Composite material, solid electrolyte and preparation method, lithium metal battery

Abstract

This application discloses a composite material for preparing a solid electrolyte, the solid electrolyte and its preparation method, and a lithium metal battery, belonging to the field of lithium-ion battery technology. The composite material comprises a garnet-type solid electrolyte and a zeolite imidazole ester framework, with a mass ratio of solid electrolyte:zeolite imidazole ester framework = 100:(0.01-6); wherein the chemical formula of the solid electrolyte is Li. 7‑ x La3Zr 2‑x Ta x O 12 , 0≤x≤1. In this application, by adding a certain amount of zeolite imidazole ester skeleton to the solid electrolyte, a solid electrolyte with low densification temperature, high ionic conductivity and high mechanical strength can be prepared from the composite material of this application.

Description

Technical Field

[0001] This application relates to the field of lithium-ion batteries, and more particularly to a composite material for preparing a solid electrolyte, a solid electrolyte and its preparation method, and a lithium metal battery. Background Technology

[0002] Currently, lithium-ion batteries have become one of the most important energy storage devices in people's daily lives due to their advantages such as long cycle life and high energy density. In recent years, with the rapid development of electric vehicles, higher requirements have been placed on the energy density and safety performance of batteries. All-solid-state lithium metal batteries replace the flammable liquid electrolyte with a solid electrolyte and use lithium metal with a higher theoretical specific capacity as the negative electrode, which has advantages such as high safety and high energy density. Therefore, the research on all-solid-state lithium metal batteries is of great significance.

[0003] Solid electrolytes are the core components of all-solid-state lithium metal batteries. They need to be prepared at low temperatures and have high density, high ionic conductivity and high mechanical strength. They also need to ensure that lithium ions can migrate rapidly between the positive and negative electrodes while suppressing lithium dendrites and maintaining long-term stable cycling of the battery.

[0004] Therefore, there is an urgent need in the field to provide a solid electrolyte that can be prepared at a low temperature and has high density, high ionic conductivity and high mechanical strength. Summary of the Invention

[0005] In view of this, this application provides a composite material for preparing solid electrolytes, which can be densified at a lower temperature, and the resulting solid electrolyte has high density, high ionic conductivity and high mechanical strength.

[0006] In a first aspect, embodiments of this application provide a composite material for preparing a solid electrolyte, the composite material comprising a garnet-type solid electrolyte and a zeolite imidazole ester skeleton, wherein, by mass percentage, the solid electrolyte: zeolite imidazole ester skeleton = 100:(0.01-6);

[0007] The chemical formula of the solid electrolyte is Li. 7-x La3Zr 2-x Ta x O 12 , 0≤x≤1.

[0008] In some embodiments of this application, the solid electrolyte: zeolite imidazole ester skeleton = 100:(1-5).

[0009] In some embodiments of this application, the solid electrolyte: zeolite imidazole ester skeleton = 100:(2-4).

[0010] In some embodiments of this application, the zeolite imidazole ester skeleton includes at least one of zeolite imidazole ester skeleton 8 and zeolite imidazole ester skeleton 67.

[0011] In some embodiments of this application, the particle size of the zeolite imidazole ester skeleton is 100 nm to 300 nm.

[0012] In some embodiments of this application, 0.2 ≤ x ≤ 0.8.

[0013] A second aspect of this application provides a method for preparing a solid electrolyte, the method comprising:

[0014] Obtain a solid electrolyte precursor; wherein the solid electrolyte precursor comprises a solid electrolyte and a zeolite imidazole ester framework, and the chemical formula of the solid electrolyte is Li. 7-x La3Zr 2-x Ta x O 12 , 0≤x≤1, calculated by mass percentage, the solid electrolyte: zeolite imidazole ester skeleton = 100:(0.01-6);

[0015] The solid electrolyte precursor is sintered at high temperature to obtain a solid electrolyte.

[0016] In some embodiments of this application, the sintering temperature is 900°C to 1300°C; and / or

[0017] The high-temperature sintering includes high-temperature sintering under an inert atmosphere; and / or

[0018] The heating rate during the high-temperature sintering process is from 5°C / min to 20°C / min.

[0019] In some embodiments of this application, the sintering temperature is 1000°C to 1100°C; and / or

[0020] The steps for obtaining the solid electrolyte precursor include:

[0021] The first mixture is obtained by mixing solid electrolyte powder and zeolite imidazole ester skeleton according to a preset ratio;

[0022] A certain pressure is applied to the first mixture to obtain a solid electrolyte precursor.

[0023] A third aspect of this application provides a solid electrolyte, which includes the aforementioned composite material or is prepared by the aforementioned preparation method.

[0024] In some embodiments of this application, the density of the solid electrolyte is 94% to 99%;

[0025] The ionic conductivity of the solid electrolyte is from 0.7 mS / cm to 1.3 mS / cm;

[0026] The elastic modulus of the solid electrolyte is 84 GPa to 175 GPa;

[0027] The hardness of the solid electrolyte is 7 GPa to 13 GPa.

[0028] A fourth aspect of this application provides a lithium metal battery, the lithium metal battery including the solid electrolyte, the solid electrolyte being disposed between the positive electrode and the negative electrode.

[0029] Beneficial effects:

[0030] In this application, by adding a certain amount of zeolite imidazole ester skeleton to the composite material for preparing solid electrolyte, a solid electrolyte with low densification temperature, high density, high ionic conductivity and high mechanical strength can be prepared from the composite material of this application. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A schematic diagram of the parameters during the nanoindentation process.

[0033] Figure 2 Load-depth curve of nanoindentation test.

[0034] Figure 3 This is the diffraction pattern of ZIF-8 prepared in the embodiments of this application.

[0035] Figure 4 This is a cycle test diagram of the battery prepared by Example 1 of this application.

[0036] Figure 5 This is a cycle test diagram of the battery prepared using Comparative Example 1 in this application.

[0037] Figure 6 This is a process flow diagram of the preparation of the solid electrolyte in this application. Detailed Implementation

[0038] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0040] In this application, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or operating state, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative purposes and do not impose numerical requirements or establish a numerical order.

[0041] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0042] In this application, "at least one" means one or more, and "more than one" means two or more. "One or more", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0043] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0044] Currently, lithium-ion batteries have become one of the most important energy storage devices in people's daily lives due to their advantages such as long cycle life and high energy density. In recent years, with the rapid development of electric vehicles, higher requirements have been placed on the energy density and safety performance of batteries. All-solid-state lithium metal batteries replace the flammable liquid electrolyte with a solid electrolyte and use lithium metal with a higher theoretical specific capacity as the negative electrode, which has advantages such as high safety and high energy density. Therefore, the research on all-solid-state lithium metal batteries is of great significance.

[0045] Solid electrolytes are the core components of all-solid-state lithium metal batteries. They need to be prepared at low temperatures, have high ionic conductivity and high mechanical strength, and suppress lithium dendrites while ensuring that lithium ions can migrate rapidly between the positive and negative electrodes, thus maintaining the long-term stable cycling of the battery.

[0046] Currently, common solid electrolytes include oxide solid electrolytes, sulfide solid electrolytes, composite solid electrolytes, and the emerging halide solid electrolytes. Oxide solid electrolytes, as materials with high ionic conductivity, stable structure, simple synthesis process, and non-toxicity and pollution-free properties, are widely studied. Among the many solid electrolytes, garnet-type Li7La3Zr2O... 12 LLZO has attracted much attention due to its high electrical conductivity and good electrochemical stability. However, LLZO also suffers from problems such as unsatisfactory ionic conductivity, low mechanical strength, and a relatively high densification temperature.

[0047] In view of this, the first aspect of the present application provides a composite material for preparing a solid electrolyte, which has the advantages of low densification temperature, high ionic conductivity and high mechanical strength.

[0048] Specifically, the composite material provided in this application includes a garnet-type solid electrolyte and a zeolite imidazole ester skeleton, with a mass ratio of solid electrolyte to zeolite imidazole ester skeleton of 100:(0.01-6) (i.e., any value between 0.01 and 6), wherein the chemical formula of the solid electrolyte is Li.7-x La3Zr 2-x Ta x O 12 , 0≤x≤1.

[0049] In this application, by adding a certain amount of zeolite imidazole ester skeleton to the composite material for preparing solid electrolyte, a solid electrolyte with low densification temperature, high ionic conductivity and high mechanical strength can be prepared from the composite material of this application.

[0050] For example, by mass percentage, the zeolite imidazole ester skeleton: solid electrolyte is approximately 0.01%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, and any value between the two aforementioned points.

[0051] For example, x takes approximately 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, and any value between the two aforementioned points. It should be noted that in this application, "approximately" means a value differing from the stated number by ±10%. Taking the stated number as 1 as an example, approximately 1 corresponds to any value between 0.9 and 1.1.

[0052] In some embodiments of this application, the solid electrolyte: zeolite imidazole ester skeleton ratio is 100:(1-5) by mass percentage. Further, the solid electrolyte: zeolite imidazole ester skeleton ratio is 100:(1-3), and even further, it is 100:(1.5-2.5). Controlling the zeolite imidazole ester skeleton ratio within this range in these embodiments further reduces the densification temperature and improves the ionic conductivity and mechanical strength of the solid electrolyte.

[0053] In some embodiments of this application, X is greater than 0. That is, the solid electrolyte is LLZTO formed by doping LLZO with Ta. In this embodiment, Ta doping is beneficial to further improve the ionic conductivity of the solid electrolyte.

[0054] It should be noted that although LLZTO exhibits significantly improved lithium-ion conductivity compared to LLZO, its lithium-ion conductivity is still not ideal, and LLZTO also suffers from low density and high densification temperature. In this embodiment, by compounding LLZTO with a zeolite imidazole ester framework, the density of LLZTO can be improved, its densification temperature (referring to the heat treatment temperature at which densification is completed) can be reduced, and the ionic conductivity and mechanical strength of the solid electrolyte can be increased.

[0055] In some embodiments of this application, 0.1 ≤ x ≤ 0.9. Further, 0.4 ≤ x ≤ 0.8. Even further, 0.5 ≤ x ≤ 0.7. In this embodiment, controlling the Ta doping content is beneficial for further improving the ionic conductivity and mechanical strength of the solid electrolyte.

[0056] In some embodiments of this application, the zeolite imidazole ester skeleton includes at least one of zeolite imidazole ester skeleton 8 (i.e., ZIF-8) and zeolite imidazole ester skeleton 67 (ZIF-67).

[0057] A second aspect of this application provides a method for preparing a solid electrolyte, the method comprising the following steps:

[0058] S10 yields a solid electrolyte precursor; wherein the solid electrolyte precursor comprises a solid electrolyte and a zeolite imidazole ester framework, and the chemical formula of the solid electrolyte is Li 7-x La3Zr 2-x Ta x O 12 , 0≤x≤1, calculated by mass percentage, the solid electrolyte: zeolite imidazole ester skeleton = 100:(0.01-6).

[0059] The solid electrolyte precursor is obtained by high-temperature sintering of S20.

[0060] In this application, by adding a certain amount of zeolite imidazole ester skeleton to the solid electrolyte, a solid electrolyte with low densification temperature, high ionic conductivity and high mechanical strength can be prepared from the composite material of this application.

[0061] For example, by mass percentage, the zeolite imidazole ester skeleton: solid electrolyte is approximately 0.01%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, and any value between the two aforementioned points.

[0062] For example, x takes approximately 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, and any value between the two aforementioned points. It should be noted that in this application, "approximately" means a value differing from the stated number by ±10%. Taking the stated number as 1 as an example, approximately 1 corresponds to any value between 0.9 and 1.1.

[0063] In some embodiments of this application, the solid electrolyte: zeolite imidazole ester skeleton ratio is 100:(1-5) by mass percentage. Further, the solid electrolyte: zeolite imidazole ester skeleton ratio is 100:(1-3), and even further, it is 100:(1.5-2.5). Controlling the zeolite imidazole ester skeleton ratio within this range in these embodiments further reduces the densification temperature and improves the ionic conductivity and mechanical strength of the solid electrolyte.

[0064] In some embodiments of this application, X is greater than 0. That is, the solid electrolyte is LLZTO formed by reacting LLZO with Ta. In this embodiment, Ta doping is beneficial to further improve the ionic conductivity of the solid electrolyte.

[0065] It should be noted that although LLZTO exhibits significantly improved lithium-ion conductivity compared to LLZO, its lithium-ion conductivity is still not ideal, and LLZTO also suffers from low density and high densification temperature. In this embodiment, by compounding LLZTO with a zeolite imidazole ester framework, the density of LLZTO can be improved, its densification temperature (referring to the heat treatment temperature at which densification is completed) can be reduced, and the ionic conductivity and mechanical strength of the solid electrolyte can be increased.

[0066] In some embodiments of this application, 0.1 ≤ x ≤ 0.9. Further, 0.4 ≤ x ≤ 0.8. Even further, 0.5 ≤ x ≤ 0.7. In this embodiment, controlling the Ta doping content is beneficial for further improving the ionic conductivity and mechanical strength of the solid electrolyte.

[0067] In some embodiments of this application, the sintering temperature is between 900°C and 1300°C. Exemplarily, the sintering temperature is approximately 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, and any value between the two aforementioned values.

[0068] Furthermore, the sintering temperature is between 1000°C and 1100°C. Within this sintering temperature range, the electrolyte in this application can be densified, which is beneficial for reducing costs.

[0069] In some embodiments of this application, the high-temperature sintering includes high-temperature sintering under an inert atmosphere. Exemplarily, the inert atmosphere includes argon. Of course, in other embodiments of this application, the inert atmosphere may also include other inert gases, and this is not limited thereto.

[0070] In some embodiments of this application, the heating rate during the high-temperature sintering process is from 5°C / min to 20°C / min. Exemplarily, the heating rate is approximately 5°C / min, 10°C / min, 15°C / min, 20°C / min, or any value between the two aforementioned values.

[0071] In some embodiments of this application, the step of obtaining the solid electrolyte precursor includes: mixing a solid electrolyte and a zeolite imidazole ester skeleton in a preset ratio to obtain a first mixture; and applying a certain pressure to the first mixture to obtain the solid electrolyte precursor.

[0072] It should be noted that the solid electrolyte and zeolite imidazole ester skeleton in the embodiments of this application can be prepared by ourselves or obtained from the market, and there is no limitation here.

[0073] In some embodiments of this application, the zeolite imidazole ester skeleton includes at least one of zeolite imidazole ester skeleton 8 and zeolite imidazole ester skeleton 67.

[0074] For example, the process of preparing ZIF-8 includes: dissolving 1.835 g of zinc nitrate hexahydrate in 125 ml of methanol under stirring at room temperature (e.g., mechanical stirring or magnetic stirring) to prepare solution A. Then, dissolving 4.058 g of dimethylimidazole in 125 ml of methanol and stirring to prepare solution B. Solution A is then slowly added to solution B, and the solution turns into a milky white liquid. The beaker is sealed with sealing film and stirred for 20 h, then centrifuged (7000 rpm, 10 min) to obtain a solid. The solid obtained by centrifugation is washed three times with methanol, then dried in a vacuum drying oven for 12 h. Finally, the dried solid (ZIF-8) is ground for later use.

[0075] For example, the preparation of solid electrolytes includes (using Li) 6.4 La3Zr 1.4 Ta 0.6 O 12For example: LiOH·H2O, La2O3, ZrO2, and Ta2O5 were weighed according to a stoichiometric ratio of 7.0:1.5:1.4:0.6 (the lithium source content needs to be added in excess of 10% compared to the theoretical content). The prepared raw materials were thoroughly mixed and placed in a ball mill jar, and an appropriate amount of isopropanol was added. The mixture was ball-milled at 300 rpm for 12 hours to obtain the first mixture after ball milling. The first mixture was dried to obtain a dry second mixture. This second mixture was then placed in a tube furnace for high-temperature sintering at 900℃ for 12 hours at a heating rate of 10℃ / min. After the reaction, the sample was placed in the tube furnace and allowed to cool naturally before removing the product. The product was placed in a zirconia ball mill jar, and an appropriate amount of ethanol was added. The mixture was ball-milled at 300 rpm for 12 hours to refine the powder. After drying, the powder was sieved to obtain LLZTO (Li2O3) with a size of approximately 500 nm. 6.4 La3Zr 1.4 Ta 0.6 O 12 )powder.

[0076] For example, the preparation of the solid electrolyte includes: mixing the prepared solid electrolyte powder with a zeolite imidazole ester skeleton according to a preset ratio to obtain a composite material; then placing the composite material into a mold for uniaxial pressing to obtain a solid electrolyte precursor (i.e., a solid electrolyte ceramic sheet). The obtained solid electrolyte precursor is sintered at high temperature under argon atmosphere and heat-treated in an argon atmosphere at 1100°C for 12 hours at a heating rate of 10°C / min; after the heat treatment, the sample is placed in a tube furnace for natural cooling to obtain a test sample (i.e., a solid electrolyte).

[0077] In some embodiments of this application, the density of the solid electrolyte is 94% to 99%; the ionic conductivity of the solid electrolyte is 0.7 mS / cm to 1.3 mS / cm; the elastic modulus of the solid electrolyte is 84 GPa to 175 GPa; and the Vickers hardness of the solid electrolyte is 7 GPa to 13 GPa.

[0078] A fourth aspect of this application provides a lithium metal battery, which includes the aforementioned solid electrolyte. It is understood that, since the lithium metal battery of this application includes the aforementioned solid electrolyte, it also possesses the beneficial effects of the aforementioned solid electrolyte and has a better cycle life.

[0079] Specifically, a lithium metal battery includes a positive electrode, a negative electrode, and a solid electrolyte disposed between the positive and negative electrodes. For example, the negative electrode includes lithium metal or a lithium alloy.

[0080] The electrolyte and lithium-ion electronics in this application will be further described below with reference to specific embodiments.

[0081] Electrolyte Example 1

[0082] ZIF-8 Preparation: A solution A was prepared by dissolving 1.835 g of zinc nitrate hexahydrate in 125 ml of methanol using a room-temperature mechanical stirring method. Solution B was prepared by dissolving 4.058 g of dimethylimidazole in 125 ml of methanol. Solution A was slowly added to solution B, resulting in a milky white liquid. The beaker was sealed with a sealing film and stirred for 20 hours. The solution was then centrifuged (7000 rpm, 10 min) and washed three times with methanol. It was then dried in a vacuum drying oven for 12 hours. Finally, the dried ZIF-8 solid was ground for later use. The ZIF-8 particle size was approximately 200 nm. Its diffraction pattern is shown below. Figure 3 As shown. By Figure 3 It can be seen that the characteristic peaks on the diffraction pattern of the prepared product match the characteristic peaks of the standard ZIF-8 pattern, indicating that ZIF-8 was successfully prepared.

[0083] Preparation of solid electrolyte (LLZTO): LiOH·H2O, La2O3, ZrO2, and Ta2O5 were weighed according to a stoichiometric ratio of 7.0:1.5:1.4:0.6 to prepare Li 6.4 La3Zr 1.4 Ta 0.6 O 12 The lithium source content needs to be added in excess of 10% compared to the theoretical content. After thoroughly mixing the prepared raw materials, place them in a ball mill jar, add an appropriate amount of isopropanol, and ball mill at 300 rpm for 12 hours. After drying, place the mixed sample in a tube furnace for high-temperature sintering at 900℃ for 12 hours at a heating rate of 10℃ / min. After the reaction, place the sample in the tube furnace to cool naturally and remove the product. Place the product in a zirconia ball mill jar, add an appropriate amount of ethanol, and ball mill at 300 rpm for 12 hours to refine the powder. After drying, the powder is screened to obtain LLZTO (Li) with a size of approximately 500 nm. 6.4 La3Zr 1.4 Ta 0.6 O 12 )powder.

[0084] Preparation of solid electrolyte: The prepared LLZTO powder was mixed with ZIF-8 at a mass ratio of 100:2, and the mixture was placed in a mold for uniaxial pressing. The resulting solid electrolyte ceramic sheet was sintered at high temperature under argon atmosphere and then heat-treated at 1100℃ in an argon atmosphere for 12 hours with a heating rate of 10℃ / min. After the heat treatment, the sample was placed in a tube furnace for natural cooling to obtain the test sample.

[0085] Electrolyte Example 2

[0086] The difference between this example and Example 1 is that the heat treatment temperature during the preparation of the solid electrolyte is 1050°C.

[0087] Electrolyte Example 3

[0088] The difference between this example and Example 1 is that the heat treatment temperature during the preparation of the solid electrolyte is 1150°C.

[0089] Electrolyte Example 4

[0090] The difference between this example and Example 1 is that the heat treatment temperature during the preparation of the solid electrolyte is 1200°C.

[0091] Electrolyte Example 5

[0092] The difference between this example and Example 1 is that the heat treatment temperature during the preparation of the solid electrolyte is 1250°C.

[0093] Electrolyte Example 6

[0094] The difference between this example and Example 1 is that the heat treatment temperature during the preparation of the solid electrolyte is 1300°C.

[0095] Electrolyte Example 7

[0096] The difference between this and Example 1 is that LLZTO powder and ZIF-8 are mixed at a mass ratio of 100:1.

[0097] Electrolyte Example 8

[0098] The difference between this and Example 1 is that LLZTO powder and ZIF-8 are mixed at a mass ratio of 100:3.

[0099] Electrolyte Example 9

[0100] The difference between this and Example 1 is that LLZTO powder and ZIF-8 are mixed at a mass ratio of 100:4.

[0101] Electrolyte Example 10

[0102] The difference between this and Example 1 is that LLZTO powder and ZIF-8 are mixed at a mass ratio of 100:5.

[0103] Electrolyte Example 11

[0104] The difference between this example and Example 1 is that the solid electrolyte prepared is Li. 6.8 La3Zr 1.8 Ta 0.2 O 12 .

[0105] Electrolyte Example 12

[0106] The difference between this example and Example 1 is that the solid electrolyte prepared is Li. 6.6 La3Zr 1.6 Ta 0.4 O 12 .

[0107] Electrolyte Example 13

[0108] The difference between this example and Example 1 is that the solid electrolyte prepared is Li. 6.2 La3Zr 1.2 Ta 0.8 O 12 .

[0109] Electrolyte Example 14

[0110] The difference between this and Example 1 is that the solid electrolyte prepared is Li6La3ZrTaO. 12 .

[0111] Electrolyte Example 15

[0112] The difference between this and Example 1 is that the solid electrolyte prepared is LLZO (Li7La3Zr2O). 12 ).

[0113] Electrolyte Example 16

[0114] The difference between this and Example 1 is that LLZTO powder and ZIF-67 are mixed at a mass ratio of 100:2.

[0115] Electrolyte Comparative Example 1

[0116] Preparation of solid electrolyte (LLZTO): LiOH·H2O, La2O3, ZrO2, and Ta2O5 were weighed according to a stoichiometric ratio of 7.0:1.5:1.4:0.6 to prepare Li 6.4 La3Zr 1.4 Ta 0.6 O 12The lithium source content needs to be added in excess of 10% compared to the theoretical content. After thoroughly mixing the prepared raw materials, place them in a ball mill jar, add an appropriate amount of isopropanol, and ball mill at 300 rpm for 12 hours. After drying, place the mixed sample in a tube furnace for high-temperature sintering at 900℃ for 12 hours at a heating rate of 10℃ / min. After the reaction, place the sample in the tube furnace to cool naturally and remove the product. Place the product in a zirconia ball mill jar, add an appropriate amount of ethanol, and ball mill at 300 rpm for 12 hours to refine the powder. After drying, the powder is screened to obtain LLZTO (Li) with a size of approximately 500 nm. 6.4 La3Zr 1.4 Ta 0.6 O 12 )powder.

[0117] Preparation of solid electrolyte: The prepared LLZTO powder was placed into a mold for uniaxial pressing. The resulting solid electrolyte ceramic sheet was sintered at high temperature under argon atmosphere and heat-treated in an argon atmosphere at 1100℃ for 12 hours with a heating rate of 10℃ / min. After heat treatment, the sample was placed in a tube furnace for natural cooling to obtain the test sample.

[0118] The difference between this and Example 1 is that ZIF-8 was not added to the solid electrolyte.

[0119] Electrolyte Comparative Example 2

[0120] The difference between this example and Example 2 is that ZIF-8 was not added to the solid electrolyte.

[0121] Electrolyte Comparative Example 3

[0122] The difference between this and Example 3 is that ZIF-8 was not added to the solid electrolyte.

[0123] Electrolyte Comparative Example 4

[0124] The difference between this and Example 4 is that ZIF-8 was not added to the solid electrolyte.

[0125] Electrolyte Comparative Example 5

[0126] The difference between this and Example 5 is that ZIF-8 was not added to the solid electrolyte.

[0127] Electrolyte Comparative Example 6

[0128] The difference between this and Example 6 is that ZIF-8 was not added to the solid electrolyte.

[0129] Electrolyte Comparative Example 7

[0130] The difference between this example and Example 15 is that ZIF-8 was not added to the solid electrolyte.

[0131] Experimental Test

[0132] Density test:

[0133] Density = Actual density / Theoretical density. The theoretical density of LLZTO is 5.5 g / cm³. 3 The actual density is measured using Archimedes' displacement method. The buoyant force on an object submerged in a liquid can be calculated from the difference between its actual weight m1 and apparent weight m2 ("apparent weight" refers to the weight of the object when submerged in the liquid). Then, the volume of the object can be calculated using Archimedes' principle: V = (m1 - m2) / (ρg). Therefore, the density of the object is: ρobject = m1 * ρliquid / (m1 - m2).

[0134] Ionic conductivity test:

[0135] The sintered solid electrolyte ceramic sheet was polished and cleaned, then immersed in glacial acetic acid for 30 seconds to remove impurities such as Li₂CO₃ and LiOH from the surface, and then placed in a glove box for later use. A layer of Ag was deposited on both sides of the solid electrolyte sheet using a thermal evaporation coating apparatus to form an Ag / LLZTO / Ag blocking system. Lithium sheets were used as electrodes, and the system was encapsulated using button cells.

[0136] A small-amplitude sine wave with an AC amplitude of 0.01V was applied to the button cell using an electrochemical workstation at room temperature. The frequency of the applied sine wave was varied within the test frequency range of 1Hz to 1MHz to obtain a series of impedances at different frequencies. A Nyquist plot was obtained, with the real part of the impedance on the horizontal axis and the imaginary part on the vertical axis, with each point representing a different frequency. The left side of the plot represents the high-frequency region, which is semi-circular; the right side represents the low-frequency region, which is linear. According to equivalent circuit analysis, the intersection of the semi-circle with the real axis at low frequencies corresponds to the ionic resistance R of the solid electrolyte ceramic sheet. The conductivity was calculated using the following formula.

[0137] σ = 1 / ρ = L / (A × R)

[0138] Where σ represents conductivity, in units of S / m; L represents the length of the solid electrolyte ceramic sheet, in units of m; and A represents the cross-sectional area of ​​the solid electrolyte ceramic sheet, in units of m². 2 R represents the ionic resistance of the solid electrolyte ceramic sheet.

[0139] Mechanical performance testing:

[0140] Please see Figure 1 and Figure 2Nanoindentation is a commonly used method for testing the mechanical properties of materials. Because this technique is based on high-precision displacement testing, it is sometimes referred to in the literature as Depth-Sensing Indentation Technique (DSI); and because it requires a high-precision displacement and load testing device, it is sometimes called Instrumented Indentation Technique (IIT). It uses a computer-controlled indenter to press into the material under test, recording the continuous changes in load in real time and monitoring the indentation depth online, thus obtaining a load-depth curve. By studying the variation of the indenter load with the indentation depth, the material's microstructure's ability to resist external deformation can be understood, and the corresponding mechanical property parameters can be calculated. The entire indentation process includes two stages: loading and unloading. During loading, the load P exerted by the indenter on the material increases with the indentation depth h. After unloading, the indenter returns to its initial position, leaving indentation marks on the sample surface due to plastic deformation.

[0141] The most commonly used nanoindentation measurement technique is the Oliver-Pharr (O&P) method. Based on the experimentally measured load-depth curve, the elastic modulus can be determined, while the hardness (E) can be calculated from the maximum applied load (P). max The residual deformation area of ​​the indentation is obtained from the indentation.

[0142] In the parameter diagram of the nanoindentation process, h c A represents the contact depth when the indenter is pressed into the sample. c h represents the radius of contact between the test sample and the indenter. s This represents the displacement of the sample surface when the indenter is pressed into the sample. By recording the load (P) during the nanoindentation process as a function of the indenter's depth into the substrate (h), a load-depth curve is obtained (see attached figure below). Figure 2 ), where P max For the maximum load, h max For the maximum displacement, h f S represents the residual displacement after complete unloading, and S represents the elastic contact stiffness.

[0143] Load-depth curve

[0144] Cyclic life test:

[0145] The prepared solid electrolyte was polished to make its surface smooth, and then treated with glacial acetic acid to remove impurities such as Li₂CO₃. Nano-silver (300 nm thick) was vapor-deposited onto both sides of the LLZTO positive and negative electrodes under 50 A for 50 s. The vapor-deposited LLZTO and lithium foil (20 μm) were then placed in an Ar atmosphere furnace for hot pressing at 200 °C and 10 MPa for 10 minutes to ensure a tight bond between the lithium foil and LLZTO. The LLZTO with double-sided silver plating and lithium foil was used in a lithium-ion symmetric battery to test its cycle life against lithium.

[0146] Table 1

[0147]

[0148]

[0149] The prepared electrolytes were tested for density, ionic conductivity, and mechanical properties, and the results are shown in Table 1. Examples 1 to 16 show that the electrolyte in this application has a maximum density of 98.7% and a densification temperature of approximately 1100°C. Comparing with Comparative Examples 1 to 7, the electrolyte without the added zeolite imidazole ester framework has a maximum density of 95.9% and a densification temperature of approximately 1200°C. This indicates that adding a certain amount of zeolite imidazole ester framework to LLZO or LLZTO can improve the electrolyte density and lower the densification temperature. Furthermore, based on the electrolyte examples and corresponding comparative examples, adding a certain amount of zeolite imidazole ester framework to LLZO or LLZTO can improve the ionic conductivity and mechanical strength of the electrolyte.

[0150] As can be seen from Examples 1, 7 to 10 of the electrolyte, when the mass ratio of the zeolite imidazole ester skeleton to the solid electrolyte is about 2% to 4%, it is beneficial to further improve the density, ionic conductivity and mechanical strength of the electrolyte.

[0151] Based on examples 1, 11 to 15, Comparative Example 1, and Comparative Example 7, it is evident that Ta doping significantly improves the ionic conductivity of LLZO, but its effect on density and mechanical properties is not significant. However, LLZTO still suffers from poor mechanical properties and less-than-ideal ionic conductivity. When Ta doping reaches approximately 0.2 to 0.8%, and the mass ratio of the zeolite imidazole ester framework to the solid electrolyte is approximately 2% to 4%, the density, mechanical properties, and ionic conductivity of LLZTO can be further improved.

[0152] Preparation of application examples and comparative examples

[0153] The prepared lithium metal battery was subjected to cycle life testing, and the test results are as follows: Figures 4 to 5 And as shown in Table 2.

[0154] Table 2

[0155]

[0156]

[0157] Depend on Figure 4 , Figure 5 As shown in Table 2, adding a certain amount of ZIF-8 to the electrolyte is beneficial to improving the cycle life of lithium metal batteries. This is likely because adding a certain amount of zeolite imidazole ester framework to the electrolyte increases the electrolyte's density and mechanical strength, thereby preventing the formation of lithium dendrites and thus improving the cycle life of the lithium metal battery.

[0158] The technical solutions provided by the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for preparing a solid electrolyte, characterized in that, The preparation method includes: Obtain a solid electrolyte precursor; wherein the solid electrolyte precursor comprises a solid electrolyte and a zeolite imidazole ester framework, and the chemical formula of the solid electrolyte is Li. 7-x La3Zr 2-x Ta x O 12 , 0≤x≤1, calculated by mass, the solid electrolyte: zeolite imidazole ester skeleton = 100: (0.01-6). The solid electrolyte precursor is sintered at high temperature to obtain a solid electrolyte; the sintering temperature is 1000℃ to 1100℃.

2. The preparation method according to claim 1, characterized in that, Sintering involves high-temperature sintering under an inert atmosphere.

3. The preparation method according to claim 1, characterized in that, The heating rate during the sintering process is 5℃ / min to 20℃ / min.

4. The preparation method according to claim 1, characterized in that, The zeolite imidazole ester skeleton includes at least one of zeolite imidazole ester skeleton 8 and zeolite imidazole ester skeleton 67.

5. The preparation method according to claim 1, characterized in that, The steps for obtaining the solid electrolyte precursor include: The first mixture is obtained by mixing solid electrolyte powder and zeolite imidazole ester skeleton according to a preset ratio; Pressure is applied to the first mixture to obtain a solid electrolyte precursor.

6. A solid electrolyte, characterized in that, The solid electrolyte is prepared by the preparation method according to any one of claims 1 to 5.

7. A solid electrolyte, characterized in that, The solid electrolyte is prepared from a composite material, which includes a garnet-type solid electrolyte and a zeolite imidazole ester skeleton. By mass, the solid electrolyte: zeolite imidazole ester skeleton = 100: (0.01-6); the zeolite imidazole ester skeleton includes at least one of zeolite imidazole ester skeleton 8 and zeolite imidazole ester skeleton 67. The chemical formula of the solid electrolyte is Li. 7-x La3Zr 2-x Ta x O 12 The solid electrolyte has a density of 94% to 99%; an ionic conductivity of 0.7 mS / cm to 1.3 mS / cm; an elastic modulus of 84 GPa to 175 GPa; and a hardness of 7 GPa to 13 GPa.

8. The solid electrolyte as described in claim 7, characterized in that, By mass, the solid electrolyte: zeolite imidazole ester skeleton = 100:(1-5); and / or The particle size of the zeolite imidazole ester skeleton is 100 nm to 300 nm.

9. The solid electrolyte as described in claim 7 or 8, characterized in that, By mass, the solid electrolyte: zeolite imidazole ester skeleton = 100: (2-4).

10. The solid electrolyte as described in claim 7 or 8, characterized in that, 0.2≤x≤0.8。 11. A lithium metal battery, characterized in that, The lithium metal battery includes a positive electrode, a negative electrode, and a solid electrolyte as described in any one of claims 6 to 10, wherein the solid electrolyte is disposed between the positive electrode and the negative electrode.

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