Composite oxide solid electrolyte material and preparation method thereof

Abstract

The invention discloses a composite oxide solid electrolyte material and a preparation method thereof. The preparation method comprises the following steps: mixing nanocrystallized first oxide solid electrolyte powder, an electropositive surfactant and a first ball milling solvent, and carrying out ball milling to form a first dispersion liquid with positive charges; mixing the nanocrystallized second oxide solid electrolyte powder, an electronegative surfactant and a second ball milling solvent, and carrying out ball milling to form a second dispersion liquid with negative charges; the first dispersion liquid and the second dispersion liquid are mixed according to the mass ratio, self-assembly coating of the core-shell structure is induced in a liquid phase through the electrostatic attraction effect by means of opposite charges given by the electropositive surface active agent and the electronegative surface active agent, the surface of the first electrolyte is evenly coated with the second electrolyte, and core-shell structure dispersion liquid is formed; and carrying out shaping treatment on the core-shell structure dispersion liquid by adopting a spray drying method, and then carrying out heat treatment to obtain the composite oxide solid electrolyte material with the core-shell structure.

Description

Technical Field

[0001] The present invention relates to the technical field of solid electrolytes, and particularly to a composite oxide solid electrolyte material and a preparation method thereof. Background Art

[0002] The application of oxide-based solid electrolyte materials in high-safety and high-energy-density solid-state batteries has received wide attention. Common oxide electrolytes include LLZO (Li7La3Zr2O 12 ), LATP (Li 1.3 Al 0.3 Ti 1.7 (PO4)3), etc., which have good thermal stability, chemical stability, and a relatively wide electrochemical window. However, oxide electrolyte materials still have technical bottlenecks such as poor interfacial compatibility, low ionic conductivity, and severe particle agglomeration, which severely limit their application in actual battery systems.

[0003] Currently, in order to improve interfacial compatibility and ion migration performance, some studies have adopted surface coating or heterostructure strategies. However, the existing technologies have the following problems: a) The coating layer is often prepared by high-temperature sintering or deposition methods, with complex processes and prone to shell layer fracture or peeling; b) The binding property of the coating interface is poor, and the interfacial resistance is high, affecting the electrochemical performance; c) The powder particle size is large and the dispersibility is poor, and the uniformity of the prepared composite material is insufficient; d) Most processes are difficult to scale up, and the industrial application prospects are limited. For example, CN201710357553.6 uses surface modification after sintering, with problems such as uneven shell layer and interfacial stress concentration; the plasma coating method in CN201910527921.6 has high costs and difficult control.

[0004] Therefore, it is of great practical significance and application value to develop a new type of composite oxide solid electrolyte material with a nanoscale core-shell structure, strong interfacial bonding, high ionic conductivity, and simple process. Summary of the Invention

[0005] The purpose of the present invention is to provide a composite oxide solid electrolyte material and a preparation method thereof. By precisely regulating the surface charge behavior and particle assembly mechanism, not only the stable construction of the core-shell structure is realized, but also the key problems such as interface incompatibility, insufficient conductivity, and environmental sensitivity of oxide solid electrolytes are fundamentally solved, providing a reliable material solution for the development of high-performance solid-state batteries.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0007] A preparation method of a composite oxide solid electrolyte material, comprising the following steps:

[0008] S1. Mix the nano-sized first oxide solid electrolyte powder, positive surfactant, and the first ball-milling solvent, and ball-mill to form a positively charged first dispersion liquid;

[0009] S2. Mix the nano-sized second oxide solid electrolyte powder, negative surfactant, and the second ball-milling solvent, and ball-mill to form a negatively charged second dispersion liquid;

[0010] S3. Mix the first dispersion liquid and the second dispersion liquid according to the mass ratio, and utilize the opposite charges conferred by the positive surfactant and the negative surfactant to induce the self-assembly coating of the core-shell structure through electrostatic attraction in the liquid phase, so that the second electrolyte is uniformly coated on the surface of the first electrolyte to form a core-shell structure dispersion liquid;

[0011] S4. Perform shaping treatment on the core-shell structure dispersion liquid by spray drying method, and then perform heat treatment to obtain a composite oxide solid electrolyte material with a core-shell structure.

[0012] Preferably, the first oxide solid electrolyte is one or more of LLZO, LATP, LATSP, or LAGP.

[0013] Preferably, the second oxide solid electrolyte is one or more of LLZO, LZSP, LiNbO3, or their doped and modified materials.

[0014] Preferably, the positive surfactant is a cationic amine or quaternary ammonium salt compound. Preferably, it is cetyltrimethylammonium bromide (CTAB) or triethanolamine (TEA).

[0015] Preferably, the negative surfactant is an anionic carboxylate, sulfonate, or phosphate ester salt. Preferably, it is sodium stearate or sodium dodecyl sulfonate.

[0016] Preferably, the mass ratio of the positive surfactant to the first electrolyte powder is 1:100 - 1:5, and the mass ratio of the negative surfactant to the second electrolyte powder is 1:150 - 1:10.

[0017] Preferably, the outlet temperature of the feed liquid in the spray drying process is 100°C - 130°C, and the atomization frequency is 250Hz - 400Hz.

[0018] Preferably, the heat treatment process in step S4 is carried out in an inert atmosphere, the heat treatment temperature is 600°C - 800°C, the holding time is 5 - 10h, the heating rate is 0.5°C / min - 3°C / min, and natural cooling is used for cooling after heat treatment.

[0019] A composite oxide solid electrolyte material prepared by the above method, which is a granular powder with an average particle size D50 of less than 500 nm and a shell layer thickness of 10 - 50 nm.

[0020] Compared with the prior art, the advantages of the present invention are as follows:

[0021] 1. By introducing cationic / anionic modifiers with uniform particle size and surface activity, the surface of the first solid electrolyte particles is positively charged, and the surface of the second solid electrolyte particles is negatively charged. After mixing, a core-shell coating structure is spontaneously and directionally formed in the liquid phase system by means of electrostatic attraction. On the basis of maintaining the high ionic conductivity of the core, this structure can optimize the shell interface, reduce the charge transfer impedance, and significantly improve the ionic conductivity of the overall electrolyte.

[0022] 2. Since the coating layer is self-assembled at the nanoscale, its structure is dense and firmly attached, which can effectively alleviate the problems of shell peeling and stress stripping commonly seen in the traditional mechanical mixing coating method. The interfacial bonding strength between the coating layer and the core material is high, which can inhibit the solid-solid interface reaction and the generation of by-products, and improve the contact stability between the electrolyte and the lithium metal negative electrode.

[0023] 3. Oxides such as LATSP in the shell layer material itself have high chemical stability, which can effectively isolate environmental pollutants such as moisture and CO2 from direct contact with the electrolyte core, thereby inhibiting the degradation reaction of air-sensitive materials such as LLZO in the core, and improving the adaptability of the material to the storage and processing environment. The shell layer structure can be evenly distributed on the surface of the lithium negative electrode, acting as a buffer interface to inhibit local high electric field concentration, and at the same time forming an interfacial stable layer (SEI layer), effectively preventing dendrite piercing and reducing side reactions during lithium deposition, and improving the battery cycle life and safety. The core-shell structure design in the present invention, especially the synergistic effect of the shell layer material selection and the surface modifier, effectively buffers the chemical mismatch between the lithium negative electrode and the electrolyte. The phosphate shell layer (such as LATSP) forms a stable interfacial passivation film at the lithium interface, inhibits the occurrence of side reactions, and delays the deterioration of the interfacial structure, thereby significantly improving the capacity retention rate and interfacial stability of the battery during long-term cycling.

[0024] 4. Traditional oxide electrolytes, such as LLZO, are easily reacted with H2O and CO2 in the air to form low-conductivity by-products (such as Li2CO3 and LiOH), resulting in a decrease in ionic conductivity and interfacial contact failure. In the present invention, through the complete coating of the shell layer material and the introduction of surfactants such as stearate and primary amine salt during the preparation process, a hydrophobic protective layer is formed on the surface of the electrolyte, greatly improving its stability in the air. This protective layer can effectively shield the penetration of moisture and oxygen, delay material deterioration, and improve the storability and processing adaptability of the material.

[0025] 5. This application first proposes to adopt the electrostatic self-assembly mechanism to precisely control the assembly process of the core-shell structure by utilizing the interaction of surface charges. Compared with traditional synthesis methods, this method has significant advantages in terms of structural regulation and material property improvement, enabling more precise structural control and performance optimization. By adopting electrostatic self-assembly and specific surface modification techniques, this application doubles the improvement of the interfacial stability and ionic conductivity of the material. Electrostatic self-assembly can regulate the fineness of the core-shell structure at the microscale, thereby achieving better interfacial matching and optimization of ionic conduction channels. Brief Description of the Drawings

[0026] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art.

[0027] Figure 1 It is the SEM image of the LATSP / LLZO core-shell structure composite material in the present invention. Detailed Description of the Embodiments

[0028] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the drawings.

[0029] Example 1

[0030] A preparation method of a composite oxide solid electrolyte material, comprising the following steps:

[0031] S1. Take the nanosized first oxide solid electrolyte powder lithium aluminum titanium phosphate (LATSP) as the "core" material, and add it together with the ball-milling solvent deionized water into a ball mill for mixing. At the same time, add a primary amine salt to the mixture, control its mass ratio with LATSP to be 1:100, and ball mill at 300 rpm for 4 hours. During the ball-milling process, the primary amine salt adsorbs on the LATSP particles, making the particle surface carry a positive charge, and obtaining a first suspension dispersion.

[0032] S2. Take the nanosized second oxide solid electrolyte powder lithium lanthanum zirconium oxide (LLZO) as the "shell" layer material, mix it with deionized water and then add it to a ball mill for ball-milling treatment. At the same time, add a carbonate (with the same mass ratio of 1:100), and ball mill at 300 rpm for 4 hours to form LLZO colloidal particles with a negatively charged surface, obtaining a second dispersion.

[0033] S3. Slowly mix the first dispersion liquid and the second dispersion liquid at a mass ratio of 1:10, maintain the stirring rate at 300 rpm, and stir for 5 hours. During the mixing process, in the liquid phase system, the electrostatic attraction between core-shell particles with opposite charges is utilized to achieve spontaneous, orderly, and directional coating between particles, forming a stable core-shell structure composite slurry. This process does not require an additional interfacial agent or external force guidance, and has high assembly uniformity and self-limitation.

[0034] S4. Input the obtained slurry into a spray drying device, set the atomization centrifugal frequency to 380 Hz, and the outlet temperature to 110 °C for drying treatment. The dried powder is heat-treated at 700 °C (heating rate 5 °C / min, holding for 7 hours) to complete the crystal structure optimization and shell densification, and finally obtain a core-shell structure composite oxide solid electrolyte material with LLZO coated on LATSP.

[0035] The material prepared in this example combines the advantages of LLZO and LATSP. The core-shell interface is naturally formed by electrostatic self-assembly, with a dense structure, continuous interface, and no obvious interface defects or reaction layers, effectively inhibiting the penetration of lithium dendrites and interface debonding phenomena, and significantly improving its cycle stability and safety in the solid-state lithium metal battery system.

[0036] To ensure that there is a strong enough electrostatic attraction between particles during the self-assembly process, the charge density on the particle surface should reach a certain level. Usually, a surface potential of several hundred to several thousand mV is required on the surface of nanoparticles. For example, the surface charge of particles can be achieved by adding an appropriate amount of surface modifiers (such as amino groups, carboxyl groups, etc.). The concentration of commonly used surface modifiers is generally 0.1% - 1% in mass ratio to ensure that the particle surface obtains sufficient charge. To ensure the effectiveness of electrostatic interaction, the particle size is usually selected in the range of 10 nm to 200 nm. Too large a particle size may result in too small an electrostatic force between particles, while too small a particle size may lead to uneven dispersion, affecting the self-assembly effect.

[0037] Electrostatic self-assembly usually requires a low ionic strength of the solution to avoid charge screening. Deionized water or an aqueous solution with a low ionic strength (such as the concentration of NaCl solution not exceeding 1 mM) is often used to ensure the electrostatic attraction between particles. The pH value is usually selected to be neutral or weakly alkaline (pH = 7 - 9), and the surfactant shows good charge stability within this pH range. The stirring rate is generally controlled at 300 rpm to avoid too violent particle collisions caused by too fast stirring, while too slow stirring may lead to uneven self-assembly. The mixing time is generally controlled for 3 - 6 hours to ensure full contact between particle surfaces and achieve stable electrostatic adsorption.

[0038] Example 2

[0039] A preparation method of a composite oxide solid electrolyte material, comprising the following steps:

[0040] S1. Take lithium aluminum titanium phosphate (LATP) powder, add it to a ball mill together with deionized water, and at the same time add a primary amine salt, control the mass ratio to be 1:100, and ball mill for 4 hours at 300 rpm to form a first dispersion.

[0041] S2. Take lithium zirconium silicate phosphate (LZSP) powder after nanocrystallization, add deionized water and mix it with a carbonate, control the mass ratio to be 1:100, and ball mill for 4 hours at 300 rpm to form a second dispersion which is a stable anionic colloid dispersion system.

[0042] S3. Mix the first dispersion and the second dispersion according to a mass ratio of 1:5 and stir for 5 hours. During the liquid-phase mixing process, by virtue of the electrostatic attraction formed by the surface heterocharge between the core particles and the shell particles, induce the LZSP particles to spontaneously adsorb on the surface of the LATP particles to form a nanoscale core-shell structure. This process has high selectivity and directionality, and a high assembly efficiency, and finally forms a uniform core-shell structure composite slurry.

[0043] S4. Spray-dry this slurry (390 Hz, 110 °C), and then perform heat treatment (600 °C, heating rate 5 °C / min, holding for 7 hours) to complete crystallization and structure stabilization, and obtain an LZSP-coated LATP core-shell type electrolyte material with excellent interfacial compatibility and ionic conduction channel continuity.

[0044] This material effectively combines the ionic conductivity of LATP and the interfacial stability of LZSP. The electrostatic self-assembly mechanism provides a flexible and cooperative interfacial connection structure, significantly reducing the interfacial resistance and the generation tendency of the interfacial reaction layer, and is for the cooperative design of oxide-oxide.

[0045] Example 3

[0046] A preparation method of a composite oxide solid electrolyte material, comprising the following steps:

[0047] S1. Take lithium germanium aluminum phosphate (LAGP) powder after nanocrystallization, add deionized water and a primary amine salt (mass ratio 1:100), and ball mill in a ball mill at 300 rpm for 4 hours to obtain a positively charged first dispersion.

[0048] S2. Take lithium zirconium silicate phosphate (LZSP) powder, add a carbonate for surface modification treatment to form a second dispersion with a negatively charged surface.

[0049] S3. Mix the two suspensions according to a mass ratio of 1:3 and stir for 5 hours. During this process, the anionic LZSP particles spontaneously adsorb on the surface of LAGP by means of a charge-driven mechanism, and uniform coating is completed at the nanoscale. The formed core-shell structure has a high specific surface area and multi-channel ion transport characteristics, and can effectively buffer the interfacial contact stress.

[0050] S4. Spray drying and heat treatment at 800 °C (heating rate 5 °C / min, holding for 7 hours) were used to complete the physical structure fixation and shell layer sintering densification, and an ultrafine composite electrolyte powder of LZSP-coated LAGP was prepared.

[0051] This material has a fine structure and a tight interface, is suitable for high-power and long-life solid-state battery systems, and exhibits excellent electrochemical stability and thermal compatibility under high-temperature conditions.

[0052] Example 4

[0053] A preparation method of a composite solid electrolyte material includes the following steps:

[0054] S1. Take lithium aluminum titanium phosphate LATP powder, add stearate (mass ratio 1:100) and deionized water, and carry out ball milling for 4 hours to achieve surface modification and dispersion to obtain a first dispersion liquid.

[0055] S2. Take LLZO powder, and carry out ball milling for 4 hours after adding a carbonate modifier (mass ratio 1:100) to form a second dispersion liquid.

[0056] S3. Mix the core-shell suspension in a 1:1 mass ratio. During the 5-hour stirring process, utilize the electrical complementarity between particles to drive LLZO to assemble on the surface of LATP to form a core-shell structure. This self-assembly method can significantly reduce the problems of agglomeration and interface discontinuity during the assembly process.

[0057] S4. After spray drying (390 Hz, 110 °C) and heat treatment at 750 °C (holding for 7 hours), a core-shell type LLZO@LATP solid electrolyte material with a uniform structure, dense particles, and stable interface is obtained.

[0058] Compared with the traditional composite process, this method can accurately control the coating thickness and core-shell ratio at the nanoscale, and has obvious advantages in large-scale preparation and interface corrosion resistance.

[0059] Comparative Example 1

[0060] Take nanosized first solid electrolyte powder lithium aluminum titanium phosphate LATP, add it to a ball mill together with the ball milling solvent deionized water for mixing. At the same time, add a cationic surface modifier stearate to the mixture to ensure that the mass ratio of stearate to LATP is 1:100, and carry out ball milling for 4 hours at a rotation speed of 300 rpm to make it fully mixed to form a suspension. Feed the mixed slurry into a spray drying device, set the inlet centrifugal frequency at 380 Hz and the outlet temperature at 110 °C, and carry out spray drying treatment. The dried powder needs to be heat treated, set the heat treatment temperature at 700 °C, hold for 7 h, and the heating rate is 5 °C / min. Finally, lithium aluminum titanium phosphate LATP material is obtained.

[0061] The method for performing the stability test in contact with lithium metal is as follows: The solid electrolyte powder in the examples is pressed into a sheet-shaped solid electrolyte with a diameter of 13 mm and a thickness of 2 mm under a pressure condition of 200 MPa and then subjected to high-temperature sintering. In a glove box filled with argon, the oxide solid electrolyte in the examples is placed inside a 2032-type battery case to ensure that its surface is in contact with the lithium tab. Subsequently, the temperature of the heating stage is adjusted to 200 °C and maintained at this temperature for up to 30 minutes.

[0062] Table 1 shows the results of the lithium metal stability tests for the electrolyte materials of each example and comparative example.

[0063] Reaction with lithium metal Phase change after contact with lithium metal Example 1 No reaction No change Example 2 No reaction No change Example 3 No reaction No change Example 4 No reaction No change Comparative Example 1 Reaction Change

[0064] When this core-shell structured composite solid electrolyte is applied in materials, due to the existence of the core-shell structure, the interfacial stability between the solid electrolyte and lithium metal is ensured. At the same time, its preparation method is relatively simple and suitable for large-scale production.

[0065] Finally, it should be noted that: The above examples are only used to illustrate the technical solutions of the present invention and are not intended to limit them; Although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that: They can still modify the technical solutions described in the foregoing examples, or perform equivalent replacements on some or all of the technical features; And these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of each example of the present invention.

Claims

1. A method for preparing a composite oxide solid electrolyte material, characterized in that: The steps include: S1, mixing a nanosized first oxide solid electrolyte powder, a positively charged surfactant and a first ball milling solvent, and ball milling to form a first dispersion liquid with a positive charge; S2, mixing the nanosized second oxide solid electrolyte powder, the negatively charged surfactant and the second ball milling solvent, and ball milling to form a negatively charged second dispersion; S3, mixing the first dispersion and the second dispersion according to a mass ratio, using the opposite charges given by the positively charged surfactant and the negatively charged surfactant to induce the self-assembly coating of the core-shell structure in the liquid phase through electrostatic attraction, so that the second electrolyte is evenly coated on the surface of the first electrolyte to form a core-shell structure dispersion; S4. The core-shell structure dispersion liquid is subjected to a shaping treatment by a spray drying method, and then subjected to a heat treatment to obtain a composite oxide solid electrolyte material having a core-shell structure.

2. The method for preparing a composite oxide solid electrolyte material according to claim 1, characterized in that: The first oxide solid electrolyte is one or more of LLZO, LATP, LATSP or LAGP.

3. The method for preparing a composite oxide solid electrolyte material according to claim 1, characterized in that: The second oxide solid electrolyte is one or more of LLZO, LZSP, LiNbO3 or doped and modified materials thereof.

4. The method for preparing a composite oxide solid electrolyte material according to claim 1, characterized in that: The positively charged surfactant is a cationic amine or quaternary ammonium salt compound.

5. The method for preparing a composite oxide solid electrolyte material according to claim 1, characterized in that: The negatively charged surfactant is an anionic carboxylate, sulfonate or phosphate salt.

6. The method for preparing a composite oxide solid electrolyte material according to claim 1, characterized in that: The mass ratio of the positively charged surfactant to the first electrolyte powder is 1:100 to 1:5, and the mass ratio of the negatively charged surfactant to the second electrolyte powder is 1:150 to 1:

10.

7. The method for preparing a composite oxide solid electrolyte material according to claim 1, characterized in that: The outlet temperature of the feed liquid in the spray drying process is 100° C. to 130° C., and the atomization frequency is 250 Hz to 400 Hz.

8. The method for preparing a composite oxide solid electrolyte material according to claim 1, characterized in that: The heat treatment process in step S4 is carried out under an inert atmosphere, the heat treatment temperature is 600°C to 800°C, the holding time is 5-10h, the heating rate is 0.5°C / min to 3°C / min, and the temperature is lowered by natural cooling after the heat treatment.

9. A composite oxide solid electrolyte material prepared by the method according to any one of claims 1 to 8, characterized in that: The prepared composite oxide solid electrolyte material is a granular powder with an average particle size D50 less than 500nm and a shell thickness of 10nm to 50nm.

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