A sulfide electrolyte and a method for producing the same

Abstract

The application provides a sulfide electrolyte and a preparation method thereof, and relates to the technical field of electrolytes. 6‑y‑z PS 5‑x‑z M y O x Cl 1+z Wherein, M is selected from Rb and / or Cs, 0<=x<=0.05, 0.05<=y<=0.2, 0.1<=z<=0.5. The sulfide electrolyte can adopt a method of step-by-step ball milling and step-by-step sintering, so that the performance of the sulfide electrolyte is further optimized, and the ion conductivity is higher and the air stability is better.

Description

Technical Field

[0001] This invention belongs to the field of electrolyte technology and relates to a sulfide electrolyte and its preparation method. Background Technology

[0002] Solid-state electrolytes are the core component of all-solid-state lithium-ion batteries, and their performance directly determines the battery's energy density, safety, and cycle life. Metal sulfide electrolytes have become a research hotspot and one of the solid-state electrolyte materials with practical application prospects due to their advantages such as high ionic conductivity, good mechanical processing properties, and compatibility with electrode materials. However, their poor air stability and interfacial compatibility with electrodes limit their application.

[0003] Doping modification can optimize electrolyte performance; existing doping methods include Li + Site cation doping, P 5+ Doping techniques include site-specific cation doping, halogen doping, and oxygen doping. Different doping techniques have different effects, and the same doping technique can have different effects on different types of electrolytes. Therefore, different types of electrolytes require different doping techniques.

[0004] The applicant believes that the existing doping technology for sulfide electrolytes needs further improvement. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a sulfide electrolyte and its preparation method.

[0006] The technical solution of the present invention is as follows:

[0007] A sulfide electrolyte having the chemical composition shown in formula (1), Li 6-y-z PS 5-x-z M y O x Cl 1+z (1) Where M is selected from Rb and / or Cs, 0≤x≤0.05, 0.05≤y≤0.2, 0.1≤z≤0.5.

[0008] Preferably, the value of x satisfies: 0.01≤x≤0.05.

[0009] Preferably, using the AC impedance method, the sulfide electrolyte has an ionic conductivity of not less than 4 mS / cm at 25°C.

[0010] A method for preparing a sulfide electrolyte according to any of the above embodiments, comprising: Lithium sulfide, phosphorus pentasulfide and lithium oxide are mixed and subjected to a first ball milling, a first sintering, and cooling to obtain a precursor. The precursor, lithium chloride, and alkali metal chloride are mixed and subjected to a second ball milling, a second sintering, and cooling to obtain the sulfide electrolyte. The alkali metal chloride is selected from cesium chloride and / or rubidium chloride.

[0011] Preferably, the molar ratio of lithium sulfide, phosphorus pentasulfide and lithium oxide is 1.95-1.98:0.5:0-0.05.

[0012] Preferably, the process of the first ball mill is as follows: rotation speed 400-600 r / min, time 2-4 h, and ball-to-material ratio 20-40:1.

[0013] Preferably, the first sintering process is as follows: temperature is 200-300℃, time is 2-4 h, and inert gas atmosphere.

[0014] Preferably, the weight ratio of the precursor, the lithium chloride, and the alkali metal chloride is 2.03:0.55-0.62:0.08-0.35.

[0015] Preferably, the second ball milling process is as follows: rotation speed 100-200 r / min, time 2-4 h, and ball-to-material ratio 10-20:1.

[0016] Preferably, the second sintering process is as follows: temperature 400-500℃, time 4-10 h, inert gas atmosphere.

[0017] The beneficial effects of this invention are: (1) This invention utilizes rubidium chloride and / or cesium chloride as a base on an LPSCl sulfide electrolyte composed of lithium sulfide, phosphorus pentasulfide, and lithium chloride. + and / or Cs + A larger ionic radius alters the lattice parameters and reduces the Li + This reduces the migration energy barrier, thereby significantly improving the ionic conductivity of the electrolyte.

[0018] (2) Further oxygen doping (adding lithium oxide) is carried out on the basis of rubidium chloride and / or cesium chloride doping. O atoms can partially replace the lattice positions of S atoms, and the doped Rb + and / or Cs + By working synergistically and optimizing the electrolyte structure, air stability is improved while further enhancing ionic conductivity. Attached Figure Description

[0019] Figure 1 This is a SEM image of the sulfide electrolyte obtained in Example 2. Detailed Implementation

[0020] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0021] On the one hand, the present invention proposes a sulfide electrolyte having the chemical composition shown in formula (1). Li 6-y-z PS 5-x-z M y O x Cl 1+z (1) Where M is selected from Rb and / or Cs, 0≤x≤0.05, 0.05≤y≤0.2, 0.1≤z≤0.5.

[0022] To address the issues of insufficient ionic conductivity and poor air stability inherent in LPSCl sulfide electrolytes, such as Li 5.5 PS 4.5 Cl 1.5 The ionic conductivity of the sulfide electrolyte at 25°C is approximately 5 mS / cm (AC impedance method). This invention, in one aspect, introduces Rb, which has a large ionic radius. + and / or Cs + Changing the lattice parameters reduces the Li + The migration energy barrier is reduced, thus significantly improving the ionic conductivity of the electrolyte. Using AC impedance spectroscopy, the ionic conductivity of the doped sulfide electrolyte at 25°C is no less than 5.25 mS / cm.

[0023] In some embodiments, the value of x satisfies: 0.01 ≤ x ≤ 0.05. When the value of x satisfies 0.01 ≤ x ≤ 0.05, that is, when O atoms are introduced into the LPSCl sulfide electrolyte for doping, the O atoms can partially replace the lattice positions of S atoms and interact with the doped Rb. + and / or Cs + By synergistically enhancing the effects and optimizing the electrolyte structure, air stability is improved while further increasing the ionic conductivity of the sulfide electrolyte. Furthermore, the value of x satisfies: 0.01 ≤ x ≤ 0.04.

[0024] In some embodiments, when x=0 in the sulfide electrolyte shown in formula (1) above, i.e., when it does not contain doped O atoms, the ionic conductivity (25°C) is not less than 4 mS / cm; when x>0, for example 0.01≤x≤0.05, i.e., it is doped with O atoms, the ionic conductivity (25°C) of the sulfide electrolyte shown in formula (1) above is not less than 5.5 mS / cm, and can even reach 6 mS / cm or higher. Therefore, in this invention, Rb is doped into the LPSCl sulfide electrolyte. + and / or Cs + Increased ionic conductivity; when using Rb + and / or Cs+ The multi-element doping of O atoms further improves the ionic conductivity of the electrolyte, and also significantly improves its air stability. When exposed to an environment with a dew point ≤ -40℃ for 8 hours, the ionic conductivity retention rate of the electrolyte can reach no less than 80%, or even higher.

[0025] On the other hand, the present invention also provides a method for preparing the sulfide electrolyte according to any of the above embodiments, comprising: Lithium sulfide (Li2S), phosphorus pentasulfide (P2S5), and lithium oxide (Li2O) are mixed and subjected to a first ball milling, a first sintering, and cooling to obtain a precursor. The above-mentioned precursor, lithium chloride (LiCl) and alkali metal chloride are mixed and subjected to a second ball milling and a second sintering, and then cooled to obtain a sulfide electrolyte; Alkali metal chlorides are selected from cesium chloride (CsCl) and / or rubidium chloride (RbCl).

[0026] For the aforementioned raw materials, lithium sulfide, phosphorus pentasulfide, lithium oxide, lithium chloride, and alkali metal chloride, the purity is not less than 99.9% or not less than 99.99%, and they can be directly obtained from the market.

[0027] This invention employs a stepwise ball milling and stepwise sintering process. The first step involves O atom doping, and the second step involves Rb doping. + and / or Cs + Doping can achieve uniformity in multi-element doping, which is more conducive to the doping of Rb. + and / or Cs + Furthermore, the synergistic effect of O atoms improves the ionic conductivity and air stability of the electrolyte. Additionally, for the preparation of LPSCl sulfide electrolytes described above, this invention found that adding lithium chloride in the second step, compared to adding it in the first step (along with lithium sulfide, phosphorus pentasulfide, and lithium oxide), is more beneficial for improving the uniformity of the raw materials and thus enhancing the performance of the electrolyte.

[0028] In some embodiments, the molar ratio of lithium sulfide, phosphorus pentasulfide and lithium oxide is 1.95-1.98:0.5:0-0.05. For example, the molar ratio of lithium sulfide, phosphorus pentasulfide, and lithium oxide can be any value or any value between 1.95:0.5:0, 1.95:0.5:0.02, 1.96:0.5:0.02, 1.97:0.5:0.02, 1.98:0.5:0.02, 1.95:0.5:0.03, 1.96:0.5:0.03, 1.97:0.5:0.03, 1.98:0.5:0.03, 1.95:0.5:0.04, 1.96:0.5:0.04, 1.97:0.5:0.04, 1.98:0.5:0.04, 1.96:0.5:0.05, 1.98:0.5:0.05, etc., without any particular restriction. Furthermore, the molar ratio of lithium sulfide, phosphorus pentasulfide and lithium oxide can be 1.96-1.98:0.5:0.01-0.04.

[0029] In some embodiments, the first ball milling process is as follows: rotation speed 400-600 r / min, time 2-4 h, and ball-to-material ratio 20-40:1. The relatively high rotation speed of the first ball mill ensures thorough mixing of the raw materials to form an amorphous precursor. For example, the rotation speed of the first ball mill can be 400 r / min, 500 r / min, 600 r / min, etc., the time can be 2 h, 3 h, 4 h, etc., and the ball-to-material ratio can be 20:1, 25:1, 30:1, 35:1, 40:1, etc.

[0030] In some embodiments, the first sintering process is as follows: temperature 200-300℃, time 2-4 h, in an inert gas atmosphere. A lower temperature during the first sintering allows for oxygen doping solid solution. For example, the temperature of the first sintering can be 200℃, 250℃, 300℃, etc., the time can be 2h, 3h, 4h, etc., and the inert atmosphere can be nitrogen, helium, argon, etc.

[0031] In some embodiments, the weight ratio of the precursor, lithium chloride, and alkali metal chloride is 2.03:0.55-0.62:0.08-0.35. For example, the weight ratio of the precursor, lithium chloride, and alkali metal chloride may be 2.03:0.55:0.08, 2.03:0.55:0.1, 2.03:0.55:0.15, 2.03:0.55:0.2, 2.03:0.55:0.25, 2.03:0.55:0.3, 2.03:0.55:0.35, or 2.03:0.57: 0.08, 2.03:0.57:0.1, 2.03:0.57:0.15, 2.03:0.57:0.2, 2.03:0.57:0.25, 2.03:0.57:0.3, 2.03:0.57:0.35, 2.03:0.58:0.08, 2.03:0.58:0.1, 2.03:0.58:0.15, 2 0.03:0.58:0.2, 2.03:0.58:0.25, 2.03:0.58:0.3, 2.03:0.58:0.35, 2.03:0.6:0.08, 2.03:0.6:0.1, 2.03:0.6:0.15, 2.03:0.6:0.2, 2.03:0.6:0.25, 2.03:0.6:0.3 The values ​​can be any one of the following: 2.03:0.6:0.35, 2.03:0.62:0.08, 2.03:0.62:0.1, 2.03:0.62:0.15, 2.03:0.62:0.2, 2.03:0.62:0.25, 2.03:0.62:0.3, 2.03:0.62:0.35, or any value between these values, without any particular restriction.

[0032] In some embodiments, the second ball milling process is as follows: rotation speed 100-200 r / min, time 2-4 h, and ball-to-material ratio 10-20:1. The lower rotation speed of the second ball milling can avoid excessive grain breakage during the doping process and will not affect the performance of the sulfide electrolyte, especially the ionic conductivity and air stability.

[0033] In some embodiments, the second sintering process is as follows: temperature 400-500℃, time 4-10 h, in an inert gas atmosphere. The higher temperature of the second sintering allows for better Rb... + and / or Cs + Furthermore, O atom doping forms a more uniform electrolyte structure, thereby obtaining a high-performance sulfide electrolyte.

[0034] Therefore, the preparation method of the sulfide electrolyte of the present invention adopts a two-step ball milling combined with a two-step sintering process. The first step, high-speed ball milling, ensures sufficient mixing of raw materials during the preparation of the oxygen-doped precursor, forming an amorphous precursor. Oxygen doping solid solution is then achieved through low-temperature sintering. The second step involves adding Cl... - 、Rb + / Cs + Low-speed ball milling avoids excessive grain breakage during the ball milling process, and two-step sintering achieves effective doping of O atoms and Rb atoms respectively. + and / or Cs + The uniform distribution of O atoms in multi-element doping is simple and controllable, requiring no special equipment and easy to scale up production.

[0035] The technical solutions of the present invention will be further described and explained below with reference to various embodiments.

[0036] Example 1 Preparation of precursor: Weigh the raw materials according to the molar ratio n(Li2S):n(P2S5)=2:0.5, place them in an agate ball mill jar, evacuate the jar and then introduce argon gas for protection. Set the ball-to-material ratio to 30:1 and the rotation speed to 500 r / min for 2 hours to obtain a mixed powder. Transfer the mixed powder to a quartz boat and heat it to 250℃ under an inert atmosphere. Sinter it at a constant temperature for 3 hours. After sintering, allow it to cool naturally to room temperature to obtain the precursor. Preparation of electrolyte: 2.03 g of the above precursor, 0.59 g of LiCl and 0.12 g of RbCl were weighed and placed in an agate ball mill jar. After evacuation, argon gas was introduced for protection. The ball-to-material ratio was set to 10:1, and the milling speed was 150 r / min for 3 h to obtain a composite powder. The composite powder was transferred to a quartz boat and sintered at 500 °C for 4 h under an argon atmosphere. After sintering, it was naturally cooled to room temperature, ground, and passed through a 200-mesh sieve to obtain LPSCl sulfide electrolyte. The chemical composition was determined to be Li 5.4 PS 4.5 Rb 0.1 Cl 1.5 .

[0037] The ionic conductivity (25°C) of the Rb-doped electrolyte obtained in this embodiment was measured to be 5.59 mS / cm using the AC impedance method. After exposure to an environment with a dew point ≤ -40°C for 8 hours, the retention rate of the ionic conductivity was 58.7%.

[0038] Example 2 Preparation of oxygen-doped precursor: The raw materials were weighed according to the molar ratio n(Li2S):n(P2S5):n(Li2O) = 1.97:0.5:0.03, placed in an agate ball mill jar, and after vacuuming, argon gas was introduced for protection. The ball-to-material ratio was set to 30:1, and the ball milling speed was 500 r / min for 2 h to obtain a mixed powder. The mixed powder was transferred to a quartz boat, placed in a tube furnace, and after purging the air with argon gas, the temperature was raised to 250℃ and sintered at a constant temperature for 3 h. After sintering, the mixture was naturally cooled to room temperature to obtain the oxygen-doped precursor. Preparation of multi-element doped electrolyte: 2.03 g of the above oxygen-doped precursor, 0.59 g of LiCl, and 0.12 g of RbCl were weighed and placed in an agate ball mill jar. After evacuation, argon gas was introduced for protection. The ball-to-material ratio was set to 10:1, and the ball milling speed was 150 r / min for 3 h to obtain composite powder. The composite powder was transferred to a quartz boat and heated to 500 °C under an inert atmosphere. It was sintered at this temperature for 4 h. After sintering, it was naturally cooled to room temperature, ground, and passed through a 200-mesh sieve to obtain O-Rb multi-element doped LPSCl sulfide electrolyte. The chemical composition was determined to be Li 5.4 PS 4.47 Rb 0.1 O 0.03 Cl 1.5 .

[0039] The ionic conductivity (25℃) of the O-Rb multi-element doped LPSCl sulfide electrolyte obtained in this embodiment was 6.23 mS / cm when tested by AC impedance method; after being exposed to an environment with a dew point ≤ -40℃ for 8 hours, the retention rate of ionic conductivity was 84.3%.

[0040] The SEM image of the sulfide electrolyte obtained in this embodiment is attached. Figure 1 As shown.

[0041] Comparative Example 1 The raw materials were weighed according to the molar ratio n(Li₂S):n(P₂S₅):n(LiCl) = 2:0.5:1.5 and placed in an agate ball mill jar. After evacuation, argon gas was introduced for protection. The ball-to-material ratio was set to 10:1, and the ball milling speed was 150 r / min for 3 hours to obtain composite powder. The composite powder was transferred to a quartz boat and heated to 500℃ under an inert atmosphere. It was sintered at this temperature for 4 hours. After sintering, it was naturally cooled to room temperature, ground, and passed through a 200-mesh sieve to obtain LPSCl sulfide electrolyte. The chemical composition was determined to be Li. 5.5 PS 4.5 Cl 1.5 .

[0042] The ionic conductivity (25℃) of the sulfide electrolyte obtained in this comparative example, measured by AC impedance spectroscopy, was 5.02 mS / cm. After exposure to an environment with a dew point ≤ -40℃ for 8 hours, the retention rate of the ionic conductivity was 47.4%.

[0043] Comparative Example 2 2.03 g of the oxygen-doped precursor from Example 1 and 0.64 g of LiCl were weighed and placed in an agate ball mill jar. After evacuation, argon gas was introduced for protection. The ball-to-material ratio was set to 10:1, and the milling speed was 150 r / min for 3 h to obtain a composite powder. The composite powder was transferred to a quartz boat and heated to 500 °C under an inert atmosphere. It was sintered at this temperature for 4 h. After sintering, it was naturally cooled to room temperature, ground, and passed through a 200-mesh sieve to obtain an O-doped LPSCl sulfide electrolyte. The chemical composition was determined to be Li. 5.5 PS 4.47 O 0.03 Cl 1.5 .

[0044] The ionic conductivity (25℃) of the O-doped LPSCl sulfide electrolyte obtained in this comparative example was measured by AC impedance spectroscopy and found to be 4.01 mS / cm. After exposure to an environment with a dew point ≤ -40℃ for 8 hours, the retention rate of the ionic conductivity was 75.9%.

[0045] Example 3 The above raw materials were weighed according to the molar ratio n(Li₂S):n(P₂S₅):n(Li₂O):n(LiCl):n(RbCl) = 1.97:0.5:0.03:1.4:0.1 and placed in an agate ball mill jar. After evacuation, argon gas was introduced for protection. The ball-to-material ratio was set to 10:1, and the ball milling speed was 150 r / min for 3 h to obtain a mixed powder. The mixed powder was transferred to a quartz boat and sintered at 500℃ for 4 h under an inert atmosphere. After sintering, it was naturally cooled to room temperature, ground, and passed through a 200-mesh sieve to obtain O-Rb multi-element doped LPSCl sulfide electrolyte. The chemical composition was determined to be Li 5.4 PS 4.47 Rb 0.1 O 0.03 Cl 1.5 .

[0046] The ionic conductivity (25℃) of the O-doped LPSCl sulfide electrolyte obtained in this embodiment was 5.37 mS / cm when tested by AC impedance method; after being exposed to an environment with a dew point ≤ -40℃ for 8 hours, the ionic conductivity retention rate was 71.04%.

[0047] Example 4 Preparation of oxygen-doped precursor: The raw materials were weighed according to the molar ratio n(Li2S):n(P2S5):n(Li2O)=1.96:0.5:0.04, placed in an agate ball mill jar, and after vacuuming, argon gas was introduced for protection. The ball-to-material ratio was set to 40:1, and the ball milling speed was 400 r / min for 5 h to obtain a mixed powder. The mixed powder was transferred to a quartz boat, heated to 250℃ under a nitrogen atmosphere, and sintered at a constant temperature for 3 h. After sintering, it was naturally cooled to room temperature to obtain the oxygen-doped precursor. Preparation of multi-element doped electrolyte: 2.03 g of oxygen-doped precursor, 0.55 g of LiCl, and 0.34 g of CsCl were weighed and placed in an agate ball mill jar. After evacuation, argon gas was introduced for protection. The ball-to-material ratio was set to 15:1, and the milling speed was 150 r / min for 3 h to obtain composite powder. The composite powder was transferred to a quartz boat and heated to 450 °C under a nitrogen atmosphere. It was sintered at this temperature for 6 h. After sintering, it was naturally cooled to room temperature, ground, and passed through a 200-mesh sieve to obtain O-Cs multi-element doped LPSCl sulfide electrolyte. The chemical composition was determined to be Li 5.3 PS 4.46 Cs 0.2 O 0.04 Cl 1.5 .

[0048] The ionic conductivity (25℃) of the O-Cs multi-element doped LPSCl sulfide electrolyte obtained in this embodiment was 6.49 mS / cm when tested by AC impedance method; after being exposed to an environment with a dew point ≤ -40℃ for 8 hours, the ionic conductivity retention rate was 86.21%.

[0049] Example 5 The raw materials were weighed according to the molar ratio n(Li₂S):n(P₂S₅):n(Li₂O):n(LiCl):n(CsCl) = 1.96:0.5:0.04:1.3:0.2 and placed in an agate ball mill jar. After evacuation, argon gas was introduced for protection. The ball-to-material ratio was set to 40:1, the rotation speed was 400 r / min, and the mixture was ball-milled for 5 h to obtain a mixed powder. The mixed powder was transferred to a quartz boat and heated to 450℃ under a nitrogen atmosphere. It was sintered at this temperature for 6 h. After sintering, it was naturally cooled to room temperature, ground, and passed through a 200-mesh sieve to obtain an O-Cs multi-element doped LPSCl sulfide electrolyte. The chemical composition was determined to be Li. 5.3 PS 4.46 Cs 0.2 O 0.04 Cl 1.5 .

[0050] The ionic conductivity (25℃) of the O-Cs multi-element doped LPSCl sulfide electrolyte obtained in this embodiment was 5.35 mS / cm when tested by AC impedance method; after being exposed to an environment with a dew point ≤ -40℃ for 8 hours, the ionic conductivity retention rate was 72.13%.

[0051] Example 6 Preparation of oxygen-doped precursor: The raw materials were weighed according to the molar ratio n(Li2S):n(P2S5):n(Li2O)=1.98:0.5:0.02 and placed in an agate ball mill jar. After evacuation, argon gas was introduced for protection. The ball-to-material ratio was set to 40:1 and the speed was 400 r / min for 4 h to obtain a mixed powder. The mixed powder was transferred to a quartz boat and heated to 200℃ under an inert atmosphere. It was sintered at a constant temperature for 4 h. After sintering, it was naturally cooled to room temperature to obtain the oxygen-doped precursor. Preparation of multi-element doped electrolyte: 2.03 g of the above oxygen-doped precursor, 0.55 g of LiCl, and 0.24 g of RbCl were weighed and placed in an agate ball mill jar. After evacuation, argon gas was introduced for protection. The ball-to-material ratio was set to 20:1, and the ball milling speed was 200 r / min for 2 h to obtain composite powder. The composite powder was transferred to a quartz boat and heated to 450 °C under an inert atmosphere. It was sintered at this temperature for 6 h. After sintering, it was naturally cooled to room temperature, ground, and passed through a 200-mesh sieve to obtain O-Rb multi-element doped LPSCl sulfide electrolyte. The chemical composition was determined to be Li 5.3 PS 4.48 Rb 0.2 O 0.02 Cl 1.5 .

[0052] The ionic conductivity (25℃) of the O-Rb multi-element doped LPSCl sulfide electrolyte obtained in this embodiment was 6.17 mS / cm when tested by AC impedance method; after being exposed to an environment with a dew point ≤ -40℃ for 8 hours, the ionic conductivity retention rate was 81.07%.

[0053] Example 7 The raw materials were weighed according to the molar ratio n(Li₂S):n(P₂S₅):n(Li₂O):n(LiCl):n(RbCl) = 1.98:0.5:0.02:1.3:0.2 and placed in an agate ball mill jar. After evacuation, argon gas was introduced for protection. The ball-to-material ratio was set to 30:1, the rotation speed was 500 r / min, and the mixture was ball-milled for 4 h to obtain a mixed powder. The mixed powder was transferred to a quartz boat and heated to 450℃ under an inert atmosphere. It was sintered at this temperature for 8 h. After sintering, it was naturally cooled to room temperature, ground, and passed through a 200-mesh sieve to obtain O-Rb multi-element doped LPSCl sulfide electrolyte. The chemical composition was determined to be Li 5.3 PS 4.48 Rb 0.2 O0.02 Cl 1.5 .

[0054] The ionic conductivity (25℃) of the O-Rb multi-element doped LPSCl sulfide electrolyte obtained in this embodiment was 5.31 mS / cm when tested by AC impedance method; after being exposed to an environment with a dew point ≤ -40℃ for 8 hours, the ionic conductivity retention rate was 70.95%.

[0055] Example 8 Preparation of oxygen-doped precursor: The raw materials were weighed according to the molar ratio n(Li2S):n(P2S5):n(Li2O)=1.99:0.5:0.01, placed in an agate ball mill jar, and after vacuuming, argon gas was introduced for protection. The ball-to-material ratio was set to 40:1, and the ball milling speed was 400 r / min for 4 h to obtain a mixed powder. The mixed powder was transferred to a quartz boat, heated to 200℃ under an inert atmosphere, and sintered at a constant temperature for 4 h. After sintering, it was naturally cooled to room temperature to obtain the oxygen-doped precursor. The preparation of multi-element doped electrolytes using oxygen-doped precursors with LiCl and RbCl was carried out according to the process in Example 6. O-Rb multi-element doped LPSCl sulfide electrolyte was obtained, and its chemical composition was determined to be Li... 5.3 PS 4.49 Rb 0.2 O 0.01 Cl 1.5 .

[0056] The ionic conductivity (25℃) of the O-Rb multi-element doped LPSCl sulfide electrolyte obtained in this embodiment was 5.97 mS / cm when tested by AC impedance method; after being exposed to an environment with a dew point ≤ -40℃ for 8 hours, the ionic conductivity retention rate was 80.01%.

[0057] Example 9 Preparation of oxygen-doped precursor: The raw materials were weighed according to the molar ratio n(Li2S):n(P2S5):n(Li2O)=1.96:0.5:0.04, placed in an agate ball mill jar, and after vacuuming, argon gas was introduced for protection. The ball-to-material ratio was set to 40:1, and the ball milling speed was 400 r / min for 5 h to obtain a mixed powder. The mixed powder was transferred to a quartz boat, heated to 250℃ under a nitrogen atmosphere, and sintered at a constant temperature for 3 h. After sintering, it was naturally cooled to room temperature to obtain the oxygen-doped precursor. Preparation of multi-element doped electrolyte: 2.03 g of oxygen-doped precursor, 0.615 g of LiCl, and 0.085 g of CsCl were weighed and placed in an agate ball mill jar. After evacuation, argon gas was introduced for protection. The ball-to-material ratio was set to 15:1, and the milling speed was 150 r / min for 3 h to obtain composite powder. The composite powder was transferred to a quartz boat and heated to 450 °C under a nitrogen atmosphere. It was sintered at this temperature for 6 h. After sintering, it was naturally cooled to room temperature, ground, and passed through a 200-mesh sieve to obtain O-Cs multi-element doped LPSCl sulfide electrolyte. The chemical composition was determined to be Li 5.45 PS 4.46 Cs 0.05 O 0.04 Cl 1.5 .

[0058] The ionic conductivity (25℃) of the O-Cs multi-element doped LPSCl sulfide electrolyte obtained in this embodiment was 6.04 mS / cm when tested by AC impedance method; after being exposed to an environment with a dew point ≤ -40℃ for 8 hours, the ionic conductivity retention rate was 82.74%.

[0059] As described above, the basic principles, main features, and advantages of the present invention have been shown and described. Those skilled in the art should understand that the present invention is not limited to the above embodiments, which are merely preferred embodiments and should not be construed as limiting the scope of the invention. All equivalent changes and modifications made in accordance with the scope of the patent and the description should still fall within the scope of the present invention. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A sulfide electrolyte, characterized in that, It has the chemical composition shown in formula (1) below. Li 6-y-z PS 5-x-z M y O x Cl 1+z (1) Where M is selected from Rb and / or Cs, 0≤x≤0.05, 0.05≤y≤0.2, 0.1≤z≤0.

5.

2. The sulfide electrolyte according to claim 1, characterized in that, The value of x satisfies: 0.01≤x≤0.

05.

3. The sulfide electrolyte according to claim 1 or 2, characterized in that, Using the AC impedance method, the ionic conductivity of the sulfide electrolyte at 25℃ is not less than 4 mS / cm.

4. A method for preparing a sulfide electrolyte according to any one of claims 1-3, characterized in that, include: Lithium sulfide, phosphorus pentasulfide and lithium oxide are mixed and subjected to a first ball milling, a first sintering, and cooling to obtain a precursor. The precursor, lithium chloride, and alkali metal chloride are mixed and subjected to a second ball milling, a second sintering, and cooling to obtain the sulfide electrolyte. The alkali metal chloride is selected from cesium chloride and / or rubidium chloride.

5. The method for preparing the sulfide electrolyte according to claim 4, characterized in that, The molar ratio of lithium sulfide, phosphorus pentasulfide and lithium oxide is 1.95-1.98:0.5:0-0.

05.

6. The method for preparing the sulfide electrolyte according to claim 4, characterized in that, The first ball milling process is as follows: rotation speed 400-600 r / min, time 2-4 h, and ball-to-material ratio 20-40:

1.

7. The method for preparing the sulfide electrolyte according to claim 4, characterized in that, The first sintering process is as follows: temperature is 200-300℃, time is 2-4 h, and inert gas atmosphere.

8. The method for preparing the sulfide electrolyte according to claim 4, characterized in that, The weight ratio of the precursor, the lithium chloride, and the alkali metal chloride is 2.03:0.55-0.62:0.08-0.

35.

9. The method for preparing the sulfide electrolyte according to claim 4, characterized in that, The second ball milling process is as follows: rotation speed 100-200 r / min, time 2-4 h, and ball-to-material ratio 10-20:

1.

10. The method for preparing the sulfide electrolyte according to claim 4, characterized in that, The second sintering process is as follows: temperature 400-500℃, time 4-10 h, inert gas atmosphere.

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