Method for eliminating LLZTO pores and improving performance of solid electrolyte through oxygen-assisted sintering

Abstract

The invention discloses a method for eliminating LLZTO pores and improving the performance of a solid electrolyte through oxygen-assisted sintering, and belongs to the technical field of lithium ion batteries. The preparation method comprises the following steps: preparing tantalum-doped lithium lanthanum zirconate (LLZTO) solid electrolyte powder with a garnet type cubic phase structure through a solid-phase method, weighing medicines according to a molar ratio, carrying out wet ball-milling mixing, drying, tabletting, pre-calcining the mixed powder tablets in air, carrying out ball-milling mixing on the pre-calcined powder, drying, and carrying out cold press molding, so as to obtain the tantalum-doped lithium lanthanum zirconate solid electrolyte. And sintering at high temperature in oxygen to obtain a compact and void-free electrolyte sheet. The cubic phase Ta-doped LLZO is synthesized, pores in the LLZO are eliminated through rapid sintering in oxygen, and the density of the electrolyte is improved, so that an ion transmission channel is improved, and the ionic conductivity is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly relates to a method for eliminating pores in LLZTO by oxygen-assisted sintering to improve the performance of solid electrolytes. Background Art

[0002] Since the commercialization of lithium-ion batteries in the 1990s, they have been applied in many aspects of our lives. In recent years, due to environmental pressure and automotive emission control, countries around the world have begun to develop electric vehicles to replace fuel vehicles. Lithium-ion batteries are undoubtedly the first choice for power batteries due to their high energy density and long cycle life. However, for traditional lithium-ion batteries based on oxide cathodes and graphite anodes, their energy density is gradually approaching the theoretical upper limit. At the same time, since such batteries use organic liquid electrolytes, side reactions are inevitable during charge and discharge. Moreover, during the battery cycling process, situations such as electrolyte volatilization and leakage will cause irreversible attenuation of the battery capacity, thereby having a negative impact on the service life of lithium-ion batteries. In addition, the safety issues caused by organic flammable electrolytes have also raised public concerns about the safety of lithium-ion batteries. As an alternative, solid electrolytes have been proposed for the next generation of rechargeable batteries.

[0003] Compared with traditional liquid lithium-ion batteries, solid-state lithium batteries eliminate the hidden dangers of liquid electrolyte leakage and corrosion and have high thermal stability; they have a stable and wide electrochemical window, can match high-voltage cathode materials, break through the limitation of the electrochemical window of traditional liquid lithium-ion batteries on the selection of cathode materials, and are conducive to improving battery performance such as energy density; most are single-ion conductors, with few charge-discharge side reactions and long cycle life; higher output voltages can be obtained through internal series connection by multi-layer stacking technology.

[0004] As the core component of solid-state lithium batteries - solid electrolytes are the key to achieving high energy density, high cycle stability, and high safety performance of solid-state lithium batteries. Solid electrolytes are also known as fast ion conductors and can be roughly divided into inorganic solid electrolytes, polymer solid electrolytes, and composite solid electrolytes according to the components of solid electrolytes. Inorganic solid electrolytes mainly include sulfides and oxides. Sulfide electrolytes have relatively high ionic conductivity, up to 10 -3 -10 -2 S·cm -1 , but have poor chemical compatibility with lithium metal anodes. Moreover, sulfide electrolytes are very sensitive to the environment and are prone to decomposition when exposed to water and oxygen in the air, releasing toxic gas H2S, which limits the application of sulfide electrolytes. Compared with sulfide electrolytes, oxide electrolytes have the advantages of high safety performance, good stability, low cost, and environmental friendliness, and are a research hotspot for energy storage applications.

[0005] Garnet-phase lithium lanthanum zirconium oxide (LLZO) is one of the most promising candidate materials for oxide solid electrolytes, with advantages such as good chemical and thermal stability, high ionic conductivity, and wide electrochemical window. LLZO has two crystalline phases, cubic phase (c-LLZO) at high temperature and tetragonal phase (t-LLZO) at low temperature. The ionic conductivity of c-LLZO is two orders of magnitude higher than that of t-LLZO. Therefore, c-LLZO is more ideal in practical applications. In order to obtain c-LLZO at room temperature, doping modification is a feasible strategy. Doping elements to replace cations Li, La or Zr can stabilize the cubic phase structure. Among them, Ta-doped LLZTO (LLZTO) has the combined advantages of high ionic conductivity and stability to Li metal, and is considered to be the most promising one.

[0006] In addition to high ionic conductivity, it is also very important to obtain LLZO with few defects and high mechanical strength. Li dendrites may grow inside LLZO and penetrate the electrolyte, causing internal short circuits. Therefore, eliminating the pores in LLZO and improving its density and comprehensive performance are key issues that need to be urgently addressed in the field of solid-state lithium battery research. However, the preparation of dense LLZO electrolytes requires harsh experimental conditions, such as spark plasma sintering, field-assisted sintering technology, and hot pressing sintering technology. These methods often require special equipment and high manufacturing costs, which are not conducive to large-scale production and application.

[0007] Therefore, how to find a low-cost preparation method that can improve the density of LLZO while having high electrochemical performance is an urgent problem to be solved in the current field of solid-state lithium battery research. Summary of the invention

[0008] The purpose of the present invention is to solve the problems existing in the prior art and provide a method for eliminating LLZTO pores by oxygen-assisted sintering to improve the performance of solid electrolytes. The pores in LLZTO can be eliminated by rapid sintering in oxygen, and the density of the electrolyte can be increased, thereby improving the ion transmission channel and achieving the effect of improving the ion conductivity of the solid electrolyte.

[0009] In order to achieve the above technical objectives, the present invention is implemented by the following technical solutions:

[0010] A method for eliminating LLZTO pores by oxygen-assisted sintering to improve the performance of solid electrolytes comprises the following steps:

[0011] (1) mixing a lithium source, a lanthanum source, a zirconium source and a tantalum source according to a preset molar ratio, performing wet ball milling, and drying to obtain a mixed precursor;

[0012] (2) tableting the mixed precursor;

[0013] (3) Pre-calcine the tablet in air, crush and grind it after cooling to obtain pre-calcined powder;

[0014] (4) Perform wet ball milling on the pre-calcined powder, and obtain refined powder after drying;

[0015] (5) Perform high-pressure tabletting on the refined powder to form a green body;

[0016] (6) Perform high-temperature sintering on the green body in an oxygen atmosphere to obtain a dense and void-free solid electrolyte ceramic sheet. In step (1), the lithium source includes LiOH·H2O, the lanthanum source includes La2O3, the zirconium source includes ZrO2, and the tantalum source includes Ta2O5; the molar ratio of the lithium source, lanthanum source, zirconium source, and tantalum source is (4-10):(1-3):(1-2):(0.1-0.4). The wet ball milling in steps (1) and (4) both uses isopropanol as the solvent, and the ball milling medium is zirconia balls or alumina balls; the ball-to-material ratio of the wet ball milling in step (1) is 1:3-1:5, the ball milling speed is 200-500 rpm, and the ball milling time is 6-16 hours. The pre-calcination temperature in step (3) is 500-700 °C, the heat preservation time is 8-12 hours, and the heating rate is 2-5 °C / min; the pressure of the tabletting in step (5) is 200-300 MPa, and the pressure holding time is 1-3 minutes.

[0017] In step (6), the high-temperature sintering temperature is 1100-1250 °C, the calcination time is 1-3 hours, and the oxygen flow rate is 0.5-2 L / min; the heating rate of the high-temperature sintering is 5-10 °C / min.

[0018] The relative density of the prepared solid electrolyte is calculated by the following formula:

[0019]

[0020] ρ ∞ is the theoretical maximum relative density, ρ0 is the density of the LLZTO powder, is the oxygen partial pressure, R is the gas constant, n is the reaction order of the oxygen partial pressure inhibition effect, Ea is the evaporation activation energy, and C, Q, k, m are parameters to be fitted.

[0021] A dense and void-free inorganic solid electrolyte ceramic material, characterized in that it is prepared by the above preparation method, and the chemical general formula of the material is Li 7-x La3Zr 2-x Ta x O 12 , where 0 < x ≤ 2; its relative density ≥ 97%, and the ionic conductivity ≥ 5.0×10 -4 S / cm.

[0022] The application of the described inorganic solid electrolyte ceramic material in lithium-ion batteries, solid-state lithium batteries or electrochemical energy storage devices.

[0023] The beneficial effects of the present invention are as follows: 1. The electrolyte material prepared by the method disclosed in this application is a tantalum-doped lithium lanthanum zirconium oxide (LLZO) solid electrolyte sheet. This application not only realizes tantalum doping to achieve the effects of stabilizing the cubic phase and improving the material density, but also eliminates the pores in LLZTO through rapid sintering in oxygen, enhancing the electrolyte density, thereby improving the ion transport channels and achieving the effect of increasing the ionic conductivity of the solid electrolyte.

[0024] 2. This application uses rapid calcination in oxygen to prepare the solid electrolyte. When the pre-calcination temperature is 700 °C and the electrolyte sheet is calcined at a high temperature in oxygen for 1 h, the ionic conductivity can reach 6.07×10 -4 S / cm. Description of the Drawings

[0025] Figure 1 is the X-ray diffraction (XRD) pattern of the final product obtained before and after calcination of the LLZTO fine powder in Example 1 in oxygen;

[0026] Figure 2 (a) is the cross-sectional scanning electron microscope (SEM) image of the LLZTO solid electrolyte ceramic material sintered in oxygen in Example 1, Figure 2 (b) is the SEM image of the LLZTO solid electrolyte sintered in air in Comparative Example 1. Detailed Embodiments

[0027] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the essence of the present invention, modifications and substitutions made to the methods, steps or conditions of the present invention all fall within the scope of the present invention.

[0028] To achieve the above technical objectives, in some typical embodiments, the present invention is realized through the following technical solutions: A method for eliminating pores in LLZTO by oxygen-assisted sintering to improve the performance of solid electrolytes, comprising the following steps:

[0029] 1) Wet ball-mill the raw materials LiOH·H2O, ZrO2, Ta2O5, and La2O3. After the ball-milling is completed, dry to obtain a mixed precursor;

[0030] 2) Press the mixed precursor;

[0031] 3) Pre-calcine the pressed mixed precursor, cool and then crush and grind to obtain the LLZTO pre-calcined powder;

[0032] 4) Wet ball-mill the pre-calcined powder. After the ball-milling is completed, dry;

[0033] 5) Press the powder that has been pre-calcined into tablets;

[0034] 6) Rapidly calcine the LLZTO green body in an oxygen atmosphere to obtain a dense and void-free electrolyte sheet.

[0035] Further, in step 1), the molar ratio of the raw materials LiOH·H2O, La2O3, ZrO2, and Ta2O5 is 4-10:1-3:1-2:0.1-0.4.

[0036] Further, in step 1), when performing wet ball milling, grinding balls and isopropanol solvent need to be added to the raw materials. The mass ratio of the raw materials, grinding balls, and isopropanol solvent is 1:3:5. The ball milling speed is 200-300 rpm, and the ball milling time is 6-12 h; the drying temperature is 80-90 °C.

[0037] Further, in step 2), the tableting pressure is 5-10 Mpa, and the pressure holding time is 10 s.

[0038] Further, in step 3), the pre-calcination temperature of the precursor material is 500-700 °C, the heating rate is 2-5 °C / min, the heat preservation time is 8-12 h, and after the heat preservation ends, it is cooled with the furnace.

[0039] Further, in step 4), when performing wet ball milling, grinding balls and isopropanol solvent need to be added to the LLZTO pre-calcined powder. The mass ratio of the pre-calcined powder, grinding balls, and isopropanol solvent is 1:4:7. The ball milling speed is 300-500 rpm, and the ball milling time is 8-16 h.

[0040] Further, in step 5), the tableting pressure is 200-300 Mpa, and the pressure holding time is 2 min.

[0041] Further, in step 6), the calcination temperature in oxygen is 1100-1250 °C, and the calcination time is 1-3 h.

[0042] The dense and void-free inorganic solid electrolyte ceramic material prepared by the above method has the material chemical formula Li 7-x La3Zr 2-x Ta x O 12 , where 0 < x ≤ 2. This electrolyte material can be further applied in lithium-ion batteries, micro-miniature power sources and devices, electrochromic devices, and other electrochemical processes.

[0043] Example 1

[0044] This example discloses a method for eliminating pores in LLZTO by oxygen-assisted sintering to improve the performance of solid electrolytes:

[0045] 1) Weigh the raw materials LiOH·H2O, La2O3, ZrO2 and Ta2O5 according to the molar ratio of 7.36:1.5:1.4:0.3. Among them, the weighed amount of LiOH·H2O needs to exceed the calculated theoretical content by 15%, which is beneficial to make up for the lithium loss during subsequent sintering.

[0046] 2) Place the raw materials weighed in the previous step into a planetary ball mill jar, add grinding zirconium balls and isopropanol solvent for ball milling and mixing. The mass ratio of the raw materials, grinding balls and isopropanol solvent is 1:3:5. The ball milling speed is 200 - 300 rpm, and the ball milling time is 10 h. After the ball milling is completed, rotary evaporate and dry the ball milling mixture at 90 °C to obtain the mixed precursor powder.

[0047] 3) Place the mixed precursor powder on a tablet press for tableting, with a pressure of 10 Mpa and a pressure holding time of 10 s.

[0048] 4) Place the mixed precursor tablet in a muffle furnace and pre-calcine it in an air atmosphere. The calcination temperature is 700 °C, the heating rate is 5 °C / min, the heat preservation time is 10 h, and it is cooled to room temperature with the furnace. Crush and grind the tablet to obtain the pre-calcined LLZTO powder.

[0049] 5) Put the pre-calcined LLZTO powder into a planetary ball mill jar, add grinding zirconium balls and isopropanol solvent for ball milling and mixing. The mass ratio of the pre-calcined LLZTO powder, grinding balls and isopropanol is 1:4:7. The ball milling speed is 400 rpm, and the ball milling time is 10 h. After the ball milling is completed, rotary evaporate and dry, and grind to obtain the LLZTO fine powder.

[0050] 6) Put the pre-calcined LLZTO fine powder into a mold for uniaxial tableting, with a pressure of 220 Mpa and a pressure holding time of 2 min to obtain the LLZTO green body.

[0051] 7) Use a tube furnace to perform high-temperature calcination on the LLZTO green body prepared in the previous step in an oxygen atmosphere. The calcination temperature is 1250 °C and the time is 1 h to obtain a dense and void-free LLZTO solid electrolyte ceramic material.

[0052] Example 2

[0053] The difference between this example and Example 1 is only that the pre-calcination temperature in step 4) is adjusted to 600 °C, and the rest of the steps and processes are the same.

[0054] Example 3

[0055] The difference between this example and Example 1 is only that the pre-calcination temperature in step 4) is adjusted to 500 °C, and the rest of the steps and processes are the same.

[0056] Comparative Example 1

[0057] The difference between this example and Example 1 is only that the oxygen atmosphere in step 7) is adjusted to air, and the remaining steps and processes are the same.

[0058] Comparative Example 2

[0059] The difference between this example and Example 1 is that the pre - calcination temperature in step 4) is adjusted to 600 °C, and the oxygen atmosphere in step 7) is adjusted to air, and the remaining steps and processes are the same.

[0060] Comparative Example 3

[0061] The difference between this example and Example 1 is that the pre - calcination temperature in step 4) is adjusted to 500 °C, and the oxygen atmosphere in step 7) is adjusted to air, and the remaining steps and processes are the same.

[0062] Relevant performance tests:

[0063] 1. Figure 1 Fig. shows the X - ray diffraction (XRD) patterns of the final products obtained before and after calcination of the pre - calcined LLZTO fine powder in Example 1 in oxygen. It can be seen from the figure that the characteristic peaks of the samples before and after calcination in oxygen match well with the standard PDF card, and there are no other impurity peaks, indicating that the phase of the powder is a cubic phase. The difference between the pre - calcined and sintered LLZTO powders is that the XRD diffraction peaks of the sintered LLZTO powder become sharper and stronger, indicating that the crystallinity of LLZTO is improved after high - temperature sintering in oxygen.

[0064] 2. Figure 2 Fig. presents the cross - sectional morphology of the LLZTO solid - state electrolyte ceramic materials prepared in Example 1 and Comparative Example 1. It can be seen that the LLZTO material sintered in oxygen is uniform and dense without voids; while the electrolyte sintered in air contains a large number of cavities.

[0065] 3. The relative density of the calcined solid - state electrolyte was measured by the Archimedes drainage method. The theoretical density of LLZTO was calculated based on the crystal structure parameters:

[0066]

[0067] Where:

[0068] ρ theory : Theoretical density of LLZTO

[0069] Z: The number of formula units per unit cell (usually 8 for the cubic phase of LLZO).

[0070] M: Molar mass of the formula unit (g / mol).

[0071] N A : Avogadro's constant (6.022×10 23 mol -1 ).

[0072] V cell : Unit cell volume (cm 3 . The unit cell parameters need to be converted from to cm).

[0073] The results are shown in Table 1.

[0074] Table 1

[0075]

[0076]

[0077] From the comparison between the examples and the comparative examples, it can be seen that the relative density of the solid electrolyte prepared by the method of the present application is significantly improved, and the relative density can still remain above 97% when the pre-calcination temperature drops to 500 °C.

[0078] 4. Test of ionic conductivity of solid electrolyte

[0079] The surface of the sintered solid electrolyte ceramic sheet is polished to be smooth. After removing impurities such as Li2CO3 and LiOH on the surface, it is placed in a glove box for standby. A layer of Ag is brushed on both sides of the solid electrolyte membrane to form an Ag / LLZTO / Ag blocking system. A lithium sheet is used as the electrode, and a button battery is used for encapsulation. An electrochemical workstation is used to apply a small-amplitude sine wave to the button battery, with an AC amplitude of 0.01 V and a test temperature of room temperature. The frequency of the small-amplitude sine wave applied is changed within the test frequency range of 1 Hz to 1 MHz to obtain a series of impedances at different frequencies. With the real part of the impedance as the horizontal axis, the imaginary part as the vertical axis, and each point representing a different frequency, a Nyquist diagram is obtained. The left side of this diagram has a high frequency and is called the high-frequency region, which is semi-circular; the right side has a low frequency and is called the low-frequency region, which is linear. According to the equivalent circuit analysis, the intersection of the semi-circle and the real axis at low frequencies corresponds to the ionic resistance R of the solid electrolyte ceramic sheet. The conductivity is calculated according to the following formula.

[0080]

[0081] Among them, σ represents the conductivity, with the unit of S / m; L represents the length of the solid electrolyte ceramic sheet, with the unit of m; A represents the cross-sectional area of the solid electrolyte ceramic sheet, with the unit of m 2 ; R represents the ionic resistance of the solid electrolyte ceramic sheet.

[0082] The batteries of each example and comparative example are prepared respectively according to the above method, and various performance parameters are measured. The results are shown in Table 2.

[0083] Table 2

[0084]

[0085]

[0086] It can be seen from the comparison between the examples and the comparative examples that the solid electrolyte prepared by the method of the present application has higher ionic conductivity, which helps to further improve the electrochemical performance of the solid-state battery. At the same pre-calcination temperature, LLZTO sintered in oxygen has higher conductivity than that sintered in air. By comparing Table 1, it is found that the conductivity of LLZTO is related to the relative density. Rapid sintering in oxygen is beneficial to improving the density of the LLZTO solid electrolyte, improving the ion transport channels, and increasing the ionic conductivity.

[0087] Furthermore, a prediction model of relative density, sintering program, and oxygen partial pressure is constructed: Since high temperature accelerates atomic diffusion (following the Arrhenius law), promoting particle rearrangement and densification; in addition, the volatilization rate increases exponentially with increasing temperature, but high oxygen partial pressure can inhibit this effect; moreover, during sintering, increasing temperature reduces the surface energy (γ), while promoting grain boundary migration and affecting the pore closure rate. The total porosity consists of two parts:

[0088] Matrix porosity (φ base ): Dominated by the densification process controlled by diffusion, related to both T and .

[0089] Volatilization-induced porosity (Δφ vol ): Generated by lithium volatilization, coupled with T and .

[0090] Based on the sintering kinetics theory, the relationship between the diffusion coefficient D and temperature is:

[0091]

[0092] where Q is the diffusion activation energy and R is the gas constant. Assuming that the matrix porosity decreases with the increase of D(T), a modified exponential decay model is introduced:

[0093]

[0094] where k and m are fitting parameters, and φ ∞ is the theoretical limit porosity.

[0095] The lithium volatilization rate R vol is co-regulated by T and . Assuming that the volatilization porosity is proportional to the volatilization rate:

[0096]

[0097] Among them, E a is the activation energy of volatilization (which can also be determined by the volatilization weight loss experiment), n is the reaction order of oxygen partial pressure, and C is a proportionality constant.

[0098] The total porosity is the superposition of the two, that is:

[0099]

[0100] After expansion:

[0101]

[0102] Further construct the correlation between relative density and porosity, and correct the model:

[0103] ρ rel = 1 - φ = 1 - (φ base + Δφ vol ) = (1 - φ base ) - Δφvol

[0104] Among them, ρ rel is the relative density, φ base is the relative density of the matrix, is the density loss due to volatilization;

[0105] That is:

[0106] ρ base : Matrix relative density dominated by diffusion;

[0107] Δρ vol : Density loss caused by lithium volatilization (positive value).

[0108] Based on the sintering kinetics theory, high temperature and high oxygen partial pressure promote densification. The modified S-shaped saturation growth model is adopted:

[0109]

[0110] ρ ∞ : Theoretical maximum relative density (set to be equal to ρ theory in this patent);

[0111] ρ0: Initial relative density (unsintered state at low temperature and low oxygen partial pressure, set ρ0 = 60% in this patent);

[0112] k, m: Enhancement coefficients of oxygen partial pressure on diffusion;

[0113] Q: Diffusion activation energy;

[0114] R: Gas constant (8.314 J / (mol·K)).

[0115] Lithium volatilization leads to density loss, and its rate is inhibited by temperature and oxygen partial pressure:

[0116]

[0117] C: Proportional constant of volatilization loss;

[0118] E a : Activation energy of volatilization;

[0119] n: Reaction order of the oxygen partial pressure inhibition effect, taken as 1 in this embodiment.

[0120] Combining the matrix density and volatilization loss, the total relative density expression is obtained:

[0121]

[0122] ρ ∞ Set to 1; E a Set to 119 kJ / mol.

[0123] Each time, 50% of the data is used for fitting, and the remaining 50% of the data is used for verification. The predicted values and errors of the verification set are calculated. The distribution intervals of the parameters obtained by fitting are: k: 1.5×10 -5 -1.7×10 -5 、m: 0.80 - 0.82、C: 1.1×10 6 -1.4×10 6 , and Q takes 90 - 92 kJ / mol.

[0124] Table 3

[0125]

[0126]

[0127] Through the three - selection method verification, the corrected model shows extremely excellent prediction accuracy (RMSE = 0.13%, R 2 = 0.9996) in the range of oxygen partial pressure 0.2 - 1.0 and temperature 500 - 700 °C, explaining that at high oxygen partial pressure: the increase in temperature significantly improves the relative density (diffusion - dominated), while at low oxygen partial pressure: the increase in temperature slightly reduces the relative density (volatilization - dominated). The model parameters of the present invention have high stability, verifying its reliability and providing a solid theoretical tool for the optimization of the LLZTO sintering process.

Claims

1. A preparation method for eliminating LLZTO pores by oxygen-assisted sintering to improve the performance of solid electrolyte, characterized in that: The following steps are involved: (1) mixing a lithium source, a lanthanum source, a zirconium source and a tantalum source according to a preset molar ratio, performing wet ball milling, and drying to obtain a mixed precursor; (2) tableting the mixed precursor; (3) pre-calcining the pressed tablets in air, and then pulverizing and grinding the tablets to obtain pre-calcined powder after cooling; (4) wet-milling the pre-calcined powder to obtain a refined powder after drying; (5) subjecting the refined powder to high-pressure tableting to form a green sheet; (6) The green body is sintered at high temperature in an oxygen atmosphere to obtain a dense and void-free solid electrolyte ceramic sheet.

2. The preparation method according to claim 1, characterized in that: In step (1), the lithium source includes LiOH·H2O, the lanthanum source includes La2O3, the zirconium source includes ZrO2, and the tantalum source includes Ta2O5; the molar ratio of the lithium source, lanthanum source, zirconium source and tantalum source is (4-10):(1-3):(1-2):(0.1-0.4).

3. The preparation method according to claim 1, characterized in that: The wet ball milling in step (1) and step (4) both uses isopropanol as a solvent, and the ball milling medium is a zirconium ball or an alumina ball; the ball-to-material ratio of the wet ball milling in step (1) is 1:3 to 1:5, the ball milling speed is 200 to 500 rpm, and the ball milling time is 6 to 16 hours.

4. The preparation method according to claim 1, characterized in that: In step (3), the pre-calcination temperature is 500-700° C., the holding time is 8-12 hours, and the heating rate is 2-5° C. / min; in step (5), the tabletting pressure is 200-300 MPa, and the holding time is 1-3 minutes.

5. The preparation method according to claim 1, characterized in that: In step (6), the temperature of high-temperature sintering is 1100-1250° C., the calcination time is 1-3 hours, the oxygen flow rate is 0.5-2 L / min; and the heating rate of the high-temperature sintering is 5-10° C. / min.

6. The preparation method according to claim 1, characterized in that: The relative density of the prepared solid electrolyte is calculated by the following formula: ρ ∞ is the theoretical maximum relative density, ρ0 is the density of LLZTO powder, is the oxygen partial pressure, R is the gas constant, n is the reaction order of the oxygen partial pressure inhibition effect, Ea is the volatilization activation energy, and C, Q, k, and m are the parameters to be fitted.

7. A dense, void-free inorganic solid electrolyte ceramic material, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 6, and the chemical formula of the material is Li 7-x Ln3Z 2-x Ta x O 12 , where 0<x≤2; Its relative density is ≥97%, and its ionic conductivity is ≥5.0×10 -4 S / cm.

8. Use of the inorganic solid electrolyte ceramic material according to claim 7 in lithium ion batteries, solid-state lithium batteries or electrochemical energy storage devices.

Images