Preparation method for improving surface interface stability of sulfide solid electrolyte and lithium metal

Abstract

The invention provides a preparation method for improving the interface stability of a sulfide solid electrolyte and a lithium metal surface, which comprises the following steps of: modifying the interface of the sulfide solid electrolyte and the lithium metal through N-butyl-N-methylpiperidine bis (fluorosulfonyl) imine salt ionic liquid, and generating a layer of compact solid electrolyte interface film (SEI) on the interface in situ; the ionic liquid with certain rheological property can permeate into sulfide solid electrolyte crystal grains, the cycling stability of the material is improved, precursor particles can be better dispersed through the ball-milling dispersing agent, in the subsequent battery preparation process, uniform mixing and reaction of the material are facilitated, and the service life of the material is prolonged. Therefore, key performance indexes such as ionic conductivity, charge-discharge performance and cycling stability of the sulfide solid-state battery are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sulfide solid electrolyte preparation, and in particular relates to a preparation method for improving the interface stability between a sulfide solid electrolyte and a lithium metal surface. Background Art

[0002] Sulfide solid electrolytes have the advantages of high ionic conductivity, low interfacial resistance, a wide electrochemical stability window and good processing performance, but they have problems such as poor air stability and less than ideal compatibility with cathode materials, which limit their large-scale application.

[0003] Patent CN118970158A discloses a method for preparing a sulfide solid electrolyte with good environmental stability, which includes the following steps: S1: weighing lithium sulfide, tin disulfide and phosphorus pentasulfide raw materials, and sequentially subjecting them to high-energy ball milling, heat treatment and post-treatment operations to prepare a sulfide solid electrolyte powder; S2: according to the chemical formula LiMO3, where M is a pentavalent transition metal element, weighing lithium salt and transition metal salt and dispersing them in a solvent to prepare a mixed solution, adding a complexing agent to react to obtain a sol; S3: spin-coating the sol on the surface of the solid electrolyte and aging it under constant temperature conditions to form a gel; S4: drying and high-temperature annealing treatment to obtain a sulfide solid electrolyte with good environmental stability.

[0004] Existing sulfide solid electrolytes still have problems such as poor cycle stability and low ionic conductivity, so the materials need to be further optimized and improved. The addition of ionic liquids can increase the ion concentration and migration rate in the electrolyte, thereby improving the ionic conductivity of the sulfide solid electrolyte and improving the charge and discharge performance of the battery. Ionic liquids are salts composed of anions and cations that are liquid at room temperature or near room temperature. They have unique properties such as low vapor pressure, low volatility, non-flammability, high thermal stability, and a wide electrochemical window, and are widely used in the field of electrochemistry. Summary of the Invention

[0005] The present invention aims to provide a preparation method for improving the surface stability of a sulfide solid electrolyte and lithium metal. A dense solid electrolyte interface (SEI) is generated in situ at the interface. An ionic liquid with defined rheological properties can penetrate into the interior of the sulfide solid electrolyte grains, improving the material's cycling stability. The ball milling dispersant further disperses the precursor particles, facilitating uniform mixing and reaction of the materials during subsequent battery preparation, thereby enhancing key performance indicators of the sulfide solid-state battery, such as ionic conductivity, charge-discharge performance, and cycling stability.

[0006] The technical solution of the present invention is: a preparation method for improving the surface stability of the sulfide solid electrolyte and lithium metal, characterized by comprising the following steps:

[0007] A. Lithium sulfide, germanium sulfide, phosphorus pentasulfide and a ball milling dispersant are weighed in a certain proportion and placed in a ball mill for high-energy ball milling. The speed and time are set, and the ball-milled powder is cold-pressed into a thin sheet of fixed thickness under a certain pressure. The sheet is then placed in a quartz tube with one end sealed. The quartz tube is evacuated and the open end is sealed with an oxyhydrogen flame. The sealed quartz tube is sintered at a high temperature. After the temperature is naturally cooled to room temperature, the product sulfide solid electrolyte is obtained.

[0008] B. A certain amount of N-butyl-N-methylpiperidinium bis(fluorosulfonyl)imide salt ionic liquid is coated on the surface of the sulfide solid electrolyte and the lithium metal.

[0009] C. Assemble into Li / / LFP batteries and test their discharge capacity, cycle performance and ionic conductivity at a current density of 0.2C.

[0010] As a preferred technical solution of the present invention, it is characterized in that: in step A, the mass ratio of the lithium sulfide, germanium sulfide, phosphorus pentasulfide raw materials and ball milling dispersant is 183-275:68-205:111-333:10-30.

[0011] As a preferred technical solution of the present invention, it is characterized in that: in step A, the preparation method of the ball milling dispersant is as follows:

[0012] Step 1: In a reaction vessel, add 17-34 parts by weight of a copolymer of allyl glycidyl ether and ethylene glycol (CAS: 41630-20-0), 19-38 parts of N-(3-aminopropyl)diethanolamine, 2-5 parts of tetramethylguanidine as a catalyst, and 200-240 parts of toluene as a solvent. The reaction temperature is controlled at 62-74°C and the reaction is continued for 30-60 minutes.

[0013] Step 2: Add 0.2-0.7 parts of zinc maleate (CAS No. 7344-42-5) to the above reaction system, maintain the reaction temperature at 62-74°C, and react for 100-160 minutes. After the reaction is completed, remove the toluene by vacuum distillation to obtain a ball mill dispersant for grinding sulfide solid-state battery precursors.

[0014] As a preferred technical solution of the present invention, it is characterized in that: in step A, the rotation speed of the ball mill is 500-800 rpm / min.

[0015] As a preferred technical solution of the present invention, it is characterized in that: in step A, the ball milling time is 10-50 minutes.

[0016] As a preferred technical solution of the present invention, it is characterized in that: in step A, the sulfide solid electrolyte precursor is placed in a stainless steel mold at a pressure of 300-500 MPa.

[0017] As a preferred technical solution of the present invention, it is characterized in that: in step A, the powder is pressed into round tablets with a thickness of 100-300 μm using a tablet press.

[0018] As a preferred technical solution of the present invention, it is characterized in that: in step A, the vacuum is pumped to 10 -2 ~10 -4 Pa.

[0019] As a preferred technical solution of the present invention, it is characterized in that: in step A, the sintering temperature is set to 350-650°C.

[0020] As a preferred technical solution of the present invention, it is characterized in that: in step A, the sintering time is 5-10 hours.

[0021] As a preferred technical solution of the present invention, it is characterized in that: in step B, the added mass parts of the N-butyl-N-methylpiperidinium bis(fluorosulfonyl)imide salt ionic liquid is 5-15 parts.

[0022] 1. Reaction Mechanism

[0023] 1. First step: The epoxy groups in the copolymer of allyl glycidyl ether and ethylene glycol undergo a ring-opening addition reaction with the amino groups in N-(3-aminopropyl)diethanolamine, catalyzed by tetramethylguanidine. The active hydrogen atoms of the amino groups attack the carbon atoms of the epoxy groups, opening the epoxy ring and forming a new chemical bond, thus connecting the two molecules.

[0024] 2. The second step reaction: zinc maleate undergoes amino-ene addition reaction with the amino group in the N-(3-aminopropyl)diethanolamine molecule to further modify the molecular structure and optimize the performance of the dispersant.

[0025] 2. Technical Effect

[0026] 1. Improved dispersion performance: Through specific molecular design and reaction steps, the prepared ball mill dispersant can effectively reduce the agglomeration between particles during the grinding process of sulfide solid-state battery precursors, making the precursor particles evenly dispersed in the grinding medium, thereby improving grinding efficiency and effect.

[0027] 2. Improve battery performance: Since ball milling dispersants can better disperse the precursor particles, they are conducive to the uniform mixing and reaction of materials in the subsequent battery preparation process, thereby improving key performance indicators of sulfide solid-state batteries such as ionic conductivity, charge and discharge performance, and cycle stability. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to specific embodiments.

[0029] Example 1

[0030] A preparation method for improving the surface stability of a sulfide solid electrolyte and a lithium metal surface, characterized by comprising the following steps:

[0031] A. Material synthesis: 183 g lithium sulfide, 68 g germanium sulfide, 111.1 g phosphorus pentasulfide, and 10 g ball milling dispersant were weighed and placed in a ball mill for high-energy ball milling at a speed of 500 / min for 4 h. The milled powder was cold pressed into a 100 μm thick sheet at a pressure of 300 MPa, and then placed in a quartz tube sealed at one end. The quartz tube was vacuumed to 10 -2 Pa, and seal the open end with a hydrogen-oxygen flame, sinter the sealed quartz tube at 350 ° C for 5 hours, and after the temperature is naturally cooled to room temperature, the product sulfide solid electrolyte can be obtained.

[0032] The preparation method of the ball milling dispersant is as follows: Step 1: In a reaction vessel, 17g of a copolymer of allyl glycidyl ether and ethylene glycol (CAS: 41630-20-0) and 19g of N-(3-aminopropyl) diethanolamine are added by weight, 2g of tetramethylguanidine is used as a catalyst, 200g of toluene is used as a solvent, the reaction temperature is controlled at 62°C, and the reaction is continued for 30 minutes. Step 2: In the above reaction system, 0.2g of zinc maleate (CAS No.: 7344-42-5) is continued to be added, the reaction temperature is maintained at 62°C, and the reaction time is 100 minutes. After the reaction is completed, the toluene is removed by vacuum distillation to finally obtain a ball milling dispersant for grinding sulfide solid-state battery precursors.

[0033] B. 5 g of N-butyl-N-methylpiperidinium bis(fluorosulfonyl)imide salt ionic liquid was coated on the solid electrolyte and the lithium metal surface.

[0034] C. The assembled Li / / LFP battery was tested to have a discharge capacity of 151.3 mAh / g at a current density of 0.2C, a capacity retention rate of 85.6% after 100 cycles, and an ionic conductivity of 0.0019 S / cm.

[0035] Example 2

[0036] A preparation method for improving the surface stability of a sulfide solid electrolyte and a lithium metal surface, characterized by comprising the following steps:

[0037] A. Material synthesis: 229 g lithium sulfide, 136 g germanium sulfide, 222 g phosphorus pentasulfide, and 20 g ball milling dispersant were weighed and placed in a ball mill for high-energy ball milling at a speed of 650 rpm for 8 h. The milled powder was cold pressed into a 150 μm thick sheet at a pressure of 400 MPa, and then placed in a quartz tube sealed at one end. The quartz tube was vacuumed to 10 -3 Pa, and seal the open end with a hydrogen-oxygen flame, sinter the sealed quartz tube at 550 ° C for 8 hours, and after the temperature is naturally cooled to room temperature, the product sulfide solid electrolyte can be obtained.

[0038] The preparation method of the ball mill dispersant is

[0039] Step 1: In a reaction vessel, 27 g of a copolymer of allyl glycidyl ether and ethylene glycol (CAS: 41630-20-0) and 30 g of N-(3-aminopropyl)diethanolamine were added by weight, along with 3.5 g of tetramethylguanidine as a catalyst and 220 g of toluene as a solvent. The reaction temperature was controlled at 68° C. and the reaction was continued for 45 minutes.

[0040] Step 2: Add 0.5g of zinc maleate (CAS No. 7344-42-5) to the above reaction system, maintain the reaction temperature at 68°C, and react for 130 minutes. After the reaction is completed, remove the toluene by vacuum distillation to obtain a ball mill dispersant for grinding sulfide solid-state battery precursors.

[0041] B. 10 g of N-butyl-N-methylpiperidinium bis(fluorosulfonyl)imide salt ionic liquid was coated on the solid electrolyte and the lithium metal surface.

[0042] C. Assembled into a Li / / LFP battery, the discharge specific capacity at a current density of 0.2C was tested to be 154.8 mAh / g, the capacity retention rate after 100 cycles was 89.9%, and the ionic conductivity was 0.0032 S / cm.

[0043] Example 3

[0044] A preparation method for improving the surface stability of a sulfide solid electrolyte and a lithium metal surface, characterized by comprising the following steps:

[0045] A. Material synthesis: 275 g lithium sulfide, 205 g germanium sulfide, 333 g phosphorus pentasulfide, and 30 g ball milling dispersant were weighed and placed in a ball mill for high-energy ball milling at a speed of 850 rpm for 12 h. The milled powder was cold pressed into a 200 μm thick sheet at a pressure of 500 MPa, and then placed in a quartz tube sealed at one end. The quartz tube was vacuumed to 10 -4 Pa, and seal the open end with a hydrogen-oxygen flame, sinter the sealed quartz tube at 650 ° C for 10 hours, and after the temperature is naturally cooled to room temperature, the product sulfide solid electrolyte can be obtained.

[0046] The preparation method of the ball mill dispersant is

[0047] Step 1: In a reaction vessel, 34 g of a copolymer of allyl glycidyl ether and ethylene glycol (CAS: 41630-20-0) and 38 g of N-(3-aminopropyl)diethanolamine were added by weight, along with 5 g of tetramethylguanidine as a catalyst and 240 g of toluene as a solvent. The reaction temperature was controlled at 74° C. and the reaction was continued for 60 minutes.

[0048] Step 2: Add 0.7 g of zinc maleate (CAS No. 7344-42-5) to the above reaction system, maintain the reaction temperature at 74°C, and react for 160 minutes. After the reaction is completed, remove the toluene by vacuum distillation to obtain a ball mill dispersant for grinding sulfide solid-state battery precursors.

[0049] B. 15 g of N-butyl-N-methylpiperidinium bis(fluorosulfonyl)imide salt ionic liquid was coated on the solid electrolyte and the lithium metal surface.

[0050] C. The assembled Li / / LFP battery was tested to have a discharge capacity of 159.9 mAh / g at a current density of 0.2C, a capacity retention rate of 94.6% after 100 cycles, and an ionic conductivity of 0.0048 S / cm.

[0051] Comparative Example 1

[0052] A preparation method for improving the surface stability of a sulfide solid electrolyte and a lithium metal surface, characterized by comprising the following steps:

[0053] A. Material synthesis: 183 g lithium sulfide, 68 g germanium sulfide, and 111.1 g phosphorus pentasulfide were weighed and placed in a ball mill for high-energy ball milling at a speed of 500 / min for 4 h. The milled powder was cold-pressed into a 100 μm thick sheet at a pressure of 300 MPa. The sheet was then placed in a quartz tube sealed at one end and vacuumed to 10 -2Pa, and seal the open end with a hydrogen-oxygen flame, sinter the sealed quartz tube at 350 ° C for 5 hours, and after the temperature is naturally cooled to room temperature, the product sulfide solid electrolyte can be obtained.

[0054] B. 5 mg of N-butyl-N-methylpiperidinium bis(fluorosulfonyl)imide salt ionic liquid was coated on the solid electrolyte and the lithium metal surface.

[0055] C. The assembled Li / / LFP battery was tested to have a discharge capacity of 142.4 mAh / g at a current density of 0.2C, a capacity retention rate of 79.7% after 100 cycles, and an ionic conductivity of 0.0011 S / cm.

Claims

1. A preparation method for improving the surface stability of the sulfide solid electrolyte and lithium metal surface, characterized in that The following steps are involved: A. Lithium sulfide, germanium sulfide, phosphorus pentasulfide and a ball milling dispersant are weighed in a certain proportion and placed in a ball mill for high-energy ball milling. The speed and time are set, and the ball-milled powder is cold-pressed into a thin sheet of fixed thickness under a certain pressure. The sheet is then placed in a quartz tube with one end sealed. The quartz tube is evacuated and the open end is sealed with an oxyhydrogen flame. The sealed quartz tube is sintered at a high temperature. After the temperature is naturally cooled to room temperature, the product sulfide solid electrolyte is obtained. B. A certain amount of N-butyl-N-methylpiperidinium bis(fluorosulfonyl)imide salt ionic liquid is coated on the surface of the sulfide solid electrolyte and the lithium metal. C. Assemble into Li / / LFP batteries and test their discharge specific capacity, cycle performance and ionic conductivity at a current density of 0.2C.

2. The method for improving the surface stability of a sulfide solid electrolyte and lithium metal according to claim 1, wherein: In step A, the mass ratio of the lithium sulfide, germanium sulfide, phosphorus pentasulfide raw materials, and ball milling dispersant is 183-275:68-205:111-333:10-30.

3. The method for improving the surface stability of the sulfide solid electrolyte and lithium metal according to claim 1, characterized in that: In step A, the preparation method of the ball mill dispersant is as follows: step 1: in a reaction container, 17-34 parts by weight of a copolymer of allyl glycidyl ether and ethylene glycol (CAS: 41630-20-0) and 19-38 parts of N-(3-aminopropyl)diethanolamine are added, 2-5 parts of tetramethylguanidine as a catalyst, and 200-240 parts of toluene as a solvent are added. The reaction temperature is controlled at 62-74° C. and the reaction is continued for 30-60 minutes. Step 2: Add 0.2-0.7 parts of zinc maleate (CAS No. 7344-42-5) to the above reaction system, maintain the reaction temperature at 62-74°C, and react for 100-160 minutes. After the reaction is completed, remove the toluene by vacuum distillation to obtain a ball mill dispersant for grinding sulfide solid-state battery precursors.

4. The method for improving the surface stability of a sulfide solid electrolyte and lithium metal according to claim 1, wherein: In step A, the ball mill rotates at a speed of 500-800 rpm.

5. The method for improving the surface stability of the sulfide solid electrolyte and lithium metal according to claim 1, characterized in that: In step A, the ball milling time is 10-50 min.

6. The method for improving the surface stability of a sulfide solid electrolyte and lithium metal according to claim 1, characterized in that: In step A, the sulfide solid electrolyte precursor is placed in a stainless steel mold at a pressure of 300-500 MPa.

7. The method for improving the surface stability of the sulfide solid electrolyte and lithium metal according to claim 1, characterized in that: In step A, the powder is pressed into round tablets with a thickness of 100-300 μm using a tablet press.

8. The method for improving the surface stability of the sulfide solid electrolyte and lithium metal according to claim 1, characterized in that: In step A, the vacuum is pumped to 10 -2 ~10 -4 Pa.

9. The method for improving the surface stability of the sulfide solid electrolyte and lithium metal according to claim 1, characterized in that: In step A, the sintering temperature is set to 350-650°C.

10. The method for improving the surface stability of the sulfide solid electrolyte and lithium metal according to claim 1, characterized in that: In step A, the sintering time is 5-10 hours.

11. The method for improving the surface stability of the sulfide solid electrolyte and lithium metal according to claim 1, characterized in that: In step B, the added mass proportion of the N-butyl-N-methylpiperidinium bis(fluorosulfonyl)imide salt ionic liquid is 5-15 parts.