PEO-CeF / C solid electrolyte, preparation method thereof and application of PEO-CeF / C solid electrolyte in lithium battery
By combining CeF/C fiber networks prepared by coaxial electrospinning with polyethylene oxide to form PEO-CeF/C solid electrolyte, the problems of low ionic conductivity and poor interfacial compatibility of PEO-based electrolytes at room temperature are solved, achieving efficient lithium-ion conduction and electrode interface stability, and extending the cycle life of lithium batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-19
- Publication Date
- 2026-04-10
AI Technical Summary
Existing PEO-based solid electrolytes have low ionic conductivity at room temperature and poor compatibility with the electrode interface, resulting in a shortened cycle life of lithium batteries. Traditional powder fillers tend to agglomerate in the PEO matrix, making it difficult to form a continuous ion transport path.
A CeF/C fiber network was prepared using coaxial electrospinning technology and combined with polyethylene oxide to form a PEO-CeF/C solid electrolyte. By controlling the spinning process and calcination parameters, the morphology of CeF3/C fibers was controllable and the dispersion uniformity was achieved, thus constructing a highly efficient lithium-ion conduction network and forming a stable LiF film at the electrode interface.
It improves the ionic conductivity and interface stability of solid-state batteries, extends the cycle life of lithium batteries, and achieves high-performance solid-state lithium batteries with long cycle life and good high-voltage resistance.
Smart Images
Figure CN121839905A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of solid-state battery energy storage, and particularly relates to a PEO-CeF / C solid electrolyte, its preparation method and its application in lithium batteries. Background Technology
[0002] Solid-state lithium batteries, by using solid electrolytes instead of traditional liquid electrolytes, fundamentally solve safety hazards such as leakage and explosion, and are compatible with high-energy-density electrode materials, making them widely recognized as the core development direction of next-generation energy storage technology. However, the long-cycle stability of solid-state batteries is limited by the performance bottleneck of solid electrolytes. Their ion conduction efficiency and electrode-electrolyte interface compatibility directly determine the battery's service life and industrialization feasibility.
[0003] Polyethylene oxide (PEO)-based solid electrolytes have attracted much attention in the field of solid-state batteries due to their good lithium salt solubility, flexibility, and process compatibility. However, the high crystallinity of PEO molecular chains at room temperature leads to a relatively low ionic conductivity (typically below 10). -6 S・cm -1 Meanwhile, PEO has poor compatibility with the electrode interface, easily leading to side reactions and the formation of a high-resistivity interface layer during cycling, resulting in a significant reduction in battery cycle life. To address these issues, researchers have mainly focused on strategies such as adding fillers, organic-inorganic composites, and controlling the lithium salt ratio. While these strategies can weaken the interaction between Li+ and coordinating solvent molecules, thereby enhancing lithium-ion mobility, they neglect the flexibility and mechanical properties of solid electrolytes. Rare earth fluorides, due to their high ion mobility, wide electrochemical stability window, and excellent interfacial compatibility, are considered highly promising electrolyte optimization fillers. However, traditional powder fillers tend to agglomerate in PEO matrices, making it difficult to form continuous ion transport pathways. One-dimensional nanofiber materials, with their high aspect ratio, large specific surface area, and continuous structural characteristics, exhibit unique advantages in constructing interconnected ion channels and enhancing the mechanical properties of the matrix. Coaxial electrospinning technology, as a high-end preparation method for precisely controlling the structure and morphology of one-dimensional materials, can achieve the ordered arrangement and size uniformity control of functional components, providing a new path for preparing high-performance inorganic fiber fillers. Summary of the Invention
[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a PEO-CeF / C solid electrolyte, its preparation method and its application in lithium batteries. When the PEO-CeF / C solid electrolyte of this application is used in lithium batteries, it improves ionic conductivity, enhances interface stability and improves the cycle life of solid lithium batteries.
[0005] To solve the technical problem of this invention, the technical solution adopted is as follows: A method for preparing a solid electrolyte, the process is as follows: 1) Dissolve polyacrylonitrile (PAN) in N,N-dimethylformamide (DMF) and stir for 4-6 hours to obtain a clear solution, which is designated as bottle a; then dissolve polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP) in N,N-dimethylformamide (DMF) and stir for 4-6 hours to obtain a clear solution, then add CeF3 powder and stir until homogeneous, which is designated as bottle b; 2) Transfer the solutions from bottles a and b in step 1) into two syringes. Place the syringe containing the solution into the inner core and outer shell of the coaxial needle. Position the coaxial needle 15-17 cm away from the stainless steel foil collector and set the parameters for electrospinning. 3) The spun fibers obtained in step 2) are dried at 50~70℃ for 5~8 hours, and then transferred to a muffle furnace for carbonization to form a fluoride spun fiber network CeF / C; 4) Dissolve the fluoride spinning from step 3) with polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide in acetonitrile, stir evenly, and then place it in a polytetrafluoroethylene mold to dry, finally forming a PEO-CeF / C solid electrolyte membrane.
[0006] Further, in step 1), the concentration of polyacrylonitrile in DMF in bottle a is 0.1~0.2 g / mL; the mass ratio of polyacrylonitrile, polyvinylpyrrolidone, and CeF3 powder in bottle b is (3~5):1:(1.5~2), and the concentration of polyacrylonitrile in DMF is 0.1~0.15 g / mL. The molecular weight of polyacrylonitrile in bottles a and b is 1 million~2 million.
[0007] Further, in step 2), the coaxial electrospinning high-voltage power supply is set to 15~25 kV, driving the syringe connected to the coaxial needle core at a speed of 0.05~0.1 mm / min. -1 The speed of the syringe connected to the coaxial needle housing is 0.05~0.15 mm / min. -1 Electrospinning is performed at a speed of [speed].
[0008] Specifically, the coaxial electrospinning high-voltage power supply is set to 20 kV, driving two syringes at a speed of 0.075 mm / min. -1 (Internal) and 0.1 mm min -1 Electrospinning is performed at an external speed.
[0009] Further, in step 3), calcination carbonization refers to first heating to 180-220℃ at a heating rate of 1-3℃ / min and holding at that temperature for 1-2 hours, then heating to 320-370℃ at a heating rate of 4-6℃ / min and holding at that temperature for 1-3 hours, and finally heating to 450-550℃ at a heating rate of 4-6℃ / min and holding at that temperature for 2-4 hours.
[0010] Specifically, the muffle furnace calcination temperature is increased to 190~210℃ at 2℃ / min and calcined at this temperature for 1 hour to remove PVP. Then, the temperature is increased to 340~360℃ at 5℃ / min and calcined at this temperature for 2 hours to carbonize PAN. Finally, the temperature is increased to 480~520℃ at 5℃ / min and calcined at this temperature for 3 hours to oxidize the outer layer to CeO2.
[0011] Further, in step 4), the mass ratio of the fluoride spun fiber network CeF / C, polyethylene oxide, and lithium bis(trifluoromethanesulfonyl)imide is 1:(3~5):(1~1.5), the concentration of polyethylene oxide in acetonitrile is 0.1~0.3 g / mL, the thickness of the PEO-CeF / C solid electrolyte membrane is 100~200 μm, and drying refers to drying at room temperature for 10~12 hours, followed by drying at 40~60℃ for 5~8 hours. The molecular weight of polyethylene oxide is preferably 100,000~1,000,000.
[0012] Furthermore, EO and Li + The molar ratio is (16~32):1.
[0013] Furthermore, the PEO-CeF / C solid electrolyte prepared by the above method.
[0014] Furthermore, the application of the PEO-CeF / C solid electrolyte in lithium batteries.
[0015] Furthermore, lithium sheets are used as negative electrodes, and lithium sheets or lithium iron phosphate or ternary lithium positive electrodes are used as positive electrodes. The prepared PEO-CeF / C solid electrolyte membrane is used as the battery separator and electrolyte, and the batteries are assembled into lithium-lithium symmetric batteries or lithium iron phosphate or lithium ternary lithium full batteries.
[0016] Furthermore, the structure of a lithium-lithium symmetric battery is: positive electrode shell, lithium sheet, PEO-CeF / C solid electrolyte membrane, lithium sheet, gasket, and negative electrode shell; the structure of a lithium iron phosphate full battery is: positive electrode shell, lithium iron phosphate positive electrode, PEO-CeF / C solid electrolyte membrane, lithium sheet, gasket, and negative electrode shell; the structure of a lithium ternary lithium full battery is: positive electrode shell, NCM81 ternary lithium positive electrode, PEO-CeF / C solid electrolyte membrane, lithium sheet, gasket, and negative electrode shell.
[0017] Further, the preparation process of the lithium iron phosphate cathode is as follows: PVDF is added to NMP and stirred until completely dissolved. Lithium iron phosphate and acetylene black are ground and then poured into the PVDF NMP solution, stirred for 10-15 hours. The mixture is then coated onto the current collector with a spatula and dried to obtain the lithium iron phosphate cathode. The preparation process of the ternary lithium cathode is as follows: PVDF is added to NMP and stirred until completely dissolved. Ternary lithium and acetylene black are ground and then poured into the PVDF NMP solution, stirred for 10-15 hours. The mixture is then coated onto the current collector with a spatula and dried to obtain the ternary lithium cathode.
[0018] Furthermore, the mass ratio of the lithium iron phosphate powder (or NCM811 ternary lithium powder), acetylene black and PVDF is (7~9):(1~2):(1~2), specifically 8:1:1.
[0019] Furthermore, the loading of lithium iron phosphate or NCM811 ternary lithium on the positive electrode is 2~4 mg cm⁻¹. -2 .
[0020] The advantages over existing technologies are: Firstly, it improves the lithium-ion conductivity of solid-state batteries. By controlling the spinning process and calcination parameters, the morphology and dispersion uniformity of CeF3 / C fibers are achieved, and their one-dimensional continuous core-shell structure is used to construct a highly efficient lithium-ion conduction network. This electrolyte increases the lithium-ion conductivity to 1.28 × 10⁻⁶ at room temperature. -4 S cm -1 This far exceeds the levels currently reported.
[0021] Secondly, it enhances the stability of the electrode-electrolyte interface and improves the electrochemical performance of lithium batteries. The F in CeF3 / C fibers... - During lithium metal battery cycling, LiF is formed. This SEI film effectively blocks electron shuttle and inhibits the continuous decomposition of the electrolyte. At 0.1 mA cm⁻¹ -2 At current densities, the Li||Li symmetric battery assembled using PEO-CeF / C solid electrolyte achieves a cycle life of over 5000 hours. More importantly, the assembled Li||NCM811 solid-state battery overcomes the 4.5V high-voltage bottleneck, maintaining over 80% capacity retention after 100 cycles at 0.1C. Compared to other patents, this technology achieves ultra-long cycle stability while exhibiting excellent high-voltage resistance, resulting in a lifespan far exceeding other patented methods.
[0022] Thirdly, the coaxial electrospinning technique is novel and allows for the controllability of fluoride-spun fiber structure. This strategy is simple to prepare and widely applicable. First, a certain amount of PAN is dissolved in DMF and stirred for 4-6 hours to obtain a transparent solution, denoted as bottle a. Then, PAN and PVP are stirred in DMF at a mass ratio of 1:1 for 4-6 hours to obtain a transparent solution, and CeF3 powder is added and stirred evenly, denoted as bottle b. The solutions in bottles a and b are transferred to two 10mL plastic syringes and placed in the inner core and outer shell of a coaxial needle. Electrospinning is performed with certain parameters. Then, the solution is dried in a 60℃ drying oven for 6-8 hours and transferred to a muffle furnace for carbonization to form a fluoride-spun fiber network CeF / C. Finally, this fluoride-spun fiber is dissolved in excess acetonitrile with a certain amount of polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide, stirred evenly, and then placed in a polytetrafluoroethylene mold for drying to form a PEO-CeF / C solid electrolyte membrane. This strategy, through innovative spinning structure design, regulates the ionic conductivity and interfacial stability of PEO-based electrolytes, ultimately achieving a breakthrough in long cycle life for solid-state lithium batteries and providing a new approach for the design and development of high-performance solid-state electrolytes. Attached Figure Description
[0023] Figure 1 This is a flowchart of the preparation of CeF / C spinning fibers and the preparation of PEO-CeF / C solid electrolyte; Figure 2 Here is a surface morphology image of the CeF / C fibers prepared in Example 1; Figure 3 These are SEM images of the surface morphology of the PEO-CeF / C solid electrolyte in Comparative Example 1 and Example 1. Figure 4 The EIS curves of the solid electrolytes in Comparative Example 1 and Example 1 at different temperatures are shown. Figure 5 The ionic conductivity of the solid electrolytes in Comparative Example 1 and Example 1 at different temperatures; Figure 6 SEM images of the lithium electrode morphology after cycling of lithium-lithium symmetric batteries in Comparative Example 2 and Example 2; Figure 7 The ion transference number is the lithium-lithium symmetric battery of Comparative Example 2 and Example 2; Figure 8 This demonstrates the long-cycle stability of the lithium-lithium symmetric batteries in Comparative Example 2 and Example 2. Figure 9 The graphs show the cycle test curves of lithium iron phosphate batteries in Comparative Example 3 and Example 3 at 0.5C. Figure 10 The in-situ EIS curves of the lithium ternary lithium batteries of Comparative Example 4 and Example 4 at different voltages are shown. Figure 11These are TEM images of the CEI film on the positive electrode surface after cycling of the batteries in Comparative Example 4 and Example 4. Figure 12 This describes the long-cycle stability and voltage plateau of the lithium ternary lithium batteries in Comparative Example 4 and Example 4 at 0.1C. Detailed Implementation
[0024] The present invention will be further described below with reference to the accompanying drawings and examples.
[0025] Comparative Example 1 Preparation and structural characterization of traditional PEO solid electrolyte (PEO).
[0026] Step 1, Preparation of traditional PEO solid electrolyte 2g of polyethylene oxide (molecular weight 600,000) and 0.652g of lithium bis(trifluoromethanesulfonyl)imide were dissolved in 20mL of acetonitrile and stirred evenly. Then, the mixture was placed in a polytetrafluoroethylene mold and dried naturally in a glove box for 18 hours. After that, it was transferred to a vacuum oven and dried at 50°C for 6 hours to finally form a PEO solid electrolyte membrane with a thickness of about 150μm.
[0027] Step 2, Structural characterization of traditional PEO solid electrolytes The surface morphology was observed using a Zeiss focused dual-ion beam scanning electron microscope (SEM), such as... Figure 3 As shown, the PEO solid electrolyte exhibits a rough surface with obvious cracks and poor morphological stability. This indicates that the PEO solid electrolyte structure is unstable, with increased crystallinity leading to surface agglomeration and roughening, resulting in extremely low ionic conductivity. Figure 4 and Figure 5 As shown.
[0028] Comparative Example 2 Lithium-lithium symmetric batteries were assembled using PEO solid electrolyte.
[0029] Step 1, Lithium electrode preparation A 100μm thick pure lithium foil (purchased from Tianjin Zhongneng Lithium Industry Co., Ltd.) was gently scraped off with an iron rod to remove surface impurities, and then cut into 16mm diameter round pieces to make lithium electrodes for use.
[0030] Step 2, Lithium-Lithium Symmetric Battery Assembly The lithium electrodes were assembled into a symmetrical CR2032 model battery (20.0 mm in diameter and 3.2 mm in thickness) for cycle stability testing. The battery components, in sequence, consisted of a positive electrode shell, lithium sheet, PEO solid electrolyte, lithium sheet, stainless steel gasket (16 mm in diameter and 1 mm in thickness), and negative electrode shell, with a sealing pressure of approximately 50 kg / cm³. The battery needed to be left to stand at 60°C for at least 8 hours before use. The PEO solid electrolyte prepared in Comparative Example 1 was used as both the separator and the battery electrolyte.
[0031] Step 3, Lithium-Lithium Symmetric Battery Testing Symmetrical battery long-cycle testing was conducted in a 60℃ constant temperature chamber to eliminate the influence of ambient temperature. Battery testing utilized a battery testing system from Wuhan Landian. Figure 8 As shown, the test parameters were set to constant current discharge and constant current charge, with a current density of 0.1 mA / cm² based on the electrode area. 2 The surface area capacity is 0.1mAh / cm². 2 Under these test conditions, the lifespan of a symmetric cell using PEO solid electrolyte is approximately 198 hours, indicating that the lifespan of a cell using PEO solid electrolyte is relatively short.
[0032] Step 4: Observation of the surface morphology of lithium symmetric batteries The surface morphology of lithium electrodes after 198 hours of degradation was observed using a Zeiss focused dual-ion-beam scanning electron microscope (SEM). Figure 6 As shown, after long-term deposition and stripping, the electrode surface is covered with disordered and irregular dead lithium, which is the main cause of battery short circuits.
[0033] Comparative Example 3 Assembling lithium iron phosphate full cells using PEO solid electrolyte Step 1, Lithium electrode preparation Same as Comparative Example 2, Step 1.
[0034] Step 2, Preparation of Lithium Iron Phosphate Cathode First, NMP (1.1 mL) was added to a glass vial, followed by PVDF (50 mg), and the mixture was stirred for 1 hour. Then, acetylene black (50 mg) and LiFPO4 (400 mg) were added to a mortar. After grinding for 20 minutes, the mixture was poured into the glass vial and stirred for 12 hours. The mixed slurry was then poured onto aluminum foil and spread evenly using a 200 μm spatula. The mixture was then incubated at 80°C for 6 hours to obtain the LiFPO4 cathode (LFP). The LFP loading mass was approximately 3 mg cm⁻¹. -2 .
[0035] Step 3, Full Battery Assembly Lithium and lithium iron phosphate electrodes were assembled into a CR2032 full cell (20.0 mm in diameter and 3.2 mm in thickness). The assembly sequence was as follows: positive electrode shell, lithium iron phosphate positive electrode sheet, PEO solid electrolyte, lithium sheet, stainless steel gasket (1 mm thick), and negative electrode shell. The sealing pressure was approximately 50 kg / cm³. The battery needed to be left to stand at 60°C for 8 hours before use. The PEO solid electrolyte prepared in Comparative Example 1 was used as both the separator and the battery electrolyte.
[0036] Step 4, Lithium Iron Phosphate Full Battery Testing The full battery test used Wuhan Landian's battery testing system. Charge and discharge tests were conducted at 60℃ and a 0.5C rate. Figure 9 As shown, the initial discharge specific capacity is 160 mAh g. -1 It then showed a downward trend, with the capacity dropping to 0 mAh g after approximately 90 cycles. -1 .
[0037] Comparative Example 4 Assembling lithium ternary lithium full cells using PEO solid electrolyte Step 1, Preparation of PEO solid electrolyte membrane Same as step 1 in Comparative Example 1.
[0038] Step 2, lithium electrode preparation.
[0039] Same as Comparative Example 2, Step 1.
[0040] Step 3, Preparation of ternary lithium NCM811 cathode First, NMP (1.1 mL) was added to a glass vial, followed by PVDF (50 mg), and stirred for 1 hour. Then, acetylene black (50 mg) and NCM811 (400 mg) were added to a mortar. After grinding for 20 minutes, the mixture was poured into the glass vial and stirred for 12 hours. The mixed slurry was poured onto aluminum foil, spread evenly with a 200 μm spatula, and kept at 80°C for 6 hours to obtain the ternary lithium cathode (NCM811). The loading mass of NCM811 was approximately 3 mg cm⁻¹. -2 .
[0041] Step 4, Full Battery Assembly The lithium electrode and the ternary lithium NCM811 electrode are assembled into a CR2032 model (20.0 mm in diameter and 3.2 mm in thickness) full cell. The assembly sequence of the entire battery is as follows: positive electrode shell, ternary lithium NCM811 positive electrode sheet, PEO solid electrolyte, lithium electrode, stainless steel gasket (1 mm thick), and negative electrode shell. The sealing pressure is approximately 50 kg / cm³. The battery needs to be left to stand at 60°C for 8 hours before use.
[0042] Step 4, Lithium-ion ternary lithium full battery test The full battery test used Wuhan Landian's battery testing system. Charge and discharge tests were conducted at 60℃ and a 0.1C rate. Figure 12 As shown, the initial discharge specific capacity is 190 mAh g. -1 Subsequently, the battery capacity decayed to 0 after approximately 100 cycles. Example 1
[0043] Preparation and structural characterization of PEO-CeF / C solid electrolyte Step 1, Preparation of CeF / C fluoride spun fibers like Figure 1 As shown, firstly, 1.32g of PAN (molecular weight: 1,500,000) was dissolved in 8mL of DMF and stirred for 6 hours to obtain a clear solution, designated as bottle a. Then, 1.2g of PAN (molecular weight: 1,500,000) and 0.3g of PVP (by mass ratio) were dissolved in 10mL of DMF and stirred for 6 hours to obtain a clear solution. Finally, 0.498g of CeF3 powder was added and stirred until homogeneous, designated as bottle b. The solutions from bottles a and b were transferred to two 10mL plastic syringes and positioned within the inner and outer shells of a coaxial needle. The coaxial needle was placed 16 cm away from the stainless steel foil collector. The coaxial electrospinning high-voltage power supply was set to 20 kV, driving the two syringes at a speed of 0.075 mm / min. -1 (Internal) and 0.1 mm min -1 Electrospinning is performed at an external speed. First, the fiber is dried at 60°C for 6 hours. Then, it is calcined in a muffle furnace at a rate of 2°C / min to about 200°C for 1 hour to remove PVP. Next, it is calcined at a rate of 5°C / min to about 350°C for 2 hours to carbonize PAN. Finally, it is calcined at a rate of 5°C / min to about 500°C for 3 hours to oxidize the outer layer to CeO2. Finally, a fluoride spun fiber network CeF / C is formed.
[0044] Step 3, Preparation of PEO-CeF / C solid electrolyte 2g of polyethylene oxide (molecular weight 600,000), 0.652g of lithium bis(trifluoromethanesulfonyl)imide, and 0.5g of CeF / C spinning fiber were dissolved in 20mL of acetonitrile and stirred evenly. The solution was then placed in a polytetrafluoroethylene mold and dried naturally in a glove box for 10-12 hours. After that, it was transferred to a vacuum oven and dried at 50°C for 6 hours to form a 150μm thick PEO-CeF / C solid electrolyte membrane.
[0045] Step 4, Structural characterization of PEO-CeF / C solid electrolyte The surface morphology was observed using a Zeiss focused dual-ion beam scanning electron microscope (SEM), such as... Figure 2As shown, the CeF / C fluoride spun fiber network exhibits a core-shell structure, which facilitates lithium-ion migration. Furthermore, as... Figure 3 As shown, the surface of the PEO-CeF / C solid electrolyte is smooth and free of obvious defects. Furthermore, the ionic conductivity of the PEO-CeF / C solid electrolyte can reach 1.28 × 10⁻⁶. -4 S cm -1 It is superior to the comparative example, such as Figure 4 and Figure 5 As shown, this facilitates lithium-ion migration.
[0046] Table 1. Ionic conductivity of traditional PEO solid electrolyte and PEO-CeF / C solid electrolyte Example 2
[0047] Lithium-lithium symmetric batteries were assembled using PEO-CeF / C solid electrolyte.
[0048] Step 1, Preparation of PEO-CeF / C solid electrolyte Same as step 3 in Example 1.
[0049] Step 2, Lithium electrode preparation Same as step 1 in Comparative Example 2.
[0050] Step 3: Assemble lithium-lithium symmetric batteries using PEO-CeF / C solid electrolyte. The lithium electrodes were assembled into a CR2032 model symmetrical battery (20.0 mm in diameter and 3.2 mm in thickness) for cycle stability testing. The battery components, in sequence, consisted of a positive electrode shell, lithium sheet, PEO-CeF / C solid electrolyte, lithium sheet, stainless steel gasket (16 mm in diameter and 1 mm in thickness), and negative electrode shell, with a sealing pressure of approximately 50 kg / cm³. The battery needed to be left to stand at 60°C for at least 8 hours before use. The PEO-CeF / C solid electrolyte prepared in Comparative Example 1 was used as both the separator and the battery electrolyte.
[0051] Step 4: Assembly and testing of lithium-lithium symmetric batteries using PEO-CeF / C solid electrolyte. Cyclic testing was performed on the lithium-lithium symmetric battery assembled with the PEO-CeF / C solid electrolyte obtained in step 3. The battery testing used a battery testing system from Wuhan Landian. Figure 8 As shown, the test parameters were set to constant current discharge and constant current charge, with a current density of 0.1 mA / cm² based on the electrode area. 2 The surface area capacity is 0.1mAh / cm². 2Under these test conditions, the symmetric cell using PEO-CeF / C solid electrolyte can achieve a lifespan of over 5500 hours, demonstrating ultra-long cycling performance and excellent electrochemical properties.
[0052] Step 5: Use SEM to observe the surface morphology of the lithium electrode after long-term cycling. After cycling tests, the surface morphology of the lithium electrode in the PEO-CeF / C solid electrolyte-assembled lithium-lithium symmetric battery is as follows: Figure 6 As shown, the lithium surface exhibits a dense deposition without obvious dendrites and has a smooth surface. Compared with the use of PEO solid electrolyte, the lithium deposition is significantly smoother and more orderly, indicating that PEO-CeF / C solid electrolyte can regulate lithium migration and deposition.
[0053] Step 6: Explain the mechanism of action of PEO-CeF / C solid electrolyte in lithium batteries. F in CeF / C fiber - During lithium metal battery cycling, LiF is formed. This SEI film effectively blocks electron shuttle and inhibits continuous electrolyte decomposition. Simultaneously, CeF3 in the CeF / C fibers coordinates with lithium ions, reducing the coordination of EO groups with lithium ions in PEO, thereby decreasing the crystallinity of PEO, increasing ionic conductivity, and promoting lithium ion migration. Figure 7 As shown. Example 3
[0054] PEO-CeF / C solid electrolyte is used in lithium iron phosphate full cells.
[0055] Step 1, Preparation of PEO-CeF / C solid electrolyte Same as step 2 in Example 1.
[0056] Step 2, Lithium electrode preparation Same as step 1 in Comparative Example 2.
[0057] Step 3, Preparation of lithium iron phosphate cathode Same as step 2 of Comparative Example 3.
[0058] Step 4: Assemble lithium iron phosphate full cells using PEO-CeF / C solid electrolyte. The lithium electrode and lithium iron phosphate electrode were assembled into a CR2032 full cell (20.0 mm in diameter and 3.2 mm in thickness). The assembly sequence of the entire battery was as follows: positive electrode shell, lithium iron phosphate positive electrode sheet, PEO-CeF / C solid electrolyte, lithium sheet, stainless steel gasket (1 mm thick), and negative electrode shell. The sealing pressure was approximately 50 kg / cm³. The battery needed to be left to stand at 60°C for 8 hours before use. The PEO-CeF / C solid electrolyte prepared in Example 1 was used as the separator and battery electrolyte.
[0059] Step 5: Assembly and testing of lithium iron phosphate full cells using PEO-CeF / C solid electrolyte. The full battery test used Wuhan Landian's battery testing system. Charge and discharge tests were conducted at 60℃ and a 0.5C rate. Figure 9 As shown, the initial discharge specific capacity is 160 mAh g. -1 Subsequently, after approximately 250 cycles, the specific capacity remained at 150 mAh g. -1 above.
[0060] Step 6: Compare the performance of the lithium iron phosphate full battery with the comparative example. Lithium iron phosphate full cells assembled using PEO solid electrolyte exhibit rapid capacity decay under 0.5C charge-discharge conditions, making them unsuitable for practical applications. Furthermore, they are prone to overcharging and short circuits under 0.5C charge-discharge conditions, primarily due to interface instability. In contrast, lithium iron phosphate full cells assembled using PEO-CeF / C solid electrolyte maintain excellent specific capacity even after 250 cycles under 0.5C charge-discharge conditions, demonstrating superior electrochemical performance. Example 4
[0061] PEO-CeF / C solid electrolyte is used in lithium ternary lithium full batteries.
[0062] Step 1, Preparation of PEO-CeF / C solid electrolyte Same as step 2 in Example 1.
[0063] Step 2, Lithium electrode preparation Same as step 1 in Comparative Example 2.
[0064] Step 3, Preparation of ternary lithium NCM811 cathode Same as step 2 of Comparative Example 4.
[0065] Step 4: Assemble lithium ternary lithium full cells using PEO-CeF / C solid electrolyte. The lithium electrode and the ternary lithium NCM811 electrode are assembled into a CR2032 model (20.0 mm in diameter and 3.2 mm in thickness) full cell. The assembly sequence of the entire battery is as follows: positive electrode shell, ternary lithium NCM811 positive electrode sheet, PEO-CeF / C solid electrolyte, lithium electrode, stainless steel gasket (1 mm thick), and negative electrode shell. The sealing pressure is approximately 50 kg / cm³. The battery needs to be left to stand at 60°C for 8 hours before use.
[0066] Step 5, Lithium-ion ternary lithium full battery test The full battery test used Wuhan Landian's battery testing system. Charge and discharge tests were conducted at 60℃ and a 0.1C rate. Figure 12 As shown, the initial discharge specific capacity is 190 mAh g. -1 It remains stable, retaining 80% of its capacity after 100 cycles. Furthermore, the lithium ternary lithium full cell assembled with PEO-CeF / C solid electrolyte can break through the 4.5V bottleneck, achieving a stable voltage platform and capacity retention.
[0067] Step 6, Analysis of the High Voltage Tolerance Mechanism of Lithium Ternary Lithium Full Cells In-situ impedance characterization techniques were used to reveal the failure evolution process of lithium ternary batteries between 3 and 4.5V, such as... Figure 10 As shown, during the initial charging process, the charge transfer impedance in the mid-frequency region exhibits a semi-circular stability. At this time, the lithiation degree of NCM811 is low, and the physical barrier formed by CeF / C isolates the direct reaction between the positive electrode and PEO, with no obvious by-products generated at the interface. However, when the battery is charged to 4V, the charge transfer impedance at the battery interface increases significantly. During this stage, a large number of by-products accumulate at the interface, forming a thick and dense CEI layer, such as... Figure 11 As shown, CeF / C decomposes at the electrode interface to form LiF, which to some extent suppresses TFSI. - The decomposition of EO further enhances the cycle stability of the 4.5 V solid-state battery.
[0068] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the claims.
[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention is determined by the claims. Similarly, any equivalent structural changes made based on the content of the present invention's specification should also be included within the scope of protection of the present invention.
Claims
1. A method for preparing a PEO-CeF / C solid-state electrolyte, characterized by, The preparation process is as follows: 1) Dissolve polyacrylonitrile in DMF and stir for 4-6 hours to obtain a transparent solution, which is recorded as bottle a; then dissolve polyacrylonitrile and polyvinylpyrrolidone in DMF and stir for 4-6 hours to obtain a transparent solution, then add CeF3 powder and stir evenly, which is recorded as bottle b; 2) Transfer the solutions from bottles a and b in step 1) into two syringes. Place the syringe containing the solution into the inner core and outer shell of the coaxial needle. Place the coaxial needle 15-17 cm away from the stainless steel foil collector. Set the parameters to perform electrospinning to obtain spun fibers. 3) The spun fibers obtained in step 2) are dried at 50~70℃ for 5~8 hours, and then transferred to a muffle furnace for carbonization to form a fluoride spun fiber network CeF / C; 4) Dissolve the fluoride spinning fiber network CeF / C from step 3) with polyethylene oxide and lithium bis(trifluoromethanesulfonylimide) in acetonitrile, stir evenly, and then place it in a polytetrafluoroethylene mold to dry, finally forming a PEO-CeF / C solid electrolyte membrane.
2. The method for preparing the PEO-CeF / C solid electrolyte according to claim 1, characterized in that, In step 1), the concentration of polyacrylonitrile in DMF in bottle a is 0.1~0.2 g / mL; the mass ratio of polyacrylonitrile, polyvinylpyrrolidone and CeF3 powder in bottle b is (3~5):1:(1.5~2), and the concentration of polyacrylonitrile in DMF is 0.1~0.15 g / mL.
3. The method for preparing the PEO-CeF / C solid electrolyte according to claim 1, characterized in that, In step 2), the coaxial electrospinning high-voltage power supply is set to 15-25 kV, and the syringe connected to the inner core of the coaxial needle is driven at a speed of 0.05-0.1 mm / min -1 , and the syringe connected to the outer shell of the coaxial needle is driven at a speed of 0.05-0.15 mm / min -1 .
4. The method of claim 1, wherein the PEO-CeF / C solid-state electrolyte is prepared by the steps of: In step 3), carbonization refers to first heating the temperature to 180-220℃ at a heating rate of 1-3℃ / min and holding it for 1-2 hours, then heating the temperature to 320-370℃ at a heating rate of 4-6℃ / min and holding it for 1-3 hours, and finally heating the temperature to 480-520℃ at a heating rate of 4-6℃ / min and holding it for 2-4 hours.
5. The method for preparing PEO-CeF / C solid electrolyte according to claim 1, characterized in that, In step 4), the mass ratio of the fluoride spun fiber network CeF / C, polyethylene oxide, and lithium bis(trifluoromethanesulfonyl)imide is 1:(3~5):(1~1.5), the concentration of polyethylene oxide in acetonitrile is 0.1~0.3 g / mL, the thickness of the PEO-CeF / C solid electrolyte membrane is 100~200 μm, and drying refers to drying at room temperature for 10~12 hours first, and then drying at 40~60℃ for 5~8 hours.
6. The PEO-CeF / C solid electrolyte prepared by the preparation method according to any one of claims 1 to 5.
7. The application of the PEO-CeF / C solid electrolyte according to claim 6 in lithium batteries, characterized in that, Lithium foil is used as the negative electrode, and lithium foil, lithium iron phosphate, or ternary lithium is used as the positive electrode. The prepared PEO-CeF / C solid electrolyte membrane is used as the battery separator and electrolyte, and the cells are assembled into lithium-lithium symmetric batteries, lithium iron phosphate, or lithium ternary lithium full batteries.
8. The application according to claim 7, characterized in that, The structure of a lithium-ion symmetric battery is: positive electrode shell, lithium sheet, PEO-CeF / C solid electrolyte membrane, lithium sheet, gasket, and negative electrode shell; the structure of a lithium iron phosphate full battery is: positive electrode shell, lithium iron phosphate positive electrode, PEO-CeF / C solid electrolyte membrane, lithium sheet, gasket, and negative electrode shell; the structure of a lithium ternary lithium full battery is: positive electrode shell, ternary lithium positive electrode, PEO-CeF / C solid electrolyte membrane, lithium sheet, gasket, and negative electrode shell.
9. The application according to claim 7 or 8, characterized in that, The preparation process of lithium iron phosphate cathode is as follows: PVDF is added to NMP and stirred until completely dissolved. Lithium iron phosphate and acetylene black are ground and then poured into the PVDF NMP solution and stirred for 10-15 hours. The solution is then coated onto the current collector with a scraper and dried to obtain lithium iron phosphate cathode. The preparation process of ternary lithium cathode is as follows: PVDF is added to NMP and stirred until completely dissolved. Ternary lithium and acetylene black are ground and then poured into the PVDF NMP solution and stirred for 10-15 hours. The solution is then coated onto the current collector with a scraper and dried to obtain ternary lithium cathode.
10. The application according to claim 9, characterized in that, The mass ratio of lithium iron phosphate powder or ternary lithium powder, acetylene black and PVDF is (7~9):(1~2):(1~2).