A c9h7f3o3 modified llzto-based peo composite solid-state electrolyte and a preparation method thereof
By introducing C9H7F3O3 as a modifier into PEO-based solid electrolytes, the interfacial stability and lithium-ion transport are enhanced, the lithium dendrite piercing problem is solved, and high stability and long lifespan solid electrolyte performance are achieved.
Patent Information
- Application Number
- CN202610442497.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-07
- Publication Date
- 2026-07-24
Smart Images
Figure CN122455906A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery technology, and relates to solid electrolyte modification technology. Specifically, it provides a C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte and its preparation method. Background Technology
[0002] With economic development and increasing energy demand, non-renewable energy sources are being continuously depleted, leading to various pollution problems that constantly impact the ecological environment. Therefore, developing environmentally friendly new energy sources is urgently needed. Rechargeable lithium-ion batteries, due to their high volumetric energy, high energy density, and long cycle life, have become a key alternative to fossil fuels and traditional energy sources, and are widely used in various portable electronic devices, electric vehicles, and large-scale energy storage systems. Currently, most commercial lithium-ion batteries (LIBs) use organic liquid electrolytes, which pose risks of combustion, explosion, and leakage. Compared to organic liquid electrolytes, solid-state electrolytes (SPEs) offer higher safety, a wider electrochemical window, a higher operating temperature range, and better suppression of lithium dendrite growth. Furthermore, solid-state electrolytes also boast higher energy densities than the highest energy density currently available in commercial liquid lithium-ion batteries.
[0003] Polyethylene oxide (PEO)-based polymer solid electrolytes have been extensively studied over the past few decades due to their excellent flexibility, good lithium salt dissociation ability, excellent interfacial contact with electrodes (especially lithium metal anodes), and low cost. The ether oxygen bond (-COC-) in the PEO backbone can react with lithium ions (Li... + Coordination occurs, and Li is realized through local movement of chain segments. + PEO-based solid electrolytes possess the intrinsic properties of solid-state ion conductors due to their ability to transport lithium ions. However, PEO-based solid electrolytes suffer from a fatal flaw: poor uniformity of lithium deposition during cycling, leading to uneven lithium accumulation and subsequent lithium dendrite penetration, causing internal short circuits in the battery. Therefore, this invention provides a C9H7F3O3-modified LLZTO-based PEO composite solid electrolyte, which enhances the interfacial stability of the electrolyte with metallic lithium and optimizes the lithium-ion transport mechanism, thereby significantly improving the electrochemical performance of PEO-based solid electrolytes. Summary of the Invention
[0004] The purpose of this invention is to provide a C9H7F3O3-modified LLZTO-based PEO composite solid electrolyte and its preparation method, to solve the problem of lithium dendrite puncture during cycling in existing PEO-based solid electrolytes. This invention creatively introduces C9H7F3O3 (4-methoxy-2-trifluoromethylbenzoic acid) as a modifier, which can effectively enhance the interfacial stability of the electrolyte with metallic lithium, while optimizing the lithium-ion transport mechanism, thereby improving the cycle life and electrochemical performance of the PEO-based solid electrolyte.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0006] A C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte, characterized in that it comprises: PEO (polyethylene oxide), LLZTO (lithium lanthanum zirconium tantalum oxide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), and C9H7F3O3 (4-methoxy-2-trifluoromethylbenzoic acid), wherein the mass ratio of C9H7F3O3 to LLZTO is (3~11):12.5.
[0007] Furthermore, the total mass of PEO, LLZTO and LiTFSI is used as the reference mass, with LiTFSI accounting for 15 wt% to 35 wt% of the reference mass.
[0008] Furthermore, the molar ratio of ether oxygen atom (EO) in PEO to LiTFSI is (8~20):1.
[0009] Meanwhile, this invention provides a method for preparing the above-mentioned C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte, characterized by comprising the following steps:
[0010] Step 1. Using acetonitrile as a solvent, C9H7F3O3 is added to acetonitrile and allowed to dissolve completely. Then LLZTO is added and stirred at room temperature to obtain mixed slurry A. Mixed slurry A is then dried to obtain modified LLZTO powder.
[0011] Step 2. Weigh the modified LLZTO powder, LiTFSI and PEO in proportion and add them to the acetonitrile solution. Stir at room temperature to obtain mixed slurry B.
[0012] Step 3. Pour the mixed slurry B into a polytetrafluoroethylene mold, and after vacuum drying, obtain the C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte.
[0013] After being thoroughly dried in a vacuum drying oven at 60℃, a modified LLZTO-based PEO composite solid electrolyte was obtained.
[0014] Furthermore, in step 1, the mass ratio of C9H7F3O3 to LLZTO is (3~11): 12.5.
[0015] Furthermore, in step 1, the drying process of mixed slurry A is as follows: mixed slurry A is poured into an evaporating dish and dried in a drying oven at 60~90℃.
[0016] Furthermore, in step 2, the molar ratio of ether oxygen atoms of PEO to LiTFSI is (8~20):1, with the total mass of PEO, LLZTO and LiTFSI as the reference mass, and LiTFSI accounting for 15 wt%~35 wt% of the reference mass.
[0017] Furthermore, in steps 1 and 2, the stirring time at room temperature is 10~24h.
[0018] Furthermore, step 2 also includes defoaming treatment, specifically: placing the mixed slurry B in a vacuum chamber and performing multiple vacuuming processes to eliminate air bubbles present in the mixed slurry B.
[0019] Furthermore, in step 3, the vacuum drying temperature is 60~80℃, and the time is 6~24h.
[0020] Based on the above technical solution, the beneficial effects of the present invention are as follows:
[0021] This invention, based on the LLZTO-based PEO composite solid-state electrolyte system, for the first time applies C9H7F3O3 as a modifier in the field of solid-state electrolytes. C9H7F3O3, LLZTO, LiTFSI, and PEO are thoroughly mixed and then dried to form a film, producing a composite solid-state electrolyte. This electrolyte effectively improves the interfacial stability between the PEO-based solid-state electrolyte and the lithium metal anode, and optimizes the lithium-ion transport mechanism, thereby significantly extending the cycle life of lithium-symmetric batteries. Its specific mechanism is as follows: On the one hand, C9H7F3O3 possesses a unique bifunctional structure, such as... Figure 1 As shown, the carboxyl group (-COOH) can undergo an acid-base neutralization reaction with high-resistivity impurities (such as lithium carbonate and lithium hydroxide, mainly lithium carbonate) on the LLZTO surface, such as... Figure 2As shown, this reaction not only effectively eliminates the severe passivation of the LLZTO surface by high-impedance impurities and significantly reduces the interfacial resistance, but also restores the lithium-ion transport activity of the interface. On the other hand, the trifluoromethyl (-CF3) group in the molecule, due to the high electronegativity of fluoride ions, endows the trifluoromethyl group with many unique properties. With its unique "weak solvation" effect and strong electron-withdrawing ability, it can effectively regulate the local lithium-ion solvation structure, reduce the lithium-ion desolventization energy barrier, reduce the diffusion resistance of lithium ions, thereby accelerating the ion migration rate, significantly improving the kinetic performance of lithium ions, and achieving optimization and rapid transport of lithium ions. At the same time, the trifluoro group is very stable, which also helps to induce the construction of a stable solid electrolyte interphase (SEI) film rich in LiF. The stable SEI film synergistically inhibits the growth of lithium dendrites. The effective inhibition of lithium dendrite growth further comprehensively improves the electrochemical stability and cycle life of the composite solid electrolyte.
[0022] In summary, this invention provides a C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte and its preparation method, which has the following advantages:
[0023] 1. The modified LLZTO-based PEO composite solid electrolyte provided by this invention exhibits good stability to lithium metal, specifically demonstrated by the assembled lithium symmetric battery maintaining a stability of 0.2 mA·cm⁻¹ at an operating temperature of 60°C. -2 At current density, it can operate stably for more than 2000 hours, demonstrating excellent lithium deposition / stripping cycle performance;
[0024] 2. The modified LLZTO-based PEO composite solid electrolyte provided by this invention exhibits excellent full-cell cycle stability. Specifically, in a battery system with lithium iron phosphate as the positive electrode and unmodified lithium metal as the negative electrode, after 300 cycles at 60°C, the capacity retention rate is still as high as 93.7%; the cycle life with an expected capacity retention rate of 80% exceeds 2000 cycles.
[0025] 3. The modified LLZTO-based PEO composite solid electrolyte preparation process provided by this invention is simple. Compared with other common modification methods, it can be achieved simply by stirring at room temperature. In addition, the solvent used is acetonitrile, which can effectively avoid the problem of other solvent residues. Attached Figure Description
[0026] Figure 1 This is a schematic diagram of the molecular structure of the modifier C9H7F3O3 (4-methoxy-2-trifluoromethylbenzoic acid) in this invention.
[0027] Figure 2 This is the chemical reaction equation between the modifier C9H7F3O3 and Li2CO3 in this invention.
[0028] Figure 3 The XRD patterns of LLZTO powder in Example 1 and Comparative Example 1 of this invention are shown.
[0029] Figure 4 The cycling performance curves of the lithium symmetric batteries in Examples 1-6 and Comparative Example 1 of this invention are shown.
[0030] Figure 5 The figures show the cycle performance curves of the lithium metal full battery in Example 1 and Comparative Example 1 of this invention.
[0031] Figure 6 This is a charge-discharge curve of the lithium metal full battery in Embodiment 1 of the present invention. Detailed Implementation
[0032] To make the objectives, technical solutions, and technical effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.
[0033] Example 1
[0034] This embodiment provides a C9H7F3O3-modified LLZTO-based PEO composite solid electrolyte, comprising: PEO (polyethylene oxide), LLZTO (lithium lanthanum zirconium tantalum oxide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), and C9H7F3O3 (4-methoxy-2-trifluoromethylbenzoic acid). The mass ratio of C9H7F3O3 to LLZTO is 7:12.5, and LiTFSI accounts for 15 wt% of the reference mass (total mass of PEO, LLZTO, and LiTFSI). The molar ratio of ether oxygen atoms (EO) of PEO to LiTFSI is 16:1. It should be noted that this embodiment uses PEO with a molecular weight of 600,000 as the polymer matrix. Based on this, lithium LiTFSI is added to the electrolyte system at a polyethylene oxide ether oxygen atom (EO) to LiTFSI molar ratio of 16:1. This ratio effectively balances the contradiction between ionic conductivity and the mechanical flexibility of the polymer matrix.
[0035] The C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte is prepared by the following steps:
[0036] Step 1: Weigh the raw materials using an electronic balance with an accuracy of 0.07 g of C9H7F3O3 and add it to 3 ml of acetonitrile. Stir thoroughly at room temperature until completely dissolved. Then weigh 0.125 g of LLZTO and add it to the above solution. Stir thoroughly at room temperature for 24 h to obtain mixed slurry A. Pour mixed slurry A into an evaporating dish and dry it thoroughly in a drying oven at 80 °C to obtain modified LLZTO powder.
[0037] Step 2: Add the modified LLZTO powder, 0.5g of PEO, and 0.204g of LiTFSI (EO: LiTFSI = 16:1) to 12ml of acetonitrile and stir magnetically at 800rpm for 24h to obtain white electrolyte slurry B.
[0038] Step 3: Before casting, pour the above electrolyte slurry into the polytetrafluoroethylene plate mold, place it in the vacuum chamber and evacuate twice to remove air bubbles in the electrolyte film, so as to avoid residual air bubbles causing pores after subsequent drying and film formation.
[0039] Step 4: After drying the above electrolyte slurry in a vacuum drying oven at 60°C for 12 hours to form a film, transfer it to a glove box filled with argon atmosphere (H2O < 0.1 ppm, O2 < 0.1 ppm) and let it stand for 6 hours to obtain the modified LLZTO-based PEO-based solid electrolyte membrane.
[0040] Based on the modified LLZTO-based and PEO-based solid electrolyte membranes described above, lithium metal symmetric cells and full cells were assembled and tested respectively.
[0041] The assembly process of lithium metal symmetric battery is as follows: the fully cooled solid electrolyte membrane is cut into uniform circular pieces with a diameter of 16mm and a thickness of about 100µm. Then, the lithium metal symmetric battery is assembled in the following order: positive electrode shell - lithium metal - modified LLZTO-based PEO solid electrolyte membrane - lithium metal - stainless steel sheet - spring sheet - negative electrode shell.
[0042] The assembly process of lithium metal full battery is as follows: using lithium iron phosphate positive electrode sheets with a diameter of 9mm and an active material of 0.80mg, the lithium metal full battery is assembled in the following order: positive electrode shell - positive electrode sheet - modified LLZTO-based PEO composite solid electrolyte membrane - lithium sheet - spring sheet - negative electrode shell.
[0043] Example 2
[0044] This embodiment also provides a C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte, which differs from Example 1 in that the mass ratio of C9H7F3O3 to LLZTO is 3:12.5, corresponding to 0.03g of C9H7F3O3 in step 1.
[0045] Example 3
[0046] This embodiment also provides a C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte, the difference from Example 1 is that the mass ratio of C9H7F3O3 to LLZTO is 5:12.5, corresponding to 0.05g of C9H7F3O3 in step 1.
[0047] Example 4
[0048] This embodiment also provides a C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte, the difference from Example 1 is that the mass ratio of C9H7F3O3 to LLZTO is 9:12.5, corresponding to 0.09g of C9H7F3O3 in step 1.
[0049] Example 5
[0050] This embodiment also provides a C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte, which differs from Example 1 in that the mass ratio of C9H7F3O3 to LLZTO is 11:12.5, corresponding to 0.11g of C9H7F3O3 in step 1.
[0051] The beneficial effects of the present invention will be described in detail below with reference to the test results. In order to more intuitively demonstrate the advantages of the present invention, a comparative example is provided.
[0052] Comparative Example 1
[0053] An LLZTO-based PEO composite solid electrolyte is provided, which differs from Comparative Example 1 in that it only includes: PEO (polyethylene oxide), LLZTO (lithium lanthanum zirconium tantalum oxide), and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), and is assembled to form a lithium metal symmetric cell and a full cell for testing.
[0054] like Figure 3 The figure shows the XRD patterns of the modified LLZTO powder in Example 1 and the LLZTO powder in Comparative Example 1. As can be seen from the figure, the comparative example sample contains a relatively obvious lithium carbonate diffraction peak, while the example sample contains almost no lithium carbonate. This result shows that C9H7F3O3 effectively removes lithium carbonate from the surface of the original LLZTO, proving that the electrolyte modified by C9H7F3O3 has almost no passivation layer.
[0055] like Figure 4 The image shows lithium symmetric batteries assembled in Examples 1-5 and Comparative Example 1 of the present invention at 60°C and 0.2 mA·cm⁻¹. -2 As shown in the figure, the cycle performance curves under working conditions indicate that the cycle life of the lithium symmetric batteries assembled based on the C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte provided in Examples 1 to 5 is significantly improved. In particular, the lithium symmetric battery in Example 1 (with a mass ratio of C9H7F3O3 to LLZTO of 7:12.5) has a cycle life exceeding 2000h. Therefore, the surface modifier C9H7F3O3 can effectively improve the interfacial stability of the LLZTO-based PEO composite solid electrolyte with lithium.
[0056] like Figure 5 The figure shows the cycling performance curves of the lithium metal full cells assembled in Example 1 and Comparative Example 1 under 60°C and 1C rate conditions. As can be seen from the figure, the lithium metal full cell assembled based on the C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte provided in Example 1 still has a capacity retention rate of up to 93.7% after 300 cycles. Under the same conditions, the full cell based on the unmodified LLZTO-based PEO solid electrolyte in Comparative Example 1 has a capacity retention rate as low as 67.8% after 300 cycles.
[0057] like Figure 6 The figure shows the charge-discharge curves of the lithium metal full battery assembled in Example 1 of this invention at 60°C and 1C rate. As can be seen from the figure, based on the C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte provided in Example 1, the capacity of the assembled lithium metal full battery only decreased from 138.59 mAh g⁻¹ after 300 cycles. -1 Reduced to 129.88 mAh g -1 The capacity retention rate is as high as 93.7%.
[0058] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.
Claims
1. A C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte, characterized in that, include: PEO (polyethylene oxide), LLZTO (lithium lanthanum zirconium tantalum oxide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) and C9H7F3O3 (4-methoxy-2-trifluoromethylbenzoic acid), wherein the mass ratio of C9H7F3O3 to LLZTO is (3~11):12.
5.
2. The C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte according to claim 1, characterized in that, The total mass of PEO, LLZTO and LiTFSI is used as the reference mass, with LiTFSI accounting for 15 wt% to 35 wt% of the reference mass.
3. The C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte according to claim 1, characterized in that, The molar ratio of ether oxygen atom (EO) to LiTFSI in the PEO is (8~20):
1.
4. The preparation method of the C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte according to claim 1, characterized in that, Includes the following steps: Step 1. Using acetonitrile as a solvent, C9H7F3O3 is added to acetonitrile and allowed to dissolve completely. Then LLZTO is added and stirred at room temperature to obtain mixed slurry A. Mixed slurry A is then dried to obtain modified LLZTO powder. Step 2. Weigh the modified LLZTO powder, LiTFSI and PEO in proportion and add them to the acetonitrile solution. Stir at room temperature to obtain mixed slurry B. Step 3. Pour the mixed slurry B into a polytetrafluoroethylene mold, and after vacuum drying, obtain the C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte. After being thoroughly dried in a vacuum drying oven at 60°C, a modified LLZTO-based PEO composite solid electrolyte was obtained.
5. The preparation method of the C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte according to claim 4, characterized in that, In step 1, the mass ratio of C9H7F3O3 to LLZTO is (3~11): 12.
5.
6. The preparation method of the C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte according to claim 4, characterized in that, In step 1, the drying process of mixed slurry A is as follows: Mixed slurry A is poured into an evaporating dish and dried in a drying oven at 60~90℃.
7. The preparation method of the C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte according to claim 4, characterized in that, In step 2, the molar ratio of ether oxygen atoms of PEO to LiTFSI is (8~20):
1. The total mass of PEO, LLZTO and LiTFSI is used as the reference mass, and LiTFSI accounts for 15 wt%~35 wt% of the reference mass.
8. The preparation method of the C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte according to claim 4, characterized in that, In steps 1 and 2, the stirring time at room temperature is 10~24h.
9. The preparation method of the C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte according to claim 4, characterized in that, Step 2 also includes defoaming treatment, specifically: placing the mixed slurry B in a vacuum chamber and performing multiple vacuuming processes to eliminate air bubbles present in the mixed slurry B.
10. The preparation method of the C9H7F3O3 modified LLZTO-based PEO composite solid electrolyte according to claim 4, characterized in that, In step 3, the vacuum drying temperature is 60~80℃ and the time is 6~24h.