A halide solid-state electrolyte and a preparation method and application thereof

Abstract

The application relates to a halide solid-state electrolyte as well as a preparation method and application thereof, and relates to the technical field of new energy materials. 1.5 Zr 0.5 M 0.5 Cl5O 0.5 , wherein M is Ta or Nb; and the inner core is a crystalline halide electrolyte with a chemical general formula of Li 2.5 Y 0.5 Zr 0.5 Cl 6‑4x F 4x , wherein 0.05<=x<=1.45. The halide solid-state electrolyte has high ion conductivity, high oxidation potential, high mechanical performance, good chemical stability with sulfides and high air stability.

Description

Technical Field

[0001] This application relates to the field of new energy materials technology, specifically to a halide solid electrolyte, its preparation method, and its application in solid-state batteries. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the safety of power batteries has become increasingly prominent. Traditional lithium-ion batteries mainly rely on flammable organic solvents as electrolytes, posing significant safety hazards under conditions such as thermal runaway. In contrast, solid-state batteries, using non-flammable solid electrolytes, can fundamentally solve safety issues and offer advantages such as high energy density and flexible structural design, making them the recognized next-generation battery technology.

[0003] To achieve the industrialization of solid-state batteries, the core lies in developing high-performance solid-state electrolytes. Among inorganic solid-state electrolyte materials, the mainstream systems are currently divided into three categories: oxides, sulfides, and halides, each with its own advantages and disadvantages.

[0004] Although oxide electrolytes have high oxidation potential and exhibit good chemical stability to high-voltage ternary cathode materials, their ionic conductivity is generally low, and their materials are rigid and have poor ductility, resulting in high contact resistance with the cathode material, which limits battery performance.

[0005] Sulfide electrolytes typically have high ionic conductivity and good ductility, enabling them to form dense physical contact with the positive and negative electrodes through cold pressing. However, they have the following problems: low oxidation potential, usually <3V, which makes them prone to decomposition and side reactions under high voltage, affecting battery cycle performance; poor air stability, easily reacting with moisture to generate toxic H2S gas when exposed to air, leading to a severe decline in material performance and stringent requirements for the production environment.

[0006] Halogen electrolytes, such as Li2ZrCl6 (Zr-based) and Li3InCl6 (In-based), are emerging electrolyte materials that have attracted attention recently. Their oxidation potentials are higher than those of sulfides, theoretically making them better suited for high-voltage cathode materials. However, they suffer from the following problems: poor air stability, readily reacting with moisture to generate HCl gas upon exposure to air, leading to a significant decline in material performance; low ionic conductivity, typically ≤1 mS / cm at room temperature, limiting the rate performance of batteries; higher Young's modulus than sulfides, resulting in greater hardness and poorer mechanical properties, making it difficult to uniformly mix with cathode materials to form a dense cathode coating, thus affecting the high-rate and long-cycle performance of batteries; and poor contact chemical stability with sulfide electrolytes, easily leading to side reactions, severely restricting their application in composite electrolytes.

[0007] Therefore, developing a solid electrolyte material that combines high ionic conductivity, high air stability, and excellent mechanical properties is a pressing technical challenge that needs to be addressed. Summary of the Invention

[0008] In view of this, the purpose of this application is to provide a halide solid electrolyte, a method for preparing the same, and its application in solid-state batteries, so as to solve at least one of the above-mentioned technical problems.

[0009] In a first aspect, this application provides a halide solid electrolyte, comprising a shell and a core; the shell is an amorphous halide electrolyte with the general chemical formula Li. 1.5 Zr 0.5 M 0.5 Cl5O 0.5 Where M is Ta or Nb; the core is a crystalline halide electrolyte with the general chemical formula Li. 2.5 Y 0.5 Zr 0.5 Cl 6-4x F 4x , where 0.05≤x≤1.45.

[0010] In conjunction with the first aspect, in some optional implementations, the value of x is in the range of 0.05 ≤ x ≤ 0.5.

[0011] In conjunction with the first aspect, in some alternative implementations, the mass ratio of the shell to the core is y%, where 1 ≤ y ≤ 20.

[0012] In conjunction with the first aspect, in some optional implementations, the value of y is in the range of 5 ≤ y ≤ 10.

[0013] Secondly, this application provides a method for preparing a halide solid electrolyte in any embodiment of the first aspect described above. This method is carried out under an inert atmosphere and includes the following steps: [The method is described in the context of Li...] 1.5 Zr 0.5 M 0.5 Cl5O 0.5 Based on the stoichiometric ratio of each element, Li₂O, MCl₅, LiCl, and ZrCl₄ were mixed and ball-milled to obtain coarse amorphous halide electrolyte powder; the coarse amorphous halide electrolyte powder was then refined to obtain fine amorphous halide electrolyte powder; according to Li… 2.5 Y 0.5 Zr 0.5 Cl 6-4x F 4xThe stoichiometric ratios of each element in the mixture are determined as follows: LiCl, YCl3, ZrF4, and ZrCl4 are powdered and mixed to obtain a halide precursor; the halide precursor is heat-treated and cooled to obtain a coarse crystalline halide electrolyte powder; the coarse crystalline halide electrolyte powder is refined to obtain a fine crystalline halide electrolyte powder; the amorphous halide electrolyte powder and the fine crystalline halide electrolyte powder are ball-milled and mixed at a preset mass ratio of y% to obtain the target electrolyte precursor; the target electrolyte precursor is heat-treated and cooled to obtain a solid halide electrolyte.

[0014] In conjunction with the second aspect, in some optional embodiments, in the step of preparing amorphous halide electrolyte coarse powder by ball milling after mixing Li2O, MCl5, LiCl and ZrCl4, a vertical planetary ball mill is used, the ball-to-material ratio is 20:1-40:1, the ball milling speed is 450-700 r / min, and the ball milling time is 30-100 h.

[0015] In conjunction with the second aspect, in some optional embodiments, in the step of refining the coarse amorphous halide electrolyte powder to obtain fine amorphous halide electrolyte powder, a gyratory pulverizer is used, with a processing capacity of 80-120g per pulverization, a pulverization speed of 25000r / min, a pulverization time of 20-30s per pulverization, and a pulverization frequency of 8-15 times.

[0016] In conjunction with the second aspect, in some optional embodiments, in the step of grinding and mixing LiCl, YCl3, ZrF4 and ZrCl4 to obtain the halide precursor, a gyratory pulverizer is used, the grinding speed is 25000 r / min, the grinding time is 20-30 s per grinding, and the grinding number is 6-12 times.

[0017] In conjunction with the second aspect, in some optional embodiments, the halide precursor is heat-treated and cooled to obtain crystalline halide electrolyte coarse powder, including: sealing the halide precursor in a tube and then transferring it to a muffle furnace for heat treatment at a temperature of 400-600℃, a heating rate of 1-2℃ / min, and a holding time of 2-4h; transferring the product after the holding time to a -30℃ oven for rapid cooling to obtain crystalline halide electrolyte coarse powder.

[0018] In conjunction with the second aspect, in some optional embodiments, in the step of refining the coarse crystalline halide electrolyte powder to obtain fine crystalline halide electrolyte powder, a gyratory pulverizer is used, with a processing capacity of 100-150g per pulverization, a pulverization speed of 25000r / min, a pulverization time of 20-30s per pulverization, and a pulverization frequency of 4-8 times.

[0019] In conjunction with the second aspect, in some optional embodiments, in the step of ball milling and mixing amorphous halide electrolyte fine powder and crystalline halide electrolyte fine powder to obtain the target electrolyte precursor, an all-around planetary ball mill is used, the ball-to-material ratio is 10:1-15:1, the ball milling speed is 150-200 r / min, the tumbling speed is 1-4 r / min, and the ball milling time is 2-6 h.

[0020] In conjunction with the second aspect, in some optional embodiments, the target electrolyte precursor is subjected to heat treatment and cooled to obtain a halide solid electrolyte, including: placing the target electrolyte precursor into a sintering tank, sealing it, and then transferring it to a muffle furnace for heat treatment at a temperature of 150-200°C, a heating rate of 1-2°C / min, and a holding time of 2-8h; and naturally cooling the product after the holding time to obtain the halide solid electrolyte.

[0021] Thirdly, this application provides a solid-state battery, which includes a halide solid electrolyte in any of the embodiments of the first aspect above or a halide solid electrolyte prepared by the method in any of the embodiments of the second aspect above.

[0022] Based on the above technical solution, the halide solid electrolyte, its preparation method, and its application in solid-state batteries provided in this application have the following beneficial effects:

[0023] (1) High ionic conductivity: Using amorphous halide electrolyte as shell material can effectively ensure that the target electrolyte has high ionic conductivity (≥3mS / cm), which is beneficial to achieving high-rate charge and discharge performance of the battery;

[0024] (2) Higher oxidation potential: By using crystalline halide electrolyte with F element doping as the core material, the oxidation potential of the target electrolyte (≥4.5V) can be effectively increased, the side reaction between the target electrolyte and the cathode material can be reduced, the capacity of the cathode active material can be improved, and the energy density and cycle stability of the battery can be improved.

[0025] (3) High mechanical properties: On the one hand, it is easy to mix with the positive electrode to form a dense coating layer, and on the other hand, it has good resistance to deformation, thereby improving the high rate and long cycle performance of the battery;

[0026] (4) Good chemical stability with sulfides: In particular, the target electrolyte has no side reactions when it comes into contact with or is mixed with the currently mainstream silver-germanium sulfide electrolyte, which greatly improves the battery cycle stability.

[0027] (5) Higher air stability: By introducing shell materials with better air stability, the air stability of the target electrolyte can be effectively improved, thereby reducing the environmental requirements and manufacturing costs of subsequent electrode preparation and making it easier to achieve large-scale mass production. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic flowchart illustrating a method for preparing a halide solid electrolyte according to an embodiment of this application. Detailed Implementation

[0030] The present application will be further described below with reference to specific embodiments, but the scope of protection of the present application is not limited to the following embodiments.

[0031] This application provides a halide solid electrolyte comprising a shell and a core.

[0032] The outer shell is an amorphous halide electrolyte with the general chemical formula Li. 1.5 Zr 0.5 M 0.5 Cl5O 0.5 (Hereinafter referred to as LZMCO), where M is Ta or Nb. Preferably, M is Ta, and the chemical formula is Li. 1.5 Zr 0.5 Ta 0.5 Cl5O 0.5 (Hereinafter referred to as LZTCO), it has a high room temperature ionic conductivity of about 4 mS / cm.

[0033] The core is a crystalline halide electrolyte with the general chemical formula Li. 2.5 Y 0.5 Zr 0.5 Cl 6-4x F 4x Where 0.05 ≤ x ≤ 1.45. Preferably, the range of x is 0.05 ≤ x ≤ 0.5, and the value of x can be 0.1, 0.2, 0.3, 0.4, or 0.5. Where x = 0.2, the chemical formula is Li. 2.5 Y 0.5 Zr 0.5 Cl 5.2 F 0.8Its room temperature ionic conductivity is up to about 1.5 mS / cm; when x=0.05 or x=0.5, the purpose of this invention can also be achieved, and a good balance is achieved between ionic conductivity and oxidation potential.

[0034] The overall chemical formula of the target electrolyte can be represented as y%·LZTCO@Li 2.5 Y 0.5 Zr 0.5 Cl 6-4x F 4x The mass ratio of the outer shell to the core is y%, where 1 ≤ y ≤ 20. Preferably, the value of y is in the range of 5 ≤ y ≤ 10, and the value of y can be 5, 6, 7, 8, 8.5, 9, or 10. Specifically, in the following embodiments, Embodiment 1 verified y = 5.0, Embodiment 3 verified y = 6.0, Embodiment 5 verified y = 7.0, Embodiment 7 verified y = 8.0, Embodiment 8 verified y = 8.5, Embodiment 9 verified y = 9.0, and Embodiment 11 verified y = 10.0. The above-mentioned single-point preferred values ​​all exhibit excellent comprehensive performance.

[0035] This halide solid electrolyte simultaneously possesses high ionic conductivity, high oxidation potential, high mechanical properties, good chemical stability with sulfides, and high air stability, as detailed below:

[0036] (1) High ionic conductivity: Using amorphous halide electrolyte as shell material can effectively ensure that the target electrolyte has high ionic conductivity (≥3mS / cm), which is beneficial to achieving high-rate charge and discharge performance of the battery.

[0037] (2) Higher oxidation potential: The core adopts a crystalline halide electrolyte doped with F element, which can effectively increase the oxidation potential of the target electrolyte (≥4.5V), suppress the side reaction between it and the cathode material, and enhance the contact stability; the shell adopts an amorphous halide electrolyte with a lower Young's modulus, which utilizes its grain boundary-free characteristics to achieve close solid-solid contact with the high-performance cathode and uniform lithium-ion conduction, further improving the interface stability between the target electrolyte and the cathode active material, thereby further improving the battery performance.

[0038] (3) Higher mechanical properties: Amorphous halide electrolytes have advantages such as being softer, easier to manufacture, having lower grain boundaries, a wider range of compositional variations, and isotropic ion conduction. The target electrolyte using it as the shell material also has higher processability and is easier to mix evenly with the positive electrode, forming a good coating layer on the surface of the positive electrode particles, which is beneficial to improving battery performance. At the same time, the core uses crystalline halide electrolytes with higher resistance to deformation, which can ensure that the target electrolyte is not prone to cracking or breaking during battery cycling, effectively improving the long-cycle stability of the battery.

[0039] (4) Good chemical stability with sulfides: Doping a certain concentration of oxygen into halide electrolytes (especially Zr-based) can effectively reduce the interfacial reaction energy with sulfides without impairing ionic conductivity. This doping helps to form a dense, low-resistivity Li3PO4 enriched layer at the interface, which not only avoids side reactions when the two come into contact or mix, but also significantly improves the electrochemical performance and cycle stability of the full cell.

[0040] (5) High air stability: The use of an amorphous halide electrolyte with excellent air stability as the shell material enhances the air stability of the target electrolyte. Tests show that the electrolyte retains ≥95% of its ionic conductivity even after being exposed in a conventional dew point drying room at -40℃ for 4 hours. This characteristic effectively reduces the stringent requirements on the electrode preparation environment, allowing the cathode to be prepared in a conventional dew point drying room using either dry or wet processes, thereby significantly reducing manufacturing costs and facilitating large-scale mass production.

[0041] Based on the above-mentioned halide solid electrolyte, the preparation method of the halide solid electrolyte will be described in detail below.

[0042] like Figure 1 As shown, a method for preparing a halide solid electrolyte is carried out under an inert atmosphere and includes the following steps:

[0043] S1, according to Li 1.5 Zr 0.5 M 0.5 Cl5O 0.5 The stoichiometric ratio of each element was determined by mixing Li₂O, MCl₅, LiCl, and ZrCl₄ and then ball milling to obtain amorphous halide electrolyte coarse powder.

[0044] In this step, ball milling preparation is achieved using a vertical planetary ball mill. During operation, first press Li... 1.5 Zr 0.5 M 0.5 Cl5O 0.5 The stoichiometric ratios of each element were measured for Li₂O, MCl₅, LiCl, and ZrCl₄, and then placed in a ball mill jar, which was sealed. Next, the ball mill jar was fixed onto a vertical planetary ball mill, the mill parameters were set, and ball milling began. After ball milling, the resulting product was a uniform, amorphous halide electrolyte coarse powder.

[0045] The ball mill parameters are set as follows: ball-to-material ratio of 20:1-40:1; ball milling speed of 450-700 r / min; and ball milling time of 30-100 h.

[0046] S2. The coarse powder of amorphous halide electrolyte is refined to obtain fine powder of amorphous halide electrolyte.

[0047] In this step, the refining process is achieved using a gyratory pulverizer. The gyratory pulverizer model can be DFY-200, with the following parameters: a processing capacity of 80-120g per pass; a pulverizing speed of 25000 r / min; a pulverizing time of 20-30s per pass; and 8-15 passes. After refining, the resulting product is a uniform amorphous halide electrolyte fine powder with a D90 ≈ 1μm.

[0048] S3, according to Li 2.5 Y 0.5 Zr 0.5 Cl 6-4x F 4x The stoichiometric ratio of each element was determined by grinding and mixing LiCl, YCl3, ZrF4, and ZrCl4 to obtain a halide precursor.

[0049] In this step, the grinding and mixing of materials is achieved using a vibrating pulverizer. During operation, first press Li... 2.5 Y 0.5 Zr 0.5 Cl 6-4x F 4x Weigh out the stoichiometric ratios of LiCl, YCl3, ZrF4, and ZrCl4, and then place them into a gyratory pulverizer for grinding and mixing. The gyratory pulverizer model can be DFY-200, with the following parameters set: grinding speed of 25000 r / min; grinding time of 20-30 s per cycle; and 6-12 grinding cycles.

[0050] S4. The halide precursor is heat-treated and cooled to obtain crystalline halide electrolyte coarse powder.

[0051] Specifically, the halide precursor is first sealed in a tube and then transferred to a muffle furnace for low-temperature heat treatment. The heat treatment parameters are set as follows: heat treatment temperature 400-600℃; heating rate 1-2℃ / min; holding time 2-4h. After holding, the product is transferred to a -30℃ oven for rapid cooling. Rapid cooling introduces high-density dispersed defects into the crystal structure. These defects promote enhanced interactions between dislocations and form diffusely distributed defects between dislocations and other crystal defects, effectively hindering dislocation movement and improving the material's resistance to deformation. After cooling, crystalline halide electrolyte coarse powder is obtained.

[0052] S5. The coarse powder of crystalline halide electrolyte is refined to obtain fine powder of crystalline halide electrolyte.

[0053] In this step, the grinding and mixing are achieved using a gyratory pulverizer. The gyratory pulverizer model can be DFY-200, with the following parameters: a processing capacity of 100-150g per grinding cycle; a grinding speed of 25000 r / min; a grinding time of 20-30s per cycle; and 4-8 grinding cycles. After refining, the resulting product is a uniform crystalline halide electrolyte fine powder with a D50 ≈ 5μm.

[0054] S6. The amorphous halide electrolyte fine powder and the crystalline halide electrolyte fine powder are ball-milled and mixed according to the preset mass ratio y% to obtain the target electrolyte precursor.

[0055] In this step, ball milling preparation is achieved using an omnidirectional planetary ball mill. During operation, amorphous halide electrolyte fine powder and crystalline halide electrolyte fine powder are weighed out according to a shell-to-core mass ratio of y%, then placed into the ball mill jar and sealed. Next, the ball mill jar is fixed on the omnidirectional planetary ball mill, the mill parameters are set, and ball milling begins. Unlike conventional vertical planetary ball mills, the omnidirectional planetary ball mill allows the planetary discs to rotate continuously 360° or work at any angle while the planetary jars are working, ensuring that the materials fully participate in grinding and mixing, thereby reducing material settling and achieving thorough mixing. After ball milling, the resulting product is the target electrolyte precursor.

[0056] The ball mill parameters are set as follows: ball-to-material ratio of 10:1-15:1; ball milling speed of 150-200 r / min; tumbling speed of 1-4 r / min; and ball milling time of 2-6 h.

[0057] S7. The target electrolyte precursor is subjected to heat treatment and cooled to obtain a halide solid electrolyte.

[0058] Specifically, the target electrolyte precursor is first placed in a sintering tank and sealed, then transferred to a muffle furnace for low-temperature heat treatment. The heat treatment parameters are set as follows: heat treatment temperature of 150-200℃, heating rate of 1-2℃ / min, and holding time of 2-8h. After the holding time is completed, the product is allowed to cool naturally to obtain the halide solid electrolyte.

[0059] Among them, low-temperature heat treatment can: on the one hand, further enhance the structural stability of the amorphous halide electrolyte in the shell, thereby improving the performance of the target electrolyte; on the other hand, make the surface coating more dense and uniform, improving the performance consistency of the target electrolyte.

[0060] Next, the technical effects of this application will be illustrated through several embodiments and comparative examples. It should be understood that the following embodiments focus on verifying the performance of x=0.2 and different y values, but the scope of protection of this application also covers schemes with x taking other single-point preferred values ​​such as 0.05, 0.1, 0.3, 0.5, etc., whose technical effects are comparable to the following embodiments and can achieve the inventive purpose of this application.

[0061] Example 1

[0062] This embodiment provides a halide solid electrolyte, the overall chemical formula of which is 5.0%·LZTCO@Li 2.5 Y 0.5 Z r0.5 Cl 5.2 F 0.8 (M=Ta, x=0.2, y=5), the specific preparation process under an argon atmosphere is as follows:

[0063] S1. Weigh out 0.5 mol Li2O, 0.5 mol TaCl5, 0.5 mol LiCl and 0.5 mol ZrCl4 according to the molar ratio and put them into a ball mill jar. The ball-to-material ratio is controlled at 20:1. After sealing, ball milling is carried out using a vertical planetary ball mill. The ball mill parameters are set as follows: ball milling speed is 640 r / min and ball milling time is 80 h. After ball milling, amorphous halide electrolyte coarse powder is obtained.

[0064] S2. The coarse powder of amorphous halide electrolyte was refined using a DFY-200 swing pulverizer. The pulverizer parameters were set as follows: 100g per batch, 25000r / min grinding speed, 30s grinding time per batch, and 13 grinding cycles. After the refinement process, fine powder of amorphous halide electrolyte with D90≈1μm was obtained.

[0065] S3. Weigh out 2.5 mol LiCl, 0.5 mol YCl3, 0.3 mol ZrCl4 and 0.20 mol ZrF4 according to the molar ratio and put them into a DFY-200 swing-type pulverizer for grinding and mixing. The pulverizer parameters are set as follows: grinding speed 25000 r / min, grinding time 30s per grinding, and grinding times 8 times. After grinding and mixing, the halide precursor is obtained.

[0066] S4. After sealing the halide precursor, transfer it to a muffle furnace for low-temperature heat treatment. The specific parameters are set as follows: heat treatment temperature is 550℃, heating rate is 1℃ / min, and holding time is 3h. After the holding time is completed, immediately transfer it to a -30℃ oven for rapid cooling treatment. After cooling, crystalline halide electrolyte coarse powder is obtained.

[0067] S5. The coarse powder of crystalline halide electrolyte was refined using a DFY-200 swing pulverizer. The pulverizer parameters were set as follows: 100g per batch, 25000r / min grinding speed, 30s grinding time per batch, and 6 grinding cycles. After the refinement process, fine powder of crystalline halide electrolyte with D50≈5μm was obtained.

[0068] S6. Weigh 5g of amorphous halide electrolyte fine powder and 100g of crystalline halide electrolyte fine powder according to a 5.0% ratio and put them into a ball mill jar. The ball-to-material ratio is controlled at 10:1. After sealing, ball milling is carried out using an all-around planetary ball mill. The ball mill parameters are set as follows: ball milling speed is 180r / min; tumbling speed is 2r / min; ball milling time is 4h. After ball milling, the target electrolyte precursor is obtained.

[0069] S7. After sealing the target electrolyte precursor in a sintering tank, transfer it to a muffle furnace for low-temperature heat treatment. The specific parameters are set as follows: heat treatment temperature is 180℃, heating rate is 1℃ / min, and holding time is 6h. After the holding time is completed, the product is allowed to cool naturally to obtain the halide solid electrolyte.

[0070] Example 2-13

[0071] Examples 2-13 only changed the y value, and the preparation process was the same as that of Example 1. Specific information is shown in Table 1.

[0072] Comparative Example 1

[0073] This embodiment provides a method that uses only the LZTCO shell as a control electrolyte, as detailed in Table 1.

[0074] Comparative Example 2

[0075] This embodiment provides a method applicable only to kernel Li 2.5 Y 0.5 Z r0.5 Cl 5.2 F 0.8 For comparison electrolytes, specific information is shown in Table 1.

[0076] Table 1. Electrolyte Composition Information

[0077]

[0078] Performance tests were conducted on Examples 1-13 and Comparative Examples 1 and 2, specifically including ionic conductivity testing, air stability testing, target electrolyte voltage window testing, battery testing, and chemical stability testing with sulfides.

[0079] Ionic conductivity test: Weigh 100mg of electrolyte powder and place it in an insulating sleeve with an inner diameter of 10mm. Press it into shape under a pressure of 300MPa and perform AC impedance spectroscopy to measure the impedance value of the electrolyte material. Then, measure the thickness of the pressurized sheet electrolyte. Based on the sheet impedance value, thickness value, and area, calculate the ionic conductivity of the electrolyte material using the formula σ=d / (R×S), where σ is the ionic conductivity in s / cm; d is the sheet thickness in cm; R is the impedance value in Ω; and S is the sheet area in cm². 2 The test results are shown in Table 2.

[0080] Air stability test: After the ionic conductivity test of the same batch of electrolytes is completed as above, take a 100mg sample of electrolyte powder and place it at a temperature of 25±3℃ and a dew point ≤ The electrolyte was left to stand at 55℃ for 6 hours. After standing, the ionic conductivity of the electrolyte was retested, and the retention rate of ionic conductivity was calculated. If the retention rate of ionic conductivity is ≥95%, it indicates that the electrolyte has high air stability. The test results are shown in Table 2.

[0081] Target electrolyte voltage window test: The target electrolyte and conductive carbon powder were weighed at a weight ratio of 70:30 and ground evenly using an agate mortar. 20 mg of the target electrolyte was then placed in an insulating outer cylinder with a diameter of 10 mm. Conductive carbon powder mixture, 20mg Li 5.4 PS 4.4 Cl 1.6 Electrolytes are layered. They are then pressurized to 360 MPa and molded, followed by... 5.4 PS 4.4 Cl 1.6 A lithium foil is stacked on one side and pressurized to form a solid shape under 100 MPa pressure. Then, stainless steel current collectors are placed above and below the stack, and current collector leads are attached to the current collectors. A linear scanning voltammetry test is performed, with a scanning range of 2... The voltage was 5V, and the scan rate was 0.1mV / s. The oxidation potential of the material is obtained by plotting the tangent line to the oxidation peak of the test curve and intersecting it with the horizontal axis. The test results are shown in Table 2.

[0082] Battery testing: Inside an argon glove box, the target electrolyte and the positive electrode active material Li(Ni) were tested. 0.8 Co 0.1 Mn 0.1 O2 (NCM811) was weighed at a weight ratio of 20:80. The mixture was ground uniformly using an agate mortar, thus preparing the composite cathode material. In an insulating outer cylinder with a diameter of 10 mm, 14 mg of the above composite cathode material and 70 mg of Li were mixed... 5.4 PS4.4 Cl 1.6 The electrolyte is laminated. It is then pressurized at 360 MPa to form the positive electrode and solid electrolyte layer. Next, an aluminum foil is laminated on the positive electrode side, forming a current collector. Then, on the opposite side of the solid electrolyte layer that contacts the positive electrode, an indium sheet with a thickness of 200 μm and a diameter of 10 mm is placed as the negative electrode material. It is then pressurized at 80 MPa to create a laminate consisting of the positive electrode, solid electrolyte layer, and negative electrode. Stainless steel current collectors are then placed on the top and bottom of the laminate, and current collector leads are attached to the current collectors. The assembled solid-state battery is subjected to cycle performance testing under the following conditions: current density of 1C and voltage range of 2.7V. 4.3V (vs. Li / Li) + The test results are shown in Table 2.

[0083] Sulfide chemical stability test: 100 mg of target electrolyte powder and 100 mg of Li5.4PS4.4Cl1.6 sulfide electrolyte powder were weighed and mixed evenly in a mortar. The mixture was then placed in an insulating sleeve with an inner diameter of 10 mm and pressurized at 300 MPa. AC impedance testing was performed continuously at different time intervals while maintaining constant pressure to obtain the impedance values ​​of the electrolyte material at different resting times. Finally, the thickness of the pressurized sheet electrolyte was measured. Based on the sheet impedance, thickness, and area, the ionic conductivity of the electrolyte material at different resting times can be calculated using the formula σ = d / (R × S), where σ is the ionic conductivity (s / cm), d is the sheet thickness (cm), R is the impedance (Ω), and S is the sheet area (cm²). 2 If the ionic conductivity remains essentially unchanged with standing time and the retention rate of ionic conductivity after standing is high, it indicates good chemical stability; if the change is significant and the retention rate of ionic conductivity after standing is low, it indicates that side reactions have occurred and the chemical stability is poor. The test results are shown in Table 3.

[0084] Table 2. Electrolyte performance testing and air stability evaluation

[0085]

[0086] Table 3. Stability evaluation of target electrolyte and sulfide electrolyte

[0087]

[0088] Combining the data in Tables 1, 2, and 3, and examining Examples 1-13, it can be seen that: with increasing coating amount, the ionic conductivity of the target electrolyte first increases and then tends to stabilize, reaching its maximum value at a coating amount of 8.5%. When the coating amount is ≥8.5%, the ionic conductivity of the target electrolyte is basically consistent with that of the amorphous halide electrolyte in the coating layer, indicating that the coating is uniform and dense at this point, fully utilizing the high ionic conductivity advantage of the coating electrolyte. The oxidation potential shows a trend of first stabilizing and then decreasing, starting to decrease significantly when the coating amount is >8.5%. This indicates that excessive coating at this point leads to the amorphous halide electrolyte in the coating layer dominating the performance, while the crystalline halide electrolyte in the core fails, thus causing… The antioxidant properties of the target electrolyte decreased; air stability showed a trend of first increasing and then stabilizing, reaching a peak when the coating amount was 8.5%, meaning that the ionic conductivity retention rate after exposure could reach 95.5%, further demonstrating that the coating amount of 8.5% was effective and could fully utilize the advantage of the high air stability of the amorphous halide electrolyte in the coating layer; battery performance showed a trend of first increasing and then decreasing, reaching its optimum when the coating amount was 8.5%, indicating that the coating effect was optimal at this point, and could fully utilize the advantages of both the coating layer and the core electrolyte; the chemical stability of the target electrolyte and the sulfide electrolyte showed a trend of first increasing and then stabilizing, with better performance when the coating amount was ≥8.5%, and there were basically no side reactions between the two. In addition, Examples 1 (y=5) and 11 (y=10) respectively verified the technical effect of the endpoints of the preferred y value range, and Examples 1-11 as a whole verified the excellent performance when y took the single-point preferred values ​​of 5, 6, 7, 8, 9, and 10.

[0089] Comparative Example 1 shows that while the single-layer amorphous halide electrolyte exhibits high ionic conductivity, air stability, and chemical stability with sulfide electrolytes, its oxidation potential is low, thus affecting battery performance. Comparative Example 2 shows that while the single-core crystalline halide electrolyte has a high oxidation potential, its ionic conductivity is low, its air stability is poor, and its chemical stability with sulfide electrolytes is also low, thus affecting battery performance. This comprehensive comparison further demonstrates the advanced nature of the present invention.

[0090] In summary, Example 8 showed the best performance. At this time, the target electrolyte had the highest ionic conductivity of 4.01 mS / cm at room temperature, the oxidation potential was still relatively high at 4.55 V, the battery performance was the best (93.8% initial efficiency, 210.8 mAh / g discharge capacity in the first cycle, and 98.5% capacity retention after 200 cycles), the best air stability (95.5% ionic conductivity retention after exposure), and the highest level of chemical stability with sulfide electrolytes (100% ionic conductivity retention after standing for 8 hours).

[0091] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in this application, and these should all be included within the scope of protection of this application.

Claims

1. A halide solid electrolyte, characterized in that, It includes an outer shell and a core; the outer shell is an amorphous halide electrolyte with the general chemical formula Li. 1.5 Zr 0.5 M 0.5 Cl5O 0.5 Where M is Ta or Nb; the core is a crystalline halide electrolyte with the general chemical formula Li. 2.5 Y 0.5 Zr 0.5 Cl 6-4x F 4x , where 0.05≤x≤1.

45.

2. The halide solid electrolyte according to claim 1, characterized in that, The value of x is in the range of 0.05 ≤ x ≤ 0.

5.

3. The halide solid electrolyte according to claim 1, characterized in that, The mass ratio of the outer shell to the core is y:100, where 1≤y≤20.

4. The halide solid electrolyte according to claim 3, characterized in that, The value of y is in the range of 5 ≤ y ≤ 10.

5. A method for preparing a halide solid electrolyte according to any one of claims 1-4, characterized in that, The method is carried out under an inert atmosphere and includes the following steps: According to Li 1.5 Zr 0.5 M 0.5 Cl5O 0.5 The stoichiometric ratio of each element in the mixture was determined by ball milling Li₂O, MCl₅, LiCl, and ZrCl₄ to obtain amorphous halide electrolyte coarse powder. The coarse powder of the amorphous halide electrolyte is refined to obtain fine powder of the amorphous halide electrolyte; According to Li 2.5 Y 0.5 Zr 0.5 Cl 6-4x F 4x The stoichiometric ratio of each element in the mixture was determined by grinding and mixing LiCl, YCl3, ZrF4 and ZrCl4 to obtain a halide precursor. The halide precursor was subjected to heat treatment and then cooled to obtain crystalline halide electrolyte coarse powder. The coarse crystalline halide electrolyte powder is refined to obtain fine crystalline halide electrolyte powder; The amorphous halide electrolyte fine powder and the crystalline halide electrolyte fine powder are ball-milled and mixed at a mass ratio of y:100 to obtain the target electrolyte precursor, wherein 1≤y≤20; The target electrolyte precursor is subjected to heat treatment and then cooled to obtain the halide solid electrolyte.

6. The preparation method according to claim 5, characterized in that, In the step of preparing amorphous halide electrolyte coarse powder by ball milling after mixing Li2O, MCl5, LiCl and ZrCl4, a vertical planetary ball mill is used, the ball-to-material ratio is 20:1-40:1, the ball milling speed is 450-700 r / min, and the ball milling time is 30-100 h.

7. The preparation method according to claim 5, characterized in that, In the step of refining the coarse amorphous halide electrolyte powder to obtain fine amorphous halide electrolyte powder, a gyratory pulverizer is used, with a processing capacity of 80-120g per pulverization, a pulverization speed of 25000r / min, a pulverization time of 20-30s per pulverization, and a pulverization frequency of 8-15 times.

8. The preparation method according to claim 5, characterized in that, In the step of grinding and mixing LiCl, YCl3, ZrF4 and ZrCl4 to obtain the halide precursor, a gyratory pulverizer is used, the grinding speed is 25000 r / min, the grinding time is 20-30s per grinding, and the grinding is repeated 6-12 times.

9. The preparation method according to claim 5, characterized in that, The step of heat-treating the halide precursor and cooling it to obtain crystalline halide electrolyte coarse powder includes: The halide precursor is sealed in a tube and then transferred to a muffle furnace for heat treatment. The heat treatment temperature is 400-600℃, the heating rate is 1-2℃ / min, and the holding time is 2-4h. After the heat preservation is completed, the product is transferred to a -30℃ oven for rapid cooling to obtain the crystalline halide electrolyte coarse powder.

10. The preparation method according to claim 5, characterized in that, In the step of refining the coarse crystalline halide electrolyte powder to obtain fine crystalline halide electrolyte powder, a swing-type pulverizer is used, with a processing capacity of 100-150g per pulverization, a pulverization speed of 25000r / min, a pulverization time of 20-30s per pulverization, and a pulverization frequency of 4-8 times.

11. The preparation method according to claim 5, characterized in that, In the step of ball milling and mixing the amorphous halide electrolyte fine powder and the crystalline halide electrolyte fine powder to obtain the target electrolyte precursor, an all-around planetary ball mill is used, the ball-to-material ratio is 10:1-15:1, the ball milling speed is 150-200 r / min, the tumbling speed is 1-4 r / min, and the ball milling time is 2-6 h.

12. The preparation method according to claim 5, characterized in that, The step of heat-treating the target electrolyte precursor and cooling it to obtain the halide solid electrolyte includes: The target electrolyte precursor is placed in a sintering tank, sealed, and then transferred to a muffle furnace for heat treatment. The heat treatment temperature is 150-200℃, the heating rate is 1-2℃ / min, and the holding time is 2-8h. The product after the heat preservation is completed is naturally cooled to obtain the halide solid electrolyte.

13. A solid-state battery, characterized in that, Includes the halide solid electrolyte as described in any one of claims 1-4 or the halide solid electrolyte prepared by the method described in any one of claims 5-12.

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