Halide solid electrolyte, preparation method thereof and solid-state battery

Abstract

The invention relates to the technical field of solid-state batteries, and discloses a halide solid-state electrolyte and a preparation method thereof, and a solid-state battery, and the preparation method comprises the following steps: mixing raw materials according to the molar ratio of the chemical formula LixInCly, and carrying out grinding treatment to obtain mixed powder; tabletting the mixed powder, placing in inert gas, heating to a first temperature at a first heating rate, preserving heat for a first time, heating to a second temperature at a second heating rate, preserving heat for a second time, and cooling to room temperature at a third cooling rate to obtain the halide solid electrolyte, wherein the first temperature ranges from 200 DEG C to 250 DEG C, and the second temperature ranges from 300 DEG C to 400 DEG C. Compared with a method in the prior art that liquid-phase synthesis is performed and then vacuum heat treatment or high-energy ball milling is performed and then heat treatment is performed, the inert gas atmosphere adopted by the invention effectively inhibits oxidation of In < 3 + >, reduces generation of impurity phases (such as InOCl), and remarkably improves the ionic conductivity of the electrolyte.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and in particular to a halide solid electrolyte, a preparation method thereof, and a solid-state battery. Background Art

[0002] With the rapid development of today's society, the challenges brought about by the rapid growth of current energy demand and the reduction of traditional non-renewable energy reserves are becoming increasingly severe. The high utilization rate of traditional energy sources such as oil, coal and natural gas has further led to environmental unsustainability and degradation. Since 2020, as my country's new energy vehicle market continues to boom, the demand for lithium-ion batteries has soared, and all-solid-state lithium batteries have emerged. Solid electrolytes are one of the key components of all-solid-state batteries, and there are many types, each with its own advantages and disadvantages. Common solid electrolytes include halides, oxides, polymers and halide solid electrolytes. Among them, halide solid electrolytes have attracted widespread attention due to their unique advantages (such as low Coulomb force between lithium ions and anions, good mechanical deformability, etc.).

[0003] At present, the preparation of traditional halide solid electrolytes is mainly divided into liquid phase method and solid phase method. Among them, the solid phase method is mainly used for small-scale laboratory production. For example, the Chinese invention patent with publication number CN110994010A discloses a halide solid electrolyte and its preparation method. The lithium halide and non-metallic halide are ball-milled and then subjected to spark plasma sintering or electric field assisted sintering. This method has a long synthesis cycle, a relatively complicated preparation process, and limited one-time output. The liquid phase method is generally suitable for mass production. For example, the document (Angew.Chem.Int.Ed.2019,58,16427.) uses a liquid phase method to prepare the halide solid electrolyte Li3InCl6. However, this preparation method requires high vacuum equipment, and the particle size of the prepared solid electrolyte is large and the uniformity is poor, which cannot meet the requirements of commercial applications.

[0004] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a halide solid electrolyte, a preparation method thereof, and a solid-state battery, so as to solve the problem that impurities are easily introduced into the existing method for preparing halide solid electrolytes.

[0006] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0007] A first aspect of the present invention provides a method for preparing a halide solid electrolyte, the method comprising the following steps:

[0008] According to Li x InCly The raw materials are mixed and ground in a molar ratio according to the chemical formula to obtain a mixed powder, wherein 2.5<x<3.5, 5.5<y<6.5;

[0009] The mixed powder is pressed into a tablet and placed in an inert gas, heated to a first temperature at a first heating rate and then kept at that temperature for a first time, then heated to a second temperature at a second heating rate and then kept at that temperature for a second time, and then cooled to room temperature at a third cooling rate to obtain the halide solid electrolyte;

[0010] Wherein, the first temperature is 200-250°C, and the second temperature is 300-400°C.

[0011] Preferably, the raw materials include LiCl and InCl3, and the molar ratio of LiCl to InCl3 is (2.5-3.5):1.

[0012] Preferably, the grinding step is specifically: using a high-speed shear mixing device to process the mixed raw materials at a rotation speed of 10,000-20,000 rpm for 1-10 minutes.

[0013] Preferably, the first heating rate is 2-5°C / min, the second heating rate is 3-5°C / min, and the third cooling rate is 5-10°C / min.

[0014] Preferably, the first time is 2-4 hours, and the second time is 8-10 hours.

[0015] Preferably, the inert gas is one or more of argon, helium, neon, and nitrogen, with a flow rate of 10-50 mL / min and a purity of ≥99%.

[0016] A second aspect of the present invention provides a halide solid electrolyte, which is prepared using the above-mentioned preparation method.

[0017] Preferably, the D50 particle size of the halide solid electrolyte is ≤2 μm.

[0018] Preferably, the ionic conductivity of the halide solid electrolyte at room temperature is 2.1-2.5 mS / cm.

[0019] According to a third aspect of the present invention, a solid-state battery is provided, comprising a positive electrode, a negative electrode, and the above-mentioned halide solid electrolyte disposed between the positive electrode and the negative electrode.

[0020] Beneficial effects:

[0021] The present invention discloses a halide solid electrolyte and its preparation method, and a solid-state battery. Compared with the prior art method of using liquid phase synthesis followed by vacuum heat treatment or high-energy ball milling followed by heat treatment, the present invention combines gradient low-temperature sintering to avoid rapid growth of raw material grains at high temperatures, forming a dense and fine grain structure. In addition, the dynamic inert gas atmosphere effectively suppresses the In 3+ The oxidation of the electrolyte can reduce the generation of impurity phases (such as InOCl) and significantly improve the ionic conductivity of the electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the SEM image of the Li3InCl6 halide solid electrolyte prepared in Example 1 of the present invention.

[0023] Figure 2 This is the SEM image of the Li3InCl6 halide solid electrolyte prepared in Comparative Example 1 of the present invention.

[0024] Figure 3 This is the SEM image of the Li3InCl6 halide solid electrolyte prepared in Comparative Example 2 of the present invention.

[0025] Figure 4 XRD patterns of the Li3InCl6 halide solid electrolyte prepared in Example 1 of the present invention and the mixed powder in Example 1. DETAILED DESCRIPTION

[0026] The present invention provides a halide solid electrolyte, a preparation method thereof, and a solid-state battery. To clarify the objectives, technical solutions, and effects of the present invention, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0027] In the prior art, the preparation of halide solid electrolytes mostly adopts manual grinding or ball milling combined with high-temperature sintering process (such as CN117410550A, CN116031475A). However, manual mixing is inefficient and it is difficult to ensure the uniformity of raw materials. Although ball milling can improve uniformity, it has the following problems: (1) ball milling time is long (usually 20-50 hours) and energy consumption is high; (2) impurities are easily introduced during the ball milling process (such as grinding medium wear); (3) the mixed raw material powder still needs to be sintered at high temperature (>500℃), resulting in grain coarsening and affecting ionic conductivity.

[0028] Furthermore, while the existing liquid-phase method can be used for mass production, it requires high-vacuum equipment and produces large, poorly uniform crystals (>10 μm). Therefore, there is an urgent need for an efficient, low-energy, scalable preparation method that can simplify the process while improving the crystallinity and electrochemical performance of the electrolyte.

[0029] Based on this, an embodiment of the present invention provides a method for preparing a halide solid electrolyte, the preparation method comprising the following steps:

[0030] According to Li x InCl y The raw materials are weighed and ground to obtain a mixed powder according to the molar ratio of the chemical formula, wherein 2.5<x<3.5, 5.5<y<6.5;

[0031] The mixed powder is pressed into a tablet and placed in an inert gas, heated to a first temperature at a first heating rate and then kept at that temperature for a first time, then heated to a second temperature at a second heating rate and then kept at that temperature for a second time, and then cooled to room temperature at a third cooling rate to obtain the halide solid electrolyte;

[0032] Wherein, the first temperature is 200-250°C, and the second temperature is 300-400°C.

[0033] In the preparation method of the embodiment of the present invention, the halide solid electrolyte mixed powder is ground and mixed and then subjected to low-temperature heat treatment. Compared with the liquid phase synthesis and vacuum heat treatment or the traditional high-energy ball milling and heat treatment method in the prior art, it does not require the cumbersome and equipment-intensive processes of dissolving the raw materials in a solvent for reaction and then vacuum evaporation crystallization or long-term high-energy ball milling. At the same time, kilogram-level mixed powder can be prepared at one time, greatly improving the preparation efficiency, simplifying the overall process flow, reducing the preparation time cost, and improving the industrialization process.

[0034] Specifically, compared with the existing technology, the present invention suppresses abnormal grain growth and improves crystallinity through gradient temperature sintering (such as heating to a first temperature at a first heating rate and then keeping it warm for a first time, then heating to a second temperature at a second heating rate and keeping it warm for a second time); introduces inert gas dynamic atmosphere control (such as argon flow rate of 10-50mL / min) to reduce the generation of impurities during sintering. The above process combination makes the particle size distribution of the halide solid electrolyte more uniform (D50 <2μm), the ionic conductivity is increased to 2.1-2.5mS / cm (compared to 1.2-1.8mS / cm in the existing technology), and is suitable for kilogram-level mass production.

[0035] In some embodiments, the raw materials include LiCl and InCl3, and the molar ratio of LiCl to InCl3 is (2.5-3.5):1.

[0036] In some preferred embodiments, the molar ratio of LiCl to InCl3 is 3:1.

[0037] In some embodiments, the grinding step is specifically: using a high-speed shear mixing device to process the raw material at a rotation speed of 10,000-20,000 rpm for 1-10 minutes.

[0038] This invention uses high-speed shear mixing instead of traditional manual or ball milling, shortening mixing time to 1-10 minutes and significantly improving efficiency. Specifically, the intense shear force generated by high-speed shear mixing can break down raw material agglomerates in a very short time, achieving uniform molecular-level dispersion.

[0039] In some preferred embodiments, the rotation speed is 15000 rpm and the time is 5 minutes.

[0040] In some embodiments, the first heating rate is 2-5°C / min, the second heating rate is 3-5°C / min, and the third cooling rate is 5-10°C / min.

[0041] In some embodiments, the first time is 2-4 hours, and the second time is 8-10 hours.

[0042] In some preferred embodiments, the first temperature is 250° C., and the first time is 1 hour; the second temperature is 350° C., and the second time is 9 hours.

[0043] In some embodiments, the mixed powder is placed in an alumina or quartz crucible, sealed with a high-temperature sealant, and then placed in a muffle furnace for sintering.

[0044] In some embodiments, the inert gas is one or more of argon, helium, neon, and nitrogen, with a flow rate of 10-50 mL / min and a purity of ≥99%.

[0045] The embodiment of the present invention introduces dynamic inert gas atmosphere control (such as argon flow rate of 10-50 mL / min) to reduce the generation of impurities during the sintering process.

[0046] An embodiment of the present invention provides a halide solid electrolyte, which is prepared using the above-mentioned preparation method.

[0047] In some embodiments, the halide solid electrolyte has a D50 particle size of ≤2 μm.

[0048] The smaller the particle size of the electrolyte, the more complete the contact area during use and the higher the ion transmission efficiency.

[0049] In some embodiments, the halide solid electrolyte has an ionic conductivity of 2.1-2.5 mS / cm at room temperature.

[0050] An embodiment of the present invention provides a solid-state battery, comprising a positive electrode, a negative electrode, and the above-mentioned halide solid electrolyte disposed between the positive electrode and the negative electrode.

[0051] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them, and are intended only to illustrate the present invention and in no way limit the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0052] Example 1

[0053] The preparation method of Li3InCl6 halide solid electrolyte material has the following specific steps:

[0054] In a glove box, 3.65 g of LiCl and 6.35 g of InCl3 were weighed and mixed at high speed (15,000 rpm for 5 minutes) to obtain a mixed powder. The mixed powder was transferred to an alumina crucible and sealed with a high-temperature sealant. The sealed crucible was placed in a muffle furnace and gradient sintered in a nitrogen environment (nitrogen flow rate 30 mL / min) (first heating rate of 2°C / min, first temperature of 250°C, first time of 1 h + second heating rate of 4°C / min, second temperature of 350°C, second time of 9 h). After sintering, the mixture was cooled to room temperature at a rate of 5°C / min to obtain a halide solid electrolyte sample. The sample was collected and fully ground in a glove box and sieved using a sieve with an aperture of 80 mesh to obtain a Li3InCl6 halide solid electrolyte. The obtained halide solid electrolyte had an ionic conductivity of 2.3 mS / cm and D50 = 1.8 μm.

[0055] Example 2

[0056] The preparation method of Li3InCl6 halide solid electrolyte material has the following specific steps:

[0057] In a glove box, 365 g of LiCl and 635 g of InCl3 were weighed and mixed at high speed (15,000 rpm for 10 minutes) to obtain a mixed powder. The mixed powder was transferred to an alumina crucible and sealed with a high-temperature sealant. The sealed crucible was placed in a muffle furnace and gradient sintered in a nitrogen environment (nitrogen flow rate 50 mL / min) (first heating rate of 2°C / min, first temperature of 250°C, first time of 2h + second heating rate of 4°C / min, second temperature of 350°C, second time of 10h). After sintering, the mixture was cooled to room temperature at a rate of 10°C / min to obtain a halide solid electrolyte sample. The sample was collected and fully ground in a glove box and sieved using a sieve with an aperture of 80 mesh to obtain a Li3InCl6 halide solid electrolyte. The obtained halide solid electrolyte had an ionic conductivity of 2.5 mS / cm and D50 = 2.0 μm.

[0058] Comparative Example 1

[0059] The preparation method of Li3InCl6 solid electrolyte material has the following specific steps:

[0060] In the glove box, 3.65g LiCl and 6.35g InCl3 were weighed respectively, and the raw materials of the above various proportions were poured into a ball mill jar, using 10mm zirconia balls and a ball-to-material ratio of 40:1; the sealed ball mill jar was transferred to a ball mill, the speed was set to 600rpm, and the ball milling time was 40h; after the ball milling, the balls were separated, and the separated materials were transferred to a muffle furnace for annealing at 500℃ for 5h for recrystallization. After sintering, the halide solid electrolyte sample was collected and fully ground in the glove box, and sieved using a sieve with an aperture of 80 mesh to obtain Li3InCl6 halide solid electrolyte. The obtained halide solid electrolyte had an ionic conductivity of 1.6mS / cm and D50=3.3μm.

[0061] Comparative Example 2

[0062] The preparation method of Li3InCl6 solid electrolyte material has the following specific steps:

[0063] 3.65g of LiCl and 6.35g of InCl3 were dissolved in 100mL of 20% hydrochloric acid solution. The resulting solution was then transferred to a vacuum flask, sealed, placed in an ultrasonic device, and heated in an oil bath at 100°C for 8 hours at a rate of 5°C / min, maintaining a negative pressure of 0.1 MPa. After heating, transparent flaky crystals precipitated, representing a lithium-indium chloride halide electrolyte hydrate solid. The collected hydrate solid was then transferred to a vacuum oven for drying and dehydration at 80°C for 10 hours. The sample was then collected and thoroughly ground in a glove box and sieved using an 80-mesh sieve to obtain a Li3InCl6 halide solid electrolyte sample with an ionic conductivity of 1.3mS / cm and a D50 of 8.6μm.

[0064] The halide solid electrolyte powders prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were made into solid electrolyte sheets and subjected to electrochemical impedance spectroscopy (EIS) testing. The EIS testing showed that the ionic conductivities of the solid electrolyte sheets obtained in Examples 1 and 2 at room temperature were 2.3 mS / cm and 2.5×10 -3 The ionic conductivities of Comparative Example 1 and Comparative Example 2 were 1.6 mS / cm and 1.3 mS / cm, respectively.

[0065] like Figure 1-3 As shown, scanning electron microscope scanning tests were performed on the halide solid electrolytes obtained in Example 1, Comparative Example 1, and Comparative Example 2. As can be seen from the figure, the microscopic morphology of the halide solid electrolyte powder prepared in this embodiment is basically consistent with that of the powder prepared by traditional ball milling, and the sintered particles are small and have good crystallinity.

[0066] The Li3InCl6 halide solid electrolyte and mixed powder prepared in Example 1 were subjected to X-ray diffraction at a diffraction angle of 10-80°. The XRD results are as follows: Figure 4 As shown in the figure, the halide solid electrolyte sample is a mixture of two raw materials, and the XRD of the phase after low-temperature sintering is consistent with the standard card characteristic peak of Li3InCl6 solid electrolyte.

[0067] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a halide solid electrolyte, characterized in that: The preparation method comprises the following steps: According to Li x InCl y The raw materials are mixed and ground in a molar ratio according to the chemical formula to obtain a mixed powder, wherein 2.5<x<3.5, 5.5<y<6.5; The mixed powder is pressed into a tablet and placed in an inert gas, heated to a first temperature at a first heating rate and then kept at that temperature for a first time, then heated to a second temperature at a second heating rate and then kept at that temperature for a second time, and then cooled to room temperature at a third cooling rate to obtain the halide solid electrolyte; Wherein, the first temperature is 200-250°C, and the second temperature is 300-400°C.

2. The method for preparing a halide solid electrolyte according to claim 1, wherein: The raw materials include LiCl and InCl3, and the molar ratio of LiCl to InCl3 is (2.5-3.5):

1.

3. The method for preparing a halide solid electrolyte according to claim 1, wherein: The grinding step specifically comprises: using a high-speed shear mixing device to process the mixed raw materials at a rotation speed of 10,000-20,000 rpm for 1-10 minutes.

4. The method for preparing a halide solid electrolyte according to claim 1, wherein: The first heating rate is 2-5°C / min, the second heating rate is 3-5°C / min, and the third cooling rate is 5-10°C / min.

5. The method for preparing a halide solid electrolyte according to claim 1, wherein: The first time is 2-4 hours, and the second time is 8-10 hours.

6. The method for preparing a halide solid electrolyte according to claim 1, wherein: The inert gas is one or more of argon, helium, neon, and nitrogen, with a flow rate of 10-50 mL / min and a purity of ≥99%.

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

8. The halide solid electrolyte according to claim 7, characterized in that The D50 particle size of the halide solid electrolyte is ≤2 μm.

9. The halide solid electrolyte according to claim 7, characterized in that The ionic conductivity of the halide solid electrolyte at room temperature is 2.1-2.5 mS / cm.

10. A solid-state battery, characterized in that: The solid-state battery includes a positive electrode, a negative electrode, and a halide solid electrolyte according to any one of claims 7 to 9 disposed between the positive electrode and the negative electrode.

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