Synthesis of nanostructured lithium zirconium phosphate

Abstract

The invention relates to a process for the production of lithium zirconium phosphate by means of flame spray pyrolysis using as precursors lithium and zirconium carboxylates containing 5 to 20 carbon atoms, organic phosphates and a solvent containing less than 10 wt.-% water. The lithium zirconium phosphate obtained by this process can be used in lithium ion batteries.

Description

Technical Field

[0001] This invention relates to a method for producing lithium zirconium phosphate by means of flame spray pyrolysis, the lithium zirconium phosphate obtained by the method, and its use in lithium-ion batteries. Background Technology

[0002] Rechargeable lithium-ion batteries are one of the most important types of batteries currently in use. A typical rechargeable lithium-ion battery consists of: an anode made of carbon material or a lithium-metal alloy, a cathode made of lithium-metal oxide, an electrolyte (in which lithium salts are dissolved in an organic solvent), and a separator (which provides lithium-ion channels between the positive and negative electrodes during charging and discharging).

[0003] In the pursuit of developing secondary batteries with improved intrinsic safety and energy density, considerable progress has recently been made in using solid-state electrolytes instead of liquid electrolytes. Among such systems, secondary lithium-ion batteries with electrodes made of lithium metal or lithium metal alloys are believed to offer high energy density and are particularly suitable. Such all-solid-state secondary lithium-ion batteries should possess good ionic conductivity at the interface between the electrode active material and the electrolyte to achieve the desired loading characteristics. This high ionic conductivity can be achieved by coating the surface of the active electrode material with lithium-containing compounds such as LiTi2(PO4)3, as described in JP 4982866 B2.

[0004] H. Xiea et al. described the preparation of Li by solid-state reaction of ZrO2 with Li2CO3, NH4H2PO4 and CaCO3 in Journal of Power Sources 2011, vol. 196, pp. 7760–7762. 1.2 Zr 1.9 Ca 0.1 (PO4)3. The Li-ion conductivity of this lithium zirconium phosphate was found to be similar to that of Li-ion batteries used as solid Li-ion separators in experimental Li-ion batteries. 1.3 Ti 1.7 Al 0.3 The Li ion conductivity of (PO4)3 is comparable.

[0005] Therefore, lithium zirconium phosphate is a promising candidate for Li-ion conducting materials used in lithium-ion batteries, especially in all-solid-state batteries.

[0006] Y. Li et al. described the preparation of orthorhombic LiZr2(PO4)3 by solid-state reaction of (NH4)2HPO4 with Li2CO3 and zirconium acetate, and its use as a solid electrolyte for all-solid-state Li / LiFePO4 lithium-ion batteries in PNAS, 2016, vol. 113 (47), pp. 13313–13317.

[0007] I. Hanghofer et al., in Dalton Trans., 2019, vol. 48, pp. 9376–9387, described the preparation of orthorhombic Ca-stabilized Li₂ via an all-solid-state reaction of Li₂CO₃, (NH₄)₂HPO₄, and CaCO₃ with either ZrO₂ or zirconium acetate. 1.4 Ca 0.2 Zr 1.8 (PO4)3 is suitable as a solid electrolyte for use in all-solid-state lithium-ion batteries.

[0008] Lithium zirconium phosphate prepared by solid-state synthesis typically has relatively high material density and low BET surface area, making it ideal for use as a core material in solid-state electrolytes for lithium-ion batteries.

[0009] However, if such compounds are to be used as additives that can be well distributed in or on the surface of the core material, smaller particle size, lower material density, and higher BET surface area are essential. Summary of the Invention

[0010] Problems and Solutions The problem solved by the present invention is to provide an improved method for industrially manufacturing crystalline lithium zirconium phosphate that can be used in lithium-ion batteries, particularly as a coating or doping material for electrodes (especially anodes) in lithium-ion batteries, and as an additive for electrolytes in lithium-ion batteries.

[0011] Specifically, the method should provide lithium zirconium phosphate particles with relatively small particle size, high BET surface area, and low compaction density.

[0012] Spray pyrolysis is a known method for producing various metal oxides and specific metal salts.

[0013] In spray pyrolysis, metal compounds in the form of fine droplets are introduced into a high-temperature zone, where they are oxidized and / or hydrolyzed to produce the corresponding metal oxides or salts. A particular form of this method is flame spray pyrolysis, in which droplets are supplied to a flame formed by igniting fuel gas and oxygen-containing gas.

[0014] US 2013 / 0316233 A1 generally discloses a method for producing a granular mixture suitable for use as an active cathode material in lithium-ion batteries. The method involves supplying an aerosol formed from a solution containing a lithium source, a transition metal source, and a phosphorus source, along with a combustion-supporting gas and a combustible gas, into a flame. The transition metal can be selected from Fe, Mn, Ti, Cr, V, Ni, Co, Cu, Zn, Al, Ge, Zr, Mo, and W; the phosphorus source can be selected from phosphoric acid, ammonium phosphate, sodium phosphate, and ferrous phosphate. Specific examples of this patent application only show the preparation of lithium iron phosphate. The synthesis of lithium zirconium phosphate is not disclosed in US 2013 / 0316233 A1. Based on the general disclosure of US 2013 / 0316233 A1, successful synthesis of this compound would require painstaking selection of suitable lithium sources, metal sources, phosphorus sources, solvents, and method conditions. Even then, it is unclear whether lithium zirconium phosphate with a high BET surface area and low material density can actually be obtained by this method.

[0015] During comprehensive experiments, it was surprisingly discovered that lithium-zirconium mixed phosphates with the desired particle properties could indeed be directly prepared using a flame spray pyrolysis method. However, the specific combination of metal and phosphorus precursors with solvents used in the method of this invention has proven crucial for obtaining particles with the properties required according to the invention.

[0016] Lithium zirconium phosphate This invention provides a general formula Li a Zr b M c (PO4) d Lithium zirconium phosphate, wherein M is at least one metal other than Li and Zr. 0.5 ≤ a ≤ 5.0, 0.5 ≤ b ≤ 5.0, 0 ≤ c ≤ 5, 1 ≤ d ≤ 5 Characterized by the lithium zirconium phosphate - It exists in the form of aggregated primary particles. - With 5 m 2 / g -100 m 2 / g BET surface area. - d 50 = 0.03 µm - 2 µm, the numerical average particle size was determined by static light scattering (SLS), and - Compacted density of 20 g / L - 200 g / L.

[0017] The lithium zirconium phosphate of the present invention can be obtained by the method of the present invention described below.

[0018] In the present invention, lithium zirconium phosphate of the general formula Li a Zrb M c (PO4) d In this context, M can be one or more elements selected from the group consisting of Na, K, Be, Mg, Ca, Sr, Ba, Zn, Co, Ni, Cu, Mn, B, Al, Ga, In, Fe, Sc, Y, La, Ti, Zr, Hf, Ce, Si, Ge, Sn, Pb, V, Nb, Ta, Mo, and W. Preferably, M = Ca.

[0019] The composition of lithium zirconium phosphate of the present invention preferably corresponds to the formula Li 0.8-1.5 Zr 1.5-2.5 M 0-0.5 (PO4) 2.5-3.5 Li, more preferably 1.0-1.3 Zr 1.8-2.2 M 0-0.3 (PO4) 2.8-3.2 .

[0020] The lithium zirconium phosphate of the present invention has 5 m 2 / g -100 m 2 / g, preferably 7 m 2 / g - 80 m 2 / g, more preferably 15-60 m 2 / g BET surface area.

[0021] BET surface area can be determined according to DIN 9277:2014 by nitrogen adsorption according to the Brunauer-Emmett-Teller method.

[0022] The lithium zirconium phosphate of the present invention is in the form of aggregated primary particles having a numerical average diameter of primary particles typically 1 to 100 nm, preferably 3 to 70 nm, and more preferably 5 to 50 nm, as determined by transmission electron microscopy (TEM). This numerical average diameter can be determined by calculating the average size of at least 500 particles analyzed by TEM.

[0023] Number average particle size d of lithium zirconium phosphate in aggregated and optionally agglomerated forms 50 The particle size is approximately 0.03 µm – 2 µm, more preferably 0.04 µm – 1 µm, and even more preferably 0.05 µm – 0.5 µm, as determined by static light scattering (SLS) after ultrasonic treatment of a mixture consisting of 5 wt% of the particles and 95 wt% of an aqueous solution of 0.5 g / L sodium pyrophosphate at 25 °C for 300 seconds.

[0024] Aggregates and partial aggregates can be broken down, for example, by grinding or ultrasonic treatment of the particles to produce particles with smaller particle size and narrower particle size distribution.

[0025] The lithium zirconium phosphate according to the present invention has a compacted density of 20 g / L–200 g / L, preferably 25 g / L–150 g / L, even more preferably 30 g / L–100 g / L, and still more preferably 40 g / L–80 g / L.

[0026] The compacted density of powdery or coarse-grained materials can be determined according to DIN ISO 787-11:1995 "General methods of test for pigments and extenders -- Part 11: Determination of tamped volume and apparent density after tamping". This involves measuring the apparent density of the bed after mixing and compaction.

[0027] Methods for producing lithium zirconium phosphate The present invention further provides a method for producing lithium zirconium phosphate of the present invention by means of flame spray pyrolysis, wherein... At least one metal precursor solution is subjected to flame spray pyrolysis, the metal precursor solution comprising - Lithium carboxylate and zirconium carboxylate, wherein each of these metal carboxylates contains 5 to 20 carbon atoms. - Organic phosphate esters, - Solvents containing less than 10% by weight of water.

[0028] During the flame spray pyrolysis method of the present invention, a solution of a metal compound (metal precursor) and a phosphorus source in the form of droplets is typically directed into a flame formed by igniting fuel gas and oxygen-containing gas, wherein the metal precursor used is oxidized and / or hydrolyzed together with the phosphorus source to produce the corresponding lithium zirconium phosphate.

[0029] The reaction initially forms highly dispersed, nearly spherical primary particles, which aggregate to form aggregates during further reaction. These aggregates can then coalesce into clusters. Unlike clusters, which can generally be relatively easily separated into aggregates by the introduction of energy, these clusters are further broken down (if any) only by the introduction of strong energy.

[0030] The resulting aggregated compound can be referred to as "fumed" or "pyrolytically generated" lithium zirconium phosphate.

[0031] The flame spray pyrolysis method is generally described in WO 2015173114 A1 and other literature.

[0032] The flame spray pyrolysis method of the present invention preferably includes the following steps: a) Atomizing the metal precursor solution with atomizing gas to provide an aerosol. b) In the reaction space of the reactor, the aerosol is reacted with a flame obtained by igniting a mixture of fuel gas and oxygen-containing gas to obtain a reaction stream. c) Cool the reaction stream, and d) The solid lithium zirconium phosphate was then removed from the reaction stream.

[0033] Examples of fuel gases are hydrogen, methane, ethane, natural gas, and / or carbon monoxide. Hydrogen is particularly preferred. Fuel gases are especially used in embodiments where the high crystallinity of the lithium zirconium phosphate to be produced is desired.

[0034] Oxygen-containing gas is typically air or oxygen-enriched air. Oxygen-containing gas is particularly used in embodiments where, for example, the high BET surface area of ​​lithium zirconium phosphate is desired. The total amount of oxygen is typically chosen to be at least sufficient to completely convert the fuel gas and metal precursor.

[0035] To obtain an aerosol, the vaporized solution containing the metal precursor can be mixed with an atomizing gas such as nitrogen, air, and / or other gases. The resulting aerosol droplets preferably have an average droplet size of 1-120 µm, particularly preferably 30-100 µm. These droplets are typically generated using single-material or multi-material nozzles. To increase the solubility of the metal precursor and obtain a suitable viscosity for solution atomization, the solution can be heated.

[0036] The metal precursors used in the method of the present invention include at least one lithium carboxylate and at least one zirconium carboxylate, each containing 5 to 20 carbon atoms.

[0037] Lithium carboxylate and zirconium carboxylate used in the method according to the invention may be, independently of each other, straight-chain, branched or cyclic lithium and / or zirconium valerate (C5), hexanoate (C6), heptanoate (C7), octanoate (C8), nonanoate (C9), decanoate (D10), undecanoate (C11), dodecanoate (C12), tridecanoate (C13), tetradecanoate (C14), pentadecanoate (C15), hexadecanoate (C16), heptadecanate (C17), octadecanoate (C18), nonadecanate (C19), icosanoate (C20), and mixtures thereof.

[0038] Most preferably, 2-ethylhexanoate (C8) zirconium and neodecanoate (C10) lithium are used.

[0039] The metal precursors used may contain carboxylates or other salts other than lithium and zirconium metals.

[0040] Besides those compounds of lithium and zirconium, metal precursors can also be inorganic metal compounds, such as nitrates, carbonates, chlorides, bromides, or other organometallic compounds, such as alkoxides, for example, ethanol, n-propoxide, isopropoxide, n-butoxide and / or tert-butoxide.

[0041] In the context of this invention, the term "organophosphate" refers to any compound having at least one group (R) (containing at least one carbon atom bonded via an oxygen atom to a phosphorus atom of unit P (=O)), such as compounds of the general formula (RO)3P (=O) or (RO)(P (=O))2, wherein R is a group containing at least one carbon atom, such as methyl or ethyl.

[0042] The organophosphate esters used in the method of the present invention are preferably selected from esters of phosphonic acid (H3PO3), esters of orthophosphoric acid (H3PO4), esters of metaphosphoric acid (HPO3), esters of pyrophosphoric acid (H4P2O7), esters of polyphosphoric acid, and mixtures thereof.

[0043] Organophosphates can be selected from alkyl esters, such as methyl ester, ethyl ester, propyl ester, butyl ester, hexyl ester, aryl esters such as phenyl ester, mixed alkyl / aryl esters and mixtures thereof.

[0044] The organophosphate ester is preferably an ester having a group containing 1 to 10 carbon atoms (most preferably an alkyl group containing 1 to 10 carbon atoms).

[0045] The use of organophosphates as phosphorus sources has unexpectedly proven crucial for obtaining lithium zirconium phosphate particles with high BET surface area and low compaction density.

[0046] The solvent mixture used in the method of the present invention can be selected from the group consisting of straight-chain or cyclic, saturated or unsaturated aliphatic or aromatic hydrocarbons, esters of carboxylic acids, ethers, alcohols, carboxylic acids and mixtures thereof.

[0047] The solvent mixture used in this 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, even more preferably less than 2% by weight of water, and even more preferably less than 1% by weight of water.

[0048] The low water content prevented the undesirable hydrolysis of zirconium carboxylate in the metal precursor solution.

[0049] The total metal content in the metal precursor solution is preferably 1%-30% by weight, more preferably 2%-20% by weight, and even more preferably 3%-15% by weight. "Total metal content" is understood as the total weight percentage of all metals contained in the metal precursor in the metal precursor solution used.

[0050] The solvent mixture used in the method of the present invention may additionally contain a chelating agent, i.e., a compound capable of forming two or more coordination bonds with metal ions. Examples of such chelating agents are, for example, diamines (such as ethylenediamine, ethylenediaminetetraacetic acid (EDTA)) and 1,3-dicarbonyl compounds (such as acetylacetone and alkyl acetoacetate). Most preferably, acetylacetone is used as such a chelating agent.

[0051] It was observed that in the presence of this chelating agent, some metal precursors, such as zirconium compounds, exhibited better solubility and did not precipitate after relatively long storage times.

[0052] The use of a special combination of metal precursors, phosphorus sources, and solvents in the method of this invention allows for ensuring good solubility of all precursors and achieving the desired particle properties of the resulting lithium zirconium phosphate, such as small particle size, high BET surface area, and low compaction density.

[0053] The method of the present invention may further include a heat treatment step of lithium zirconium phosphate produced by flame spray pyrolysis.

[0054] The further heat treatment is preferably carried out at a temperature of 600℃–1300℃, more preferably 650℃–1250℃, even more preferably 700℃–1200℃, and still more preferably 750℃–1150℃.

[0055] The heat treatment according to the method of the present invention allows for the acquisition of heat-treated lithium zirconium phosphate with desired properties, especially desired crystal structure.

[0056] The method of the present invention may include a further step of milling, preferably ball milling, of heat-treated lithium zirconium phosphate.

[0057] Ball milling is preferably carried out using ZrO2 balls (e.g., with a diameter of about 0.5 mm) in a suitable solvent such as ethanol or isopropanol.

[0058] Applications of lithium zirconium phosphate in lithium-ion batteries The present invention further provides the use of lithium zirconium phosphate according to the present invention in lithium-ion batteries, particularly as a component of the solid electrolyte of lithium-ion batteries, as an additive in the liquid electrolyte or gel electrolyte of lithium-ion batteries, or as a component of the electrode of lithium-ion batteries.

[0059] The present invention further provides a lithium-ion battery comprising lithium zirconium phosphate according to the present invention or lithium zirconium phosphate obtainable by the method of the present invention.

[0060] The lithium-ion battery of the present invention may contain an active positive electrode (cathode), an anode, a separator, and an electrolyte containing a lithium-containing compound.

[0061] 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.

[0062] 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.

[0063] The active cathode material may include materials capable of reversibly inserting / deintercalating lithium ions and is well known in the art. Such active cathode materials may include transition metal oxides such as mixed oxides comprising 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 oxides, lithium-manganese oxides, lithium-nickel-cobalt oxides, lithium-nickel-manganese-cobalt oxides, lithium-nickel-cobalt-aluminum oxides, lithium-nickel-manganese oxides, lithium iron phosphate, lithium manganese oxides, or mixtures thereof.

[0064] The anode of this lithium-ion battery can be any suitable material commonly used in rechargeable lithium-ion batteries that is capable of reversibly inserting / deintercalating lithium ions. Typical examples are carbon-containing materials, including crystalline carbon such as natural or artificial graphite in the form of flakes, sheets, spheres, or fibers; and amorphous carbon such as soft carbon, hard carbon, mesophase pitch carbides, coke, and the like, or mixtures thereof. Alternatively, lithium metal, lithium layers, or conversion materials (such as Si or Sn) can be used as the anode active material.

[0065] The present invention further provides electrodes, such as cathodes or anodes, comprising the lithium zirconium phosphate of the present invention for use in lithium-ion batteries. Specifically, the lithium zirconium phosphate of the present invention can be a dopant or coating material for the electrode.

[0066] The present invention further provides an electrolyte for lithium-ion batteries, comprising lithium zirconium phosphate of the present invention.

[0067] The electrolyte in a lithium-ion battery can be in liquid, gel, or solid form.

[0068] The liquid electrolyte of a lithium-ion battery may contain any suitable organic solvent commonly used in lithium-ion batteries, such as anhydrous ethylene carbonate (EC), dimethyl carbonate (DMC), 1,2-propylene carbonate, methyl ethyl carbonate, diethyl carbonate, γ-butyrolactone, dimethoxyethane, fluoroethylene carbonate, vinyl ethylene carbonate, or mixtures thereof.

[0069] The gel electrolyte comprises a gelled polymer.

[0070] The solid electrolyte of this lithium-ion battery may contain oxides (such as lithium metal oxides), sulfides, phosphates, or solid polymers.

[0071] The liquid or polymer gel electrolyte of this lithium-ion battery typically contains a lithium salt. Examples of such lithium salts include lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), Li2SiF6, lithium trifluoromethanesulfonate, LiN(SO2CF2CF3)2, lithium nitrate, lithium bis(oxalate)borate, lithium cyclo-difluoromethane-1,1-bis(sulfonyl)imide, lithium cyclo-hexafluoropropane-1,1-bis(sulfonyl)imide, and mixtures thereof.

[0072] The lithium-ion battery (especially lithium-ion batteries with liquid electrolyte or gel electrolyte) may also include a separator that prevents direct contact between the two electrodes (which would cause an internal short circuit).

[0073] The diaphragm material may comprise polyolefin resins, fluorinated polyolefin resins, polyester resins, polyacrylonitrile resins, cellulose resins, nonwoven fabrics, or mixtures thereof. Preferably, the material comprises polyolefin resins such as polyethylene or polypropylene resins, fluorinated resins such as polyvinylidene fluoride polymers or polytetrafluoroethylene, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyacrylonitrile resins, cellulose resins, nonwoven fabrics, or mixtures thereof.

[0074] The lithium-ion battery according to the present invention may comprise a liquid electrolyte, a gel electrolyte, or a solid electrolyte. In the context of this invention, a liquid mixture of a lithium salt and an organic solvent that has not been cured, polymerized, or crosslinked is referred to as a "liquid electrolyte." A gel or solid mixture comprising a cured, polymerized, or crosslinked compound or a mixture thereof, optionally a solvent, and a lithium salt is referred to as a "gel electrolyte." Such a gel electrolyte can be prepared by polymerization or crosslinking of a mixture containing at least one reactive (i.e., polymerizable or crosslinkable) compound and a lithium salt.

[0075] A special type of lithium-ion battery is the lithium polymer battery, in which a polymer electrolyte is used instead of a liquid electrolyte. Similarly, the electrolyte in solid-state batteries may also contain other types of solid electrolytes such as sulfide, oxide solid electrolytes, or mixtures thereof.

[0076] The battery of the present invention can be a lithium metal battery such as Li-air, lithium-sulfur (Li-S), and other types of lithium metal batteries.

[0077] Li-air batteries typically contain a porous carbon cathode and an electrolyte of the organic, glass-ceramic, or polymer-ceramic type.

[0078] Li-sulfur (Li-S) batteries typically contain iron disulfide (FeS2), iron sulfide (FeS), copper sulfide (CuS), lead sulfide, and copper sulfide (PbS+CuS) cathodes.

[0079] Many other known types of lithium metal batteries also exist, such as lithium-selenium (Li-Se), lithium-manganese dioxide (Li-MnO2 or Li / Al-MnO2), and lithium-monofluoride (Li-(CF)). x Lithium-thionyl chloride (Li-SOCl2), lithium-thionyl 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 oxyphosphate (Li-Cu4O(PO4)2) and other types. Attached Figure Description

[0080] Figure 1 This is a TEM image of lithium zirconium phosphate particles prepared as described in Comparative Example 1.

[0081] Figure 2 This is a TEM image of lithium zirconium phosphate particles prepared as described in Comparative Example 2.

[0082] Figure 3 This is a TEM image of lithium zirconium phosphate particles prepared as described in Example 1.

[0083] Figure 4 The XRD patterns of lithium zirconium phosphate prepared as described in Examples 1-2 and Comparative Examples 1-2 are shown.

[0084] Figure 5 SEM images of NMC dry-coated with fumed lithium zirconium phosphate particles are shown (a - backscattered electron (BSE) image, b - EDX mapping of Zr, c - high-resolution SEM image).

[0085] Figure 6 The rate characteristics and cycle performance of uncoated NMC and NMC dry-coated with gaseous lithium zirconium phosphate particles are shown in a lithium-ion battery with a liquid electrolyte.

[0086] Figure 7 The charge and discharge curves are shown in a sulfide-based all-solid-state battery with Li6PS5Cl solid electrolyte, under the initial cycle at a discharge current of 0.066 mA (0.035C).

[0087] Figure 8The charge and discharge curves are shown in a sulfide-based all-solid-state battery with Li6PS5Cl solid electrolyte, at a discharge current of 1.4 mA (0.75C) for the fourth cycle. Detailed Implementation

[0088] Example Comparative Example 1 A 6.34 kg aqueous solution containing 157.8 g of LiNO3 (metal content: 4 wt%) and 1733 g of Zr(NO3)4 (metal content: 6 wt%) was prepared. Under vigorous stirring, 1190 g of H3PO4 (85 wt% in water) was added dropwise to the metal salt solution, resulting in the formation of a dispersion containing a white precipitate. The compound obtained thus corresponds to the formula LiZr2(PO4)3.

[0089] The dispersion was formed at a rate of 1.5 kg / h and 15 Nm through a two-component nozzle. 3 / h of air aerosol is sprayed into a tubular reaction vessel with a combustion flame. The combustion gases of this flame are 14.3 Nm 3 / h of hydrogen and 30 Nm 3 The air composition is / h. Additionally, 25 Nm is used. 3 / h of secondary air. After the reactor, the reaction gas is cooled and filtered.

[0090] The particle properties are shown in Table 1, and the TEM images of the particles are shown in Table 2. Figure 1 And XRD analysis ( Figure 4 The main phase of the product is cubic zirconium phosphate.

[0091] Comparative Example 2 A 6.34 kg ethanol solution containing 157.8 g of LiNO3 (metal content: 4 wt%) and 1733 g of Zr(NO3)4 (metal content: 6 wt%) was prepared. Under vigorous stirring, 1190 g of H3PO4 (85 wt% in water) was added dropwise to the metal salt solution, resulting in the formation of a dispersion containing a white precipitate. The compound obtained thus corresponds to the formula LiZr2(PO4)3.

[0092] The dispersion was formed at a rate of 1.5 kg / h and 15 Nm through a two-component nozzle. 3 / h of air aerosol is sprayed into a tubular reaction vessel with a combustion flame. The combustion gases of this flame are 8.4 Nm³. 3 / h of hydrogen and 30 Nm 3 The air composition is / h. Additionally, 25 Nm is used. 3 / h of secondary air. After the reactor, the reaction gas is cooled and filtered.

[0093] The particle properties are shown in Table 1, and the TEM images of the particles are shown in Table 2. Figure 2 And XRD analysis ( Figure 4 The main phase of the product is cubic zirconium phosphate.

[0094] Comparative Example 3 A 61.4 g solution was prepared by mixing 2.9 g of a commercial solution of lithium (Borchers® Deca Lithium 2) in the form of lithium neodecanoate dissolved in naphtha (2 wt%) and 50 g of a commercial solution of zirconium (Octa Solingen® Zirconium 12) in the form of zirconium ethylhexanoate dissolved in petroleum solvent (whitespirit). 8.6 g of H3PO4 (85 wt%) in water was added dropwise to this metal salt solution under vigorous stirring. Phase separation was observed, making it impossible to spray the solution uniformly. No spraying experiments were performed.

[0095] Example 1 A clear solution was obtained by mixing 23.75 kg of a solution containing 3370 g of a commercial solution of lithium in the form of lithium neodecanoate dissolved in naphtha (Borchers® Deca Lithium 2), 15 kg of a commercial solution of Zr in the form of zirconium ethylhexanoate dissolved in petroleum solvent oil (Octa Solingen® Zirconium 12), and 5384 g of a commercial solution of phosphorus in the form of triethyl phosphate (Alfa Aesar) containing 16.83 wt% of phosphorus. This solution corresponds to the composition of LiZr2(PO4)3.

[0096] The dispersion was formed at a rate of 1.5 kg / h and 15 Nm through a two-component nozzle. 3 / h of air aerosol is sprayed into a tubular reaction vessel with a combustion flame. The combustion gases of this flame are 8.5 Nm³. 3 / h of hydrogen and 30 Nm 3 The air composition is / h. Additionally, 25 Nm is used. 3 / h of secondary air. After the reactor, the reaction gas is cooled and filtered.

[0097] The particle properties are shown in Table 1, and the TEM images of the particles are shown in Table 2. Figure 3 And XRD analysis ( Figure 4 The main phase of the product is orthorhombic hexahedral lithium zirconium phosphate.

[0098] Example 2 A solution containing 6.18 kg of a commercial solution (containing 1056 g of a commercial solution of lithium in the form of lithium neodecanoate dissolved in naphtha (Borchers® Deca Lithium 2), 2453 g of a commercial solution of Zr in the form of zirconium ethylhexanoate dissolved in petroleum solvent oil (Octa Solingen® Zirconium 12), and 1408 g of a commercial solution of phosphorus in the form of triethyl phosphate (Alfa Aesar)) was mixed to obtain a clear solution. Another solution containing 60.8 g of Ca(NO3)2×4H2O, 1200 g of ethanol, and 1200 g of ethylhexanoic acid was added under continuous stirring until a clear solution was obtained. This solution corresponds to Li 1.2 Ca 0.1 Zr 1.9 The composition of (PO4)3.

[0099] The dispersion was formed at a rate of 1.5 kg / h and 15 Nm through a two-component nozzle. 3 / h of air aerosol is sprayed into a tubular reaction vessel with a combustion flame. The combustion gases of this flame are 8.7 Nm³. 3 / h of hydrogen and 30 Nm 3 The air composition is / h. Additionally, 25 Nm is used. 3 / h of secondary air. After the reactor, the reaction gas is cooled and filtered.

[0100] The particle properties are shown in Table 1, and XRD analysis ( Figure 4 The main phase of the product is orthorhombic hexahedral lithium zirconium phosphate.

[0101] The particle properties of the resulting products summarized in Table 1 show that the combination of the present invention, using only metal carboxylates and ethyl phosphates in anhydrous solutions, results in a relatively high BET surface area (17-44 m²). 2 / g relative to the comparative example 4.3-4.7m 2 Lithium zirconium phosphate has the following characteristics: small particle size (76-130 nm compared to approximately 4 μm in the comparative example) and low compaction density (approximately 50 g / L compared to approximately 300 g / L in the comparative example).

[0102] Table 1 Properties of Lithium Zirconium Phosphate

[0103] Analysis of lithium zirconium phosphate (LZP) coated with a mixture of lithium transition metal oxides by SEM-EDX In a high-intensity laboratory mixer (a SOMAKON MP-GL mixer with a 0.5 L mixing unit), NMC powder was first mixed with a corresponding amount (1.0 wt%) of fumed LZP powder from Example 1 at 500 rpm for 1 minute to homogenize the two powders. The mixing intensity was then increased to 2000 rpm for 5 minutes to achieve dry coating of NMC particles with LZP powder.

[0104] The thickness of the LZP coating on the NMC particles is approximately 15-200 nm.

[0105] Figure 5 SEM images of NMC dry-coated with LZP are shown. Figure 5 a, b, c: Vapor-phase LZP of Example 1. A comparison of the backscattered electron image (a) of the NMP dry-coated with vapor-phase LZP and the EDX mapping of Zr (b) reveals that all cathode particles are completely and uniformly covered by vapor-phase LZP. No large LZP agglomerates were detected, indicating good dispersion of nanostructured vapor-phase LZP particles. Furthermore, no free, unconnected LZP particles were found adjacent to the cathode particles, indicating strong adhesion between the coating and the substrate. The high-resolution SEM image (c) shows a uniform distribution of vapor-phase LZP with a high surface coverage of CAM.

[0106] Electrochemical tests of lithium-ion batteries with liquid electrolyte Electrodes for electrochemical measurements were prepared by blending 90 wt% NMC with 5 wt% PVDF (SolefPVDF 5130) as a binder and 5 wt% SUPER PLi (TIMCAL) as a conductive additive under an inert gas atmosphere. N-methyl-2-pyrrolidone was used as the solvent. The slurry was cast onto aluminum foil and dried in air at 120°C for 20 minutes on a hot plate. The electrode sheets were then dried in a vacuum furnace at 120°C for 2 hours. Circular electrodes with a diameter of 12 mm were stamped, rolled at 90 psi, and dried again in a vacuum furnace at 120°C for 12 hours to remove any residual water and NMP. For cycling tests, the cells were assembled into CR2032 button cells (MTI Corporation) in an argon-filled glove box (GLOVEBOX SYSTEMTECHNIK GmbH). Lithium metal (ROCKWOOD LITHIUM GmbH) was used as the anode material. Celgard 2500 was used as the separator. 25 μL of a 1M LiPF6 solution in ethylene carbonate and methyl ethyl carbonate (50:50 wt / wt; SIGMA-ALDRICH) was used as the electrolyte. The battery was locked with a crimper (MTI).

[0107] For electrochemical evaluation, constant current cycling was performed between 3.0 and 4.3 V. For capacity and specific current calculations, only the mass of the active material was considered. For the button half-cell during cycling, the C-rate was increased from 0.1 / 0.1 (charge / discharge) to 0.3 / 0.3, 0.5 / 0.5, 1.0 / 1.0, 1.0 / 2.0, and 1.0 / 4.0 C every four cycles. The cells were then cycled at 0.5 / 0.5 C for long-term stability testing.

[0108] Figure 6 The effect of the LZP coating on the cycle performance is shown. The performance of the NMC dry-coated with vapor-phase LZP from Example 1 is compared with that of the uncoated NMC as a reference. It is readily apparent from the figures shown that the dry-coated vapor-phase LZP coating significantly improves the stability and cycle life of the NMC. The NMC dry-coated with vapor-phase LZP exhibits higher discharge capacity in all cycles (initial rate test and long-term cycle test). A higher initial specific discharge capacity than the uncoated NMC is also shown at 0.1 C.

[0109] Electrochemical tests on sulfide-based all-solid-state lithium-ion batteries A powdered composite electrode was prepared by mixing active material NCM (AM), conductive carbon nanofibers (CNF), and solid electrolyte (Li6PS5Cl, SE) in an agate mortar at a mass ratio of 65:2:35. To fabricate a freestanding and flexible dry film, the prepared powder electrode was mixed with 0.3 wt% polytetrafluoroethylene (PTFE, a fine powder produced by emulsion polymerization; particle size 300–700 µm; softening point 320–330 °C; molecular weight 10) in the mortar at 100 °C. 7 -10 8 Mix (g / mol).

[0110] After 1 minute of mixing and shearing, a single sheet is formed. The sheet is placed on a hot plate and rolled to the desired thickness (approximately 100 μm). Each sample is prepared at least twice to confirm the reproducibility of the method. To prepare a separate electrolyte membrane, the solid electrolyte is mixed with 0.15 wt% PTFE and treated in the same manner as the cathode membrane.

[0111] Test cells were prepared to measure the basic properties of the cathode composite material, such as the charge / discharge potential curve and rated discharge capacity.

[0112] The battery was fabricated using a mold with a diameter of 13 mm. The test battery contained a stainless steel casing with Teflon insulation. For a typical battery, the electrolyte Li6PS5Cl powder was uniformly spread inside the mold using a micro-scraper. Next, the powder was temporarily compressed and compacted into pellets in one pass. The cathode composite powder was uniformly distributed on the compacted electrolyte surface within the mold. Then, the cathode layer was compressed. The lithium-indium alloy anode was placed and pressed against the opposite sides of the battery stack. All battery components were then compressed together and fully granulated using a hydraulic press (applied at 4 tons for 30 seconds): 300 MPa.

[0113] After compression, the battery stack is placed inside the steel casing, with screws maintaining electrical contact within the battery. The screws are then tightened using a preset torque of 3.0 Nm.

[0114] All the above methods are carried out in an argon-filled glove box (<0.1 ppm H2O and O2).

[0115] The battery's cycle and rate performance were measured using a CTS-Lab battery tester (BaSyTec, Germany). The standard rate performance test consisted of three different discharge currents ranging from 0.066 mA (0.035C) to 1.4 mA (0.75C), while the charge rate, including the CV step, remained constant at 0.14 mA (0.075C). The standard cut-off voltages used for this cycle test were set at 3.63 V for charging and 1.93 V for discharging.

[0116] Figure 7 The effect of different coating amounts of LZP (0.5 wt%, 1 wt%, and 2 wt%) on rate performance is shown at a discharge current of 0.066 mA (0.035 C) during the first cycle. The discharge capacity of the NMC dry-coated with vapor-phase LZP from Example 1 at 0.066 mA is compared with that of the uncoated NMC as a reference. It is readily apparent from the figures that no significant improvement in initial discharge capacity is observed in sulfide-based all-solid-state batteries at low discharge rates such as 0.035 C.

[0117] Figure 8The effect of different coating amounts of LZP (0.5 wt%, 1 wt%, and 2 wt%) on rate characteristics at a discharge current of 1.4 mA (0.75 C) during cycle 4 is shown. The discharge capacity of the NMC dry-coated with vapor-phase LZP from Example 1 at 0.75 C is compared with that of an uncoated NMC as a reference. It is readily apparent from the figures that the dry-coated vapor-phase LZP coating significantly improves the discharge rate characteristics of the NMC. In sulfide-based all-solid-state batteries, the NMC dry-coated with vapor-phase LZP exhibits higher discharge capacity at high discharge rates, such as 0.75 C.

Claims

1. General formula Li a Zr b M c (PO4) d lithium zirconium phosphate, Where M is at least one metal different from Li and Zr. 0.5 ≤ a ≤ 5.0, 0.5 ≤ b ≤ 5.0, 0 ≤ c ≤ 5, 1 ≤ d ≤ 5 Its features are, The lithium zirconium phosphate It exists in the form of aggregated primary particles, with a numerical average diameter of primary particles ranging from 1 to 100 nm. With 5 m 2 / g -100 m 2 / g BET surface area. d 50 = 0.03 µm - 2 µm, the numerical average particle size was determined by static light scattering (SLS), and Compacted density of 20 g / L - 200 g / L.

2. A method for preparing lithium zirconium phosphate according to claim 1 by means of flame spray pyrolysis. Its features At least one metal precursor solution is subjected to flame spray pyrolysis, the metal precursor solution comprising - Lithium carboxylate and zirconium carboxylate, wherein each of these metal carboxylates contains 5 to 20 carbon atoms. - Organic phosphate esters, - Solvents containing less than 10% by weight of water.

3. The method according to claim 2, Its features The flame spray pyrolysis includes the following steps: a) The metal precursor solution is atomized by means of an atomizing gas to provide an aerosol. b) In the reaction space of the reactor, the aerosol is reacted with a flame obtained by igniting a mixture of fuel gas and oxygen-containing gas to obtain a reaction stream. c) Cool the reaction stream, and d) The solid lithium zirconium phosphate is then removed from the reaction stream.

4. The method according to claim 2 or 3, Its features The lithium carboxylate and zirconium carboxylate are independently selected from the group consisting of lithium and / or zirconium carboxylates: straight-chain, branched or cyclic valerate (C5), hexanoate (C6), heptanoate (C7), octanoate (C8), nonanoate (C9), decanoate, undecanoate (C11), dodecanoate (C12), tridecanoate (C13), tetradecanoate (C14), pentadecanoate (C15), hexadecanoate (C16), heptadecanate (C17), octadecanoate (C18), nonadecanate (C19), icosanoate (C20), and mixtures thereof.

5. The method according to claim 2 or 3, Its features The organophosphate esters are selected from esters of phosphorous acid (H3PO3), esters of orthophosphoric acid (H3PO4), esters of metaphosphoric acid (HPO3), esters of pyrophosphoric acid (H4P2O7), esters of polyphosphoric acid, and mixtures thereof.

6. The method according to claim 2 or 3, Its features The organophosphate is selected from alkyl esters, aryl esters, mixed alkyl / aryl esters and mixtures thereof.

7. The method according to claim 2 or 3, Its features The organophosphate ester is an alkyl ester having an alkyl group having 1 to 10 carbon atoms.

8. The method according to claim 2 or 3, Its features The solvent is selected from the group consisting of straight-chain or cyclic, saturated or unsaturated aliphatic or aromatic hydrocarbons, esters of carboxylic acids, ethers, alcohols, carboxylic acids and mixtures thereof.

9. The method according to claim 2 or 3, Its features The metal precursor solution contains a chelating agent selected from the group consisting of diamines and 1,3-dicarbonyl compounds.

10. The method according to claim 2 or 3, Further, it includes heat treatment of the lithium zirconium phosphate produced by flame spray pyrolysis at a temperature of 600°C to 1300°C.

11. The method according to claim 10, Further includes milled and heat-treated lithium zirconium phosphate.

12. The use of lithium zirconium phosphate according to claim 1, wherein the lithium zirconium phosphate is used as a component of a solid electrolyte in a lithium-ion battery, as an additive in a liquid or gel electrolyte in a lithium-ion battery, or as a component of an electrode in a lithium-ion battery.

13. An electrode for a lithium-ion battery comprising lithium zirconium phosphate as claimed in claim 1.

14. An electrolyte for lithium-ion batteries comprising lithium zirconium phosphate as claimed in claim 1.

15. A lithium-ion battery comprising lithium zirconium phosphate according to claim 1.

16. The lithium-ion battery of claim 15, comprising a liquid or gel electrolyte.

17. The lithium-ion battery according to claim 15, wherein the battery is a solid-state battery.

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