Sulfide solid electrolyte having a chloride gas phase coating layer and a method of preparing the same

Abstract

The application discloses a chloride-coated sulfide solid electrolyte and a preparation method and application thereof. The electrolyte comprises a sulfide electrolyte core of argyrodite type and a chloride coating layer coated on the surface of the core. The chemical general formula of the sulfide electrolyte is Li 7−x PS 6−x Cl x ·n(MCl y ), wherein M is one or more of Fe, Zr, Al, Sb, Ta and Nb. The chloride coating layer is continuously distributed on the surface of the sulfide electrolyte core particles. The application adopts a gas phase sublimation deposition method to construct a continuous and dense chloride coating layer on the surface of the sulfide electrolyte particles, does not introduce any organic solvent in the whole process, and does not include any mechanical ball milling step, thereby avoiding solvent-induced side reactions and the destruction of the crystal structure caused by mechanical impact. The application effectively inhibits the interface side reaction between the sulfide electrolyte and the positive electrode material, significantly improves the interface compatibility and cycle stability, and is suitable for a full solid-state battery system.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery electrolyte material technology, specifically involving several methods for preparing and applying chloride-coated modified sulfide electrolytes, and particularly involving a technique for coating and modifying the surface of sulfide electrolytes through the vaporization and sublimation of low-boiling-point chlorides. Background Technology

[0002] All-solid-state batteries have become one of the core development directions for next-generation power batteries due to their superior safety and high energy density. Australite-type sulfide solid electrolytes, as key materials for all-solid-state batteries, have attracted widespread attention due to their high ionic conductivity, good ductility, and ability to form good physical contact with electrode materials. However, australite-type sulfide solid electrolytes suffer from limited oxidation stability (typically below 3 V) and poor interfacial compatibility with high-voltage cathode materials, severely limiting their application in high-energy-density all-solid-state batteries.

[0003] To address the aforementioned issues, existing technologies often employ surface coating modification to treat sulfide electrolytes. By forming a stable coating layer on the surface, direct contact between air and electrode materials is isolated, thereby improving stability and interfacial compatibility.

[0004] The mainstream methods for coating sulfide electrolytes are mainly divided into two categories: dry ball milling coating and wet solvent coating. However, both methods have significant drawbacks. Wet solvent coating involves dissolving or suspending the coating material in a solvent, mixing it with sulfide electrolyte powder, and then drying and heat-treating to form a coating layer. However, the core drawback of this method is twofold: firstly, the introduction of solvent may cause hydrolysis or solvation reactions in the sulfide electrolyte, damaging its crystal structure and reducing ionic conductivity; secondly, the uniformity of the coating layer thickness is difficult to control, easily leading to incomplete coating in certain areas or excessively thick coating layers that hinder ion conduction. Furthermore, solvent evaporation during drying can create pores in the coating layer, affecting its density. Dry ball milling coating, on the other hand, physically mixes chloride and sulfide electrolyte powders through mechanical ball milling to achieve surface coating. However, it also has significant drawbacks: First, the mechanical impact during ball milling can easily cause sulfide electrolyte particles to break and crystal structure defects, significantly reducing their intrinsic ion conductivity. Second, the coating effect is highly dependent on the ball milling parameters, and problems such as local agglomeration and discontinuous coating are prone to occur, making it difficult to form a uniform and dense coating layer. Third, the powder is easily oxidized by air during ball milling, and impurities from the ball milling media may be introduced, further deteriorating the electrolyte performance.

[0005] In sulfide-based all-solid-state batteries, constructing a chloride coating layer (such as AlCl3 or ZrCl4) on the surface of the intercalated oxide cathode (such as NCM or LCO) is a key strategy to address its intrinsic interface problem. Its core advantages are: 1. Kinetic optimization: the coating layer acts as a buffer layer for the lithium chemical potential, effectively suppressing harmful space charge layer effects and significantly reducing interface impedance; 2. Chemical stability: the dense coating layer physically isolates the sulfide electrolyte from the erosion of strong oxidizing substances (such as reactive oxygen species and high-valence metal ions) at high voltages and blocks the bidirectional diffusion of harmful elements; 3. Structural reinforcement: it enhances the mechanical contact and compatibility between the cathode particles and the solid electrolyte, maintaining the structural integrity of the composite electrode during cycling. This technology, by constructing a multifunctional interface phase, systematically improves the rate performance, cycle life, and safety of the battery, making it an effective way to promote the practical application of high-energy-density sulfide-based solid-state batteries. Summary of the Invention

[0006] The purpose of this invention is to overcome some of the problems existing in the commonly used coating modification methods for sulfide solid electrolytes of silver-germanium sulfide in the prior art, such as the difficulty in selecting solvents for wet coating and the interference with sulfide electrolytes, and the uniformity and long time of dry ball milling coating, while solving the interface problem between sulfide electrolytes and intercalated oxide cathodes.

[0007] To address the aforementioned problems, this method utilizes the vaporization and sublimation of chlorides to form a uniform and dense coating layer on the surface of the sulfide electrolyte. This eliminates the need for solvents and ball milling, effectively preserving the intrinsic properties of the sulfide electrolyte and significantly improving its stability and interfacial compatibility. Therefore, in three aspects: first, this invention provides a low-boiling-point chloride-coated modified sulfhydryl germanite-type solid electrolyte; second, this invention provides a method for preparing the chloride-coated modified sulfhydryl germanite-type solid electrolyte; and third, this invention provides an application of the chloride-coated modified sulfhydryl germanite-type solid electrolyte in all-solid-state batteries.

[0008] 1. In a first aspect, a chloride-coated modified silver-germanium sulfide solid electrolyte is provided, characterized in that the electrolyte comprises a sulfide electrolyte core and a chloride coating layer coating the core, having the general chemical formula Li. 7−x PS 6− x Cl x · n(MCl y ).

[0009] Where x takes values ​​in the range of 1 ≤ x ≤ 1.5, n takes values ​​in the range of 0.0001 ≤ n ≤ 0.05, and y corresponds to the number of chlorine atoms corresponding to the valence state of element M, specifically MCl. yWhen the y=3 is FeCl3, y=4 is ZrCl4, y=3 is AlCl3, y=3 is SbCl5, y=5 is TaCl5, and y=5 is NbCl5.

[0010] Preferably, the value of n is in the range of 0.0005 ≤ n ≤ 0.01

[0011] Preferably, the chloride coating layer is a phase formed by in-situ deposition on the surface of the sulfide electrolyte particles, rather than a phase formed through liquid-phase reaction or mechanical mixing. The chloride coating layer is continuously distributed on the surface of the sulfide electrolyte bulk particles, and the coating layer thickness is 5-50 nm. The ionic conductivity of the electrolyte at 30°C is not less than 3 mS / cm.

[0012] The inventors propose that the selected chlorides offer advantages in terms of sublimation temperature adaptability, chemical stability, and compatibility with sulfide electrolytes. Within the aforementioned preferred parameter range, the modified sulfide electrolyte exhibits optimal performance. If the coating layer is too thin, it is difficult to form a complete protective layer, failing to effectively isolate external corrosion; if the thickness is too thick, it increases lithium-ion transport resistance and reduces ionic conductivity. A coating layer of 5-50 nm ensures effective protection for the vast majority of sulfide electrolyte particles. Combined with limitations on ionic conductivity and hydrolysis rate, this simultaneously guarantees the electrolyte's conductivity and stability, meeting the high-efficiency and stable operation requirements of all-solid-state batteries.

[0013] Secondly, the present invention provides a method for preparing a chloride-coated modified sulfide solid electrolyte of the silver-germanium sulfide type, comprising the following steps:

[0014] Step (1) Main pretreatment steps: The sulfide electrolyte raw powder is dried and sieved to remove surface adsorbed water and soft agglomerates, and obtain sulfide electrolyte powder with uniform particle size distribution.

[0015] Step (2) Precursor preparation step: Grind or sieve the chloride precursor powder to make its particle size smaller than the average particle size of the sulfide electrolyte powder, so as to improve the stability of its vaporization sublimation rate.

[0016] Step (3) Sublimation deposition coating step: The sulfide electrolyte powder treated in step (1) is spread evenly in the sample holder of the sublimation coating device, and the chloride precursor powder treated in step (2) is placed in the sublimation zone of the device. The device is then evacuated or sealed after being purged with inert gas. Subsequently, the temperature of the sublimation zone and the temperature of the sample holder are controlled respectively to make the chloride precursor vaporize and sublimate to form vapor, and deposit and condense on the surface of the sulfide electrolyte powder, thereby forming a continuous chloride coating layer in situ on the surface of the sulfide electrolyte main particles.

[0017] Step (4) Cooling and shaping step: The coated powder is naturally cooled or programmed cooling is performed under an inert gas atmosphere, followed by sieving or loosening to remove secondary agglomerated particles, and the chloride-coated sulfide solid electrolyte product is obtained.

[0018] Preferably, the drying temperature in step (1) is 40-120℃; the drying time is 2-24 h; the sieve mesh size in step (1) is 100-500 mesh; and the D of the chloride precursor powder in step (2) is... 50 It ranges from 1 to 10 μm.

[0019] Preferably, the sieve mesh size is 500 mesh.

[0020] Preferably, step (3) is performed under any of the following atmospheric conditions: evacuation to 10... -1 -10 3 After sealing; or carried out in an inert gas atmosphere;

[0021] Preferably, the inert gas is argon or nitrogen with a purity > 99.99%.

[0022] Preferably, in step (3), the sublimation coating device assembly involves spreading the sieved pretreated sulfide electrolyte powder evenly in the sample holder of the sublimation coating device, placing the chloride powder in the sublimation zone of the device, and maintaining a certain height between the sample holder and the sublimation zone; and sealing the device. The sublimation coating device includes a sealed cavity, a temperature-controlled sublimation zone, and an adjustable height sample holder.

[0023] Preferably, the height of the sublimation zone and the sample holder is 5-30 cm;

[0024] Preferably, the sealed cavity is protected by high-purity argon gas at atmospheric pressure, with an argon purity requirement of ≥99.99%. The sublimation zone is heated by resistance heating, the temperature control accuracy of the sample holder is ±1 ℃, and the heating rate of the sublimation zone is 2 ℃ / min.

[0025] Preferably, in step (3), the sublimation heating deposition process requires controlling the temperature of the sublimation zone to the sublimation temperature of chloride so that the chloride powder is vaporized and sublimated to form vapor; at the same time, the temperature of the sample holder is controlled to the preset deposition temperature so that the chloride vapor is deposited and condensed on the surface of the sulfide electrolyte powder to form a coating layer; after the preset holding time, heating is stopped and the sample is allowed to cool naturally to room temperature.

[0026] Preferably, the chloride purity is ≥99.9%, and the sublimation temperature is 300-350℃ when the chloride is FeCl3; 400-450℃ when it is ZrCl4; 180-220℃ when it is AlCl3; 250-300℃ when it is SbCl5; 230-270℃ when it is TaCl5; and 230-270℃ when it is NbCl5.

[0027] Preferably, the deposition temperature is 50-150 ℃, more preferably 80-120 ℃; the preset heat preservation time is 1-8 h, more preferably 1-3 h.

[0028] Preferably, in step (4), the cooled coated modified sulfide electrolyte powder is taken out and sieved under inert gas protection to remove agglomerated particles, thereby obtaining the chloride-coated modified sulfide electrolyte product.

[0029] Preferably, in step 4, the inert gas is argon or nitrogen; the sieving is performed using a 100-300 mesh standard sieve.

[0030] Thirdly, the present invention provides a battery comprising the above-mentioned chloride-coated sulfide solid electrolyte of silver-germanium sulfide or the chloride-coated sulfide solid electrolyte of silver-germanium sulfide prepared by the above-mentioned preparation method.

[0031] Due to the adoption of the above technical solutions, the technological progress achieved by this invention is mainly reflected in the following aspects:

[0032] (1) This invention uses a sulfide solid electrolyte of the sulfide type as the main body and constructs a continuous and dense chloride coating layer on the surface of its particles to realize a composite solid electrolyte structure with the electrolyte itself as the core and significantly improved interfacial stability. The formed chloride coating layer does not contain sulfur, which can effectively avoid the interfacial side reactions generated by traditional sulfide electrolytes during contact with high-voltage cathode materials, thereby improving the electrochemical stability of the electrolyte from the material bulk level.

[0033] (2) Unlike existing discrete coating structures obtained through wet coating or mechanical mixing, this invention employs a vapor-phase sublimation-in-situ deposition method, enabling chlorides to preferentially nucleate and continuously grow on the surface of sulfide electrolyte particles of silver-germanium sulfide, thereby forming a uniform, continuous, and controllable thickness nanoscale coating layer. The interface between this coating layer and the electrolyte core is tightly bonded, without introducing significant interfacial impedance, effectively avoiding the ion transport obstruction problems caused by uneven coating or local agglomeration in traditional coating methods.

[0034] (3) By precisely controlling the thickness of the chloride coating layer, this invention significantly improves the stability of the electrolyte interface while maintaining the original high ionic conductivity of the sulfide electrolyte of silver-germanium sulfide. It achieves synergistic optimization between interface stability and ion conduction performance, and overcomes the technical contradiction in the prior art that "improving stability inevitably sacrifices conductivity".

[0035] (4) The preparation method adopted in this invention does not require the introduction of organic solvents throughout the process and does not involve mechanical ball milling and coating steps. It fundamentally avoids the damage to the electrolyte crystal structure caused by solvent residue, hydrolysis reaction and mechanical impact. The process route is clear, highly controllable, and has good repeatability and industrial scale-up feasibility. Attached Figure Description

[0036] Figure 1 For example of TEM of sulfide electrolyte with chloride vapor phase coating, the TEM test was performed with an accelerating voltage of 200kV. Twenty electrolyte particles were randomly selected, and the coating thickness at three different locations was measured for each particle. The average value was taken as the coating thickness. It can be observed that the surface coating is 15-25nm.

[0037] Figure 2 Electrochemical impedance spectroscopy for ZrCl4-LPSC series;

[0038] Figure 3 Electrochemical impedance spectroscopy for ZrCl4-LPSC1.5 series;

[0039] Figure 4 Electrochemical performance of ZrCl4-LPSC series;

[0040] Figure 5 Electrochemical performance of ZrCl4-LPSC1.5 series;

[0041] Figure 6 Electrochemical performance of the TaCl5-LPSC1.5 series. Detailed Implementation

[0042] To make the objectives, technical solutions, and technical effects of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. The embodiments described below are some embodiments of the present invention, but not all embodiments. In conjunction with the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] The term "sulfide electrolyte of the sulfide type" as used in this article includes the sulfide structure in the strict crystallographic sense, as well as the derived structures that retain the main framework structural features after halogen doping and vacancy regulation.

[0044] In the description of this invention, when "-" is used to indicate numerical ranges, they include both endpoints, and the units are common. For example, "particle size of 1.00-100.00 μm" for argyrocerium sulfide solid electrolytes means that the particle size of the argyrocerium sulfide solid electrolyte is 1.00 μm or larger and 100.00 μm or smaller.

[0045] In the description of this invention, "D" 50 "" refers to the particle size at which the cumulative particle size distribution percentage of the sample reaches 50%.

[0046] It should be understood that the mass of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the masses of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope of this invention. Specifically, the weight mentioned in the embodiments of this invention can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0047] Furthermore, unless the context explicitly uses it otherwise, the singular form of a word should be understood as including the plural form of the word. The terms "comprising" or "having" are intended to specify the presence of a feature, quantity, step, operation, element, part, or combination thereof, but are not intended to exclude the presence or possible addition of one or more other features, quantities, steps, operations, elements, parts, or combinations thereof.

[0048] Example 1

[0049] (I) Preparation of Li6PS5Cl (LPSC) sulfide solid electrolyte particles

[0050] 1. In a glove box under an argon atmosphere, Li₂S, P₂S₅, and LiCl were thoroughly mixed in a molar ratio of 5:1:2 to obtain 6.0 g of mixed powder. The powder was ball-milled using 10 mm diameter zirconia balls at a speed of 500 rpm for 30 hours, with a ball-to-powder mass ratio of 40:1. The ball-milled powder was then further ground in a mortar to achieve a fine powder.

[0051] 2. The dried powder was sieved using a 300-mesh standard sieve to obtain 5.5 g of powdered Li6PS5Cl sulfide solid electrolyte particles. The particle size D was measured using a laser particle size analyzer. 50 It is 20.0 μm.

[0052] (II) Preparation of coated sulfide solid electrolyte ZrCl4-LPSC

[0053] 1. Select zirconium tetrachloride as the chloride raw material, grind it to a particle size of 1-5 μm, and weigh the raw material according to the molar ratio of zirconium tetrachloride to sulfide electrolyte of 0.01:1.

[0054] 2. Spread the Li6PS5Cl sulfide solid electrolyte particles prepared in step (I) evenly in the sample holder of the sublimation coating device (2 mm thick), place the zirconium tetrachloride powder in the sublimation zone of the device, and keep the sample holder 15 cm away from the sublimation zone.

[0055] 3. Sealing device

[0056] 4. Turn on the sublimation zone heating device and raise the temperature to 450 ℃ to vaporize and sublimate the zirconium tetrachloride powder into vapor; at the same time, control the temperature of the sample holder at 100 ℃ to allow the zirconium tetrachloride vapor to deposit and condense on the surface of the sulfide electrolyte; after holding at this temperature for 1.5 h, turn off the heating device and allow it to cool naturally to room temperature.

[0057] 5. Under argon protection, the coated electrolyte powder is removed and sieved using a 300-mesh standard sieve to remove a small amount of agglomerated particles, resulting in a powdered coated sulfide solid electrolyte ZrCl4-LPSC with an internal Li6PS5Cl sulfide solid electrolyte and a ZrCl4 coating layer on the surface.

[0058] Example 2

[0059] (I) Li 5.5 PS 4.5 Cl 1.5 Preparation of (LPSCl) sulfide solid electrolyte particles

[0060] 1. In a glove box under an argon atmosphere, Li₂S, P₂S₅, and LiCl were thoroughly mixed in a molar ratio of 4:1:3 to obtain 6.0 g of mixed powder. The powder was ball-milled using 10 mm diameter zirconia balls at 300 rpm for 20 hours, with a ball-to-powder mass ratio of 30:1. The ball-milled powder was then further ground in a mortar to achieve a fine powder.

[0061] 2. Place the powder obtained in step 1 in a vacuum drying oven and dry it for 5 h under a vacuum of 6 Pa and a temperature of 110 ℃.

[0062] 3. The dried powder was sieved using a 180-mesh standard sieve to obtain powdered LPSC1.5 sulfide solid electrolyte. The Do was measured using a laser particle size analyzer. 50 The particle size is 25.0 μm.

[0063] (II) Preparation of coated sulfide solid electrolyte ZrCl4-LPSC1.5

[0064] 1. Select zirconium tetrachloride and grind it to a particle size of 1-4 μm. Weigh the raw materials according to a zirconium tetrachloride to sulfide electrolyte molar ratio of 0.01:1.

[0065] 2. The Li prepared in step (I) 5.5 PS 4.5 Cl 1.5 The sulfide solid electrolyte particles were spread evenly on the sample holder (2 mm thick), and zirconium tetrachloride was placed in the sublimation zone. The sample holder was 12 cm away from the sublimation zone.

[0066] 3. Sealing device.

[0067] 4. Raise the temperature of the sublimation zone to 450 ℃, control the temperature of the sample holder at 90 ℃, keep it at this temperature for 1.5 h, then stop heating and allow it to cool naturally to room temperature.

[0068] 5. The powder was removed under nitrogen protection and sieved through a 300-mesh sieve to obtain a powder with an internal composition of Li. 5.5 PS 4.5 Cl 1.5 ZrCl4-LPSC1.5 is a coated solid electrolyte of sulfide with a ZrCl4 coating layer on its surface.

[0069] Example 3

[0070] (I) Li 5.5 PS 4.5 Cl 1.5 Preparation of (LPSCl) sulfide solid electrolyte particles

[0071] 1. In a glove box under an argon atmosphere, Li₂S, P₂S₅, and LiCl were thoroughly mixed in a molar ratio of 4:1:3 to obtain 6.0 g of mixed powder. The powder was ball-milled using 10 mm diameter zirconia balls at 300 rpm for 20 hours, with a ball-to-powder mass ratio of 30:1. The ball-milled powder was then further ground in a mortar to achieve a fine powder.

[0072] 2. Place the powder obtained in step 1 in a vacuum drying oven and dry it for 5 h under a vacuum of 6 Pa and a temperature of 110 ℃.

[0073] 3. The dried powder was sieved using a 180-mesh standard sieve to obtain powdered LPSC1.5 sulfide solid electrolyte. The Do was measured using a laser particle size analyzer. 50 The particle size is 25.0 μm.

[0074] (II) Preparation of coated sulfide solid electrolyte TaCl5-LPSC1.5

[0075] 1. Select tantalum pentachloride and grind it to a particle size of 1-4 μm. Weigh the raw material (i.e., 180 mg of tantalum pentachloride) according to the molar ratio of tantalum pentachloride to sulfide electrolyte of 0.03:1.

[0076] 2. The Li prepared in step (I) 5.5 PS 4.5 Cl 1.5 Sulfide solid electrolyte particles were spread evenly on the sample holder (2 mm thick), and tantalum pentachloride was placed in the sublimation zone. The sample holder was 12 cm away from the sublimation zone.

[0077] 3. Sealing device.

[0078] 4. Raise the temperature of the sublimation zone to 230 ℃, control the temperature of the sample holder at 30 ℃, keep it at this temperature for 1.5 h, then stop heating and allow it to cool naturally to room temperature.

[0079] 5. The powder was removed under nitrogen protection and sieved through a 300-mesh sieve to obtain a powder with an internal composition of Li. 5.5 PS 4.5 Cl 1.5 TaCl5-LPSC1.5 is a coated sulfide solid electrolyte with a TaCl5 coating layer on its surface.

[0080] Comparative Example 1

[0081] The preparation method for Li6PS5Cl (LPSC) sulfide solid electrolyte particles is the same as that in step (i) of Example 1, without any coating treatment.

[0082] Comparative Example 2

[0083] Preparation of Li 5.5 PS 4.5 Cl 1.5 (LPSC1.5) Sulfide solid electrolyte particles are prepared using the same method as step (i) in Example 3, without any coating treatment.

[0084] Comparative Example 3

[0085] (I) Preparation of Li6PS5Cl (LPSC) sulfide solid electrolyte particles

[0086] The preparation method is the same as step (i) in Example 1.

[0087] (II) Preparation of coated sulfide solid electrolyte ZrCl4-LPSC (wet coating)

[0088] 1. Weigh zirconium tetrachloride according to a molar ratio of zirconium tetrachloride to sulfide electrolyte of 0.01:1, add anhydrous ethanol as solvent, and stir to disperse for 2 h to obtain a suspension.

[0089] 2. Add the Li6PS5Cl sulfide solid electrolyte particles prepared in step (I) to the above suspension and stir for 4 h.

[0090] 3. The solvent was removed by vacuum drying at 80 °C for 12 h to obtain a coated sulfide solid electrolyte powder with an internal Li6PS5Cl sulfide solid electrolyte and a ZrCl4 coating layer on the surface.

[0091] Comparative Example 4

[0092] (I) Preparation of Li6PS5Cl (LPSC) sulfide solid electrolyte particles

[0093] The preparation method is the same as step (i) in Example 1.

[0094] (II) Preparation of coated sulfide solid electrolyte ZrCl4-LPSC (dry ball milling coating)

[0095] 1. Weigh zirconium tetrachloride at a molar ratio of 0.01:1 to zirconium tetrachloride electrolyte, and add it together with the Li6PS5Cl sulfide solid electrolyte particles prepared in step (I) into a ball mill jar.

[0096] 2. Using agate balls as the milling medium, with a material-to-ball ratio of 1:20, a milling speed of 300 rpm, and a milling time of 4 h, coated sulfide solid electrolyte powder was obtained.

[0097] Comparative Example 5

[0098] (I) Li 5.5 PS 4.5 Cl 1.5 Preparation of (LPSC1.5) sulfide solid electrolyte particles

[0099] The preparation method is the same as step (i) in Example 3.

[0100] (II) Preparation of coated sulfide solid electrolyte ZrCl4-LPSC1.5 (wet coating)

[0101] 1. Weigh zirconium tetrachloride at a molar ratio of 0.01:1 to zirconium tetrachloride electrolyte, add anhydrous ethanol as solvent, and stir to disperse for 2 h to obtain a suspension.

[0102] 2. Add the LPSC1.5 sulfide solid electrolyte particles prepared in step (I) to the above suspension and stir for 4 h.

[0103] 3. The solvent was removed by vacuum drying at 80 °C for 12 h to obtain a coated sulfide solid electrolyte powder with an internal LPSC1.5 sulfide solid electrolyte and a ZrCl4 coating layer on the surface.

[0104] Comparative Example 6

[0105] (I) Li 5.5 PS 4.5 Cl 1.5 Preparation of (LPSC1.5) sulfide solid electrolyte particles

[0106] The preparation method is the same as step (i) in Example 2.

[0107] (II) Preparation of coated sulfide solid electrolyte ZrCl4-LPSC1.5 (dry ball milling coating)

[0108] 1. Weigh zirconium tetrachloride at a molar ratio of 0.01:1 to zirconium tetrachloride electrolyte, and add it together with the Li6PS5Cl sulfide solid electrolyte particles prepared in step (I) into a ball mill jar.

[0109] 2. Using agate balls as the milling medium, with a material-to-ball ratio of 1:20, a milling speed of 300 rpm, and a milling time of 4 h, coated sulfide solid electrolyte powder was obtained.

[0110] Experimental Example 1

[0111] The electrolyte ionic conductivity was determined using the following method.

[0112] In a glove box purged with thoroughly dried argon gas (H2O < 0.01 ppm, O2 < 0.01 ppm), the products prepared in Examples 1-3 and Comparative Examples 1-9 were placed in a tableting mold and compressed using an isostatic press at a pressure of 200 MPa for 1.5 min. After demolding, solid electrolyte tablets were obtained. The thickness of the solid electrolyte tablets was measured using a digital micrometer. Using a 10 mm diameter stainless steel disc as a blocking electrode, the solid electrolyte tablets were encapsulated using a conductivity testing kit, and EIS testing was performed using an electrochemical workstation.

[0113] The EIS test method is as follows: Apply a voltage of 50mV in the frequency range of 1 Hz to 1 MHz using the AC impedance method; calculate the ionic conductivity σ using the equation σ=L / RS, where R is the total resistance of the solid electrolyte sheet, L is the thickness of the solid electrolyte sheet, and S is the area of ​​a single surface of the solid electrolyte sheet. The test results are shown in Table 1.

[0114] Experiment Example 2

[0115] The electrochemical properties of the electrolyte were determined using the following method:

[0116] 1. Pretreatment: In an argon glove box (water / oxygen ≤ 0.1 ppm), lithium-indium were pressed together at an atomic ratio of 1:1 to prepare a Li-In anode; the products obtained in Examples 1-3 and Comparative Examples 1-9 were manually mixed with NCM811 and VGCF at a mass ratio of 29:70:1 for 20 min to prepare a composite cathode.

[0117] 2. Assembly: Weigh 70 mg of sulfide electrolyte powder and evenly spread it in the designated area of ​​the PEEK mold; start the tablet press, apply 4 t of pressure to the powder and hold for several tens of seconds to compress the powder into a dense sulfide electrolyte sheet; evenly spread 10 mg of composite cathode material on one side of the compressed sulfide electrolyte sheet, ensuring that the area covered by the cathode material is completely compatible with the effective contact area of ​​the electrolyte sheet; then start the tablet press again and apply 3 t of pressure to tightly press the composite cathode and electrolyte sheet together to form a cathode-electrolyte composite structure; use a punching tool to punch the indium foil and lithium foil respectively, where the indium foil is punched into a circle with a diameter of 10 mm and the lithium foil is punched into a circle with a diameter of 4 mm; Full cell stacking and bonding: lay the circular indium foil flat on the side of the sulfide electrolyte sheet that is not composited with the cathode, and then accurately place the circular lithium foil in the center of the indium foil, ensuring that the centers of the lithium foil, indium foil and electrolyte sheet are aligned; then apply 1 t of pressure to the overall structure inside the mold. Apply pressure and hold it for a short time to ensure that the layers of positive electrode, electrolyte, indium foil, and lithium foil adhere tightly.

[0118] 3. Testing: The battery testing system measures charge and discharge performance at 0.1-1C rate and 2.7-4.3V (vs Li) at 30℃ and 2.7-4.3V (vs Li). Cycle stability is measured at 1C rate (1C nominal is 200mAh / g). Interface stability is evaluated by comparing impedance before and after cycling.

[0119] Table 1. Ionic conductivity of sulfide solid electrolytes prepared in Examples 1-2 and Comparative Examples 3-6

[0120] sample Initial ionic conductivity Coated ionic conductivity retention rate Time consumed Example 1 4.8 mS / cm 4.4 mS / cm 91.67% 2.5h Example 2 11.9 mS / cm 9.6 mS / cm 80.00% 2.5h Comparative Example 3 4.8 mS / cm 1.7 mS / cm 35.42% 20h Comparative Example 4 4.8 mS / cm 2.5mS / cm 58.33% 5h Comparative Example 5 11.9 mS / cm 3.8 mS / cm 31.93% 20h Comparative Example 6 11.9 mS / cm 6.5 mS / cm 54.62% 5h

[0121] Figure 2 , 3The electrochemical impedance spectroscopy results for ZrCl4-LPSC series and ZrCl4-LPSC are presented, and the calculated ionic conductivity and process time are summarized in Table 1. Table 1 shows that the vaporization-sublimation coating method eliminates the need for solvents throughout the process, fundamentally avoiding the hydrolysis or solvation damage to the sulfide electrolyte by solvents and mitigating the decrease in electrolyte conductivity. Simultaneously, the elimination of mechanical ball milling avoids damage to the crystal structure of the sulfide electrolyte caused by mechanical impact, preserving its intrinsic ionic conductivity to the greatest extent. Therefore, the impact of the vaporization-sublimation coating method on conductivity is far less than that of solid-phase ball milling and liquid-phase methods. Furthermore, the operation process is simple and controllable, the time is significantly reduced compared to solid-phase and liquid-phase coating, and it requires no complex equipment, facilitating large-scale production.

[0122] Table 2 Electrochemical performance data of batteries assembled from sulfide solid electrolytes prepared in Examples 1-3 and Comparative Examples 1-6

[0123] sample Initial capacity (mAh / g) Capacity (mAh / g) after 80 cycles Capacity retention rate (%) Example 1 147.6 146.1 98.98 Example 2 155.9 149.1 95.64 Example 3 150.2 150.0 99.87 Comparative Example 1 121.1 114.4 93.92 Comparative Example 2 133.3 118.9 89.19 Comparative Example 3 127.6 124.3 97.41 Comparative Example 4 135.6 128.4 94.69 Comparative Example 5 135.8 131 96.46 Comparative Example 6 146.2 138.6 94.80

[0124] Figure 4 , 5 Tables 6 and 7 respectively show the electrochemical performance of ZrCl4-LPSC, ZrCl4-LPSC1.5, and TaCl5-LPSC1.5. The measured capacity and capacity retention are summarized in Table 2. Table 2 shows that chloride coating improves the interfacial stability between the sulfide solid electrolyte and the ternary high-voltage cathode to a certain extent, reflected in the increase in initial battery capacity and capacity retention after 80 cycles. Meanwhile, the battery assembled with electrolyte modified by the vapor-phase sublimation coating method exhibits significantly better cycle stability than those assembled by ball-milling dry coating and wet coating methods. The battery assembled with the coated electrolyte demonstrates that the vaporization-sublimation coating method eliminates the need for solvents throughout the process, fundamentally preventing the hydrolysis or solvation damage of the sulfide electrolyte by solvents. Simultaneously, the elimination of mechanical ball milling avoids damage to the crystal structure of the sulfide electrolyte from mechanical impact, maximizing the preservation of its intrinsic ion conductivity. The improvement effect on both different sulfide electrolytes indicates the universality of this method. Furthermore, it verifies that both ZrCl4 and AlCl3 coatings can improve the interfacial stability between the sulfide solid electrolyte and the ternary high-voltage cathode to a certain extent.

[0125] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A chloride-coated modified sulfide solid electrolyte of silver-germanium sulfide type, characterized in that... The electrolyte comprises a sulfide electrolyte core and a chloride coating layer encapsulating the core, with the general chemical formula Li. 7−x PS 6−x Cl x · n(MCl y Where x ranges from 1 to x to 1.5, n ranges from 0.0001 to n to 0.05, and y corresponds to the number of chlorine atoms corresponding to the valence state of element M. Specifically, MCl y When the value is FeCl3, y=3; when the value is ZrCl4, y=4; when the value is AlCl3, y=3; when the value is SbCl5, y=5; when the value is TaCl5, y=5; and when the value is NbCl5, y=5.

2. The chloride coating layer according to claim 1, characterized in that, The coating layer is a continuous phase formed by in-situ deposition on the surface of sulfide electrolyte particles, rather than a phase formed through liquid-phase reaction or mechanical mixing.

3. The chloride coating layer according to claim 1, characterized in that, The thickness of the continuously distributed coating layer is 5-50 nm.

4. A method for preparing the chloride-coated sulfide-germanium sulfide solid electrolyte according to any one of claims 1-3, characterized in that, The process includes the following steps: Step (1), main body pretreatment step: the sulfide electrolyte raw powder is dried and sieved to remove surface adsorbed water and soft agglomerates, and obtain sulfide electrolyte powder with uniform particle size distribution; Step (2), coating precursor preparation step: the chloride precursor powder is ground or sieved to make its particle size smaller than the average particle size of the sulfide electrolyte powder, so as to improve the stability of its vaporization sublimation rate; Step (3), sublimation deposition coating step: the sulfide electrolyte powder treated in step (1) is spread flat in the sample holder of the sublimation coating device, the chloride precursor powder treated in step (2) is placed in the sublimation zone of the device, and the device is vacuumed or sealed after being purged with inert gas; then the temperature of the sublimation zone and the temperature of the sample holder are controlled respectively, and a continuous chloride coating layer is formed in situ on the surface of the sulfide electrolyte main particles. No organic solvents are introduced during the entire coating process, and no mechanical ball milling steps are included. Step (4), Cooling and shaping step: The coated powder is naturally cooled or programmed cooling is performed under an inert gas atmosphere, followed by sieving or loosening to remove secondary agglomerated particles, and the chloride-coated silver-germanium sulfide solid electrolyte product is obtained.

5. The preparation method according to claim 4, characterized in that, The drying temperature in step (1) is 40-120℃; the drying time is 2-24 h; the sieve mesh size in step (1) is 100-500 mesh; the D of the chloride precursor powder in step (2) 50 It ranges from 1 to 10 μm.

6. The preparation method according to claim 4, characterized in that... Step (3) is performed under any of the following atmospheric conditions: evacuation to 10... -1 -10 3 After sealing, or in an inert gas atmosphere.

7. The preparation method according to claim 4, characterized in that... In step (3), the sublimation coating device assembly involves spreading the sieved and pretreated sulfide electrolyte powder evenly in the sample holder of the sublimation coating device, placing the chloride powder in the sublimation zone of the device, and maintaining a certain height between the sample holder and the sublimation zone; the device is then sealed. The sublimation coating device includes a sealed cavity, a temperature-controlled sublimation zone, and an adjustable height sample holder.

8. The preparation method according to claim 4, characterized in that... In step (3), the temperature of the sublimation zone is controlled to the sublimation temperature of chloride during the sublimation heating deposition process; at the same time, the temperature of the sample holder is controlled to the preset deposition temperature; after the preset temperature is maintained, the heating is stopped and the sample is allowed to cool naturally to room temperature.

9. The preparation method according to claim 4, characterized in that... In step (4), the cooled coated modified sulfide electrolyte powder is taken out and sieved under inert gas protection to remove agglomerated particles, thus obtaining the chloride-coated modified sulfide electrolyte product.

10. A battery, characterized in that, Includes the chloride-coated sulfide solid electrolyte of the silver-germanium sulfide type as described in any one of claims 1 to 9, or the chloride-coated sulfide solid electrolyte of the silver-germanium sulfide type prepared by the above preparation method.

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