High-performance composite solid electrolyte and preparation method thereof
By adding rare earth element-doped cerium oxide nanofillers to the PVDF matrix, the shortcomings of traditional composite electrolytes in terms of ion transport, mechanical strength and interfacial reaction are solved, and a high-performance all-solid-state lithium metal battery is realized.
Patent Information
- Application Number
- CN202511210913.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-27
- Publication Date
- 2025-11-21
AI Technical Summary
Traditional PVDF-based composite electrolytes struggle to balance ion transport and mechanical strength, and uncontrollable interfacial side reactions lead to insufficient safety and energy density in lithium batteries.
Rare earth element-doped cerium oxide nanofiller is used as an additive in composite solid electrolyte. The adsorption of anions by oxygen vacancies on its surface promotes the dissociation of lithium salt, constructs a fast lithium-ion transport channel, and improves the stability of the electrolyte-electrode interface.
Significantly reduces battery impedance, improves cycle life and rate performance, and achieves a high-safety and high-energy-density all-solid-state lithium metal battery.
Smart Images
Figure CN120999110A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to lithium-ion battery material technology, specifically to a composite solid electrolyte with polyvinylidene fluoride as the matrix and rare earth element-doped cerium oxide nanofiller, which is suitable for all-solid-state lithium metal batteries with high safety and high energy density. Background Technology
[0002] Traditional liquid lithium batteries pose safety hazards due to the flammability of organic electrolytes. Solid-state lithium batteries, with their high safety and energy density, have become a research hotspot for next-generation energy storage devices. However, polymer solid electrolytes (such as polyvinylidene fluoride, PVDF) face core challenges, including low room-temperature ionic conductivity (typically less than 10⁻⁵ S / cm), high interfacial impedance, and insufficient mechanical strength. While PVDF possesses good electrochemical stability, its high crystallinity restricts polymer chain movement, hindering lithium-ion transport. Furthermore, the rigid interface easily induces lithium dendrite penetration, leading to battery short-circuit failure.
[0003] Currently, PVDF-based composite electrolytes mainly improve their performance by introducing inorganic fillers (such as LLZTO, LATP, etc.) or plasticizers (such as succinic acid), but two major contradictions still exist: (1) Trade-off between ion transport and mechanical strength: Although plasticizers can reduce the crystallinity of PVDF and increase ionic conductivity, they significantly weaken mechanical strength (tensile strength less than 5 MPa) and cannot suppress lithium dendrite penetration; while inorganic fillers (such as LLZTO) can enhance mechanical properties, but high loading (greater than 30 wt%) leads to deterioration of interfacial contact, and ionic conductivity drops to the order of 10-6 S / cm. (2) Uncontrollable interfacial side reactions: La atoms on the surface of garnet-type fillers (such as LLZO) undergo defluorination reaction with PVDF to generate unsaturated carbon chains, which trigger continuous degradation, resulting in a surge in interfacial impedance (greater than 1000 Ω·cm2) and a narrowing of the electrochemical window (less than 4.0 V); sulfide fillers have the risk of gas generation, which reduces cycle stability.
[0004] Rare-earth element-doped cerium oxide is an ideal filler due to its unique oxygen vacancy effect. Therefore, this paper uses polyvinylidene fluoride (PVDF) as a matrix and adds rare-earth element-doped cerium oxide nanofillers to prepare a composite solid electrolyte. The oxygen vacancies on the surface of rare-earth element-doped cerium oxide can adsorb anions (such as TFSI⁻), promote lithium salt dissociation, and improve the overall performance of the battery. Summary of the Invention
[0005] To address the aforementioned problems, this invention provides a high-performance composite solid electrolyte and its preparation method. Using polyvinylidene fluoride (PVDF) as the polymer matrix, rare-earth element-doped cerium oxide nanofiller is added. The oxygen vacancies on the surface of the rare-earth element-doped cerium oxide nanofiller adsorb anions (such as bis(trifluoromethanesulfonyl)imide, TFSI⁻) through Lewis acid-base interactions, promoting lithium salt dissociation and releasing free Li⁺. Simultaneously, a rapid lithium-ion transport channel is constructed within the PVDF matrix, enhancing the stability of the electrolyte-electrode interface, resulting in a battery with low impedance, good cycle life, and excellent rate performance.
[0006] A method for preparing a high-performance composite solid electrolyte, characterized in that the method includes the following steps: Step (1): Dissolve polyvinylidene fluoride in an organic solvent and stir until completely dissolved to obtain a polymer solution; Step (2): The rare earth element-doped cerium oxide nanofiller is dispersed in an organic solvent and ultrasonically treated to obtain a uniform and stable filler suspension. Step (3): Add the filler suspension described in step (2) to the polymer solution obtained in step (1) and stir and mix at room temperature to obtain a uniformly dispersed mixed solution; Step (4): Transfer the mixed solution obtained in step (3) to a glove box, add lithium salt, and stir until completely dissolved to obtain a uniformly dispersed composite solution; Step (5): The composite solution described in step (4) is coated into a film, and the solvent is removed by vacuum drying to obtain the composite solid electrolyte.
[0007] The organic solvents mentioned in steps (1) and (2) are independently selected from one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, acetone, cyclohexanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, butyl butyrate, hexyl hexanoate, ethylene glycol methyl ether, and diisobutyl ketone.
[0008] Further, the rare earth element mentioned in step (2) includes one or more of gadolinium, samarium, yttrium, and lanthanum; the rare earth element-doped cerium oxide nanofiller is gadolinium-doped cerium oxide (GDC) nanofiller or samarium-doped cerium oxide (SDC) nanofiller.
[0009] Furthermore, the stirring time in steps (3) and (4) is 4 to 36 hours.
[0010] Furthermore, the thickness of the coating film in step (5) is 40~100 μm.
[0011] Furthermore, the vacuum drying temperature in step (5) is 60~80℃, and the drying time is 12~24 h.
[0012] Compared with the prior art, the beneficial technical effects of the present invention are: (1) The gadolinium-doped cerium oxide (GDC) nanofiller selected in the present invention has surface oxygen vacancies, which can promote the dissociation of lithium salt; (2) The composite solid electrolyte prepared after adding GDC nanofiller has good interface stability, which significantly improves the overall performance of lithium battery. Attached Figure Description
[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0014] Figure 1 The image shows the EIS impedance diagram of the composite solid electrolyte of this invention.
[0015] Figure 2 This is a comparison graph of the electrochemical window curves of Example 1 and Comparative Example 1.
[0016] Figure 3 The battery cycle curves of Example 1 and Comparative Example 1 are compared.
[0017] Figure 4 This is a comparison of the battery rate curves of Example 1 and Comparative Example 1. Detailed Implementation
[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0019] The composite solid electrolyte provided by this invention comprises the following weight composition: 60-95 parts of PVDF polymer, 5-40 parts of lithium salt, and GDC with the chemical formula Ce0.8Gd0.2O2, which accounts for 1-10% of the total mass of PVDF and lithium salt.
[0020] The following is a detailed illustration using specific examples, along with comparative examples: Example
[0021] The specific steps for preparing PVDF-modified GDC nanofiller composite solid electrolyte are as follows: (1) Dissolve 0.6 g PVDF in 8 ml NMP and stir until homogeneous to obtain homogeneous slurry a; (2) 0.01 g of GDC filler was weighed and distributed in an organic solvent, and then subjected to ultrasonic treatment to obtain a uniform and stable filler suspension b; (3) Add the suspension b from step (2) to the uniform slurry a from step (1), stir evenly, and obtain the mixed slurry c; (4) Transfer the slurry c obtained in step (3) to a glove box, weigh 0.4 g of lithium bis(trifluoromethanesulfonyl)imide and add it to the slurry c, stir for 24 h to obtain a uniformly dispersed composite slurry d; (5) The composite slurry d obtained in step (4) is coated onto copper foil by a scraping method and dried under vacuum at 60 °C for 24 h to remove the solvent, thereby obtaining a composite solid electrolyte; (6) Cut the electrolyte obtained in step (5) into 17 mm round pieces, equip them with coin cells, and perform corresponding tests.
[0022] Comparative Example 1 (1) Weigh 0.6g of PVDF and add it to 8ml of NMP, then stir to dissolve; (2) Weigh 0.4 g of lithium bis(trifluoromethanesulfonylimide) in a glove box and add it to the slurry obtained in step (1), and stir for 24 h; (3) The slurry from step (2) is coated onto the substrate and dried under vacuum at 60°C to obtain the PVDF polymer electrolyte; (4) Cut the electrolyte obtained in step (3) into 17 mm round pieces, equip them with coin cells, and perform corresponding tests.
[0023] Figure 1 This is the EIS impedance diagram of the composite solid electrolyte of the present invention. Compared with the PVDF polymer electrolyte, the impedance of the composite solid electrolyte of the present invention is significantly lower than that of the PVDF polymer electrolyte, indicating that it has good interfacial stability.
[0024] Figure 2 The image shows a comparison of the electrochemical window curves of Example 1 and Comparative Example 1. Compared with the PVDF polymer electrolyte, the electrochemical window of the composite electrolyte of the present invention is significantly better than that of the PVDF polymer electrolyte, indicating that its stability is superior.
[0025] Figure 3 Comparing the battery cycle curves of Example 1 and Comparative Example 1, it can be seen that the composite solid electrolyte of this invention has a first-cycle discharge specific capacity of 120 mAh / g and stronger cycle stability.
[0026] Figure 4The battery rate curves of Example 1 and Comparative Example 1 are compared. Compared with PVDF polymer electrolyte, the battery equipped with the composite solid electrolyte of the present invention achieves a capacity of 110 mAh / g at 1C, while the battery equipped with PVDF polymer electrolyte only achieves a capacity of 80 mAh / g at 1C. This shows that the composite solid electrolyte of the present invention has superior rate performance.
[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.
Claims
1. A high-performance composite solid electrolyte, characterized in that, It comprises: a polyvinylidene fluoride (PVDF) matrix, a lithium salt, and rare earth-doped cerium oxide nanofillers, wherein the mass of the rare earth-doped cerium oxide nanofillers accounts for 1 to 10% of the total mass of the polyvinylidene fluoride matrix and the lithium salt; the rare earth elements include one or more of gadolinium, samarium, yttrium, and lanthanum.
2. The composite solid electrolyte according to claim 1, characterized in that, The rare earth element-doped cerium oxide nanofiller is either gadolinium-doped cerium oxide (GDC) nanofiller or samarium-doped cerium oxide (SDC) nanofiller.
3. The composite solid electrolyte according to claim 1 or 2, characterized in that, The rare earth element-doped cerium oxide nanofiller is in the form of nanowires or nanoparticles.
4. The composite solid electrolyte according to claim 1 or 2, characterized in that, The lithium salt is selected from one or two of lithium bis(trifluoromethanesulfonyl)imide and lithium hexafluorophosphate; the mass ratio of the polyvinylidene fluoride body to the lithium salt is (60~95):(5~40).
5. A method for preparing the composite solid electrolyte according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Dissolve polyvinylidene fluoride and lithium salt in an organic solvent and stir until completely dissolved to obtain a polymer solution; (2) The rare earth element-doped cerium oxide filler is dispersed in an organic solvent and ultrasonically treated to obtain a uniform and stable filler suspension. (3) Add the filler suspension to the polymer solution obtained in step (1) and stir and mix at room temperature to obtain a uniformly dispersed mixed solution; (4) Transfer the mixed solution obtained in step (3) to a glove box, add lithium salt, and stir until completely dissolved to obtain a uniformly dispersed composite solution; (5) The composite solution described in step (4) is coated into a film, and the solvent is removed by vacuum drying to obtain the composite solid electrolyte.
6. The preparation method according to claim 5, characterized in that, The organic solvents mentioned in steps (1) and (2) are independently selected from one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, acetone, cyclohexanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, butyl butyrate, hexyl hexanoate, ethylene glycol methyl ether, and diisobutyl ketone.
7. The preparation method according to claim 5, characterized in that, The stirring time in steps (3) and (4) is 4 to 36 hours, and the vacuum drying temperature in step (5) is 60 to 80°C, and the drying time is 12 to 24 hours.
8. An all-solid-state lithium metal battery, comprising a positive electrode, a negative electrode, and an electrolyte layer, characterized in that, The electrolyte layer is the composite solid electrolyte according to any one of claims 1 to 4; using lithium metal as the negative electrode, after 50 cycles at a charge-discharge rate of 0.5C and room temperature, its capacity retention is greater than 95%, and its electrochemical window measured by linear sweep voltammetry is not less than 4.5 V (relative to Li). + / Li electrode).