A doped LLZO solid-state electrolyte material and a preparation method thereof

Abstract

The application provides a doped LLZO solid electrolyte material, characterized in that the chemical general formula of the doped LLZO solid electrolyte material is Li 7‑x Al x La3Zr 2‑y M y O 12 , wherein 0.04<=x<=0.30, M is one or a combination of multiple of Fe, Ti and Si, and 0.06<=y<=0.85. The application also provides a preparation method of the doped LLZO solid electrolyte material. The doped LLZO solid electrolyte material has high ionic conductivity through multi-element synergistic doping, and the preparation method helps to reduce the cost of raw materials.

Description

Technical Field

[0001] This invention relates to the field of inorganic solid electrolyte materials technology, specifically to a doped LLZO solid electrolyte material and its preparation method. Background Technology

[0002] With increasing demands for safety and energy density in lithium batteries, solid-state electrolyte materials have become a research hotspot due to their high stability and energy density. Among them, garnet-type lithium lanthanum zirconium oxide (LLZO) solid-state electrolytes are considered to be highly promising materials due to their high ionic conductivity and good chemical stability. However, traditional LLZO solid-state electrolyte materials require high-purity zirconium oxide (ZrO2) as the zirconium source. Although this can achieve high phase purity and ionic conductivity, the raw material price is expensive, making it difficult to meet industrialization requirements.

[0003] In addition, previous studies have shown that elemental doping (such as Al, Ga, Fe, Ti, Si, etc.) can improve the ionic conductivity of LLZO solid electrolyte materials and promote the formation of cubic phases. However, the introduction of these elements often depends on additional high-purity dopants, which increases the complexity and cost of the process.

[0004] Therefore, how to reduce raw material costs and stably obtain high-performance cubic phase LLZO solid electrolyte materials is an urgent problem to be solved. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a doped LLZO solid electrolyte material and its preparation method. This doped LLZO solid electrolyte material exhibits high ionic conductivity through multi-element synergistic doping, and its preparation method helps to reduce raw material costs. The technical solution adopted is as follows:

[0006] A doped LLZO solid electrolyte material, characterized in that the chemical formula of the doped LLZO solid electrolyte material is Li. 7-x Al x La3Zr 2-a-b-c Fe a Ti b Si c O 12 , where 0.04≤x≤0.30, 0.01≤a≤0.30, 0.01≤b≤0.39, 0.04≤c≤0.35, and 0.06≤a+b+c≤0.85.

[0007] The main mechanisms of action of this invention are: 1. Doping mechanism: Al 3+ Primarily occupying Li sites, forming Li vacancies, which is conducive to the formation of a stable cubic phase structure; Fe 3+ Si 4+ and Ti4+ It can partially replace Zr 4+ 1. **Site formation:** On the one hand, it induces lattice distortion, forming more migration channels; on the other hand, it maintains charge balance and promotes the stable existence of Li⁺ migration channels. 2. **Phase stability mechanism:** The synergistic effect of quaternary doping can effectively suppress the formation of tetragonal phase and stabilize the garnet-type cubic phase (Ia-3d space group), thereby significantly improving room temperature ionic conductivity. 3. **Microstructure mechanism:** Moderate Fe / Ti content helps improve sintering activity and densification, resulting in more uniform particle size distribution, which is beneficial for reducing grain boundary impedance and forming continuous lithium-ion conduction channels.

[0008] In a preferred embodiment, the Zr contained in the doped LLZO solid electrolyte material is derived from fused zirconium oxide.

[0009] This invention also provides a method for preparing the above-mentioned doped LLZO solid electrolyte material, characterized by comprising the following steps in sequence:

[0010] (1) Based on the general chemical formula Li 7-x Al x La3Zr 2-a-b-c Fe a Ti b Si c O 12 Where 0.04≤x≤0.30, 0.01≤a≤0.30, 0.01≤b≤0.39, 0.04≤c≤0.35, and 0.06≤a+b+c≤0.85;

[0011] The raw materials are prepared according to the stoichiometric ratio specified in the general chemical formula: lithium carbonate (Li2CO3) is used as the lithium source; lanthanum oxide (La2O3) is used as the lanthanum source; and fused zirconium oxide is used as the zirconium source, with a ZrO2 content of not less than 98 wt% and containing one or more of the impurities Al2O3, Fe2O3, TiO2, and SiO2. Based on the existing Al2O3, Fe2O3, TiO2, and SiO2 content in the fused zirconium oxide, the difference is calculated, and one or more of the dopants Al2O3, Fe2O3, TiO2, and SiO2 are added.

[0012] (2) The lithium carbonate, lanthanum oxide, fused zirconium oxide and dopant prepared in step (1) are added to the ball milling equipment for the first wet ball milling; after the first wet ball milling is completed, the slurry is dried to obtain a uniformly mixed powder.

[0013] (3) The mixed powder obtained in step (2) is subjected to mineralization treatment to obtain a block;

[0014] (4) After cooling the block obtained in step (3), crush it and then perform a second wet ball milling to obtain powder;

[0015] (5) After the powder obtained in step (4) is mixed evenly with the binder, it is pressed into shape to obtain a blank;

[0016] (6) Sinter the blank obtained by pressing in step (5) to obtain the desired doped LLZO solid electrolyte material.

[0017] The preferred chemical composition of the fused zirconium oxide used in step (1) is: ZrO2 ≥ 98 wt%, Fe2O3 ≤ 0.1 wt%, TiO2 ≤ 0.3 wt%, Al2O3 ≤ 0.4 wt%, SiO2 ≤ 1.2 wt%. The amount of impurities in fused zirconium oxide other than Al, Fe, Ti, and Si is very small, usually less than 10 ppm, and does not need to be removed before use (it can be ignored during metering).

[0018] In preferred step (2), the lithium carbonate, lanthanum oxide, fused zirconium oxide, and dopant prepared in step (1) are added to a ball mill (such as a polypropylene ball mill jar, ball milled under sealed conditions at room temperature) for mixing and ball milling. During the ball milling process, zirconium oxide ceramic balls with a diameter of 2 mm and zirconium oxide ceramic balls with a diameter of 5 mm are used as the ball milling media. The mass ratio of the 2 mm zirconium oxide ceramic balls to the 5 mm zirconium oxide ceramic balls is 4:1-2:1, the ball-to-material ratio is 8:1-15:1, isopropanol is used as the dispersion solvent, and the ball milling time is 3-12 hours. The first wet ball milling is used to ensure that the raw materials are uniformly mixed.

[0019] In preferred step (2), the slurry is dried at 80–100°C.

[0020] The mineralization process in step (3) aims to promote the formation of crystalline phases in the precursor and generate cubic LLZO with high phase purity, providing a structural basis for the subsequent sintering in step (6).

[0021] In preferred step (3), the mixed powder obtained in step (2) is placed in an air atmosphere for mineralization treatment. The mineralization treatment uses a magnesium oxide crucible as a reaction vessel. The reaction vessel and the mixed powder inside it are heated from room temperature to 950–1050℃, and the heating rate is controlled at 2.5–3.5℃ / min. Then, it is kept at 950–1050℃ for 6–9 hours.

[0022] In the preferred step (4), the second wet ball milling uses zirconia balls with a particle size of 0.5 mm as the milling medium, with a ball-to-material ratio of 8:1-15:1, isopropanol as the dispersion solvent, and a milling time of 3-12 hours. The purpose of the second wet ball milling process in step (4) is to further refine the particles and achieve particle size uniformity, ultimately obtaining ultrafine powder with a D50 particle size of approximately 0.5-2 μm (the powder is dried and sieved after ball milling).

[0023] In step (5), the amount of adhesive used is 2-5 wt% of the powder. The adhesive can be an aqueous solution of polyvinyl alcohol or an acrylic emulsion. Preferably, an aqueous solution of polyvinyl alcohol with a mass percentage concentration of 3.5-4.5% or an acrylic emulsion with a mass percentage concentration of 4-5% is used.

[0024] The preferred step (5) pressing process is as follows: First, a molding process is used to apply a pressure of 20–30 MPa to press the mixture of powder and binder into a sheet blank; then, the sheet blank is subjected to isostatic pressing (preferably held at a pressure of 200–400 MPa for 2–5 minutes). Isostatic pressing can further improve the density of the blank. The final blank has a thickness of about 1 mm and a diameter of about 10–15 mm, providing a good dense structural foundation for subsequent sintering.

[0025] In preferred step (6), the blank obtained by pressing in step (5) is placed in a magnesium oxide crucible and sintered in an air atmosphere. The sintering process uses a heating rate of 1-5℃ / min to heat the magnesium oxide crucible and the blank inside it from room temperature to 1150–1230℃, and then holds at 1150–1230℃ for 8–12 hours. The purpose of sintering is to achieve material densification and perfect crystal structure.

[0026] In step (6), in order to prevent the evaporation of lithium at high temperature, it is preferable to cover the surface of the blank with LLZO embedded powder with the same composition as the blank. The LLZO embedded powder can be prepared from LLZO powder with the same formula (e.g., the powder obtained in step (4)) to effectively protect the composition and structural stability of the doped LLZO solid electrolyte material.

[0027] Step (6) After sintering, the material (such as sheet-like doped LLZO solid electrolyte material) undergoes post-processing and performance testing. First, the material surface is polished to obtain a smooth test interface. Silver paste is evenly brushed onto both sides of the material and dried at 80-120℃ for 30 minutes to form good contact electrodes. Then, an AC impedance spectroscopy instrument is used at room temperature with a frequency range of 1 MHz to 1 Hz and an amplitude of 10 mV to test the total ionic conductivity of the material, thereby determining its ionic conductivity performance. The above experiments verify the ability of this invention to stably obtain LLZO solid electrolytes with high ionic conductivity.

[0028] This invention breaks with traditional approaches, employing fused zirconium oxide (ZrO2 content ≥ 98 wt%, containing certain amounts of impurities such as Al2O3, Fe2O3, SiO2, and TiO2) as the zirconium source. It fully utilizes the natural impurity elements as functional dopant sources for Al, Fe, Ti, and Si, balancing cost control and structural optimization, significantly reducing the cost of the zirconium source and dopants. To precisely control the doping ratio of the final material, the inventors analyzed the impurity content in the fused zirconium oxide and added exogenous high-purity dopants such as Al2O3, Fe2O3, SiO2, and TiO2 to achieve controllable total dopant content. Based on this, a process route of ball milling–mineralization–secondary ball milling–isostatic pressing–high-temperature sintering is adopted to effectively promote the formation and densification of cubic LLZO, ensuring that the material maintains structural stability while achieving excellent ionic conductivity.

[0029] This invention focuses on two core objectives: reducing material costs and optimizing structural performance, solving several key technical challenges in the preparation of existing LLZO solid electrolytes. First, by replacing expensive high-purity zirconium oxide with industrial-grade fused zirconium oxide, the raw material cost of the zirconium source is significantly reduced. Second, the invention fully utilizes the natural impurities such as Al, Fe, Ti, and Si in fused zirconium oxide. These impurities, traditionally considered harmful components, are cleverly used as functional dopants. Through formulation design and external compensation, multi-component synergistic doping is achieved, effectively avoiding the large-scale use of high-purity dopants and further reducing overall formulation costs. Furthermore, this invention introduces an integrated mineralization-sintering process, effectively promoting the formation and stabilization of cubic LLZO, avoiding the formation of tetragonal phases, and improving the ionic conductivity of the material. Simultaneously, the optimized ball milling and secondary granulation strategies enhance the reactivity and particle uniformity of the powder, making the material easier to densify during sintering, resulting in a more compact microstructure. This facilitates the formation of continuous and low-resistance lithium-ion migration channels, thereby significantly improving the overall performance of the solid electrolyte.

[0030] Compared with existing technologies, this invention has the following advantages: 1. The metal elements doped in the material are all common and inexpensive oxides, without precious metals such as Ta and Nb, resulting in low overall raw material cost; 2. Natural impurities in fused zirconium oxide are converted into functional dopants, simplifying the formulation system and reducing processing steps; 3. The sintered sample exhibits a dense structure, with SEM images showing uniform grain size and XRD analysis indicating a single cubic garnet-type structure without impurities; 4. The electrical conductivity at room temperature is significantly improved compared to lithium lanthanum zirconium oxide prepared using only fused zirconium oxide, lithium carbonate, and lanthanum oxide; 5. It is suitable for industrialization, with clear cost advantages and structural control capabilities.

[0031] In terms of raw material costs, alumina, silicon dioxide, titanium dioxide, alumina and iron oxide account for a small proportion and their impact on raw material costs can be ignored; the price of each ton of fused zirconium oxide and high-purity zirconium is about RMB35,000 and RMB56,000 respectively. A comparison of the prices of fused zirconium oxide and high-purity zirconium shows that using fused zirconium oxide as the main raw material can significantly reduce raw material costs. Attached Figure Description

[0032] Figure 1 This is a SEM microstructure image of the doped LLZO solid electrolyte material of Embodiment 1 of the present invention;

[0033] Figure 2 This is the XRD pattern of the doped LLZO solid electrolyte material in Embodiment 1 of the present invention. Detailed Implementation

[0034] The fused zirconium oxide used in all the following examples and comparative examples in step (1) is the same, and its chemical composition is: ZrO2 98 wt%, Fe2O3 0.1 wt%, TiO2 0.3 wt%, Al2O3 0.4 wt%, SiO2 1.2 wt%.

[0035] Example 1: In this example, the chemical formula of the doped LLZO solid electrolyte material is Li. 6.70 Al 0.30 La3Zr 1.15 Fe 0.30 Ti 0.39 Si 0.16 O 12 .

[0036] In this embodiment, the preparation method of the doped LLZO solid electrolyte material includes the following steps in sequence:

[0037] (1) Based on the chemical formula Li 6.70 Al 0.30 La3Zr 1.15 Fe 0.30 Ti 0.39 Si 0.16 O 12 The raw materials are prepared in a limited stoichiometric ratio, with lithium carbonate (Li2CO3) as the lithium source, lanthanum oxide (La2O3) as the lanthanum source, fused zirconium oxide as the zirconium source, and dopants including aluminum oxide (Al2O3), iron oxide (Fe2O3), titanium oxide (TiO2), and silicon oxide (SiO2).

[0038] The amounts of lithium carbonate (Li2CO3), lanthanum oxide (La2O3), fused zirconium oxide, doped aluminum oxide (Al2O3), doped iron oxide (Fe2O3), doped titanium oxide (TiO2), and doped silicon oxide (SiO2) are shown in Table 1.

[0039] (2) The lithium carbonate, lanthanum oxide, fused zirconium oxide and dopant prepared in step (1) are added to the ball milling equipment for the first wet ball milling; after the first wet ball milling is completed, the slurry is dried (the slurry is dried at 90°C) to obtain a uniformly mixed powder.

[0040] In step (2), the lithium carbonate, lanthanum oxide, fused zirconium oxide and dopant prepared in step (1) are added to a polypropylene ball milling jar for mixing and ball milling (ball milling is carried out under room temperature and closed conditions); during the ball milling process, zirconium oxide ceramic balls with a diameter of 2 mm and zirconium oxide ceramic balls with a diameter of 5 mm are used together as the ball milling medium, the mass ratio of zirconium oxide ceramic balls with a diameter of 2 mm to that with a diameter of 5 mm is 2:1, the ball-to-material ratio is 10:1, isopropanol is used as the dispersion solvent, and the ball milling time is 12 hours;

[0041] (3) The mixed powder obtained in step (2) is subjected to mineralization treatment to obtain a block;

[0042] In this step (3), the mixed powder obtained in step (2) is placed in an air atmosphere for mineralization treatment. The mineralization treatment uses a magnesium oxide crucible as a reaction vessel. The reaction vessel and the mixed powder inside it are heated from room temperature to 1000℃, the heating rate is controlled at 3℃ / min, and then kept at 1000℃ for 6 hours.

[0043] (4) After cooling the block obtained in step (3), crush it and then perform a second wet ball milling to obtain powder;

[0044] In this step (4), the second wet ball milling uses zirconia balls with a particle size of 0.5 mm as the ball milling medium, the ball-to-material ratio is 15:1, isopropanol is used as the dispersion solvent, and the ball milling time is 6 hours; to obtain ultrafine powder with a D50 particle size of 1 μm (after ball milling, the powder is dried and sieved).

[0045] (5) After the powder obtained in step (4) is mixed evenly with the binder, it is pressed into shape to obtain a blank;

[0046] In this step (5), the amount of adhesive used is 3wt% of the powder; the adhesive is a 4% polyvinyl alcohol aqueous solution by mass percentage.

[0047] The pressing process in step (5) is as follows: First, a molding process is used to apply a pressure of 25MPa to press the mixture of powder and binder into a sheet blank; then the sheet blank is subjected to isostatic pressing (held at 300MPa pressure for 3 minutes) to obtain a blank with a thickness of 1 mm and a diameter of 12 mm.

[0048] (6) Sinter the blank obtained by pressing in step (5) to obtain the desired doped LLZO solid electrolyte material.

[0049] In step (6) above, the blank obtained by pressing in step (5) is placed in a magnesium oxide crucible and sintered in an air atmosphere. The sintering process uses a heating rate of 2℃ / min to heat the magnesium oxide crucible and the blank inside it from room temperature to 1200℃, and then holds it at 1200℃ for 10 hours.

[0050] In step (6) above, in order to prevent the lithium element from volatilizing at high temperature, LLZO powder with the same composition as the blank is covered on the surface of the blank. The LLZO powder can be prepared from LLZO powder with the same formula (e.g., the powder obtained in step (4)).

[0051] The ionic conductivity of the doped LLZO solid electrolyte material in this embodiment is shown in Table 1.

[0052] Example 2: In this example, the chemical formula of the doped LLZO solid electrolyte material is Li. 6.84 Al 0.16 La3Zr 1.61 Fe 0.2 Ti 0.15 Si 0.04 O 12 .

[0053] In this embodiment, the preparation method of the doped LLZO solid electrolyte material includes the following steps in sequence:

[0054] (1) Based on the chemical formula Li 6.84 Al 0.16 La3Zr 1.61 Fe 0.2 Ti 0.15 Si 0.04 O 12 The raw materials are prepared in a limited stoichiometric ratio, with lithium carbonate (Li2CO3) as the lithium source, lanthanum oxide (La2O3) as the lanthanum source, fused zirconium oxide as the zirconium source, and dopants including aluminum oxide (Al2O3), iron oxide (Fe2O3), and titanium oxide (TiO2).

[0055] The amounts of lithium carbonate (Li2CO3), lanthanum oxide (La2O3), fused zirconium oxide, doped aluminum oxide (Al2O3), doped iron oxide (Fe2O3), and doped titanium oxide (TiO2) are shown in Table 1.

[0056] (2) The lithium carbonate, lanthanum oxide, fused zirconium oxide and dopant prepared in step (1) are added to the ball milling equipment for the first wet ball milling; after the first wet ball milling is completed, the slurry is dried to obtain a uniformly mixed powder.

[0057] (3) The mixed powder obtained in step (2) is subjected to mineralization treatment to obtain a block;

[0058] (4) After cooling the block obtained in step (3), crush it and then perform a second wet ball milling to obtain powder;

[0059] (5) After the powder obtained in step (4) is mixed evenly with the binder, it is pressed into shape to obtain a blank;

[0060] (6) Sinter the blank obtained by pressing in step (5) to obtain the desired doped LLZO solid electrolyte material.

[0061] The specific process and process conditions of steps (2)-(6) in this embodiment are the same as those in embodiment 1.

[0062] The ionic conductivity of the doped LLZO solid electrolyte material in this embodiment is shown in Table 1.

[0063] Example 3: In this example, the chemical formula of the doped LLZO solid electrolyte material is Li. 6.71 Al 0.29 La3Zr 1.35 Fe 0.08 Ti 0.21 Si 0.36 O 12 .

[0064] In this embodiment, the preparation method of the doped LLZO solid electrolyte material includes the following steps in sequence:

[0065] (1) Based on the chemical formula Li 6.71 Al 0.29 La3Zr 1.35 Fe 0.08 Ti 0.21 Si 0.36 O 12The raw materials are prepared in a limited stoichiometric ratio, with lithium carbonate (Li2CO3) as the lithium source, lanthanum oxide (La2O3) as the lanthanum source, fused zirconium oxide as the zirconium source, and dopants including aluminum oxide (Al2O3), iron oxide (Fe2O3), titanium oxide (TiO2), and silicon oxide (SiO2).

[0066] The amounts of lithium carbonate (Li2CO3), lanthanum oxide (La2O3), fused zirconium oxide, doped aluminum oxide (Al2O3), doped iron oxide (Fe2O3), doped titanium oxide (TiO2), and doped silicon oxide (SiO2) are shown in Table 1.

[0067] (2) The lithium carbonate, lanthanum oxide, fused zirconium oxide and dopant prepared in step (1) are added to the ball milling equipment for the first wet ball milling; after the first wet ball milling is completed, the slurry is dried to obtain a uniformly mixed powder.

[0068] (3) The mixed powder obtained in step (2) is subjected to mineralization treatment to obtain a block;

[0069] (4) After cooling the block obtained in step (3), crush it and then perform a second wet ball milling to obtain powder;

[0070] (5) After the powder obtained in step (4) is mixed evenly with the binder, it is pressed into shape to obtain a blank;

[0071] (6) Sinter the blank obtained by pressing in step (5) to obtain the desired doped LLZO solid electrolyte material.

[0072] The specific process and process conditions of steps (2)-(6) in this embodiment are the same as those in embodiment 1.

[0073] The ionic conductivity of the doped LLZO solid electrolyte material in this embodiment is shown in Table 1.

[0074] Example 4: In this example, the chemical formula of the doped LLZO solid electrolyte material is Li. 6.85 Al 0.15 La3Zr 1.80 Fe 0.14 Ti 0.01 Si 0.05 O 12 .

[0075] In this embodiment, the preparation method of the doped LLZO solid electrolyte material includes the following steps in sequence:

[0076] (1) Based on the chemical formula Li 6.85 Al 0.15 La3Zr 1.80 Fe0.14 Ti 0.01 Si 0.05 O 12 Each raw material is supplied with a limited stoichiometric ratio, with lithium carbonate (Li2CO3) as the lithium source, lanthanum oxide (La2O3) as the lanthanum source, fused zirconium oxide as the zirconium source, and aluminum oxide (Al2O3) and iron oxide (Fe2O3) as dopants.

[0077] The amounts of lithium carbonate (Li2CO3), lanthanum oxide (La2O3), fused zirconium oxide, dopant aluminum oxide (Al2O3), and dopant iron oxide (Fe2O3) are shown in Table 1.

[0078] (2) The lithium carbonate, lanthanum oxide, fused zirconium oxide and dopant prepared in step (1) are added to the ball milling equipment for the first wet ball milling; after the first wet ball milling is completed, the slurry is dried to obtain a uniformly mixed powder.

[0079] (3) The mixed powder obtained in step (2) is subjected to mineralization treatment to obtain a block;

[0080] (4) After cooling the block obtained in step (3), crush it and then perform a second wet ball milling to obtain powder;

[0081] (5) After the powder obtained in step (4) is mixed evenly with the binder, it is pressed into shape to obtain a blank;

[0082] (6) Sinter the blank obtained by pressing in step (5) to obtain the desired doped LLZO solid electrolyte material.

[0083] The specific process and process conditions of steps (2)-(6) in this embodiment are the same as those in embodiment 1.

[0084] The ionic conductivity of the doped LLZO solid electrolyte material in this embodiment is shown in Table 1.

[0085] Example 5: In this example, the chemical formula of the doped LLZO solid electrolyte material is Li. 6.72 Al 0.28 La3Zr 1.57 Fe 0.2 Ti 0.19 Si 0.04 O 12 .

[0086] In this embodiment, the preparation method of the doped LLZO solid electrolyte material includes the following steps in sequence:

[0087] (1) Based on the chemical formula Li 6.72 Al 0.28 La3Zr 1.57 Fe0.2 Ti 0.19 Si 0.04 O 12 The raw materials are prepared in a limited stoichiometric ratio, with lithium carbonate (Li2CO3) as the lithium source, lanthanum oxide (La2O3) as the lanthanum source, fused zirconium oxide as the zirconium source, and dopants including aluminum oxide (Al2O3), iron oxide (Fe2O3), and titanium oxide (TiO2).

[0088] The amounts of lithium carbonate (Li2CO3), lanthanum oxide (La2O3), fused zirconium oxide, doped aluminum oxide (Al2O3), doped iron oxide (Fe2O3), and doped titanium oxide (TiO2) are shown in Table 1.

[0089] (2) The lithium carbonate, lanthanum oxide, fused zirconium oxide and dopant prepared in step (1) are added to the ball milling equipment for the first wet ball milling; after the first wet ball milling is completed, the slurry is dried to obtain a uniformly mixed powder.

[0090] (3) The mixed powder obtained in step (2) is subjected to mineralization treatment to obtain a block;

[0091] (4) After cooling the block obtained in step (3), crush it and then perform a second wet ball milling to obtain powder;

[0092] (5) After the powder obtained in step (4) is mixed evenly with the binder, it is pressed into shape to obtain a blank;

[0093] (6) Sinter the blank obtained by pressing in step (5) to obtain the desired doped LLZO solid electrolyte material.

[0094] The specific process and process conditions of steps (2)-(6) in this embodiment are the same as those in embodiment 1.

[0095] The ionic conductivity of the doped LLZO solid electrolyte material in this embodiment is shown in Table 1.

[0096] Example 6: In this example, the chemical formula of the doped LLZO solid electrolyte material is Li. 6.85 Al 0.15 La3Zr 1.73 Fe 0.01 Ti 0.15 Si 0.11 O 12 .

[0097] In this embodiment, the preparation method of the doped LLZO solid electrolyte material includes the following steps in sequence:

[0098] (1) Based on the chemical formula Li 6.85 Al0.15 La3Zr 1.73 Fe 0.01 Ti 0.15 Si 0.11 O 12 The raw materials are prepared in a limited stoichiometric ratio, with lithium carbonate (Li2CO3) as the lithium source, lanthanum oxide (La2O3) as the lanthanum source, fused zirconium oxide as the zirconium source, and dopants including aluminum oxide (Al2O3), iron oxide (Fe2O3), titanium oxide (TiO2), and silicon oxide (SiO2).

[0099] The amounts of lithium carbonate (Li2CO3), lanthanum oxide (La2O3), fused zirconium oxide, doped aluminum oxide (Al2O3), doped iron oxide (Fe2O3), doped titanium oxide (TiO2), and doped silicon oxide (SiO2) are shown in Table 1.

[0100] (2) The lithium carbonate, lanthanum oxide, fused zirconium oxide and dopant prepared in step (1) are added to the ball milling equipment for the first wet ball milling; after the first wet ball milling is completed, the slurry is dried to obtain a uniformly mixed powder.

[0101] (3) The mixed powder obtained in step (2) is subjected to mineralization treatment to obtain a block;

[0102] (4) After cooling the block obtained in step (3), crush it and then perform a second wet ball milling to obtain powder;

[0103] (5) After the powder obtained in step (4) is mixed evenly with the binder, it is pressed into shape to obtain a blank;

[0104] (6) Sinter the blank obtained by pressing in step (5) to obtain the desired doped LLZO solid electrolyte material.

[0105] The specific process and process conditions of steps (2)-(6) in this embodiment are the same as those in embodiment 1.

[0106] The ionic conductivity of the doped LLZO solid electrolyte material in this embodiment is shown in Table 1.

[0107] Example 7: In this example, the chemical formula of the doped LLZO solid electrolyte material is Li. 6.84 Al 0.16 La3Zr 1.72 Fe 0.08 Ti 0.09 Si 0.11 O 12 .

[0108] In this embodiment, the preparation method of the doped LLZO solid electrolyte material includes the following steps in sequence:

[0109] (1) Based on the chemical formula Li 6.84 Al 0.16 La3Zr 1.72 Fe 0.08 Ti 0.09 Si 0.11 O 12 The raw materials are prepared in a limited stoichiometric ratio, with lithium carbonate (Li2CO3) as the lithium source, lanthanum oxide (La2O3) as the lanthanum source, fused zirconium oxide as the zirconium source, and dopants including aluminum oxide (Al2O3), iron oxide (Fe2O3), titanium oxide (TiO2), and silicon oxide (SiO2).

[0110] The amounts of lithium carbonate (Li2CO3), lanthanum oxide (La2O3), fused zirconium oxide, doped aluminum oxide (Al2O3), doped iron oxide (Fe2O3), doped titanium oxide (TiO2), and doped silicon oxide (SiO2) are shown in Table 1.

[0111] (2) The lithium carbonate, lanthanum oxide, fused zirconium oxide and dopant prepared in step (1) are added to the ball milling equipment for the first wet ball milling; after the first wet ball milling is completed, the slurry is dried to obtain a uniformly mixed powder.

[0112] (3) The mixed powder obtained in step (2) is subjected to mineralization treatment to obtain a block;

[0113] (4) After cooling the block obtained in step (3), crush it and then perform a second wet ball milling to obtain powder;

[0114] (5) After the powder obtained in step (4) is mixed evenly with the binder, it is pressed into shape to obtain a blank;

[0115] (6) Sinter the blank obtained by pressing in step (5) to obtain the desired doped LLZO solid electrolyte material.

[0116] The specific process and process conditions of steps (2)-(6) in this embodiment are the same as those in embodiment 1.

[0117] The ionic conductivity of the doped LLZO solid electrolyte material in this embodiment is shown in Table 1.

[0118] Example 8: In this example, the chemical formula of the doped LLZO solid electrolyte material is Li. 6.96 Al 0.04 La3Zr 1.84 Fe 0.01 Ti 0.11 Si 0.04 O 12 .

[0119] In this embodiment, the preparation method of the doped LLZO solid electrolyte material includes the following steps in sequence:

[0120] (1) Based on the chemical formula Li 6.96 Al 0.04 La3Zr 1.84 Fe 0.01 Ti 0.11 Si 0.04 O 12 Each raw material is supplied with a limited stoichiometric ratio, with lithium carbonate (Li2CO3) as the lithium source, lanthanum oxide (La2O3) as the lanthanum source, fused zirconium oxide as the zirconium source, and aluminum oxide (Al2O3) and titanium oxide (TiO2) as dopants.

[0121] The amounts of lithium carbonate (Li2CO3), lanthanum oxide (La2O3), fused zirconium oxide, doped aluminum oxide (Al2O3), and doped titanium oxide (TiO2) are shown in Table 1.

[0122] (2) The lithium carbonate, lanthanum oxide, fused zirconium oxide and dopant prepared in step (1) are added to the ball milling equipment for the first wet ball milling; after the first wet ball milling is completed, the slurry is dried to obtain a uniformly mixed powder.

[0123] (3) The mixed powder obtained in step (2) is subjected to mineralization treatment to obtain a block;

[0124] (4) After cooling the block obtained in step (3), crush it and then perform a second wet ball milling to obtain powder;

[0125] (5) After the powder obtained in step (4) is mixed evenly with the binder, it is pressed into shape to obtain a blank;

[0126] (6) Sinter the blank obtained by pressing in step (5) to obtain the desired doped LLZO solid electrolyte material.

[0127] The specific process and process conditions of steps (2)-(6) in this embodiment are the same as those in embodiment 1.

[0128] The ionic conductivity of the doped LLZO solid electrolyte material in this embodiment is shown in Table 1.

[0129] Example 9: In this example, the chemical formula of the doped LLZO solid electrolyte material is Li. 6.71 Al 0.29 La3Zr 1.93 Fe 0.01 Ti 0.01 Si 0.05 O 12 .

[0130] In this embodiment, the preparation method of the doped LLZO solid electrolyte material includes the following steps in sequence:

[0131] (1) Based on the chemical formula Li 6.71 Al 0.29 La3Zr 1.94 Fe 0.01 Ti 0.01 Si 0.05 O 12 Each raw material is supplied in a limited stoichiometric ratio, with lithium carbonate (Li2CO3) as the lithium source, lanthanum oxide (La2O3) as the lanthanum source, fused zirconium oxide as the zirconium source, and aluminum oxide (Al2O3) as the dopant.

[0132] The amounts of lithium carbonate (Li2CO3), lanthanum oxide (La2O3), fused zirconium oxide, and dopant aluminum oxide (Al2O3) are shown in Table 1.

[0133] (2) The lithium carbonate, lanthanum oxide, fused zirconium oxide and dopant prepared in step (1) are added to the ball milling equipment for the first wet ball milling; after the first wet ball milling is completed, the slurry is dried to obtain a uniformly mixed powder.

[0134] (3) The mixed powder obtained in step (2) is subjected to mineralization treatment to obtain a block;

[0135] (4) After cooling the block obtained in step (3), crush it and then perform a second wet ball milling to obtain powder;

[0136] (5) After the powder obtained in step (4) is mixed evenly with the binder, it is pressed into shape to obtain a blank;

[0137] (6) Sinter the blank obtained by pressing in step (5) to obtain the desired doped LLZO solid electrolyte material.

[0138] The specific process and process conditions of steps (2)-(6) in this embodiment are the same as those in embodiment 1.

[0139] The ionic conductivity of the doped LLZO solid electrolyte material in this embodiment is shown in Table 1.

[0140] Comparative Example 1: In this comparative example, the chemical formula of the doped LLZO solid electrolyte material is Li. 6.98 Al 0.02 La3Zr 1.93 Fe 0.01 Ti 0.01 Si 0.05 O 12 .

[0141] In this comparative example, the preparation method of the doped LLZO solid electrolyte material includes the following steps:

[0142] (1) Based on the chemical formula Li 6.98 Al 0.02 La3Zr 1.93 Fe 0.01 Ti 0.01 Si 0.05 O 12 Each raw material is supplied with a limited stoichiometric ratio, with lithium carbonate (Li2CO3) as the lithium source, lanthanum oxide (La2O3) as the lanthanum source, and fused zirconium oxide as the zirconium source, without any other substances being added;

[0143] The amounts of lithium carbonate (Li2CO3), lanthanum oxide (La2O3), and fused zirconium oxide are shown in Table 1.

[0144] (2) The lithium carbonate, lanthanum oxide and fused zirconium oxide prepared in step (1) are added to the ball mill for the first wet ball milling; after the first wet ball milling is completed, the slurry is dried to obtain a uniformly mixed powder.

[0145] (3) The mixed powder obtained in step (2) is subjected to mineralization treatment to obtain a block;

[0146] (4) After cooling the block obtained in step (3), crush it and then perform a second wet ball milling to obtain powder;

[0147] (5) After the powder obtained in step (4) is mixed evenly with the binder, it is pressed into shape to obtain a blank;

[0148] (6) Sinter the blank obtained by pressing in step (5) to obtain the desired doped LLZO solid electrolyte material.

[0149] The specific process and process conditions of steps (2)-(6) in this comparative example are the same as those in Example 1.

[0150] The ionic conductivity of the doped LLZO solid electrolyte material in this comparative example is shown in Table 1.

[0151] The method for testing the ionic conductivity of the doped LLZO solid electrolyte material in Examples 1-9 and Comparative Example 1 is as follows: The surface of the LLZO solid electrolyte wafer is polished to obtain a smooth test interface; silver paste is evenly brushed onto both sides of the wafer and dried at 100°C for 30 minutes to form a good contact electrode; then, the total ionic conductivity of the LLZO solid electrolyte is tested using an AC impedance spectrometer at a frequency range of 1 MHz to 1 Hz and an amplitude of 10 mV at room temperature.

[0152] Table 1. Amount and ionic conductivity of each raw material in Examples 1-9

[0153] Lithium carbonate mass (grams) Mass of lanthanum oxide (g) Mass of fused zirconia (g) Mass of alumina (grams) Mass of iron oxide (grams) Mass of silicon dioxide (grams) Mass of titanium dioxide (g) Ionic conductivity (10⁻⁴ S / cm) Example 1 247.53 488.73 141.70 14.84 23.84 3.85 15.34 3.2 Example 2 252.63 488.73 198.38 7.65 15.89 0 5.59 7.51 Example 3 247.90 488.73 166.35 14.27 6.31 9.61 8.07 5.38 Example 4 253.00 488.73 221.80 7.09 11.10 0 0 1.21 Example 5 248.27 488.73 193.46 13.66 15.89 0 7.19 1.06 Example 6 252.93 488.73 213.17 7.09 0.24 2.04 5.59 1.64 Example 7 252.56 488.73 211.94 7.60 6.31 2.04 3.15 2.23 Example 8 257.14 488.73 226.72 1.26 0 0 4.03 1.27 Example 9 247.90 488.73 239.05 14.03 0 0 0 1.13 Comparative Example 1 258.02 488.73 239.05 0 0 0 0 0.57

[0154] Comparison of experimental test results and effects:

[0155] 1. SEM microstructure (the test subject was the doped LLZO solid electrolyte material of Example 1)

[0156] from Figure 1 As can be seen, the LLZO ceramic sintered body exhibits a dense structure with uniform and fully developed grains, without any obviously oversized grains. The grain size is approximately 20–30 μm, and the grain boundaries are clear.

[0157] 2. XRD phase analysis (the test object was the doped LLZO solid electrolyte material of Example 1)

[0158] from Figure 2 The XRD pattern shows peaks at 2θ of 17.1°, 24.6°, 28.2°, 30.5°, 33.3°, 37.9°, 40.6°, and 47.1°, corresponding to the cubic phase LLZO (PDF#45-0109) peaks (211), (231), (400), (420), (422), (521), (611), (640), and (642), respectively. No other impurity peaks were observed in the XRD pattern, and no tetragonal splitting peaks were found near 35.5°. This indicates that high-purity cubic phase LLZO can be prepared by adding high-purity dopants using fused zirconia as the zirconium source.

[0159] 3. Summary

[0160] This invention successfully prepared a high-performance cubic phase LLZO solid electrolyte by replacing high-purity zirconium oxide with fused zirconium oxide and combining it with a quaternary doping strategy of Al, Fe, Ti, and Si. It has the advantages of controllable process, low cost, and excellent performance, and is suitable for the needs of solid-state battery industrialization.

Claims

1. A doped LLZO solid electrolyte material, characterized in that... The chemical formula of the doped LLZO solid electrolyte material is Li 7-x Al x La3Zr 2-a-b-c Fe a Ti b Si c O 12 Where 0.04≤x≤0.30, 0.01≤a≤0.30, 0.01≤b≤0.39, 0.04≤c≤0.35, and 0.06≤a+b+c≤0.85; The doped LLZO solid electrolyte material has a cubic phase structure; The Zr contained in the doped LLZO solid electrolyte material comes from fused zirconium oxide; The preparation method of the doped LLZO solid electrolyte material includes the following steps in sequence: (1) Based on the general chemical formula Li 7-x Al x La3Zr 2-a-b-c Fe a Ti b Si c O 12 Where 0.04≤x≤0.30, 0.01≤a≤0.30, 0.01≤b≤0.39, 0.04≤c≤0.35, and 0.06≤a+b+c≤0.85; The raw materials are prepared according to the stoichiometric ratio specified in the general chemical formula: lithium carbonate is used as the lithium source; lanthanum oxide is used as the lanthanum source; fused zirconium oxide is used as the zirconium source, with a ZrO2 content of not less than 98 wt% and containing one or more of the impurities Al2O3, Fe2O3, TiO2 and SiO2; and the difference is calculated based on the existing Al2O3, Fe2O3, TiO2 and SiO2 content in the fused zirconium oxide, and one or more of the dopants Al2O3, Fe2O3, TiO2 and SiO2 are added. (2) The lithium carbonate, lanthanum oxide, fused zirconium oxide and dopant prepared in step (1) are added to the ball milling equipment for the first wet ball milling; after the first wet ball milling is completed, the slurry is dried to obtain a uniformly mixed powder. (3) The mixed powder obtained in step (2) is subjected to mineralization treatment to obtain a block; In this step (3), the mixed powder obtained in step (2) is placed in an air atmosphere for mineralization treatment. The mineralization treatment uses a magnesium oxide crucible as a reaction vessel. The reaction vessel and the mixed powder inside it are heated from room temperature to 950–1050℃, and the heating rate is controlled at 2.5–3.5℃ / min. Then, it is kept at 950–1050℃ for 6–9 hours. (4) After cooling the block obtained in step (3), crush it and then perform a second wet ball milling to obtain powder; (5) After the powder obtained in step (4) is mixed evenly with the binder, it is pressed into shape to obtain a blank; (6) Sinter the blank obtained by pressing in step (5) to obtain the desired doped LLZO solid electrolyte material; In step (6), the blank obtained by pressing in step (5) is placed in a magnesium oxide crucible and sintered in an air atmosphere. The sintering process uses a heating rate of 1-5℃ / min to heat the magnesium oxide crucible and the blank inside it from room temperature to 1150-1230℃, and then holds it at 1150-1230℃ for 8-12 hours.

2. The preparation method of the doped LLZO solid electrolyte material according to claim 1, characterized in that... The steps are as follows: (1) Based on the general chemical formula Li 7-x Al x La3Zr 2-a-b-c Fe a Ti b Si c O 12 Where 0.04≤x≤0.30, 0.01≤a≤0.30, 0.01≤b≤0.39, 0.04≤c≤0.35, and 0.06≤a+b+c≤0.85; The raw materials are prepared according to the stoichiometric ratio specified in the general chemical formula: lithium carbonate is used as the lithium source; lanthanum oxide is used as the lanthanum source; fused zirconium oxide is used as the zirconium source, with a ZrO2 content of not less than 98 wt% and containing one or more of the impurities Al2O3, Fe2O3, TiO2 and SiO2; and the difference is calculated based on the existing Al2O3, Fe2O3, TiO2 and SiO2 content in the fused zirconium oxide, and one or more of the dopants Al2O3, Fe2O3, TiO2 and SiO2 are added. (2) The lithium carbonate, lanthanum oxide, fused zirconium oxide and dopant prepared in step (1) are added to the ball milling equipment for the first wet ball milling; after the first wet ball milling is completed, the slurry is dried to obtain a uniformly mixed powder. (3) The mixed powder obtained in step (2) is subjected to mineralization treatment to obtain a block; In this step (3), the mixed powder obtained in step (2) is placed in an air atmosphere for mineralization treatment. The mineralization treatment uses a magnesium oxide crucible as a reaction vessel. The reaction vessel and the mixed powder inside it are heated from room temperature to 950–1050℃, and the heating rate is controlled at 2.5–3.5℃ / min. Then, it is kept at 950–1050℃ for 6–9 hours. (4) After cooling the block obtained in step (3), crush it and then perform a second wet ball milling to obtain powder; (5) After the powder obtained in step (4) is mixed evenly with the binder, it is pressed into shape to obtain a blank; (6) Sinter the blank obtained by pressing in step (5) to obtain the desired doped LLZO solid electrolyte material; In step (6), the blank obtained by pressing in step (5) is placed in a magnesium oxide crucible and sintered in an air atmosphere. The sintering process uses a heating rate of 1-5℃ / min to heat the magnesium oxide crucible and the blank inside it from room temperature to 1150-1230℃, and then holds it at 1150-1230℃ for 8-12 hours.

3. The method for preparing the doped LLZO solid electrolyte material according to claim 2, characterized in that: The chemical composition of the fused zirconium oxide used in step (1) is: ZrO2≥98 wt%, Fe2O3≤0.1 wt%, TiO2≤0.3 wt%, Al2O3≤0.4 wt%, SiO2≤1.2wt%.

4. The method for preparing the doped LLZO solid electrolyte material according to claim 2, characterized in that: In step (2), the lithium carbonate, lanthanum oxide, fused zirconium oxide and dopant prepared in step (1) are added to the ball milling equipment for mixing and ball milling. During the ball milling process, zirconium oxide ceramic balls with a diameter of 2 mm and zirconium oxide ceramic balls with a diameter of 5 mm are used as the ball milling media. The mass ratio of zirconium oxide ceramic balls with a diameter of 2 mm to zirconium oxide ceramic balls with a diameter of 5 mm is 4:1-2:1, the ball-to-material ratio is 8:1-15:1, isopropanol is used as the dispersion solvent, and the ball milling time is 3-12 hours. In step (2), the slurry is dried at 80–100°C.

5. The method for preparing the doped LLZO solid electrolyte material according to claim 2, characterized in that: In step (4), the second wet ball milling uses zirconia balls with a particle size of 0.5 mm as the ball milling medium, the ball-to-material ratio is 8:1-15:1, isopropanol is used as the dispersion solvent, and the ball milling time is 3-12 hours.

6. The method for preparing the doped LLZO solid electrolyte material according to claim 2, characterized in that: In step (5), the amount of binder used is 2-5 wt% of the powder, and the binder is a polyvinyl alcohol aqueous solution or an acrylic emulsion.

7. The method for preparing the doped LLZO solid electrolyte material according to claim 2, characterized in that: The pressing process in step (5) is as follows: First, a molding process is used to apply a pressure of 20–30 MPa to press the mixture of powder and binder into a sheet blank; then the sheet blank is subjected to isostatic pressing.

8. The method for preparing the doped LLZO solid electrolyte material according to claim 2, characterized in that: In step (6), LLZO powder with the same composition as the green body is applied to the surface of the green body.

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