Sulfide solid electrolyte membrane, method for manufacturing the same, and solid-state battery
By employing a composite support and a gradient-doped electrolyte layer in a sulfide solid electrolyte, the problems of brittleness, microcracks, and interfacial impedance in existing sulfide solid electrolytes are solved, resulting in an ultra-thin electrolyte membrane with high ionic conductivity and long-cycle stability, thus improving the overall performance of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XIAN THERMAL POWER RES INST CO LTD
- Filing Date
- 2026-06-08
- Publication Date
- 2026-07-10
AI Technical Summary
Existing sulfide solid electrolytes suffer from inherent brittleness, difficulty in fabricating ultrathin films, susceptibility to microcracks, high interfacial impedance, and poor chemical stability, which limit their application in the field of energy storage and frequency regulation.
The design employs a composite support and a gradient-doped electrolyte layer. The support is constructed using boron-doped cellulose nanosheets and boron nitride nanosheets, and a covalent network is formed through gradient doping and in-situ crosslinking to enhance mechanical strength and chemical stability, providing continuous ion transport channels.
A sulfide solid electrolyte membrane with ultrathin thickness, high ionic conductivity and excellent mechanical strength has been achieved, which reduces interfacial impedance, improves battery cycle life and rate response, and enhances battery safety and thermal management capabilities.
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Figure CN122370484A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of sulfide solid electrolytes, specifically to sulfide solid electrolyte membranes, their preparation methods, and solid-state batteries. Background Technology
[0002] Sulfide solid electrolytes are considered core materials for energy storage and frequency regulation solid batteries because their room temperature ionic conductivity is close to that of liquid electrolytes and their electrochemical window is wide.
[0003] However, existing sulfide solid electrolytes have the following three major technical bottlenecks: high intrinsic brittleness, making it difficult to prepare self-supporting films with a thickness of less than 30 μm, and prone to microcracks during cycling, leading to lithium dendrite penetration; high interfacial impedance, resulting in poor contact with the positive and negative electrode interfaces, severe polarization at high rates, and limiting the frequency modulation response speed; and poor chemical stability, making them prone to decomposition at high voltage and high current density, leading to rapid decay of cycle life.
[0004] Currently, most mainstream composite support solutions use inert polymer skeletons, which improve mechanical strength but significantly reduce overall ionic conductivity; while single doping modification is difficult to simultaneously achieve ionic conductivity and chemical stability.
[0005] Therefore, there is an urgent need to develop a sulfide solid electrolyte membrane that simultaneously possesses ultra-thin thickness, high ionic conductivity, excellent mechanical strength, and interfacial stability to meet the special requirements of the energy storage and frequency regulation field. Summary of the Invention
[0006] This application proposes a sulfide solid electrolyte membrane, a method for preparing the same, and a solid-state battery to address the deficiencies of the prior art.
[0007] According to a first aspect of the embodiments of this application, a sulfide solid electrolyte membrane is provided, comprising a composite support and a gradient-doped electrolyte layer for forming at least one surface of the composite support; The composite support comprises boron-doped nanocellulose and boron nitride nanosheets dispersed in the boron-doped nanocellulose; The gradient-doped electrolyte layer is a sulfide solid electrolyte layer, and the gradient-doped electrolyte layer has a doping concentration that varies along the direction away from the composite support.
[0008] In some embodiments, the gradient-doped electrolyte layer includes a low-doped layer and a high-doped layer; the low-doped layer is located further away from the composite support than the high-doped layer.
[0009] In some embodiments, the gradient-doped electrolyte layer comprises a sulfide solid electrolyte, a halide dopant, and a polyetheramine, wherein the polyetheramine and the sulfide solid electrolyte are cross-linked to form a covalent network.
[0010] In some embodiments, the sulfide solid electrolyte is Li7P3S. 11 .
[0011] In some embodiments, the halide dopant in the low-doped layer accounts for 0.5% to 2% of the total mass of the sulfide solid electrolyte, the halide dopant, and the polyetheramine; The mass of the halide dopant in the highly doped layer accounts for 2% to 5% of the total mass of the sulfide solid electrolyte, the halide dopant, and the polyetheramine.
[0012] In some embodiments, the halide dopant is lithium bromide and / or lithium iodide.
[0013] In some embodiments, the boron doping content in the boron-doped nanocellulose is 0.5 wt% to 2.0 wt%, the diameter of the boron in the boron-doped nanocellulose is 20 nm to 50 nm, and the length of the boron in the boron-doped nanocellulose is 1 μm to 5 μm; the thickness of the boron nitride nanosheet is 1 nm to 5 nm, and the lateral dimension of the boron nitride nanosheet is 0.5 μm to 2 μm.
[0014] In some embodiments, the composite support has a thickness of 2 μm to 6 μm and a porosity of 40%-60%. The thickness of the low-doped layer is 5 μm to 12 μm, and the thickness of the high-doped layer is 3 μm to 8 μm; The thickness of the sulfide solid electrolyte membrane is 15 μm to 30 μm.
[0015] According to a second aspect of this application, a preparation method is provided for preparing a sulfide solid electrolyte membrane as described above, comprising: Boron-doped cellulose nanofibers were dispersed in water, and boron nitride nanosheets and a crosslinking agent were added to react, followed by film formation and drying to obtain a boron-doped cellulose nanofibers-boron nitride nanosheet composite support. High-doped sulfide electrolyte slurries and low-doped sulfide electrolyte slurries with different halide dopant contents were prepared respectively. The low-doped sulfide electrolyte slurry and the high-doped sulfide electrolyte slurry are sequentially coated on the substrate to form an electrolyte membrane precursor with a gradient structure. The precursor is then heat-treated to allow the polyetheramine in the low-doped sulfide electrolyte slurry and the high-doped sulfide electrolyte slurry to undergo an in-situ crosslinking reaction with the sulfide solid electrolyte. The highly doped sides of the two heat-treated electrolyte membrane precursors are respectively attached to both sides of the composite support, and then subjected to cold pressing and substrate peeling to obtain the sulfide solid electrolyte membrane.
[0016] According to a third aspect of this application, a solid-state battery is provided, including a positive electrode, a negative electrode, and a sulfide solid electrolyte membrane as described above disposed between the positive electrode and the negative electrode.
[0017] The beneficial effects of the sulfide solid electrolyte membrane and its preparation method, as well as the solid-state battery, according to the embodiments of this application, include at least the following: This application embodiment achieves high ionic conductivity on the support side and maintains good chemical stability on the contact electrode side by designing a concentration gradient structure from the highly doped support side to the low-doped electrode side, thus resolving the contradiction between high ionic conductivity and interfacial chemical stability that is difficult to achieve with single uniform doping. This application embodiment also uses heat treatment to induce in-situ crosslinking between the polyetheramine binder and the sulfide electrolyte, forming a covalent network. This not only enhances the mechanical strength of the electrolyte membrane and suppresses microcrack formation but also significantly improves the interfacial bonding within the electrolyte layer and between layers, providing continuous ion transport channels and reducing interfacial impedance. This application embodiment uses boron-doped nanocellulose and boron nitride nanosheets to construct a composite support. The mechanical strength of the nanocellulose forms the support framework, while the boron nitride nanosheets improve thermal conductivity and flame retardancy. Both components have a certain lithium-ion conductivity, avoiding the ionic insulation problem caused by using a completely inert support. This achieves ultrathinness and enhances mechanical and thermal properties while minimizing the negative impact on overall ionic conductivity. Attached Figure Description
[0018] Figure 1 This is a low-magnification SEM image of a sulfur-containing polymer electrolyte membrane according to an embodiment of this application; Figure 2 This is a high-magnification SEM image of a sulfur-containing polymer electrolyte membrane according to an embodiment of this application; Figure 3 The diagram shows a comparison of the ionic conductivity results of Examples 1 to 10 and Comparative Examples 1 to 3 of this application. Figure 4 This is a diagram showing a comparison of impedance results between Example 1 and Comparative Example 1 of this application. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the sulfide solid electrolyte membrane and its preparation method, as well as the solid-state battery, will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of this application. Obviously, the described embodiments are only some embodiments of the embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0020] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed embodiments of the present application, but merely to illustrate selected embodiments of the present application. Other embodiments obtained by those skilled in the art based on the embodiments of the present application without inventive effort are all within the scope of protection of the embodiments of the present application.
[0021] It can be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it will not be further defined and explained in subsequent figures according to the embodiments of this application.
[0022] This application discloses a sulfide solid electrolyte membrane, its preparation method, and a solid-state battery. The sulfur-containing polymer electrolyte membrane is prepared based on the preparation method described above. The solid-state battery is equipped with the sulfur-containing polymer electrolyte membrane and is particularly suitable for power system energy storage and frequency regulation scenarios. It is preferably applied to gradient doped interfacial crosslinked ultrathin sulfide solid electrolyte membrane, its preparation method, and energy storage solid-state battery in the field of energy storage and frequency regulation. The purpose is to solve the problem that sulfide electrolytes in the prior art are difficult to achieve ultrathinness, high ionic conductivity, and long cycle stability.
[0023] This application provides an embodiment of a sulfide solid electrolyte membrane, comprising a composite support and a gradient-doped electrolyte layer for forming at least one surface of the composite support.
[0024] In some embodiments, the composite support comprises boron-doped nanocellulose and boron nitride nanosheets dispersed in the boron-doped nanocellulose.
[0025] For example, the boron doping content in the boron-doped nanocellulose is 0.5 wt% to 2.0 wt%, the diameter of the boron in the boron-doped nanocellulose is 20 nm to 50 nm, and the length of the boron in the boron-doped nanocellulose is 1 μm to 5 μm.
[0026] For example, the boron nitride nanosheets have a thickness of 1 nm to 5 nm and a lateral dimension of 0.5 μm to 2 μm.
[0027] In some embodiments, the gradient-doped electrolyte layer is a sulfide solid electrolyte layer, and the gradient-doped electrolyte layer has a doping concentration that varies along the direction away from the composite support.
[0028] For example, the gradient-doped electrolyte layer includes a low-doped layer and a high-doped layer; the low-doped layer is located further away from the composite support than the high-doped layer.
[0029] For example, the gradient-doped electrolyte layer comprises a sulfide solid electrolyte, a halide dopant, and a polyetheramine, wherein the polyetheramine and the sulfide solid electrolyte form a covalent network through cross-linking.
[0030] Preferably, the sulfide solid electrolyte is Li7P3S. 11 .
[0031] For example, the mass of the halide dopant in the low-doped layer accounts for 0.5% to 2% of the total mass of the sulfide solid electrolyte, the halide dopant, and the polyetheramine; the mass of the halide dopant in the high-doped layer accounts for 2% to 5% of the total mass of the sulfide solid electrolyte, the halide dopant, and the polyetheramine.
[0032] Preferably, the halide dopant is lithium bromide and / or lithium iodide.
[0033] Preferably, the composite support has a thickness of 2 μm to 6 μm and a porosity of 40% to 60%; the low-doped layer has a thickness of 5 μm to 12 μm, the high-doped layer has a thickness of 3 μm to 8 μm, and the sulfide solid electrolyte membrane has a thickness of 15 μm to 30 μm.
[0034] See attached document Figure 1 and attached Figure 2 The particulate matter shown is a sulfide solid electrolyte (Li7P3S). 11 The adhesion between particles shown reflects the covalent network structure formed by in-situ crosslinking between polyetheramine and sulfide. (See attached image.) Figure 1 The image shown is a low-magnification SEM image (1.00kx, 50.0μm scale bar). Figure 1 The macroscopic uniformity of the electrolyte membrane surface is demonstrated, showing that the electrolyte particles are extremely uniformly distributed on the membrane surface, without obvious cracks or large pore defects; as shown in the attached image. Figure 2 The image shown is a high-magnification SEM image (5.00kx, 10.0μm scale bar), which focuses on microscopic details. Figure 2 The image clearly shows the morphology, particle size distribution, and tight contact interfaces between the electrolyte particles. (Attached) Figure 1 and attached Figure 2The global and local structures of the sulfide solid electrolyte are shown respectively, with appendices. Figure 1 This demonstrates the controllability and uniformity of the film formation process. Figure 2 This demonstrates the deep integration of active materials and polymer matrices at the microscale. (See attached image.) Figure 1 and attached Figure 2 This confirms the in-situ crosslinking effect of this application, showing blurred interparticle boundaries and a continuous phase structure, proving that the polyetheramine binder and the sulfide electrolyte underwent an in-situ crosslinking reaction, forming a dense covalent network; based on the attached... Figure 1 and attached Figure 2 The tight contact between particles and the encapsulation of the cross-linked network ensure a continuous ion transport path inside the electrolyte layer, realizing the structural basis for high ion conductivity and establishing a continuous ion transport channel.
[0035] This application embodiment achieves high ionic conductivity on the support side and maintains good chemical stability on the contact electrode side by designing a concentration gradient structure from the highly doped support side to the low-doped electrode side, thus resolving the contradiction between high ionic conductivity and interfacial chemical stability that is difficult to achieve with single uniform doping. This application embodiment also uses heat treatment to induce in-situ crosslinking between the polyetheramine binder and the sulfide electrolyte, forming a covalent network. This not only enhances the mechanical strength of the electrolyte membrane and suppresses microcrack formation but also significantly improves the interfacial bonding within the electrolyte layer and between layers, providing continuous ion transport channels and reducing interfacial impedance. This application embodiment uses boron-doped nanocellulose and boron nitride nanosheets to construct a composite support. The mechanical strength of the nanocellulose forms the support framework, while the boron nitride nanosheets improve thermal conductivity and flame retardancy. Both components have a certain lithium-ion conductivity, avoiding the ionic insulation problem caused by using a completely inert support. This achieves ultrathinness and enhances mechanical and thermal properties while minimizing the negative impact on overall ionic conductivity.
[0036] This application also discloses a preparation method for preparing the sulfide solid electrolyte membrane as described above, comprising the following steps S1 to S4.
[0037] Step S1: Disperse boron-doped nanocellulose in water, add boron nitride nanosheets and crosslinking agent to react, perform film formation and drying treatment to obtain boron-doped nanocellulose-boron nitride nanosheet composite support.
[0038] In this context, step S1 can be understood as the preparation step of the boron-doped nanocellulose-boron nitride nanosheet composite support.
[0039] For example, step S1 includes: dispersing boron-doped nanocellulose in deionized water to prepare a dispersion with a mass concentration of 0.2~1.5 g / L; adding boron nitride nanosheets, ultrasonically dispersing for 30~60 min, adding the crosslinking agent glutaraldehyde, and stirring the reaction at 50~60℃ for 6~12 h; after the reaction is completed, filtering to form a film, and vacuum drying to obtain a boron-doped nanocellulose-boron nitride nanosheet composite support.
[0040] Step S2: Prepare highly doped sulfide electrolyte slurries and low doped sulfide electrolyte slurries with different halide dopant contents, respectively.
[0041] In this context, step S2 can be understood as the preparation step of gradient-doped sulfide electrolyte slurry.
[0042] For example, step S2 includes: preparing a highly doped sulfide electrolyte slurry and a low-doped sulfide electrolyte slurry respectively: High-doped slurry: Li7P3S... 11 Dopant LiBr / LiI and polyetheramine binder are dispersed in a DMC-EMC (dimethyl carbonate-ethyl methyl carbonate) mixed solvent at a mass ratio of (92~97):(2~5):(1~3), and the mixture is degassed and stirred to obtain a slurry with a solid content of 30%~60%; Low-doped slurry: Li7P3S 11 The dopant LiBr / LiI and polyetheramine binder are dispersed in a DMC-EMC mixed solvent at a mass ratio of (96~99):(0.5~2):(0.5~2), and the mixture is degassed and stirred to obtain a slurry with a solid content of 30%~60%.
[0043] Step S3: The low-doped sulfide electrolyte slurry and the high-doped sulfide electrolyte slurry are sequentially coated on the substrate to form an electrolyte membrane precursor with a gradient structure, and then heat-treated to allow the polyetheramine in the low-doped sulfide electrolyte slurry and the high-doped sulfide electrolyte slurry to undergo an in-situ crosslinking reaction with the sulfide solid electrolyte.
[0044] Step S3 can be understood as the gradient electrolyte membrane coating and interface crosslinking step.
[0045] For example, step S3 includes: first coating a low-doped sulfide electrolyte slurry onto a polyimide substrate, drying it, and then coating it with a high-doped sulfide electrolyte slurry to form a gradient structure electrolyte membrane; and then heat-treating it at 80~100℃ for 1~2h to allow the polyetheramine and sulfide electrolyte to undergo an in-situ crosslinking reaction.
[0046] Step S4: The highly doped sides of the two heat-treated electrolyte membrane precursors are respectively attached to both sides of the composite support, and then subjected to cold pressing and substrate peeling to obtain the sulfide solid electrolyte membrane.
[0047] Step S4 can be understood as a composite pressing and transfer step.
[0048] For example, step S4 includes: attaching the highly doped sides of two gradient structure electrolyte membranes to both sides of a boron-doped nanocellulose-boron nitride nanosheet composite support, cold pressing under a pressure of 200~400MPa for 5~10min, peeling off the polyimide substrate, and obtaining a gradient doped interfacial cross-linked ultrathin sulfide solid electrolyte membrane with a thickness of 15~30μm.
[0049] In some embodiments, in the highly doped sulfide electrolyte slurry, the halide dopant accounts for 2 wt% to 5 wt% of the total mass of the sulfide solid electrolyte, halide dopant, and polyetheramine; in the low-doped sulfide electrolyte slurry, the halide dopant accounts for 0.5 wt% to 2 wt% of the total mass of the sulfide solid electrolyte, halide dopant, and polyetheramine.
[0050] In some embodiments, the boron nitride nanosheets have a thickness of 1 nm to 5 nm, a lateral dimension of 0.5 μm to 2 μm, and a mass ratio of 1:(3~10) to boron-doped nanocellulose.
[0051] In some embodiments, the volume ratio of DMC to EMC in the DMC-EMC mixed solvent is (1~3):1.
[0052] In some embodiments, the thickness of the low-doped layer is 5 μm to 12 μm, and the thickness of the high-doped layer is 3 μm to 8 μm.
[0053] In some embodiments, the composite support has a thickness of 2 μm to 6 μm and a porosity of 40% to 60%.
[0054] This application describes a preparation method that first employs a gradient coating process, starting with low concentrations and gradually increasing with higher concentrations, to construct an electrolyte layer with doping concentrations increasing from the electrode side to the support side. This structurally achieves a balance between interfacial chemical stability and high bulk ionic conductivity. Secondly, a heat treatment step is introduced to induce in-situ crosslinking between the polyetheramine and the sulfide electrolyte, forming a covalent bond network within and between the electrolyte layers. This simultaneously enhances the mechanical integrity of the membrane and provides continuous ion transport channels, significantly reducing interfacial impedance. Finally, a functional support composed of boron-doped cellulose nanosheets and boron nitride nanosheets is pre-prepared and then composited and pressed with the gradient electrolyte layer in the final step. This support provides excellent mechanical strength and thermal stability while avoiding the severe obstruction of ion conduction by traditional inert frameworks, offering a reliable pathway to achieve ultrathin, high-strength, and high-conductivity electrolyte membranes.
[0055] This application also discloses a solid-state battery, including a positive electrode, a negative electrode, and a sulfide solid electrolyte membrane disposed between the positive electrode and the negative electrode. For example, the solid-state battery includes an ultrathin sulfide solid electrolyte membrane, a lithium iron phosphate positive electrode, and a lithium metal negative electrode.
[0056] The core advantage of this solid-state battery embodiment lies in the simultaneous improvement of overall battery performance. Gradient doping and interfacial cross-linking structures jointly ensure that the battery has extremely low interfacial impedance and excellent interfacial stability during operation, giving the battery faster rate response and longer cycle life. At the same time, the high strength and high toughness of the composite support can effectively suppress lithium dendrite puncture during cycling, significantly improving the intrinsic safety of the battery; the introduction of boron nitride nanosheets also enhances the battery's thermal management capability; this solid-state battery structure fundamentally overcomes the contradiction between high ionic conductivity and interfacial / chemical stability in traditional sulfide solid-state batteries.
[0057] The following discloses a specific process of an embodiment of this application. This process demonstrates the differences in the embodiment of this application under different conditions of related components or ingredients and the comparison with related technology comparative examples by adjusting different parameters in Examples 1 to 10 and Comparative Examples 1 to 3.
[0058] Example 1: The composite support preparation stage includes: dispersing 100 mg of boron-doped cellulose nanofibers with a boron doping concentration of 1.0 wt% in 100 mL of deionized water to prepare a 1 g / L dispersion; adding 20 mg of boron nitride nanosheets and ultrasonically dispersing for 45 min; adding 0.5 mL of 25 wt% glutaraldehyde aqueous solution and stirring at 55 °C for 8 h; filtering to form a film and vacuum drying at 60 °C for 12 h to obtain a composite support with a thickness of 4 μm. The gradient electrolyte slurry preparation stage includes: the high-doped slurry preparation stage: dispersing 9.5 g of Li7P3S... 11 0.3g LiBr and 0.2g polyetheramine (PEA-2000) were dispersed in 15mL LDC-EMC (2:1) mixed solvent and vacuum degassed and stirred for 2h to obtain a slurry with a solid content of 40%; and in the low-doped slurry preparation stage: 9.8g Li7P3S 110.1 g LiBr and 0.1 g polyetheramine were dispersed in 15 mL of LDC-EMC (2:1) mixed solvent and vacuum degassed and stirred for 2 h to obtain a slurry with a solid content of 40%. The gradient film coating and crosslinking stage included: first, coating a 30 μm thick layer of low-doped slurry onto a 25 μm thick polyimide substrate, followed by vacuum drying at 60 °C for 30 min; then coating a 20 μm thick layer of high-doped slurry, followed by vacuum drying at 60 °C for 30 min; and finally heat-treating at 90 °C for 1.5 h to complete in-situ crosslinking. The composite pressing stage included: attaching the high-doped sides of the two gradient electrolyte films to both sides of the composite support, cold pressing at 300 MPa for 8 min, and then peeling off the polyimide substrate to obtain an ultrathin sulfide solid electrolyte film with a total thickness of 22 μm. The battery assembly stage includes: stacking lithium iron phosphate positive electrode (area capacity 2.0mAh / cm²), the above-mentioned electrolyte membrane, and a 50μm thick lithium metal negative electrode in an argon glove box (water ≤0.01ppm, oxygen ≤0.01ppm), encapsulating them in an aluminum-plastic film, and performing isostatic pressing at 300MPa to obtain an energy storage solid-state battery.
[0059] Example 2 differs from Example 1 only in that the amount of boron nitride nanosheets added in the preparation of the composite support is 15 mg.
[0060] Example 3 differs from Example 1 only in that the amount of boron nitride nanosheets added in the preparation of the composite support is 25 mg.
[0061] Example 4 differs from Example 1 only in that the amount of LiBr added in the highly doped slurry is 0.2g.
[0062] Example 5 differs from Example 1 only in that the amount of LiBr added in the highly doped slurry is 0.4g.
[0063] Example 6 differs from Example 1 only in that the dopant is replaced by an equal mass of LiI instead of LiBr.
[0064] Example 7 differs from Example 1 only in that the polyetheramine adhesive is replaced with PEA-4000 instead of PEA-2000.
[0065] Example 8 differs from Example 1 only in that the in-situ crosslinking heat treatment temperature is 85°C and the time is 2 hours.
[0066] Example 9 differs from Example 1 only in that the cold pressing pressure is 250 MPa and the time is 10 min.
[0067] Example 10 differs from Example 1 only in that the total thickness of the final electrolyte membrane is 18 μm.
[0068] Comparative Example 1 differs from Example 1 only in that: a gradient doping structure was not used, the electrolyte membrane was uniformly doped (LiBr content 0.2wt%), and the total thickness was still 22μm.
[0069] Comparative Example 2 differs from Example 1 only in that it does not undergo in-situ crosslinking heat treatment; the other steps are the same.
[0070] Comparative Example 3 differs from Example 1 only in that the composite support is replaced with a pure boron-doped nanocellulose membrane (without boron nitride nanosheets), while the thickness remains 4 μm.
[0071] The mechanical strength test conditions for Examples 1 to 10 and Comparative Examples 1 to 3 were as follows: a universal testing machine was used to test the tensile strength and elongation at break according to the GB / T1040.3-2006 standard, with a tensile rate of 5 mm / min.
[0072] The room temperature ionic conductivity test conditions for Examples 1 to 10 and Comparative Examples 1 to 3 were all configured as follows: AC impedance method (frequency range 10). - ¹-10 6 The conductivity σ = L / (R×S) was measured at Hz (amplitude 5mV), where L is the film thickness, R is the impedance value, and S is the electrode area.
[0073] The lithium dendrite suppression performance test conditions for Examples 1 to 10 and Comparative Examples 1 to 3 were as follows: Li / electrolyte membrane / Li symmetric cells were assembled, constant current charge-discharge tests were performed at a current density of 0.5 mA / cm², and the battery short-circuit time was recorded.
[0074] The experimental results of Examples 1 to 10 and Comparative Examples 1 to 3 are shown in Table 1 below: Table 1: Experimental Results of Examples 1 to 10 and Comparative Examples 1 to 3
[0075] From Table 1, Figure 3 and Figure 4As can be seen, comparing Example 1 with Comparative Example 1, the gradient doping structure increases the ionic conductivity from 8.7 mS / cm to 12.8 mS / cm and significantly reduces the interfacial impedance. This is because the highly doped layer provides a fast ion conduction channel, while the low-doped layer reduces side reactions with lithium metal and improves interfacial contact. Comparing Example 1 with Comparative Example 2, in-situ crosslinking increases the tensile strength from 22.4 MPa to 38.5 MPa and the elongation at break from 6.8% to 12.3%. The covalent network formed by the polyetheramine and the sulfide electrolyte not only enhances the mechanical properties of the film but also provides a continuous ion conduction path, effectively suppressing interfacial separation and microcrack formation. Comparing Example 1 with Comparative Example 3, the addition of boron nitride nanosheets increases the tensile strength from 29.6 MPa to 38.5 MPa and extends the lithium dendrite short-circuit time from 850 h to over 1200 h. Boron nitride nanosheets possess excellent mechanical strength and thermal conductivity, enabling them to disperse stress and rapidly dissipate heat, significantly improving the electrolyte membrane's resistance to lithium dendrite formation and its thermal stability. Example 10 reduced the electrolyte membrane thickness to 18 μm, further enhancing ionic conductivity and rate performance, but slightly decreasing mechanical strength.
[0076] This application employs a gradient doping structure design, where the electrolyte membrane exhibits a doping concentration gradient from the support side to the electrode side. High doping on the support side enhances ionic conductivity, while low doping on the electrode side strengthens chemical stability, resolving the contradiction between conductivity and stability in single-doped electrolytes. This application also utilizes in-situ interfacial crosslinking technology, where polyetheramine and sulfide electrolytes form a covalent network during heat treatment, significantly enhancing interfacial bonding and providing continuous ion conduction channels, thus reducing interfacial impedance. Furthermore, this application employs a functionalized composite support. Boron-doped nanocellulose provides high mechanical strength, while boron nitride nanosheets improve thermal conductivity and flame retardancy. Both components possess a certain lithium-ion conductivity, avoiding the ion insulation problems associated with inert supports.
[0077] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of this application, and this application is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this application, and these modifications and improvements are also considered to be within the scope of protection of this application.
Claims
1. A sulfide solid electrolyte membrane, characterized in that, Includes a composite support and a gradient-doped electrolyte layer for forming at least one surface of the composite support; The composite support comprises boron-doped nanocellulose and boron nitride nanosheets dispersed in the boron-doped nanocellulose; The gradient-doped electrolyte layer is a sulfide solid electrolyte layer, and the gradient-doped electrolyte layer has a doping concentration that varies along the direction away from the composite support.
2. The sulfide solid electrolyte membrane according to claim 1, characterized in that, The gradient-doped electrolyte layer includes a low-doped layer and a high-doped layer; the low-doped layer is farther away from the composite support than the high-doped layer.
3. The sulfide solid electrolyte membrane according to claim 2, characterized in that, The gradient-doped electrolyte layer comprises a sulfide solid electrolyte, a halide dopant, and a polyetheramine, wherein the polyetheramine and the sulfide solid electrolyte form a covalent network through cross-linking.
4. The sulfide solid electrolyte membrane according to claim 3, characterized in that, The sulfide solid electrolyte is Li7P3S. 11 .
5. The sulfide solid electrolyte membrane according to claim 3, characterized in that, The mass of the halide dopant in the low-doped layer accounts for 0.5% to 2% of the total mass of the sulfide solid electrolyte, the halide dopant, and the polyetheramine; The mass of the halide dopant in the highly doped layer accounts for 2% to 5% of the total mass of the sulfide solid electrolyte, the halide dopant, and the polyetheramine.
6. The sulfide solid electrolyte membrane according to claim 5, characterized in that, The halide dopant is lithium bromide and / or lithium iodide.
7. The sulfide solid electrolyte membrane according to claim 1, characterized in that, The boron doping content in the boron-doped nanocellulose is 0.5 wt% to 2.0 wt%, the diameter of the boron in the boron-doped nanocellulose is 20 nm to 50 nm, and the length of the boron in the boron-doped nanocellulose is 1 μm to 5 μm; the thickness of the boron nitride nanosheet is 1 nm to 5 nm, and the lateral dimension of the boron nitride nanosheet is 0.5 μm to 2 μm.
8. The sulfide solid electrolyte membrane according to claim 2, characterized in that, The composite support has a thickness of 2μm to 6μm and a porosity of 40%-60%. The thickness of the low-doped layer is 5 μm to 12 μm, and the thickness of the high-doped layer is 3 μm to 8 μm; The thickness of the sulfide solid electrolyte membrane is 15 μm to 30 μm.
9. A preparation method for preparing a sulfide solid electrolyte membrane as described in any one of claims 1 to 8, characterized in that, include: Boron-doped cellulose nanofibers were dispersed in water, and boron nitride nanosheets and a crosslinking agent were added to react, followed by film formation and drying to obtain a boron-doped cellulose nanofibers-boron nitride nanosheet composite support. High-doped sulfide electrolyte slurries and low-doped sulfide electrolyte slurries with different halide dopant contents were prepared respectively. The low-doped sulfide electrolyte slurry and the high-doped sulfide electrolyte slurry are sequentially coated on the substrate to form an electrolyte membrane precursor with a gradient structure. The precursor is then heat-treated to allow the polyetheramine in the low-doped sulfide electrolyte slurry and the high-doped sulfide electrolyte slurry to undergo an in-situ crosslinking reaction with the sulfide solid electrolyte. The highly doped sides of the two heat-treated electrolyte membrane precursors are respectively attached to both sides of the composite support, and then subjected to cold pressing and substrate peeling to obtain the sulfide solid electrolyte membrane.
10. A solid-state battery, characterized in that, It includes a positive electrode, a negative electrode, and a sulfide solid electrolyte membrane disposed between the positive electrode and the negative electrode as described in any one of claims 1 to 8.