Preparation method of oxyfluoride solid electrolyte and oxyfluoride solid electrolyte

Abstract

The invention relates to a preparation method of an oxyfluoride solid electrolyte and the oxyfluoride solid electrolyte. The preparation method comprises the following steps: putting a lithium source material, a lanthanum source material, a doped element-containing material, a pore-forming agent and a solvent into a grinding machine for grinding treatment to obtain mixed slurry; carrying out spray granulation on the mixed slurry to obtain initial particles; placing the initial particles in a fluidized bed reactor, sintering in an air atmosphere to remove the pore-forming agent and the residual solvent so as to obtain porous particles, switching the atmosphere into fluorine-containing gas, then sintering, enabling a fluorine-containing active body decomposed by the fluorine-containing gas to react with the porous particles, and naturally cooling to room temperature in an inert gas atmosphere, thereby obtaining the porous particles. And crushing the oxyfluoride solid electrolyte block to obtain the oxyfluoride solid electrolyte. The oxyfluoride solid electrolyte prepared by the preparation method provided by the invention has the characteristics of high density and high ionic conductivity, and can be widely applied to lithium batteries, especially all-solid-state lithium batteries.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid electrolyte materials, and particularly relates to a preparation method of a fluorine oxide solid electrolyte and the fluorine oxide solid electrolyte. BACKGROUND

[0002] Lithium ion batteries are widely used in many fields, and most of the lithium ion batteries use liquid organic electrolytes, while all-solid-state batteries using solid electrolytes have many advantages compared with liquid electrolytes, such as non-flammability, high safety, wide electrochemical window and good thermal stability, and are considered as key materials for next-generation battery technology. Among them, fluorine oxide solid electrolytes have attracted widespread attention due to their excellent ionic conductivity and electrochemical stability.

[0003] However, there are still some problems in the existing preparation technology of fluorine oxide solid electrolytes: on the one hand, in the preparation process of traditional solid electrolyte materials, although the high-temperature solid phase method is simple in process, it needs to be calcined at high temperature for a long time. The solid electrolyte particles prepared by the traditional method are coarse, high in hardness, complete in crystallization and low in sintering activity. In order to densify them, very high sintering temperature and long holding time are needed, which leads to the problems of impurity phase in the final product and excessive loss of volatile substances; on the other hand, the conventional sintering process is difficult to maintain the balance between high density of the material and low energy consumption of production, resulting in low ionic conductivity or high energy consumption in preparation. In addition, the preparation of fluorine oxide solid electrolyte in the prior art is relatively less studied, especially for the multi-element doped fluorine oxide solid electrolyte material, its preparation process has not been fully optimized, and it is difficult to achieve the goals of high density and high ionic conductivity at the same time.

[0004] Therefore, it is urgent to develop a fluorine oxide solid electrolyte material preparation method which can realize uniform mixing of raw materials, improve sintering efficiency, reduce production energy consumption, and at the same time improve the density and ionic conductivity of the material. SUMMARY

[0005] The present application aims at the defects in the prior art, and provides a preparation method of a fluorine oxide solid electrolyte and the fluorine oxide solid electrolyte.

[0006] The present application reduces the initial particle size of the raw materials by grinding and mixing non-fluorine source raw materials (referring to other raw materials for preparing fluorine oxide solid electrolyte except fluorine source materials) with pore-forming agents, thereby increasing the specific surface area of the raw materials, improving the activity of the raw materials, and further improving the mixing uniformity; then the slurry droplet surface is instantaneously dehydrated to form a gel shell by spray granulation, the mixing state of the raw materials is "frozen" in the microspheres to obtain initial microparticles, which provides conditions for subsequent preparation of a porous structure; the initial microparticles are placed in a boiling bed reactor for first-stage sintering to remove the pore-forming agents and residual solvents in the initial microparticles, and porous microparticles are obtained; the porous microparticles can provide a large reaction interface during the fluorination reaction of the second-stage sintering, so that the porous microparticles react with fluorine-containing gas in a solid-gas contact manner, the reaction uniformity is improved, the fluorine element can be uniformly doped into the crystal lattice, and the consistency of the composition and structure of the final product is improved; finally, the fluorination reaction product is crushed, and in the crushing process, the multiple connection points inside the porous structure of the fluorination reaction product are broken, obtaining fluorine oxide solid electrolyte crystal fragments that are non-porous, smaller in size (submicron level) but self-dense, and due to the existence of pores in the product after the fluorination reaction, the structure of the multiple internal point connections in the pores is broken during the crushing process, and better crushing effect can be obtained at lower energy consumption. The preparation method provided by the present application can be carried out at a lower temperature and for a shorter time, thereby reducing energy consumption and improving efficiency.

[0007] To achieve the above-mentioned object, in a first aspect, the present application provides a preparation method of a fluorine oxide solid electrolyte, the preparation method comprising.

[0008] According to the stoichiometric ratio of the chemical formula of the fluorine oxide solid electrolyte, a lithium source material, a lanthanum source material, and a material containing a doping element are weighed as raw materials, and are placed in a grinder together with a pore-forming agent and a solvent for grinding treatment to obtain a mixed slurry; wherein the material containing a doping element includes one or more of a material containing an M1 element, a material containing an M2 element, and a material containing an M3 element.

[0009] The mixed slurry is spray granulated to obtain initial microparticles.

[0010] The initial microparticles are placed in a boiling bed reactor, and first-stage sintering is carried out in an air atmosphere to remove the pore-forming agent and residual solvent, and porous microparticles are obtained; the porous microparticles are oxide precursor particles with a porous structure.

[0011] The atmosphere in the boiling bed reactor is switched to a fluorine-containing gas, and second-stage sintering is carried out, so that the fluorine-containing gas decomposes and / or the fluorine-containing active body of the fluorine-containing gas reacts with the porous microparticles inside the pores of the oxide precursor particles and on the surface; after sintering, heating is stopped, the atmosphere is switched to an inert gas atmosphere, and natural cooling to room temperature is carried out to obtain the fluorine oxide solid electrolyte.

[0012] Preferably, the lithium source material comprises one or more of lithium carbonate, lithium hydroxide, lithium oxalate, lithium acetate, lithium nitrate.

[0013] The lanthanum source material comprises one or more of lanthanum trioxide, lanthanum carbonate, lanthanum nitrate, lanthanum hydroxide, lanthanum fluoride.

[0014] The oxyfluoride solid electrolyte has a general chemical formula of Li x La y M1 a M2 b M3 c O6F, wherein x, y, a, b, c are the molar percentages of the corresponding elements, and 1 < x + 3y < 5, 0 < x ≤ 2, 1 / 3 < y < 5 / 3, 0 ≤ a ≤ 2, 0 ≤ b ≤ 2, 0 ≤ c ≤ 2, a + b + c = 2, M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation.

[0015] The pore-forming agent comprises one or more of polyethylene glycol, polyvinylpyrrolidone, starch, and polymethyl methacrylate; the mass of the pore-forming agent accounts for 1% to 20% of the total mass of the raw materials.

[0016] Preferably, the M1 element specifically comprises one or more of Zr, Ti, Hf, Si, Ge, and Sn.

[0017] The M2 element specifically comprises one or more of Nb, Sb, Bi, V, and Ta.

[0018] The M3 element specifically comprises one or more of W, Cr, Mo, and Mn.

[0019] Preferably, the solvent comprises one or more of deionized water, ethanol, NMP, isopropanol, and acetone.

[0020] The rotation speed of the grinding machine is set to 1000 rpm to 3000 rpm, and the grinding time is 1 hour to 6 hours.

[0021] The solid content of the mixed slurry is 10 wt% to 45 wt%.

[0022] Preferably, the spray granulation equipment is a spray dryer; the temperature of the feed inlet of the spray dryer is 180°C to 240°C, and the temperature of the discharge outlet is 60°C to 120°C.

[0023] Preferably, the flow rate of air in the fluidized bed reactor is 0.01 m / s to 1 m / s.

[0024] The first sintering process specifically includes: heating the fluidized bed reactor from room temperature to 300-500℃ at a heating rate of 1-8℃ / min, and keeping the temperature for 1-8 hours.

[0025] The porosity of the porous microparticles is 30-50%.

[0026] Preferably, the fluorine-containing gas includes one or more of nitrogen tetrafluoride, nitrogen trifluoride, hydrogen fluoride vapor, polytetrafluoroethylene, and ammonium fluoride; and the flow rate of the fluorine-containing gas in the fluidized bed reactor is 0.01-1 m / s.

[0027] The second sintering process specifically includes: heating the fluidized bed reactor to 600-900℃ at a heating rate of 1-8℃ / min, and keeping the temperature for 1-12 hours.

[0028] The inert gas includes one or more of nitrogen, argon, and helium; and the flow rate of the inert gas in the fluidized bed reactor is 0.01-1 m / s.

[0029] Preferably, after the natural cooling to room temperature, the preparation method further includes: performing a crushing treatment on the oxyfluoride solid electrolyte block.

[0030] The equipment for the crushing treatment is a fluidized bed jet mill or a flat jet mill.

[0031] The pressure of the compressed air during the crushing treatment is 0.5-3 MPa, and the dew point of the compressed air is less than -20℃.

[0032] In a second aspect, the present application provides an oxyfluoride solid electrolyte prepared by the preparation method of the first aspect, and the chemical general formula of the oxyfluoride solid electrolyte is Li x La y M1 a M2 b M3 c O6F, wherein x, y, a, b, and c are the molar percentages of the corresponding elements, and 1

[0033] The particle size Dv50 of the oxyfluoride solid electrolyte is 200 nm-2.0 μm.

[0034] The compactness of the oxyfluoride solid electrolyte is greater than 90%.

[0035] The ion conductivity of the oxyfluoride solid electrolyte is greater than 6 mS / cm.

[0036] Preferably, the M1 element specifically includes one or more of Zr, Ti, Hf, Si, Ge, and Sn.

[0037] The M2 element specifically includes one or more of Nb, Sb, Bi, V, and Ta.

[0038] The M3 element specifically includes one or more of W, Cr, Mo, and Mn.

[0039] In a third aspect, the present application provides a lithium battery comprising the oxyfluoride solid electrolyte prepared by the preparation method of the first aspect or the oxyfluoride solid electrolyte of the second aspect.

[0040] The preparation method of the oxyfluoride solid electrolyte and the oxyfluoride solid electrolyte provided by the present application have the following technical effects.

[0041] (1) The present application provides a preparation method of an oxyfluoride solid electrolyte. First, non-fluorine raw materials, pore-forming agents, and solvents are ground and mixed to form a slurry, and then spray granulation is performed to obtain initial microparticles. The initial microparticles are placed in a boiling bed reactor, and first-stage sintering is performed to remove the pore-forming agents and residual solvents in the initial microparticles, thereby obtaining porous microparticles. Then, fluorine source gas is introduced for second-stage sintering, so that the fluorine-containing active body decomposed from the fluorine source gas fully reacts with the porous microparticles. The product after the reaction is crushed to obtain the oxyfluoride solid electrolyte.

[0042] The preparation method of the present application reduces the initial particle size of the raw materials by grinding, thereby increasing the specific surface area of the raw materials, improving the activity of the raw materials, and improving the mixing uniformity. The slurry droplet surface is instantaneously dehydrated to form a gel shell by spray granulation, and the mixed state of the raw materials is "frozen" in the microspheres to obtain initial microparticles, which provides conditions for subsequent preparation of a porous structure. Two-stage sintering is performed in a boiling bed reactor. The first-stage sintering forms porous microparticles, and the second-stage sintering allows the porous microparticles to react with fluorine-containing gas. The fluorine element can be uniformly doped into the crystal lattice, which can improve the consistency of the final product in composition and structure, and make the obtained oxyfluoride solid electrolyte stable in performance. The preparation method provided by the present application has low energy consumption, can reduce costs, and improve efficiency.

[0043] (2) The oxyfluoride solid electrolyte prepared by the preparation method has high density and high ion conductivity, and can be widely used in lithium batteries, especially in all-solid-state lithium batteries. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1A flowchart of a preparation method of the oxyfluoride solid-state electrolyte provided in the embodiments of the present application is shown.

[0045] Figure 2 X-ray diffraction (XRD) patterns of the solid-state electrolytes prepared for the embodiment 1, the comparative example 1, the comparative example 2 and the comparative example 3 of the present application are shown. DETAILED DESCRIPTION

[0046] The technical solutions of the present application will be further described in detail below with the aid of the accompanying drawings and embodiments.

[0047] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with the aid of the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0048] The embodiments of the present application provide a preparation method of an oxyfluoride solid-state electrolyte, as shown in Figure 1 The preparation method specifically comprises the following steps.

[0049] In step 110, a lithium source material, a lanthanum source material and a material containing a doping element are weighed as raw materials according to the stoichiometric ratio of the chemical formula of the oxyfluoride solid-state electrolyte, and are placed in a grinding machine together with a pore former and a solvent for grinding treatment to obtain a mixed slurry.

[0050] The chemical formula of the oxyfluoride solid-state electrolyte to be prepared is Li x La y M1 a M2 b M3 c O6F, wherein x, y, a, b, c are the mole percentages of the corresponding elements, and 1

[0051] The lithium source material includes one or more of lithium carbonate, lithium hydroxide, lithium oxalate, lithium acetate and lithium nitrate.

[0052] The lanthanum source material includes one or more of lanthanum trioxide, lanthanum carbonate, lanthanum nitrate, lanthanum hydroxide and lanthanum fluoride.

[0053] The material containing the doping element includes one or more of the material containing the M1 element, the material containing the M2 element, and the material containing the M3 element. Specifically, the M1 element specifically includes one or more of Zr, Ti, Hf, Si, Ge, and Sn. The M2 element specifically includes one or more of Nb, Sb, Bi, V, and Ta. The M3 element specifically includes one or more of W, Cr, Mo, and Mn.

[0054] The pore-forming agent includes one or more of polyethylene glycol, polyvinylpyrrolidone, starch, and polymethyl methacrylate. The mass of the pore-forming agent accounts for 1% to 20% of the total mass of the raw material.

[0055] The solvent includes one or more of deionized water, ethanol, NMP, isopropyl alcohol, and acetone.

[0056] The rotation speed of the grinding machine is set to 1000 rpm to 3000 rpm, which can be any value within this range, for example, 1000 rpm, 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm, etc., but is not limited to the listed values. Other values not listed within this value range are also applicable.

[0057] The grinding time is 1 hour to 6 hours, which can be any value within this range, for example, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, etc., but is not limited to the listed values. Other values not listed within this value range are also applicable.

[0058] The solid content of the mixed slurry is 10wt% to 45wt%.

[0059] In this step, the initial particle size of the raw material is reduced by grinding, thereby increasing the specific surface area of the raw material, improving the activity of the raw material, and improving the uniformity of the mixed materials.

[0060] In step 120, the mixed slurry is spray granulated to obtain initial microparticles.

[0061] The spray granulation equipment is a spray dryer, the inlet temperature of the spray dryer is 180℃ to 240℃, and the outlet temperature is 60℃ to 120℃.

[0062] In this step, the surface of the droplets of the mixed slurry is instantaneously dehydrated to form a gel shell by spray drying, the mixed state of the raw material is "frozen" in the gel shell to obtain initial microparticles, and conditions are provided for subsequent preparation of porous structure particles.

[0063] In step 130, the initial microparticles are placed in a fluidized bed reactor and subjected to first-stage sintering in an air atmosphere to remove the pore-forming agent and residual solvent, thereby obtaining porous microparticles.

[0064] The flow rate of the air in the ebullated bed reactor is 1.5 m / s to 3.0 m / s.

[0065] The first-stage sintering specifically includes: heating the ebullated bed reactor from room temperature to 300 DEG C to 500 DEG C at a heating rate of 1 DEG C / min to 8 DEG C / min, and keeping the temperature for 1 hour to 8 hours.

[0066] The porosity of the porous microparticles is 30% to 50%.

[0067] The porous microparticles prepared in this step are oxide precursor particles with a porous structure. By using an ebullated bed reactor with uniform temperature, easy control and sufficient interphase contact, the microparticles with a porous structure are obtained by removing the pore-forming agent in the first-stage sintering, which greatly increases the specific surface area of the particles, provides a large reaction interface for the subsequent fluorination reaction, and provides a diffusion channel for the fluorine-containing gas, so that the fluorine-containing gas can penetrate into the interior of the particles along the pores in the second-stage sintering, realizing the reaction from the inside to the outside or simultaneously from the inside and the outside. Compared with the traditional one-step preparation of oxyfluoride solid electrolyte, the distributed preparation can first form oxide precursor particles with a porous structure, thereby fundamentally avoiding the problem that the one-step preparation directly forms a dense shell, which prevents the internal material from fully reacting with fluorine, i.e., solving the problem of incomplete reaction caused by the "core-shell structure" in the traditional preparation process.

[0068] In step 140, the atmosphere in the ebullated bed reactor is switched to a fluorine-containing gas, and the second-stage sintering is performed to make the fluorine-containing gas and / or the fluorine-containing active body decomposed from the fluorine-containing gas react with the porous microparticles; after the sintering is completed, the heating is stopped, the atmosphere is switched to an inert gas atmosphere, and the natural cooling to room temperature is performed to obtain the oxyfluoride solid electrolyte.

[0069] The fluorine-containing gas includes one or more of nitrogen tetrafluoride, nitrogen trifluoride, hydrogen fluoride vapor, polytetrafluoroethylene, and ammonium fluoride; the flow rate of the fluorine-containing gas in the ebullated bed reactor is 1.5 m / s to 3.0 m / s; the fluorine-containing active body is a highly reactive fluorine-containing substance, including elemental fluorine, fluorine radicals, hydrogen fluoride, and small-molecule fluorocarbons; the small-molecule fluorocarbons include hexafluoroethylene, carbon tetrafluoride, and octafluorocyclobutane. Different fluorine-containing gases are selected to obtain different fluorine-containing active bodies at high temperatures, and the fluorine-containing gas itself or the fluorine-containing active body decomposed therefrom can react with the porous microparticles inside the pores and on the surface of the oxide precursor particles with a porous structure.

[0070] The second-stage sintering specifically includes: heating the ebullated bed reactor to 600 DEG C to 900 DEG C at a heating rate of 1 DEG C / min to 8 DEG C / min, and keeping the temperature for 1 hour to 12 hours.

[0071] The inert gas includes one or more of nitrogen, argon, and helium; and the flow rate of the inert gas in the ebullated bed reactor is 1.5 m / s to 3.0 m / s.

[0072] In the second-stage sintering process of the present step, the porous structure formed in the first-stage sintering process enables the fluorine-containing gas to fully react with the porous microparticles in gas-solid contact, and the fluorine element can be uniformly doped into the crystal lattice, thereby not only improving the density of the oxyfluoride solid-state electrolyte, but also ensuring the uniformity of the composition and structure, thus promoting ion transmission and significantly improving the ionic conductivity.

[0073] Step 150, crushing the oxyfluoride solid-state electrolyte.

[0074] The crushing equipment is a fluidized bed jet mill or a flat jet mill.

[0075] The pressure of the compressed air during the crushing process is 0.5 MPa to 3 MPa, and the dew point of the compressed air is less than -20℃.

[0076] The chemical general formula of the oxyfluoride solid-state electrolyte prepared by the present embodiment is Li x La y M1 a M2 b M3 c O6F, wherein x, y, a, b, and c are the molar percentages of the corresponding elements, and 1 < x + 3y < 5, 0 < x ≤ 2, 1 / 3 < y < 5 / 3, 0 ≤ a ≤ 2, 0 ≤ b ≤ 2, 0 ≤ c ≤ 2, a + b + c = 2, M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation. Specifically, M1 includes one or more of Zr, Ti, Hf, Si, Ge, and Sn. M2 includes one or more of Nb, Sb, Bi, V, and Ta. M3 includes one or more of W, Cr, Mo, and Mn.

[0077] The particle size Dv50 of the oxyfluoride solid-state electrolyte prepared by the preparation method provided by the present embodiment is between 200 nm and 2.0 μm, which can be any value within this range, such as 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, etc., but is not limited to the listed values, and other values not listed within this range are also applicable.

[0078] The density of the oxyfluoride solid-state electrolyte prepared by the present embodiment is greater than 90%.

[0079] The ion conductivity of the oxyfluoride solid-state electrolyte prepared by the embodiment of the present application is greater than 6 mS / cm.

[0080] The oxyfluoride solid-state electrolyte prepared by the embodiment of the present application can be used in a lithium battery, for example, can be used as an additive in the preparation of a negative electrode sheet and / or a positive electrode sheet, and / or as a solid-state electrolyte film for assembling a full solid-state battery.

[0081] In order to better understand the technical solutions provided by the present application, the following describes the preparation method and characteristics of the oxyfluoride solid-state electrolyte of the present application with multiple specific examples.

[0082] Embodiment 1 The embodiment of the present application provides an oxyfluoride solid-state electrolyte Li 1.25 La 0.58 Nb2O6F, and a preparation method thereof, which specifically comprises the following steps.

[0083] (1) According to the stoichiometric ratio of the chemical formula Li 1.25 La 0.58 Nb2O6F of the oxyfluoride solid-state electrolyte, lithium carbonate, lanthanum trioxide, and niobium pentoxide are weighed as raw materials, and are placed in a grinding machine together with polyethylene glycol and a solvent deionized water, and are ground at a speed of 1800 rpm for 3.5 hours to obtain a mixed slurry with a solid content of 25 wt%. The mass of the polyethylene glycol accounts for 10% of the raw materials.

[0084] (2) The mixed slurry is placed in a spray dryer to perform spray granulation, the temperature of the feed inlet of the spray dryer is 220°C, and the temperature of the discharge outlet is 120°C, to obtain initial microparticles.

[0085] (3) The initial microparticles are placed in a fluidized bed reactor, the flow rate of air in the fluidized bed reactor is 0.15 m / s under an air atmosphere, the fluidized bed reactor is heated from room temperature to 450°C at a heating rate of 5°C / min, and is kept for 6 hours, so as to remove the pore-forming agent and residual solvent, and to obtain porous microparticles with a porosity of 36.7%.

[0086] (4) The atmosphere in the fluidized bed reactor is switched to nitrogen tetrafluoride gas with a flow rate of 0.10 m / s, the fluidized bed reactor is heated to 850°C at a heating rate of 5°C / min, and is kept for 6 hours, so that the fluorine-containing active body decomposed by the nitrogen tetrafluoride gas reacts with the porous microparticles; after sintering is completed, heating is stopped, the atmosphere is switched to a nitrogen atmosphere, and natural cooling is performed to room temperature, to obtain the oxyfluoride solid-state electrolyte.

[0087] (5) The oxyfluoride solid-state electrolyte is subjected to a crushing treatment by means of an air flow crusher, to obtain crushed oxyfluoride solid-state electrolyte Li 1.25 La0.58 Nb2O6F; wherein, the compressed air pressure in the crushing process is 2 MPa, and the dew point of the compressed air is -30℃.

[0088] The oxyfluoride solid-state electrolyte Li 1.25 La 0.58 The XRD pattern of Nb2O6F is shown in FIG. 1, wherein the abscissa represents the diffraction angle (2-Theta, unit degree, symbol °), and the ordinate represents the intensity of the diffraction peak (Intensity, unit arb. unit). Figure 2

[0089] Example 2 The oxyfluoride solid-state electrolyte Li 1.25 La 0.58 Ti 0.5 SbW 0.5 O6F, specifically comprising the following steps.

[0090] (1) According to the stoichiometric ratio of the oxyfluoride solid-state electrolyte Li 1.25 La 0.58 Ti 0.5 SbW 0.5 O6F, lithium carbonate, lanthanum trioxide, titanium dioxide, antimony pentoxide, and tungsten oxide are weighed as raw materials, and are placed in a grinder together with polyethylene glycol and deionized water as a solvent, and are ground at a speed of 2000 rpm for 3 hours to obtain a mixed slurry with a solid content of 30 wt%. The mass of the polyethylene glycol accounts for 15% of the raw materials.

[0091] (2) The mixed slurry is placed in a spray dryer for spray granulation, the temperature of the feed inlet of the spray dryer is 220℃, and the temperature of the discharge outlet is 120℃, to obtain initial microparticles.

[0092] (3) The initial microparticles are placed in a fluidized bed reactor, the flow rate of the air in the fluidized bed reactor is 0.20 m / s under an air atmosphere, the fluidized bed reactor is heated from room temperature to 500℃ at a heating rate of 5℃ / min, and is kept at 500℃ for 5 hours to remove the pore-forming agent and residual solvent, and porous microparticles with a porosity of 44.6% are obtained.

[0093] (4) The atmosphere in the fluidized bed reactor is switched to ammonium fluoride gas with a flow rate of 0.14 m / s, the fluidized bed reactor is heated to 850℃ at a heating rate of 5℃ / min, and is kept at 850℃ for 4 hours to make the fluorine-containing active body decomposed from the ammonium fluoride gas react with the porous microparticles; after sintering is completed, heating is stopped, the atmosphere is switched to argon atmosphere, and natural cooling is performed to room temperature to obtain the oxyfluoride solid-state electrolyte.

[0094] ​(5) The fluorine oxide solid electrolyte is crushed by an air flow crusher to obtain crushed fluorine oxide solid electrolyte Li 1.25 La 0.58 Ti 0.5 SbW 0.5 O6F; wherein the compressed air pressure in the crushing process is 2 MPa, and the dew point of the compressed air is-30 DEG C.

[0095] Example 3 The embodiment of the present application provides a fluorine oxide solid electrolyte Li 1.2 La 0.6 TiWO6F, and a preparation method thereof, specifically comprising the following steps.

[0096] (1) According to the chemical formula Li 1.2 La 0.6 TiWO6F, lithium carbonate, lanthanum trioxide, titanium dioxide and tungsten oxide are weighed as raw materials, and are placed in a grinding machine together with polyvinylpyrrolidone and deionized water, and are ground at a speed of 2000 rpm for 4 hours to obtain a mixed slurry with a solid content of 30 wt%. The mass of the polyvinylpyrrolidone accounts for 15% of the mass of the raw materials.

[0097] (2) The mixed slurry is placed in a spray dryer for spray granulation, the temperature of the feed inlet of the spray dryer is 220 DEG C, and the temperature of the discharge outlet is 120 DEG C, to obtain initial microparticles.

[0098] (3) The initial microparticles are placed in a fluidized bed reactor, the flow rate of air in the fluidized bed reactor is 0.15 m / s under an air atmosphere, the fluidized bed reactor is heated from room temperature to 500 DEG C at a heating rate of 5 DEG C / min, and is kept for 5 hours to remove the pore forming agent and residual solvent, to obtain porous microparticles with a porosity of 43.1%.

[0099] (4) The atmosphere in the fluidized bed reactor is switched to ammonium fluoride gas with a flow rate of 0.10 m / s, the fluidized bed reactor is heated to 850 DEG C at a heating rate of 5 DEG C / min, and is kept for 6 hours to make the fluorine-containing active body decomposed from the ammonium fluoride gas react with the porous microparticles; after sintering, heating is stopped, the atmosphere is switched to argon atmosphere, and natural cooling is performed to room temperature to obtain a fluorine oxide solid electrolyte.

[0100] (5) The fluorine oxide solid electrolyte is crushed by an air flow crusher to obtain crushed fluorine oxide solid electrolyte Li 1.2 La 0.6 TiWO6F; wherein the compressed air pressure in the crushing process is 1.2 MPa, and the dew point of the compressed air is-30 DEG C.

[0101] Example 4 The embodiment of the present application provides a fluorine oxide solid electrolyte Li 1.25 La 1.25 A preparation method of Ti2O6F, specifically comprising the following steps.

[0102] (1) according to the chemical formula of the fluorine oxide solid electrolyte Li 1.25 La 1.25 The stoichiometric ratio of Ti2O6F, lithium hydroxide, lanthanum carbonate, titanium oxide, lithium fluoride as raw materials, and polyvinylpyrrolidone and deionized water are placed in a grinding machine, and the grinding treatment is carried out at a speed of 2500 rpm for 3 hours, to obtain a mixed slurry with a solid content of 20wt%. The mass of polyvinylpyrrolidone accounts for 10% of the raw materials.

[0103] (2) the mixed slurry is placed in a spray dryer for spray granulation, the inlet temperature of the spray dryer is 220℃, and the outlet temperature is 120℃, to obtain initial microparticles.

[0104] (3) the initial microparticles are placed in a fluidized bed reactor, the air flow rate in the fluidized bed reactor is 0.20m / s, the fluidized bed reactor is heated from room temperature to 500℃ at a heating rate of 5℃ / min, and the heating is maintained for 5 hours, to remove the pore forming agent and residual solvent, and obtain porous microparticles with a porosity of 36.8%.

[0105] (4) the atmosphere in the fluidized bed reactor is switched to ammonium fluoride gas with a flow rate of 0.15m / s, the fluidized bed reactor is heated to 850℃ at a heating rate of 5℃ / min, and the heating is maintained for 6 hours, so that the fluorine-containing active body decomposed from the ammonium fluoride gas reacts with the porous microparticles; after sintering, the heating is stopped, the atmosphere is switched to argon atmosphere, and the temperature is naturally cooled to room temperature, to obtain the fluorine oxide solid electrolyte.

[0106] (5) the fluorine oxide solid electrolyte is crushed by an air flow crusher to obtain crushed fluorine oxide solid electrolyte Li 1.25 La 1.25 Ti2O6F; wherein, the compressed air pressure in the crushing process is 1.2MPa, and the dew point of the compressed air is-30℃.

[0107] In order to better illustrate the effect of the embodiment of the present application, the comparative example is compared with the above embodiment.

[0108] Comparative Example 1 The present comparative example provides a preparation method of a fluorine oxide solid electrolyte, which is different from the embodiment 1 in that no pore forming agent is introduced in the preparation process, and the specific preparation process is as follows.

[0109] (1) according to the chemical formula of the fluorine oxide solid electrolyte Li1.25 La 0.58 Nb2O6F stoichiometric ratio, lithium carbonate, lanthanum trioxide, niobium pentoxide were weighed and mixed uniformly to obtain the mixture raw material.

[0110] (2) The mixture raw material was placed in a fluidized bed reactor, nitrogen tetrafluoride gas with a flow rate of 0.15 m / s was introduced, and then the fluidized bed reactor was heated to 850°C at a heating rate of 5°C / min, and the nitrogen tetrafluoride gas was decomposed for 6 hours. The fluorine-containing active body reacted with the mixture raw material; after sintering, heating was stopped, the atmosphere was switched to nitrogen atmosphere, and natural cooling was carried out to room temperature to obtain the oxyfluoride solid electrolyte.

[0111] (3) The oxyfluoride solid electrolyte was crushed by an air flow crusher to obtain the crushed oxyfluoride solid electrolyte Li 1.25 La 0.58 Nb2O6F; wherein the compressed air pressure during crushing is 2 MPa, and the dew point of the compressed air is -30°C.

[0112] The oxyfluoride solid electrolyte Li 1.25 La 0.58 Nb2O6F prepared by the comparative example 1, and the XRD pattern is shown in Figure 2 .

[0113] Comparative example 2 The comparative example provides a preparation method of an oxyfluoride solid electrolyte, which is different from example 1 in that a fluidized bed reactor is not used in the preparation process, but sintering is directly carried out in a box furnace. The specific preparation process is as follows.

[0114] (1) The preparation process of the mixed slurry is the same as that of example 1.

[0115] (2) The preparation process of the initial microparticles is the same as that of example 1.

[0116] (3) The initial microparticles were placed in a box furnace, and the box furnace was heated from room temperature to 500°C at a heating rate of 5°C / min under air atmosphere, and was kept for 5 hours to remove the pore-forming agent and residual solvent, and the porous microparticles with a porosity of 37.3% were obtained.

[0117] (4) The atmosphere in the box furnace was switched to nitrogen tetrafluoride gas with a flow rate of 0.01 m / s, and the box furnace was heated to 1000°C at a heating rate of 5°C / min, and the nitrogen tetrafluoride gas was decomposed for 6 hours. The fluorine-containing active body reacted with the porous microparticles; after sintering, heating was stopped, the atmosphere was switched to nitrogen atmosphere, and natural cooling was carried out to room temperature to obtain the oxyfluoride solid electrolyte.

[0118] (5) The oxyfluoride solid electrolyte is crushed by an air flow crusher to obtain crushed oxyfluoride solid electrolyte Li 1.25 La 0.58 Nb2O6F; wherein the compressed air pressure in the crushing process is 2 MPa, and the dew point of the compressed air is -30°C.

[0119] The oxyfluoride solid electrolyte Li 1.25 La 0.58 Nb2O6F prepared in Comparative Example 2 has an XRD pattern as shown in Figure 2

[0120] Comparative Example 3 The comparative example provides a conventional preparation method of an oxyfluoride solid electrolyte, which is different from Example 1 in that no pore-forming agent and boiling bed reactor are used, and the specific preparation process is as follows.

[0121] (1) According to the stoichiometric ratio of the chemical formula Li 1.25 La 0.58 Nb2O6F of the oxyfluoride solid electrolyte, lithium carbonate, lanthanum trioxide, and lithium fluoride are weighed and uniformly mixed to obtain a mixture raw material.

[0122] (2) The mixture raw material is placed in a box furnace, heated to 1000°C at a heating rate of 5°C / min under a nitrogen atmosphere, and kept for 6 hours; after sintering is completed, heating is stopped, the atmosphere is switched to a nitrogen atmosphere, and natural cooling is performed to room temperature to obtain an oxyfluoride solid electrolyte.

[0123] (3) The oxyfluoride solid electrolyte is crushed by an air flow crusher to obtain crushed oxyfluoride solid electrolyte Li 1.25 La 0.58 Nb2O6F; wherein the compressed air pressure in the crushing process is 2 MPa, and the dew point of the compressed air is -30°C.

[0124] The oxyfluoride solid electrolyte Li 1.25 La 0.58 Nb2O6F prepared in Comparative Example 3 has an XRD pattern as shown in Figure 2

[0125] By Figure 2 Comparing Comparative Examples 1-3 with Example 1 in the XRD pattern, it can be seen that the XRD of Example 1 has no impurity peaks, which is because the preparation method provided in Example 1 of pre-forming porous particles, uniformly reacting with fluorine source, and finally crushing avoids the problem of forming a dense shell on the surface of the raw material, which causes incomplete reaction. The preparation method provided in Example 1 improves the uniformity of the reaction, and the obtained fluoride solid electrolyte has no other impurity peaks and has a good phase. ​​

[0126] The fluorine oxide solid electrolytes of Examples 1-4 and Comparative Examples 1-3 were subjected to performance tests, and the specific test items and test methods are as follows.

[0127] Test 1, test of densification α, was carried out by the following method.

[0128] Sample preparation: the fluorine oxide solid electrolyte was pressed into a ceramic sheet using a tablet press, and the ceramic sheet was sintered at 1000°C for 5 hours for densification to obtain a densified ceramic sheet sample, and the obtained ceramic sheet sample was placed in a drying oven at 110°C for 2 hours.

[0129] The mass of the fluorine oxide solid electrolyte in air was measured using an analytical balance (空气） .

[0130] The ceramic sheet sample was placed on a sample holder connected to an analytical balance to test the sample mass, and the sample holder was placed in deionized water to obtain the mass of the fluorine oxide solid electrolyte in deionized water under the action of buoyancy (水） .

[0131] The densification was calculated according to the formula: ρ=ρ (水) ×W (空气） / (W (空气） -W (水） ); Densification α = (ρ / ρ0)*100%; ρ is the volume density of the fluorine oxide solid electrolyte ceramic sheet, in grams per cubic centimeter (g / cm 3 ); W (空气） is the mass of the fluorine oxide solid electrolyte ceramic sheet in air, in grams (g); W (水） is the mass of the fluorine oxide solid electrolyte ceramic sheet in deionized water, in grams (g); ρ (水) is the density of water, in grams per cubic centimeter (g / cm 3 ); ρ0 is the theoretical density of the fluorine oxide solid electrolyte ceramic sheet, in grams per cubic centimeter (g / cm 3 ).

[0132] Test 2, test of ionic conductivity, was carried out by the following method.

[0133] The fluorine oxide solid electrolyte powder was ground uniformly and pressed into a ceramic sheet, which was sintered at 1000°C for 2 hours for densification to obtain a densified ceramic sheet sample.

[0134] The two round surfaces of the sintered ceramic sheet are polished smooth in turn using 400-mesh, 1000-mesh and 3000-mesh sandpaper, so that the entire round surface is flat and clean without defects.

[0135] The thickness L of the ceramic sheet is measured using a digital thickness gauge, and the diameter of the ceramic sheet is measured using a vernier caliper, and the cross-sectional area of the round surface of the ceramic sheet is further calculated and denoted as S.

[0136] The surface of the polished solid electrolyte sheet sample is coated with conductive silver paste, and then the conductive silver paste on the side of the solid electrolyte sheet is ground off.

[0137] The test is carried out under the conditions of a temperature of (25±2) °C and a humidity of less than 50%, the parameters of the Zahner electrochemical workstation are set, the perturbation voltage is 10 mV, the frequency is 0.1 Hz-10 6 Hz, and the impedance curve is tested.

[0138] The resistance R is calculated by fitting using the Zahner Analysis software, and the room temperature ionic conductivity of the solid electrolyte is calculated according to the ionic conductivity formula.

[0139] The ionic conductivity test formula is: σ = L / (R*S); In the formula, σ is the ionic conductivity of the oxyfluoride solid electrolyte ceramic sheet, in units of siemens per centimeter (S / cm); L is the thickness of the oxyfluoride solid electrolyte ceramic sheet, in units of centimeters (cm); R is the fitted impedance value of the oxyfluoride solid electrolyte ceramic sheet, in units of ohms (Ω); S is the cross-sectional area of the round surface of the oxyfluoride solid electrolyte ceramic sheet, in units of square centimeters (cm 2 ).

[0140] Test 3: Test the particle size Dv50 of the oxyfluoride solid electrolyte.

[0141] The particle size Dv50 of the material refers to the volume median particle size, which is the median value according to the volume. In the embodiments of the present application, the volume-ordered median particle size is specifically used, which represents the particle size distributed in 50% of the mixed slurry according to the volume distribution. The particle size Dv50 is a meaning known in the art. The particle size Dv50 of the material provided in the embodiments of the present application can be measured by instruments known in the art and conventional methods. Specifically, in the embodiments of the present application, the particle size Dv50 is measured by using a Mastersizer 3000 laser particle size analyzer of Malvern Instruments Ltd., UK.

[0142] Table 1 is a summary of the test data of Examples 1-4 and Comparative Examples 1-3.

[0143] Table 1 As can be seen from the comparison of the density test data in Table 1, the density of Examples 1-4 is much higher than that of Comparative Examples 1-3, because in the preparation method of Examples 1-4, the raw materials are shaped by grinding and spray granulation, the pore-forming agent is uniformly mixed with the raw materials, and a porous structure of microparticles is formed in the subsequent sintering process. This porous structure of microparticles is in solid-gas contact reaction with fluorine-containing gas, and in the further sintering process, the fluorine-containing active body decomposed from the fluorine source can be uniformly distributed in the porous structure of microparticles and fully react with the microparticles, so that the raw materials on the surface and in the pores of the porous microparticles react with the fluorine-containing active body to densify, thereby improving the density of the final oxyfluoride solid electrolyte.

[0144] As can be seen from the comparison of the ion conductivity in Table 1, the ion conductivity of Examples 1-4 is better than that of Comparative Examples 1-3, because the oxyfluoride solid electrolyte prepared in Examples 1-4 has high density, and the improvement of high density can improve the ion transmission efficiency in the solid electrolyte, thereby improving the ion conductivity of the solid electrolyte.

[0145] As can be seen from the comparison of the particle size test data in Table 1, the crushing effect of the oxyfluoride solid electrolyte prepared in Examples 1-4 is better than that of Comparative Examples 1-3, because the oxyfluoride solid electrolyte block in Examples 1-4 has a porous structure before crushing, and the internal connection of the porous structure is more prone to breakage. Comparative Examples 1 and 3 use conventional methods to prepare the oxyfluoride solid electrolyte block, which does not have a porous structure, so the crushing effect is inferior to that of Examples 1-4. Although Comparative Example 2 has a porous structure, the material is in a static state during sintering in the box furnace, and some porous microparticles are in static contact during the sintering process, which may cause the phenomenon of porous blockage and structure collapse, affecting the subsequent crushing results.

[0146] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a fluoride oxide solid electrolyte, characterized in that, The preparation method includes: According to the stoichiometric ratio of the general chemical formula for fluoride oxide solid electrolytes, lithium source material, lanthanum source material, and material containing doped elements are weighed as raw materials, and placed together with pore-forming agent and solvent in a grinding mill for grinding to obtain a mixed slurry; wherein, the material containing doped elements includes one or more of the following: material containing M1 element, material containing M2 element, and material containing M3 element. The mixed slurry is spray-granulated to obtain initial microparticles; The initial microparticles are placed in a fluidized bed reactor and sintered in an air atmosphere to remove the pore-forming agent and residual solvent, thereby obtaining porous microparticles; the porous microparticles are oxide precursor particles with a porous structure. The atmosphere in the fluidized bed reactor is switched to a fluorine-containing gas for a second-stage sintering process, whereby the fluorine-containing gas and / or the fluorine-containing active substances decomposed from the fluorine-containing gas react with the porous microparticles inside and on the surface of the oxide precursor particles. After sintering, heating is stopped, the atmosphere is switched to an inert gas atmosphere, and the mixture is allowed to cool naturally to room temperature to obtain the fluorine oxide solid electrolyte.

2. The preparation method according to claim 1, characterized in that, The lithium source material includes one or more of lithium carbonate, lithium hydroxide, lithium oxalate, lithium acetate, and lithium nitrate. The lanthanum source material includes one or more of the following: lanthanum trioxide, lanthanum carbonate, lanthanum nitrate, lanthanum hydroxide, and lanthanum fluoride; The chemical formula of the fluoride oxide solid electrolyte is Li x La y M1 a M2 b M3 c O6F, where x, y, a, b, and c are the molar percentages of the corresponding elements, and 1 < x + 3y < 5, 0 < x ≤ 2, 1 / 3 < y < 5 / 3, 0 ≤ a ≤ 2, 0 ≤ b ≤ 2, 0 ≤ c ≤ 2, a + b + c = 2, element M1 is a tetravalent cation, element M2 is a pentavalent cation, and element M3 is a hexavalent cation; The pore-forming agent includes one or more of polyethylene glycol, polyvinylpyrrolidone, starch, and polymethyl methacrylate; the mass of the pore-forming agent accounts for 1% to 20% of the total mass of the raw materials.

3. The preparation method according to claim 1, characterized in that, The M1 element specifically includes one or more of Zr, Ti, Hf, Si, Ge, and Sn; The M2 element specifically includes one or more of Nb, Sb, Bi, V, and Ta; The M3 element specifically includes one or more of W, Cr, Mo, and Mn.

4. The preparation method according to claim 1, characterized in that, The solvent includes one or more of the following: deionized water, ethanol, NMP, isopropanol, and acetone; The grinding mill's rotation speed is set to 1000 rpm to 3000 rpm, and the grinding process takes 1 hour to 6 hours. The solid content of the mixed slurry is 10wt% to 45wt%. The equipment for spray granulation is a spray dryer; the inlet temperature of the spray dryer is 180℃~240℃, and the outlet temperature is 60℃~120℃.

5. The preparation method according to claim 1, characterized in that, The air velocity in the fluidized bed reactor is 0.01 m / s to 1 m / s; The first sintering stage specifically includes: heating the fluidized bed reactor from room temperature to 300℃ to 500℃ at a heating rate of 1℃ / min to 8℃ / min, and holding it at that temperature for 1 hour to 8 hours; The porosity of the porous microparticles is 30% to 50%.

6. The preparation method according to claim 1, characterized in that, The fluorine-containing gas includes one or more of nitrogen tetrafluoride, nitrogen trifluoride, hydrogen fluoride vapor, polytetrafluoroethylene, and ammonium fluoride; the flow rate of the fluorine-containing gas in the fluidized bed reactor is 0.01 m / s to 1 m / s; The second stage of sintering specifically includes: heating the fluidized bed reactor to 600℃~900℃ at a heating rate of 1℃ / min~8℃ / min, and holding it at that temperature for 1 hour~12 hours; The inert gas includes one or more of nitrogen, argon, and helium; the flow rate of the inert gas in the fluidized bed reactor is 0.01 m / s to 1 m / s.

7. The preparation method according to claim 1, characterized in that, After naturally cooling to room temperature, the preparation method further includes: pulverizing the fluoride oxide solid electrolyte block; The equipment used for the pulverization process is a fluidized bed jet mill or a flat jet mill; The pressure of the compressed air during the pulverization process is between 0.5 MPa and 3 MPa, and the dew point of the compressed air is less than -20°C.

8. A fluorine oxide solid electrolyte prepared by any one of the preparation methods according to claims 1-7, characterized in that, The chemical formula of the fluoride oxide solid electrolyte is Li x La y M1 a M2 b M3 c O6F, where x, y, a, b, and c are the molar percentages of the corresponding elements, and 1 < x + 3y < 5, 0 < x ≤ 2, 1 / 3 < y < 5 / 3, 0 ≤ a ≤ 2, 0 ≤ b ≤ 2, 0 ≤ c ≤ 2, a + b + c = 2, element M1 is a tetravalent cation, element M2 is a pentavalent cation, and element M3 is a hexavalent cation; The particle size Dv50 of the fluorine oxide solid electrolyte is 200 nm to 2.0 μm; The density of the fluoride solid electrolyte is greater than 90%. The ionic conductivity of the fluorine oxide solid electrolyte is greater than 6 mS / cm.

9. The fluorine oxide solid electrolyte according to claim 8, characterized in that, The M1 element specifically includes one or more of Zr, Ti, Hf, Si, Ge, and Sn; The M2 element specifically includes one or more of Nb, Sb, Bi, V, and Ta; The M3 element specifically includes one or more of W, Cr, Mo, and Mn.

10. A lithium battery, characterized in that, The lithium battery includes a fluorine oxide solid electrolyte prepared by any of the preparation methods described in claims 1-7, or a fluorine oxide solid electrolyte prepared by any of claims 8-9.

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