Composite sulfide solid electrolyte material and preparation method and application thereof

Abstract

The invention belongs to the technical field of new energy materials, and particularly discloses a composite sulfide solid electrolyte material and a preparation method and application thereof. The preparation method of the composite sulfide solid electrolyte material comprises the following steps: S1, mixing a sulfide electrolyte precursor, thiolated modified CNF and a solvent in proportion, and carrying out ball milling; obtaining mixed slurry; the mass ratio of the sulfide electrolyte precursor to the thiolated modified CNF to the solvent (p-xylene) is (50-95): (5-50): (100-200); s2, coating a substrate with the mixed slurry, and drying the coated substrate to remove the solvent; s3, carrying out heat treatment on the dried matrix in a protective atmosphere; and S4, performing densification processing on the matrix subjected to heat treatment through mechanical pressing to obtain the composite sulfide solid electrolyte material. According to the method, the thiolated modified CNF is used as a modifier, so that the performance of the solid electrolyte material is improved.

Description

Technical Field

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

[0002] With the continuous growth of energy demand and the 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 to replace traditional liquid electrolytes, have advantages such as higher safety, wider electrochemical windows, and higher energy density, and are considered the development direction of the next generation of energy storage devices. However, current solid electrolyte materials still face some challenges.

[0003] The solid electrolyte system mainly includes three types of materials: sulfides, oxides, and polymers. Among them, sulfide electrolytes have become a research hotspot due to their ultra-high ionic conductivity (10 -3 ~10 -2 S / cm). However, their intrinsic mechanical strength deficiency leads to two core problems: First, lithium dendrites are prone to penetrate the electrolyte layer and cause short circuits; second, microcracks are generated at the electrode / electrolyte interface due to volume changes during cycling. Existing strengthening strategies all have significant defects - although oxide composites can increase the strength to 1.2 GPa, the heterogeneous interface causes a 60% attenuation of ionic conductivity; although the polymer composite system has good ductility, it is limited by a room temperature ionic conductivity < 10 -4 S / cm. Therefore, the most promising electrolyte system at present is the sulfide solid electrolyte.

[0004] Due to its nano-scale size effect, nanocellulose exhibits excellent properties in multiple fields, such as having broad application prospects in material reinforcement, biomedicine, energy storage, etc. Its unique structural and performance characteristics make it one of the research hotspots in the current field of materials science. Based on the high specific modulus and high strength of nanocellulose, a three-dimensional reinforced composite solid electrolyte network can be constructed. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a composite sulfide solid electrolyte material, a preparation method thereof, and an 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 the second stage of ball milling. By using the buffering effect of the liquid phase medium, the aspect ratio and dispersion uniformity of CNF are regulated, realizing the efficient dispersion and cross-scale structure regulation of the nano-reinforcing phase; constructing a three-dimensional interpenetrating network framework.

[0007] The purpose of the present invention is achieved through the following technical solutions: <The first aspect> The present invention provides a preparation method of a composite sulfide solid electrolyte material, comprising the following steps: S1. Mix a sulfide electrolyte precursor, thiolated modified CNF, and a solvent (such as p-xylene) in a proportion and perform ball milling to obtain a mixed slurry; the mass ratio of the sulfide electrolyte precursor, thiolated modified CNF, and the solvent is (50-95):(5-50):(100-200); S2. Coat the mixed slurry on a substrate, and dry the coated substrate to remove the solvent; S3. Mechanically press the dried substrate under a protective atmosphere to densify the substrate; S4. Perform heat treatment on the mechanically pressed substrate under a protective atmosphere to obtain a composite sulfide solid electrolyte material; In step S1, the preparation method of the thiolated modified CNF comprises the following steps: 1). Perform high-pressure homogenization treatment on nanocellulose (CNF) and 3-mercaptopropionic acid (MPA) at a molar ratio of 1:1-10; the pressure is 3-10 Bar, the temperature is 25-60 °C, and the time is 4-7 h; 2). Heat-treat the material processed in step 1) to obtain thiolated modified CNF, the temperature is 50-70 °C, and the time is 5-20 h.

[0008] In step S1, the parameters of the ball milling treatment are: the ball-to-material ratio is 15-20:1, the rotation speed is 300-500 revolutions per hour, and the ball milling time is 15-20 h.

[0009] The average diameter of the thiolated modified CNF is 70-120 nm, and a three-dimensional interpenetrating network structure is formed with the sulfide electrolyte precursor through ball milling (wet ball milling).

[0010] Here, wet ball milling refers to a mechanical processing process in which solid materials are crushed, mixed, and dispersed by the impact, friction, and shear effects of grinding balls (such as ceramic balls, metal balls, etc.) in the presence of a liquid medium (solvent).

[0011] 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 h.

[0012] In step S4, the heat treatment is carried out under an inert atmosphere, the temperature is 120-300 °C, and the time is 1-5 h.

[0013] In step S3, the mechanical pressing is roll pressing treatment, the roll pressing temperature is 100-200 °C, and the pressure is 15-30 MPa.

[0014] In step S1, the sulfide electrolyte precursor is a mixture obtained by vibration ball milling of Li2S and P2S5, and the mass ratio of Li2S to P2S5 is 1:1.61 - 1.70; the vibration ball milling conditions are: the vibration frequency is 1500 - 2000 revolutions per minute, the ball-to-material ratio is 20:1, and the ball milling time is 20 - 30 h.

[0015] The particle size of the sulfide electrolyte precursor powder is in the micron range; the particle size is 100 - 500 μm.

[0016] Both the ball milling tank and the grinding balls are made of zirconia.

[0017] <Second aspect> The present invention also provides a composite sulfide solid electrolyte material obtained by the preparation method as described above.

[0018] In the present invention, nanocellulose (CNF) is pretreated to obtain thiolated modified CNF: ;(1000 ≤ n ≤ 10000).

[0019] The high-pressure homogenizer used is a high-pressure homogenizer with the brand of Holder and the model of HD-HP10.

[0020] As an embodiment, the slurry is mixed for 10 - 15 h using a rolling mill (Miqi horizontal DMS-4) or a shearer.

[0021] <Third aspect> The application of the composite sulfide solid electrolyte material in an all-solid-state soft-pack battery also falls within the protection scope of the present invention.

[0022] For the all-solid-state soft-pack battery, the 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 a lithium-indium alloy.

[0023] As an embodiment, the negative electrode includes lithium metal or a metal lithium composite.

[0024] As an embodiment, the positive electrode includes NCM811.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) Better interfacial compatibility: By introducing modified CNF into the sulfide solid electrolyte, a stable chemical bonding interface is constructed through a unique surface modification technology, significantly reducing the electrode / electrolyte contact impedance. Through molecular-level structure regulation, interfacial side reactions and structural degradation during cycling are effectively inhibited.

[0026] (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 the volume changes during charge and discharge of solid-state batteries.

[0027] (3) Higher electrochemical stability: Modified CNF can act as a stabilizer to improve the electrochemical stability of solid electrolytes and extend the lifespan of solid-state batteries.

[0028] (4) Lower cost and resource sustainability: Using renewable biomass-based nanomaterials as key components can significantly reduce raw material costs while enhancing performance. Their natural degradability also reduces the environmental load throughout the life cycle, meeting the requirements of the low-carbon economic transformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Other features, objectives, and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings: Figure 1 SEM photograph of the Li-P-S composite sulfide solid electrolyte membrane modified with thiolated CNF prepared for Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention will be described in detail below with reference to embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several adjustments and improvements can be made. These all fall within the protection scope of the present invention.

[0031] Preparation Example 1 Preparation of Thiolated Modified CNF 1. Mix CNF and 3-mercaptopropionic acid (MPA) in a molar ratio of 1:5 in an air environment, and use a high-pressure homogenizer to homogenize for 5 h at 60 °C, 10 Bar, and 120 L / h to obtain a colloidal solution.

[0032] 2. React the colloidal solution at 60 °C for 10 h in an air environment to obtain thiolated modified CNF with an average diameter of 70 nm.

[0033] Preparation Example 2 Preparation of Thiolated Modified CNF 1. Mix CNF and 3-mercaptopropionic acid (MPA) in a molar ratio of 1:8 in an air environment, and use a high-pressure homogenizer to homogenize for 5 h at 60 °C, 10 Bar, and 120 L / h to obtain a colloidal solution.

[0034] 2. React the colloidal solution at 60 °C for 10 h in an air environment to obtain thiolated modified CNF with an average diameter of 120 nm.

[0035] Preparation Example 3: Preparation of Sulfide Electrolyte Precursor Under an inert atmosphere, Li2S and P2S5 with a mass ratio of 1:1.65 and 10 mm zirconia grinding balls were jointly loaded into a zirconia ball mill jar and subjected to high-energy mechanical grinding in a vibratory ball mill for 20 h. Among them, the ball-to-material ratio was 20:1, the amplitude was 5 mm, and the vibration frequency was 1800 revolutions per minute to obtain the sulfide electrolyte precursor.

[0036] Comparative Preparation Example 1 The difference between this comparative preparation example and Preparation Example 1 is as follows: In Step 1, 3-mercaptopropionic acid (MPA) was replaced with mercaptopropyltrimethoxysilane (MPTMS).

[0037] Step 2 was the same as Preparation Example 1 to obtain CNF modified with mercaptopropyltrimethoxysilane with an average diameter of 70 nm.

[0038] Comparative Preparation Example 2 The difference between this comparative preparation example and Preparation Example 1 is as follows: In Step 1, CNF was replaced with carbon nanotubes.

[0039] Step 2 was the same as Preparation Example 1 to obtain thiolated modified carbon nanotubes with an average diameter of.

[0040] Example 1 This example provides a method for preparing a Li-P-S composite sulfide solid electrolyte membrane modified with thiolated CNF.

[0041] S1. Under an inert atmosphere, the sulfide electrolyte precursor (prepared in Preparation Example 3), thiolated CNF (prepared in Preparation Example 1), and p-xylene were mixed according to a mass ratio of 90:10:100. Then, they were jointly loaded into a zirconia ball mill jar with 20 mm zirconia ball mill beads. The ball-to-material ratio was 16:1, and a rolling mill was used to mix for 10 h at a rotation speed of 300 revolutions per hour to ensure the uniformity of the mixed slurry; S2. The mixed slurry was placed in an inert atmosphere glove box, and a coater was used to uniformly coat the slurry on a copper strip with a doctor blade. Among them, the copper strip was 10 μm thick, 8 cm wide, and 9 cm long. The height of the doctor blade was 240 μm, the angle was 90°, and the coating speed was 5 mm / s to form a composite solid electrolyte membrane with a thickness of 230 μm, a width of 6 cm, and a length of 8 cm; S3. The coated copper strip was dried at 70 °C for 5 h under an inert atmosphere environment to form an electrolyte membrane on the copper strip.

[0042] S4. The electrolyte membrane was repeatedly rolled 5 times at 120 °C and 20 MPa by a rolling press under an inert atmosphere environment to reduce its thickness to 200 μm to obtain a rolled product.

[0043] S5. Place the roll-pressed product in a muffle furnace under an inert atmosphere and anneal it at 200 °C for 4 h to obtain a composite solid electrolyte membrane. Cut out an electrolyte membrane with a length and width of 1 mm each, assemble it on a sample stage for gold spraying, and take a scanning electron microscope photo (as Figure 1 ).

[0044] It should be noted that in this embodiment, the inert atmosphere is an argon environment with a water and oxygen content ≤ 0.01 ppm.

[0045] Example 2 This embodiment provides a preparation method of a Li-P-S composite sulfide solid electrolyte membrane modified with thiolated CNF.

[0046] The preparation steps are basically the same as those in Example 1, and the difference is that: In step S1, the thiolated CNF used is the thiolated CNF prepared in Preparation Example 2.

[0047] Comparative Example 1 The difference between this comparative example and Example 1 is that no thiolated CNF is added; the specific steps are as follows: S1. Mix the sulfide electrolyte precursor and p-xylene in a mass ratio of 90:100 under an inert atmosphere. Then, load them together with 20 mm zirconia milling beads into a zirconia milling jar, with a ball-to-material ratio of 16:1, and use a rolling mill to mix for 10 h at a rotation speed of 300 revolutions per hour to ensure the uniformity of the mixed slurry.

[0048] The remaining steps are the same as those in Example 1.

[0049] Comparative Example 2 The difference between this comparative example and Example 1 is that: In step S1, the thiolated CNF prepared in Preparation Example 1 is replaced with CNF (particle size: 40 nm).

[0050] Comparative Example 3 The difference between this comparative example and Example 1 is that: In step S1, the thiolated CNF used is the modified CNF prepared with 3-mercaptopropyltrimethoxysilane in Comparative Preparation Example 1.

[0051] Comparative Example 4 The difference between this comparative example and Example 1 is that: In step S1, the thiolated CNF used is the thiolated carbon nanotubes prepared in Comparative Preparation Example 2.

[0052] Performance Test Example 1. Battery Assembly Positive electrode sheet: The positive electrode material is NCM811, the positive electrode current collector is 10-μm aluminum foil, 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 being mixed evenly, it is coated on the positive electrode current collector, and the loading of the positive electrode material is 10 mg / cm 2 , the width of the positive electrode sheet is 8 cm and the length is 10 cm; Negative electrode sheet: The negative electrode material is a lithium-indium alloy negative electrode (indium foil with a thickness of 200 μm, lithium foil with a thickness of 50 μm). The width of the negative electrode sheet is 8 cm and the length is 10 cm. It is attached to the negative electrode current collector, and the negative electrode current collector is 10-μm copper foil; Preparation of polymer electrolyte membrane: Use the composite solid electrolyte membranes prepared in the above-mentioned various examples and comparative examples; Battery assembly: In an inert atmosphere, stack the positive electrode, negative electrode and composite solid electrolyte membrane together in sequence, and then perform vacuum sealing to assemble an all-solid-state soft-pack lithium battery.

[0053] It should be noted that the inert atmosphere for the assembly environment is an argon environment with a water and oxygen content ≤ 0.01 ppm, and the test conditions are all in an incubator at 25 °C.

[0054] 2. Performance detection Perform cyclic charge and discharge tests on the assembled batteries at 0.1C. The results of the first charge-discharge efficiency (initial 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 initial efficiency of the battery is increased 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.

[0055] Capacity retention rate = discharge specific capacity in the 100th cycle / discharge specific capacity in the first cycle × 100%.

[0056] Table 1 Battery performance test table corresponding to each example and comparative example

[0057] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A preparation method of a composite sulfide solid electrolyte material, characterized in that, It includes the following steps: S1. Mix a sulfide electrolyte precursor, thiolated modified CNF, and a solvent in a certain proportion and perform ball milling to obtain a mixed slurry; the mass ratio of the sulfide electrolyte precursor, thiolated modified CNF, and the solvent is (50~95):(5~50):(100~200); S2. Coat the mixed slurry on a substrate, and dry the coated substrate to remove the solvent; S3. Mechanically press the dried substrate under a protective atmosphere to densify the substrate; S4. Heat-treat the mechanically pressed substrate under a protective atmosphere to obtain a composite sulfide solid electrolyte material; In step S1, the preparation method of the thiolated modified CNF includes the following steps: 1). Perform high-pressure homogenization treatment on nanocellulose CNF and 3-mercaptopropionic acid MPA at a molar ratio of 1:1~10; the pressure is 3~10 Bar, the temperature is 25~60 °C, and the time is 4~7 h; 2). Heat-treat the material obtained in step 1) 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 h.

3. The preparation method according to claim 1, characterized in that, In step S4, the heat treatment is carried out under an inert atmosphere, the temperature is 120~300 °C, and the time is 1~5 h.

4. The preparation method according to claim 1, wherein In step S3, the mechanical pressing is roll pressing treatment, the roll 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 obtained by vibration ball milling of Li2S and P2S5, and the mass ratio of Li2S and P2S5 is 1:1.61~1.70; the vibration ball milling conditions: the vibration frequency is 1500~2000 revolutions per minute, the ball-to-material ratio is 10-20:1, and the ball milling time is 20-30 h.

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

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

8. The application according to claim 7, wherein 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 a lithium-indium alloy.

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