of a mixture containing at least one reactive, i.e., polymerizable or crosslinkable, compound and a lithium salt.

[0066] A special type of lithium-ion battery is a lithium polymer battery in which a polymer electrolyte is used instead of a liquid electrolyte. The electrolyte of a similar solid battery can also include other types of solid electrolytes such as sulfides, oxide solid electrolytes, or mixtures thereof.

[0067] The battery of the present invention can be a lithium metal battery such as a lithium-air, lithium-sulfur (Li-S), and other types of lithium metal batteries.

[0068] A lithium-air battery usually includes a porous carbon cathode and an organic, glass ceramic, or polymer ceramic type electrolyte. A lithium-sulfur (Li-S) battery usually includes iron disulfide (FeS2), iron sulfide (FeS), copper sulfide (CuS), lead sulfide, and copper sulfide (PbS+CuS) cathodes. There are also many other known types of lithium metal batteries. For example, lithium selenium (Li-Se), lithium manganese dioxide (Li-MnO2 or Li / Al-MnO2), lithium monofluoride (Li-(CF) x) Lithium thionyl chloride (Li-SOCl2), lithium sulfuryl chloride (Li-SO2Cl2), lithium sulfur dioxide (Li-SO2), lithium iodine (Li-I2), lithium silver chromate (Li-Ag2CrO4), lithium vanadium pentoxide (Li-V2O5 or Li / Al-V2O5), lithium copper chloride (Li-CuCl2), lithium copper (II) oxide (Li-CuO), lithium copper oxalate phosphate (Li-Cu4O(PO4)2), etc.

Brief Description of Drawings

[0069]

Figure 1

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Examples

[0070] Experimental Example 1 1337 g of a commercially available solution (Octa Solingen® Zirconium 18) containing 18.01 wt% Zr in the form of zirconium ethylhexanoate and 982 g of a commercially available solution (Alfa Aesar) containing 16.66 wt% P in the form of triethyl phosphate were mixed to obtain 2.97 kg of a solution. This solution corresponds to the composition of ZrP2O7. 1.25 kg / hour of this solution and 5 Nm of air3 The aerosol with time was generated by a two-component nozzle and sprayed into a tubular reaction with a combustion flame. The combustion gas of the flame was 4.3 Nm 3 / h of hydrogen and 25 Nm 3 / h of air. Furthermore, 15 Nm 3 / h of secondary air was used. After the reactor, the reaction gas was cooled and filtered. The BET surface area of the obtained white powder was 36 m 2 / g, and the tapped density was 65 g / L. The TEM image of the particles is shown in Fig. 1. XRD analysis (Fig. 2) showed that the main phase of the product was the cubic phase of zirconium phosphate. Fig. 3 shows the size distribution of the strong aggregates of this material after 30 minutes of ultrasonic treatment.

[0071] Experimental Example 2: Dry Coating of Zirconium Phosphate (ZPO) on CAM Using a high-intensity laboratory mixer (SOMAKON Mixer MP-GL equipped with a 0.5 L mixing unit), a commercially available NMC7 1.5 1.5 powder (PLB-H7 type, Linyi Gelon LIB Co.) with a BET surface area of 0.30 - 0.60 m 2 / g and a median diameter d50 = 10.6 ± 2 μm (by laser scattering) was first mixed with ZPO powder (from Experimental Example 1) in each amount (1.0 wt%) at 500 rpm for 1 minute to uniformly mix the two powders. Then, the mixing intensity was increased to 2000 rpm and processed for 5 minutes to dry coat the NMC particles with ZPO. The coated NMC particles were realized with a ZPO coating layer thickness of 20 - 200 nm. Fig. 4 is an SEM image of NMC dry-coated with ZPO. Comparing the backscattered electron image (a) of NMC dry-coated with fumed ZPO and the EDX mapping of Zr (b), it was found that the periphery of all cathode particles was completely and uniformly covered with ZPO. No large ZPO weak aggregates were detected, indicating the successful dispersion of nanostructured fumed ZPO. Furthermore, no unattached ZPO particles were seen adjacent to the cathode particles, indicating strong adhesion between the coating and the substrate. The high-resolution SEM image (c) showed a high surface coverage by CAM and the uniform distribution of ZPO.

[0072] Experimental Example 3: Electrochemical Test In an inert gas atmosphere, 90 wt% NMC, 5 wt% of PVDF (Solef PVDF 5130) as a binder, and 5 wt% of SUPER C65 (IMERYS) as a conductive additive were mixed to prepare an electrode for electrochemical measurement. As a solvent, N-methyl-2-pyrrolidone (NMP) was used. The slurry was cast on an aluminum foil and dried on a heating plate at 120 °C in air for 20 minutes. Then, the electrode plate was dried in a vacuum furnace at 120 °C for 2 hours. The cathode loading related to the area was adjusted to 2.0 ± 0.1 mAh cm -2 . A circular electrode with a diameter of 12 mm was punched out, calendared, and the electrode density was set to 3.0 g cm -3 . It was dried again in a vacuum furnace at 120 °C for 12 hours to remove all residual water and NMP. In the cycle test, the cell was assembled as a CR2032 coin cell (MTI Corporation) in an argon-filled glove box (GLOVEBOX SYSTEMTECHNIK GmbH). As the anode material, lithium metal (ROCKWOOD LITHIUM GmbH) was used. As the separator, Celgard 2500 was used. As the electrolyte, a 1 M LiPF6 solution (35 μL) in ethylene carbonate and ethyl methyl carbonate (50 wt%:50 wt%, SIGMA-ALDRICH) was used. The cell was fixed with a crimper (MTI). In the electrochemical evaluation, at 25 °C, constant current cycling was performed between 3.0 and 4.3 V with respect to Li + / Li. In the calculation of the capacity and specific current, only the mass of the active material was considered, and the theoretical capacity of NMC7 1.5 1.5 was assumed to be 180 mAh / g. In the case of the coin half-cell during cycling, the C rate was increased every 4 cycles from 0.1 / 0.1 (charge / discharge) to 0.2 / 0.2, 0.5 / 0.5, 1.0 / 1.0, and 1.0 / 2.0 C. Then, for the long-term stability test, the cell was cycled at 1 / 1 C. Figure 5 shows the influence of the obtained ZPO coating layer on the cycle performance. The performance of NMC coated with fumed ZPO was compared with that of uncoated NMC. From the graph data, it was intuitively found that the fumed ZPO coating significantly improved the performance and cycle life of NMC. The NMC coated with fumed ZPO had improved rate capability and long-term cycle stability.

[0073] Measurement of LiOH and Li2CO3 contents 2 g of the cathode material powder and 30 mL of deionized water were placed in a 100 mL titration beaker and stirred at room temperature for 10 minutes. The remaining solid was filtered, and the filter was rinsed with 20 mL of deionized water. All the liquid was collected in a 100 mL titration beaker. For the LiOH and Li2CO3 contents, tris (hydroxymethyl) aminomethane (TRIS) as a standard was used and measured by titration with hydrochloric acid (c(HCl) = 0.1 mol / L). Therefore, the beaker was placed on a manual titration stand (Excellence Titrator T7 (manufactured by Mettler Toledo) equipped with a 20 mL burette DV1020 and an electrode DGi111-SC), and titration was started. In the case of the material of Experimental Example 1, 0.05 wt% of LiOH and 0.265 wt% of Li2CO3 were detected by titration. For comparison, in uncoated NMC, 0.168 wt% of LiOH and 0.511 wt% of Li2CO3 were detected by titration.

[0074] As can be seen from the experimental examples, zirconium phosphate (ZPO) of the present invention is suitable for advantageous use as a component of an electrode. In addition to improving performance and cycle life, the material of the present invention can reduce the LiOH / Li2CO3 content, indicating that the lithium ion removal ability of the zirconium phosphate of the present invention is outstanding.

Claims

1. This is a form of strongly aggregated primary particles, The BET surface area (DIN 9277:2014) is 5 m². ２ / g to 100m ２ / g, The numerically average particle size d50 measured by static light scattering (SLS) is 0.03 μm to 2 μm, and the tamping density (DIN ISO 787-11:1995) is 20 g / L to 200 g / L. Zirconium phosphate produced by the thermal decomposition method of the general formula ZrP2O7.

2. A method for producing zirconium phosphate according to claim 1 by flame spray pyrolysis, - At least one zirconium compound selected from carboxylates, each of which zirconium carboxylates has 5 to 20 carbon atoms. -Organophosphates, - A solvent containing less than 10% by weight of water A method of applying flame spray pyrolysis to a solution containing [a substance].

3. The method according to claim 2, wherein the zirconium carboxylate is a carboxylate selected from the group consisting of linear, branched, or cyclic zirconium pentanoates (C5), hexanoates (C6), heptanoates (C7), octanoates (C8), nonanoates (C9), decanoates (D10), undecanoates (C11), dodecanoates (C12), tridecanoates (C13), tetradecanoates (C14), pentadecanoates (C15), hexadecanoates (C16), heptadecanoates (C17), octadecanoates (C18), nonadecanoates (C19), eicosanoates (C20), and mixtures thereof.

4. where the organic phosphoric acid is selected from phosphonic acid (H ３ PO ３ ), orthophosphoric acid (H ３ PO ４ ), metaphosphoric acid (HPO ３ ), pyrophosphoric acid (H ４ P ２ O ７ ), esters of polyphosphoric acid, and mixtures thereof, the method according to claim 2.

5. The method according to claim 2, wherein the organic phosphoric acid is selected from alkyl esters, aryl esters, alkyl / aryl mixed esters, and mixtures thereof.

6. The method according to claim 2, wherein the organic phosphoric acid is an alkyl ester having an alkyl group having 1 to 10 carbon atoms.

7. The method according to claim 2, wherein the solvent is selected from the group consisting of linear or cyclic saturated or unsaturated aliphatic or aromatic hydrocarbons, carboxylic acid esters, ethers, alcohols, carboxylic acids, and mixtures thereof.

8. The method according to claim 2, wherein the zirconium phosphate produced by flame spray pyrolysis is further heat-treated at a temperature of 600°C to 1300°C.

9. The method according to claim 8, wherein the heat-treated zirconium phosphate is pulverized.

10. Use of zirconium phosphate according to claim 1 as a component of a solid electrolyte, as an additive in a liquid or gel electrolyte, or as a component of an electrode in a lithium-ion battery.

11. An electrode for a lithium-ion battery containing zirconium phosphate as described in claim 1.

12. An electrolyte for a lithium-ion battery containing zirconium phosphate as described in claim 1.

13. A lithium-ion battery containing zirconium phosphate as described in claim 1.

14. A lithium-ion battery according to claim 13, comprising a liquid or gel electrolyte.

15. A lithium-ion battery according to claim 14, which is a solid-state battery.

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