Ultra-thin strong and tough high-conductivity solid-state polymer electrolyte membrane, preparation method and application thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SUN YAT SEN UNIV
- Filing Date
- 2026-05-20
- Publication Date
- 2026-08-07
AI Technical Summary
[0005]本申请提供一种超薄强韧高导固态聚合物电解质膜及其制备方法和应用，旨在解决现有固态聚合物电解质存在的离子导电率低、界面稳定性差的技术问题
本申请制备的固态聚合物电解质膜中，一维杂化高分子刷以刚性细菌纤维素为基底，其侧链中的磺酸基团可以与LLZTO填料表面碱性惰性层发生原位反应，转变为锂离子活性的磺酸锂基团。界面磺酸锂基团可以提供快速的Li+传输通道，同时负电荷中心可以通过静电相互作用抑制阴离子的扩散，提高界面离子扩散速度，并有效抑制电解质中有机-无机界面空间电荷层的形成，从而提高聚合物电解质的离子电导率和锂离子迁移数，有利于实现快速的界面离子传输；并且磺酸锂基团可以均匀锂离子流，促进均匀的锂金属沉积行为，原位构建富含无机组分的CEI/SEI界面层。此外，固态聚合物电解质膜中刚性的细菌纤维素和LLZTO填料可协同实现聚合物电解质的力学性能，有利于抑制缓解电池充放电过程中的体积变化。
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Abstract
Description
Technical Field
[0001] This application relates to the field of solid polymer electrolyte technology for lithium-ion batteries, and in particular to an ultrathin, strong, and highly conductive solid polymer electrolyte membrane, its preparation method, and its application. Background Technology
[0002] Lithium-ion batteries, with their high energy density and long cycle life, have become the most widely used rechargeable battery technology in the world today. With the increasing demand for batteries with higher energy density and lower cost, intercalated cathodes (~250 mAh g⁻¹) are increasingly being adopted. -1 ) and graphite anode (372 mAh g) -1 The energy density of commercial lithium-ion batteries is gradually becoming insufficient to meet future development needs, making high-capacity silicon-carbon anodes and lithium metal anodes the two core research directions for next-generation battery systems. However, both silicon-carbon and lithium metal anodes face insurmountable application bottlenecks in liquid systems. During cycling, they undergo continuous volume changes, leading to irreversible regeneration of the solid electrolyte interface, ultimately significantly reducing the battery's cycle life and failing to meet the application requirements of long-cycle power batteries.
[0003] Developing solid-state batteries based on solid-state electrolytes is an important way to solve the safety problems of high-energy-density lithium batteries and improve their cycle life. An ideal solid-state electrolyte should possess the following characteristics: high ionic conductivity (>10⁻⁶) over a wide temperature range. -3 S cm -1 PVDF-based polymer electrolytes possess excellent mechanical properties and high electrochemical and thermal stability, showing great application potential in solid-state lithium batteries. However, their ionic conductivity is relatively low. Adding inorganic ceramic particles (such as lithium lanthanum zirconium tantalum oxide, LLZTO) can reduce the crystallinity of PVDF electrolytes and enhance their ionic conductivity. Simultaneously, the higher mechanical modulus of inorganic fillers can provide better mechanical strength to the electrolyte membrane. For example, PHLP-15 electrolyte membranes are obtained by combining P-DOL-coated LLZTO particles with PVDF-HFP polymers. The conjugated structure of the P-DOL polymer layer on the LLZTO filler surface can promote lithium salt dissociation and effectively alleviate the potential difference at the organic / inorganic interface, which is beneficial for the rapid transport of lithium ions in the charge-rich space charge layer. However, when using LLZTO ceramic particles as PVDF fillers, the presence of Li2CO3 and LiOH passivation layers on the particle surface not only induces PVDF to remove HF and form -CH=CF-, affecting its high-pressure stability, but also the inert passivation layer hinders ion transport at the organic / inorganic interface, reducing the ionic conductivity of the electrolyte membrane.
[0004] Therefore, it is of great significance to develop novel solid polymer electrolytes with high ionic conductivity and stable interfaces. Summary of the Invention
[0005] This application provides an ultrathin, strong, and highly conductive solid polymer electrolyte membrane, its preparation method, and its application, aiming to solve the technical problems of low ionic conductivity and poor interface stability in existing solid polymer electrolytes.
[0006] To achieve the above objectives, the present application adopts the following technical solution.
[0007] A first aspect of this application provides a method for preparing an ultrathin, strong, and highly conductive solid polymer electrolyte membrane, comprising the following steps: S1, bacterial cellulose is reacted with 2-bromoisobutyryl bromide via esterification to obtain bromine-modified bacterial cellulose; S2, the bromine-modified bacterial cellulose and a polymer monomer containing sulfonic acid groups are polymerized to graft polymer side chains onto its surface to obtain a one-dimensional polymer brush; S3, the one-dimensional polymer brush and lithium lanthanum zirconium tantalum oxide (LLZTO) are dispersed in a first organic solvent to obtain a filler dispersion; the filler dispersion, lithium salt and PVDF are dispersed in the first organic solvent, mixed evenly, and then coated onto the substrate surface and dried to obtain an ultrathin, strong and tough high-conductivity solid polymer electrolyte membrane.
[0008] Preferably, step S1 specifically includes: Bacterial cellulose was dispersed in N,N-dimethylformamide, and 4-dimethylaminopyridine and triethylamine were added and mixed thoroughly. 2-Bromoisobutyryl bromide was added dropwise to the above mixture at 0 °C under an inert atmosphere. The mixture was heated to 30 °C and stirred for 24 h. The reaction was quenched with ethanol. The solid product was collected, washed, and dried to obtain bromine-modified bacterial cellulose.
[0009] More preferably, the mass-to-volume ratio of bacterial cellulose to N,N-dimethylformamide is 1~5 mg / mL; The mass ratio of bacterial cellulose to 4-dimethylaminopyridine is 1:1~3; The mass-to-volume ratio of bacterial cellulose to triethylamine and 2-bromoisobutyryl bromide was 1 mg: 20-50 μL: 20-40 μL.
[0010] Preferably, step S2 specifically includes: Bromine-modified bacterial cellulose was dispersed in a second organic solvent, and a polymer monomer containing sulfonic acid groups, tris(2-pyridylmethyl)amine, copper bromide, and vitamin C were added. The mixture was heated to 60-70 °C and reacted under an inert atmosphere. The solid product was collected, washed, and the intermediate product was obtained. The intermediate product was dispersed in deionized water, a strong acid solution was added, and the mixture was stirred until homogeneous. The solid phase was collected, washed, and a one-dimensional polymer brush was obtained.
[0011] More preferably, the polymer monomer containing sulfonic acid groups includes at least one of sodium p-styrenesulfonate, potassium 3-sulfonopropyl methacrylate, or 2-acrylamide-2-methylpropanesulfonic acid; The strong acid solution is nitric acid or hydrochloric acid; The second organic solvent includes at least one of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, or tetrahydrofuran; And / or, The mass ratio of the brominated bacterial cellulose, the polymer monomer containing sulfonic acid groups, tris(2-pyridylmethyl)amine, copper bromide, and vitamin C is 1:20~60:0.5~0.9:0.05~0.1:0.2~0.35; The mass-to-volume ratio of bromine-modified bacterial cellulose to the second organic solvent is 1 mg: 0.5~1.5 mL.
[0012] Preferably, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, or lithium difluorooxalateborate. The first organic solvent is N,N-dimethylformamide; And / or, The concentration of the one-dimensional polymer brush in the filler dispersion is 50~60 mg / mL; The mass ratio of the one-dimensional polymer brush to lithium lanthanum zirconium tantalum oxide is 0.25~0.5:1; The mass ratio of one-dimensional polymer brush to polyvinylidene fluoride is 1:3~4; The mass ratio of polyvinylidene fluoride to lithium salt is 1~2:1; The mass-to-volume ratio of polyvinylidene fluoride to N,N-dimethylformamide is 1 mg / 1.5~3 mL; And / or, The thickness of the ultrathin, strong, and highly conductive solid polymer electrolyte membrane is 15~20 μm.
[0013] A second aspect of this application provides an ultrathin, strong, and highly conductive solid polymer electrolyte membrane prepared by the above-described preparation method.
[0014] A third aspect of this application provides the application of the aforementioned ultrathin, strong, and highly conductive solid polymer electrolyte membrane in lithium batteries.
[0015] Preferably, during the assembly of the lithium battery, a plasticizer is dropped into the ultrathin, strong, and highly conductive solid polymer electrolyte membrane; The plasticizer includes at least one of ethylene carbonate, fluoroethylene carbonate, methyl trifluoroethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene ethylene carbonate, or ethylene carbonate. The dosage of plasticizer is 0.1~0.5 μL / cm³. 2 .
[0016] A fifth aspect of this application provides a solid-state lithium battery, which includes a positive electrode, a negative electrode, and a solid electrolyte. The positive electrode is any one of lithium iron phosphate, lithium nickel cobalt manganese oxide, or lithium cobalt oxide. The negative electrode is any one of lithium metal, graphite, or silicon-carbon. The solid electrolyte is the aforementioned ultrathin, strong, and highly conductive solid polymer electrolyte membrane.
[0017] Compared with the prior art, the beneficial effects of this application are as follows: In the solid polymer electrolyte membrane prepared in this application, the one-dimensional hybrid polymer brush uses rigid bacterial cellulose as a substrate. The sulfonic acid groups in its side chains can react in situ with the alkaline inert layer on the surface of the LLZTO filler, transforming into lithium-ion-active lithium sulfonate groups. The interfacial lithium sulfonate groups can provide rapid Li-ionization... + The transport channels, along with the negative charge centers, can suppress anion diffusion through electrostatic interactions, increasing the interfacial ion diffusion rate and effectively inhibiting the formation of a space charge layer at the organic-inorganic interface in the electrolyte. This improves the ionic conductivity and lithium-ion transference number of the polymer electrolyte, facilitating rapid interfacial ion transport. Furthermore, lithium sulfonate groups can uniformly distribute lithium-ion flow, promoting uniform lithium metal deposition and in-situ constructing an inorganic-rich CEI / SEI interfacial layer. In addition, the rigid bacterial cellulose and LLZTO fillers in the solid polymer electrolyte membrane synergistically enhance the mechanical properties of the polymer electrolyte, helping to suppress and mitigate volume changes during battery charging and discharging.
[0018] Based on the above synergistic effects, the solid polymer electrolyte membrane of this application possesses ultra-high room temperature ionic conductivity, good mechanical strength, and excellent electrochemical performance, making it suitable for use in wide-temperature-range lithium batteries. Lithium batteries incorporating the solid polymer electrolyte membrane of this application exhibit excellent capacity retention and cycle stability. Attached Figure Description
[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 The image shows a scanning electron microscope (SEM) image of the surface of bacterial cellulose and intermediate products from Example 1. Figure 2 Images of polymer films BPALP, BLP, LP, and PVDF; Figure 3 Scanning electron microscope (SEM) images of the surfaces of polymer films BPALP, BLP, LP, and PVDF; Figure 4 Stress-strain curves of polymer films BPALP, BLP, LP and PVDF; Figure 5 Atomic force microscopy Young's modulus distribution of solid polymer electrolyte membranes BPALP / P, BLP / P, LP / P, and PVDF / P; Figure 6 Impedance spectra and ionic conductivity-temperature curves for solid polymer electrolyte membranes BPALP / P, BLP / P, LP / P, and PVDF / P. Figure 7 Linear scan voltammetric curves of solid polymer electrolyte membranes BPALP / P, BLP / P, LP / P, and PVDF / P; Figure 8 Critical current density test results for solid polymer electrolyte membranes BPALP / P, BLP / P, LP / P, and PVDF / P; Figure 9 Cyclic performance test results of Li|Li symmetric cells assembled with solid polymer electrolyte membranes BPALP / P, BLP / P, LP / P and PVDF / P; Figure 10 Cyclic performance test results of NCM811 full cells assembled with solid polymer electrolyte membranes BPALP / P, BLP / P, LP / P and PVDF / P; Figure 11 Cyclic performance test results of full cells assembled with solid polymer electrolyte membrane BPALP / P at -20 °C and 100 °C. Detailed Implementation
[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0022] In the following description of this embodiment, the terms "including", "comprising", "having", and "containing" are all open-ended terms, meaning that they include but are not limited to.
[0023] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.
[0024] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.
[0025] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.
[0026] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.
[0027] Those skilled in the art will understand that the numerical ranges in the embodiments of this application should be understood as each intermediate value between the upper and lower limits of the specifically disclosed range. Each smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0028] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.
[0029] A first aspect of this application provides a method for preparing an ultrathin, strong, and highly conductive solid polymer electrolyte membrane, comprising the following steps: S1, bacterial cellulose (BC) is reacted with 2-bromoisobutyryl bromide via an esterification reaction to obtain bromine-modified bacterial cellulose. The specific steps include: Bacterial cellulose was dispersed in N,N-dimethylformamide, and 4-dimethylaminopyridine and triethylamine were added and mixed thoroughly. 2-Bromoisobutyryl bromide was added dropwise to the above mixture at 0 ℃ under an inert atmosphere, and the mixture was heated to 30 ℃ and stirred for 24 h to carry out the esterification reaction. After the reaction, ethanol was added to quench the reaction, the solid product was collected, washed repeatedly with N,N-dimethylformamide, and dried to obtain bromine-modified bacterial cellulose.
[0030] The bacterial cellulose to N,N-dimethylformamide mass-to-volume ratio is 1-5 mg / mL, preferably 3 mg / mL; the bacterial cellulose to 4-dimethylaminopyridine mass ratio is 1:1-3, preferably 1:1.95.
[0031] The mass-to-volume ratio of bacterial cellulose to triethylamine and 2-bromoisobutyryl bromide is 1 mg:20~50 μL:20~40 μL, preferably 1 mg:30 μL:33 μL.
[0032] S2, the bromine-modified bacterial cellulose is polymerized with a polymer monomer containing sulfonic acid groups to graft polymer side chains onto its surface, obtaining a one-dimensional polymer brush. Specifically, this includes the following steps: Bromine-modified bacterial cellulose was dispersed in a second organic solvent, and a polymer monomer containing sulfonic acid groups, tris(2-pyridylmethyl)amine, copper bromide, and vitamin C were added. The mixture was heated to 60-70 °C and reacted under an inert atmosphere. The solid product was collected and washed with deionized water to obtain the intermediate product. The intermediate product was dispersed in deionized water, and a strong acid solution was added and stirred until homogeneous. The solid phase was collected and washed to obtain a one-dimensional polymer brush. Preferably, the washing was performed three times sequentially with deionized water and N,N-dimethylformamide.
[0033] In this application, the polymer monomer containing sulfonic acid groups includes at least one of sodium p-styrene sulfonate, potassium 3-sulfonopropyl methacrylate, or 2-acrylamide-2-methylpropanesulfonic acid, preferably sodium p-styrene sulfonate; the strong acid solution is nitric acid or hydrochloric acid.
[0034] By reacting polymers containing sulfonic acid groups, such as sodium p-styrene sulfonate and potassium 3-sulfonopropyl methacrylate, with a strong acid solution, hydrogen ions replace metal ions, resulting in metal ion-free polymer monomers containing sulfonic acid groups, such as p-styrene sulfonic acid and 3-sulfonopropyl methacrylate.
[0035] The second organic solvent includes at least one of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, or tetrahydrofuran.
[0036] In this application, the mass ratio of the bromine-modified bacterial cellulose, the polymer monomer containing sulfonic acid groups, tris(2-pyridylmethyl)amine, copper bromide, and vitamin C is 1:20~60:0.5~0.9:0.05~0.1:0.2~0.35, preferably 1:40:0.7:0.075:0.275.
[0037] The mass-to-volume ratio of bromine-modified bacterial cellulose to the second organic solvent is 1 mg: 0.5~1.5 mL, preferably 1 mg: 0.75 mL.
[0038] S3, the one-dimensional polymer brush and lithium lanthanum zirconium tantalum oxide (LLZTO) are dispersed in a first organic solvent to obtain a filler dispersion; the filler dispersion, lithium salt and PVDF are dispersed in the first organic solvent, mixed evenly, and then coated onto the substrate surface and dried to obtain an ultrathin, strong and tough high-conductivity solid polymer electrolyte membrane.
[0039] In this application, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, or lithium difluorooxalateborate. The first organic solvent is N,N-dimethylformamide.
[0040] In this application, the concentration of the one-dimensional polymer brush in the filler dispersion is preferably 50~60 mg / mL; The preferred mass ratio of the one-dimensional polymer brush to lithium lanthanum zirconium tantalum oxide is 0.25~0.5:1; the preferred mass ratio of the one-dimensional polymer brush to polyvinylidene fluoride is 1:3~4; the preferred mass ratio of polyvinylidene fluoride to lithium salt is 1~2:1, preferably 1:1; the preferred mass-volume ratio of polyvinylidene fluoride to N,N-dimethylformamide is 1 mg / 1.5~3 mL, preferably 1 mg / 2.5 mL.
[0041] In this application, the thickness of the ultrathin, strong, and highly conductive solid polymer electrolyte membrane is 15~20 μm.
[0042] The one-dimensional polymer brush prepared in this application uses rigid bacterial cellulose as a substrate. The sulfonic acid groups in its side chain can react in situ with the alkaline inert layer on the surface of the LLZTO filler to transform into lithium ion-active lithium sulfonate groups, thereby improving the ionic conductivity and lithium ion transference number of the polymer electrolyte, which is beneficial for achieving rapid interfacial ion transport. The rigid bacterial cellulose and LLZTO filler can synergistically improve the mechanical properties of the polymer electrolyte, which is beneficial for suppressing and mitigating volume changes during battery charging and discharging.
[0043] Specifically, the lithium sulfonate group at the interface can provide rapid Li + The transport channel, along with the negative charge center, can inhibit the diffusion of anions through electrostatic interaction, increase the diffusion rate of interfacial ions, and effectively suppress the formation of the space charge layer at the organic-inorganic interface in the electrolyte, thereby improving the ionic conductivity and lithium-ion transference number of the polymer electrolyte, which is conducive to achieving rapid interfacial ion transport; and the lithium sulfonate group can uniformly flow lithium ions, promote uniform lithium metal deposition behavior, and construct an inorganic-rich CEI / SEI interface layer in situ.
[0044] The ultrathin, tough, and highly conductive solid polymer electrolyte membrane prepared in this application exhibits ultra-high room temperature ionic conductivity, good mechanical strength, and excellent electrochemical performance based on the above synergistic effects. It can be used in lithium batteries, and is particularly suitable for assembling wide-temperature-range lithium batteries.
[0045] It should be noted that, when assembling lithium batteries, plasticizers can be added to the ultrathin, strong, and highly conductive solid polymer electrolyte membrane of this application to further enhance its electrochemical performance.
[0046] The plasticizer may be selected from at least one of ethylene carbonate, fluoroethylene carbonate, methyl trifluoroethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene ethylene carbonate, or ethylene carbonate. Based on the area of the ultrathin, strong, and highly conductive solid polymer electrolyte membrane, the amount of plasticizer used is 0.1~0.5 μL / cm². 2 .
[0047] This application also provides a solid-state lithium battery, which includes a positive electrode, a negative electrode, and a solid electrolyte; The positive electrode can be any one of lithium iron phosphate, lithium nickel cobalt manganese oxide, or lithium cobalt oxide; the negative electrode can be any one of lithium metal, graphite, or silicon carbon; and the solid electrolyte is the ultrathin, strong, and highly conductive solid polymer electrolyte membrane of this application.
[0048] The solid-state lithium battery containing the solid polymer electrolyte membrane of this application has excellent capacity retention and cycle stability.
[0049] The present application will be further described below through specific embodiments.
[0050] Example 1 This embodiment provides an ultrathin, strong, and highly conductive solid polymer electrolyte membrane, the preparation method of which includes the following steps: S1, 450 mg of bacterial cellulose (BC), 877 mg of 4-dimethylaminopyridine, and 13.3 mL of anhydrous triethylamine were added to 150 mL of deionized water and stirred thoroughly until homogeneous. 15 mL of 2-bromoisobutyryl bromide was slowly added using a constant pressure dropping funnel at 0 °C under an inert atmosphere. The reaction was then continued at 35 °C under an inert atmosphere for 24 h. The reaction was quenched with ethanol, followed by washing three times with ethanol, water, and N,N-dimethylformamide to obtain bromine-modified BC (BC-Br). S2, 200 mg of BC-Br, 8 g of sodium p-styrenesulfonate, 150 mg of tris(2-pyridylmethyl)amine, and 10 mg of copper bromide were added to 100 mL of N-methylpyrrolidone / dimethyl sulfoxide mixed solvent. After mixing evenly, 30 mg of ascorbic acid was added under an inert atmosphere, and then the temperature was raised to 65 °C. After reacting for 24 h, the product was washed three times by centrifugation with deionized water to obtain the intermediate product. The intermediate product was dispersed in 30 mL of deionized water and stirred evenly. Then, 5 mL of concentrated nitric acid was added and stirred for 10 min. The solid phase was collected and washed three times each with deionized water and N,N-dimethylformamide by centrifugation to obtain a one-dimensional hybrid polymer brush. S3, 15 mg of one-dimensional hybrid polymer brush and 40 mg of LLZTO ceramic filler were dispersed in 1 mL of N,N-dimethylformamide and stirred thoroughly for 24 h to obtain a dispersion; The dispersion, 200 mg of polyvinylidene fluoride, and 200 mg of lithium bis(trifluoromethanesulfonyl)imide were dispersed in 4 mL of N,N-dimethylformamide and stirred thoroughly for 24 h. Then, the mixture was coated onto the surface of a glass plate with a 500 μm thick doctor blade and dried in a 60 °C oven for 24 h to obtain a polymer film, denoted as BPALP.
[0051] Example 2 This embodiment provides an ultrathin, strong, and highly conductive solid polymer electrolyte membrane, the preparation method of which includes the following steps: S1, same as in Example 1; S2, same as in Example 1; S3, 10 mg of one-dimensional hybrid polymer brush and 40 mg of LLZTO ceramic filler were dispersed in 1 mL of N,N-dimethylformamide and stirred thoroughly for 24 h to obtain a dispersion; The dispersion, 200 mg of polyvinylidene fluoride, and 200 mg of lithium bis(trifluoromethanesulfonyl)imide were dispersed in 4 mL of N,N-dimethylformamide and stirred thoroughly for 24 h. Then, the mixture was coated onto the surface of a glass plate with a 500 μm thick doctor blade and dried in a 60 °C oven for 24 h to obtain a polymer film, denoted as BPALP-5.0.
[0052] Example 3 This embodiment provides an ultrathin, strong, and highly conductive solid polymer electrolyte membrane, the preparation method of which includes the following steps: S1, same as in Example 1; S2, same as in Example 1; S3, 20 mg of one-dimensional hybrid polymer brush and 40 mg of LLZTO ceramic filler were dispersed in 1 mL of N,N-dimethylformamide and stirred thoroughly for 24 h to obtain a dispersion; The dispersion, 200 mg of polyvinylidene fluoride, and 200 mg of lithium bis(trifluoromethanesulfonyl)imide were dispersed in 4 mL of N,N-dimethylformamide and stirred thoroughly for 24 h. Then, the mixture was coated onto the surface of a glass plate with a 500 μm thick doctor blade and dried in a 60 °C oven for 24 h to obtain a polymer film, denoted as BPALP-10.0.
[0053] Comparative Example 1 15 mg of BC and 40 mg of LLZTO ceramic filler were dispersed in 1 mL of N,N-dimethylformamide and stirred thoroughly for 24 h to obtain a dispersion. The dispersion, 200 mg of polyvinylidene fluoride, and 200 mg of lithium bis(trifluoromethanesulfonyl)imide were dispersed in 4 mL of N,N-dimethylformamide and stirred thoroughly for 24 h. Then, the mixture was coated onto the surface of a glass plate with a 500 μm thick doctor blade and dried in a 60 °C oven for 24 h to obtain a polymer film, denoted as BLP.
[0054] Comparative Example 2 40 mg of LLZTO ceramic filler, 200 mg of polyvinylidene fluoride, and 200 mg of lithium bis(trifluoromethanesulfonyl)imide were dispersed in 5 mL of N,N-dimethylformamide and stirred thoroughly for 24 h. The mixture was then coated onto the surface of a glass plate with a 500 μm thick doctor blade and dried in a 60 °C oven for 24 h to obtain a polymer film, denoted as LP.
[0055] Comparative Example 3 200 mg of polyvinylidene fluoride and 200 mg of lithium bis(trifluoromethanesulfonyl)imide were dispersed in 5 mL of N,N-dimethylformamide and stirred thoroughly for 24 h. Then, the mixture was coated onto the surface of a glass plate with a 500 μm thick doctor blade and dried in a 60 °C oven for 24 h to obtain a polymer film, denoted as PVDF.
[0056] The microstructure of the polymer films prepared in the embodiments and comparative examples of this application was characterized as follows: The surface of the bacterial cellulose and intermediate products from Example 1 was analyzed by scanning electron microscopy, and the results are as follows: Figure 1 As shown. Among them, Figure 1 Figure a shows the SEM image of bacterial cellulose, and Figure b shows the SEM image of the intermediate product.
[0057] from Figure 1 It can be seen that bacterial cellulose maintains a good one-dimensional linear morphology. After grafting with polymer side chains, bacterial cellulose becomes significantly thicker, indicating that the side chains were successfully grafted.
[0058] Physical images of the polymer film BPALP from Example 1, the polymer films BLP, LP, and PVDF from Comparative Examples 1-3 are shown in Figure 2. Surface scanning electron microscopy (SEM) tests were performed on each film, and the results are as follows: Figure 3 As shown.
[0059] Figure 2 Figure a represents PVDF, figure b represents LP, figure c represents BLP, and figure d represents BPALP. Figure 2 It can be seen that the thickness of the polymer film is in the range of 17-20 μm.
[0060] Figure 3 Figure a represents PVDF, figure b represents LP, figure c represents BLP, and figure d represents BPALP. Figure 3 It can be seen that the pure PVDF polymer membrane has obvious phase separation pores. The phase separation of LP and BLP polymer membranes is alleviated, but particle aggregation occurs. The BPALP polymer membrane exhibits a smoother and denser morphology, indicating that the compatibility of bacterial cellulose and LLZTO filler with PVDF is improved.
[0061] Stress-strain tests were performed on polymer films BPALP, BLP, LP, and PVDF, and the results are as follows: Figure 4 As shown.
[0062] from Figure 4 The tensile strengths of the four polymer films were found to be 12.5 MPa, 17.4 MPa, 17.5 MPa, and 18.6 MPa, respectively. The test results indicate that the addition of both bacterial cellulose and LLZTO rigid fillers significantly improved the tensile strength of the polymer films. The BPALP polymer film of Example 1 exhibited extremely high elongation at break, which is attributed to the formation of lithium p-styrene sulfonate at the bacterial cellulose and LLZTO interface, which promotes stress transfer, thereby achieving a simultaneous increase in tensile strength and elongation at break.
[0063] The polymer films from Example 1 and Comparative Examples 1-3 were used to assemble lithium batteries, and their electrochemical performance was evaluated.
[0064] When assembling the battery, the above polymer film is cut into films with a diameter of 1.8 cm and 5 μL of a mixed solvent of ethylene carbonate / fluoroethylene carbonate (volume ratio 3:1) is added to form a solid polymer electrolyte membrane, which is denoted as BPALP / P, BLP / P, LP / P and PVDF / P respectively.
[0065] Young's modulus tests were performed on the above-mentioned solid polymer electrolyte membranes BPALP / P, BLP / P, LP / P, and PVDF / P. The atomic force microscopy Young's modulus distribution diagrams are shown below. Figure 5 As shown. Among them, Figure 5 Figure a shows the PVDF / P ( Figure 5 Figures a) and b) represent LP / P, figure c) represents BLP / P, and figure d) represents BPALP / P.
[0066] from Figure 5 It is known that the Young's modulus of the BPALP / P solid electrolyte membrane can reach 1.5 GPa, while the Young's moduli of the LP / P and BLP / P electrolyte membranes are 0.50 and 0.72 GPa, respectively, and the Young's modulus of the pure PVDF / P electrolyte membrane is only 0.48 GPa. Test data indicate that both rigid bacterial cellulose and LLZTO ceramic fillers contribute to improving the Young's modulus of the electrolyte membrane, thus inhibiting dendrite growth during charge and discharge.
[0067] Impedance and ionic conductivity tests were performed on the above-mentioned solid polymer electrolyte membranes BPALP / P, BLP / P, LP / P, and PVDF / P. The results are as follows: Figure 6 As shown. Among them, Figure 6 Figures a to d are impedance spectra, and figure e is the ionic conductivity-temperature curve.
[0068] from Figure 6 It can be seen that the BPALP electrolyte exhibits the highest room temperature ionic conductivity, reaching 1.2 × 10⁻⁶. -3 S cm -1 This is mainly due to the synergistic effect between LLZTO and the lithium p-polystyrene sulfonate side chains, which enables rapid interfacial ion transport behavior. As a result, the ion transport activation energy of the BPALP electrolyte membrane is also significantly reduced.
[0069] The above-mentioned solid polymer electrolyte membrane was used to assemble an asymmetric battery with lithium-ion / steel sheets, and a linear sweep voltammetry test was performed, as follows: In an argon-atmospheric glove box, lithium-ion / steel-ion asymmetric batteries were assembled in the following order: negative electrode shell, spring contact, stainless steel gasket, lithium sheet, solid polymer electrolyte membrane, stainless steel gasket, and positive electrode shell. The lithium sheet had a diameter of 15.6 mm and a thickness of 0.45 mm; the stainless steel gasket had a diameter of 15.6 mm and a thickness of 1.0 mm; and the water and oxygen content in the glove box was below 0.1 ppm. Lithium-ion / steel-ion asymmetric batteries were then assembled using the aforementioned solid polymer electrolyte membranes BPALP / P, BLP / P, LP / P, and PVDF / P, respectively.
[0070] Using a CHI760E electrochemical workstation from Shanghai Chenhua Co., Ltd., linear sweep voltammetry (LSV) was performed at a scan rate of 5 mV / s. -1 The voltage range is 0~6.0 V. The resulting LSV curve is as follows. Figure 7 As shown.
[0071] from Figure 7 It can be seen that the electrochemical window of LP / P and BLP / P solid polymer electrolyte membranes is lower than that of pure PVDF / P electrolyte. This is mainly because the presence of the alkaline passivation layer on the LLZTO surface induces PVDF to de-HF and form -C=C- double bonds, which will damage the high-voltage stability of the electrolyte membrane. Conversely, the BPALP / P electrolyte exhibits the highest electrochemical window, indicating that the lithium carbonate passivation layer on the LLZTO surface has been successfully transformed into lithium-ion active lithium p-styrene sulfonate. The lithium deposition / stripping performance of the solid polymer electrolyte membrane assembled with the above-mentioned lithium wafer / lithium wafer symmetric battery is tested. The specific steps are as follows: In an argon-atmospheric glove box, Li|Li symmetric batteries were assembled in the following order: negative electrode shell, spring sheet, stainless steel gasket, lithium sheet, solid polymer electrolyte membrane, lithium sheet, and positive electrode shell. The stainless steel gasket had a diameter of 15.6 mm and a thickness of 1.5 mm, and the lithium sheet had a thickness of 0.45 mm. The water and oxygen content in the glove box was both below 0.1 ppm. Lithium|Li symmetric batteries were then assembled using the aforementioned solid polymer electrolyte membranes BPALP / P, BLP / P, LP / P, and PVDF / P, respectively.
[0072] Figure 8 Critical current density test results for Li|Li symmetric cells assembled with PVDF / P, LP / P, BLP / P, and BPALP / P solid electrolyte membranes. Figure 8 It can be seen that the BPALP tough and high-conductivity solid electrolyte membrane exhibits the highest critical current density, indicating that thanks to the mechanical support of the two rigid fillers and the synergistic effect of the lithium styrene sulfonate groups on homogenizing lithium ion flow, lithium dendrites can be effectively suppressed and uniform lithium metal deposition can be promoted.
[0073] Figure 9For PVDF / P, LP / P, BLP / P, and BPALP / P solid electrolyte membranes at 0.1 mA cm⁻¹ -2 Current density and 0.1 mAh cm⁻¹ -2 Cycling performance of Li|Li symmetric cells at areal capacity. The Li|Li symmetric cell assembled based on the BPALP / P electrolyte membrane can cycle stably for over 1000 h, exhibiting low and stable overpotentials and demonstrating stable and reversible lithium deposition / stripping behavior. In contrast, Li|Li symmetric cells assembled based on PVDF / P, LP / P, and BLP / P electrolyte membranes exhibit higher and more unstable overpotentials during lithium deposition / cycling, and all experience short circuits within a short time, indicating uncontrolled lithium dendrite growth within the cells.
[0074] The electrochemical performance of the full cell assembled with the above-mentioned solid polymer electrolyte membrane was tested using the following method: In an argon-atmospheric glove box, a full cell was assembled in the following order: negative electrode shell, spring sheet, stainless steel gasket, lithium sheet, solid polymer electrolyte membrane, positive electrode sheet, and positive electrode shell. The stainless steel gasket had a diameter of 15.6 mm and a thickness of 1.5 mm, the lithium sheet had a diameter of 15.6 mm and a thickness of 0.45 mm, and the areal density of the positive electrode sheet was 1-2 mg / cm³. -2 The diameter was 12 mm, and the water and oxygen content in the glove box was less than 0.1 ppm. Full cells were assembled using the above-mentioned solid polymer electrolyte membranes BPALP / P, BLP / P, LP / P, and PVDF / P, respectively.
[0075] Figure 10 Cycling performance of NCM811 full cells assembled with PVDF / P, LP / P, BLP / P, and BPALP / P solid electrolyte membranes at current densities of 1.0 C and 2.0 C.
[0076] from Figure 10 It can be seen that, at a current density of 1 C, the Li|BPALP / P|NCM811 battery assembled with the solid polymer electrolyte membrane BPALP / P of Example 1 can achieve 179.4 mAh g⁻¹. -1The high initial discharge specific capacity of the Li|BPALP / P|NCM811 battery exhibited by Example 1 remained at 70.7% capacity after 900 cycles. In contrast, the NCM811 full cells assembled with PVDF / P, LP / P, and BLP / P electrolyte membranes in the comparative examples all experienced severe capacity decay within a short period. Furthermore, at a higher current density of 2C, the Li|BPALP / P|NCM811 battery assembled with the solid electrolyte membrane in Example 1 could stably cycle for 600 cycles with a capacity retention of 78.4%; while the Li||NCM811 full cells assembled with the other three electrolytes all experienced internal short circuits within 300 cycles. This is mainly due to the synergistic effect of the dual fillers, which promotes rapid ion transport at the interface and alleviates the polarization process caused by limited ion transport at the interface.
[0077] Figure 11 The cycling performance of a full cell assembled using the BPALP / P solid polymer electrolyte membrane of Example 1, Li|BPALP / P|NCM811, at -20 °C and 100 °C. From... Figure 11 It can be seen that it can still maintain stable cycling at -20 ℃, and the discharge specific capacity can reach 137 mAh g. -1 The capacity retention rate was still 100% after 40 cycles. At 100 °C, it could still maintain reversible cycling for more than 40 cycles at a current density of 0.2 C, indicating that the BPALP / P electrolyte of Example 1 has the potential for application under extreme conditions.
[0078] Although this application has been described in detail in this specification with general descriptions and specific embodiments, some modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, such modifications or improvements made without departing from the spirit of this application are all within the scope of protection claimed in this application.
Claims
1. A method for preparing an ultrathin, strong, and highly conductive solid polymer electrolyte membrane, characterized in that, Includes the following steps: S1, bacterial cellulose is reacted with 2-bromoisobutyryl bromide via esterification to obtain bromine-modified bacterial cellulose; S2, the bromine-modified bacterial cellulose and a polymer monomer containing sulfonic acid groups are polymerized to graft polymer side chains onto its surface to obtain a one-dimensional polymer brush; S3, the one-dimensional polymer brush and lithium lanthanum zirconium tantalum oxide are dispersed in a first organic solvent to obtain a filler dispersion; the filler dispersion, lithium salt and PVDF are dispersed in the first organic solvent, mixed evenly, coated onto the substrate surface, and dried to obtain an ultrathin, strong and tough high-conductivity solid polymer electrolyte membrane.
2. The preparation method according to claim 1, characterized in that, Step S1 is as follows: Bacterial cellulose was dispersed in N,N-dimethylformamide, and 4-dimethylaminopyridine and triethylamine were added and mixed thoroughly. 2-Bromoisobutyryl bromide was added dropwise to the above mixture at 0 ℃ under an inert atmosphere. The mixture was heated to 30 ℃ and stirred for 24 h. The reaction was quenched with ethanol. The solid product was collected, washed, and dried to obtain bromine-modified bacterial cellulose.
3. The preparation method according to claim 2, characterized in that, The mass-to-volume ratio of bacterial cellulose to N,N-dimethylformamide is 1~5 mg / mL; The mass ratio of bacterial cellulose to 4-dimethylaminopyridine is 1:1~3; The mass-to-volume ratio of bacterial cellulose to triethylamine and 2-bromoisobutyryl bromide was 1 mg: 20-50 μL: 20-40 μL.
4. The preparation method according to claim 1, characterized in that, Step S2 is as follows: Bromine-modified bacterial cellulose was dispersed in a second organic solvent, and a polymer monomer containing sulfonic acid groups, tris(2-pyridylmethyl)amine, copper bromide, and vitamin C were added. The mixture was heated to 60-70 °C and reacted under an inert atmosphere. The solid product was collected, washed, and the intermediate product was obtained. The intermediate product was dispersed in deionized water, a strong acid solution was added, and the mixture was stirred to react, converting the polymer salt containing sulfonic acid groups into a polymer containing sulfonic acid groups. The solid phase was collected, washed, and a one-dimensional polymer brush was obtained.
5. The preparation method according to claim 4, characterized in that, The polymeric monomer containing sulfonic acid groups includes at least one of sodium p-styrene sulfonate, potassium 3-sulfopropyl methacrylate, or 2-acrylamide-2-methylpropanesulfonic acid. The strong acid solution is nitric acid or hydrochloric acid; The second organic solvent includes at least one of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, or tetrahydrofuran; And / or, The mass ratio of the brominated bacterial cellulose, the polymer monomer containing sulfonic acid groups, tris(2-pyridylmethyl)amine, copper bromide, and vitamin C is 1:20~60:0.5~0.9:0.05~0.1:0.2~0.35; The mass-to-volume ratio of bromine-modified bacterial cellulose to the second organic solvent is 1 mg: 0.5~1.5 mL.
6. The preparation method according to claim 1, characterized in that, The lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, or lithium difluorooxalateborate. The first organic solvent is N,N-dimethylformamide; And / or, The concentration of the one-dimensional polymer brush in the filler dispersion is 50~60 mg / mL; The mass ratio of the one-dimensional polymer brush to lithium lanthanum zirconium tantalum oxide is 0.25~0.5:1; The mass ratio of one-dimensional polymer brush to polyvinylidene fluoride is 1:3~4; The mass ratio of polyvinylidene fluoride to lithium salt is 1~2:1; The mass-to-volume ratio of polyvinylidene fluoride to N,N-dimethylformamide is 1 mg / 1.5~3 mL; And / or, The thickness of the ultrathin, strong, and highly conductive solid polymer electrolyte membrane is 15~20 μm.
7. The ultrathin, strong, and highly conductive solid polymer electrolyte membrane prepared by the preparation method according to any one of claims 1-6.
8. The application of the ultrathin, strong, and highly conductive solid polymer electrolyte membrane according to claim 7 in lithium batteries.
9. The application according to claim 8, characterized in that, During the assembly of lithium batteries, a plasticizer is dropped into the ultra-thin, strong, and highly conductive solid polymer electrolyte membrane; The plasticizer includes at least one of ethylene carbonate, fluoroethylene carbonate, methyl trifluoroethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene ethylene carbonate, or ethylene carbonate. The dosage of plasticizer is 0.1~0.5 μL / cm³. 2 .
10. A solid-state lithium battery, characterized in that, It includes a positive electrode, a negative electrode, and a solid electrolyte; The positive electrode is any one of lithium iron phosphate, lithium nickel cobalt manganese oxide, or lithium cobalt oxide. The negative electrode is any one of lithium metal, graphite, or silicon-carbon. The solid electrolyte is the ultrathin, strong, and highly conductive solid polymer electrolyte membrane as described in claim 7.