A sulfide electrolyte film containing polyethylene wax and a preparation method thereof, and a full solid-state lithium ion battery

Abstract

This invention discloses a sulfide electrolyte membrane containing polyethylene wax, its preparation method, and an all-solid-state lithium-ion battery. The sulfide electrolyte membrane containing polyethylene wax comprises, by mass percentage: 94%–98.5% sulfide electrolyte, 1%–2% polyethylene wax, and 0.5%–5% binder. During the preparation of the sulfide electrolyte membrane, each component is mixed with a weakly polar solvent to prepare a slurry. After coating and forming a film, the weakly polar solvent is removed. The synergistic effect of the low molecular weight polyethylene wax and the weakly polar solvent significantly improves the film quality, greatly enhances the stability of the slurry, optimizes the performance of the electrolyte membrane, improves process economy, and broadens compatibility.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a sulfide electrolyte membrane containing polyethylene wax and its preparation method, and an all-solid-state lithium-ion battery. Background Technology

[0002] Solid-state lithium-ion batteries are considered one of the core development directions of next-generation energy storage technology due to their higher energy density, better safety, and longer cycle life. Sulfide electrolytes, as key materials for all-solid-state batteries, have advantages such as high ionic conductivity and excellent machinability. However, several technical challenges remain in thin-film preparation: First, after dispersing sulfide electrolyte powder into a slurry, uneven flowability and surface tension differences easily occur, leading to poor surface smoothness after film formation and defects such as pinholes, cracks, and edge shrinkage, affecting the interfacial contact stability of the battery. Second, controlling the viscosity of the slurry system is difficult. Low viscosity easily leads to component sedimentation and uneven coating thickness, while high viscosity causes bubbles to form during coating and reduces coating smoothness, ultimately affecting the mechanical properties and ion transport efficiency of the electrolyte membrane.

[0003] Existing technologies often improve electrolyte levels by adding traditional leveling agents (such as silicones and acrylates) or thickeners (such as cellulose derivatives and inorganic nanoparticles). However, these methods have significant limitations: silicone leveling agents have poor compatibility with sulfide electrolytes, which can easily lead to phase separation within the membrane and reduce the density of the electrolyte membrane; acrylate leveling agents have insufficient thermal stability and are prone to decomposition during high-temperature drying and solvent removal of the electrolyte membrane in battery manufacturing or during high-temperature cycling, affecting the long-term stability of the battery; inorganic nanoparticle thickeners can significantly increase the interfacial impedance of the electrolyte membrane and reduce ionic conductivity; and organic thickeners such as cellulose derivatives have the problems of strong hygroscopicity and poor dispersibility with sulfide systems.

[0004] Chinese patent application CN117525561A discloses a sulfide electrolyte slurry, a sulfide solid electrolyte, and their applications. It uses a combination of alkane and ether solvents as the solvent system. The alkane solvent can effectively swell the binder at room temperature, resulting in a clear and transparent electrolyte solution. The ether solvent has a higher polarity than the alkane solvent; the combination of the two improves the solvent polarity, allowing the solvent to effectively wet the sulfide electrolyte particles, thus better achieving the micronization / nanoization of the sulfide electrolyte during the dispersion process of the slurry.

[0005] Chinese patent application CN112635814A discloses an electrolyte membrane for a sulfide solid-state battery, its preparation method, and its uses. The electrolyte membrane comprises a base membrane, a nano-ceramic particle layer, and a sulfide electrolyte layer; wherein the pores of the base membrane contain electrolyte, the nano-ceramic particle layer is located on opposite sides of the surface of the base membrane, and the sulfide electrolyte layer is located on the surface of the nano-ceramic particle layer. Summary of the Invention

[0006] To address the aforementioned shortcomings in the prior art, this invention provides a sulfide electrolyte membrane containing polyethylene wax, its preparation method, and an all-solid-state lithium-ion battery.

[0007] The present invention first provides a sulfide electrolyte membrane containing polyethylene wax, wherein the components, by mass percentage, include: 94%~98.5% sulfide electrolyte, 1%~2% polyethylene wax, and 0.5%~5% binder; in the preparation process of the sulfide electrolyte membrane, each component is mixed with a weakly polar solvent to prepare a slurry, and after coating to form a film, the weakly polar solvent is removed.

[0008] Weakly polar solvents are those whose molecules contain a low content of polar groups, resulting in weak overall polarity. These solvents typically have small dipole moments and have minimal impact on the polarity of the solute during dissolution. Weakly polar solvents also have relatively low dielectric constants and are commonly used to dissolve nonpolar or weakly polar compounds. The weakly polar solvents used in this application are primarily cyclohexane, n-hexane, toluene, and xylene-based solvents, capable of dissolving or dispersing binders without chemically reacting with sulfide electrolyte materials.

[0009] Preferably, the sulfide electrolyte membrane containing polyethylene wax comprises, by mass percentage: 97%~98.5% sulfide electrolyte, 1%~2% polyethylene wax, and 0.5%~1% binder.

[0010] Preferably, the weakly polar solvent has a mass percentage content of 30% to 50% in the slurry.

[0011] Preferably, the weakly polar solvent is one or more of n-hexane, cyclohexane, and xylene.

[0012] More preferably, the weakly polar solvent is any combination of the following: A mixed solvent of cyclohexane and p-xylene in a volume ratio of 1 to 2:1 has both a high dissolution rate (reducing the dissolution time of polyethylene wax by 30% to 50%) and a low volatility rate, making it suitable for casting coating processes. A mixed solvent of n-hexane and cyclohexane in a volume ratio of 2 to 3:1 has a moderate evaporation rate, leaving no solvent residue in the coated film, making it suitable for blade coating processes. Pure p-xylene solvent has the highest solubility for polyethylene wax (solubility of 8g / 100ml at 25℃, meaning that up to 8g of polyethylene wax can be dissolved per 100ml of p-xylene solvent), making it suitable for the preparation of high-viscosity slurries.

[0013] Preferably, the sulfide electrolyte is Li7P3S in a glass-ceramic state. 11 And Li3PS4, tetragonal Li 10 GeP2S 12 and Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 and Li of the sulfide-germanium type 7-x PS 6-x Cl x and Li 6.6 Si 0.6 Sb 0.4 One or more of S5I, where x takes the value from 1 to 1.6.

[0014] Preferably, the particle size of the sulfide electrolyte is 0.7~10μm.

[0015] Preferably, the polyethylene wax has a molecular weight of 1000~8000 and a melting point of 80~120℃; more preferably, the polyethylene wax has a molecular weight of 3000 and a melting point of 100℃. Within this parameter range, the polyethylene wax dissolves faster in weakly polar solvents, and achieves an optimal balance between leveling properties, thickening effect, and compatibility with sulfide electrolytes.

[0016] Preferably, the binder is one or more of polyisobutylene (PIB), polybutadiene (CBR), hydrogenated styrene-butadiene block copolymer (SEBS), and hydrogenated styrene-isoprene block copolymer (SEPS). The binder is used to improve the dispersion stability and interparticle adhesion of the sulfide electrolyte powder in weakly polar solvents, prevent particle agglomeration in the slurry, and improve the strength of the dried sulfide electrolyte membrane.

[0017] This invention further provides a method for preparing the sulfide electrolyte membrane containing polyethylene wax, comprising the following steps: Step 1: Mix the polyethylene wax, binder, sulfide electrolyte, and weakly polar solvent to form a slurry; Step 2: Coat the slurry onto the substrate to form a film, and dry to remove the weakly polar solvent; Step 3: Roll pressing to obtain the sulfide electrolyte membrane containing polyethylene wax.

[0018] Preferably, in step 1, polyethylene wax is first added to the weakly polar solvent and heated and stirred until the polyethylene wax is completely dissolved to obtain a polyethylene wax-solvent solution. The weakly polar solvent lowers the dissolution temperature of the polyethylene wax, which can shorten the dissolution time until the polyethylene wax is completely dissolved to obtain a polyethylene wax-solvent solution. Then, a binder is added and dissolved, and stirred at 40°C for 1-6 hours to ensure that the binder is completely dissolved to form a homogeneous and transparent solution. Finally, a sulfide electrolyte is added, and the mixture is ball-milled to obtain the slurry. During ball milling, zirconia grinding beads are added, with a ball-to-material ratio of 4:1. Under inert gas (argon or nitrogen) protection, a planetary ball mill is used for 0.5 hours at a speed of 200-400 r / min to obtain a uniformly dispersed sulfide electrolyte slurry.

[0019] Preferably, the thickness of the slurry coated on the substrate in step 2 is 100~150μm. The slurry is coated onto the substrate (such as aluminum foil, ceramic sheet, polyimide PI or polyethylene terephthalate PET film) by means of scraping, casting or spraying.

[0020] The coated film was heated and dried at 40-80℃ on the bottom or in dry air for 10 minutes to remove the surface solvent. After the surface was dry, it was transferred to a vacuum oven and vacuum dried at 90℃ for 12 hours. It was further compacted and densified by roller pressing. The roller surface temperature was 40-60℃, the gap was adjusted and the roller pressure was 1-3MPa. After cooling, a dense and flat sulfide electrolyte membrane was obtained.

[0021] The present invention also provides an all-solid-state lithium-ion battery using the aforementioned sulfide electrolyte membrane containing polyethylene wax.

[0022] Low molecular weight polyethylene waxes typically have a molecular weight between 1,000 and 10,000 and are non-polar polymers, exhibiting good chemical and thermal stability. However, their low solubility in polar solvents can lead to uneven dispersion, affecting leveling and thickening effects. Weakly polar solvents such as n-hexane, cyclohexane, and toluene are better matched to the solubility parameters of low molecular weight polyethylene waxes, enabling rapid and complete dissolution. Furthermore, the weakly polar environment reduces the surface adsorption of sulfide electrolyte powders, further improving the dispersion stability of the slurry.

[0023] The core innovation of this invention lies in the synergistic effect of low molecular weight polyethylene wax and weakly polar solvent, the specific principle of which is as follows: 1. Improved solvent-wax compatibility: Solubility parameters of n-hexane, cyclohexane, and p-xylene (7.3~8.9 (cal / cm³)) 3 ) 1 / 2 ) and low molecular weight polyethylene wax (7.8~8.5 (cal / cm) 3 ) 1 / 2The high degree of matching allows polyethylene wax to dissolve quickly and completely at 40~60℃, avoiding coating defects caused by undissolved wax particles in traditional polar solvents; 2. Enhanced leveling effect: The weakly polar solvent has a low surface tension (20~30mN / m), which, in synergy with polyethylene wax, can further reduce the surface tension of the slurry, promote the rapid spreading of the slurry on the substrate, reduce edge shrinkage defects, and significantly improve the smoothness of the film layer; 3. Controllable thickening effect: In weakly polar solvents, polyethylene wax molecular chains extend more fully, forming a more stable network structure. The viscosity control accuracy of the slurry is improved to ±50mPa·s, avoiding uneven coating thickness caused by viscosity fluctuations in traditional solvents. 4. Optimized dispersion stability: The weakly polar environment reduces the surface adsorption of sulfide electrolyte powder (polar inorganic material), and with the help of a weakly polar binder, the slurry shows no significant sedimentation after standing for 10 hours (compared to only 2 hours in traditional polar solvent systems). 5. Reduced process energy consumption: The weakly polar solvents have lower boiling points (n-hexane 69℃, cyclohexane 81℃, xylene 137.6℃), which can reduce the drying temperature by 20~40℃ and shorten the drying time by 30%~50%, significantly reducing the energy consumption of the preparation.

[0024] Compared with the prior art, the present invention has the following beneficial effects: 1. Significantly improved film quality: The synergistic effect of low molecular weight polyethylene wax and weakly polar solvent reduces the surface roughness of the film to below 0.5μm, basically eliminating defects such as pinholes and edge shrinkage, and increasing the contact area between the electrolyte and the electrode interface. 2. Significantly improved slurry stability: The slurry showed no sedimentation after standing for 10 hours in a weakly polar system, and the viscosity fluctuation was less than 6%, meeting the requirements of large-scale continuous coating processes; 3. Electrolyte membrane performance optimization: The prepared electrolyte membrane has high density, and its room temperature ionic conductivity remains at 2.7 × 10⁻⁶. -3 ~2.9×10 -3 The S / cm ratio significantly improved the uniformity of the electrolyte membrane, with no foil leakage or localized unevenness observed. The bending strength of the electrolyte membrane was also enhanced (the minimum bending diameter can reach 10 mm).

[0025] 4. Improved process economy: The weakly polar solvent reduces the dissolution temperature by 20-30℃ and the drying time by 30%-50%, reducing the energy consumption per unit film layer preparation. Furthermore, the recyclability of the weakly polar solvent is estimated to be over 80%, further reducing costs. 5. Wider compatibility: Compatible with weakly polar systems and various sulfide electrolytes (Li3PS4, Li...). 10 GeP2S 12The electrode materials (sulfur cathode, silicon-based anode) have good compatibility and no interfacial side reactions occur, making them suitable for various all-solid-state lithium-ion battery systems. Attached Figure Description

[0026] Figure 1 The figures show the AC impedance test results of the sulfide electrolyte membranes prepared in Examples 1-3 and Comparative Examples 1-3.

[0027] Figure 2 For the membrane uniformity test results: The sulfide electrolyte membranes of Examples 1 and 2 showed a uniform effect under the projection of the auxiliary light source, while Comparative Examples 1 and 4 showed obvious tailing and unevenness. Detailed Implementation

[0028] Example 1 A sulfide electrolyte membrane containing low molecular weight polyethylene wax has the following composition by mass percentage: 98% Li6PS5Cl electrolyte powder, 1% low molecular weight polyethylene wax (molecular weight 3000, melting point 100℃), and 1% hydrogenated styrene-butadiene block copolymer (SEBS) (binder). The solvent used in the preparation process is a mixture of cyclohexane and p-xylene (volume ratio 1:1), and after preparation into a slurry, the solvent mass accounts for 44.4% of the total slurry mass.

[0029] Preparation method: (1) Add 0.5g of low molecular weight polyethylene wax to 40g of a mixed solvent of cyclohexane and p-xylene (volume ratio 1:1), stir at 50°C for 1h until completely dissolved to obtain polyethylene wax-mixed solvent.

[0030] (2) Add 0.5g of hydrogenated styrene-butadiene block copolymer SEBS to the polyethylene wax-mixed solvent, stir at 40°C for 4h, and the transparent adhesive can be obtained when the adhesive is completely dissolved.

[0031] (3) 49g of Li6PS5Cl powder was gradually added to the ball mill jar, along with the colloid obtained in the above steps. The mixture was ball milled for 0.5h under an inert gas atmosphere at a speed of 350r / min to obtain a sulfide electrolyte slurry.

[0032] (4) Lay a clean, flat, smooth aluminum foil on a coating machine with a heated plate. Use a micron-tunable film applicator to scrape and coat the sulfide electrolyte slurry onto the aluminum foil surface and then cast it onto the ceramic sheet. The coating gap of the film applicator is 100 μm.

[0033] (5) The sulfide electrolyte membrane was heated and dried at 50°C for 10 min on the bottom of a flat plate coating machine to remove the surface solvent. After the surface was dry, it was transferred to a vacuum oven and vacuum dried at 90°C for 12 h.

[0034] (6) The membrane is further compacted by roller pressing. The roller surface temperature is 40°C, the gap is adjusted and the roller pressure is 1MPa. After cooling, a dense and flat sulfide electrolyte membrane is obtained.

[0035] Example 2 A sulfide electrolyte membrane containing low molecular weight polyethylene wax has the following composition by mass percentage: 97% Li6PS5Cl electrolyte powder, 2% low molecular weight polyethylene wax (molecular weight 3000, melting point 100℃), and 1% hydrogenated styrene-butadiene block copolymer (SEBS). The solvent used in the preparation process is a mixture of cyclohexane and p-xylene (volume ratio 1:1), and after preparation into a slurry, the solvent mass accounts for 44.4% of the total slurry mass. The remaining preparation methods are the same as in Example 1.

[0036] Example 3 A sulfide electrolyte membrane containing low molecular weight polyethylene wax has the following composition by mass percentage: 97% Li6PS5Cl electrolyte powder, 2% low molecular weight polyethylene wax (molecular weight 3000, melting point 100℃), and 1% hydrogenated styrene-butadiene block copolymer (SEBS). The solvent used in the preparation process is a mixture of n-hexane and cyclohexane (volume ratio 2:1), and after preparation into a slurry, the solvent mass accounts for 44.4% of the total slurry mass. The remaining preparation methods are the same as in Example 1.

[0037] Example 4 A sulfide electrolyte membrane containing low molecular weight polyethylene wax has the following composition by mass percentage: 97% Li6PS5Cl electrolyte powder, 2% low molecular weight polyethylene wax (molecular weight 3000, melting point 100℃), and 1% hydrogenated styrene-butadiene block copolymer (SEBS). The solvent used in the preparation process is pure p-xylene, and after preparation into a slurry, the solvent mass accounts for 44.4% of the total slurry mass. The remaining preparation methods are the same as in Example 1.

[0038] Example 5 A sulfide electrolyte membrane containing low molecular weight polyethylene wax has the following composition by mass percentage: 97% Li3PS4 electrolyte powder (electrolyte replaced with 2%), 2% low molecular weight polyethylene wax (molecular weight 3000, melting point 100℃), and 1% hydrogenated styrene-butadiene block copolymer (SEBS). The solvent used in the preparation process is a mixture of cyclohexane and p-xylene (volume ratio 1:1), and after preparation into a slurry, the solvent mass accounts for 44.4% of the total slurry mass. The remaining preparation methods are the same as in Example 1.

[0039] Example 6 A sulfide electrolyte membrane containing low molecular weight polyethylene wax has the following composition by mass percentage: 97% Li6PS5Cl electrolyte powder, 2% low molecular weight polyethylene wax (molecular weight 1000, melting point 80℃), and 1% hydrogenated styrene-butadiene block copolymer (SEBS). The solvent used in the preparation process is a mixture of cyclohexane and p-xylene (volume ratio 1:1), and after preparation into a slurry, the solvent mass accounts for 44.4% of the total slurry mass. The remaining preparation methods are the same as in Example 1.

[0040] Example 7 A sulfide electrolyte membrane containing low molecular weight polyethylene wax has the following composition by mass percentage: 97% Li6PS5Cl electrolyte powder, 2% low molecular weight polyethylene wax (molecular weight 8000, melting point 120℃), and 1% hydrogenated styrene-butadiene block copolymer (SEBS). The solvent used in the preparation process is a mixture of cyclohexane and p-xylene (volume ratio 1:1), and after preparation into a slurry, the solvent mass accounts for 44.4% of the total slurry mass. The remaining preparation methods are the same as in Example 1.

[0041] Example 8 A sulfide electrolyte membrane containing low molecular weight polyethylene wax has the following composition by mass percentage: 97% Li6PS5Cl electrolyte powder, 2% low molecular weight polyethylene wax (molecular weight 3000, melting point 100℃), and 1% hydrogenated styrene-butadiene block copolymer (SEBS). The solvent used in the preparation process is a mixture of cyclohexane and p-xylene (volume ratio 1:1). To reduce the solvent content, the solvent mass after preparation as a slurry is 30% of the total slurry mass. The remaining preparation methods are the same as in Example 1.

[0042] Example 9 A sulfide electrolyte membrane containing low molecular weight polyethylene wax has the following composition by mass percentage: 97% Li6PS5Cl electrolyte powder, 2% low molecular weight polyethylene wax (molecular weight 3000, melting point 100℃), and 1% hydrogenated styrene-butadiene block copolymer (SEBS). The solvent used in the preparation process is a mixture of cyclohexane and p-xylene (volume ratio 1:1) to increase the solvent content. After preparation into a slurry, the solvent mass accounts for 50% of the total slurry mass. The remaining preparation methods are the same as in Example 1.

[0043] Example 10 A sulfide electrolyte membrane containing low molecular weight polyethylene wax has the following composition by mass percentage: 97% Li6PS5Cl electrolyte powder, 2% low molecular weight polyethylene wax (molecular weight 3000, melting point 100℃), and 1% hydrogenated styrene-butadiene block copolymer (SEBS). The solvent used in the preparation process is a mixture of cyclohexane and p-xylene (volume ratio 2:1), and after preparation into a slurry, the solvent mass accounts for 44.4% of the total slurry mass. The remaining preparation methods are the same as in Example 1.

[0044] Example 11 A sulfide electrolyte membrane containing low molecular weight polyethylene wax has the following composition by mass percentage: 97% Li6PS5Cl electrolyte powder, 2% low molecular weight polyethylene wax (molecular weight 3000, melting point 100℃), and 1% hydrogenated styrene-butadiene block copolymer (SEBS). The solvent used in the preparation process is a mixture of n-hexane and cyclohexane (volume ratio 3:1), and after preparation into a slurry, the solvent mass accounts for 44.4% of the total slurry mass. The remaining preparation methods are the same as in Example 1.

[0045] Example 12 A sulfide electrolyte membrane containing low molecular weight polyethylene wax has the following composition by mass percentage: 98.5% Li6PS5Cl electrolyte powder, 1% low molecular weight polyethylene wax (molecular weight 3000, melting point 100℃), and 0.5% hydrogenated styrene-butadiene block copolymer (SEBS) (binder). The solvent used in the preparation process is a mixture of cyclohexane and p-xylene (volume ratio 1:1), and after preparation into a slurry, the solvent mass accounts for 44.4% of the total slurry mass. The remaining preparation methods are the same as in Example 1.

[0046] Example 13 A sulfide electrolyte membrane containing low molecular weight polyethylene wax has the following composition by mass percentage: 94% Li6PS5Cl electrolyte powder, 1% low molecular weight polyethylene wax (molecular weight 3000, melting point 100℃), and 5% hydrogenated styrene-butadiene block copolymer (SEBS) (binder). The solvent used in the preparation process is a mixture of cyclohexane and p-xylene (volume ratio 1:1), and after preparation into a slurry, the solvent mass accounts for 44.4% of the total slurry mass. The remaining preparation methods are the same as in Example 1.

[0047] Comparative Example 1 A sulfide electrolyte membrane without low molecular weight polyethylene wax has the following composition by mass percentage: 99% Li6PS5Cl electrolyte powder and 1% hydrogenated styrene-butadiene block copolymer (SEBS). The solvent used in the preparation process is pure p-xylene, and after preparation into a slurry, the solvent mass accounts for 44.4% of the total slurry mass. The remaining preparation methods are the same as in Example 1.

[0048] Comparative Example 2 A sulfide electrolyte membrane prepared by a dry binder has the following composition by mass percentage: 99% Li6PS5Cl electrolyte powder and 1% polytetrafluoroethylene (PTFE) powder. The electrolyte powder and the dry binder are thoroughly mixed by a high-pressure mixer, and the mixture is extruded and kneaded to form a block material. The material is then rolled and thinned in a roller press to obtain a sulfide electrolyte membrane with a thickness of about 100 μm.

[0049] Comparative Example 3 A sulfide electrolyte membrane containing silane coupling agent-modified ethyl cellulose has the following composition by mass percentage: 97% Li6PS5Cl electrolyte powder, 2% silane coupling agent-modified ethyl cellulose (model: Plus550, brand: Ashland, viscosity: 700~1000 mPa·s), and 1% hydrogenated styrene-butadiene block copolymer (SEBS). The solvent used in the preparation process is a mixture of cyclohexane and p-xylene (volume ratio 1:1), and after preparation into a slurry, the solvent mass accounts for 44.4% of the total slurry mass. The remaining preparation methods are the same as in Example 1.

[0050] Comparative Example 4 A sulfide electrolyte membrane without low molecular weight polyethylene wax has the following composition by mass percentage: 99% Li3PS4 electrolyte powder and 1% hydrogenated styrene-butadiene block copolymer (SEBS). The solvent used in the preparation process is pure p-xylene, and after preparation into a slurry, the solvent mass accounts for 44.4% of the total slurry mass. The remaining preparation methods are the same as in Example 1.

[0051] Detection Example 1 (1) Method for testing slurry viscosity: In an inert gas protected environment, the sulfide electrolyte slurry after ball milling for 0.5 hours was taken, and its viscosity was measured using a rotational viscometer. The viscosity was recorded as V after the value stabilized. 0h The slurry was sealed and allowed to stand for 10 hours. The viscosity of the slurry was measured again and recorded as V. 10h Calculate viscosity fluctuations: Viscosity fluctuation = (V 0h -V 10h ) / V 0h ×100%.

[0052] (2) Ionic conductivity testing method: Test temperature 25±1℃.

[0053] 1) Use a sampler to take electrolyte membrane discs.

[0054] 2) Place the electrolyte membrane disc into the tableting mold; press the tableting mold containing the sample disc using a hydraulic press according to the design pressure.

[0055] 3) Load the sample disc into the test mold and pressurize the test mold according to the designed test pressure.

[0056] 4) Connect the test mold to the electrochemical workstation; select the EIS test program, input the set potential of 0.01V, set the test frequency of 10MHz-0.1Hz, and start the test program; the formula for calculating ionic conductivity is: σ=L / (R×S), with the unit being S / cm.

[0057] (3) Membrane uniformity test method: The sulfide electrolyte slurry was coated onto the surface of a transparent PET film using the same method. After drying, a sample was placed above a light source, and the uniformity of the film surface was observed under the projection of an auxiliary parallel light source.

[0058] (4) Electrolyte membrane flexural strength test method: The sample size is 100mm×10mm. The sulfide electrolyte membrane is wound sequentially around the surface of cylinders with diameters of 50mm, 30mm and 10mm respectively. The electrolyte membrane is observed with a magnifying glass to see if it bends, breaks or falls off. When a break occurs at a certain diameter, the diameter of the cylinder at that time is recorded.

[0059] The above embodiments and comparative examples are shown in Table 1. The "film uniformity" is measured by its performance under the projection of an auxiliary parallel light source. Good uniformity is characterized by the absence of particles and light leakage, while "poor" uniformity is characterized by obvious tailing or unevenness, and "average" is characterized by a balance between the two. In the film bending strength section, "yes" indicates no damage or material loss, while "no" indicates damage or material loss.

[0060] Table 1 Ion conductivity was measured. Figure 1 The AC impedance test results are shown for the sulfide electrolyte membranes prepared in Examples 1 to 3 and Comparative Examples 1 to 3.

[0061] like Figure 2 As shown, the sulfide electrolyte membranes of Examples 1 and 2 exhibited a uniform effect under the projection of an auxiliary light source, and the membrane uniformity was rated as "good"; while Comparative Examples 1 and 4 showed obvious tailing and non-uniformity, and the membrane uniformity was rated as "poor".

[0062] As shown in Table 1, compared with Comparative Example 1, the sulfide electrolyte membrane containing low molecular weight polyethylene wax in Example 2 exhibits significantly improved slurry stability. The membrane also demonstrates excellent uniformity when coated on a PET surface. Furthermore, the ionic conductivity reflects the significant improvement in electrolyte slurry dispersion and uniformity achieved by the polyethylene wax, reaching 2.9 × 10⁻⁶. -3The S / cm also improves the bending strength of the electrolyte membrane, allowing it to bend on the surface of a 10mm diameter cylinder without material loss. Although Comparative Example 2 also has relatively excellent ionic conductivity and bending strength, the dry electrolyte membrane cannot be thinned to below 100μm, and is prone to large-area cracking during rolling. The process of dry electrolyte membrane is also more complex. In Example 5 and Comparative Example 4, changing the type of sulfide electrolyte did not result in significant differences in ionic conductivity, indicating that polyethylene wax has a wider range of applications in sulfide electrolyte membranes.

Claims

1. A sulfide electrolyte membrane containing polyethylene wax, characterized in that, The components, by mass percentage, include: 94%~98.5% sulfide electrolyte, 1%~2% polyethylene wax, and 0.5%~5% binder. In the preparation of the sulfide electrolyte membrane, each component is mixed with a weakly polar solvent to prepare a slurry, which is then coated into a film and the weakly polar solvent is removed.

2. The sulfide electrolyte membrane containing polyethylene wax according to claim 1, characterized in that, The weakly polar solvent has a mass percentage content of 30% to 50% in the slurry.

3. The sulfide electrolyte membrane containing polyethylene wax according to claim 1, characterized in that, The weakly polar solvent is one or more of n-hexane, cyclohexane, and xylene.

4. The sulfide electrolyte membrane containing polyethylene wax according to claim 3, characterized in that, The weakly polar solvent is any combination of the following: A mixed solvent of cyclohexane and p-xylene, with a volume ratio of 1~2:1; A mixed solvent of n-hexane and cyclohexane, with a volume ratio of 2~3:1; Pure p-xylene solvent.

5. The sulfide electrolyte membrane containing polyethylene wax according to claim 1, characterized in that, The sulfide electrolyte is Li7P3S in a glass-ceramic state. 11 And Li3PS4, tetragonal Li 10 GeP2S 12 and Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 and Li of the sulfide-germanium type 7-x PS 6-x Cl x and Li 6.6 Si 0.6 Sb 0.4 One or more of S5I, where x takes the value from 1 to 1.

6.

6. The sulfide electrolyte membrane containing polyethylene wax according to claim 1, characterized in that, The polyethylene wax has a molecular weight of 1000~8000 and a melting point of 80~120℃.

7. The sulfide electrolyte membrane containing polyethylene wax according to claim 1, characterized in that, The adhesive is one or more of polyisobutylene, polybutadiene, hydrogenated styrene-butadiene block copolymer, and hydrogenated styrene-isoprene block copolymer.

8. The method for preparing the sulfide electrolyte membrane containing polyethylene wax according to any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: Mix the polyethylene wax, binder, sulfide electrolyte, and weakly polar solvent to form a slurry; Step 2: Coat the slurry onto the substrate to form a film, and dry to remove the weakly polar solvent; Step 3: Roll pressing to obtain the sulfide electrolyte membrane containing polyethylene wax.

9. The method for preparing the sulfide electrolyte membrane containing polyethylene wax according to claim 8, characterized in that, In step 1, polyethylene wax is first added to the weakly polar solvent and heated and stirred until the polyethylene wax is completely dissolved to obtain a polyethylene wax-solvent solution; then the binder is added and dissolved; finally, a sulfide electrolyte is added and ball-milled to obtain the slurry.

10. A fully solid-state lithium-ion battery, characterized in that, Use the sulfide electrolyte membrane containing polyethylene wax as described in any one of claims 1 to 7.

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