Anti-perovskite solid electrolyte and its preparation method, solid electrolyte sheet and all-solid-state lithium battery

Abstract

This invention relates to the field of lithium-ion battery technology, and discloses an anti-perovskite solid electrolyte and its preparation method, a solid electrolyte sheet, and an all-solid-state lithium battery. The method uses Li₂O and LiX as raw materials, which are pretreated and pressurized to obtain the anti-perovskite solid electrolyte. This invention also discloses the anti-perovskite solid electrolyte prepared by the method, a solid electrolyte sheet including the anti-perovskite solid electrolyte, and an all-solid-state battery including the solid electrolyte sheet. This invention uses Li₂O and LiX as raw materials, and sintering under pressure to achieve a purity of 61-72% for Li₇O₂X₃ (e.g., Li₇O₂Br₃) in the obtained anti-perovskite solid electrolyte, thereby improving the ionic conductivity of the anti-perovskite solid electrolyte.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to an anti-perovskite solid electrolyte and its preparation method, a solid electrolyte sheet, and an all-solid-state lithium battery. Background Technology

[0002] Currently, rechargeable lithium-ion batteries stand out among various energy storage batteries due to their stable charge-discharge characteristics and high energy density. However, the widespread application of electric vehicles and large-scale energy storage technologies urgently requires new lithium battery systems with high energy density, long cycle life, and high safety and reliability. Nevertheless, commercial lithium-ion batteries using liquid electrolytes still have significant drawbacks; for example, the flammability of organic liquid electrolytes can lead to serious safety issues. Replacing the organic liquid electrolytes used in traditional commercial lithium-ion batteries with solid-state electrolytes can greatly improve the safety of all-solid-state lithium batteries. Therefore, all-solid-state lithium batteries are considered a candidate for the most competitive next-generation energy storage technology. Furthermore, as the most critical component of all-solid-state lithium batteries, solid-state electrolytes typically require high lithium-ion conductivity.

[0003] Recently, the design concept of two-dimensional layered anti-perovskite structures has attracted the attention of researchers. The Ruddlesden-Poper (RP) phase Na4OI2, with octahedrons connected in an ab-plane, possesses the lowest activation energy barrier (0.3 eV), lower than the 0.34 eV of 3D cubic Na3OBr. Theoretical calculations revealed that basic interstitial atoms have a lower migration barrier than vacancies and play an important role in ion conduction in RP anti-perovskites (A4OX2, A = Li, Na; X = Cl, Br, I). Theoretical calculations indicate that layered Li4OBr2 has an activation energy as low as 0.29 eV. The paper "Enhanced Ionic Conductivity with Li7O2Br3 Phase in Li3OBr Anti-Perovskite Solid Electrolyte" (Zhu, J.; Li, S.; Zhang, Y.; Howard, JW; Lu, X.; Li, Y.; Wang, Y.; Kumar, RS; Wang, L.; Zhao, Y., APPLIED PHYSICS LETTERS 2016, 109, 61-65.) discloses the synthesis of Li3OBr anti-perovskite solid electrolyte mixed with Li7O2Br3 by ball milling.

[0004] Although the aforementioned existing techniques cannot obtain a pure Li7O2Br3 phase, they do have a higher conductivity (10 Ω·cm) compared to the Li3OBr ion alone. -6 S·cm -1Compared to other electrolytes, the anti-perovskite solid electrolyte mixed with Li7O2Br3 exhibits a higher ionic conductivity of 0.24 × 10⁻⁶. -4 S·cm -1 Currently, the pure phase of Li7O2Br3 anti-perovskite solid electrolyte has not been synthesized. In the paper "Enhanced Ionic Conductivity with Li7O2Br3 Phase in Li3OBr Anti-Perovskite Solid Electrolyte", a Li7O2Br3 / Li3OBr mixture with a mass percentage of 44% was obtained by ball milling at room temperature and atmospheric pressure using Li2O and LiBr as raw materials.

[0005] Therefore, there is an urgent need to develop a method to prepare anti-perovskite solid electrolytes with higher purity of Li7O2Br3. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem of low purity of Li7O2Br3 in the anti-perovskite solid electrolyte in the prior art, and to provide an anti-perovskite solid electrolyte, its preparation method, solid electrolyte sheet and all-solid-state lithium battery.

[0007] To achieve the above objectives, the first aspect of the present invention provides a method for preparing an anti-perovskite solid electrolyte, wherein the method uses Li2O and LiX as raw materials, and obtains the anti-perovskite solid electrolyte after pretreatment and pressure sintering.

[0008] Where X is F - Cl - ,Br - I - NO2 - NH2 - BH4 - and BF4 - One or more of them.

[0009] The second aspect of the present invention provides an anti-perovskite solid electrolyte prepared by the method described in the first aspect.

[0010] A third aspect of the present invention provides a solid electrolyte sheet comprising the anti-perovskite solid electrolyte described in the second aspect.

[0011] A fourth aspect of the present invention provides an all-solid-state battery comprising the solid electrolyte sheet described in the third aspect.

[0012] The beneficial technical effects achieved by the present invention through the above technical solution are as follows:

[0013] This invention uses Li2O and LiX as raw materials and performs sintering under pressure to achieve a purity of 61-72% for Li7O2X3 (e.g., Li7O2Br3) in the obtained anti-perovskite solid electrolyte, thereby improving the ionic conductivity of the anti-perovskite solid electrolyte. Attached Figure Description

[0014] Figure 1 This is the XRD pattern of the anti-perovskite solid electrolyte prepared in Example 1 of this invention. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] The first aspect of the present invention provides a method for preparing an anti-perovskite solid electrolyte, wherein the method uses Li2O and LiX as raw materials, and obtains the anti-perovskite solid electrolyte after pretreatment and pressure sintering;

[0017] Where X is F - Cl - ,Br - I - NO2 - NH2 - BH4 - and BF4 - One or more of them.

[0018] In the preparation process described in this invention, when X is Br, the main reactions that occur are as follows:

[0019] 2Li₂O + 3LiBr → Li₇O₂Br₃

[0020] Li₂O + LiBr → Li₃OBr.

[0021] This invention uses Li₂O and LiX as raw materials. The pretreated raw materials are sintered under pressure, unexpectedly increasing the purity of Li₇O₂X₃ (e.g., Li₇O₂Br₃) in the resulting anti-perovskite solid electrolyte; that is, increasing the mass percentage of Li₇O₂X₃ (e.g., Li₇O₂Br₃) in the anti-perovskite solid electrolyte. The anti-perovskite solid electrolyte prepared by this invention exhibits improved ionic conductivity.

[0022] In some embodiments of the present invention, the molar ratio of Li₂O to Li₃ is 1:0.5-5, for example 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, and any value within the range of any two of the above values, preferably 1:0.75-3. In the present invention, if this molar ratio is too large, there will be too much Li₂O; if this molar ratio is too small, there will be too much Li₃. Both excessively large and excessively small molar ratios are detrimental to the formation of high-purity Li₇O₂X₃.

[0023] In some preferred embodiments of the present invention, X is Br - .

[0024] In some embodiments of the present invention, the pretreatment includes ball milling and drying Li2O and LiX. In the present invention, ball milling enables Li2O and LiX to be mixed uniformly.

[0025] In some embodiments of the present invention, the ball milling speed is 150-500 rpm, for example, 150 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm, and any value within the range of any two of the above values, preferably 200-300 rpm. In the present invention, if the ball milling speed is too fast, the material will react to generate Li3OX impurities; if the ball milling speed is too slow, a longer mixing time is required.

[0026] In some preferred embodiments of the present invention, the ball milling time is 1-5 hours, preferably 1-2 hours. In the present invention, if the ball milling time is too short, the mixing is not uniform enough, and a longer mixing time is required; if the ball milling time is too long, a uniform mixture will be obtained, but too much unnecessary time will be consumed.

[0027] In some embodiments of the present invention, the drying temperature is 100-180°C, for example 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, and any value within the range of any two of the above values, preferably 120-160°C. In the present invention, if the drying temperature is too low, a longer drying time is required; if the drying temperature is too high, the raw materials may react.

[0028] In some preferred embodiments of the present invention, the drying time is 1-5 hours, preferably 1.5-2.5 hours. In the present invention, if the drying time is too short, the drying effect will not be achieved; if the drying time is too long, too much time will be consumed.

[0029] In some preferred embodiments of the invention, the drying is carried out under vacuum conditions. This is done to prevent moisture from entering.

[0030] In some preferred embodiments of the present invention, the vacuum degree of the vacuum condition is 10. -1 -10 -2 Pa.

[0031] In some embodiments of the present invention, the pressure of the pressure sintering is 4-10 GPa, for example, 4 GPa, 5 GPa, 6 GPa, 7 GPa, 8 GPa, 9 GPa, 10 GPa, or any value within the range of any two of the above values, preferably 5-8 GPa. In the present invention, if the pressure of the pressure sintering is too low, the yield of Li7O2Br3 will be too low; if the pressure of the pressure sintering is too high, the yield of Li7O2Br3 will also decrease, and the product will decompose.

[0032] In some preferred embodiments of the present invention, the pressure sintering temperature is 550-900℃, for example, 550℃, 600℃, 700℃, 800℃, 900℃, or any value within the range of any two of the above values, preferably 700-800℃. In the present invention, if the pressure sintering temperature is too low, the reaction will not be sufficient; if the pressure sintering temperature is too high, the product will decompose.

[0033] In some preferred embodiments of the present invention, the pressure sintering time is 1.5-5 hours, for example, 1.5 hours, 2 hours, 3 hours, 4 hours, 5 hours, or any value within the range of any two of the above values, preferably 2-3 hours. In the present invention, if the pressure sintering time is too short, the reaction will not be sufficient; if the pressure sintering time is too long, too much synthesis time will be consumed.

[0034] In some embodiments of the present invention, the method further includes: post-processing the pressure-sintered product to obtain an anti-perovskite solid electrolyte.

[0035] Those skilled in the art can choose post-processing methods, such as grinding, according to actual needs.

[0036] According to a particularly preferred embodiment of the present invention, a method for preparing an anti-perovskite solid electrolyte includes the following steps:

[0037] (1) Using Li₂O and LiBr in a molar ratio of 1:0.75-3 as raw materials, ball milling is performed at 200-300 rpm for 1-2 hours, followed by drying at 120-160℃ for 1.5-2.5 hours; the drying is carried out under a vacuum of 10 -1 -10 -2 The procedure was carried out under vacuum conditions of Pa;

[0038] (2) The dried product is subjected to pressure sintering at 700-800℃ and 5-8GPa for 2-3 hours;

[0039] (3) The product of pressure sintering is post-treated to obtain an anti-perovskite solid electrolyte.

[0040] The second aspect of the present invention provides an anti-perovskite solid electrolyte prepared by the method described in the first aspect.

[0041] A third aspect of the present invention provides a solid electrolyte sheet comprising the anti-perovskite solid electrolyte described in the second aspect.

[0042] In this invention, solid electrolyte sheets can be prepared using methods known in the art.

[0043] A fourth aspect of the present invention provides an all-solid-state battery comprising the solid electrolyte sheet described in the third aspect.

[0044] This invention uses Li2O and LiX as raw materials and performs sintering under pressure to achieve a purity of 61-72% for Li7O2Br3 in the obtained anti-perovskite solid electrolyte, thereby improving the ionic conductivity of the anti-perovskite solid electrolyte.

[0045] The present invention will be described in detail below through embodiments.

[0046] Unless otherwise specified in the following examples and comparative examples, all conditions were performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products.

[0047] Example 1

[0048] This embodiment illustrates the preparation of an anti-perovskite solid electrolyte.

[0049] (1) Using Li₂O (Alfa Aesar, 99.5%) and LiBr (Alfa-Aesar, anhydrous, 99%) as raw materials, weigh 0.05 mol of Li₂O and 0.075 mol of LiBr in a glove box. Place the raw materials into a 30 mL ball mill jar containing 60 g of zirconia balls and ball mill at 200 rpm for 1 h to mix them evenly. Then place the above mixed slurry into a vacuum drying oven (vacuum degree of 10). - 2 Pa), dried at 135℃ for 2 hours;

[0050] (2) The product obtained in step (1) is placed in the cavity of a six-sided press and sintered for 2 hours at a pressure of 8 GPa and a temperature of 700 °C. After cooling to room temperature, the pressure is released to obtain an anti-perovskite solid electrolyte including Li7O2Br3 and Li3OBr.

[0051] Example 2

[0052] This embodiment illustrates the preparation of an anti-perovskite solid electrolyte.

[0053] (1) Using Li₂O (Alfa Aesar, 99.5%) and LiBr (Alfa-Aesar, anhydrous, 99%) as raw materials, weigh 0.05 mol of Li₂O and 0.067 mol of LiBr in a glove box. Place the raw materials into a 30 mL ball mill jar containing 60 g of zirconia balls and ball mill at 250 rpm for 2 h to mix them evenly. Then place the above mixed slurry into a vacuum drying oven (vacuum degree of 10). - 2 Pa), dried at 120℃ for 2.5h;

[0054] (2) The product obtained in step (1) is placed in the cavity of a six-sided press and sintered for 2.5 h at a pressure of 5 GPa and a temperature of 800 °C. After cooling to room temperature, the pressure is released to obtain an anti-perovskite solid electrolyte including Li7O2Br3 and Li3OBr.

[0055] Example 3

[0056] This embodiment illustrates the preparation of an anti-perovskite solid electrolyte.

[0057] (1) Using Li₂O (Alfa Aesar, 99.5%) and LiBr (Alfa-Aesar, anhydrous, 99%) as raw materials, weigh 0.05 mol of Li₂O and 0.05 mol of LiBr in a glove box. Place the raw materials into a 30 mL ball mill jar containing 60 g of zirconia balls and ball mill at 300 rpm for 1.75 h to mix them evenly. Then place the above mixed slurry into a vacuum drying oven (vacuum degree of 10). - 2 Pa), dried at 160℃ for 1.5h;

[0058] (2) The product obtained in step (1) is placed in the cavity of a six-sided press and sintered for 3 hours at a pressure of 6 GPa and a temperature of 750 °C. After cooling to room temperature, the pressure is released to obtain an anti-perovskite solid electrolyte including Li7O2Br3 and Li3OBr.

[0059] Example 4

[0060] This embodiment illustrates the preparation of an anti-perovskite solid electrolyte.

[0061] (1) Using Li₂O (Alfa Aesar, 99.5%) and LiBr (Alfa-Aesar, anhydrous, 99%) as raw materials, weigh 0.05 mol of Li₂O and 0.025 mol of LiBr in a glove box. Place the raw materials into a 30 mL ball mill jar containing 60 g of zirconia balls and ball mill at 150 rpm for 5 h to mix them evenly. Then place the above mixed slurry into a vacuum drying oven (vacuum degree of 10). - 2 Pa), dried at 100℃ for 1 hour;

[0062] (2) The product obtained in step (1) is placed in the cavity of a six-sided press and sintered for 1.5 h at a pressure of 4 GPa and a temperature of 900 °C. After cooling to room temperature, the pressure is released to obtain an anti-perovskite solid electrolyte including Li7O2Br3 and Li3OBr.

[0063] Example 5

[0064] This embodiment illustrates the preparation of an anti-perovskite solid electrolyte.

[0065] (1) Using Li₂O (Alfa Aesar, 99.5%) and LiBr (Alfa-Aesar, anhydrous, 99%) as raw materials, weigh 0.05 mol of Li₂O and 0.25 mol of LiBr in a glove box. Place the raw materials into a 30 mL ball mill jar containing 60 g of zirconia balls and ball mill at 500 rpm for 1 h to mix them evenly. Then place the above mixed slurry into a vacuum drying oven (vacuum degree of 10). -2 Pa), dried at 180℃ for 5 hours;

[0066] (2) The product obtained in step (1) is placed in the cavity of a six-sided press and sintered for 5 hours at a pressure of 10 GPa and a temperature of 550 °C. After cooling to room temperature, the pressure is released to obtain an anti-perovskite solid electrolyte including Li7O2Br3 and Li3OBr.

[0067] Comparative Example 1

[0068] An anti-perovskite solid electrolyte was prepared according to the method in Example 5, except that the product obtained in step (1) was placed in a sintering furnace and sintered at atmospheric pressure and 480°C for 15 h. The sintered product was then ball-milled at 300 rpm for 1.5 h. The sintering and ball-milling process was repeated three times to obtain an anti-perovskite solid electrolyte comprising Li7O2Br3 and Li3OBr.

[0069] Test Example 1

[0070] The purity of Li7O2Br3 in the anti-perovskite solid electrolytes prepared in Examples 1-5 and Comparative Example 1 was analyzed by XRD, and the results are shown in Table 1. The XRD pattern of the anti-perovskite solid electrolyte in Example 1 is shown below. Figure 1 .

[0071] Test Example 2

[0072] The anti-perovskite solid electrolytes prepared in Examples 1-5 and Comparative Example 1 were fabricated into solid electrolyte sheets, and their ionic conductivity was tested. The results are shown in Table 1.

[0073] The method for preparing solid electrolyte tablets is as follows: Take a certain mass of electrolyte powder, grind it thoroughly, spread it evenly in the mold of a tablet press, press it into tablets with a pressure of 300 MPa, hold the pressure for 5 minutes, and then take it out. The tableting is completed, and solid electrolyte tablets are obtained.

[0074] The method for testing ionic conductivity is as follows: A solid electrolyte sheet is polished smooth, and then double-sided gold sputtering is used to prepare a blocking electrode. Electrochemical impedance spectroscopy (EIS) is used to test the impedance diagram of the solid electrolyte on an electrochemical workstation. The frequency range is 1MHz-0.1Hz, and the amplitude is 10mV. Impedance testing is performed at room temperature. Finally, Zview software is used to analyze and fit the obtained impedance diagram to obtain the ionic conductivity.

[0075] Table 1

[0076] serial number <![CDATA[Purity of Li7O2Br3, %]]> <![CDATA[Ionic conductivity, S·cm -1 > Example 1 72 <![CDATA[0.77×10 -4 ]]> Example 2 70 <![CDATA[0.70×10 -4 ]]> Example 3 69 <![CDATA[0.68×10 -4 ]]> Example 4 64 <![CDATA[0.59×10 -4 ]]> Example 5 61 <![CDATA[0.57×10 -4 ]]> Comparative Example 1 43 <![CDATA[0.24×10 -4 ]]>

[0077] As can be seen from the results in Table 1, compared with Comparative Example 1, Examples 1-5 using the method of the present invention, with Li2O and LiBr as raw materials and sintered under pressure, can obtain anti-perovskite solid electrolytes with a purity of 61-72% for Li7O2Br3, thereby improving the ionic conductivity of the anti-perovskite solid electrolyte.

[0078] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing an anti-perovskite solid state electrolyte, characterized by, The method uses Li2O and LiX as raw materials, and obtains the anti-perovskite solid-state electrolyte Li7O2X3 after pretreatment and pressure sintering; wherein X is one or more of F - , Cl - , Br - , I - , NO2 - , NH2 - , BH4 - , and BF4 - . The pressure of the pressure sintering is 5-8 GPa; The temperature of the pressure sintering is 700-800℃; The time of the pressure sintering is 2-3 h.

2. The method of claim 1, wherein, The molar ratio of Li2O and LiX is 1:0.5-5; and / or X is Br - .

3. The method of claim 2, wherein, The molar ratio of Li2O and LiX is 1:0.75-3; and / or X is Br - .

4. The method of claim 1, wherein, The pretreatment comprises ball milling and drying of Li2O and LiX.

5. The method of claim 4, wherein, The speed of the ball milling is 150-500 rpm; And / or, the time of the ball milling is 1-5 h.

6. The method of claim 5, wherein, The speed of the ball milling is 200-300 rpm; And / or, the time of the ball milling is 1-2 h.

7. The method of claim 4, wherein, The temperature of the drying is 100-180℃; And / or, the time of the drying is 1-5 h.

8. The method of claim 7, wherein, The temperature of the drying is 120-160℃; And / or, the time of the drying is 1.5-2.5 h.

9. The method of claim 4, wherein, The drying is performed under vacuum condition; and / or the vacuum degree of the vacuum condition is 10 -1 -10 -2 Pa.

10. The method of any of claims 1-9, wherein, The method further comprises post-treatment of the product of the pressure sintering to obtain the anti-perovskite solid-state electrolyte.

11. An anti-perovskite solid-state electrolyte prepared by the method of any one of claims 1-10.

12. A solid-state electrolyte sheet comprising the anti-perovskite solid-state electrolyte of claim 11.

13. An all-solid-state battery comprising the solid-state electrolyte sheet of claim 12.

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