A composite sulfide solid electrolyte material and its preparation method and application

Abstract

This invention belongs to the field of new energy materials technology and specifically discloses a composite sulfide solid electrolyte material, its preparation method, and application. The preparation method comprises the following steps: S1. Mixing a sulfide electrolyte precursor, thiolated modified CNF, and a solvent in proportion and ball milling to obtain a mixed slurry; the mass ratio of the sulfide electrolyte precursor, thiolated modified CNF, and solvent (p-xylene) is (50-95):(5-50):(100-200); S2. Applying the mixed slurry to a substrate and drying the coated substrate to remove the solvent; S3. Heat-treating the dried substrate under a protective atmosphere; and S4. Densifying the heat-treated substrate by mechanical pressing to obtain the composite sulfide solid electrolyte material. The method utilizes thiolated modified CNF as a modifier to improve the performance of the solid electrolyte material.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy materials, and in particular to a composite sulfide solid electrolyte material, a preparation method and applications thereof. Background Art

[0002] With the continuous growth of energy demand and increasingly severe environmental problems, the development of energy storage devices with high energy density, high safety, and long life has become an urgent need. Solid-state batteries, which use solid electrolytes instead of traditional liquid electrolytes, offer advantages such as improved safety, a wider electrochemical window, and higher energy density, and are considered the development direction of next-generation energy storage devices. However, solid-state electrolyte materials still face several challenges.

[0003] Solid electrolyte systems mainly include sulfides, oxides and polymers. Among them, sulfide electrolytes have high ionic conductivity (10 -3 ~10 -2 S / cm) has become a research hotspot, but its lack of intrinsic mechanical strength leads to two core problems: first, lithium dendrites easily penetrate the electrolyte layer and cause short circuits; second, the electrode / electrolyte interface produces microcracks due to volume changes during cycling. Existing strengthening strategies all have significant drawbacks: although oxide composites can increase strength to 1.2 GPa, the heterogeneous interface causes a 60% decrease in ionic conductivity; although polymer composite systems have good ductility, they are limited by room temperature ionic conductivity <10 -4 S / cm. Therefore, the most promising electrolyte system at present is sulfide solid electrolyte.

[0004] Nanocellulose, due to its nanoscale size effects, exhibits excellent properties in a variety of fields, including material reinforcement, biomedicine, and energy storage. Its unique structure and performance characteristics have made it a research hotspot in materials science. The high specific modulus and strength of nanocellulose enable the construction of three-dimensional reinforced composite solid electrolyte networks. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a composite sulfide solid electrolyte material and a preparation method and application thereof.

[0006] The present invention first performs primary ball milling on the sulfide precursor to optimize its particle size distribution and reaction activity, and then introduces thiolated modified CNF for second-stage ball milling. The buffering effect of the liquid medium is used to regulate the aspect ratio and dispersion uniformity of the CNF, thereby achieving efficient dispersion of the nano-reinforced phase and cross-scale structural regulation; and constructing a three-dimensional interpenetrating network skeleton.

[0007] The object of the present invention is achieved through the following technical solutions:

[0008] <First Aspect>

[0009] The present invention provides a method for preparing a composite sulfide solid electrolyte material, comprising the following steps:

[0010] S1. Mixing a sulfide electrolyte precursor, thiolated modified CNF, and a solvent (such as p-xylene) in proportion and ball milling to obtain a mixed slurry; the mass ratio of the sulfide electrolyte precursor, thiolated modified CNF, and solvent is (50-95):(5-50):(100-200);

[0011] S2, coating the mixed slurry on a substrate, and drying the coated substrate to remove the solvent;

[0012] S3. Mechanically pressing the dried substrate under a protective atmosphere to densify the substrate;

[0013] S4. heat-treating the mechanically pressed substrate under a protective atmosphere to obtain a composite sulfide solid electrolyte material;

[0014] In step S1, the method for preparing thiolated modified CNF comprises the following steps:

[0015] 1) High-pressure homogenization of nanocellulose (CNF) and 3-mercaptopropionic acid (MPA) at a molar ratio of 1:1-10; pressure 3-10 Bar, temperature 25-60°C, time 4-7 hours;

[0016] 2) The material treated in step 1) is subjected to a heat treatment to obtain thiolated modified CNF at a temperature of 50-70° C. for 5-20 h.

[0017] In step S1, the parameters of the ball milling treatment are: a ball-to-material ratio of 15-20:1, a rotation speed of 300-500 rpm, and a ball milling time of 15-20 h.

[0018] The average diameter of the thiolated modified CNF is 70-120 nm, and a three-dimensional interpenetrating network structure is formed with a sulfide electrolyte precursor through ball milling (wet ball milling).

[0019] Here, wet ball milling refers to a mechanical processing process in which solid materials are crushed, mixed and dispersed by the impact, friction and shearing action of grinding balls (such as ceramic balls, metal balls, etc.) in the presence of a liquid medium (solvent).

[0020] In step S2, the substrate is a copper strip with a thickness of 10-20 μm, the coating process is carried out under an inert atmosphere, the drying temperature after coating is 70-80° C., and the drying time is 5-6 hours.

[0021] In step S4, the heat treatment is performed under an inert atmosphere at a temperature of 120-300° C. for 1-5 hours.

[0022] In step S3, the mechanical pressing is a roller pressing process, the roller pressing temperature is 100-200° C., and the pressure is 15-30 MPa.

[0023] In step S1, the sulfide electrolyte precursor is a mixture of Li2S and P2S5 obtained by vibration ball milling, and the mass ratio of Li2S to P2S5 is 1:1.61~1.70; the vibration ball milling conditions are: vibration frequency of 1500~2000 rpm, ball-to-material ratio of 20:1, and ball milling time of 20-30h.

[0024] The particle size of the sulfide electrolyte precursor powder is micron-sized; the particle size is 100~500μm.

[0025] The ball mill jar and grinding balls are made of zirconium oxide.

[0026] <Second Aspect>

[0027] The present invention also provides a composite sulfide solid electrolyte material prepared by the above-mentioned preparation method.

[0028] The present invention pre-treats nanocellulose (CNF) to obtain thiolated modified CNF: ; (1000 ≤ n ≤ 10000).

[0029] The high pressure homogenizer is a Holder brand, HD-HP10 model high pressure homogenizer.

[0030] As an embodiment, the slurry is mixed using a roller mill (Miqi horizontal DMS-4) or a shear mill for 10 to 15 hours.

[0031] <Third Aspect>

[0032] The application of the composite sulfide solid electrolyte material in all-solid-state soft-pack batteries also falls within the protection scope of the present invention.

[0033] The all-solid-state soft-pack battery includes a positive electrode, a negative electrode, and an electrolyte membrane prepared from the composite sulfide solid electrolyte material, wherein the positive electrode material is NCM811, and the negative electrode is lithium metal or lithium-indium alloy.

[0034] As one embodiment, the negative electrode comprises lithium metal or a lithium metal composite.

[0035] As an embodiment, the positive electrode comprises NCM811.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) Better interfacial compatibility: By introducing modified CNF into the sulfide solid electrolyte, the unique surface modification technology constructs a stable chemical bonding interface, significantly reducing the electrode / electrolyte contact impedance. Through molecular-level structural regulation, the interfacial side reactions and structural degradation during the cycle are effectively suppressed.

[0038] (2) Enhanced mechanical properties: The introduction of modified CNF can enhance the mechanical strength and toughness of the composite solid electrolyte membrane, making it more resistant to volume changes during the charge and discharge process of solid-state batteries.

[0039] (3) Higher electrochemical stability: Modified CNF can act as a stabilizer to improve the electrochemical stability of solid electrolytes and extend the life of solid-state batteries.

[0040] (4) Lower costs and resource sustainability: Using renewable biomass-based nanomaterials as key components significantly reduces raw material costs while improving performance. Their natural biodegradability also reduces the environmental impact of their entire life cycle, meeting the needs of a low-carbon economic transition. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0042] Figure 1 This is a scanning electron microscope photograph of the Li-PS composite sulfide solid electrolyte membrane modified with thiol-modified CNF prepared in Example 1. DETAILED DESCRIPTION

[0043] The present invention will be described in detail below with reference to the examples. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that those skilled in the art may make several adjustments and improvements without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0044] Preparation Example 1 Preparation of thiolated modified CNF

[0045] 1. CNF and 3-mercaptopropionic acid (MPA) were mixed in an air environment at a molar ratio of 1:5 and homogenized for 5 h using a high-pressure homogenizer at 60 °C, 10 Bar, and 120 L / h to obtain a colloidal solution.

[0046] 2. The colloidal solution was reacted at 60 °C for 10 h in an air environment to obtain thiolated modified CNF with an average diameter of 70 nm.

[0047] Preparation Example 2 Preparation of Thiol-Modified CNF

[0048] 1. CNF and 3-mercaptopropionic acid (MPA) were mixed in an air environment at a molar ratio of 1:8 and homogenized for 5 h using a high-pressure homogenizer at 60 °C, 10 Bar, and 120 L / h to obtain a colloidal solution.

[0049] 2. The colloidal solution was reacted at 60 °C for 10 h in an air environment to obtain thiolated modified CNF with an average diameter of 120 nm.

[0050] Preparation Example 3 Preparation of sulfide electrolyte precursor

[0051] Under an inert atmosphere, Li2S and P2S5 with a mass ratio of 1:1.65 were loaded into a zirconia ball mill together with 10mm zirconia grinding balls and subjected to high-energy mechanical grinding for 20 hours in a vibrating ball mill, wherein the ball-to-material ratio was 20:1, the amplitude was 5 mm, and the vibration frequency was 1800 rpm, to prepare a sulfide electrolyte precursor.

[0052] Comparative Preparation Example 1

[0053] The difference between this comparative preparation example and preparation example 1 is:

[0054] In step 1, 3-mercaptopropionic acid (MPA) was replaced with mercaptopropyltrimethoxysilane (MPTMS).

[0055] Step 2 is the same as that in Preparation Example 1, and mercaptopropyltrimethoxysilane-modified CNF with an average diameter of 70 nm is obtained.

[0056] Comparative Preparation Example 2

[0057] The difference between this comparative preparation example and preparation example 1 is:

[0058] In step 1, CNFs are replaced with carbon nanotubes.

[0059] Step 2 is the same as that in Preparation Example 1, and thiol-modified carbon nanotubes with an average diameter of are obtained.

[0060] Example 1

[0061] This embodiment provides a method for preparing a Li-PS composite sulfide solid electrolyte membrane modified by thiolation-modified CNF.

[0062] S1. Under an inert atmosphere, mix the sulfide electrolyte precursor (prepared in Preparation Example 3), thiolated modified CNF (prepared in Preparation Example 1), and p-xylene in a mass ratio of 90:10:100. Then, place the mixture in a zirconia ball mill with 20 mm zirconia beads at a ball-to-material ratio of 16:1. Mix the mixture in a roller mill for 10 hours at 300 rpm to ensure uniformity.

[0063] S2. Place the mixed slurry in an inert atmosphere glove box and use a coating machine to evenly coat the slurry on a copper strip with a scraper. The copper strip is 10 μm, 8 cm wide, and 9 cm long. The scraper has a height of 240 μm, an angle of 90°, and a coating speed of 5 mm / s. The resulting composite solid electrolyte membrane has a thickness of 230 μm, a width of 6 cm, and a length of 8 cm.

[0064] S3. Dry the coated copper strip at 70° C. for 5 h in an inert atmosphere to form an electrolyte membrane on the copper strip.

[0065] S4. In an inert atmosphere, the electrolyte membrane is passed through a roller press at 120° C. and 20 MPa, and rolled repeatedly for 5 times to reduce its thickness to 200 μm to obtain a rolled product.

[0066] S5. Place the rolled product in a muffle furnace under an inert atmosphere and anneal at 200°C for 4 hours to obtain a composite solid electrolyte membrane. Cut out the electrolyte membrane with a length and width of 1 mm, assemble it on a sample stand, spray gold, and take scanning electron microscope photos (such as Figure 1 ).

[0067] It should be noted that, in this embodiment, the inert atmosphere is an argon environment with a water and oxygen content of ≤0.01 ppm.

[0068] Example 2

[0069] This embodiment provides a method for preparing a Li-PS composite sulfide solid electrolyte membrane modified by thiolation-modified CNF.

[0070] The preparation steps are basically the same as those in Example 1, except that:

[0071] In step S1, the thiolation-modified CNF is the thiolation-modified CNF prepared in Preparation Example 2.

[0072] Comparative Example 1

[0073] The difference between this comparative example and Example 1 is that no thiolation-modified CNF is added; the specific steps are as follows:

[0074] S1. Under an inert atmosphere, mix the sulfide electrolyte precursor and p-xylene at a mass ratio of 90:100. Then, place the mixture in a zirconia ball mill with 20 mm zirconia beads at a ball-to-material ratio of 16:1. Mix the mixture in a roller mill for 10 hours at 300 rpm to ensure uniformity.

[0075] The remaining steps are the same as in Example 1.

[0076] Comparative Example 2

[0077] The difference between this comparative example and Example 1 is:

[0078] In step S1, the thiolated modified CNF prepared in Preparation Example 1 was replaced with CNF (particle size: 40 nm).

[0079] Comparative Example 3

[0080] The difference between this comparative example and Example 1 is:

[0081] In step S1, the thiolation-modified CNF is the modified CNF prepared using mercaptopropyltrimethoxysilane in Comparative Preparation Example 1.

[0082] Comparative Example 4

[0083] The difference between this comparative example and Example 1 is:

[0084] In step S1, the thiolation-modified CNFs are the thiolation-modified carbon nanotubes prepared in Comparative Preparation Example 2.

[0085] Performance test case

[0086] 1. Battery assembly

[0087] Positive electrode sheet: The positive electrode material is NCM811, the positive electrode current collector is 10μm aluminum foil, and the binder is polyvinylidene fluoride. The mass ratio between the positive electrode active material (NCM811) and the binder (polyvinylidene fluoride PVDF) is 99:1. After mixing evenly, it is coated on the positive electrode current collector. The positive electrode material loading is 10 mg / cm 2 , the positive electrode is 8cm wide and 10cm long;

[0088] Negative electrode sheet: The negative electrode material is a lithium-indium alloy negative electrode (indium foil, thickness 200μm, lithium foil, thickness 50μm), the negative electrode sheet is 8cm wide and 10cm long, and is attached to the negative electrode collector, which is a 10μm copper foil;

[0089] Preparation of polymer electrolyte membrane: using the composite solid electrolyte membrane prepared in the above embodiments and comparative examples;

[0090] Battery assembly: In an inert atmosphere, the positive electrode, negative electrode and composite solid electrolyte membrane are stacked together in sequence, then vacuum-sealed to assemble into an all-solid-state soft-pack lithium battery.

[0091] It should be noted that the inert atmosphere of the assembly environment is an argon environment with a water and oxygen content of ≤0.01 ppm, and the test conditions are all in a constant temperature box at 25°C.

[0092] 2. Performance testing

[0093] The assembled batteries were subjected to cyclic discharge tests at 0.1C. The results of the first charge and discharge efficiency (first efficiency) and the capacity retention rate after 100 cycles are listed in Table 1. It can be seen that after adding thiolated modified CNF to the solid electrolyte membrane, the first efficiency of the battery is improved by about 16%, which means that the energy conversion efficiency of the battery during the first charge and discharge process is improved and the energy loss is reduced.

[0094] Capacity retention rate = 100th cycle discharge specific capacity / 1st cycle discharge specific capacity × 100%.

[0095] Table 1 Battery performance test table corresponding to each embodiment and comparative example

[0096]

[0097] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a composite sulfide solid electrolyte material, characterized in that: The steps include: S1. Mixing a sulfide electrolyte precursor, thiolated modified CNF, and a solvent in proportion and ball milling to obtain a mixed slurry; the mass ratio of the sulfide electrolyte precursor, thiolated modified CNF, and solvent is (50-95):(5-50):(100-200); S2, coating the mixed slurry on a substrate, and drying the coated substrate to remove the solvent; S3. Mechanically pressing the dried substrate under a protective atmosphere to densify the substrate; S4. heat-treating the mechanically pressed substrate under a protective atmosphere to obtain a composite sulfide solid electrolyte material; In step S1, the method for preparing thiolated modified CNF comprises the following steps: 1) High-pressure homogenization of nanocellulose CNF and 3-mercaptopropionic acid MPA at a molar ratio of 1:1-10; pressure 3-10 Bar, temperature 25-60°C, time 4-7 hours; 2) The material treated in step 1) is subjected to a heating treatment to obtain thiolated modified CNF; the heating temperature is 50-70° C. and the time is 5-20 h.

2. The preparation method according to claim 1, characterized in that In step S2, the substrate is a copper strip with a thickness of 10-20 μm, the coating process is carried out under an inert atmosphere, the drying temperature after coating is 70-80° C., and the drying time is 5-6 hours.

3. The preparation method according to claim 1, characterized in that In step S4, the heat treatment is performed under an inert atmosphere at a temperature of 120-300° C. for 1-5 hours.

4. The preparation method according to claim 1, characterized in that In step S3, the mechanical pressing is a roller pressing process, the roller pressing temperature is 100-200° C., and the pressure is 15-30 MPa.

5. The preparation method according to claim 1, characterized in that In step S1, the sulfide electrolyte precursor is a mixture of Li2S and P2S5 obtained by vibration ball milling, and the mass ratio of Li2S to P2S5 is 1:1.61~1.70; the vibration ball milling conditions are: vibration frequency of 1500~2000 rpm, ball-to-material ratio of 10-20:1, and ball milling time of 20-30h.

6. A composite sulfide solid electrolyte material prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the composite sulfide solid electrolyte material according to claim 6 in an all-solid-state soft-pack battery.

8. The use according to claim 7, characterized in that The all-solid-state soft-pack battery includes a positive electrode, a negative electrode, and an electrolyte membrane prepared from the composite sulfide solid electrolyte material, wherein the positive electrode material is NCM811, and the negative electrode is lithium metal or lithium-indium alloy.

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