Composite material for preparing solid-state electrolyte, solid-state electrolyte and preparation method, and lithium metal battery

Abstract

A composite material for preparing a solid-state electrolyte, the solid-state electrolyte and a preparation method, and a lithium metal battery, relating to the technical field of lithium-ion batteries. The composite material comprises a garnet-type solid-state electrolyte and a zeolitic imidazolate framework, wherein the ratio of the garnet-type solid-state electrolyte to the zeolitic imidazolate framework is 100:(0.01-6). The composite material can be used to prepare a solid-state electrolyte having a low densification temperature, high ionic conductivity, and high mechanical strength.

Description

Composite material for preparing solid-state electrolyte, solid-state electrolyte and preparation method, and lithium metal battery

[0001] This application claims priority to the Chinese patent application No. 202411320872.6 filed on September 20, 2024 with the Chinese Patent Office, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of lithium ion batteries, in particular to a composite material for preparing solid-state electrolyte, solid-state electrolyte and preparation method, and lithium metal battery. BACKGROUND

[0003] At present, lithium ion batteries have become one of the most important energy storage devices in people's daily life because of their long cycle life, high energy density and other advantages. In recent years, with the rapid development of electric vehicles, higher requirements have been put forward for the energy density and safety performance of batteries. All-solid-state lithium metal batteries replace flammable liquid electrolyte with solid-state electrolyte, and use metal lithium with higher theoretical specific capacity as the negative electrode, which has the advantages of high safety and high energy density, so it is of great significance to study all-solid-state lithium metal batteries.

[0004] Solid-state electrolyte is a core component of all-solid-state lithium metal batteries, which needs to meet the requirements of low preparation temperature, high density, high ionic conductivity and high mechanical strength, and at the same time, it needs to inhibit lithium dendrites and maintain long-term stable cycle of the battery while ensuring the rapid migration of lithium ions between the positive and negative electrodes.

[0005] Therefore, there is an urgent need in the art to provide a solid-state electrolyte with low preparation temperature, high density, high ionic conductivity and high mechanical strength. TECHNICAL PROBLEM TECHNICAL SOLUTION

[0006] Therefore, the present application provides a composite material for preparing solid-state electrolyte, which can be densified at a lower temperature, and the prepared solid-state electrolyte has high density, high ionic conductivity and high mechanical strength.

[0007] In a first aspect, the present application provides a composite material for preparing solid-state electrolyte, which comprises a garnet-type solid-state electrolyte and a zeolitic imidazolate framework, and the solid-state electrolyte: zeolitic imidazolate framework = 100:(0.01-6) by mass percentage.

[0008] The chemical formula of the solid-state electrolyte is Li 7-x La3Zr 2-x Ta x O 12 , 0≤x≤1.

[0009] In some embodiments of the present application, the solid-state electrolyte: zeolitic imidazolate framework = 100: (1-5).

[0010] In some embodiments of the present application, the solid-state electrolyte: zeolitic imidazolate framework = 100: (2-4).

[0011] In some embodiments of the present application, the zeolitic imidazolate framework includes at least one of zeolitic imidazolate framework 8 and zeolitic imidazolate framework 67.

[0012] In some embodiments of the present application, the particle size of the zeolitic imidazolate framework is 100 nm to 300 nm.

[0013] In some embodiments of the present application, 0.2≤x≤0.8.

[0014] The second aspect of the present application provides a preparation method of a solid-state electrolyte, the preparation method comprising:

[0015] obtaining a solid-state electrolyte precursor; wherein the solid-state electrolyte precursor includes a solid-state electrolyte and a zeolitic imidazolate framework, the chemical formula of the solid-state electrolyte is Li 7-x La3Zr 2-x Ta x O 12 , 0≤x≤1, calculated in terms of mass percentage, the solid-state electrolyte: zeolitic imidazolate framework = 100: (0.01-6);

[0016] sintering the solid-state electrolyte precursor at high temperature to obtain a solid-state electrolyte.

[0017] In some embodiments of the present application, the sintering temperature is 900°C to 1300°C; and / or

[0018] The high-temperature sintering includes high-temperature sintering under an inert atmosphere; and / or

[0019] The heating rate during the high-temperature sintering process is 5°C / min to 20°C / min.

[0020] In some embodiments of the present application, the sintering temperature is 1000°C to 1100°C; and / or

[0021] The step of obtaining a solid-state electrolyte precursor includes:

[0022] mixing the solid-state electrolyte powder and the zeolitic imidazolate framework in a preset ratio to obtain a first mixture;

[0023] applying a certain pressure to the first mixture to obtain a solid-state electrolyte precursor.

[0024] A third aspect of this application provides a solid electrolyte, which includes the aforementioned composite material or is prepared by the aforementioned preparation method.

[0025] In some embodiments of this application, the density of the solid electrolyte is 94% to 99%;

[0026] The ionic conductivity of the solid electrolyte is from 0.7 mS / cm to 1.3 mS / cm;

[0027] The elastic modulus of the solid electrolyte is 84 GPa to 175 GPa;

[0028] The hardness of the solid electrolyte is 7 GPa to 13 GPa.

[0029] 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. 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. Schematic diagram of parameters during the nanoindentation process.

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

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

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

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

[0037] Figure 6 is a process flow diagram of the preparation of the solid electrolyte of this application. Embodiments of the present invention

[0038] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts are within the scope of the present application. In addition, it should be understood that the specific implementations described herein are merely used to illustrate and explain the present application, and are not intended to limit the present 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 application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0040] In the present application, the orientation words such as "upper" and "lower" are generally used to refer to the upper and lower positions of the device in the actual use or working state, and specifically refer to the directions of the drawing surface in the drawings. In addition, in the description of the present application, the term "comprising" means "including but not limited to". The terms first, second, third, etc. are only used as labels and do not impose numerical requirements or establish sequences.

[0041] In the present application, "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which can represent the following cases: A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural.

[0042] In the present application, "at least one" means one or more, and "multiple" means two or more. "One or more", "at least one of the following" or the like means any combination of these items, including any combination of single item or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple.

[0043] Various embodiments of the present application can exist in a range of forms; it should be understood that the description in a range form is merely for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the range described has been specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has been 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., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fraction or integer) within the indicated range.

[0044] At present, lithium ion batteries have become one of the most important energy storage devices in people's daily life because of their long cycle life, high energy density and other advantages. In recent years, with the rapid development of electric vehicles, higher requirements have been put forward for the energy density and safety performance of batteries. The all-solid-state lithium metal battery replaces the flammable liquid electrolyte with a solid-state electrolyte, and uses metal lithium with higher theoretical specific capacity as the negative electrode, which has the advantages of high safety and high energy density, so it is of great significance to study the all-solid-state lithium metal battery.

[0045] The solid-state electrolyte is a core component of the all-solid-state lithium metal battery, which needs to meet the requirements of low preparation temperature, high ionic conductivity and high mechanical strength, and at the same time, inhibit lithium dendrites and maintain long-term stable cycle of the battery while ensuring fast migration of lithium ions between the positive and negative electrodes.

[0046] The common solid-state electrolytes at present include oxide solid-state electrolyte, sulfide solid-state electrolyte, composite solid-state electrolyte and emerging halide solid-state electrolyte, etc. The oxide solid-state electrolyte is widely studied as a material with high ionic conductivity, stable structure, simple synthesis process, non-toxic and non-polluting. Among many solid-state electrolytes, garnet-type Li7La3Zr2O 12 (LLZO) is of great concern because of its high ionic conductivity and good electrochemical stability. However, LLZO still has problems of suboptimal ionic conductivity, low mechanical strength and high densification temperature.

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

[0048] Specifically, the composite material provided by the embodiments of the present application comprises a garnet-type solid-state electrolyte and a zeolitic imidazolate framework, and the solid-state electrolyte: zeolitic imidazolate framework = 100:(0.01-6) (i.e. any value between 0.01 and 6) by mass, wherein the chemical formula of the solid-state electrolyte is Li7-x La3Zr 2-x Ta x O 12 , 0≤x≤1.

[0049] In the present application, by adding a certain amount of zeolite imidazolate framework in the preparation of solid electrolyte composite material, a solid electrolyte with lower densification temperature, higher ion conductivity and higher mechanical strength can be prepared from the composite material in the present application.

[0050] Exemplarily, the zeolite imidazolate framework: solid electrolyte is about 0.01%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6% or any value between the two aforementioned point values in terms of mass percentage.

[0051] Exemplarily, x is about 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or any value between the two aforementioned point values. It should be noted that "about" in the present application means a value within ±10% of the number. Taking the number 1 as an example, correspondingly, about 1 refers to any value between 0.9 and 1.1.

[0052] In some embodiments of the present application, the solid electrolyte: zeolite imidazolate framework = 100:(1-5) in terms of mass percentage. Further, the solid electrolyte: zeolite imidazolate framework = 100:(1-3), and further, the solid electrolyte: zeolite imidazolate framework = 100:(1.5-2.5). Controlling the zeolite imidazolate framework in this range in this embodiment can further reduce the densification temperature and improve the ion conductivity and mechanical strength of the solid electrolyte.

[0053] In some embodiments of the present application, X is greater than 0. That is, the solid electrolyte is LLZTO formed by doping Ta element into LLZO. In this embodiment, by doping Ta element, the ion conductivity of the solid electrolyte is further improved.

[0054] It should be noted that although the lithium ion conductivity of LLZTO is greatly improved compared with LLZO, the lithium ion conductivity is still not ideal, and LLZTO also has the problems of low density and high densification temperature. In this embodiment, by compounding the zeolite imidazolate framework with the LLZTO, the density of the LLZTO can be improved, the densification temperature (referring to the heat treatment temperature when the densification is completed) can be reduced, and the ion conductivity and mechanical strength of the solid electrolyte can be improved.

[0055] In some embodiments of the present application, 0.1≤x≤0.9. Further, 0.4≤x≤0.8. Still further, 0.5≤x≤0.7. By controlling the content of the Ta element doping in the embodiments, the ion conductivity and mechanical strength of the solid-state electrolyte can be further improved.

[0056] In some embodiments of the present application, the zeolitic imidazolate framework includes at least one of zeolitic imidazolate framework 8 (i.e., ZIF-8) and zeolitic imidazolate framework 67 (ZIF-67).

[0057] Referring to FIG. 6, the second aspect of the embodiments of the present application provides a preparation method of a solid-state electrolyte, and the preparation method includes the following steps:

[0058] S10 obtains a solid-state electrolyte precursor; wherein the solid-state electrolyte precursor includes a solid-state electrolyte and a zeolitic imidazolate framework, and the chemical formula of the solid-state electrolyte is Li 7-x La3Zr 2-x Ta x O 12 , 0≤x≤1, and the solid-state electrolyte: zeolitic imidazolate framework = 100:(0.01-6) in terms of mass percentage.

[0059] S20 sintering the solid-state electrolyte precursor at a high temperature to obtain a solid-state electrolyte.

[0060] In the present application, by adding a certain content of the zeolitic imidazolate framework into the solid-state electrolyte, a solid-state electrolyte with a lower densification temperature, higher ion conductivity and higher mechanical strength can be prepared from the composite material in the present application.

[0061] For example, the zeolitic imidazolate framework: solid-state electrolyte is about 0.01%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6% or any value between any two of the above values in terms of mass percentage.

[0062] For example, x is about 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or any value between any two of the above values. It should be noted that "about" in the present application means a value within ±10% of the number. For example, if the number is 1, about 1 means any value between 0.9 and 1.1.

[0063] In some embodiments of the present application, the solid-state electrolyte: zeolitic imidazolate framework = 100: (1-5) in percentage by mass. Further, the solid-state electrolyte: zeolitic imidazolate framework = 100: (1-3), and more further, the solid-state electrolyte: zeolitic imidazolate framework = 100: (1.5-2.5). Controlling the zeolitic imidazolate framework in this range in this embodiment can further reduce the densification temperature and improve the ionic conductivity and mechanical strength of the solid-state electrolyte.

[0064] In some embodiments of the present application, X is greater than 0. That is, the solid-state electrolyte is LLZTO formed by doping Ta element to LLZO. In this embodiment, by doping Ta element, the ionic conductivity of the solid-state electrolyte can be further improved.

[0065] It should be noted that although the lithium ion conductivity of LLZTO is greatly improved compared with LLZO, the lithium ion conductivity of LLZTO is still not ideal, and LLZTO also has the problems of low density and high densification temperature. In this embodiment, by compounding the zeolitic imidazolate framework with LLZTO, the density of LLZTO can be improved, the densification temperature (referring to the heat treatment temperature when the densification is completed) can be reduced, and the ionic conductivity and mechanical strength of the solid-state electrolyte can be improved.

[0066] In some embodiments of the present application, 0.1≤x≤0.9. Further, 0.4≤x≤0.8. More further, 0.5≤x≤0.7. In this embodiment, by controlling the content of Ta element doping, the ionic conductivity and mechanical strength of the solid-state electrolyte can be further improved.

[0067] In some embodiments of the present application, the sintering temperature is 900-1300°C. Illustratively, the sintering temperature is about 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, and any value between any two of the foregoing values.

[0068] Further, the sintering temperature is 1000-1100°C. In this sintering temperature range, the electrolyte in the present application can be densified, which is conducive to reducing the cost.

[0069] In some embodiments of the present application, the high-temperature sintering includes high-temperature sintering in an inert atmosphere. Illustratively, the inert atmosphere includes argon. Of course, in other embodiments of the present application, the inert atmosphere can also include other inert gases, which are not limited herein.

[0070] In some embodiments of the present application, the temperature increasing rate in the high-temperature sintering process is 5-20℃ / min. For example, the temperature increasing rate is about 5℃ / min, 10℃ / min, 15℃ / min, 20℃ / min, or any value between any two of the aforementioned values.

[0071] In some embodiments of the present application, the step of obtaining the solid-state electrolyte precursor comprises: mixing the solid-state electrolyte and the zeolitic imidazolate framework (ZIF) in a preset ratio to obtain a first mixture; and applying a certain pressure to the first mixture to obtain the solid-state electrolyte precursor.

[0072] It should be noted that the solid-state electrolyte and the zeolitic imidazolate framework (ZIF) in the embodiments of the present application can be prepared by oneself or obtained from the market, which is not limited herein.

[0073] In some embodiments of the present application, the zeolitic imidazolate framework (ZIF) comprises at least one of ZIF-8 and ZIF-67.

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

[0075] For example, the solid-state electrolyte is prepared by mixing Li 6.4 La3Zr 1.4 Ta 0.6 O 12LiOH H2O, La2O3, ZrO2 and Ta2O5 (lithium source content needs to be added 10% more than the theoretical content) are weighed according to the stoichiometric ratio of 7.0:1.5:1.4:0.6. The prepared raw materials are fully mixed and then placed in a ball mill tank, and an appropriate amount of isopropyl alcohol is added. The first mixture after ball milling is obtained under the condition of 300 rpm for 12 hours. The first mixture after ball milling is dried to obtain a dry second mixture. The second mixture is placed in a tube furnace for high-temperature sintering. The high-temperature sintering condition is 900℃ for 12 hours, and the heating rate is 10℃ / min. After the reaction is completed, the sample is naturally cooled in the tube furnace and the product is taken out. The product is placed in a zirconia ball mill tank, and an appropriate amount of ethanol is added for ball milling at a speed of 300 rpm for 12 hours for powder refinement. After the powder is dried, it is screened to obtain LLZTO (Li 6.4 La3Zr 1.4 Ta 0.6 O 12 ) powder with a size of about 500nm.

[0076] Exemplarily, the preparation of the solid-state electrolyte includes: mixing the prepared solid-state electrolyte powder and zeolite imidazolate framework according to a preset ratio to obtain a composite material, and then placing the composite material in a mold for uniaxial pressing to obtain a solid-state electrolyte precursor (i.e., a solid-state electrolyte ceramic sheet). The obtained solid-state electrolyte precursor is subjected to high-temperature sintering under argon, and is heat-treated at 1100℃ in an argon environment for 12 hours, with a heating rate of 10℃ / min. After the heat treatment is completed, the sample is naturally cooled in a tube furnace to obtain a test sample (i.e., a solid-state electrolyte).

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

[0078] The fourth aspect of the embodiments of the present application provides a lithium metal battery, which comprises the solid-state electrolyte. It can be understood that, since the lithium metal battery in the present application comprises the solid-state electrolyte described above, it also has the beneficial effects of the solid-state electrolyte described above, and has a good cycle life.

[0079] Specifically, the lithium metal battery comprises a positive electrode, a negative electrode, and a solid-state electrolyte disposed between the positive electrode and the negative electrode. Exemplarily, the negative electrode comprises lithium metal or lithium alloy.

[0080] The electrolyte and lithium ion battery in the present application will be further described below in conjunction with specific embodiments.

[0081] Electrolyte Example 1

[0082] ZIF-8 Preparation: Using the method of mechanical stirring at room temperature, 1.835 g of zinc nitrate hexahydrate was dissolved in 125 ml of methanol to prepare solution A, and 4.058 g of dimethyl imidazole was dissolved in 125 ml of methanol to prepare solution B. Solution A was slowly added to solution B, and the solution became a milky white liquid. The beaker was sealed with a sealing film and stirred for 20 h, then centrifuged (7000 rpm, 10 min) and washed with methanol three times, and placed in a vacuum drying oven for 12 h. Finally, the dried ZIF-8 solid was ground for use. The particle size of ZIF-8 was about 200 nm. The diffraction pattern thereof is shown in FIG. 3. As can be seen from FIG. 3, 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 has been successfully prepared.

[0083] Solid-state electrolyte (LLZTO) preparation: LiOH H2O, La2O3, ZrO2 and Ta2O5 were weighed according to the stoichiometric ratio of 7.0:1.5:1.4:0.6 to prepare Li 6.4 La3Zr 1.4 Ta 0.6 O 12 , wherein the lithium source content needs to be added by 10% compared to the theoretical content. The prepared raw materials were fully mixed and placed in a ball mill tank, and an appropriate amount of isopropanol was added. The ball milling was carried out at a speed of 300 rpm for 12 hours. After drying, the mixed sample raw materials were placed in a tube furnace for high-temperature sintering. The high-temperature sintering conditions were 900℃ for 12 hours, and the heating rate was 10℃ / min. After the reaction was completed, the sample was placed in the tube furnace for natural cooling and the product was taken out. The product was placed in a zirconia ball mill tank, an appropriate amount of ethanol was added, and the ball milling was carried out at a speed of 300 rpm for 12 hours for powder refinement. After drying the powder, the LLZTO (Li 6.4 La3Zr 1.4 Ta 0.6 O 12 ) powder with a size of about 500 nm was obtained through screening.

[0084] Solid-state electrolyte preparation: The prepared LLZTO powder and ZIF-8 were mixed according to a mass ratio of 100:2, and uniaxial pressing was performed in a mold to obtain a solid-state electrolyte ceramic sheet. High-temperature sintering was performed under argon, and heat treatment was carried out at 1100℃ for 12 hours in an argon environment at a heating rate of 10℃ / min. After heat treatment, the sample was placed in a tube furnace for natural cooling to obtain a test sample.

[0085] Electrolyte Example 2

[0086] The difference between it and Example 1 is that the temperature of the heat treatment in the preparation process of the solid-state electrolyte is 1050℃.

[0087] Electrolyte Example 3

[0088] The difference from Example 1 is that the temperature of heat treatment during the preparation of the solid-state electrolyte is 1150°C.

[0089] Electrolyte Example 4

[0090] The difference from Example 1 is that the temperature of heat treatment during the preparation of the solid-state electrolyte is 1200°C.

[0091] Electrolyte Example 5

[0092] The difference from Example 1 is that the temperature of heat treatment during the preparation of the solid-state electrolyte is 1250°C.

[0093] Electrolyte Example 6

[0094] The difference from Example 1 is that the temperature of heat treatment during the preparation of the solid-state electrolyte is 1300°C.

[0095] Electrolyte Example 7

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

[0097] Electrolyte Example 8

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

[0099] Electrolyte Example 9

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

[0101] Electrolyte Example 10

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

[0103] Electrolyte Example 11

[0104] The difference from Example 1 is that the solid-state electrolyte prepared is Li 6.8 La3Zr 1.8 Ta 0.2 O 12 .

[0105] Electrolyte Example 12

[0106] The difference from Example 1 is that the solid-state electrolyte prepared is Li 6.6 La3Zr 1.6 Ta 0.4 O 12 .

[0107] Electrolyte Example 13

[0108] The difference from Example 1 is that the solid-state electrolyte prepared is Li 6.2 La3Zr 1.2 Ta 0.8 O 12 .

[0109] Electrolyte Example 14

[0110] The difference from Example 1 is that the solid-state electrolyte prepared is Li 12 .

[0111] Electrolyte Example 15

[0112] The difference from Example 1 is that the solid-state electrolyte prepared is LLZO (Li 12 ).

[0113] Electrolyte Example 16

[0114] The difference from Example 1 is that the LLZTO powder is mixed with ZIF-67 in a mass ratio of 100:2.

[0115] Electrolyte Comparative Example 1

[0116] Solid-state electrolyte (LLZTO) preparation: Li 6.4 La3Zr 1.4 Ta 0.6 O 12 , wherein the lithium source content needs to be added by 10% compared to the theoretical content. After mixing the prepared raw materials, they are placed in a ball mill tank and an appropriate amount of isopropanol is added. Ball milling is carried out at a speed of 300 rpm for 12 hours. After drying, the mixed sample raw materials are placed in a tube furnace for high-temperature sintering. The high-temperature sintering conditions are 900°C for 12 hours, and the heating rate is 10°C / min. After the reaction is completed, the sample is placed in the tube furnace for natural cooling and the product is taken out. The product is placed in a zirconia ball mill tank, an appropriate amount of ethanol is added, and ball milling is carried out at a speed of 300 rpm for 12 hours for powder refinement. After drying the powder, it is screened to obtain LLZTO (Li 6.4 La3Zr1.4 Ta 0.6 O 12 ) powder.

[0117] Preparation of solid electrolyte: the prepared LLZTO powder was put into a mold for uniaxial tabletting, and the obtained solid electrolyte ceramic sheet was sintered at high temperature under argon, and was heat treated at 1100°C for 12 hours under argon, with a heating rate of 10°C / min; after the heat treatment, the sample was naturally cooled in a tube furnace to obtain a test sample.

[0118] The difference between it and Example 1 is that no ZIF-8 is added to the solid electrolyte.

[0119] Electrolyte Comparative Example 2

[0120] The difference between it and Example 2 is that no ZIF-8 is added to the solid electrolyte.

[0121] Electrolyte Comparative Example 3

[0122] The difference between it and Example 3 is that no ZIF-8 is added to the solid electrolyte.

[0123] Electrolyte Comparative Example 4

[0124] The difference between it and Example 4 is that no ZIF-8 is added to the solid electrolyte.

[0125] Electrolyte Comparative Example 5

[0126] The difference between it and Example 5 is that no ZIF-8 is added to the solid electrolyte.

[0127] Electrolyte Comparative Example 6

[0128] The difference between it and Example 6 is that no ZIF-8 is added to the solid electrolyte.

[0129] Electrolyte Comparative Example 7

[0130] The difference between it and Example 15 is that no ZIF-8 is 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 / cm 3The actual density is measured by Archimedes displacement method. The buoyancy force of the object immersed in the liquid can be obtained by the difference between the actual weight ml and the apparent weight m2 ("apparent weight" refers to the weight measured by the object immersed in the liquid), and the volume of the object is obtained by Archimedes principle, V=(m1-m2) / (pg), and the density of the object is: pobject=m1*pliquid / (m1-m2).

[0134] Ion conductivity test:

[0135] After polishing and cleaning the sintered solid electrolyte ceramic sheet, immersing it in glacial acetic acid for 30s to remove surface impurities such as Li2CO3 and LiOH, and then placing it in a glove box for standby. A layer of Ag is evaporated on both sides of the solid electrolyte sheet using a thermal evaporation coating instrument to form an Ag / LLZTO / Ag blocking system, a lithium sheet is used as an electrode, and a button cell is used for packaging.

[0136] An electrochemical workstation is used to apply a small amplitude sinusoidal wave to the button cell, with an alternating amplitude of 0.01V and a test temperature of room temperature. The frequency of the applied small amplitude sinusoidal wave is changed in the test frequency range of 1Hz-1MHz to obtain a series of impedances at different frequencies. The real part of the impedance is taken as the horizontal axis and the imaginary part is taken as the vertical axis, and each point represents a different frequency to obtain the Nyquist plot. The left side of the graph has a high frequency, which is called the high frequency region, and the high frequency region is semicircular. The right side has a low frequency, which is called the low frequency region, and the low frequency region is linear. According to the equivalent circuit analysis, the intersection of the semicircle with the real axis at low frequency corresponds to the ionic resistance R of the solid electrolyte ceramic sheet. The conductivity is calculated according to the following formula. σ=1 / ρ=L / (A×R)

[0137] Where σ represents the conductivity, with a unit of S / m; L represents the length of the solid electrolyte ceramic sheet, with a unit of m; A represents the cross-sectional area of the solid electrolyte ceramic sheet, with a unit of m 2 ; R represents the ionic resistance of the solid electrolyte ceramic sheet.

[0138] Mechanical property test:

[0139] Please refer to Fig. 1 and Fig. 2, nanoindentation technique is a commonly used method for testing the mechanical properties of materials, since this technique is based on high-precision displacement testing, sometimes referred to as depth-sensitive indentation technique (Depth-Sensing Indentation Technique, DSI) in the literature; again, since this technique needs to be assisted by high-precision displacement and load testing device, sometimes referred to as instrumented indentation technique (Instrumented Indentation Technique, IIT) in the literature. It controls the indenter to press into the material to be tested through the computer, records the continuous change of load in real time, and monitors the indentation depth online, so as to obtain the load-depth curve, by studying the change rule of indenter load with indentation depth, the ability of microstructure of material to resist external force deformation can be understood, and the corresponding mechanical property parameters can be calculated, the whole indentation process includes loading and unloading two stages. During the loading process, the load P acting on the material by the indenter will increase with the increase of indentation depth h, after unloading, the indenter returns to the initial position, and the indentation trace will be left on the surface of the sample, which is caused by the plastic deformation of the sample.

[0140] The most commonly used method of nanoindentation measurement technology is Oliver-Pharr (O&P). According to the measured load-depth curve, the elastic modulus can be obtained according to the load-depth curve, and the hardness (E) can be obtained by the maximum loading load (P max ) and the residual deformation area of indentation.

[0141] In the parameter diagram of nanoindentation process, h c represents the contact depth when the indenter is pressed into the sample, A c represents the radius of the sample in contact with the indenter, h s represents the displacement of the sample surface when the indenter is pressed into the sample. By recording the change of load (P) with the change of indenter indentation depth (h) in the nanoindentation process, the load-depth curve (as shown in the following Fig. 2) is obtained, in which P max is the maximum load, h max is the maximum displacement, h f is the residual displacement after complete unloading, and S is the elastic contact stiffness.

[0142] Load-depth curve

[0143] Cycle life test:

[0144] The prepared solid electrolyte is polished and polished to make its surface flat, and the surface is treated with glacial acetic acid to remove impurities such as Li2CO3. Nano-silver (thickness 300 nm) is evaporated on the positive and negative electrodes of the LLZTO, and the evaporation conditions are 50 A and 50 s. The LLZTO and lithium foil (20 um) after evaporation are placed in an atmosphere furnace (Ar) for hot pressing, with a temperature of 200°C, a pressure of 10 MPa, and a pressure holding time of 10 minutes, to ensure that the lithium foil and the LLZTO are tightly attached. The LLZTO with silver coating on both sides and lithium foil is used for lithium symmetric battery, and the cycle life to lithium is detected.

[0145] Table 1

[0146] The prepared electrolyte is tested for density, ion conductivity and mechanical properties, and the test results are shown in Table 1. As can be seen from Examples 1 to 16, the density of the electrolyte in the present application can reach 98.7% at most, and the densification temperature is about 1100°C. As can be seen from Comparative Examples 1 to 7, the density of the electrolyte without adding zeolite imidazolate framework is at most 95.9%, and the densification temperature is about 1200°C. It can be seen that adding a certain amount of zeolite imidazolate framework to LLZO or LLZTO can improve the density of the electrolyte and reduce the densification temperature. At the same time, as can be seen from the electrolyte examples and the corresponding electrolyte comparative examples, adding a certain amount of zeolite imidazolate framework to LLZO or LLZTO can improve the ion conductivity and mechanical strength of the electrolyte.

[0147] As can be seen from electrolyte examples 1, 7 to 10, when the mass ratio of zeolite imidazolate framework to solid electrolyte in the electrolyte is about 2% to 4%, it is beneficial to further improve the density, ion conductivity and mechanical strength of the electrolyte.

[0148] As can be seen from electrolyte examples 1, 11 to 15, comparative example 1 and comparative example 7, Ta element doping can significantly improve the ion conductivity of LLZO, but the improvement of density and mechanical properties is not obvious. However, LLZTO still has the problems of poor mechanical properties and unsatisfactory ion conductivity. When the Ta element doping is about 0.2 to 0.8, and the mass ratio of zeolite imidazolate framework to solid electrolyte in the electrolyte is about 2% to 4%, the density, mechanical properties and ion conductivity of LLZTO can be further improved.

[0149] Preparation of application examples and comparative examples

[0150] The prepared lithium metal battery is tested for cycle life, and the test results are shown in Figures 4 to 5 and Table 2.

[0151] Table 2

[0152] As can be seen from FIG. 4, FIG. 5 and Table 2, adding a certain amount of ZIF-8 in the electrolyte is conducive to improving the cycle life of the lithium metal battery. The possible reason is that adding a certain amount of zeolitic imidazolate framework in the electrolyte improves the compactness and mechanical strength of the electrolyte, thereby enhancing the ability to block lithium dendrites, and further improving the cycle life of the lithium metal battery.

[0153] The technical solutions provided by the embodiments of the present application are described in detail above, and specific examples are applied in this paper to describe the principles and implementation modes of the present application. The above description of the embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed, and the above description of the present application should not be understood as a limitation.

Claims

1. A composite material for preparing a solid-state electrolyte, comprising a garnet-type solid-state electrolyte and a zeolitic imidazolate framework, wherein the solid-state electrolyte: zeolitic imidazolate framework = 100: (0.01-6) by mass. wherein The chemical formula of the solid-state electrolyte is Li 7-x La3Zr 2-x Ta x O 12 , 0≤x≤1.

2. The composite material of claim 1, wherein, The solid-state electrolyte: zeolitic imidazolate framework = 100: (1-5) by mass.

3. The composite material of claim 1, wherein, The zeolitic imidazolate framework comprises at least one of zeolitic imidazolate framework 8 and zeolitic imidazolate framework 67.

4. The composite material of claim 1, wherein, The particle size of the zeolitic imidazolate framework is 100 nm to 300 nm.

5. The composite material of claim 2, wherein, The solid-state electrolyte: zeolitic imidazolate framework = 100: (2-4) by mass.

6. The composite material of claim 2, wherein, The solid-state electrolyte: zeolitic imidazolate framework = 100: (1.5-2.5) by mass.

7. The composite material of any one of claims 1 to 6, wherein, 0.2≤x≤0.8。 8. A method of making a solid state electrolyte, wherein, The preparation method comprises: obtaining a solid-state electrolyte precursor; wherein the solid-state electrolyte precursor comprises a solid-state electrolyte and a zeolitic imidazolate framework, the chemical formula of the solid-state electrolyte is Li 7-x La3Zr 2-x Ta x O 12 , 0≤x≤1, the solid-state electrolyte: zeolitic imidazolate framework = 100:(0.01-6) by mass. high-temperature sintering the solid-state electrolyte precursor to obtain a solid-state electrolyte.

9. The production method according to claim 8, wherein The sintering temperature is 900℃ to 1300℃.

10. The production method according to claim 8, wherein The sintering temperature is 1000℃ to 1100℃.

11. The production method according to claim 8, wherein The sintering comprises high-temperature sintering under an inert atmosphere.

12. The production method according to claim 8, wherein The heating rate during sintering is 5℃ / min to 20℃ / min.

13. The production method according to claim 8, wherein The zeolitic imidazolate framework comprises at least one of zeolitic imidazolate framework 8 and zeolitic imidazolate framework 67. 14.The preparation method of claim 8, wherein, The step of obtaining a solid-state electrolyte precursor comprises: mixing the solid-state electrolyte powder and the zeolitic imidazolate framework in a preset ratio to obtain a first mixture; applying pressure to the first mixture to obtain a solid-state electrolyte precursor.

15. A solid state electrolyte, wherein, The solid-state electrolyte comprises the composite material of any one of claims 1 to 7, or is prepared by the preparation method of any one of claims 8 to 14.

16. The solid state electrolyte of claim 15, wherein, The solid-state 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.

17. The solid state electrolyte of claim 16, wherein, The solid-state electrolyte has a density of 96.2% to 99%.

18. The solid state electrolyte of claim 16, wherein, The solid-state electrolyte has an ionic conductivity of 1.1 mS / cm to 1.3 mS / cm.

19. The solid state electrolyte of claim 16, wherein, The solid-state electrolyte has an elastic modulus of 110 GPa to 175 GPa.

20. The solid state electrolyte of claim 16, wherein, The solid-state electrolyte has a hardness of 9.5 GPa to 13 GPa.

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