A method for preparing a rare earth composite solid electrolyte coating material

Abstract

This application discloses a method for preparing a rare-earth composite solid electrolyte coating material, relating to the field of solid-state battery technology, comprising the following steps: Step 1, modifying solid high-purity, highly colloidal alumina powder with rare-earth-based precursor powder to obtain a modified mixture; Step 2, subjecting the modified mixture to sequential acidification and high-speed stirring dispersion to obtain a slurry; Step 3, adding LATP solid electrolyte powder to the slurry and mixing and beating to obtain a coating material; wherein the modified mixture is obtained through surface coating modification or doping modification. This application has the effect of enhancing the ion transport capability of the coating material in solid-state batteries and improving chemical and thermal stability.

Description

Technical Field

[0001] This application relates to the field of solid-state battery technology, and in particular to a method for preparing a rare-earth composite solid electrolyte coating material. Background Technology

[0002] Traditional lithium-ion batteries use liquid electrolytes, which, while offering high energy density, pose safety risks such as flammability and leakage. Therefore, solid-state batteries, with their superior safety, better cycle life, and higher energy density, are gradually becoming a key research focus for next-generation energy storage technologies.

[0003] The ion transport rate of solid electrolytes is one of the key factors affecting the performance of solid-state batteries. The development of novel solid electrolyte materials aims to improve ion conductivity, enabling solid-state batteries to achieve faster charge / discharge rates and higher energy densities to meet the demands of modern high-performance electronic devices and electric vehicles. One of the key challenges of solid-state batteries is the interfacial stability between the positive electrode, negative electrode, and solid electrolyte. Poor interfacial contact between the solid electrolyte and the electrodes can lead to problems such as high interfacial impedance, dendrite growth, and decreased cycle performance.

[0004] Studies have shown that adding a functional coating between the positive electrode, negative electrode, and solid electrolyte can effectively improve interfacial contact, reduce side reactions, and improve battery stability and conductivity.

[0005] Chinese invention patent application CN202410293543.0 discloses a solid electrolyte-SiO2 particle composite coating, its preparation method, and its application. The method involves coating a solid electrolyte onto a polyolefin separator, followed by spin-coating a thin layer of SiO2 particles onto the surface. The solid electrolyte can serve as an inorganic material to improve the electrolyte wettability, thermal stability, and mechanical properties of the polyolefin separator, and also as a highly efficient lithium-ion conductor to promote lithium-ion transport. The surface SiO2 particles act as a protective layer for the solid electrolyte, successfully preventing direct contact between the solid electrolyte and the metal electrode, inhibiting lithium dendrite growth and reduction reactions, and improving electrode interface stability.

[0006] Chinese invention patent application CN202411342644.9 discloses a coated separator for lithium batteries and its preparation method. By combining an LATP solid electrolyte interface layer and an adhesive layer containing nitrile rubber, polyurethane, and maleic anhydride, an integrated membrane layer is formed, thereby improving the hydrophilicity and heat resistance of the coated separator. This solves the defect of low electrochemical performance of traditional polyolefin separators, and makes the coated separator exhibit excellent electrochemical performance and long-term electrochemical cycling performance.

[0007] Chinese invention patent application CN202411381196.3 discloses a method for preparing a solid electrolyte coating, a composite electrode, and its application. The method involves bonding a composite substrate, consisting of a polymer film, a semi-solid coating, and a binder layer stacked sequentially, to a positive and / or negative electrode. After hot pressing, the polymer film is removed, resulting in a solid electrolyte coating on the surface of the positive and / or negative electrode. By controlling the areal density of the solid electrolyte coating, the structural stability and electrochemical performance of the coating are effectively ensured.

[0008] Chinese invention patent application CN202410828668.9 discloses a lanthanide-doped magnesium titanium phosphate solid electrolyte and its preparation and application. The lanthanide doping partially replaces the tetravalent Ti element in the magnesium titanium phosphate solid electrolyte to suppress the formation of the non-conductive secondary phase titanium pyrophosphate and increase the lattice spacing of the magnesium titanium phosphate solid electrolyte, thus widening the Li⁺ transport channel size for charge replenishment. The provided lanthanide-doped magnesium titanium phosphate solid electrolyte exhibits high tap density and excellent ionic conductivity. When used as a solid electrolyte material in solid-state lithium batteries, it can improve their cycle capacity.

[0009] Chinese invention patent application CN202311745924.X discloses a solid electrolyte material, its preparation method, and its application. By introducing one or more elements from Sc, Y, and La into the raw materials, the Al element in the square zeolite NaAlSi2O6 is partially replaced, which can improve the ionic conductivity of the material. After dehydration, it is made into a solid electrolyte slurry and coated on the surface of a separator or made into a solid electrolyte coating for a positive electrode current collector and applied to the positive electrode sheet. The resulting separator and positive electrode sheet can be used in sodium-ion batteries, which can significantly improve the rate performance, room temperature cycle performance, and high temperature cycle performance of sodium-ion batteries.

[0010] Other studies are exploring different types of coating materials, such as oxide, fluoride, and polymer coatings, to enhance the stability of the electrode-electrolyte interface.

[0011] High-purity, highly colloidal alumina can be used as a protective layer on the surface of solid-state electrolytes. It can reduce interfacial impedance, effectively preventing electrolyte dissolution and corrosion, and improving the chemical stability and safety of solid-state batteries. In all-solid-state batteries, alumina can also be used as a curing agent for the electrolyte, helping it maintain a stable structure and preventing deformation or cracking, thereby improving the battery's mechanical stability and safety. Furthermore, using alumina as a separator between different battery components or between the battery and the external environment can prevent short circuits between components or the influence of the external environment on the battery, improving battery safety.

[0012] However, there is still no way to dope rare earth elements and their compounds into functional coating materials of high-purity, highly colloidal alumina to solve the problems of weak ion transport capacity, low chemical stability and poor thermal stability, and this needs to be improved. Summary of the Invention

[0013] In view of this, the purpose of this application is to provide a method for preparing a rare earth composite solid electrolyte coating material, so as to enhance the ion transport capability of the coating material in solid-state batteries and improve its chemical and thermal stability. The specific solution is as follows:

[0014] A method for preparing a rare earth composite solid electrolyte coating material includes the following steps:

[0015] Step 1: Composite modification of solid high-purity, highly colloidal alumina powder with rare earth-based precursor powder to obtain modified mixture material;

[0016] Step 2: The modified mixture is subjected to acidification and high-speed stirring dispersion in sequence to obtain a slurry;

[0017] Step 3: Add LATP solid electrolyte powder to the slurry, mix and beat to obtain coating material;

[0018] The modified mixture is obtained by surface coating modification.

[0019] Preferably, the high-purity, highly colloidal alumina powder is Al2(OH)5Cl or high-purity boehmite; the rare earth-based precursor powder is rare earth oxide, rare earth carbonate, or rare earth oxalate.

[0020] Preferably, the high-purity, highly colloidal alumina powder is Al2(OH)5Cl; the surface coating modification includes dispersing Al2(OH)5Cl in deionized water to obtain a 5-10 wt% suspension, then adding a rare earth salt solution, which is LaCl3 or Ce(NO3)3, and simultaneously adding a precipitant. After the addition is complete, the temperature is controlled at 60-80℃ for water bath treatment for 2-4 hours, and after standing and aging for 10-16 hours, it is vacuum dried at 60℃ to obtain a modified mixture of Al2(OH)5Cl coated with rare earth carbonate or rare earth oxalate.

[0021] Preferably, the high-purity, highly colloidal alumina powder is Al2(OH)5Cl; the surface coating modification includes dispersing Al2(OH)5Cl in deionized water to obtain a 5-10 wt% suspension, then adding a rare earth nitrate solution dropwise to the suspension, stirring until homogeneous, and then adding citric acid and ethylene glycol. The molar ratio of citric acid to rare earth ions is controlled at 1:1, and the amount of ethylene glycol added is 50% of the mass percentage of citric acid, and a gel is obtained. The pH of the gel is then adjusted to 3.0-4.0, and the temperature is controlled at 80℃ while stirring to obtain another gel. Finally, the gel is mixed with Al2(OH)5Cl solid particles, dried, and calcined. The calcination temperature is controlled at 500-700℃ and held for 1.5-2 hours to obtain a modified mixture of rare earth oxide-coated Al2(OH)5Cl formed by gel decomposition.

[0022] Preferably, the high-purity, highly colloidal alumina powder is high-purity boehmite; the surface coating modification includes dispersing high-purity boehmite in deionized water to obtain a 2-5 wt% suspension, adding a rare earth-based precursor to the suspension, controlling the amount of rare earth-based precursor added to be 3-15% of the mass percentage of high-purity boehmite, adding urea, controlling the concentration of urea to be 0.5-1 mol / L, controlling the temperature to be 120-130℃, holding for 6-12 hours, cooling to room temperature, and then sequentially centrifuging, washing with ethanol, and drying, or sequentially centrifuging, washing with ethanol, and calcining to obtain a modified mixture.

[0023] Preferably, the rare earth element in the rare earth-based precursor powder is at least one of lanthanum, cerium, praseodymium, and neodymium.

[0024] Preferably, the acidification treatment is performed using at least one of hydrochloric acid, sulfuric acid, phosphoric acid, or nitric acid; the acidification treatment temperature is 20-60℃, the high-speed stirring speed is 400-2000 r / min, and the stirring time is 0.25-5 h.

[0025] Preferably, the pulping temperature is 20-60℃, the pulping speed is 400-2000 r / min, and the pulping time is 0.25-5 h.

[0026] Preferably, the mass ratio of the high-purity, highly colloidal alumina powder, rare earth-based precursor powder, and LATP solid electrolyte powder is 40-75:2-20:20-40.

[0027] Preferably: In step 3, an ionic conductivity > 10 is obtained. -2 Coating material with a density of s / cm.

[0028] As can be seen from the above scheme, this application provides a method for preparing a rare earth composite solid electrolyte coating material, which has the following beneficial effects:

[0029] 1. A coating material is obtained by combining high-purity, highly colloidal alumina, rare earth-based precursors, and LATP solid electrolyte powder. The three-dimensional framework structure of LATP solid electrolyte powder provides a fast migration channel for lithium ions. The rare earth-based precursor reduces the energy barrier for lithium ion migration, promotes ion transfer at the interface between LATP solid electrolyte powder and alumina, reduces interface impedance, and works synergistically with high-purity, highly colloidal alumina to fill the gaps between LATP solid electrolyte powders, forming a continuous ion conduction path and a highly efficient ion conduction network that avoids conduction interruption caused by the island effect.

[0030] 2. By coating and modifying with rare earth-based precursors, a uniform rare earth compound layer is formed on the surface of high-purity, highly colloidal alumina, eliminating the lattice mismatch between high-purity, highly colloidal alumina and LATP solid electrolyte powder, reducing the resistance to lithium ion migration at the interface, and synergistically adsorbing lithium ions with the high electronegativity of rare earth-based precursors to form a local high-concentration ion region, accelerating ion diffusion.

[0031] 3. By coating the surface of high-purity, highly colloidal alumina with rare earth-based precursors, an effective physical barrier is formed to prevent direct contact between high-purity, highly colloidal alumina and the cathode material, thus avoiding the generation of high-resistivity reaction products. At the same time, it buffers the redox reaction at the electrode interface and reduces the occurrence of side reactions.

[0032] 4. By adjusting the pH of the slurry through acidification treatment, the agglomeration of high-purity, highly colloidal alumina and LATP solid electrolyte powder is inhibited, and the dispersion uniformity is improved. This reduces local concentration polarization of the dispersed particles and avoids the problem of decreased chemical stability caused by material aggregation. At the same time, the acidic environment has the effect of enhancing the binding force between rare earth-based precursors and high-purity, highly colloidal alumina, thereby improving the integrity and chemical stability of the coating.

[0033] 5. Coating the surface of high-purity, highly colloidal alumina with rare earth-based precursors significantly improves the high-temperature resistance of the coating material, effectively preventing the high-purity, highly colloidal alumina from undergoing phase transformation at high temperatures. Furthermore, the rare earth-based precursors form strong bonds with the high-purity, highly colloidal alumina, thereby improving thermal conductivity, accelerating heat diffusion, and preventing localized overheating. Detailed Implementation

[0034] The technical solutions described below in conjunction with the embodiments of this application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0035] It should be mentioned that the modified mixture in this application forms a coating layer with a thickness of 5-50 nm.

[0036] The following will describe in detail the preparation method of a rare earth composite solid electrolyte coating material according to this application.

[0037] A method for preparing a rare earth composite solid electrolyte coating material includes the following steps:

[0038] Step 1: Modify solid high-purity, highly colloidal alumina powder by combining it with rare earth-based precursor powder. The rare earth element in the rare earth-based precursor powder is at least one of lanthanum, cerium, praseodymium, and neodymium to obtain a modified mixture.

[0039] Step 2: The modified mixture is subjected to acidification treatment and high-speed stirring dispersion in sequence. During the acidification treatment, at least one of hydrochloric acid, sulfuric acid, phosphoric acid or nitric acid is used, and the acidification temperature is 20-60℃. The high-speed stirring speed is 400-2000 r / min and the stirring time is 0.25-5 h. The pulping temperature is controlled at 20-60℃, the pulping speed is 400-2000 r / min and the pulping time is 0.25-5 h to obtain the pulp.

[0040] Step 3: Add LATP solid electrolyte powder to the slurry and mix and slurry. Control the mixing mass ratio of high-purity, highly colloidal alumina powder, rare earth-based precursor powder and LATP solid electrolyte powder to 40-75:2-20:20-40 to obtain an ionic conductivity >10. -2 Coating material with a density of s / cm.

[0041] The modified mixture was obtained through surface coating modification.

[0042] In the embodiments of this application, the high-purity, highly colloidal alumina powder is Al2(OH)5Cl or high-purity boehmite. The rare earth-based precursor powder is rare earth oxide, rare earth carbonate, or rare earth oxalate.

[0043] Due to the difference in properties between Al2(OH)5Cl and high-purity boehmite, when performing coating modification treatment, if the high-purity, highly colloidal alumina powder is Al2(OH)5Cl and the rare earth-based precursor powder is rare earth carbonate or rare earth oxalate, the surface coating modification includes dispersing Al2(OH)5Cl in deionized water to obtain a 5-10 wt% suspension, then adding a rare earth salt solution, namely LaCl3 or Ce(NO3)3, to the suspension while simultaneously adding a precipitant. After the addition is complete, the temperature is controlled at 60-80℃ for water bath treatment for 2-4 hours. After standing and aging for 10-16 hours, the mixture is vacuum dried at 60℃ to obtain a modified mixture of Al2(OH)5Cl coated with rare earth carbonate or rare earth oxalate.

[0044] If the high-purity, highly colloidal alumina powder is Al2(OH)5Cl and the rare earth-based precursor powder is rare earth oxide, the surface coating modification includes dispersing Al2(OH)5Cl in deionized water to obtain a 5-10 wt% suspension, then adding a rare earth nitrate solution dropwise to the suspension, stirring until homogeneous, and then adding citric acid and ethylene glycol. The molar ratio of citric acid to rare earth ions is controlled at 1:1, and the amount of ethylene glycol added is 50% of the mass percentage of citric acid, and a gel is obtained. The pH of the gel is then adjusted to 3.0-4.0, and the temperature is controlled at 80℃ while stirring to obtain a gel. Finally, the gel is mixed with Al2(OH)5Cl solid particles, dried, and calcined. The calcination temperature is controlled at 500-700℃ and held for 1.5-2 hours to obtain a modified mixture of rare earth oxide coated Al2(OH)5Cl formed by gel decomposition.

[0045] When the high-purity, highly colloidal alumina powder is high-purity boehmite, the surface coating modification includes dispersing the high-purity boehmite in deionized water to obtain a 2-5 wt% suspension, adding a rare earth-based precursor to the suspension, controlling the amount of rare earth-based precursor added to be 3-15% of the mass percentage of the high-purity boehmite, adding urea, controlling the concentration of urea to be 0.5-1 mol / L, controlling the temperature to be 120-130℃, holding for 6-12 hours, cooling to room temperature, and then sequentially centrifuging, washing with ethanol, and drying, or sequentially centrifuging, washing with ethanol, and calcining to obtain the modified mixture.

[0046] Example 1

[0047] A method for preparing a rare earth composite solid electrolyte coating material includes the following steps:

[0048] Step 1: Modify solid high-purity, highly colloidal alumina powder with rare earth-based precursor powder. The rare earth element in the rare earth-based precursor powder is lanthanum, and a modified mixture is obtained.

[0049] Step 2: The modified mixture is subjected to acidification treatment and high-speed stirring dispersion in sequence. Hydrochloric acid is used in the acidification treatment and the acidification temperature is 20℃. The stirring speed of the high-speed stirring is 1000r / min and the stirring time is 5h. The pulping treatment temperature is controlled at 20℃, the pulping speed is 1000r / min and the pulping time is 5h to obtain the pulp.

[0050] Step 3: Add LATP solid electrolyte powder to the slurry and mix and slurry. Control the mixing mass ratio of high-purity, highly colloidal alumina powder, rare earth-based precursor powder and LATP solid electrolyte powder to 20:1:10 to obtain an ionic conductivity >10. -2 Coating material with a density of s / cm.

[0051] The modified mixture was obtained through surface coating modification.

[0052] In Example 1 of this application, the rare earth-based precursor powder is rare earth carbonate. The high-purity, highly colloidal alumina powder is Al2(OH)5Cl, and the surface coating modification includes dispersing Al2(OH)5Cl in deionized water to obtain a 5wt% suspension, then adding a rare earth salt solution, namely LaCl3, to the suspension while simultaneously adding a precipitant. After the addition is complete, the temperature is controlled at 60°C for water bath treatment for 4 hours, and after standing and aging for 10 hours, it is vacuum dried at 60°C to obtain a modified mixture of Al2(OH)5Cl coated with rare earth carbonate.

[0053] It should be mentioned that the precipitant in the embodiments of this application is an NH4HCO3 solution, and the pH is controlled at 6.0-7.0.

[0054] Example 2

[0055] A method for preparing a rare earth composite solid electrolyte coating material includes the following steps:

[0056] Step 1: Modify solid high-purity, highly colloidal alumina powder by combining it with rare earth-based precursor powder. The rare earth element in the rare earth-based precursor powder is cerium, and a modified mixture is obtained.

[0057] Step 2: The modified mixture is subjected to acidification treatment and high-speed stirring dispersion in sequence. Nitric acid is used in the acidification treatment and the acidification temperature is 40℃. The stirring speed of the high-speed stirring is 800 r / min and the stirring time is 3h. The pulping treatment temperature is controlled at 40℃, the pulping speed is 800 r / min and the pulping time is 3h to obtain the pulp.

[0058] Step 3: Add LATP solid electrolyte powder to the slurry and mix and slurry. Control the mixing mass ratio of high-purity, highly colloidal alumina powder, rare earth-based precursor powder and LATP solid electrolyte powder to be 55:11:27 to obtain an ionic conductivity >10. -2 Coating material with a density of s / cm.

[0059] The modified mixture was obtained through surface coating modification.

[0060] In Example 1 of this application, the rare earth-based precursor powder is rare earth oxalate. The high-purity, highly colloidal alumina powder is Al2(OH)5Cl, and the surface coating modification includes dispersing Al2(OH)5Cl in deionized water to obtain a 7wt% suspension, then adding a rare earth salt solution, namely Ce(NO3)3, to the suspension while simultaneously adding a precipitant. After the addition is complete, the temperature is controlled at 70°C and treated in a water bath for 3 hours. After standing and aging for 12 hours, the mixture is vacuum dried at 60°C to obtain a modified mixture of Al2(OH)5Cl coated with rare earth oxalate.

[0061] It should be mentioned that the precipitant in the embodiments of this application is a (NH4)2C2O4 solution, and the pH is controlled at 4.0-5.0.

[0062] Example 3

[0063] A method for preparing a rare earth composite solid electrolyte coating material includes the following steps:

[0064] Step 1: Modify solid high-purity, highly colloidal alumina powder with rare earth-based precursor powder. The rare earth element in the rare earth-based precursor powder is lanthanum, and a modified mixture is obtained.

[0065] Step 2: The modified mixture is subjected to acidification treatment and high-speed stirring dispersion in sequence. Phosphoric acid is used in the acidification treatment, and the acidification temperature is 60℃. The stirring speed of the high-speed stirring is 400 r / min and the stirring time is 0.25 h. The pulping treatment temperature is controlled at 60℃, the pulping speed is 400 r / min and the pulping time is 0.25 h to obtain the pulp.

[0066] Step 3: Add LATP solid electrolyte powder to the slurry and mix and slurry. Control the mixing mass ratio of high-purity, highly colloidal alumina powder, rare earth-based precursor powder and LATP solid electrolyte powder to 15:4:10 to obtain an ionic conductivity >10. -2 Coating material with a density of s / cm.

[0067] The modified mixture was obtained through surface coating modification.

[0068] In Example 1 of this application, the rare earth-based precursor powder is rare earth carbonate. The high-purity, highly colloidal alumina powder is Al2(OH)5Cl, and the surface coating modification includes dispersing Al2(OH)5Cl in deionized water to obtain a 10wt% suspension, then adding a rare earth salt solution, namely LaCl3, to the suspension while simultaneously adding a precipitant. After the addition is complete, the temperature is controlled at 80℃ and treated in a water bath for 2 hours. After standing and aging for 10-16 hours, the mixture is vacuum dried at 60℃ to obtain a modified mixture of Al2(OH)5Cl coated with rare earth carbonate.

[0069] It should be mentioned that the precipitant in the embodiments of this application is an NH4HCO3 solution, and the pH is controlled at 6.0-7.0.

[0070] Example 4

[0071] The difference between Example 4 and Example 2 is that the rare earth-based precursor powder in Example 4 is rare earth oxide. The surface coating modification includes dispersing Al2(OH)5Cl in deionized water to obtain a 5wt% suspension, then adding a rare earth nitrate solution dropwise to the suspension, stirring evenly, and then adding citric acid and ethylene glycol. The molar ratio of citric acid to rare earth ions is controlled at 1:1, and the amount of ethylene glycol added is 50% of the mass percentage of citric acid to obtain a gel. The pH of the gel is then adjusted to 3.0-4.0, and the temperature is controlled at 80℃ while stirring to obtain a gel. Finally, the gel is mixed with Al2(OH)5Cl solid particles, dried, and calcined. The calcination temperature is controlled at 500℃ and held for 2 hours to obtain a modified mixture of rare earth oxide coated Al2(OH)5Cl.

[0072] Example 5

[0073] The difference between Example 5 and Example 2 is that the rare earth-based precursor powder in Example 5 is rare earth oxide. The surface coating modification includes dispersing Al2(OH)5Cl in deionized water to obtain a 7wt% suspension, then adding a rare earth nitrate solution dropwise to the suspension, stirring evenly, and then adding citric acid and ethylene glycol. The molar ratio of citric acid to rare earth ions is controlled at 1:1, and the amount of ethylene glycol added is 50% of the mass percentage of citric acid to obtain a gel. The pH of the gel is then adjusted to 3.0-4.0, and the temperature is controlled at 80℃ while stirring to obtain a gel. Finally, the gel is mixed with Al2(OH)5Cl solid particles, dried, and calcined. The calcination temperature is controlled at 600℃ and held for 1.8 hours to obtain a modified mixture of rare earth oxide coated Al2(OH)5Cl formed by gel decomposition.

[0074] Example 6

[0075] The difference between Example 6 and Example 2 is that the rare earth-based precursor powder in Example 6 is rare earth oxide. The surface coating modification includes dispersing Al2(OH)5Cl in deionized water to obtain a 10wt% suspension, then adding a rare earth nitrate solution dropwise to the suspension, stirring until homogeneous, and then adding citric acid and ethylene glycol. The molar ratio of citric acid to rare earth ions is controlled at 1:1, and the amount of ethylene glycol added is 50% of the mass percentage of citric acid, and a gel is obtained. The pH of the gel is then adjusted to 3.0-4.0, and the temperature is controlled at 80℃ while stirring to obtain a gel. Finally, the gel is mixed with Al2(OH)5Cl solid particles, dried, and calcined. The calcination temperature is controlled at 700℃ and held for 1.5 hours to obtain a modified mixture of rare earth oxide coated Al2(OH)5Cl formed by gel decomposition.

[0076] Example 7

[0077] The difference between Example 7 and Example 2 is that the high-purity, highly colloidal alumina powder in Example 7 is high-purity boehmite. The surface coating modification includes dispersing high-purity boehmite in deionized water to obtain a 2wt% suspension, adding a rare earth-based precursor to the suspension, controlling the amount of rare earth-based precursor added to be 3-15% of the mass percentage of high-purity boehmite, adding urea, controlling the concentration of urea to be 0.5mol / L, controlling the temperature to be 120℃, holding for 12 hours, cooling to room temperature, and then sequentially centrifuging, washing with ethanol, and drying, or sequentially centrifuging, washing with ethanol, and calcining to obtain a modified mixture.

[0078] The washing process involved ethanol washing and drying at 80℃ for 6 hours; the calcination process involved calcination at 600℃ for 2 hours.

[0079] Example 8

[0080] The difference between Example 8 and Example 3 is that the high-purity, highly colloidal alumina powder in Example 8 is high-purity boehmite. The surface coating modification includes dispersing high-purity boehmite in deionized water to obtain a 3wt% suspension, adding a rare earth-based precursor to the suspension, controlling the amount of rare earth-based precursor added to be 9% of the mass percentage of high-purity boehmite, adding urea, controlling the concentration of urea to be 0.7mol / L, controlling the temperature to be 125℃, holding for 8 hours, cooling to room temperature, and then sequentially centrifuging, washing with ethanol, and drying, or sequentially centrifuging, washing with ethanol, and calcining to obtain a modified mixture.

[0081] The washing process involved ethanol washing and drying at 80℃ for 6 hours; the calcination process involved calcination at 600℃ for 2 hours.

[0082] Example 9

[0083] The difference between Example 9 and Example 4 is that the high-purity, highly colloidal alumina powder in Example 9 is high-purity boehmite. The surface coating modification includes dispersing high-purity boehmite in deionized water to obtain a 5wt% suspension, adding a rare earth-based precursor to the suspension, controlling the amount of rare earth-based precursor added to be 15% of the mass percentage of high-purity boehmite, adding urea, controlling the concentration of urea to be 1mol / L, controlling the temperature to be 130℃, holding for 6 hours, cooling to room temperature, and then sequentially centrifuging, washing with ethanol, and drying, or sequentially centrifuging, washing with ethanol, and calcining to obtain a modified mixture.

[0084] The washing process involved ethanol washing and drying at 80℃ for 6 hours; the calcination process involved calcination at 600℃ for 2 hours.

[0085] Comparative Example 1

[0086] The difference between Comparative Example 1 and Example 2 is that in Comparative Example 1, solid high-purity, highly colloidal alumina powder and rare earth-based precursor powder are directly mixed to obtain a mixture and then step 2 is continued.

[0087] Comparative Example 2

[0088] The difference between Comparative Example 2 and Example 4 is that the surface coating modification operation was repeated in Comparative Example 2 to obtain a modified mixture with a coating layer thickness of 65-75 nm.

[0089] Comparative Example 3

[0090] The difference between Comparative Example 3 and Example 7 is that Comparative Example 3 did not undergo acidification treatment.

[0091] Performance testing:

[0092] 1. Ionic conductivity test: The coating material is coated on the stainless steel current collector to obtain a dense electrode sheet. Based on the AC impedance spectroscopy (EIS) method, the test frequency is controlled at 1Hz-1MHz, the amplitude is 5mV, and the temperature is 25℃. The electrode sheet is sandwiched between two stainless steel electrodes to form a symmetrical cell for testing. The ionic conductivity is calculated according to the formula σ=L / (R×A).

[0093] 2. Chemical stability test: The coating material powder was immersed in a mixture of LATP solid electrolyte powder and carbonate electrolyte, sealed and left to stand at 60°C for 72 hours. The phase change of the coating material before and after immersion was analyzed by X-ray diffraction, or the particle dissolution, agglomeration or cracking was evaluated by scanning electron microscopy.

[0094] 3. Thermal stability test: The coating material powder is heated from room temperature to 800℃ in air at a rate of 10℃ / min, and the mass change (TG) and heat flow change (DTA) are recorded to analyze whether there is abnormal weight loss or exothermic peak.

[0095] 4. High-temperature impedance test: After the symmetrical cell is kept at 80℃ for 2 hours, the EIS test is repeated, and the ion conductivity retention rate (conductivity at 80℃ / conductivity at room temperature × 100%) is calculated to evaluate the performance stability at high temperature.

[0096] The performance test results are shown in Table 1 below.

[0097] Table 1 Performance Test Results

[0098]

[0099] Table 1 above shows that Examples 2 and 7 have excellent electrical conductivity, indicating that the CeO2 oxygen vacancy density formed after the decomposition of cerium oxalate is high, and the nanostructure of boehmite shortens the ion diffusion path. Example 5 achieves a coating layer with suitable crystallinity through a calcination temperature of 600℃, avoiding the problems of particle sintering due to excessively high temperature or incomplete crystallization due to excessively low temperature.

[0100] Meanwhile, based on Examples 2 and 5, it is evident that the cerium oxalate coating layer bonds more tightly with Al2(OH)5Cl, thereby effectively blocking ion interdiffusion. Example 2 exhibits the lowest weight loss rate and the highest high-temperature retention rate, indicating that the cerium oxalate coating layer forms stable Ce-O-Al bonds with high-purity, highly colloidal alumina, thus effectively inhibiting hydroxyl group removal and high-temperature phase transition.

[0101] In summary, this application provides a method for preparing a rare-earth composite solid electrolyte coating material. This method first involves composite high-purity, highly colloidal alumina, a rare-earth-based precursor, and LATP solid electrolyte powder to obtain the coating material. The three-dimensional framework structure of the LATP solid electrolyte powder provides a rapid migration channel for lithium ions. The rare-earth-based precursor lowers the energy barrier for lithium ion migration, promoting ion transfer at the interface between the LATP solid electrolyte powder and alumina, reducing interfacial impedance, and synergistically filling the voids between the LATP solid electrolyte powder particles with the high-purity, highly colloidal alumina to form a continuous ion conduction path, avoiding conduction interruptions caused by island effects—a highly efficient ion conduction network. Secondly, a uniform rare-earth compound layer is formed on the surface of the high-purity, highly colloidal alumina through rare-earth-based precursor coating modification. This eliminates the lattice mismatch between the high-purity, highly colloidal alumina and the LATP solid electrolyte powder, reducing lithium ion migration resistance at the interface. Furthermore, the high electronegativity of the rare-earth-based precursor synergistically adsorbs lithium ions, forming a locally high-concentration ion region, accelerating ion diffusion. In the acidification process, adjusting the slurry pH inhibits the agglomeration of high-purity, highly colloidal alumina and LATP solid electrolyte powder, improving dispersion uniformity. This reduces local concentration polarization and avoids the decrease in chemical stability caused by material aggregation. Simultaneously, the acidic environment enhances the bonding force between the rare-earth-based precursor and the high-purity, highly colloidal alumina, improving the integrity and chemical stability of the coating. The rare-earth-based precursor coating on the surface of the high-purity, highly colloidal alumina forms an effective physical barrier, preventing direct contact between the alumina and the cathode material, avoiding the formation of high-resistance reaction products, and buffering redox reactions at the electrode interface, reducing side reactions. Furthermore, the coating modification significantly improves the high-temperature resistance of the coating material, effectively preventing phase transitions in the high-purity, highly colloidal alumina at high temperatures. The strong bonds formed between the rare-earth-based precursor and the high-purity, highly colloidal alumina improve thermal conductivity, accelerate heat diffusion, and prevent local overheating.

[0102] The terms “first,” “second,” “third,” “fourth,” etc., used in this application (if applicable) are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, or apparatus that includes a series of steps or units is not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, or apparatus.

[0103] It should be noted that the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0104] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for preparing a rare earth composite solid electrolyte coating material, characterized in that, Includes the following steps: Step 1: Composite modification of solid high-purity, highly colloidal alumina powder with rare earth-based precursor powder to obtain modified mixture material; Step 2: The modified mixture is subjected to acidification and high-speed stirring dispersion in sequence to obtain a slurry; Step 3: Add LATP solid electrolyte powder to the slurry, mix and beat to obtain coating material; The rare earth-based precursor powder is rare earth oxide, rare earth carbonate, or rare earth oxalate; the rare earth element in the rare earth-based precursor powder is at least one of lanthanum, cerium, praseodymium, and neodymium; and the modified mixture is obtained through surface coating modification. The high-purity, highly colloidal alumina powder is Al2(OH)5Cl; the surface coating modification includes dispersing Al2(OH)5Cl in deionized water to obtain a 5-10 wt% suspension, and then adding a rare earth salt solution, namely LaCl3 or Ce, to the suspension. (NO3)3 and a precipitant is added dropwise simultaneously. After the addition is complete, the temperature is controlled at 60-80℃ for water bath treatment for 2-4 hours. After standing and aging for 10-16 hours, the mixture is vacuum dried at 60℃ to obtain a modified mixture of Al2(OH)5Cl coated with rare earth carbonate or rare earth oxalate; or the surface coating modification includes dispersing Al2(OH)5Cl in deionized water to obtain a 5-10wt% suspension, then adding a rare earth nitrate solution dropwise to the suspension, stirring evenly, and then adding citric acid and ethylene glycol. The molar ratio of citric acid to rare earth ions is controlled at 1:1, and the amount of ethylene glycol added is 50% of the mass percentage of citric acid to obtain a gel. The pH of the gel is then adjusted to 3.0-4.0, and the temperature is controlled at 80℃ while stirring to obtain a gel. Finally, the gel is solidified with Al2(OH)5Cl. The particles are mixed, dried, and calcined, with the calcination temperature controlled at 500-700℃ and held for 1.5-2 hours to obtain a modified mixture of rare earth oxide-coated Al2(OH)5Cl formed by gel decomposition; or the high-purity, highly colloidal alumina powder is high-purity boehmite; the surface coating modification includes dispersing high-purity boehmite in deionized water to obtain a 2-5 wt% suspension, adding a rare earth-based precursor to the suspension, controlling the amount of rare earth-based precursor added to be 3-15% of the mass percentage of high-purity boehmite, adding urea, controlling the concentration of urea to be 0.5-1 mol / L, then controlling the temperature at 120-130℃, holding for 6-12 hours, cooling to room temperature, and then sequentially centrifuging, washing with ethanol, and drying, or sequentially centrifuging, washing with ethanol, and calcining to obtain the modified mixture.

2. The method for preparing a rare earth composite solid electrolyte coating material according to claim 1, characterized in that: The acidification treatment is carried out using at least one of hydrochloric acid, sulfuric acid, phosphoric acid, or nitric acid; the acidification treatment temperature is 20-60℃, the high-speed stirring speed is 400-2000 r / min, and the stirring time is 0.25-5 h.

3. The method for preparing a rare earth composite solid electrolyte coating material according to claim 1, characterized in that: The pulping process is carried out at a temperature of 20-60℃, a pulping speed of 400-2000 r / min, and a pulping time of 0.25-5 h.

4. The method for preparing a rare earth composite solid electrolyte coating material according to claim 1, characterized in that: The mixing mass ratio of the high-purity, highly colloidal alumina powder, rare earth-based precursor powder, and LATP solid electrolyte powder is 40-75:2-20:20-40.

5. The method for preparing a rare earth composite solid electrolyte coating material according to claim 1, characterized in that: In step 3, an ionic conductivity > 10 is obtained. -2 Coating material with a density of s / cm.

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