A / B / O three-position composite doped LLTO solid electrolyte ceramic material and preparation method thereof

Abstract

The invention discloses an A / B / O three-position composite doped LLTO solid electrolyte ceramic material and a preparation method thereof, aiming at A-position Li < + > ions of a Li < 0.33 > La < 0.56 > TiO < 3 > ceramic material, high-valence ions M with high electronegativity are adopted to carry out A-position partial substitution, aiming at B-position Ti < 4 + > ions, low-valence ions Sb < 3 + > with high electronegativity are adopted to carry out B-position partial substitution, aiming at O-position O < 2-> ions, o-site partial substitution is performed by adopting high-electronegativity low-valence ions F <->, so that a stable and high-conductivity cubic phase crystal form of a high-electronegativity element is introduced, a lithium ion channel is widened, the electronic insulation performance of the material is improved, an electricity price compensation mechanism is triggered by utilizing non-equivalent substitution, more cation vacancy defects are generated in unit cells, and the performance of the material is improved. The oxygen vacancy concentration at the grain boundary is reduced by utilizing a lattice oxygen transition mechanism, and positive charge enrichment at the grain boundary is inhibited; and by utilizing the electricity price difference between O < 2-> and F <->, cation vacancies with certain concentration are ensured to exist in unit cells, certain cation vacancies are formed at the grain boundary, and the grain boundary conductivity of the material is improved, so that a novel environment-friendly solid electrolyte material with excellent comprehensive performance is formed. The preparation method is low in sintering temperature, low in preparation cost, simple in process and easy to operate, influence factors are easy to control, and the preparation method is suitable for large-scale industrial production and beneficial to popularization and application.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte ceramic materials technology, and in particular to a composite-doped LLTO solid electrolyte ceramic material and its preparation method. Background Technology

[0002] Currently, solid-state lithium-ion battery technology is a key technology being researched and developed in the new energy industry, and solid-state electrolytes are the core materials for solid-state batteries. Among them, perovskite (Li-ion) electrolytes are... 0.33 La 0.56 TiO3, LLTO) solid electrolytes have high grain conductivity (1 mS·cm) -1 Due to its strong mechanical properties and air stability, LLTO has become one of the most promising solid electrolytes. However, the grain boundary conductivity of current LLTO solid electrolytes is relatively low, typically only 1×10⁻⁶. -2 mS·cm -1 The order of magnitude or even lower, and the difficulty in preparing high-conductivity cubic phase structures using solid-state reaction methods, greatly limit the application of LLTO solid electrolytes.

[0003] Currently, researchers have not reached a consensus on the causes of high grain boundary impedance in LLTO solid-state electrolytes. The three main viewpoints are: first, a second phase with extremely low ionic conductivity forms at the grain boundaries; second, the grain boundaries are transitional structures, and energy gradients lead to partial lattice rearrangement, reducing carrier concentration at the grain boundaries; and third, ion transport is blocked by structural distortion at the grain boundary core, and carriers are depleted near the grain boundaries due to space charge. However, due to the difficulty in characterizing LLTO solid-state electrolyte grain boundaries and the complexity of factors affecting grain boundary conductivity, research on grain boundary optimization in LLTO solid-state electrolytes is currently limited, and the grain boundary modification mechanism of perovskite solid-state electrolytes remains unclear. Therefore, improving the cubic phase content and grain boundary conductivity while ensuring the electronic insulation performance of the material to obtain perovskite solid-state electrolyte materials with excellent overall performance is an important research topic in the field of solid-state lithium-ion batteries. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material, specifically targeting Li 0.33 La 0.56 TiO3 ceramic material A-site Li + The ion, a high-valence ion M with high electronegativity, is used for partial substitution at the A-site, targeting the Ti at the B-site. 4+ The ion used is the highly electronegative, low-valence ion Sb. 3+ Perform partial substitution at position B, targeting position O. 2- Ions, using highly electronegative, low-valence ions F -O-site partial substitution is performed. Through the aforementioned composite doping modification, highly electronegative elements are introduced to stabilize the cubic phase crystal structure with high conductivity, broaden the lithium-ion channels, and improve the electronic insulation performance of the material. Then, an inequivalent substitution mechanism is used to trigger a valence compensation mechanism, generating more cation vacancy defects within the unit cell. The lattice oxygen transition mechanism is used to reduce the oxygen vacancy concentration at grain boundaries, suppressing the enrichment of positive charges at grain boundaries. However, lattice oxygen transitions inevitably inhibit the generation of cation vacancies in the unit cell; therefore, O-site partial substitution is then used... 2- and F - The difference in cation valence ensures a certain concentration of cation vacancies within the unit cell, while simultaneously forming cation vacancies at grain boundaries, thereby improving the grain boundary conductivity of the material and resulting in a novel, high-performance, and environmentally friendly solid electrolyte material. Another objective of this invention is to provide a method for preparing the aforementioned A / B / O three-position composite doped LLTO solid electrolyte ceramic material and its product.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] This invention provides an A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material, whose general chemical formula I is Li. (0.33-x) La 0.56 (M) x Ti (1-y) Sb y O (3-z) F z Where 0.01≤x≤0.05, 0.02≤y≤0.08, 0.04≤z≤0.2; M is a highly electronegative ion with a valence higher than Li. + Li doping into the ceramic cell partially replaces the A-site. + Ions; Sb 3 + Ion doping enters the ceramic cell and partially replaces the Ti at the B site. 4+ Ions; F - Ion doping enters the ceramic cell and grain boundaries, partially replacing the O sites. 2- ion.

[0007] Furthermore, in this invention, M is Fe. 3+ Cu 2+ Zn 2+ , or Cr 2+ ion.

[0008] In the above scheme, the total conductivity (σ) of the solid electrolyte ceramic material of the present invention at 20-30℃ is... tot ≥0.05mS·cm -1 Grain boundary conductivity (σ) gb ≥0.065mS·cm -1Total conductivity activation energy (Ea) total The steady-state current (I) under the polarization voltage condition of ≤0.5eV and 100mV is ≤5nA.

[0009] Another objective of this invention is achieved through the following technical solution:

[0010] The preparation method of the above-mentioned A / B / O three-position composite doped LLTO solid electrolyte ceramic material of the present invention includes the following steps:

[0011] (1) Preparation of pre-synthesized precursor powder

[0012] Using Li₂CO₃, La₂O₃, and TiO₂ as matrix raw materials, oxides of element M are used as A-site doping materials, Sb₂O₃ as B-site doping materials, and LiF as O-site doping materials; according to the stoichiometric ratio in the general chemical formula I, the amount of raw material Li₂CO₃ is 105-125 wt%, and the amounts of the remaining raw materials are prepared according to their corresponding stoichiometric ratios; then, anhydrous ethanol is used as the ball milling medium for a single ball milling process. After drying, sieving, and pressing, the ball milled slurry is then milled at 3-6℃·min⁻¹. -1 The pre-calcination process is carried out at 700-900℃ for 300-400 minutes. After natural cooling, the pre-synthesized precursor powder is obtained by grinding and sieving.

[0013] (2) Preparation of calcined powder

[0014] Using Li₂CO₃, La₂O₃, and TiO₂ as raw materials, according to general chemical formula II, i.e., Li 0.33 La 0.56 The stoichiometric ratio of TiO3 is as follows: the amount of raw material Li2CO3 is 105–125 wt% of its stoichiometric ratio, and the amounts of the remaining raw materials are prepared according to their corresponding stoichiometric ratios. Then, anhydrous ethanol is used as the ball milling medium for ball milling. The ball milled slurry is dried, sieved, and then milled in air at 3–6 °C / min. -1 The calcined material is heated to 700-900℃ and held for 400-500 minutes. After natural cooling, the calcined material is ground and sieved. The calcined material is then mixed with alumina powder in a granulator at a mass ratio of calcined material to alumina powder of 1:0.8-1.2 to obtain the calcined powder.

[0015] (3) Preparation of LLTO solid electrolyte materials

[0016] (3-1) The pre-synthesized precursor powder is subjected to secondary ball milling with anhydrous ethanol as the ball milling medium. The ball milling slurry is dried and sieved. The resulting material is then granulated, aged, dried and pressed into a green body.

[0017] (3-2) The green body is covered with sintered powder and fired in air at 3-6°C / min. -1 The product is calcined at 1130–1300℃ for 300–400 minutes and then naturally cooled to obtain the calcined product.

[0018] (3-3) The calcined product is then surface modified to obtain an A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material.

[0019] Furthermore, in step (1) of the preparation method of the present invention, the material is ball-milled once at a mass ratio of material:ball:anhydrous ethanol = 1:3.5 to 4.5:3 for a ball-milling time of 20 to 24 hours; the pressing pressure is 2 to 5 MPa.

[0020] Furthermore, in step (2) of the preparation method of the present invention, ball milling is performed at a mass ratio of material:ball:anhydrous ethanol = 1:1.2 to 1.8:2, and the ball milling time is 5 to 15 minutes.

[0021] Further, in step (3-1) of the preparation method of the present invention, a secondary ball milling process is performed at a mass ratio of material:ball:anhydrous ethanol = 1:3.5 to 4.5:3, and the ball milling time is 18 to 22 hours; granulation is performed using a 5 wt% PVA aqueous solution as a binder, and the amount of binder is 25 to 45 wt% of the material; after granulation, the material is sieved to obtain powder with a particle size of 60 mesh above 80 mesh, and the aging time of the powder is 20 to 24 hours; the pressing pressure is 6 to 10 MPa.

[0022] Furthermore, the surface modification treatment in step (3-3) of the preparation method of the present invention is as follows: First, wet polishing treatment, that is, firstly, the surface of the calcined product is coarsely polished with 400-600 grit sandpaper, and then finely polished with 1500-2500 grit sandpaper until the surface of the calcined product has a mirror effect; Second, coating blocking electrodes, that is, sputtering silver / gold electrodes on the upper and lower surfaces of the polished calcined product for a sputtering time of 60-100s.

[0023] The product was prepared using the above-mentioned method for preparing A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material.

[0024] The present invention has the following beneficial effects:

[0025] (1) During the preparation of perovskite-type solid electrolyte materials, lithium volatilizes and is lost during high-temperature sintering. A small amount of lithium volatilization forms cation vacancy carriers in the material, which is beneficial to lithium-ion conduction; however, high-temperature sintered ceramic products inevitably suffer from a significant amount of lithium volatilization loss. To address this phenomenon, this invention employs two methods to improve the situation: first, by adding 5–25 wt% lithium carbonate to compensate for lithium volatilization during sintering; second, by introducing highly electronegative high-valence ions (M ions, Fe2+, Fe3+) into the system. 3+ Cu 2+ Zn 2+ , or Cr 2+ As a flux, it lowers the firing temperature range of the material. Simultaneously, the introduction of M ions partially replaces Li at the A-site in the system. + Its high electronegativity will inevitably attract the outer electron cloud of the surrounding bridging oxygen, thereby stabilizing the high-temperature cubic phase structure and increasing the cubic phase content of the material.

[0026] (2) During the preparation of perovskite-type solid electrolyte materials, a large number of oxygen vacancy structures exist at the grain boundaries, resulting in a large accumulation of positive charges at the grain boundaries, which are identical to the charge of lithium ions. Therefore, the conduction of lithium ions to the grain boundaries is greatly suppressed. To address this phenomenon, this invention employs a valence ratio B-site Ti... 4+ Low Sb 3+ By partially replacing the oxygen atoms, a charge compensation mechanism is triggered, causing lattice oxygen in the unit cell to jump to the crystal interface. This weakens the accumulation of positive charge at the grain boundary, and the oxygen atoms that jump to the surface can participate in high-temperature physicochemical reactions on the surface, increasing the effective contact area between grains, suppressing structural distortion and atomic rearrangement at the grain boundary, and maintaining a stable phase structure. This improves the grain boundary conductivity of the material, ultimately resulting in a perovskite-type solid electrolyte material with excellent performance.

[0027] (3) Based on the ionic radius rule and according to the valence balance mechanism, the transition of lattice oxygen will inevitably reduce the cation vacancy concentration in the unit cell. To address this phenomenon, this invention selects F with a negative valence of -1. - F ions partially replace O in the crystal lattice, thereby increasing the cation vacancy concentration in the unit cell; simultaneously, some O in the grain boundaries is also replaced by F, thus forming a certain concentration of cation vacancies at the grain boundaries of the material, thereby increasing the Li... + By improving transport efficiency at grain boundaries, high-performance perovskite-type solid electrolyte materials can be obtained.

[0028] (4) This invention modifies the grain boundaries of perovskite-type solid electrolytes by introducing highly electronegative elements, thereby increasing the chemical bond strength at the unit cell and grain boundaries. Furthermore, by controlling the bond length and bond angle through electronegativity, lattice distortion is induced, thus widening the lithium-ion transport channels within the unit cell and achieving the goal of improving the cell and grain boundary conductivity of the material. Simultaneously, the introduction of highly electronegative elements at the A / B sites weakens the O-ion transport process. 2- For Li + The binding effect is beneficial to Li + migrate.

[0029] (5) The introduction of halogen elements will inevitably increase the electronic conductivity of the material. Based on the electronegativity law of materials, this invention greatly improves the ionic conductivity of the material grains while effectively suppressing the increase in electronic conductivity caused by the introduction of halogen elements. The electronic conductivity of the material is controlled below 5nA, and it still shows relatively excellent electronic insulation performance.

[0030] (6) This invention employs advanced aberration-corrected transmission electron microscopy (TEM) technology to characterize the grain boundary structure of perovskite solid electrolyte materials. This reveals another reason for the low grain boundary conductivity of perovskite solid electrolytes: the atomic arrangement at the grain boundaries is highly regular, demonstrating extremely low vacancy carrier concentration at the grain boundaries. This discovery serves as direct evidence for refining the theory of grain boundary conductivity in perovskite solid electrolytes.

[0031] (7) The preparation method of the present invention adopts advanced ceramic preparation technology, with low firing temperature, low preparation cost, simple and easy operation, and easy control of influencing factors. It is suitable for large-scale industrial production and is conducive to promotion and application. Attached Figure Description

[0032] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings:

[0033] Figure 1 These are the XRD phase diagrams of the perovskite-type solid electrolyte ceramic materials prepared in the embodiments and comparative examples of this invention;

[0034] Figure 2 These are scanning electron microscope images of the perovskite-type solid electrolyte ceramic materials prepared in the embodiments and comparative examples of this invention;

[0035] Figure 3 These are EIS images of the surface of the perovskite-type solid electrolyte ceramic materials prepared in the embodiments and comparative examples of the present invention. Detailed Implementation

[0036] Example 1:

[0037] 1. This embodiment describes an A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material, whose general chemical formula I is Li.0.32 La 0.56 Fe 0.01 Ti 0.94 Sb 0.06 O 2.92 F 0.08 Fe 3+ Ion doping partially replaces Li at the A-site in the ceramic cell. + Sb ions 3+ Ion doping enters the ceramic cell and partially replaces the Ti at the B site. 4+ Ions, F - Ion doping into ceramic unit cells and grain boundaries partially replaces O at O ​​sites. 2- ion

[0038] 2. The preparation method of the above-mentioned A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material comprises the following steps:

[0039] (1) Preparation of pre-synthesized precursor powder

[0040] Using analytical grade Li₂CO₃, La₂O₃, TiO₂, Fe₂O₃, Sb₂O₃, and LiF as raw materials, the raw materials were prepared according to the stoichiometric ratios in the aforementioned general chemical formula I, with the amount of Li₂CO₃ being 120 wt% of its stoichiometric value and the remaining raw materials being prepared according to their corresponding stoichiometric values. Then, anhydrous ethanol was used as the ball milling medium, and the mixture was ball-milled once at 400 rpm for 22 hours at a mass ratio of material:ball:anhydrous ethanol = 1:4:3. The ball milling slurry was dried, passed through an 80-mesh sieve, and pressed into shape under 2 MPa pressure. Finally, it was placed in a crucible and milled at 5°C / min. -1 The temperature was raised to 800℃ for pre-calcination, and the holding time was 350 minutes. After natural cooling, the powder was ground and passed through a 60-mesh sieve to obtain the pre-synthesized precursor powder.

[0041] (2) Preparation of calcined powder

[0042] Using Li₂CO₃, La₂O₃, and TiO₂ as raw materials, according to general chemical formula II, i.e., Li 0.33 La 0.56 The stoichiometric ratio of TiO3 is as follows: the amount of raw material Li2CO3 is 120 wt% of its stoichiometric ratio, and the amounts of the remaining raw materials are prepared according to their corresponding stoichiometric ratios. Then, using anhydrous ethanol as the ball milling medium, the mixture is rapidly ball-milled for 10 min in a high-speed ball mill at a mass ratio of material:ball:anhydrous ethanol = 1:1.5:2. The ball-milled slurry is dried, passed through an 80-mesh sieve, and then placed in a crucible and heated at 5°C / min in air atmosphere. -1The calcined material is heated to 800℃ and held for 450 minutes. After natural cooling, it is ground and passed through a 60-mesh sieve. The calcined material is then mixed with alumina powder in a granulator at a mass ratio of calcined material to alumina powder of 1:1 to obtain the calcined powder.

[0043] (3) Preparation of LLTO solid electrolyte materials

[0044] (3-1) The above-mentioned pre-synthesized precursor powder was placed in a nylon ball mill jar and ball milled for 20 hours with anhydrous ethanol as the ball milling medium at a mass ratio of material:ball:anhydrous ethanol = 1:4:3. The ball milling slurry was dried and passed through an 80-mesh sieve. The resulting material was placed in an agate mortar and granulated with a 5 wt% polyvinyl alcohol (PVA) aqueous solution as a binder (the amount of binder was 40 wt% of the material). After sieving, the powder was obtained with a particle size of 60 mesh above 80 mesh. The powder was aged for 24 hours and dried, and then pressed into a green body under a pressure of 8 MPa.

[0045] (3-2) The above-mentioned green body is vertically buried in the calcining powder, and fired at 5°C / min in an air atmosphere. -1 The product is heated to 1240℃ and calcined for 360 minutes. After natural cooling, the calcined product is obtained.

[0046] (3-3) The above-mentioned calcined products are subjected to the following surface modification treatments: 1. Wet polishing treatment, that is, the surface of the calcined products is first coarsely polished with 400-grit sandpaper, and then finely polished with 2000-grit sandpaper until the surface of the calcined products has a mirror effect; 2. Coating blocking electrodes, that is, gold electrodes are sputtered on the upper and lower surfaces of the polished calcined products for a sputtering time of 60-100s, thus obtaining A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material.

[0047] Example 2:

[0048] This embodiment presents an A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material and its preparation method, which differs from Embodiment 1 in that:

[0049] Chemical formula I is Li 0.32 La 0.56 Cu 0.01 Ti 0.94 Sb 0.06 O 2.92 F 0.08 .

[0050] In step (1), Li2CO3, La2O3, TiO2, CuO, Sb2O3 and LiF are used as raw materials.

[0051] The calcination temperature in step (3-2) is 1220℃.

[0052] Comparative example:

[0053] Using raw materials without Fe2O3, Sb2O3, and LiF as a comparative example, the remaining steps were the same as in Example 1, and Li was prepared with general chemical formula II, i.e., Li. 0.33 La 0.56 TiO3 perovskite-type solid electrolyte ceramic material.

[0054] like Figure 1 As shown, the perovskite-type solid electrolyte ceramic materials prepared in the embodiments and comparative examples of the present invention have diffraction peaks that are consistent with the standard spectra of cubic phase (PDF#04-006-2255) and tetragonal phase (PDF#97-009-2236), indicating that the obtained materials have a phase structure in which tetragonal and cubic phases coexist.

[0055] Scanning electron microscope images of the perovskite-type solid electrolyte ceramic material prepared in the embodiments of the present invention are shown below. Figure 2 As shown in the figure, the perovskite-type solid electrolyte ceramic material prepared in the embodiments of the present invention exhibits a distinct coating-like material on the grain surface (in the comparative example, no coating-like structure is formed on the surface because a large number of oxygen vacancies are not formed in the unit cell). This indicates that after lattice oxygen jumps to the crystal surface, it participates in high-temperature physicochemical reactions, resulting in more uniform grain size, clearer and more three-dimensional grain edges, fewer defect structures, and tighter inter-grain connections, thus optimizing the effective contact area between grains.

[0056] Figure 3 The EIS spectra of the samples at an ambient temperature of 25℃ were obtained, and the data were fitted using Z-View software. The fitted data of the test samples showed a high degree of agreement with the original data, with fitting errors all less than 10%. Figure 3 As shown, the embodiment exhibits a more complete and arched arc in the high-frequency region, indicating that the smaller its radius, the lower the resistance value and the higher the ionic conductivity.

[0057] The performance of the perovskite-type solid electrolyte materials prepared in the embodiments and comparative examples of the present invention is shown in Table 1.

[0058] Table 1. Performance of perovskite-type solid electrolyte materials prepared in the embodiments and comparative examples of the present invention.

[0059]

Claims

1. A three-dimensional composite doped LLTO solid electrolyte ceramic material, characterized in that: The solid electrolyte ceramic material has the general chemical formula I, Li. (0.33-x) La 0.56 (M) x Ti (1-y) Sb y O (3-z) F z Where 0.01≤x≤0.05, 0.02≤y≤0.08, 0.04≤z≤0.2; M is a highly electronegative ion with a valence higher than Li. + Li doping into the ceramic cell partially replaces the A-site. + Ions; Sb 3+ Ion doping enters the ceramic cell and partially replaces the Ti at the B site. 4+ Ions; F - Ion doping enters the ceramic cell and grain boundaries, partially replacing the O sites. 2- ion.

2. The A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material according to claim 1, characterized in that: M is Fe 3+ Cu 2+ Zn 2+ , or Cr 2+ ion.

3. The A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material according to claim 1, characterized in that: The total conductivity (σ) of the solid electrolyte ceramic material at 20–30°C is... tot ≥0.05mS·cm -1 Grain boundary conductivity (σ) gb ≥0.065mS·cm -1 Total conductivity activation energy (Ea) total The steady-state current (I) under the polarization voltage condition of ≤0.5eV and 100mV is ≤5nA.

4. The method for preparing the A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material according to any one of claims 1-3, characterized in that... Includes the following steps: (1) Preparation of pre-synthesized precursor powder Using Li₂CO₃, La₂O₃, and TiO₂ as matrix raw materials, oxides of element M are used as A-site doping materials, Sb₂O₃ as B-site doping materials, and LiF as O-site doping materials; according to the stoichiometric ratio in the general chemical formula I, the amount of raw material Li₂CO₃ is 105-125 wt%, and the amounts of the remaining raw materials are prepared according to their corresponding stoichiometric ratios; then, anhydrous ethanol is used as the ball milling medium for a single ball milling process. After drying, sieving, and pressing, the ball milled slurry is then milled at 3-6℃·min⁻¹. -1 The pre-calcination process is carried out at 700-900℃ for 300-400 minutes. After natural cooling, the pre-synthesized precursor powder is obtained by grinding and sieving. (2) Preparation of calcined powder Using Li₂CO₃, La₂O₃, and TiO₂ as raw materials, according to general chemical formula II, i.e., Li 0.33 La 0.56 The stoichiometric ratio of TiO3 is as follows: the amount of raw material Li2CO3 is 105–125 wt% of its stoichiometric ratio, and the amounts of the remaining raw materials are prepared according to their corresponding stoichiometric ratios. Then, anhydrous ethanol is used as the ball milling medium for ball milling. The ball milled slurry is dried, sieved, and then milled in air at 3–6 °C / min. -1 The calcined material is heated to 700-900℃ and held for 400-500 minutes. After natural cooling, the calcined material is ground and sieved. The calcined material is then mixed with alumina powder in a granulator at a mass ratio of calcined material to alumina powder of 1:0.8-1.2 to obtain the calcined powder. (3) Preparation of LLTO solid electrolyte materials (3-1) The pre-synthesized precursor powder is subjected to secondary ball milling with anhydrous ethanol as the ball milling medium. The ball milling slurry is dried and sieved. The resulting material is then granulated, aged, dried and pressed into a green body. (3-2) The green body is covered with sintered powder and fired in air at 3-6°C / min. -1 The product is calcined at 1130–1300℃ for 300–400 minutes and then naturally cooled to obtain the calcined product. (3-3) The calcined product is then surface modified to obtain an A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material.

5. The preparation method of the A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material according to claim 4, characterized in that: In step (1), a ball milling process is carried out once with a mass ratio of material:ball:anhydrous ethanol = 1:3.5 to 4.5:3, and the ball milling time is 20 to 24 hours; the pressing pressure is 2 to 5 MPa.

6. The preparation method of the A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material according to claim 4, characterized in that: In step (2), ball milling is performed at a mass ratio of material:ball:anhydrous ethanol = 1:1.2 to 1.8:2, and the ball milling time is 5 to 15 minutes.

7. The preparation method of the A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material according to claim 4, characterized in that: In step (3-1), a secondary ball milling process is performed at a mass ratio of material:ball:anhydrous ethanol = 1:3.5 to 4.5:3 for 18 to 22 hours. Granulation is carried out using a 5 wt% PVA aqueous solution as a binder, with the binder amounting to 25 to 45 wt% of the material. After granulation, the material is sieved to obtain powder with a particle size of 60 mesh above 80 mesh. The aging time of the powder is 20 to 24 hours. The pressing pressure is 6 to 10 MPa.

8. The preparation method of the A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material according to claim 4, characterized in that: The surface finishing process in step (3-3) is as follows:

1. Wet polishing: firstly, the surface of the calcined product is coarsely polished with 400-600 grit sandpaper, and then finely polished with 1500-2500 grit sandpaper until the surface of the calcined product has a mirror effect; 2. Coating blocking electrodes: silver / gold electrodes are sputtered onto the upper and lower surfaces of the polished calcined product for 60-100 seconds.

9. A product prepared by the method for preparing the A / B / O three-dimensional composite doped LLTO solid electrolyte ceramic material according to any one of claims 4-8.

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