A high ionic conductivity lithium lanthanum titanate solid electrolyte material and its preparation and application

Abstract

The present invention belongs to the technical field of lithium-ion solid-state batteries, and discloses a high-ionic conductivity lanthanum titanate lithium solid electrolyte material and its preparation and application. The preparation method of the high-ionic conductivity lanthanum titanate lithium solid electrolyte material is to use a lithium source, a titanium source and a lanthanum source as precursors, and prepare them into lanthanum titanate lithium solid ceramic sheets through ball milling mixing, drying, pre-burning, ball milling crushing, drying, granulation, tableting, sintering and other processes, and then perform a high-temperature quenching process to obtain a high-ionic conductivity lanthanum titanate lithium solid electrolyte material. The present invention adopts a solid electrolyte preparation process of first sintering and then quenching treatment, which can effectively reduce the grain boundary impedance of lanthanum titanate lithium ceramics, thereby improving the ionic conductivity of lanthanum titanate lithium ceramic solid electrolytes to 10 ‑4 ~10 ‑3 On the other hand, the process is simple and easy to control, which can effectively ensure that the ceramic reduces the grain boundary resistance with significant results.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion solid-state batteries, and particularly relates to a lithium lanthanum titanate solid electrolyte material with high ionic conductivity, its preparation and application. Background Art

[0002] Lithium lanthanum titanate (Li 3x La 2 / 3-x TiO3 (0.04 < x < 0.17)) is a solid ceramic electrolyte with a perovskite structure. Among them, Li 3x La 2 / 3-x In TiO3, La and Li jointly occupy the A site of the perovskite structure. Among them, La plays a very crucial role in the conductivity. On the one hand, the high-valent La occupies the A position, causing partial voids at the A position. On the other hand, the relatively large-radius La occupying the A position is conducive to the formation of relatively large pores, which is also conducive to the migration of lithium ions. Especially its room-temperature bulk ionic conductivity is as high as 10 -3 S / cm, which has attracted the attention of many researchers. However, the lithium lanthanum titanate solid electrolyte has obvious defects. The lithium lanthanum titanate cooled with the furnace after simple high-temperature sintering is prone to segregation of titanium elements at grain boundaries, more ceramic defects, non-dense structure, incomplete grain development, and a large proportion of grain boundaries. Various comprehensive factors lead to a very large grain boundary impedance, seriously reducing the total ionic conductivity of the material (between 10 -5 and 10 -6 S / cm), greatly limiting its application. To solve the above problems, the commonly used method at present is to dope and modify it or compound it to reduce the grain boundary impedance, so as to improve the total ionic conductivity. However, the improvement effect of these methods is not obvious, and the process is complex and the preparation cost is high. Summary of the Invention

[0003] In order to overcome the above-mentioned disadvantages and deficiencies of the prior art, the primary object of the present invention is to provide a preparation method for a lithium lanthanum titanate solid electrolyte material with high ionic conductivity. This method can effectively reduce the grain boundary impedance of lithium lanthanum titanate ceramics, thereby improving the ionic conductivity of lithium lanthanum titanate solid electrolytes.

[0004] Another object of the present invention is to provide a lithium lanthanum titanate solid electrolyte material with high ionic conductivity prepared by the above method.

[0005] Another object of the present invention is to provide the application of the above lithium lanthanum titanate solid electrolyte material with high ionic conductivity.

[0006] The object of the present invention is achieved by the following solutions:

[0007] A preparation method for a lithium lanthanum titanate solid electrolyte material with high ionic conductivity, comprising the following steps:

[0008] (1) Mix the required lithium source, titanium source, lanthanum source, and solvent according to the chemical formula of lithium lanthanum titanate by ball milling, then take it out and dry it to obtain a lithium lanthanum titanate precursor mixture, and pre-burn the precursor mixture to obtain a lithium lanthanum titanate ceramic material;

[0009] (2) Perform secondary ball milling and drying on the pre-burned lithium lanthanum titanate ceramic material in step (1) to obtain lithium lanthanum titanate ceramic powder, then granulate and press the powder, and then perform debinding and sintering, and cool it in the furnace to room temperature to obtain a lithium lanthanum titanate ceramic sheet solid electrolyte with a perovskite structure;

[0010] (3) Perform a high-temperature quenching process on the lithium lanthanum titanate ceramic sheet obtained in step (2), and control the cooling rate to be 100 - 300 °C / min to obtain a lithium lanthanum titanate ceramic sheet solid electrolyte with high ionic conductivity.

[0011] The "according to the formula" mentioned in step (1) means selecting the corresponding amounts of lithium source, titanium source, and lanthanum source according to Li 3x La 2 / 3-x TiO3 (0.04 < x < 0.17), that is, the amounts of lithium source, titanium source, and lanthanum source satisfy the molar ratio of lithium element, titanium element, and lanthanum element of 3x:1:(2 / 3 - x), (0.04 < x < 0.17);

[0012] The lithium source mentioned in step (1) is at least one of lithium carbonate, lithium hydroxide, lithium sulfate, lithium oxalate, lithium acetate, and lithium chloride; the titanium source is at least one of titanium dioxide and tetrabutyl titanate; the lanthanum source is at least one of lanthanum oxide, lanthanum carbonate, and lanthanum acetate.

[0013] The solvent mentioned in step (1) is at least one of water, ethanol, and acetone.

[0014] In the ball milling and mixing in step (1), the ball-to-material ratio (that is, the mass ratio of grinding balls to materials) is (3 - 5):1, where the mass ratio of powder to solvent is 1:1 - 1.5, and ball mill the mixture at a rotation speed of (200 - 600) r / min on a ball mill for 12 - 24 h.

[0015] The drying temperature in step (1) is 80 - 120 °C, and the drying time is 12 - 24 h.

[0016] The pre-burning temperature in step (1) is 900 - 1200 °C, and the pre-burning time is 1 - 10 h.

[0017] The rotation speed of the secondary ball milling in step (2) is (200 - 600) r / min, the ball milling time is 12 - 24 h, the ball-to-material ratio (that is, the mass ratio of grinding balls to materials) is (3 - 5):1, where the mass ratio of powder to solvent is 1:1 - 1.5, and the solvent is at least one of water, ethanol, and acetone;

[0018] The drying temperature in step (2) is 80-120° C., and the drying time is 12-24 hours.

[0019] The binder added during the granulation process in step (2) is at least one of a 5wt% PVB-ethanol solution and a 5wt% PVA aqueous solution, and the amount of the binder is 5-15wt% of the powder, and the powder is sieved with an 80-200 mesh sieve to obtain a ceramic powder with uniform particles;

[0020] In the present invention, adding a binder for granulation is beneficial to improving the fluidity of the powder, so that the powder can evenly fill the mold, avoiding defects such as voids, loose corners, and layer cracks, thereby making the sintered ceramics more uniform and dense.

[0021] The tableting in step (2) is to press the ceramic green sheets into sheets with a diameter of 10-15 mm at 10-30 MPa, with a holding time of 1-5 min;

[0022] The debinding and sintering described in step (2) refer to debinding the pressed tablets before sintering. The debinding method is to heat the green ceramic sheet from room temperature to 100-300°C at 1-10°C / min and keep it warm for 1-2 hours; the second stage is to heat it to 380-450°C at 3-5°C / min and keep it warm for 4-6 hours; the third stage is to heat it to 500-700°C at 5-8°C / min and keep it warm for 1-2 hours, and finally cool it to room temperature with the furnace. The segmented debinding process before sintering is conducive to slowly removing the binder and ensuring that the ceramic sheet does not undergo significant deformation, reducing the generation of pores or other defects in it during subsequent sintering.

[0023] The sintering described in step (2) adopts a three-stage heat treatment process, first heating from room temperature to 100-300°C at 1-10°C / min and keeping warm for 0.5-3h; then heating to 400-600°C at 3-10°C / min and keeping warm for 0.5-3h, and then heating to 1200-1400°C at 4-10°C / min and keeping warm for 5-10h to allow the ceramic grains to grow fully, and finally cooling to room temperature with the furnace to obtain a lanthanum titanate lithium ceramic sheet solid electrolyte with a perovskite structure.

[0024] Preferably, the high temperature quenching process in step (3) refers to heating the sintered ceramic sheet to a sintering temperature of 1200-1400°C at 8-10°C / min under a certain atmosphere in a tube furnace, and keeping it warm for 1-5h, and then quenching it in air or in a quenching agent, controlling the cooling rate to 100-300°C / min, thereby obtaining a lanthanum titanate lithium ceramic sheet solid electrolyte with high ionic conductivity.

[0025] The heat treatment temperature in the high-temperature quenching process is 1200-1400°C, the heating rate is 8-15°C / min, and the treatment time is 1-5h. At this temperature, the ions in the lanthanum titanate lithium ceramic sheet crystals diffuse, especially driving the titanium ions accumulated at the grain boundaries to diffuse into the grains, thereby forming a uniformly distributed ceramic solid solution.

[0026] The atmosphere in the high-temperature quenching process tubular furnace can be either oxygen or high-oxygen air (oxygen content greater than 30%). By quenching in an oxygen atmosphere, oxygen vacancy defects in the ceramic material can be significantly reduced, improving the electrochemical properties of the ceramic material. At the same time, oxygen can fully enter the lanthanum titanate lithium perovskite structure, assisting the diffusion of titanium ions from the grain boundaries to the entire grain, thereby reducing the accumulation of titanium ions at the grain boundaries.

[0027] In the high-temperature quenching process, the quenching medium is air or other quenching agents, including water, quenching oil, etc., and the quenching rate is controlled at 100-300℃ / min, and the material is quickly cooled to room temperature. This quenching treatment helps prevent titanium ions from re-accumulating at the grain boundaries, thereby avoiding blocking the ion channels at the grain boundaries, thereby effectively reducing the grain boundary resistance. Among them, if the cooling rate is below 100℃ / min, titanium ions will still segregate at the grain boundaries; if the cooling rate is higher than 300℃ / min, the lanthanum titanate lithium ceramic sheet will crack or even break due to insufficient stress release.

[0028] A high ionic conductivity lithium lanthanum titanate solid electrolyte material prepared by the above method.

[0029] The application of the above-mentioned high ionic conductivity lithium lanthanum titanate solid electrolyte material in lithium-ion solid-state batteries, electrochromic devices and ion-conducting sensor devices.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] The present invention adopts a solid electrolyte preparation process of first sintering and then quenching treatment to obtain a high-ionic conductivity lanthanum lithium titanate solid electrolyte, which can effectively reduce the grain boundary impedance of the lanthanum lithium titanate ceramic, thereby improving the ionic conductivity of the lanthanum lithium titanate ceramic solid electrolyte.

[0032] 1. The present invention first uses a ball milling debinding process to improve the fluidity of the powder, so that the powder can evenly fill the mold, avoiding defects such as voids, loose corners, and layer cracks. Then, through the sintering process, the grains in the ceramic sheet can fully grow, the grain boundaries are reduced, and a large number of pores inside the ceramic are discharged, thereby forming a lanthanum titanate lithium ceramic sheet with a higher density.

[0033] 2. By adopting a high-temperature quenching process, under heat preservation in an oxygen atmosphere, on the one hand, the ions in the lanthanum titanate lithium ceramic sheet crystals are freely diffused, especially driving the titanium ions accumulated at the grain boundaries to diffuse into the grains, thereby forming a ceramic solid solution with uniform element distribution, and then rapidly cooling to room temperature. Under this quenching treatment, it helps to prevent the titanium ions from re-accumulating at the grain boundaries, which significantly reduces the segregation of titanium elements at the grain boundaries, thereby avoiding the blockage of ion channels at the grain boundaries and the generation of extremely large grain boundary impedance; at the same time, due to the effect of the oxygen atmosphere, the oxygen vacancy defects in the ceramic material can be significantly reduced, and the electrochemical properties of the ceramic material can be improved. At the same time, the oxygen element can fully enter the lanthanum titanate lithium perovskite structure, assisting the diffusion of titanium ions from the grain boundaries to the entire grain, thereby reducing the accumulation of titanium ions at the grain boundaries.

[0034] 3. At the same time, the lanthanum titanate lithium solid electrolyte obtained by the above-mentioned preparation method of first ball milling, debinding and sintering and then high-temperature quenching treatment has higher crystallinity, less impurities and higher density, which has a significant synergistic effect on improving the ionic conductivity of the material.

[0035] Therefore, the grain boundary impedance of the lanthanum titanate lithium ceramic sheet solid electrolyte material prepared by this method is significantly reduced, which greatly improves its total ionic conductivity to 10 -4 ~10 -3 On the other hand, the process is simple and easy to control, which can effectively ensure that the ceramic reduces the grain boundary resistance with significant results. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 XRD diffraction patterns of Comparative Example 1(a) and Example 1(b) of the present invention;

[0037] Figure 2 are SEM images of Comparative Example 1(a) and Example 1(b) of the present invention;

[0038] Figure 3 1(a) and 1(b) of the present invention;

[0039] Figure 4 1 and 2 are electrochemical impedance spectroscopy diagrams of comparative example 1 and embodiment 1 of the present invention, wherein a is the full spectrum of the test; b is an enlarged view of the high-frequency part of the circle in a. DETAILED DESCRIPTION

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0041] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially. Unless otherwise specified, the reagents used in the examples can be purchased from conventional commercial sources.

[0042] Example 1

[0043] According to lithium lanthanum titanate (Li 0.5 La 0.5 The chemical formula of TiO3 is designed with Li2CO3, TiO2 and La2O3 as raw materials, anhydrous ethanol as solvent, a ball-to-material ratio of 3:1, and a powder-to-solvent mass ratio of 1:1. The mixture is ball-milled at a speed of 300 r / min for 12 hours, then dried in an 80°C oven for 12 hours, and pre-calcined in a high-temperature chamber furnace at 1100°C for 3 hours;

[0044] The powder was put into the ball mill again with a ball-to-material ratio of 3:1 and a powder-to-solvent mass ratio of 1:1. The ball milling was continued at a speed of 300 r / min for 12 hours. Then, the powder was dried in a blast oven at 80°C for 12 hours to obtain ultrafine and uniform lanthanum titanate lithium ceramic powder. A 5wt% PVB ethanol solution accounting for 10% of the powder mass was added for granulation. The powder was sieved with a 100-mesh sieve and pressed into ceramic green sheets using a mold with a diameter of 12.7 mm at 10 MPa and a pressure of 1 min.

[0045] The ceramic green sheet is placed in the debinding furnace for debinding. The debinding process is set to three stages. The first stage is to heat up from room temperature to 200℃ at 5℃ / min and keep it warm for 1h; the second stage is to heat up from 200 to 380℃ at 3℃ / min and keep it warm for 5h; the third stage is to heat up from 380 to 600℃ at 5℃ / min and keep it warm for 1h, and finally cool to room temperature with the furnace.

[0046] After the debinding is completed, the ceramic sheet is sintered. The sintering process is as follows: the first stage is to heat from room temperature to 200°C at 5°C / min and keep warm for 0.5h; the second stage is to heat from 200 to 600°C at 5°C / min and keep warm for 0.5h; the third stage is to heat from 600 to 1350°C at 5°C / min and keep warm for 6h, and finally cool to room temperature with the furnace to obtain the sintered lithium lanthanum titanate solid ceramic electrolyte sheet as the sample of comparative example 1.

[0047] The sintered lanthanum titanate lithium ceramic sheet was subjected to a high-temperature quenching process in a tube furnace in an oxygen atmosphere at a treatment temperature of 1350°C, a heating rate of 10°C / min, and kept warm for 2 hours. It was then taken out immediately while hot and quenched in air to room temperature, with a cooling rate controlled at 150°C / min.

[0048] The surface of the lithium lanthanum titanate material prepared in the embodiment and the comparative example was polished and plated with a gold electrode by radio frequency sputtering for performance testing. The electrode coating thickness was 10 nm. The ionic impedance spectrum of the ceramic piece was tested and the ionic conductivity of the ceramic piece was calculated (the specific method is to use the ionic conductivity calculation formula: σ = d / (R * S), σ is the ionic conductivity, unit S / cm; d is the thickness of the ceramic piece, unit cm; R is the ionic impedance of the test, unit Ω; S is the area of ​​the effective electrode, unit cm). 2 ).

[0049] like Figure 1 As shown in the figure, the XRD diffraction patterns provided by Example 1 and Comparative Example 1 of the present invention show that a lanthanum titanate lithium ceramic sheet with a perovskite structure was synthesized by this method. After analysis, the diffraction peak intensity of the sample of Example 1 is significantly higher, indicating that the lanthanum titanate lithium ceramic sheet after quenching by the high-temperature quenching process has higher crystallinity and fewer unit cell defects; it can also be seen that Comparative Example 1 is significantly different from Example 1 between 20-30°, and there is a clear impurity phase, which further illustrates that the lanthanum titanate lithium solid electrolyte after quenching by the high-temperature quenching process has higher crystallinity and less impurity phase.

[0050] from Figure 2 It can be seen from the SEM image of the sample that, compared with Comparative Example 1, the grains of Example 1 have significantly grown larger, and the grain boundary pores and intracrystalline pores have been significantly reduced. Therefore, the density of the lanthanum titanate lithium solid electrolyte prepared in Example 1 using the inventive method is significantly improved.

[0051] Calculation method of relative density: First, the volume density of ceramics is measured using the displacement method. The basis of this method is Archimedes' principle, that is, the buoyancy of an object immersed in a liquid is equal to the weight of the displaced liquid.

[0052] The formula for calculating the volume density of the sample is:

[0053] Where M0 is the weight of the sample after it is fully dried, M1 is the weight of the sample in air after it is treated with boiling water, M2 is the weight of the sample in water after it is treated with boiling water, and ρ w is the density of water.

[0054] Relative density = sample volume density / sample theoretical density * 100%

[0055] Wherein, the theoretical density of the sample can be obtained by referring to the data.

[0056] from Figure 3 It can be seen from the EDS spectrum of the sample that, compared with Comparative Example 1, the lanthanum titanate lithium solid electrolyte prepared in Example 1 significantly reduces the segregation of titanium at the grain boundaries, thereby forming a ceramic solid solution with uniform distribution of elements, avoiding the blockage of ion channels at the grain boundaries and resulting in maximum grain boundary impedance.

[0057] Example 2

[0058] According to lithium lanthanum titanate (Li 0.15 La 0.62 The chemical formula of TiO3 is designed with Li2CO3, TiO2 and La2O3 as raw materials, anhydrous ethanol as solvent, a ball-to-material ratio of 5:1, and a powder-to-solvent mass ratio of 1:1.5. The mixture is ball-milled at a speed of 300 r / min for 24 hours, then dried in an 80°C oven for 24 hours, and pre-calcined in a high-temperature box furnace at 1100°C for 3 hours;

[0059] The powder was put into the ball mill again with a ball-to-material ratio of 3:1 and a powder-to-solvent mass ratio of 1:1.5. The ball milling was continued at 300 r / min for 24 hours, and then dried in an 80°C oven for 24 hours to obtain ultrafine and uniform lanthanum titanate lithium ceramic powder. A 5wt% PVB ethanol solution accounting for 15% of the powder mass was added for granulation, and the powder was sieved with an 80-mesh screen. The ceramic green sheet was pressed into a mold with a diameter of 12.7 mm at 10 MPa and a pressure of 1 minute.

[0060] The ceramic green sheets are placed in a debinding furnace for debinding. The debinding process is set to three stages. The first stage is to heat up from room temperature to 200°C at 5°C / min and keep warm for 1 hour; the second stage is to heat up from 200°C to 380°C at 3°C / min and keep warm for 5 hours; the third stage is to heat up from 380°C to 600°C at 5°C / min and keep warm for 1 hour, and finally cool to room temperature with the furnace.

[0061] After the debinding is completed, the ceramic sheet is sintered. The sintering process is as follows: the first stage is to heat up from room temperature to 200°C at 5°C / min and keep warm for 0.5h; the second stage is to heat up from 200°C to 600°C at 5°C / min and keep warm for 0.5h; the third stage is to heat up from 600°C to 1400°C at 5°C / min and keep warm for 5h, and finally cool to room temperature with the furnace to obtain the sintered lithium lanthanum titanate solid ceramic electrolyte sheet as the sample of comparative example 2.

[0062] The sintered lanthanum titanate lithium ceramic sheet was subjected to a high-temperature quenching process in a tubular furnace with a high oxygen content air atmosphere (oxygen content 50%). The treatment temperature was 1400°C, the heating rate was 15°C / min, and it was kept warm for 1 hour. Then, it was immediately taken out while hot and quenched in quenching oil to room temperature. The cooling rate was controlled at 200°C / min.

[0063] The surface of the lithium lanthanum titanate material prepared in Example 2 and Comparative Example 2 was polished and coated with gold electrodes by radio frequency sputtering for performance testing. The electrode coating thickness was 10 nm. The ionic impedance spectrum of the ceramic sheet was tested, and the ionic conductivity of the ceramic sheet was calculated.

[0064] Example 3

[0065] According to lithium lanthanum titanate (Li 0.3 La 0.57 The chemical formula of TiO3 is designed with Li2CO3, TiO2 and La2O3 as raw materials, anhydrous ethanol as solvent, a ball-to-material ratio of 4:1, and a powder-to-solvent mass ratio of 1:1.2. The mixture is ball-milled at a speed of 300 r / min for 24 hours, then dried in an oven at 100°C for 24 hours, and pre-calcined in a high-temperature box furnace at 1100°C for 3 hours;

[0066] The powder was put into the ball mill again with a ball-to-material ratio of 4:1 and a powder-to-solvent mass ratio of 1:1.2. The ball milling was continued at a speed of 300 r / min for 24 hours, and then dried in an oven at 100°C for 24 hours to obtain ultrafine and uniform lanthanum titanate lithium ceramic powder. A 5wt% PVB ethanol solution accounting for 5% of the powder mass was added for granulation, and the powder was sieved with a 200-mesh screen. The ceramic green sheet was pressed into a mold with a diameter of 12.7 mm at 10 MPa and a pressure of 1 minute.

[0067] The ceramic green sheet is placed in the debinding furnace for debinding. The debinding process is set to three stages. The first stage is to heat up from room temperature to 200℃ at 5℃ / min and keep it warm for 1h; the second stage is to heat up from 200℃ to 380℃ at 3℃ / min and keep it warm for 5h; the third stage is to heat up from 380℃ to 600℃ at 5℃ / min and keep it warm for 1h, and finally cool to room temperature with the furnace.

[0068] After the debinding is completed, the ceramic sheet is sintered. The sintering process is as follows: the first stage is to heat up from room temperature to 200°C at 5°C / min and keep warm for 0.5h; the second stage is to heat up from 200°C to 600°C at 5°C / min and keep warm for 0.5h; the third stage is to heat up from 600°C to 1300°C at 5°C / min and keep warm for 8h, and finally cool to room temperature with the furnace to obtain the sintered lithium lanthanum titanate solid ceramic electrolyte sheet as the sample of comparative example 3.

[0069] The sintered lanthanum titanate lithium ceramic sheet was subjected to a high-temperature quenching process in a tubular furnace with a high-oxygen air atmosphere (oxygen content 35%). The treatment temperature was 1300°C, the heating rate was 8°C / min, and the temperature was kept for 5 hours. Then, it was immediately taken out while hot and quenched in water to room temperature. The cooling rate was controlled at 250°C / min.

[0070] The surface of the lithium lanthanum titanate material prepared in Example 3 and Comparative Example 3 was polished and coated with gold electrodes by radio frequency sputtering for performance testing. The electrode coating thickness was 10 nm. The ionic impedance spectrum of the ceramic sheet was tested, and the ionic conductivity of the ceramic sheet was calculated.

[0071] Table 1 Ionic conductivity data of Examples and Comparative Examples

[0072] Ionic conductivity (S / cm) Relative density (%) Example 1 <![CDATA[7.84*10 -4 ]]> 99.1 Example 2 <![CDATA[1.31*10 -3 ]]> 99.5 Example 3 <![CDATA[5.21*10 -4 ]]> 99.2 Comparative Example 1 <![CDATA[3.58*10 -5 ]]> 98.3 Comparative Example 2 <![CDATA[4.25*10 -5 ]]> 98.1 Comparative Example 3 <![CDATA[7.18*10 -6 ]]> 97.9

[0073] In summary, the present invention can effectively reduce the grain boundary impedance of lanthanum titanate lithium ceramic solid electrolyte, making its total ionic conductivity reach 5.21*10 -4 ~1.31*10 -3 S / cm.

[0074] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a high ionic conductivity lithium lanthanum titanate solid electrolyte material, characterized in that The following steps are involved: (1) According to the chemical formula of lithium lanthanum titanate, the required lithium source, titanium source, lanthanum source and solvent are ball-milled and mixed, and then taken out and dried to obtain a lithium lanthanum titanate precursor mixture, and the precursor mixture is pre-fired to obtain a lithium lanthanum titanate ceramic material; (2) The lanthanum titanate lithium ceramic material pre-fired in step (1) is subjected to secondary ball milling and drying to obtain lanthanum titanate lithium ceramic powder, and then the powder is granulated and tableted, and then subjected to binder removal and sintering, and then cooled to room temperature in the furnace to obtain a lanthanum titanate lithium ceramic sheet solid electrolyte with a perovskite structure; (3) The lanthanum titanate lithium ceramic sheet obtained in step (2) is subjected to a high-temperature quenching process, and the cooling rate is controlled to be 100-300°C / min, thereby obtaining a lanthanum titanate lithium ceramic sheet solid electrolyte with high ionic conductivity.

2. The method for preparing the high ionic conductivity lithium lanthanum titanate solid electrolyte material according to claim 1, characterized in that: The chemical formula of lithium lanthanum titanate described in step (1) refers to Li 3x La 2 / 3-x TiO3 selects the corresponding amount of lithium source, titanium source and lanthanum source, that is, the amount of lithium source, titanium source and lanthanum source is such that the molar ratio of lithium element, titanium element and lanthanum element is 3x: 1: 2 / 3-x, wherein 0.04 <x<0.17; And / or, the lithium source in step (1) is at least one of lithium carbonate, lithium hydroxide, lithium sulfate, lithium oxalate, lithium acetate, lithium chloride, and lithium nitrate; The titanium source is at least one of titanium dioxide and tetrabutyl titanate; The lanthanum source is at least one of lanthanum oxide, lanthanum carbonate and lanthanum acetate.

3. The method for preparing the high ionic conductivity lithium lanthanum titanate solid electrolyte material according to claim 1, characterized in that: In the ball milling mixing described in step (1), the ball-to-material ratio is 3-5:1, and the material is ball milled on a ball mill at a speed of 200-600 r / min for 12-24 hours; and / or; In step (1), the pre-firing temperature is 900-1200°C and the pre-firing time is 1-10h; The rotation speed of the secondary ball milling in step (2) is 200-600 r / min, the ball milling time is 12-24 h, and the ball-to-material ratio is 3-5:

1.

4. The method for preparing a high ionic conductivity lithium lanthanum titanate solid electrolyte material according to claim 1, wherein: The binder added during the granulation process in step (2) is at least one of a PVB-ethanol solution and a PVA aqueous solution.

5. The method for preparing the high ionic conductivity lithium lanthanum titanate solid electrolyte material according to claim 4, characterized in that: The amount of the binder used is 5-15wt% of the powder.

6. The method for preparing a high ionic conductivity lithium lanthanum titanate solid electrolyte material according to claim 1, characterized in that: The debinding method described in step (2) is to heat the green ceramic sheet from room temperature to 100-300°C at 1-10°C / min and keep it warm for 1-2 hours; in the second stage, heat it to 380-450°C at 3-5°C / min and keep it warm for 4-6 hours; in the third stage, heat it to 500-700°C at 5-8°C / min and keep it warm for 1-2 hours, and finally cool it to room temperature with the furnace.

7. The method for preparing a high ionic conductivity lithium lanthanum titanate solid electrolyte material according to claim 1, characterized in that: The sintering described in step (2) adopts a three-stage heat treatment process, firstly, the temperature is raised from room temperature to 100-300°C at 1-10°C / min and kept at this temperature for 0.5-3h; then the temperature is raised to 400-600°C at 3-10°C / min and kept at this temperature for 0.5-3h; then the temperature is raised to 1200-1400°C at 4-10°C / min and kept at this temperature for 5-10h, so that the grains of the ceramic sheet are fully grown, and finally the ceramic sheet is cooled to room temperature with the furnace to obtain a lanthanum titanate lithium ceramic sheet solid electrolyte with a perovskite structure.

8. The method for preparing a high ionic conductivity lithium lanthanum titanate solid electrolyte material according to claim 1, characterized in that: In step (3), the high temperature quenching process is to heat the sintered ceramic sheet in a tube furnace at a rate of 8-15°C / min to a sintering temperature of 1200-1400°C, and keep the temperature for 1-5 hours, and then quench in air or a quenching agent, controlling the cooling rate to 100-300°C / min, thereby obtaining a lanthanum titanate lithium ceramic sheet solid electrolyte with high ionic conductivity.

9. The method for preparing a high ionic conductivity lithium lanthanum titanate solid electrolyte material according to claim 8, characterized in that: The atmosphere in the high temperature quenching process tube furnace is any one of oxygen and high oxygen content air atmosphere.

10. The method for preparing the high ionic conductivity lithium lanthanum titanate solid electrolyte material according to claim 9, characterized in that: The high oxygen content air atmosphere refers to air with an oxygen content greater than 30%.

11. A high ionic conductivity lithium lanthanum titanate solid electrolyte material prepared according to the method according to any one of claims 1 to 10.

12. Use of the high ionic conductivity lithium lanthanum titanate solid electrolyte material according to claim 11 in lithium ion solid-state batteries, electrochromic devices and ion-conducting sensor devices.

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