A high-conductivity sulfide solid-state electrolyte, a preparation method and applications thereof

Abstract

The application discloses a high-ionic-conductivity sulfide solid electrolyte, a preparation method and application thereof, and relates to the following steps: performing pressure treatment on LPSCI raw material powder, maintaining a certain pressure and pressure time, and obtaining the high-ionic-conductivity sulfide solid electrolyte. The high-ionic-conductivity sulfide solid electrolyte is prepared through high pressure, the improved dislocation density and reduced interface impedance in the high-ionic-conductivity sulfide solid electrolyte can be maintained at normal temperature and normal pressure, and the preparation process does not need heating and pressure transmission substances, and the method is simple, safe and reliable.

Description

Technical Field

[0001] This invention belongs to the field of solid-state lithium batteries, and relates to a high-conductivity sulfide solid electrolyte, its preparation method, and its application. Background Technology

[0002] Lithium batteries stand out among many energy storage devices due to their advantages such as long lifespan, high energy density, and no memory effect, and are widely used in portable electronic devices and new energy vehicles.

[0003] The use of organic electrolytes poses significant safety risks to lithium batteries, such as leakage, fire, and explosion, severely limiting their practical application. Therefore, there is an urgent need to develop battery systems with higher energy density and safety properties. All-solid-state lithium batteries, with their advantages of high safety, high energy density, convenient packaging, and a wide operating temperature range, have become one of the most promising new battery systems. The solid electrolyte is the core component of an all-solid-state battery, playing a decisive role in its overall performance. Sulfide solid electrolytes, particularly those with high ionic conductivity and excellent mechanical ductility, have become a focus of research. The high conductivity of sulfide solid electrolytes is achieved through the migration and diffusion of lithium ions via internal defects and transport channels within the crystal structure. However, the significant interfacial impedance between the electrolyte and electrodes, as well as between the electrolyte and internal grain boundaries, limits lithium ion conduction at the interface. Furthermore, due to the presence of electrolyte grain boundaries and pores, lithium dendrites can grow along these pores and boundaries, ultimately leading to short-circuit failure in all-solid-state batteries, severely restricting their commercial application. Summary of the Invention

[0004] The purpose of this invention is to address the limitations on improving the ionic conductivity of sulfide solid electrolytes (SSEs) caused by factors such as low internal strain and dislocation density leading to fewer lithium-ion transport channels, and high interfacial impedance due to large grain boundaries and porosity. This invention provides a simple method for improving the conductivity of SSEs and its applications. The high ionic conductivity SSE of this invention is prepared under high pressure. The increased dislocation density and reduced interfacial impedance can be maintained at room temperature and pressure. Furthermore, the preparation process requires no heating or pressure-transferring materials, making the method simple, safe, and reliable.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing a high-conductivity sulfide solid electrolyte includes the following steps: filling a high-pressure sample chamber with raw material powder and a pressure calibrator, pressurizing the sample chamber, maintaining the pressurization time, and obtaining a high-conductivity sulfide solid electrolyte.

[0007] The pressure of the pressurization treatment is ≥1.6 GPa, preferably 1.6-2.0 GPa; the pressurization treatment time is 20-60 min, preferably 30 min.

[0008] The molar ratio of each element in the raw material powder is Li:P:S:Cl = 5.5-6:0.9-1.0:4.5-5:1-1.5, and the preferred material is Li. 5.5 PS 4.5 Cl 1.5 powder.

[0009] In particular, when the ratio of Li, P, S, and Cl is 6:1:5:1, the initial ionic conductivity is 3.5 mS / cm. -1 Li6PS5Cl, after being held at a pressure of 2.8 GPa for at least 40 min, achieved a conductivity of 14.3 mS / cm. -1 Li6PS5Cl;

[0010] When the ratio of Li, P, S, and Cl is 5.5:1:4.5:1.5, Li 5.5 PS 4.5 Cl 1.5 Under a pressure of 2 GPa and maintained for at least 30 minutes, an electrical conductivity of 26.7 mS / cm was obtained. -1 Li 5.5 PS 4.5 Cl 1.5 ;

[0011] In particular, it also includes placing the pressure calibrator and raw materials together in a high-pressure device before performing the pressurization process, wherein the pressure calibrator is a ruby.

[0012] In particular, it also includes placing a soft metal between the raw material and the electrode to eliminate the resistance between the raw material and the electrode, wherein the metal is lithium and indium, preferably indium.

[0013] In particular, the high-pressure device is selected from diamond anvil press or double-sided press, preferably diamond anvil press.

[0014] In particular, the sample cavity is prepared by the following method: First, two diamonds are used to press a depression into the metal pad of the anvil press; then, a circular hole is drilled in the center of the depression with a laser. The cavity formed by the upper and lower diamond surfaces of the diamond anvil and the circular hole on the pad is the pressing cavity or sample cavity.

[0015] In particular, the metal gasket is a beryllium copper sheet.

[0016] The above method yields a high-conductivity sulfide solid electrolyte with an ionic conductivity greater than 25 mS / cm. Its crystal space group is: The lattice constant is:

[0017] High-conductivity sulfide solid electrolytes are used as electrolyte materials in solid-state lithium batteries. The increased dislocation density within the crystal lattice of high-conductivity sulfide solid electrolytes provides excellent pathways for lithium-ion migration. The closer contact between grains, smaller porosity, and reduced interfacial impedance further facilitate lithium-ion passage.

[0018] Compared with the prior art, the present invention has the following advantages and benefits:

[0019] 1. The method of the present invention can obtain high conductivity sulfide solid electrolyte materials through simple pressure treatment without heating or adding any pressure transmission medium. The whole process does not introduce other impurities, which not only saves preparation costs, but also does not pollute the environment. The method is simple, safe and reliable.

[0020] 2. The high-conductivity sulfide solid electrolyte material obtained by the present invention under high pressure has high dislocation density and low interfacial resistance. It can be stably stored at room temperature and pressure. The high-conductivity sulfide solid electrolyte material can be used as a good electrolyte material in solid-state lithium batteries, thereby increasing the capacity of solid-state lithium batteries.

[0021] 3. This invention addresses internal defects in the electrolyte crystal structure and optimizes the grain boundaries, pores, and internal defects of sulfide solid electrolytes using high pressure. By applying pressures exceeding 1.6 GPa, permanent strain is induced within the electrolyte, increasing dislocation density, expanding lithium-ion transport channels, and improving ion transport in sulfide solid electrolytes. Simultaneously, pressure also makes the contact between electrolyte grains tighter, reducing the obstruction of lithium-ion transport by grain boundaries and pores, thus improving its ionic conductivity. Furthermore, pressure, as a clean method, can improve ionic conductivity without altering the composition of the solid electrolyte, offering safety, controllability, and simple operation, providing a new approach to modulating the conductivity of sulfide solid electrolytes. Attached Figure Description

[0022] Figure 1 For sample Li 5.5 PS 4.5 Cl 1.5 X-ray diffraction spectra under different pressures;

[0023] Figure 2 Li in Example 2 5.5 PS 4.5 Cl 1.5 Ionic conductivity under different pressures;

[0024] Figure 3The AC impedance spectra of Li6PS5Cl in Example 3 are shown below at atmospheric pressure and after being depressurized from 3 GPa.

[0025] Figure 4 The ionic conductivity of Li6PS5Cl under different pressures in Example 3;

[0026] Figure 5 Li in Example 4 5.5 PS 4.5 Cl 1.5 Ionic conductivity under different pressures. Detailed Implementation

[0027] This invention provides a Li with high ionic conductivity 5.5 PS 4.5 Cl 1.5 The material and its high-pressure preparation method include the following steps:

[0028] Chemically pure raw material, silver sulfide germanium ore type Li 5.5 PS 4.5 Cl 1.5 The powder and pressure calibrator are loaded into the diamond anvil chamber (i.e., the sample chamber) of the diamond anvil press, and then the Li in the sample chamber is... 5.5 PS 4.5 Cl 1.5 Powder was pressurized to a pressure greater than or equal to 1.6 GPa to obtain Li with high ionic conductivity. 5.5 PS 4.5 Cl 1.5 After being held under high pressure (≥1.6 GPa) for more than 30 minutes, the product after depressurization exhibits high ionic conductivity, specifically Li. 5.5 PS 4.5 Cl 1.5 It can be stored stably at room temperature.

[0029] Among them, the pressure calibrator is a substance used to calibrate the pressure inside the pressure chamber, usually ruby. During the pressurization process, the pressure inside the pressure chamber can be obtained in real time through the pressure calibrator.

[0030] The diamond anvil cell is prepared by the following method: First, two diamonds are used to press a depression into the metal pad of the anvil press; then, a circular hole is drilled in the center of the depression using a laser. The cavity formed by the upper and lower surfaces of the diamond anvil and the circular hole in the pad is the pressure cavity or sample cavity.

[0031] In a specific embodiment of the present invention, the diamond anvil cell press is preferably a symmetrical diamond anvil cell device. In this invention, the diameter of the diamond anvil cell facet of the diamond anvil cell press is 1000 μm; the diameter of the pressing chamber of the diamond anvil cell press is 600 μm, and the height is 150 μm (typically 100–200 μm). The pressing chamber is formed by laser drilling holes (with a hole diameter of 600 μm (typically 200–700 μm)) in an insulating gasket; the insulating gasket is a beryllium copper sheet with a layer of cubic boron nitride pressed onto its surface. The use of beryllium copper as a sealing gasket in this invention provides protection for the diamond.

[0032] After the pressure chamber is fabricated, this invention will have an initial ionic conductivity of 9 mS / cm. -1 Li 5.5 PS 4.5 Cl 1.5 The powder is filled into the pressure chamber, and the particle size of the powder is 5-40 micrometers.

[0033] Li 5.5 PS 4.5 Cl 1.5 The powder is loaded into the pressing chamber of the diamond anvil cell press, wherein the Li powder is loaded into the chamber. 5.5 PS 4.5 Cl 1.5 At that time, it is made to completely fill the pressure cavity without leaving any gaps; in a specific embodiment of the present invention, specifically, Li is used to fill the pressure cavity with approximately 110% of its volume. 5.5 PS 4.5 Cl 1.5 The powder is loaded into the pressure chamber and compacted to ensure that the pressure chamber is completely filled, i.e., the Li before loading. 5.5 PS 4.5 Cl 1.5 The ratio of the powder bulk volume to the pressure chamber volume is approximately 110:100 (typically ≥110:100).

[0034] Place the soft metal in Li 5.5 PS 4.5 Cl 1.5 To eliminate Li between powder and electrode 5.5 PS 4.5 Cl 1.5 The resistance between the powder and the electrode, wherein the metal is preferably indium.

[0035] In this invention, the pressure calibrator is a ruby ​​ball, preferably with a particle size of 20–40 μm (30 μm in this case), and the amount used is 2–5 balls (3 balls in this case). Other pressure calibrators besides ruby ​​balls include SrB4O7:Sm 2 + Diamond is also applicable to this invention, and ruby ​​balls are pressure calibrators commonly used in the art.

[0036] In a specific embodiment of the present invention, the ruby ​​is preferably first loaded under the electrode in the pressure cavity, and then Li with a particle size of 5-40 micrometers is placed using a tungsten needle. 5.5 PS 4.5 Cl 1.5 Place it into the pressure cavity, fill it completely and compact it, leaving no gaps.

[0037] After loading, the upper part of the diamond anvil cell is closed, sealing the sample in the pressure chamber. The pressure inside the pressure chamber is adjusted by adjusting the pressure screw of the diamond anvil cell press, thus regulating the Li content within the chamber. 5.5 PS 4.5 Cl 1.5 High ionic conductivity Li was obtained by pressurization treatment. 5.5 PS 4.5 Cl 1.5 ;

[0038] The pressurization process involves maintaining the pressure within the pressure chamber at a level above 1.6 GPa, preferably 1.6–2 GPa, and most preferably above 1.6 GPa. The pressure maintenance time is ≥30 min, preferably 30 min.

[0039] During the process of adjusting the pressure in the pressure chamber by adjusting the pressure screw, the pressure application rate of the pressure screw is 1.0 to 2.0 GPa / min (preferably 1.5 to 2.0 GPa / min). Controlling the pressure application rate can accelerate the formation of dislocations inside the sample and also protect the diamond from breakage.

[0040] During the pressurization process, the pressure value inside the pressure chamber is calculated according to formula (1) based on the fluorescence peak of the ruby ​​measured by the fluorescence spectrometer. The relationship between the fluorescence peak position of the ruby ​​and the pressure (P) is as shown in formula (1):

[0041] P = 380.8 × [(6942 Δλ + 1) 5 - 1] (1)

[0042] Where Δλ is the peak position difference of the ruby ​​R2 peak under pressure and without pressure.

[0043] In this invention, the pressure inside the regulating chamber is achieved by adjusting the pressure screw of the diamond anvil press, and the pressure rate of the pressure screw is 1.0 to 2.0 GPa / min (preferably 1.5 to 2.0 GPa / min).

[0044] The present invention employs a pressurization rate to uniformly apply pressure to the cavity of the diamond anvil press, thereby obtaining high pressure in the pressure cavity located between the anvil faces of the two diamond anvils. Under high pressure conditions, Li 5.5 PS4.5 Cl 1.5 The internal dislocation density increases and the grain boundary resistance decreases, and this is maintained for more than 30 minutes (preferably 30 minutes) under high pressure.

[0045] This invention does not add a pressure-transmitting medium during the pressurization process, thereby creating a non-hydrostatic environment that allows shear force to be generated inside the pressure chamber. This shear force can promote an increase in dislocation density.

[0046] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments thereof.

[0047] Example 1

[0048] The beryllium copper sheet is pre-pressed using a diamond anvil press with a 1000μm anvil face. After pre-pressing, the beryllium copper sheet has a higher density and can withstand greater pressure without easily deforming.

[0049] After pre-compression, the diamond forms a frustum-like depression on the beryllium copper sheet. The spacer is removed from the diamond, and a circular hole (600 μm in diameter) is laser-drilled in the center of the depression. The presence of the depression allows for easy repositioning of the spacer, allowing it to be placed back onto the lower diamond without creating a gap between them. This circular hole serves as a pressure cavity, formed by the upper and lower surfaces of the diamond anvil cell and the circular hole on the spacer.

[0050] First, add Li, whose volume is 110% of the pressure chamber volume. 5.5 PS 4.5 Cl 1.5 Powder (purchased from Guolian Automotive Power Battery Research Institute Co., Ltd., purity ≥99.5%) is filled into the pressure chamber without adding a pressure transmission medium. 5.5 PS 4.5 Cl 1.5 The powder fills the pressure chamber, and then a ruby ​​ball is placed in the center of the sample as a pressure calibrator.

[0051] Close the upper diamond and fill with Li. 5.5 PS 4.5 Cl 1.5 The powder compression chamber is then sealed. The pressure screw of the diamond anvil press is adjusted, and the diamond extrudes the compression chamber, increasing the pressure inside the chamber and pressurizing the raw material. The pressure on the raw material increases. The pressure rate of the pressure screw is controlled to be 1.5 GPa / min (usually 1.0 to 2.0 GPa / min, preferably 1.5 to 2.0 GPa / min).

[0052] During the pressurization process, in-situ X-ray diffraction was used to detect Li within the diamond anvil cell press chamber. 5.5 PS4.5 Cl 1.5 X-ray diffraction pattern of the sample (e.g.) Figure 1 As shown):

[0053] When the pressure inside the chamber increases from atmospheric pressure to 0.9 GPa, the atomic and interplanar spacing of the sample decreases under the influence of pressure, the diffraction peaks shift towards larger angles, and the diffraction peaks broaden. When the pressure is further increased to 1.5 GPa, the atomic and interplanar spacing of the sample continues to decrease, and the diffraction peaks continue to broaden.

[0054] When the pressure inside the chamber was further increased to 2 GPa and maintained for 30 minutes, and then released to atmospheric pressure, the broadened diffraction peaks did not return to their initial state, resulting in an ionic conductivity of 25.1 mS / cm. -1 Li 5.5 PS 4.5 Cl 1.5 .

[0055] Example 2

[0056] Except for drilling a 600 μm hole in the indentation, the pretreatment of the gasket was the same as in Example 1. Then, a layer of cubic boron nitride powder was laid on the indentation cavity and the entire indentation, and an upper diamond was attached. Pressure was then applied to 1 GPa, causing the cubic boron nitride to fill the sample cavity and be compacted and adhered to the gasket. A 600 μm hole was then drilled in the center of the indentation. An insulating layer was then pressed onto the reverse side of the gasket using the same method, and a 600 μm diameter hole was drilled to serve as the sample cavity. At this point, the indentation cavity was surrounded by a 20 μm thick cubic boron nitride insulating layer. A platinum electrode was then attached to the lower diamond anvil and led out using copper wire. The insulating gasket was repositioned on the lower diamond, and an indium sheet with a diameter of 300 μm and a thickness of 10 μm was placed in the center of the platinum electrode. Li was then loaded into the indentation cavity. 5.5 PS 4.5 Cl 1.5 An indium sheet of the same size was placed on the upper surface of the sample. A platinum electrode was attached to the diamond anvil and led out with a copper wire. After the diamond anvil was closed, the two platinum electrodes were in contact with the indium sheet. Under different pressure conditions (pressure rate of 1.5 GPa / min), i.e., according to the pressure method of Example 1, the raw material in the pressure chamber was pressurized. The sample impedance was measured using an electrochemical workstation under 0, 0.9, 1.6, 2.0 GPa (held for 30 min) and depressurization conditions. The conductivity test results of the material under different pressures are as follows. Figure 2 As shown.

[0057] The test results show that: Li 5.5 PS 4.5 Cl 1.5 Its initial conductivity is 9.14 mS / cm -1 After depressurization from 1.6 GPa, Li 5.5 PS4.5 Cl 1.5 Its electrical conductivity is 25.5 mS / cm -1 After depressurization from 2GPa, Li 5.5 PS 4.5 Cl 1.5 Its conductivity is 26.7 mS / cm -1 .

[0058] Example 3

[0059] To explore whether high-conductivity sulfide solid electrolytes could be prepared using raw materials with other elemental ratios, Li6PS5Cl powder (purchased from Guolian Automotive Power Battery Research Institute Co., Ltd., purity ≥99.5%) with an elemental ratio of 6:1:5:1 was pressurized (pressurization rate 1.5 GPa / min) to 0.3, 0.5, 1.1, 1.6, 1.9, 2.2, 2.5, 2.6, 2.8, and 3 GPa, respectively. After being held at 3 GPa for 30 min, the pressure was released to atmospheric pressure. The remaining processes and conditions were the same as in Example 2.

[0060] During the pressurization process, the AC impedance spectrum of the Li6PS5Cl sample inside the diamond anvil press chamber was detected by in-situ high-voltage electrical testing, and the conductivity of the sample was calculated (e.g., ...). Figure 3 , Figure 4 (As shown).

[0061] The initial conductivity of Li6PS5Cl sample was 3.5 mS / cm after being pressurized to 3 GPa and held for 30 min and then discharged to atmospheric pressure. -1 The conductivity after pressure treatment is 14.3 mS / cm -1 .

[0062] Example 4

[0063] To eliminate the influence of accidental factors on Li after stress treatment 5.5 PS 4.5 Cl 1.5 To investigate the effect of electrical conductivity characteristics, we repeated the experiment of Example 2 (the procedure and conditions were the same as in Example 2). Figure 5 For Li after repeating the experiment 5.5 PS 4.5 Cl 1.5 Conductivity change. After pressurizing Li6PS5Cl to 2.0 GPa and holding for 30 min, then releasing to atmospheric pressure, the initial conductivity of the sample was 9.1 mS / cm. -1 The conductivity after pressure treatment is 25.2 mS / cm -1 .

[0064] In summary, this invention utilizes a diamond anvil cell for the processing of Li 5.5 PS4.5 Cl 1.5 The sample was subjected to a pressure of 1.6 to 2 GPa, causing Li 5.5 PS 4.5 Cl 1.5 The sample transforms into Li with high ionic conductivity 5.5 PS 4.5 Cl 1.5 After depressurization, Li 5.5 PS 4.5 Cl 1.5 The irreversible conductivity of Li allows for the production of high ionic conductivity Li at room temperature. 5.5 PS 4.5 Cl 1.5 The purpose of the sample is to ensure safe operation.

[0065] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-conductivity sulfide solid electrolyte, characterized in that, The LPSCI raw material powder was pressurized and kept under a certain pressure and pressurization time to obtain a high conductivity sulfide solid electrolyte.

2. The preparation method according to claim 1, characterized in that, The pressure of the pressurization process is ≥1.6 GPa, preferably 1.6-2.0 GPa, more preferably 1.8-2.0 GPa; the pressurization rate is 1.0-2.0 GPa / min, preferably 1.5-2.0 GPa / min; The pressurization time is 20-60 minutes, preferably 30-40 minutes.

3. The preparation method according to claim 1, characterized in that, The molar ratio of each element in the LPSCI raw material powder is Li:P:S:Cl = 5.5-6:0.9-1.0:4.5-5:1-1.5, preferably Li:P:S:Cl = 5.5-5.6:0.95-1.0:4.5-4.6:1.2-1.5, and more preferably Li 5.5 PS 4.5 Cl 1.5 powder.

4. The preparation method according to claim 3, characterized in that, The Li 5.5 PS 4.5 Cl 1.5 The powder particle size is 5-40 micrometers.

5. The preparation method according to any one of claims 1-4, characterized in that, Includes the following steps: The LPSCI raw material powder was filled into the sample cavity, and the sample cavity was pressurized. A certain pressure and pressurization time were maintained to obtain a high conductivity sulfide solid electrolyte. The pressurization process is carried out on a diamond anvil press. The high-pressure sample chamber preparation method includes: firstly, pressing a depression into the metal pad of the anvil press with two diamonds; then, drilling a circular hole in the center of the depression with a laser. The cavity formed by the upper and lower diamond surfaces of the diamond anvil and the circular hole in the pad constitutes the sample chamber.

6. The preparation method according to claim 5, characterized in that, The sample chamber is filled with a pressure calibrator, which is ruby.

7. A high-conductivity sulfide solid electrolyte, characterized in that, It is prepared by any one of the preparation methods of claims 1-6.

8. The sulfide solid electrolyte according to claim 7, characterized in that, The ionic conductivity is greater than 25 mS / cm.

9. The sulfide solid electrolyte according to claim 7, characterized in that, The crystal space group is: (No. 216), the lattice constant is:

10. The use of a sulfide solid electrolyte according to any one of claims 7-9 in a lithium-ion battery.

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