Oxide electrolyte, preparation method thereof and solid-state battery

Abstract

The invention provides an oxide electrolyte, a preparation method thereof and a solid-state battery, and relates to the field of solid-state batteries. The preparation method comprises the following steps: performing first mixing on citric acid, a solvent and a lithium source to obtain a first mixture; performing second mixing on the first mixture, a lanthanum source and a zirconium source to obtain a second mixture; performing third mixing on the second mixture and ethylenediamine tetraacetic acid to obtain a third mixture; performing fourth mixing on the third mixture and ammonia water to obtain a fourth mixture; drying the fourth mixture to obtain dry gel; and sequentially carrying out pretreatment, grinding and sintering on the dry gel to obtain the oxide electrolyte. According to the preparation method, atomic-scale uniform mixing is realized through a double-chelating system with a specific sequence and proportion, and a targeted gradient sintering process is matched, so that the electrolyte material with excellent performance is obtained while the sintering temperature is remarkably reduced and lithium volatilization is inhibited.

Description

Technical Field

[0001] This application relates to the field of solid-state batteries, and more particularly to an oxide electrolyte, a method for preparing the same, and a solid-state battery. Background Technology

[0002] Lithium-ion batteries store and release electrical energy through the reversible insertion and extraction of lithium ions between the positive and negative electrodes. Their core structure includes a positive electrode (such as lithium cobalt oxide or ternary materials), a negative electrode (graphite or silicon-carbon), a liquid electrolyte (LiPF6 / carbonate solution), and a separator. Despite nearly 30 years of commercialization, liquid systems have inherent drawbacks, such as thermal runaway safety risks, energy density limitations, and interfacial side reactions between the electrolyte and highly active electrodes.

[0003] Solid-state batteries replace liquid systems with solid electrolytes, offering revolutionary and disruptive advantages: 1. Intrinsically safe: Non-flammable solid materials completely eliminate the risk of thermal runaway; 2. Leap in energy density: Compatible with lithium metal anodes (theoretical capacity 3860mAh / g) and 5V cathodes, with energy density expected to exceed 500Wh / kg; 3. Long lifespan potential: Suppressing dendrite growth and interfacial side reactions, resulting in a cycle life of >2000 cycles.

[0004] Among them, oxide solid electrolytes have high ionic conductivity (10) -5 -10 -3 With high S / cm, a wide electrochemical window (0-6V), and excellent oxidation stability, solid-state battery electrolytes have become the mainstream industrialization route. Garnet-type Li7La3Zr2O 12 (LLZO) has attracted much attention due to its unique advantages: 1. It is compatible with lithium metal, does not form dendrites, and is suitable for high energy density anodes; 2. Its electrochemical window is >6V, and it can be matched with a variety of positive and negative electrode materials; 3. It can provide three-dimensional ion channels, and its ionic conductivity can reach 2-4×10⁻⁴. -4 S / cm. Although LLZO is an ideal electrolyte for solid-state batteries, the huge differences in pH value caused by the hydrolysis precipitation of various metal ions, resulting in component segregation, and the lithium volatilization defects caused by high-temperature sintering, have led to its performance and mass production capabilities falling far short of theoretical expectations. Breakthroughs in atomic-level uniform synthesis and low-temperature densification processes have become the key to unlocking the commercialization of oxide solid-state batteries.

[0005] Therefore, developing a method for the coordinated control of the entire process from precursor molecular-level uniform design to sintering is an urgent problem to be solved in this field. Summary of the Invention

[0006] The purpose of this application is to provide an oxide electrolyte, a method for preparing the same, and a solid-state battery to solve the above-mentioned problems.

[0007] To achieve the above objectives, the first aspect of this application provides a method for preparing an oxide electrolyte, comprising: Citric acid, solvent, and lithium source are first mixed to obtain a first mixture; The first mixture, the lanthanum source, and the zirconium source are mixed a second time to obtain a second mixture; The second mixture and ethylenediaminetetraacetic acid are mixed in a third mixture to obtain a third mixture; The third mixture and ammonia water are then mixed in a fourth mixture to obtain a fourth mixture; The fourth mixture was dried to obtain a dry gel; The dry gel was pretreated, ground, and sintered in sequence to obtain an oxide electrolyte.

[0008] Optionally, the solvent includes water; And / or, the lithium source includes at least one of LiNO3·3H2O, LiCl and LiCH3COO; And / or, the lanthanum source includes at least one of La(NO3)3·6H2O, LaCl3, and La(CH3COO)3; And / or, at least one of the zirconium sources ZrO(NO3)2·5H2O, ZrOCl2 and ZrO(CH3COO)2·4H2O.

[0009] Optionally, the molar ratio of total metal ions, citric acid, and ethylenediaminetetraacetic acid in the second mixture is 12:18-24:12-18; And / or, the second mixture may also contain an aluminum source and / or a tantalum source; The aluminum source includes at least one of Al(NO3)3·9H2O, AlCl3·6H2O and Al(CH3COO)3; The tantalum source includes Ta(NO3)5·xH2O and / or TaCl5; The molar ratio of lithium in the lithium source, lanthanum in the lanthanum source, zirconium in the zirconium source, aluminum in the aluminum source, and tantalum in the tantalum source is 6.9-7:3:1.6-2:0-0.1:0-0.4.

[0010] Optionally, the temperatures of the first mixture, the second mixture, and the third mixture are each independently 80-90°C; And / or, the drying temperature is 90-100℃ and the time is 2-3h.

[0011] Optionally, the pH of the fourth mixture is 7.5-8.5.

[0012] Optionally, the pretreatment temperature is 200-250℃ and the time is 10-12h.

[0013] Optionally, the particle size of the ground dry gel is 10-20 μm.

[0014] Optionally, the sintering includes a first sintering and a second sintering performed sequentially; The heating rate of the first sintering is 4-5℃ / min, the final temperature is 850-950℃, and the holding time is 2-3h. The second sintering process involves a heating rate of 2-3℃ / min, an endpoint temperature of 1050-1150℃, and a holding time of 9-11h.

[0015] A second aspect of this application provides an oxide electrolyte, which is prepared by the method for preparing the oxide electrolyte.

[0016] A third aspect of this application provides a solid-state battery, including the aforementioned oxide electrolyte.

[0017] Compared with the prior art, the beneficial effects of this application include: The method for preparing the oxide electrolyte provided in this application involves first adding citric acid to combine with a lithium source, and then adding La. 3+ Zr 4+ High-valence ions and small-radius ions are combined, and finally ethylenediaminetetraacetic acid (EDTA) is added for chelation. This order is based on the differences in the acid dissociation constants (pKa) and complexation abilities of the two ions for different metal ions, achieving hierarchical and precise complexation of metal ions and suppressing segregation caused by different hydrolysis pH from the source. Based on the ultra-uniform precursor (dry gel) obtained by the above double chelation process, pretreatment is used to fully decompose and release residual organic matter such as citric acid, EDTA, and nitrates and water of crystallization in the dry gel, and then sintering is used to fully decompose the organic matter. This preparation method achieves atomic-level uniform mixing through a double chelation system with a specific sequence and ratio, and then matches it with a targeted gradient sintering process, which significantly reduces the sintering temperature and suppresses lithium volatilization while obtaining electrolyte materials with excellent performance.

[0018] The oxide electrolyte provided in this application exhibits excellent purity, density, and ionic conductivity. Its fundamental advantage lies in its systematic solution to the core contradiction in traditional methods—the difficulty in simultaneously achieving "compositional uniformity," "powder characteristics," and "low-temperature densification"—through collaborative innovation across the entire chain, from precursor design to sintering process. Electrolytes prepared by existing technologies often suffer from compositional segregation and impurity phases due to differences in the hydrolysis rates of metal ions. This application achieves precise and hierarchical complexation of metal ions with different valence states through a stepwise sequential chelation process using EDTA and citric acid, ensuring atomic-level mixing at the molecular source and thus obtaining a high-purity single-cubic-phase garnet structure. Existing technologies (such as solid-state methods) directly use micron-sized raw materials for mixing, resulting in coarse powders with poor uniformity. This leads to insufficient sintering driving force, necessitating high-temperature, long-time sintering to achieve densification, which exacerbates lithium volatilization and abnormal grain growth. This application utilizes a unique gelation and low-temperature pretreatment process to obtain fluffy, fine, and highly active nano / submicron-sized precursor powders. These fine powders possess higher specific surface area and sintering activity, laying the foundation for subsequent gradient sintering. Combined with a gradient process of "low-temperature pre-decomposition - medium-temperature pre-crystallization - high-temperature short-time sintering," the fine powders achieve uniform nucleation and growth of grains, driving an efficient and uniform densification process with a relatively lower overall thermal budget, ultimately yielding a highly dense ceramic body with uniform microstructure, clean grain boundaries, and low porosity.

[0019] The solid-state battery provided in this application effectively improves energy density and safety. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0021] Figure 1 This is a schematic flowchart of the preparation method of the oxide electrolyte provided in Example 1. Detailed Implementation

[0022] It is important to note that in existing technologies, the main approaches to improving the performance of LLZO fall into two categories: one is to enhance powder uniformity by optimizing precursor preparation (e.g., using a single citric acid complex); the other is to improve densification by optimizing the sintering process (e.g., using isothermal sintering). However, these two approaches are often studied in isolation. If only a single chelating agent is used, it is difficult to simultaneously achieve uniform dispersion of both high-valence and low-valence ions; if high-temperature sintering is used under the premise of insufficient powder uniformity, it may exacerbate lithium volatilization and impurity phase formation. Based on this, this application provides the following solution to address the above problems.

[0023] First, the solution provided in this application will be explained in more detail as follows: The first aspect of this application provides a method for preparing an oxide electrolyte, comprising: Citric acid, solvent, and lithium source are first mixed to obtain a first mixture; The first mixture, the lanthanum source, and the zirconium source are mixed a second time to obtain a second mixture; The second mixture and ethylenediaminetetraacetic acid are mixed in a third mixture to obtain a third mixture; The third mixture and ammonia water are then mixed in a fourth mixture to obtain a fourth mixture; It should be noted that Li + It is an alkali metal ion, and its binding constant (logK ≈ 2.8) with ethylenediaminetetraacetic acid (EDTA), a strong chelating agent, is very weak, making it difficult for EDTA to effectively complex it; while citric acid, under heating and specific pH conditions (acidic to neutral), can bind with Li. + To form a sufficiently stable soluble complex, citric acid is first used to "protect" the easily migrating but difficult-to-bind Li+. + This introduces a preliminary stabilizing network into the solution, preventing lithium segregation or loss in subsequent steps; furthermore, EDTA's chelating ability is fully realized in an alkaline environment (pH 7.5-8.5); La 3+ Zr 4+ Highly charged, small-radius ions are easily hydrolyzed, and their binding constant with EDTA is extremely high (logK>15). Therefore, EDTA needs to be added later and should be used in conjunction with a suitable pH environment. The above step sequence is based on the significant differences in the binding constants of different metal ions with different chelating agents, which realizes the hierarchical and precise complexation of all metal ions. This ensures the atomic-level uniformity of the precursor gel from the molecular source, which is the key to solving the problems of component segregation and lithium volatilization in the subsequent sintering process.

[0024] The fourth mixture was dried to obtain a dry gel; The dry gel was pretreated, ground, and sintered in sequence to obtain the oxide electrolyte.

[0025] It is important to note that directly sintering the dry gel to prepare solid electrolytes can lead to problems such as violent decomposition of organic matter causing material pulverization and cracking, loss of lithium source due to local overheating, and difficulty in obtaining a highly dense sintered body due to uneven internal stress. Therefore, it is necessary to pretreat the dry gel to obtain a fluffy first precursor. This step involves gentle and slow thermal decomposition, which allows residual organic matter such as citric acid, EDTA, and nitrates in the dry gel to be fully decomposed and released along with the water of crystallization, rather than exploding instantaneously at subsequent high temperatures. The fluffy first precursor obtained after pretreatment has a lower density and a higher specific surface area, forming a uniform nanoscale pore network inside. This structure not only greatly improves the efficiency of subsequent grinding and ensures uniform and fine powder, but more importantly, it provides optimized kinetic conditions for lithium ion diffusion, uniform grain nucleation and growth during subsequent gradient sintering. This effectively suppresses lithium volatilization and impurity phase formation caused by excessively rapid local densification, making it a key pretreatment step for obtaining high-purity, high-density, and high-performance LLZO ceramics.

[0026] It is also important to note that if the pretreated, porous first precursor is directly sintered at high temperatures to prepare solid electrolytes, it will face serious technical and efficiency bottlenecks in industrial production. This is because the first precursor is extremely porous and bulky, and directly loading it into the furnace will severely encroach on the effective sintering space, resulting in extremely low single-batch yield, significantly increased energy consumption, and production efficiency that cannot meet actual needs. Furthermore, its abundant pores and residual organic matter will instantly generate enormous pressure at high temperatures, easily causing the material to burst, pulverize, or even contaminate the furnace. The uneven heat transfer caused by its porous structure will also lead to inconsistent quality of the sintered body. Therefore, it is essential to… A crucial intermediate treatment is required for the fluffy first precursor: it is ground into a fine powder, loaded into a ceramic crucible, and then sintered. This step aims to achieve multiple optimization objectives: First, powdering significantly increases the packing density, enabling a substantial increase in single-furnace output and overcoming a core obstacle to production efficiency. Second, the pre-firing at 850-950℃ is a precise "decarburization and crystallization pretreatment" process, which completely decomposes residual organic matter (such as the carbon chains of citric acid and EDTA) in the precursor into gases and converts amorphous or low-crystallinity metal oxides into highly active nanocrystalline powders with the target lattice rudimentary structure. The resulting electrolyte second precursor is an active powder with highly uniform composition, a preliminary crystalline structure, and no carbon residue.

[0027] In some embodiments, the solvent includes water; And / or, the lithium source includes at least one of LiNO3·3H2O, LiCl and LiCH3COO; And / or, the lanthanum source includes at least one of La(NO3)3·6H2O, LaCl3, and La(CH3COO)3; And / or, at least one of the zirconium sources ZrO(NO3)2·5H2O, ZrOCl2 and ZrO(CH3COO)2·4H2O.

[0028] In some embodiments, the molar ratio of total metal ions, citric acid, and ethylenediaminetetraacetic acid in the second mixture is 12:18-24:12-18; Optionally, the molar ratio of total metal ions, citric acid and ethylenediaminetetraacetic acid in the second mixture can be any value between (12:18:12), (12:21:12), (12:24:12), (12:18:15), (12:18:18) or 12:18-24:12-18; In some embodiments, the total metal ions in the second mixture refer to the total molar amount of lithium in the lithium source, lanthanum in the lanthanum source, and zirconium in the zirconium source in the second mixture; in other embodiments, the total metal ions in the second mixture refer to the total molar amount of lithium in the lithium source, lanthanum in the lanthanum source, zirconium in the zirconium source, aluminum in the aluminum source, and / or tantalum in the tantalum source in the second mixture. And / or, the second mixture may also contain an aluminum source and / or a tantalum source; The aluminum source includes at least one of Al(NO3)3·9H2O, AlCl3·6H2O and Al(CH3COO)3; The tantalum source includes Ta(NO3)5·xH2O and / or TaCl5; The molar ratio of lithium in the lithium source, lanthanum in the lanthanum source, zirconium in the zirconium source, aluminum in the aluminum source, and tantalum in the tantalum source is 6.9-7:3:1.6-2:0-0.1:0-0.4.

[0029] Optionally, the molar ratio of lithium in the lithium source, lanthanum in the lanthanum source, zirconium in the zirconium source, aluminum in the aluminum source, and tantalum in the tantalum source can be any value between (7:3:2:0:0), (6.9:3:2:0.1:0), (7:3:1.6:0:0.4), (6.9:3:1.6:0.1:0.4), or 6.9-7:3:1.6-2:0-0.1:0-0.4.

[0030] In some embodiments, the temperatures of the first mixture, the second mixture, and the third mixture are each independently 80-90°C; Optionally, the temperatures of the first mixture, the second mixture, and the third mixture can each be independently 80°C, 85°C, 90°C, or any value between 80°C and 90°C; And / or, the drying temperature is 90-100℃ and the time is 2-3h.

[0031] Optionally, the drying temperature can be any value between 90℃, 95℃, 100℃ or 90-100℃, and the time can be any value between 2h, 2.5h, 3h or 2-3h.

[0032] In some embodiments, the pH of the fourth mixture is 7.5-8.5.

[0033] Optionally, the pH of the fourth mixture can be 7.5, 8, 8.5, or any value between 7.5 and 8.5.

[0034] It is important to note that EDTA, as a powerful chelating agent, has a chelating ability highly dependent on pH. Under acidic or neutral conditions, the carboxylate group of EDTA mostly exists in a protonated (-COOH) form, exhibiting very weak chelating ability. When the pH is adjusted to above 7.5, EDTA completely dissociates into Y. 4- Form, which is effective for high-valence metal ions (such as La). 3+ Zr 4+ The chelation constant of the ions reaches its maximum, enabling the formation of extremely stable and soluble complexes, thereby "locking" these ions at the molecular level and completely preventing their hydrolysis and precipitation.

[0035] In some embodiments, the pretreatment temperature is 200-250°C and the time is 10-12 hours.

[0036] Optionally, the pretreatment temperature can be any value between 200℃, 210℃, 220℃, 230℃, 240℃, 250℃ or 200-250℃, and the time can be any value between 10h, 11h, 12h or 10-12h.

[0037] In some embodiments, the particle size of the milled dry gel is 10-20 μm.

[0038] Optionally, the particle size of the milled dry gel can be any value between 10 μm, 15 μm, 20 μm, or 10-20 μm.

[0039] In some embodiments, the sintering includes a first sintering and a second sintering performed sequentially; The heating rate of the first sintering is 4-5℃ / min, the final temperature is 850-950℃, and the holding time is 2-3h. Optionally, the heating rate of the first sintering can be any value between 4℃ / min, 4.5℃ / min, 5℃ / min or 4-5℃ / min, the final temperature can be any value between 850℃, 900℃, 950℃ or 850-950℃, and the isothermal time can be any value between 2h, 2.5h, 3h or 2-3h. The second sintering process involves a heating rate of 2-3℃ / min, an endpoint temperature of 1050-1150℃, and a holding time of 9-11h.

[0040] Optionally, the heating rate of the second sintering can be any value between 2℃ / min, 2.5℃ / min, 3℃ / min or 2-3℃ / min, the final temperature can be any value between 1050℃, 1100℃, 1150℃ or 1050-1150℃, and the isothermal time can be any value between 9h, 10h, 11h or 9-11h.

[0041] It is worth noting that the ultra-uniform precursor obtained based on the above-mentioned double chelating agent process adopts a three-stage gradient sintering process of "low-temperature slow decomposition - medium-temperature pre-crystallization - high-temperature short-time densification". In particular, a key heat preservation platform is set at 850-950℃ to allow the organic matter to fully decompose and initially form crystal nuclei, laying the foundation for subsequent densification. Furthermore, slow heating suppresses Li volatilization, thereby synergistically resolving the contradiction between uniformity, lithium volatilization and densification.

[0042] A second aspect of this application provides an oxide electrolyte, which is prepared by the method for preparing the oxide electrolyte.

[0043] A third aspect of this application provides a solid-state battery, including the aforementioned oxide electrolyte.

[0044] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0045] Example 1 This embodiment provides an oxide electrolyte and its preparation method, the preparation process is as follows: Figure 1 As shown, the specific preparation steps are as follows: S1: Weigh the raw materials according to the molar ratio of citric acid monohydrate, lithium from the lithium source, lanthanum from the lanthanum source, zirconium from the zirconium source, and ethylenediaminetetraacetic acid (EDTA) in the ratio of 18:7:3:2:12. Pour the citric acid monohydrate into a beaker containing deionized water and stir it evenly with a magnetic stirrer at 90°C. Then add the lithium source LiNO3·3H2O to the beaker and stir evenly. Then add the lanthanum source La(NO3)3·6H2O and the zirconium source Zr(NO3)4·5H2O and stir at 90°C again. Then add ethylenediaminetetraacetic acid (EDTA) and stir at 90°C again to obtain a mixed solution. Add ammonia water to the mixed solution to adjust the pH of the solution to 8. Stir the mixed solution at 95°C for 3 hours to remove the solvent and obtain a dry gel. S2: The dry gel was placed in an oven at 250℃ and dried for 10 hours to obtain a fluffy first precursor. The fluffy first precursor was ground into powder (particle size 10-20μm). The first precursor powder was placed into a ceramic crucible and placed in a muffle furnace for the first sintering. It was pre-calcined at 900℃ for 2 hours to obtain the electrolyte second precursor. The pre-calcined second precursor was further ground and placed into a corundum crucible. It was placed in a muffle furnace and heated to 900℃ at 5℃ / min, and then heated to 1100℃ at 2℃ / min for the second sintering. It was calcined at 1100℃ for 10 hours to obtain the phased oxide electrolyte material.

[0046] The chemical formula of the prepared oxide electrolyte is Li7La3Zr2O 12 .

[0047] Example 2 The difference from Example 1 is that in step S1, when adding lanthanum source La(NO3)3·6H2O and zirconium source Zr(NO3)4·5H2O, Al(NO3)3·9H2O is also added, and the molar ratio of Li in lithium source, lanthanum in lanthanum source, zirconium in zirconium source and aluminum in aluminum source is 6.9:3:2:0.1. In step S2, the second sintering temperature is the final temperature of 1050°C.

[0048] The chemical formula of the prepared oxide electrolyte is Li 6.9 Al 0.1 La3Zr2O 12 .

[0049] Example 3 The difference from Example 1 is that in step S1, when adding lanthanum source La(NO3)3·6H2O and zirconium source Zr(NO3)4·5H2O, TaO(NO3)3·2H2O is also added, and the molar ratio of Li in lithium source, lanthanum in lanthanum source, zirconium in zirconium source and tantalum in tantalum source is 7:3:1.6:0.4. In step S2, the final temperature of the first sintering is 950°C, and the final temperature of the second sintering is 1150°C.

[0050] The chemical formula of the prepared oxide electrolyte is Li7La3Zr. 1.6 Ta 0.4 O 12 .

[0051] Example 4 The difference from Example 1 is that in step S1, when adding lanthanum source La(NO3)3·6H2O and zirconium source Zr(NO3)4·5H2O, Al(NO3)3·9H2O and TaO(NO3)3·2H2O are also added. The molar ratio of Li in the lithium source, lanthanum in the lanthanum source, zirconium in the zirconium source, aluminum in the aluminum source, and tantalum in the tantalum source is 6.9:3:1.6:0.1:0.4. And in step S2, the final temperature of the second sintering is 1050°C.

[0052] The chemical formula of the prepared oxide electrolyte is Li 6.9 Al 0.1 La3Zr 1.6 Ta 0.4 O 12 .

[0053] Example 5 The difference from Example 1 is that in step S2, the final temperature of the first sintering is 850°C.

[0054] Example 6 The difference from Example 1 is that in step S2, the final temperature of the first sintering is 950°C.

[0055] Comparative Example 1 The difference from Example 1 is that ethylenediaminetetraacetic acid (EDTA) is not added.

[0056] Comparative Example 2 The difference from Example 1 is that the first sintering step in step S2 is not performed.

[0057] Comparative Example 3 The difference from Example 1 is that in step S2, the final temperature of the first sintering is 800°C.

[0058] Comparative Example 4 The difference from Example 1 is that in step S2, the final temperature of the first sintering is 1000°C.

[0059] Comparative Example 5 The difference from Example 1 is that the oven treatment in step S2 is not performed.

[0060] Comparative Example 6 The difference from Example 1 is that the grinding in step S2 is not performed, and the fluffy first precursor is directly sintered.

[0061] Comparative Example 7 The difference from Example 1 is that citric acid monohydrate is not added in step S1.

[0062] The oxide electrolytes provided in the above embodiments and comparative examples were subjected to conductivity tests, and the specific test data are shown in Table 1.

[0063] Table 1 Conductivity Test

[0064] analyze: As demonstrated by the above tests, the "stepwise sequential double chelation-gradient sintering" preparation method provided in this application successfully yielded LLZO series oxide solid electrolytes with excellent comprehensive performance. The selection and synergistic effect of doping elements are key to improving performance in this scheme. Specifically, the ionic conductivity of the Al / Ta co-doped material (7.3 × 10⁻⁶) is... -4 The S / cm ratio reached its highest value, significantly outperforming single doping (Al doping: 4.5 × 10⁻⁶). -4 S / cm; Ta doping: 5×10 -4 S / cm) and undoped pure LLZO (4×10) -4 S / cm). Precise control of key processes throughout the entire process is the cornerstone of achieving high performance: data shows that the absence of any core step (such as double chelating agent, oven treatment, first sintering) or deviation of parameters from the optimal window (such as the first sintering temperature being 800℃) will result in significant performance degradation. o C or 1000 o C) will all lead to an order-of-magnitude or significant decrease in conductivity (for example, the lack of oven treatment in Comparative Example 5 caused the conductivity to plummet to 1.8 × 10⁻⁶). -6 (S / cm). This proves that the proposed solution is not a simple superposition of conventional steps, but a collaborative innovation system in which each link is tightly coupled and the parameters are mutually locked. Any simplification of the process or arbitrary change of the parameters cannot reproduce the excellent effect of this invention, thus fully demonstrating the non-obviousness and outstanding substantial progress of this technical solution.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0066] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing an oxide electrolyte, characterized in that, include: Citric acid, solvent, and lithium source are first mixed to obtain a first mixture; The first mixture, the lanthanum source, and the zirconium source are mixed a second time to obtain a second mixture; The second mixture and ethylenediaminetetraacetic acid are mixed in a third mixture to obtain a third mixture; The third mixture and ammonia water are then mixed in a fourth mixture to obtain a fourth mixture; The fourth mixture was dried to obtain a dry gel; The dry gel was pretreated, ground, and sintered in sequence to obtain the oxide electrolyte.

2. The method for preparing the oxide electrolyte according to claim 1, characterized in that, The solvent includes water; And / or, the lithium source includes at least one of LiNO3·3H2O, LiCl and LiCH3COO; And / or, the lanthanum source includes at least one of La(NO3)3·6H2O, LaCl3, and La(CH3COO)3; And / or, at least one of the zirconium sources ZrO(NO3)2·5H2O, ZrOCl2 and ZrO(CH3COO)2·4H2O.

3. The method for preparing oxide electrolyte according to claim 1, characterized in that, The molar ratio of total metal ions, citric acid, and ethylenediaminetetraacetic acid in the second mixture is 12:18-24:12-18; And / or, the second mixture may also contain an aluminum source and / or a tantalum source; The aluminum source includes at least one of Al(NO3)3·9H2O, AlCl3·6H2O and Al(CH3COO)3; The tantalum source includes Ta(NO3)5·xH2O and / or TaCl5; The molar ratio of lithium in the lithium source, lanthanum in the lanthanum source, zirconium in the zirconium source, aluminum in the aluminum source, and tantalum in the tantalum source is 6.9-7:3:1.6-2:0-0.1:0-0.

4.

4. The method for preparing the oxide electrolyte according to claim 1, characterized in that, The temperatures of the first mixture, the second mixture, and the third mixture are each independently 80-90°C; And / or, the drying temperature is 90-100℃ and the time is 2-3h.

5. The method for preparing the oxide electrolyte according to claim 1, characterized in that, The pH of the fourth mixture is 7.5-8.

5.

6. The method for preparing the oxide electrolyte according to claim 1, characterized in that, The pretreatment temperature is 200-250℃, and the time is 10-12h.

7. The method for preparing the oxide electrolyte according to claim 1, characterized in that, The particle size of the ground dry gel is 10-20 μm.

8. The method for preparing the oxide electrolyte according to any one of claims 1-7, characterized in that, The sintering includes a first sintering and a second sintering performed sequentially. The heating rate of the first sintering is 4-5℃ / min, the final temperature is 850-950℃, and the holding time is 2-3h. The second sintering process involves a heating rate of 2-3℃ / min, an endpoint temperature of 1050-1150℃, and a holding time of 9-11h.

9. An oxide electrolyte, characterized in that, It is prepared by the method for preparing oxide electrolyte according to any one of claims 1-8.

10. A solid-state battery, characterized in that, Includes the oxide electrolyte as described in claim 9.

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