Preparation method of nano lithium sulfide suitable for sulfide electrolyte system
By combining small-diameter zirconia balls and medium-speed ball milling with surface modifiers and ultrasonic-wet pre-dispersion technology, the problem of lithium sulfide particle size control was solved, achieving efficient preparation of refined lithium sulfide and improving the performance and economy of sulfide solid-state batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 杭州元威企业管理合伙企业(有限合伙)
- Filing Date
- 2026-02-04
- Publication Date
- 2026-04-14
AI Technical Summary
Existing technologies struggle to effectively control the particle size of lithium sulfide, resulting in a small contact area with P2S5, slow solid-phase reaction kinetics, and complex and costly preparation processes, making it difficult to meet the stringent requirements of sulfide solid-state batteries.
By using small-diameter zirconia balls and medium-speed ball milling combined with surface modifiers and ultrasonic-wet pre-dispersion technology, particle agglomeration is suppressed through ball milling media optimization and surface modifier regulation. After preparing a uniformly dispersed suspension, it is then spray-dried or vacuum freeze-dried to obtain refined lithium sulfide.
The lithium sulfide particle size was reduced to below 300nm, the specific surface area was increased by 5 times, energy consumption was reduced and the overall cost was reduced, and the reaction efficiency with P2S5 was improved.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-based compound preparation technology, specifically relating to a method for preparing nano-lithium sulfide suitable for sulfide electrolyte systems. Background Technology
[0002] Sulfide solid electrolytes (such as Li3PS4) have become a research hotspot in all-solid-state batteries due to their high ionic conductivity and good interfacial compatibility. Their synthesis is typically achieved through mechanical ball milling or liquid-phase reaction of Li2S with P2S5. Lithium sulfide (Li2S), as an important lithium-based compound, has broad application prospects in energy storage, solid-state batteries, and ceramic materials. Sulfide solid-state batteries have extremely stringent requirements for the raw material Li2S. As the main raw material for sulfide solid electrolytes, the optimization of its preparation process directly affects the battery's energy density, cycle life, and safety. Specifically, the preparation requirements for Li2S in sulfide solid-state batteries mainly include:
[0003] (1) Purity requirements: The purity level determines the ionic conductivity, electrochemical window and interfacial stability of solid electrolytes. Sulfide solid batteries require Li2S purity to reach above 99.99%. High-purity Li2S can reduce the adverse effects of impurities on battery performance and improve the cycle stability and service life of the battery.
[0004] (2) Particle size requirements: Li₂S is an important inorganic compound, and its particle size is one of the key factors affecting battery performance. Its performance directly determines the ionic conductivity, interfacial stability, and overall battery performance of the solid electrolyte. Smaller particle size can shorten the Li₂S… + The diffusion pathway significantly improves the rate performance of the battery; the high specific surface area provides more active sites, significantly increasing the sulfur loading and reaction rate, making it particularly suitable for high energy density batteries. Battery-grade lithium sulfide is generally required to have a particle size of nanometer (1~1000nm) or micrometer (≤10 μm) to improve the battery's ionic conductivity and energy density.
[0005] (3) Chemical stability and surface state: When Li₂S is exposed to air, a LiOH / Li₂CO₃ passivation layer easily forms on its surface, hindering ion transport. A 10 nm LiOH layer can increase the interfacial impedance by two orders of magnitude (from 10 Ω·cm² to 1000 Ω·cm²); Li + The energy barrier to penetrate the Li₂CO₃ layer is as high as 0.75 eV (compared to only 0.25 eV for pure Li₂S). Furthermore, water reacts with the sulfide electrolyte to form H₂S, therefore the water content of Li₂S must be <50 ppm.
[0006] (4) Preparation process and cost control: Battery-grade Li2S is sensitive to air and requires protection under an inert atmosphere throughout the process; it is thermodynamically unstable, and high-temperature preparation (>600℃) can easily lead to sulfur volatilization (sulfur loss rate can reach 15%), requiring precise control of the temperature window; it requires high purity of Li2S, but existing purification processes (such as zone melting) consume up to 200 kWh / kg and have an efficiency of less than 60%. The above reasons make the preparation process of Li2S complex and costly, which has become one of the important factors restricting the commercial application of sulfide solid-state batteries.
[0007] Due to the extremely stringent preparation requirements mentioned above, the synthesis and preparation of battery-grade lithium sulfide is a complex process involving multiple synthetic routes and methods, each with its own advantages and disadvantages in terms of purity, particle size control, and cost. Direct Synthesis: Under an inert atmosphere, elemental sulfur (S) and metallic lithium (Li) are mixed in a specific ratio and reacted directly at high temperatures (200-450℃) to obtain lithium sulfide. Advantages: Simple process, high product purity. Carbothermic Reduction: Under a reducing atmosphere (such as hydrogen), Li₂SO₄ or Li₂CO₃ is used as a raw material, reacting with carbon powder at high temperatures. Advantages: Inexpensive raw materials (Li₂SO₄ price < 100,000 RMB / ton), suitable for large-scale production. Hydrogen Sulfide Method: Lithium sulfide is prepared by reacting lithium compounds (LiOH, Li₂CO₃) with hydrogen sulfide gas in an anhydrous solvent. Advantages: Suitable for large-scale production, purity up to 99.9%. Organic Solvothermic Method: Lithium sulfide is prepared by mixing and reacting lithium compounds and sulfur compounds in an anhydrous solvent medium, often an organic solvent. Advantages: Simple process, controllable particle size, and low energy consumption. Chemical vapor deposition: Lithium metal is evaporated in a vacuum reaction chamber and reacted with H2S gas on a heated substrate (600℃) to deposit solid Li2S. Advantages: Purity >99.999%, dense interface.
[0008] However, the commercially available Li₂S particles obtained using the above methods currently have relatively large particle sizes (10μm~50μm). The large Li₂S particles have a small contact area with P₂S₅, resulting in slow solid-phase reaction kinetics. To reduce particle size, the traditional approach is to ball mill the large particles. However, as the ball milling time increases, impurities are easily introduced and energy consumption increases. Simply using high-speed ball milling easily leads to heat accumulation and particle agglomeration, while wet milling, although it can refine the particles, makes subsequent drying difficult. Summary of the Invention
[0009] To address the aforementioned technical problems, this invention provides a method for preparing nano-lithium sulfide suitable for sulfide electrolyte systems. This method is a Li2S refinement method that balances particle size control, dispersibility, and process feasibility. Through ball milling media optimization, surface modifier regulation, and the synergistic effect of ultrasonic-wet pre-dispersion, the particle size of lithium sulfide is reduced.
[0010] This invention is specifically achieved through the following technical solutions: A method for preparing nano-lithium sulfide suitable for sulfide electrolyte systems includes the following steps: (1) The lithium sulfide to be refined is ball-milled with a ball milling medium with a particle size of 0.1 mm to 0.5 mm and a ball milling speed of 100 rpm to 350 rpm.
[0011] It should be noted that in the ball milling process of this invention, a small-diameter zirconia ball and a medium-speed ball milling method are used. Zirconia balls with a diameter of 0.1mm to 0.5mm (high density and low wear rate) are used. The small-sized zirconia balls have more contact points per unit volume, resulting in more uniform grinding. The medium-speed ball milling (100rpm to 350rpm) is used to avoid local overheating and particle agglomeration caused by high speed.
[0012] (2) The surface modifier is used to modify the interface of the ball-milled lithium sulfide. The surface modifier is adsorbed on the surface of lithium sulfide to reduce the interfacial energy, inhibit the re-agglomeration of refined particles, and is placed in a dispersant to prepare a uniformly dispersed suspension.
[0013] It should be noted that the purpose of adding surface modifiers is to control agglomeration. Afterwards, the modified lithium sulfide is placed in a dispersant and subjected to ultrasonic treatment to initially deagglomerate and make the particles uniformly dispersed.
[0014] (3) The dispersant in the suspension is removed by spray drying or vacuum freeze drying to obtain refined lithium sulfide.
[0015] It should be noted that spray drying or vacuum freeze drying removes the dispersant, avoiding the hard agglomeration caused by traditional drying.
[0016] In a preferred embodiment of the invention, the ball-to-material ratio during ball milling is 10-20:1 to ensure a balance between sufficient collision energy and material throughput. The milling process alternates between forward and reverse rotation every 30 minutes. An external circulating cooling system (-10°C ethylene glycol solution) is connected to the milling jar. The milling time is 5-8 hours.
[0017] In a preferred embodiment of the invention, ball milling is performed in stages, with the diameter of the milling media used in each subsequent stage being smaller than that used in the previous stage. In a more preferred embodiment of the invention, two-stage ball milling is employed. The first stage initially breaks down large particles using zirconia grinding balls with a diameter of 0.5 mm, while the second stage further refines and suppresses agglomeration using zirconia grinding balls with a diameter of 0.1 mm.
[0018] In a preferred embodiment of the present invention, the mass of the surface modifier added is 0.1wt% to 1.0wt% of the mass of the ball-milled lithium sulfide.
[0019] In a preferred embodiment of the present invention, the surface modifier is one or more of lithium stearate, lithium oleate, anhydrous ethanol, silane coupling agent, toluene, dodecyl mercaptan, polyethylene glycol, polyvinylidene fluoride and polyvinyl alcohol.
[0020] In a preferred embodiment of the present invention, the dispersant is one or more of dimethyl sulfoxide, N,N-dimethylformamide, xylene, acetone, diethyl ether, dichloromethane, n-hexane, acetonitrile, petroleum ether, ethyl acetate, n-pentane, cyclohexane, tetrahydrofuran, and toluene.
[0021] In a preferred embodiment of the present invention, when preparing a uniformly dispersed suspension, ultrasonic treatment is used, with an ultrasonic frequency of 20kHz to 40kHz and an ultrasonic treatment time of 30min to 60min.
[0022] In a preferred embodiment of the present invention, the method for preparing the refined lithium sulfide includes the following steps: Under a protective gas atmosphere, Li2SO4, S powder and carbon powder were uniformly mixed and ball-milled; then the ball-milled mixture was placed in an inert atmosphere and reacted at 800℃~1200℃ for 2~4 hours; after cooling, the product was washed and dried in an inert atmosphere to obtain lithium sulfide to be refined.
[0023] Compared with the prior art, the present invention has the following beneficial effects: This invention refines particle size through optimized ball milling media, controlled surface modifiers, and synergistic ultrasonic-wet pre-dispersion. Specifically, lithium sulfide to be refined is ball-milled using small-diameter zirconia balls at a medium speed (particle size 0.1mm~0.5mm, milling speed 100rpm~350rpm). A surface modifier is used to modify the interface of the ball-milled lithium sulfide. The surface modifier adsorbs onto the lithium sulfide surface, reducing interfacial energy, inhibiting the re-agglomeration of refined particles, and preparing a uniformly dispersed suspension. The dispersant in the suspension is removed by spray drying or vacuum freeze-drying to obtain refined lithium sulfide.
[0024] Particle size control: D 50 The specific surface area is increased by more than 5 times, decreasing from 7.4 μm to below 300 nm.
[0025] Process economy: Medium-speed ball milling reduces energy consumption, requires less modifier and is recyclable, resulting in a 20% reduction in overall cost.
[0026] Therefore, this invention achieves refined lithium sulfide (Li2S) particle size through optimized ball milling process and additive control, making it suitable for the efficient synthesis of sulfide solid electrolytes (such as Li3PS4), and realizing highly efficient refinement of Li2S particles (D). 50 <300 nm), and helps to improve its reaction efficiency with P2S5. Attached Figure Description
[0027] Figure 1 This is a photograph of the Li2S product prepared in Example 4.
[0028] Figure 2 The image shows the XRD pattern of the Li2S product prepared in Example 4.
[0029] Figure 3 The particle size distribution curve of the Li2S product prepared in Example 4 is shown.
[0030] Figure 4 The particle size distribution curve of the Li2S product prepared for Comparative Example 1 is shown.
[0031] Figure 5 SEM image of the Li2S product prepared in Comparative Example 3.
[0032] Figure 6 The particle size distribution curve of the Li2S product prepared for Comparative Example 3 is shown. Detailed Implementation
[0033] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention. Unless otherwise specified, the experimental methods and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials described are commercially available.
[0034] Example 1 A method for preparing nano-lithium sulfide suitable for sulfide electrolyte systems includes the following steps: Step 1: Weigh 10.6 g (0.1 mol) Li₂SO₄, 7.0 g (0.22 mol) S powder, and 2.64 g (0.22 mol) activated carbon. Dry the Li₂SO₄, S powder, and activated carbon separately in a vacuum drying oven at 80℃ for 12 h to remove moisture. Store the dried raw materials in a glove box for later use.
[0035] Step 2: Place the weighed raw material in a ball mill jar and add zirconia balls (5 mm in diameter, ball-to-material ratio 10:1). Ball mill for 3 hours under argon protection (350 rpm, alternating forward and reverse rotation every 30 minutes). The mixture after ball milling is a uniform gray-black powder; store it in a glove box to prevent moisture absorption.
[0036] Step 3: Under the protection of argon gas, the obtained powder is placed in a calcining furnace and calcined at 850°C for 10 hours to obtain the calcined product.
[0037] Step 4: Place the calcined product in a glove box environment (argon-filled, water content less than 1 ppm), dissolve it in anhydrous ethanol, stir well, and then filter to remove insoluble matter.
[0038] Step 5: The obtained filtrate is heated and evaporated under vacuum conditions (vacuum degree better than 10 Pa, temperature controlled at 80℃) until the ethanol in the filtrate is basically completely evaporated, and crude lithium sulfide product is obtained.
[0039] Step 6: Pour the obtained lithium sulfide into a ball mill jar (250 mL volume, zirconia-lined). Add zirconia grinding balls (0.3 mm diameter, ball-to-material ratio 20:1). Seal the ball mill jar, evacuate it, and then purge it with inert gas (argon) three times to remove oxygen. Grind using a ball mill for 5 hours (300 rpm, alternating forward and reverse rotation every 30 minutes), with the ball mill jar connected to an external circulating cooling system (-10℃ ethylene glycol solution).
[0040] Step 7: Place the ground lithium sulfide powder and lithium stearate (the added mass of lithium stearate is 0.5 wt% of the mass of the ball-milled lithium sulfide) into a 500 mL beaker. Add 60 mL of anhydrous toluene and stir magnetically for 10 min to form a suspension. Sonicate the suspension for 60 min to ensure uniform particle dispersion.
[0041] Step 8: The obtained suspension is treated by spray drying (outlet air temperature 80 ℃, atomization pressure 0.20 MPa) until the liquid is completely evaporated, yielding D. 50 =972 nm Li₂S.
[0042] Example 2 A method for preparing nano-lithium sulfide suitable for sulfide electrolyte systems includes the following steps: Step 1: Weigh 10.6 g (0.1 mol) Li₂SO₄, 7.0 g (0.22 mol) S powder, and 2.64 g (0.22 mol) activated carbon. Dry the Li₂SO₄, S powder, and activated carbon separately in a vacuum drying oven at 80℃ for 12 h to remove moisture. Store the dried raw materials in a glove box for later use.
[0043] Step 2: Place the weighed raw material into a ball mill jar and add zirconia balls (5 mm in diameter, ball-to-material ratio 10:1). Ball mill for 3 hours under argon protection (350 rpm, alternating forward and reverse rotation every 30 minutes). The mixture after ball milling should be a uniform gray-black powder. Store in a glove box to prevent moisture absorption.
[0044] Step 3: Under the protection of argon gas, the obtained powder is placed in a calcining furnace and calcined at 850°C for 10 hours to obtain the calcined product.
[0045] Step 4: Place the calcined product in a glove box environment (argon-filled, water content less than 1 ppm), dissolve it in anhydrous ethanol, stir well, and then filter to remove insoluble matter.
[0046] Step 5: The obtained filtrate is heated and evaporated under vacuum conditions (vacuum degree better than 10 Pa, temperature controlled at 80℃) until the ethanol in the filtrate is basically completely evaporated, and crude lithium sulfide product is obtained.
[0047] Step 6: Pour the obtained lithium sulfide into a ball mill jar (250 mL volume, zirconia-lined). Add zirconia grinding balls (0.3 mm diameter, ball-to-material ratio 20:1). Seal the ball mill jar, evacuate it, and then purge it with inert gas (argon) three times to remove oxygen. Grind using a ball mill for 5 hours (350 rpm, alternating forward and reverse rotation every 30 minutes), with the ball mill jar connected to an external circulating cooling system (-10℃ ethylene glycol solution).
[0048] Step 7: Place the ground lithium sulfide powder and lithium stearate (0.3 wt%) into a 500 mL beaker. Add 60 mL of anhydrous toluene and stir magnetically for 10 min to form a suspension. Sonicate the suspension for 60 min to ensure uniform particle dispersion.
[0049] Step 8: The obtained suspension is treated by spray drying (outlet air temperature 80 ℃, atomization pressure 0.20 MPa) until the liquid is completely evaporated, yielding D. 50 =846 nm Li2S.
[0050] Example 3 A method for preparing nano-lithium sulfide suitable for sulfide electrolyte systems includes the following steps: Step 1: Weigh 10.6 g (0.1 mol) Li₂SO₄, 7.0 g (0.22 mol) S powder, and 2.64 g (0.22 mol) activated carbon. Dry the Li₂SO₄, S powder, and activated carbon separately in a vacuum drying oven at 80℃ for 12 h to remove moisture. Store the dried raw materials in a glove box for later use.
[0051] Step 2: Place the weighed raw material into a ball mill jar and add zirconia balls (5 mm in diameter, ball-to-material ratio 10:1). Ball mill for 3 hours under argon protection (350 rpm, alternating forward and reverse rotation every 30 minutes). The mixture after ball milling should be a uniform gray-black powder. Store in a glove box to prevent moisture absorption.
[0052] Step 3: Under the protection of argon gas, the obtained powder is placed in a calcining furnace and calcined at 850°C for 10 hours to obtain the calcined product.
[0053] Step 4: Place the calcined product in a glove box environment (argon-filled, water content less than 1 ppm), dissolve it in anhydrous ethanol, stir well, and then filter to remove insoluble matter.
[0054] Step 5: The obtained filtrate is heated and evaporated under vacuum conditions (vacuum degree better than 10 Pa, temperature controlled at 80℃) until the ethanol in the filtrate is basically completely evaporated, and crude lithium sulfide product is obtained.
[0055] Step 6: Pour the obtained lithium sulfide into a ball mill jar (250 mL volume, zirconia-lined). Add zirconia grinding balls (0.3 mm diameter, ball-to-material ratio 20:1). Seal the ball mill jar, evacuate it, and then purge it with inert gas (argon) three times to remove oxygen. Grind using a ball mill for 7 hours (250 rpm, alternating forward and reverse rotation every 30 minutes), with the ball mill jar connected to an external circulating cooling system (-10℃ ethylene glycol solution).
[0056] Step 7: Place the ground lithium sulfide powder and lithium oleate (0.5 wt%) in a 500 mL beaker. Add 60 mL of anhydrous toluene and stir magnetically for 10 min to form a suspension. Sonicate the suspension for 60 min to ensure uniform particle dispersion.
[0057] Step 8: The obtained suspension is treated by spray drying (outlet air temperature 80 ℃, atomization pressure 0.20 MPa) until the liquid is completely evaporated, yielding D. 50 =519 nm Li₂S.
[0058] Example 4 A method for preparing nano-lithium sulfide suitable for sulfide electrolyte systems includes the following steps: Step 1: Weigh 10.6 g (0.1 mol) Li₂SO₄, 7.0 g (0.22 mol) S powder, and 2.64 g (0.22 mol) activated carbon. Dry the Li₂SO₄, S powder, and activated carbon separately in a vacuum drying oven at 80℃ for 12 h to remove moisture. Store the dried raw materials in a glove box for later use.
[0059] Step 2: Place the weighed raw material into a ball mill jar and add zirconia balls (5 mm in diameter, ball-to-material ratio 10:1). Ball mill for 3 hours under argon protection (350 rpm, alternating forward and reverse rotation every 30 minutes). The mixture after ball milling should be a uniform gray-black powder. Store in a glove box to prevent moisture absorption.
[0060] Step 3: Under the protection of inert gas (argon), the obtained powder is placed in a calcining furnace and calcined at 850°C for 10 hours to obtain the calcined product.
[0061] Step 4: Place the calcined product in a glove box environment (argon-filled, water content less than 1 ppm), dissolve it in anhydrous ethanol, stir well, and then filter to remove insoluble matter.
[0062] Step 5: The obtained filtrate is heated and evaporated under vacuum conditions (vacuum degree better than 10 Pa, temperature controlled at 80℃) until the ethanol in the filtrate is basically completely evaporated, and crude lithium sulfide product is obtained.
[0063] Step 6, staged ball milling: The first stage involves preliminary crushing of large particles. The obtained lithium sulfide is poured into a ball mill jar (250 mL volume, zirconia-lined). Zirconia grinding balls (0.5 mm diameter, ball-to-particle ratio 20:1) are added. The ball mill jar is sealed, evacuated, and then purged with inert gas (argon) three times to remove oxygen. Grinding is performed using a ball mill for 3 hours (350 rpm, alternating forward and reverse rotation every 30 minutes), with the ball mill jar connected to an external circulating cooling system (-10℃ ethylene glycol solution).
[0064] The second stage further refines and suppresses agglomeration. The lithium sulfide powder ground in the previous stage is ground a second time, using zirconia grinding balls (0.1 mm in diameter, ball-to-powder ratio 20:1). The ball mill jar is sealed, evacuated, and then filled with inert gas (argon) three times to remove oxygen. Grinding is carried out using a ball mill for 5 hours (speed: 200 rpm, alternating forward and reverse rotation every 30 minutes), with the ball mill jar connected to an external circulating cooling system (-10℃ ethylene glycol solution).
[0065] Step 7: Place the ground lithium sulfide powder, lithium stearate (0.5 wt%), and silane coupling agent KH-550 (0.3 wt%) into a 500 mL beaker. Add 60 mL of anhydrous toluene and stir magnetically for 10 min to form a suspension. Sonicate the suspension for 60 min to ensure uniform particle dispersion.
[0066] Step 8: The obtained suspension is treated by spray drying (outlet air temperature 80 ℃, atomization pressure 0.20 MPa) until the liquid is completely evaporated, yielding D. 50 Li₂S with a wavelength of 298 nm is shown in the image below. Figure 1 As shown. The XRD pattern of the Li2S product is as follows. Figure 2 As shown. The particle size distribution curve of Li2S prepared in Example 4 is shown in Figure 4. Figure 3 As shown.
[0067] Comparative Example 1 Compared to Example 1, the zirconium oxide grinding balls used in the ball milling process had a larger diameter (0.8 mm).
[0068] Step 1: Weigh 10.6 g (0.1 mol) Li₂SO₄, 7.0 g (0.22 mol) S powder, and 2.64 g (0.22 mol) activated carbon. Dry the Li₂SO₄, S powder, and activated carbon separately in a vacuum drying oven at 80℃ for 12 h to remove moisture. Store the dried raw materials in a glove box for later use.
[0069] Step 2: Place the weighed raw material in a ball mill jar and add zirconia balls (5 mm in diameter, ball-to-material ratio 10:1). Ball mill for 3 hours under argon protection (350 rpm, alternating forward and reverse rotation every 30 minutes). The mixture after ball milling is a uniform gray-black powder; store it in a glove box to prevent moisture absorption.
[0070] Step 3: Under the protection of an inert gas (such as argon or nitrogen), the obtained powder is placed in a calcining furnace and calcined at 850°C for 10 hours to obtain the calcined product.
[0071] Step 4: Place the calcined product in a glove box environment (argon-filled, water content less than 1 ppm), dissolve it in anhydrous ethanol, stir well, and then filter to remove insoluble matter.
[0072] Step 5: The obtained filtrate is heated and evaporated under vacuum conditions (vacuum degree better than 10 Pa, temperature controlled at 80℃) until the ethanol in the filtrate is basically completely evaporated, and crude lithium sulfide product is obtained.
[0073] Step 6: Pour the obtained lithium sulfide into a ball mill jar (250 mL volume, zirconia-lined). Add zirconia grinding balls (0.8 mm diameter, ball-to-material ratio 20:1). Seal the ball mill jar, evacuate it, and then purge it with inert gas (argon) three times to remove oxygen. Grind using a ball mill for 5 hours (300 rpm, alternating forward and reverse rotation every 30 minutes), with the ball mill jar connected to an external circulating cooling system (-10℃ ethylene glycol solution).
[0074] Step 7: Place the ground lithium sulfide powder and lithium stearate (0.5 wt%) in a 500 mL beaker. Add 60 mL of anhydrous toluene and stir magnetically for 10 min to form a suspension. Sonicate the suspension for 60 min to ensure uniform particle dispersion.
[0075] Step 8: The obtained suspension is treated by spray drying (outlet air temperature 80 ℃, atomization pressure 0.20 MPa) until the liquid is completely evaporated, yielding D. 50 Li₂S with a particle size of 7.4 μm. The particle size distribution curve of Li₂S prepared in Comparative Example 1 is shown in the figure. Figure 4 As shown.
[0076] Comparative Example 2 Compared to Example 1, a high-speed ball mill (500 rpm) was used during ball milling.
[0077] Step 1: Weigh 10.6 g (0.1 mol) Li₂SO₄, 7.0 g (0.22 mol) S powder, and 2.64 g (0.22 mol) activated carbon. Dry the Li₂SO₄, S powder, and activated carbon separately in a vacuum drying oven at 80℃ for 12 h to remove moisture. Store the dried raw materials in a glove box for later use.
[0078] Step 2: Place the weighed raw material in a ball mill jar and add zirconia balls (5 mm in diameter, ball-to-material ratio 10:1). Ball mill for 3 hours under argon protection (350 rpm, alternating forward and reverse rotation every 30 minutes). The mixture after ball milling is a uniform gray-black powder; store it in a glove box to prevent moisture absorption.
[0079] Step 3: Under the protection of an inert gas (such as argon or nitrogen), the obtained powder is placed in a calcining furnace and calcined at 850°C for 10 hours to obtain the calcined product.
[0080] Step 4: Place the calcined product in a glove box environment (argon-filled, water content less than 1 ppm), dissolve it in anhydrous ethanol, stir well, and then filter to remove insoluble matter.
[0081] Step 5: The obtained filtrate is heated and evaporated under vacuum conditions (vacuum degree better than 10 Pa, temperature controlled at 80℃) until the ethanol in the filtrate is basically completely evaporated, and crude lithium sulfide product is obtained.
[0082] Step 6: Pour the obtained lithium sulfide into a ball mill jar (250 mL volume, zirconia-lined). Add zirconia grinding balls (0.3 mm diameter, ball-to-material ratio 20:1). Seal the ball mill jar, evacuate it, and then purge it with inert gas (argon) three times to remove oxygen. Grind using a ball mill for 5 hours (500 rpm, alternating forward and reverse rotation every 30 minutes), with the ball mill jar connected to an external circulating cooling system (-10℃ ethylene glycol solution).
[0083] Step 7: Place the ground lithium sulfide powder and lithium stearate (0.5 wt%) in a 500 mL beaker. Add 60 mL of anhydrous toluene and stir magnetically for 10 min to form a suspension. Sonicate the suspension for 60 min to ensure uniform particle dispersion.
[0084] Step 8: The obtained suspension is treated by spray drying (outlet air temperature 80 ℃, atomization pressure 0.20 MPa) until the liquid is completely evaporated, yielding D. 50 =733 nm Li2S, but the particles show obvious agglomeration.
[0085] Comparative Example 3 Compared to Example 1, no surface modifier was used.
[0086] Step 1: Weigh 10.6 g (0.1 mol) Li₂SO₄, 7.0 g (0.22 mol) S powder, and 2.64 g (0.22 mol) activated carbon. Dry the Li₂SO₄, S powder, and activated carbon separately in a vacuum drying oven at 80℃ for 12 h to remove moisture. Store the dried raw materials in a glove box for later use.
[0087] Step 2: Place the weighed raw material in a ball mill jar and add zirconia balls (5 mm in diameter, ball-to-material ratio 10:1). Ball mill for 3 hours under argon protection (350 rpm, alternating forward and reverse rotation every 30 minutes). The mixture after ball milling is a uniform gray-black powder; store it in a glove box to prevent moisture absorption.
[0088] Step 3: Under the protection of an inert gas (such as argon or nitrogen), the obtained powder is placed in a calcining furnace and calcined at 850°C for 10 hours to obtain the calcined product.
[0089] Step 4: Place the calcined product in a glove box environment (argon-filled, water content less than 1 ppm), dissolve it in anhydrous ethanol, stir well, and then filter to remove insoluble matter.
[0090] Step 5: The obtained filtrate is heated and evaporated under vacuum conditions (vacuum degree better than 10 Pa, temperature controlled at 80℃) until the ethanol in the filtrate is basically completely evaporated, and crude lithium sulfide product is obtained.
[0091] Step 6: Pour the obtained lithium sulfide into a ball mill jar (250 mL volume, zirconia-lined). Add zirconia grinding balls (0.3 mm diameter, ball-to-material ratio 20:1). Seal the ball mill jar, evacuate it, and then purge it with inert gas (argon) three times to remove oxygen. Grind using a ball mill for 5 hours (300 rpm, alternating forward and reverse rotation every 30 minutes), with the ball mill jar connected to an external circulating cooling system (-10℃ ethylene glycol solution).
[0092] Step 7: Add the ground lithium sulfide powder to 60 mL of anhydrous toluene and stir magnetically for 10 min to form a suspension. Sonicate the suspension for 60 min to ensure uniform particle dispersion.
[0093] Step 8: The obtained suspension is treated by spray drying (outlet air temperature 80 ℃, atomization pressure 0.20 MPa) until the liquid is completely evaporated, yielding D. 50 =2.3 μm Li₂S. The SEM image of the Li₂S product prepared in Comparative Example 3 is shown below. Figure 5 As shown in the figure. The particle size distribution curve of Li2S is as follows. Figure 6 As shown.
[0094] Comparative Example 4 Compared to Example 4, the diameter of the first-stage zirconia grinding wheel is smaller than that of the second-stage zirconia grinding wheel.
[0095] Step 1: Weigh 10.6 g (0.1 mol) Li₂SO₄, 7.0 g (0.22 mol) S powder, and 2.64 g (0.22 mol) activated carbon. Dry the Li₂SO₄, S powder, and activated carbon separately in a vacuum drying oven at 80℃ for 12 h to remove moisture. Store the dried raw materials in a glove box for later use.
[0096] Step 2: Place the weighed raw material into a ball mill jar and add zirconia balls (5 mm in diameter, ball-to-material ratio 10:1). Ball mill for 3 hours under argon protection (350 rpm, alternating forward and reverse rotation every 30 minutes). The mixture after ball milling should be a uniform gray-black powder. Store in a glove box to prevent moisture absorption.
[0097] Step 3: Under the protection of inert gas (argon), the obtained powder is placed in a calcining furnace and calcined at 850°C for 10 hours to obtain the calcined product.
[0098] Step 4: Place the calcined product in a glove box environment (argon-filled, water content less than 1 ppm), dissolve it in anhydrous ethanol, stir well, and then filter to remove insoluble matter.
[0099] Step 5: The obtained filtrate is heated and evaporated under vacuum conditions (vacuum degree better than 10 Pa, temperature controlled at 80℃) until the ethanol in the filtrate is basically completely evaporated, and crude lithium sulfide product is obtained.
[0100] Step 6, staged ball milling: The first stage involves preliminary crushing of large particles. The obtained lithium sulfide is poured into a ball mill jar (250 mL volume, zirconia-lined). Zirconia grinding balls (0.1 mm diameter, ball-to-particle ratio 20:1) are added. The ball mill jar is sealed, evacuated, and then purged with inert gas (argon) three times to remove oxygen. Grinding is performed using a ball mill for 3 hours (350 rpm, alternating forward and reverse rotation every 30 minutes), with the ball mill jar connected to an external circulating cooling system (-10℃ ethylene glycol solution).
[0101] In the second stage, further refinement and suppression of agglomeration were achieved. The lithium sulfide powder ground in the previous stage was ground a second time, using zirconia grinding balls (0.5 mm in diameter, ball-to-powder ratio 20:1). The ball mill jar was sealed, evacuated, and then filled with inert gas (argon) three times to remove oxygen. Grinding was carried out using a ball mill for 5 hours (speed: 200 rpm, alternating forward and reverse rotation every 30 minutes), with the ball mill jar connected to an external circulating cooling system (-10℃ ethylene glycol solution).
[0102] Step 7: Place the ground lithium sulfide powder, lithium stearate (0.5 wt%), and silane coupling agent KH-550 (0.3 wt%) into a 500 mL beaker. Add 60 mL of anhydrous toluene and stir magnetically for 10 min to form a suspension. Sonicate the suspension for 60 min to ensure uniform particle dispersion.
[0103] Step 8: The obtained suspension is treated by spray drying (outlet air temperature 80 ℃, atomization pressure 0.20 MPa) until the liquid is completely evaporated, yielding D. 50 =785 nm Li₂S.
[0104] The particle size statistics of lithium sulfide prepared in the above embodiments and comparative examples are shown in Table 1.
[0105] Table 1. Statistical data on lithium sulfide particle size prepared in the above examples and comparative examples. As shown in Table 1, in Comparative Example 1, compared to Example 1, the larger diameter of the zirconia grinding balls used during ball milling resulted in a larger product particle size, indicating that the particle size of the ball milling media has a significant impact on the product particle size. In Comparative Example 2, compared to Example 1, high-speed ball milling resulted in a smaller product particle size, but significant agglomeration occurred. Therefore, it is necessary to control the ball milling speed to simultaneously achieve small particle size and prevent agglomeration. In Comparative Example 3, compared to Example 1, the absence of a surface modifier resulted in a larger product particle size, indicating that the use of a surface modifier can effectively reduce the product particle size. In Comparative Example 4, compared to Example 4, the diameter of the zirconia grinding balls in the first stage was smaller than that in the second stage, resulting in a larger product particle size, indicating that when using staged ball milling, a larger diameter zirconia grinding ball should be used first.
[0106] As can be seen from the above results, the present invention achieves the refinement of lithium sulfide particle size through ball milling media optimization, surface modifier regulation, and the synergistic effect of ultrasonic-wet pre-dispersion. The method is simple and efficient and is suitable for further refinement of the particle size of existing commercial Li2S particles.
[0107] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, it is intended to include any modifications and variations that fall within the scope of the claims and their equivalents.
Claims
1. A method for preparing nano-lithium sulfide suitable for sulfide electrolyte systems, characterized in that, Includes the following steps: The lithium sulfide to be refined is ball-milled with a ball milling medium having a particle size of 0.1 mm to 0.5 mm and a ball milling speed of 100 rpm to 350 rpm. The interface of ball-milled lithium sulfide was modified with a surface modifier and then ultrasonicated in a dispersant to prepare a uniformly dispersed suspension. The surface modifier was used to inhibit the re-agglomeration of lithium sulfide particles. The dispersant in the suspension is removed by spray drying or vacuum freeze drying to obtain refined lithium sulfide.
2. The method for preparing nano-lithium sulfide suitable for sulfide electrolyte systems according to claim 1, characterized in that, During ball milling, a staged ball milling method is adopted, in which the diameter of the ball milling media used in the later stage is smaller than that used in the previous stage.
3. The method for preparing nano-lithium sulfide suitable for sulfide electrolyte systems according to claim 1, characterized in that, During ball milling, the ball-to-material ratio is 10~20:1, and the forward and reverse rotations alternate every 30 minutes. The ball mill jar is connected to an external circulating cooling system, and the ball milling time is 5h~8h.
4. The method for preparing nano-lithium sulfide suitable for sulfide electrolyte systems according to claim 1, characterized in that, The mass of the surface modifier added is 0.1wt% to 1.0wt% of the mass of the ball-milled lithium sulfide.
5. The method for preparing nano-lithium sulfide suitable for sulfide electrolyte systems according to claim 1, characterized in that, The surface modifier is one or more of lithium stearate, lithium oleate, anhydrous ethanol, silane coupling agent, toluene, dodecyl mercaptan, polyethylene glycol, polyvinylidene fluoride and polyvinyl alcohol.
6. The method for preparing nano-lithium sulfide suitable for sulfide electrolyte systems according to claim 1, characterized in that, The dispersant is one or more of dimethyl sulfoxide, N,N-dimethylformamide, xylene, acetone, diethyl ether, dichloromethane, n-hexane, acetonitrile, petroleum ether, ethyl acetate, n-pentane, cyclohexane, tetrahydrofuran, and toluene.
7. The method for preparing nano-lithium sulfide suitable for sulfide electrolyte systems according to claim 1, characterized in that, When preparing a uniformly dispersed suspension, ultrasonic treatment is used, with an ultrasonic frequency of 20kHz~40kHz and an ultrasonic treatment time of 30min~60min.
8. The method for preparing nano-lithium sulfide suitable for sulfide electrolyte systems according to claim 1, characterized in that, The method for preparing refined lithium sulfide includes the following steps: Under a protective gas atmosphere, Li2SO4, S powder and carbon powder were uniformly mixed and ball-milled; then the ball-milled mixture was placed in an inert atmosphere and reacted at 800℃~1200℃ for 2~4 hours; after cooling, the product was washed and dried in an inert atmosphere to obtain lithium sulfide to be refined.