Method for preparing solid-state lithium ion battery polymer electrolyte by taking potassium titanate as filler

Abstract

The invention discloses a method for preparing a solid-state lithium ion battery polymer electrolyte by taking potassium titanate as a filler, and belongs to the field of lithium ion battery solid-state electrolyte materials. The method comprises the following steps: preparing a potassium titanate filler by adopting a solution-gel method, uniformly dispersing the potassium titanate filler in a solid electrolyte precursor solution, and forming the solid electrolyte membrane by adopting a solution pouring process. A uniform pore structure is formed in the obtained electrolyte, and a continuous lithium ion transmission channel is constructed, so that the migration ability and electrochemical performance of lithium ions are remarkably improved. Test results show that the ionic conductivity of the electrolyte at room temperature reaches 1.69 * 10 <-4 > S.cm <-1 >, the stable electrochemical window is widened to 4.62 V, and the specific discharge capacity is still maintained at 100 mAh.g <-1 > after 100 cycles at 1C multiplying power. The invention shows that the comprehensive electrochemical performance of the solid electrolyte can be effectively improved by introducing the potassium titanate filler, and the solid electrolyte has good research value and application prospect.

Description

Technical Field

[0001] This invention relates to the field of solid-state lithium-ion battery materials, specifically providing a method using potassium titanate (K2Ti6O) 13 A composite solid electrolyte synergistically modified with nanofillers and a polyacrylonitrile (PAN) / polyvinylidene fluoride (PVDF) dual polymer matrix. This electrolyte exhibits a room temperature ionic conductivity ≥1.69 × 10⁻⁶. -4 S / cm), electrochemical window (≥4.62V vs. Li) + It has significant advantages in terms of Li) and interface stability (capacity retention of 80% after 100 cycles), making it suitable for high energy density solid-state battery systems. Background Technology

[0002] Currently, the development of solid-state lithium-ion batteries is facing key technological bottlenecks. Although solid-state systems, represented by polymer / inorganic composite electrolytes, have solved the thermal runaway risk of traditional lithium metal batteries by eliminating liquid components (He et al., Energy Environ. Mater. 2024, 7:4), existing technologies still have irreconcilable contradictions: on the one hand, the room temperature ionic conductivity of pure polymer electrolytes (such as PEO-based electrolytes) is generally lower than 10. -5 The mechanical strength is insufficient, leading to lithium dendrite penetration (Zhang et al., Coord. Chem. Rev. 2025, 528:216432); on the other hand, although adding traditional inorganic fillers (such as Al2O3 or LLZO) can improve mechanical properties, particle agglomeration causes a surge in interfacial resistance (interfacial resistance > 200 Ω·cm). 2 This leads to a narrowing of the electrochemical window (<4.2V). Of particular note is the recent finding that while titanate fillers (such as SrTiO3) can improve ion transport, their side reactions with lithium metal can generate an insulating phase, Li2TiO3, which leads to a continuous deterioration of interfacial stability during cycling (Nomura et al., ACS Energy Lett. 2025, 10: 1404-1410).

[0003] Against this backdrop, the innovative breakthrough of this invention lies in the first disclosure of potassium titanate (K2Ti6O) 13 The unique synergistic mechanism of [TiO6]: its layered crystal structure contains [TiO6] octahedral channels (0.3 nm in diameter) that can provide [TiO6] with Li + A size-matched (0.076 nm) directional conduction pathway is established, while the residual citric acid ligand on the surface reduces the interfacial impedance to 55.4 Ω·cm through chelation with the lithium salt anion (TFSI-). 2More importantly, the precise control of the pore structure through the sol-gel method ensures uniform microstructure and surface morphology of the filler, thereby achieving a particle size of 1.69 × 10⁻⁶ at a low addition of 10 wt%. -4 A room-temperature conductivity of S / cm is achieved while maintaining a tensile strength of 12.3 MPa. This multi-scale synergistic effect successfully solves the problem of the incompatibility between "high conductivity, high mechanical strength, and wide electrochemical window" in traditional technologies. Summary of the Invention

[0004] In existing technologies, the core challenge facing polymer-based solid electrolytes lies in the difficulty of simultaneously achieving a synergistic optimization of high ionic conductivity, low interfacial impedance, and high mechanical strength. Traditional solutions, such as adding inert oxide fillers (e.g., Al₂O₃), can improve mechanical properties but lead to a decrease in conductivity due to their insulating properties. While highly active fillers (e.g., LLZO) improve ion transport, the particle coarsening (average particle size > 5 μm) caused by high-temperature sintering can lead to deterioration of interfacial contact (interfacial resistance > 200 Ω·cm). 2 This invention innovatively introduces potassium titanate (K2Ti6O). 13 As a multifunctional filler, combining the mesoporous structure prepared by the sol-gel method with surface citric acid coordination modification, it has achieved a triple breakthrough for the first time: ① room temperature ionic conductivity reaches 1.69×10 -4 S / cm, two orders of magnitude higher than pure PAN / PVDF matrix; ② Interfacial impedance reduced to 55.4Ω·cm 2 Superior to similar strontium titanate filler systems (>120Ω·cm) 2 ); ③ The tensile strength reaches 12.3 MPa, which can effectively suppress lithium dendrite penetration. Its technical essence lies in the [TiO6] octahedral channels (XRD 2θ=8.5°) of potassium titanate and Li + Precise size matching (0.076 nm) and coordination between surface -COOH groups and TFSI- anions jointly construct a fast lithium-ion transport network that runs through the polymer matrix.

[0005] The preparation method of this invention achieves the above-mentioned effects through the following key steps: First, a potassium titanate precursor is synthesized using a controlled hydrolysis process (pH = 4 ± 0.2, 70℃ water bath for 4 h), and then a filler with a complete crystal structure is obtained through stepwise sintering (400℃ × 2 h + 750℃ × 4 h); subsequently, 10 wt% potassium titanate and 100 wt% LiTFSI are embedded in a PAN / PVDF (1:6) matrix, coated into a film (150 ± 5 μm), and then vacuum dried. The innovation of this process is reflected in: ① the mesoporous structure achieved by the sol-gel method ensures uniform dispersion of the filler (SEM shows particle size deviation < 10%); ② citric acid precisely controls the chemical bonding at the filler-matrix interface; ③ the low-temperature film formation process (120℃) avoids polymer chain degradation. The finally assembled LiFePO4 full cell maintains 80% capacity after 100 cycles at 1C under a wide electrochemical window of 4.62 V, confirming the feasibility of its commercial application.

[0006] The specific implementation process includes five innovative steps:

[0007] I. Preparation of Potassium Titanate

[0008] Mix titanate and alcohol solvent at a volume ratio of 1:5-1:10, stir magnetically to form a homogeneous solution, add citric acid (0.5 times the mass of alcohol solvent) as a complexing agent, and continue stirring for 20-60 minutes until completely dissolved.

[0009] Dissolve the potassium source in an alcohol / water mixture (volume ratio 1:1) at a mass ratio of 1:1 to 1:10, stir until clear, and then add it dropwise to the titanate precursor solution. Adjust the pH value to 2-5 with dilute nitric acid, and stir in a water bath at 40-80℃ for 2-8 hours to obtain a sol.

[0010] The sol was allowed to stand at room temperature for 12-48 hours to form a wet gel, then dried at 100-150℃ for 2-8 hours and milled, with each milling cycle occurring at 2℃ min. -1 Heat to 300-500℃ and hold for 1-6 hours to remove organic matter, then heat at 5℃ for 5 minutes. -1 Heat to 650-900℃ and hold for 2-8 hours, then cool with the furnace to obtain potassium titanate (K2Ti6O). 13 )filler;

[0011] II. Preparation of polymer electrolyte matrix precursor solution

[0012] Polyacrylonitrile and polyvinylidene fluoride were dissolved in N,N-dimethylformamide at a mass ratio of 1:1 to 1:10 and stirred at room temperature until dissolved.

[0013] III. Preparation of Polymer Electrolyte Precursor Solutions

[0014] Add 1-20% by weight of potassium titanate filler and 5-100% by weight of lithium salt to the solution in step two, and stir to mix evenly;

[0015] IV. Preparation of Polymer Electrolytes

[0016] The precursor solution was poured into a mold and vacuum dried at 60-140℃ to form a film.

[0017] V. Assembly of Solid-State Lithium-ion Batteries

[0018] The thin film, along with a lithium iron phosphate cathode and lithium sheet, were assembled into a solid-state battery in an argon-filled glove box.

[0019] In step one, the potassium source is selected from at least one of potassium nitrate and potassium acetate.

[0020] Furthermore, in step one, the mass ratio of the potassium source to the alcohol / water mixed solvent is 1:1 to 1:2.

[0021] Furthermore, in step one, the alcohol solvent is ethanol or isopropanol.

[0022] Furthermore, in step three, the lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium hexafluorophosphate.

[0023] Furthermore, a polymer electrolyte film prepared by a method that simultaneously incorporates all the above features is used as an electrolyte component.

[0024] Based on the above technical solution, the following beneficial effects are achieved:

[0025] This invention proposes a method for preparing solid-state lithium-ion battery polymer electrolyte materials using potassium titanate as a filler. Potassium titanate can significantly improve the electrochemical performance of PAN / PVDF hybrid matrices, primarily due to the synergistic enhancement effect between its unique physicochemical properties and the matrix.

[0026] Structure-function synergy: The pore channels of potassium titanate form a three-dimensional continuous ion transport network with the polymer matrix (SEM shows porosity >30%), enabling Li... + The migration count increased to 0.80;

[0027] Interface stability: The chelation between -COOH on the filler surface and lithium salt anions inhibited side reactions;

[0028] Economic efficiency: The solution-gel method reduces energy consumption by 70% compared to the solid phase method, and the raw material cost is less than $50 / kg (40% of LLZO).

[0029] From an ion transport perspective, the vast majority of potassium titanate particles are of similar size, with particle size differences strictly controlled within the micrometer range. This uniform particle size distribution gives it excellent ionic conductivity. When uniformly dispersed in a matrix composed of polar PAN and PVDF, it can construct efficient ion migration interface channels within the polymer network, effectively reducing the transport resistance of charge carriers such as lithium ions, thereby significantly improving the overall ionic conductivity and rate performance of the composite material. Experiments show that at 1C, after 100 cycles, the discharge specific capacity remains at 100 mAh·g. -1 This invention employs a solution-gel process, which has low raw material costs and solves the problem of poor electrochemical performance of solid electrolytes, while providing a cost-effective solution for commercialization. Attached Figure Description

[0030] To more clearly illustrate the modified results of the embodiments of the present invention, the accompanying drawings used in the description of the comparative examples and embodiments will be briefly introduced below.

[0031] Figure 1 This is a graph showing the electrochemical stability window of a polymer electrolyte for a method of preparing a solid-state lithium-ion battery polymer electrolyte using potassium titanate as a filler.

[0032] Figure 2 Cyclic voltammetry curves of lithium iron phosphate half-cells assembled with polymer electrolyte prepared by a method of preparing polymer electrolyte for solid-state lithium-ion batteries using potassium titanate as filler.

[0033] Figure 3 Impedance diagrams before and after polarization and current-time curves during polarization of a lithium iron phosphate half-cell assembled with polymer electrolyte prepared by a method of preparing polymer electrolyte for solid lithium-ion batteries using potassium titanate as filler.

[0034] Figure 4 This is an X-ray diffraction (XRD) pattern of potassium titanate in a method for preparing polymer electrolytes for solid-state lithium-ion batteries using potassium titanate as a filler.

[0035] Figure 5 This is a scanning electron microscope (SEM) image of potassium titanate used in a method for preparing polymer electrolytes for solid-state lithium-ion batteries using potassium titanate as a filler.

[0036] Figure 6 This is a scanning electron microscope (SEM) image of a polymer electrolyte used in a method for preparing a solid-state lithium-ion battery polymer electrolyte with potassium titanate as a filler.

[0037] Figure 7Scanning electron microscope (SEM) images of polymer electrolyte comparison samples (without filler) for a method of preparing polymer electrolyte for solid-state lithium-ion batteries using potassium titanate as filler: (a) LiTFSI / PVDF; (b) LiTFSI / PAN / PVDF;

[0038] Figure 8 This is an electrochemical stability window diagram of a polymer electrolyte comparison sample (without filler) for a method of preparing polymer electrolyte for solid-state lithium-ion batteries using potassium titanate as filler.

[0039] Figure 9 Cyclic voltammetry curves of a polymer electrolyte control sample (without filler) for a method of preparing polymer electrolyte for solid-state lithium-ion batteries using potassium titanate as filler.

[0040] Figure 10 Impedance diagrams before and after polarization and current-time curves during polarization of a Li|electrolyte|Li battery prepared by a method for preparing polymer electrolytes for solid-state lithium-ion batteries using potassium titanate as filler.

[0041] Figure 11 This is an elemental energy distribution surface mapping (EDS-mapping) diagram of potassium titanate used in a method for preparing polymer electrolytes for solid-state lithium-ion batteries using potassium titanate as a filler.

[0042] Figure 12 Electrochemical impedance spectroscopy (EIS) is used to test the conductivity of a polymer electrolyte prepared by a method for preparing polymer electrolytes for solid-state lithium-ion batteries using potassium titanate as a filler.

[0043] Figure 13 The electrochemical impedance spectroscopy of the polymer electrolyte prepared by a method for preparing polymer electrolytes for solid lithium-ion batteries using potassium titanate as filler is shown in Comparative Example 1, which tests the conductivity.

[0044] Figure 14 The electrochemical impedance spectroscopy of the polymer electrolyte prepared by a method for preparing polymer electrolytes for solid lithium-ion batteries using potassium titanate as filler is shown in Comparative Example 2, which tests the conductivity.

[0045] Figure 15 The electrochemical impedance spectroscopy of the polymer electrolyte prepared by a method for preparing polymer electrolytes for solid lithium-ion batteries using potassium titanate as filler is shown in Comparative Example 3, which tests the conductivity.

[0046] Figure 16 The image shows the voltage-specific capacity curve of a lithium iron phosphate half-cell assembled with a polymer electrolyte prepared by a method of preparing polymer electrolyte for solid-state lithium-ion batteries using potassium titanate as filler, at 1C.

[0047] Figure 17 The image shows the voltage-specific capacity curve of a lithium iron phosphate half-cell assembled with a polymer electrolyte prepared by a method of preparing polymer electrolyte for solid lithium-ion batteries using potassium titanate as filler, at 1C.

[0048] Figure 18 This is a voltage-specific capacity curve of a lithium iron phosphate half-cell assembled with a polymer electrolyte prepared by a method of preparing polymer electrolyte for solid-state lithium-ion batteries using potassium titanate as filler, compared to a control sample (without filler).

[0049] Figure 19 Electrochemical impedance spectroscopy of an uncycled lithium iron phosphate half-cell assembled with a polymer electrolyte prepared by a method of preparing polymer electrolyte for solid lithium-ion batteries using potassium titanate as filler.

[0050] Figure 20 Electrochemical impedance spectroscopy of a non-cycled lithium iron phosphate half-cell, used as a polymer electrolyte control sample (without filler) in a method for preparing polymer electrolytes for solid-state lithium-ion batteries using potassium titanate as filler.

[0051] Figure 21 This is a constant current polarization diagram of a lithium symmetric battery assembled using a method for preparing a solid-state lithium-ion battery polymer electrolyte with potassium titanate as a filler.

[0052] Figure 22 This is a specific capacity-efficiency diagram of a lithium iron phosphate half-cell assembled with a polymer electrolyte prepared by a method of preparing polymer electrolyte for solid-state lithium-ion batteries using potassium titanate as filler, under 1C cycling.

[0053] Figure 23 This is a specific capacity-efficiency diagram of a lithium iron phosphate half-cell assembled using a method for preparing polymer electrolytes for solid-state lithium-ion batteries with potassium titanate as filler, under 1C cycling.

[0054] Figure 24 This is a specific capacity-efficiency diagram of a lithium iron phosphate half-cell assembled using a method for preparing polymer electrolytes for solid-state lithium-ion batteries with potassium titanate as filler, under 1C cycling conditions. Figure 25 The ionic conductivity of PAN / PVDF electrolyte is given by different raw material contents. Detailed Implementation

[0055] The following embodiments further illustrate the above-mentioned content of the present invention in detail. However, the subject matter of the present invention is not limited to the following embodiments, and all technologies implemented based on the above-mentioned content of the present invention fall within the scope of the present invention.

[0056] The reagents used in the experiment are shown in Table 1, and the instruments used in the experiment are shown in Table 2.

[0057] Table 1. Drugs used in the experiment

[0058]

[0059]

[0060] Table 2. Instruments and equipment used in the experiment

[0061]

[0062] The preparation process steps of the following examples are further described in conjunction with the accompanying drawings and comparative examples, but the scope of protection of the present invention is not limited to the following examples.

[0063] Example: A method for preparing a solid-state lithium-ion battery polymer electrolyte using potassium titanate as a filler according to this example is carried out according to the following steps:

[0064] I. Preparation of Potassium Titanate

[0065] First, mix 5 ml of titanate with 10 ml of anhydrous ethanol and stir magnetically to form a homogeneous solution. Then, add 3.9 g of citric acid as a complexing agent and continue stirring for 30 minutes until completely dissolved to obtain a transparent solution.

[0066] Dissolve 5g of potassium nitrate (KNO3) in 10ml of ethanol / water mixed solvent (volume ratio 1:1), stir until clear, and then slowly add it dropwise to the titanate precursor solution while keeping the stirring vigorous. After the addition is complete, adjust the pH value to 4 with dilute nitric acid, and stir in a 60℃ water bath for 4h to obtain a uniform and transparent sol.

[0067] Pour the sol into a petri dish and let it stand at room temperature for 24 hours to form a wet gel. Dry at 120°C for 6 hours, then grind into a dry gel powder. Finally, spray at 2°C for 1 minute... -1 Heat to 400℃ and hold for 2 hours (to remove organic matter), then heat at 5℃ for 5 minutes. -1 The temperature was raised to 750℃ and held for 4 hours, then cooled in the furnace to obtain the final product, potassium titanate (K2Ti6O3), which is a polymer electrolyte. 13 )filler;

[0068] II. Preparation of polymer electrolyte matrix precursor solution

[0069] 0.05 g of polyacrylonitrile and 0.3 g of polyvinylidene fluoride were dissolved in 5 ml of organic solvent N,N-dimethylformamide and stirred evenly at room temperature to obtain a precursor solution of polymer electrolyte matrix.

[0070] III. Preparation of Polymer Electrolyte Precursor Solutions

[0071] 0.035g of filler and 0.35g of lithium salt were introduced into the polymer electrolyte matrix solution and mixed by stirring at room temperature to obtain a homogeneous polymer electrolyte precursor solution.

[0072] IV. Preparation of Polymer Electrolytes

[0073] The precursor solution was cast and dried under vacuum at 120°C to obtain a polymer electrolyte film.

[0074] V. Assembly of Solid-State Lithium-ion Batteries

[0075] After slicing the polymer electrolyte, it is assembled in sequence in an argon-filled glove box in the following order: positive electrode shell, lithium iron phosphate positive electrode, polymer electrolyte film, lithium sheet, gasket, spring sheet, and negative electrode shell, thus obtaining the practically applicable polymer electrolyte modified with potassium titanate.

[0076] Comparative Example 1: A method for preparing a solid-state lithium-ion battery polymer electrolyte using potassium titanate as a filler in this embodiment is carried out according to the following steps:

[0077] I. Preparation of Potassium Titanate

[0078] First, mix 5 ml of titanate with 10 ml of anhydrous ethanol and stir magnetically to form a homogeneous solution. Then, add 3.9 g of citric acid as a complexing agent and continue stirring for 30 minutes until completely dissolved to obtain a transparent solution.

[0079] Dissolve 5g of KNO3 in 10ml of ethanol / water mixed solvent (volume ratio 1:1), stir until clear, and then slowly add the titanate precursor solution dropwise while maintaining vigorous stirring. After the addition is complete, adjust the pH value to 4 with dilute nitric acid, and stir in a 60℃ water bath for 4h to obtain a uniform and transparent sol.

[0080] Pour the sol into a petri dish and let it stand at room temperature for 24 hours to form a wet gel. Dry at 120°C for 6 hours, then grind into a dry gel powder. Finally, spray at 2°C for 1 minute... -1 Heat to 400℃ and hold for 2 hours (to remove organic matter), then heat at 5℃ for 5 minutes. -1 The temperature was raised to 750℃ and held for 4 hours, then cooled in the furnace to obtain the final product, polymer electrolyte filler.

[0081] II. Preparation of polymer electrolyte matrix precursor solution

[0082] 0.05 g of polyacrylonitrile and 0.3 g of polyvinylidene fluoride were dissolved in 5 ml of organic solvent N,N-dimethylformamide and stirred evenly at room temperature to obtain a precursor solution of polymer electrolyte matrix.

[0083] III. Preparation of Polymer Electrolyte Precursor Solutions

[0084] 0.0175 g of filler and 0.35 g of lithium salt were introduced into the polymer electrolyte matrix solution and mixed by stirring at room temperature to obtain a homogeneous polymer electrolyte precursor solution.

[0085] IV. Preparation of Polymer Electrolytes

[0086] The precursor solution was cast and dried under vacuum at 120°C to obtain a polymer electrolyte film.

[0087] V. Assembly of Solid-State Lithium-ion Batteries

[0088] After slicing the polymer electrolyte, it is assembled in sequence in an argon-filled glove box in the following order: positive electrode shell, lithium iron phosphate positive electrode, polymer electrolyte film, lithium sheet, gasket, spring sheet, and negative electrode shell, thus obtaining the practically applicable polymer electrolyte modified with potassium titanate.

[0089] Comparative Example 2:

[0090] I. Preparation of Potassium Titanate

[0091] First, mix 5 ml of titanate precursor with 10 ml of anhydrous ethanol, stir magnetically to form a homogeneous solution, add complexing agent, and continue stirring for 30 min until completely dissolved to obtain a transparent solution.

[0092] Dissolve 5g of KNO3 in 10ml of ethanol / water mixed solvent, stir until clear, and then slowly add it dropwise to the titanate precursor solution while stirring vigorously. After the addition is complete, adjust the pH to 4 with dilute nitric acid, and stir in a 60℃ water bath for 4h to obtain a uniform and transparent sol.

[0093] Pour the sol into a petri dish and let it stand at room temperature for 24 hours to form a wet gel. Dry at 120°C for 6 hours, then grind into a dry gel powder. Finally, spray at 2°C for 1 minute... -1 Heat to 400℃ and hold for 2 hours (to remove organic matter), then heat at 5℃ for 5 minutes. -1 The temperature was raised to 750℃ and held for 4 hours, then cooled in the furnace to obtain the final product, polymer electrolyte filler.

[0094] II. Preparation of polymer electrolyte matrix precursor solution

[0095] 0.05 g of polyacrylonitrile and 0.3 g of polyvinylidene fluoride were dissolved in 5 ml of organic solvent N,N-dimethylformamide and stirred evenly at room temperature to obtain a precursor solution of polymer electrolyte matrix.

[0096] III. Preparation of Polymer Electrolyte Precursor Solutions

[0097] 0.0525g of filler and 0.35g of lithium salt were introduced into the polymer electrolyte matrix solution and mixed by stirring at room temperature to obtain a homogeneous polymer electrolyte precursor solution.

[0098] IV. Preparation of Polymer Electrolytes

[0099] The precursor solution was cast and dried under vacuum at 120°C to obtain a polymer electrolyte film.

[0100] V. Assembly of Solid-State Lithium-ion Batteries

[0101] After slicing the polymer electrolyte, it is assembled in sequence in an argon-filled glove box in the following order: positive electrode shell, lithium iron phosphate positive electrode, polymer electrolyte film, lithium sheet, gasket, spring sheet, and negative electrode shell, thus obtaining the practically applicable polymer electrolyte modified with potassium titanate.

[0102] Comparative Example 3:

[0103] I. Preparation of Potassium Titanate

[0104] First, mix 5 ml of titanate with 10 ml of anhydrous ethanol and stir magnetically to form a homogeneous solution. Then, add the complexing agent and continue stirring for 30 minutes until completely dissolved to obtain a transparent solution.

[0105] Dissolve 5g of KNO3 in 10ml of an ethanol / water mixture (volume ratio 1:1), stir until clear, and then slowly add the titanate precursor solution dropwise while maintaining vigorous stirring. After the addition is complete, adjust the pH to 4 with dilute nitric acid, and stir in a 60℃ water bath for 4 hours to obtain a uniform and transparent sol.

[0106] Pour the sol into a petri dish and let it stand at room temperature for 24 hours to form a wet gel. Dry at 120°C for 6 hours, then grind into a dry gel powder. Finally, spray at 2°C for 1 minute... -1 Heat to 400℃ and hold for 2 hours (to remove organic matter), then heat at 5℃ for 5 minutes. -1 The temperature was raised to 750℃ and held for 4 hours, then cooled in the furnace to obtain the final product, polymer electrolyte filler.

[0107] II. Preparation of polymer electrolyte matrix precursor solution

[0108] 0.05 g of polyacrylonitrile and 0.3 g of polyvinylidene fluoride were dissolved in 5 ml of organic solvent N,N-dimethylformamide and stirred evenly at room temperature to obtain a precursor solution of polymer electrolyte matrix.

[0109] III. Preparation of Polymer Electrolyte Precursor Solutions

[0110] 0.07 g of filler and 0.35 g of lithium salt were introduced into the polymer electrolyte matrix solution and mixed by stirring at room temperature to obtain a homogeneous polymer electrolyte precursor solution.

[0111] IV. Preparation of Polymer Electrolytes

[0112] The precursor solution was cast and dried under vacuum at 120°C to obtain a polymer electrolyte film.

[0113] V. Assembly of Solid-State Lithium-ion Batteries

[0114] After slicing the polymer electrolyte, it is assembled in sequence in an argon-filled glove box in the following order: positive electrode shell, lithium iron phosphate positive electrode, polymer electrolyte film, lithium sheet, gasket, spring sheet, and negative electrode shell, thus obtaining the practically applicable polymer electrolyte modified with potassium titanate.

[0115] The only difference between Comparative Examples 1 to 3 and the Examples is the content of potassium titanate filler. The potassium titanate synthesized in Examples to 3 were used as fillers to prepare solid-state lithium-ion battery polymer electrolytes, which were then tested as follows:

[0116] 1) X-ray diffraction (XRD) test. This patent utilizes an X'Pert PRO type X-ray diffractometer to analyze the effect of different preparation conditions on the crystal form of the filler. A copper target was selected as the X-ray source (Cu Kα radiation, wavelength...). The operating parameters were set to 45kV tube voltage and 40mA tube current. The diffraction data acquisition range was 10-35° (2θ), and the scanning speed was fixed at 5° / min. -1 In the experiment, the X-ray diffraction patterns of the samples were obtained by recording the diffraction peak intensities corresponding to different 2θ angles. The measured diffraction peak positions were matched with characteristic peaks in a standard PDF database to determine the type of crystal phase and its structural characteristics present in the samples.

[0117] 2) Scanning Electron Microscopy (SEM) Testing. A FEI Sirion 200 scanning electron microscope was used to characterize the surface morphology of the filler and solid electrolyte. To address the insulating properties of the polymer materials, the sample surface was sputter-coated with gold before testing. Testing conditions were set with accelerating voltages ranging from 0.2 to 30 kV, with the optimal resolution obtained at an accelerating voltage of 20 kV.

[0118] 3) Cyclic voltammetry (CV) test. The redox characteristics of the electrode material were investigated using cyclic voltammetry, and the tests were performed on a CHI760E workstation. The initial potential was set to 2.2V, the termination potential to 4.5V, and the voltammetry interval was 0.3mV / s. -1A single-cycle test was performed at a specific scan rate, and the current-potential response curve was recorded throughout the test. Cyclic voltammetry was used to evaluate the electrochemical stability of the material by analyzing the positions of the redox peaks and the current response.

[0119] 4) Electrochemical stability window testing. The electrochemical stability window is a key indicator for evaluating the electrochemical stability of solid-state electrolytes, and its voltage range directly determines the material's practical application potential in high-voltage lithium metal battery systems. To determine the electrochemical stability window of the solid-state electrolyte, a stainless steel / solid-state electrolyte / lithium metal three-electrode system was constructed. A CHI760E electrochemical workstation was used, with a voltage range of 0.002 V / s. -1 A constant scan rate was used to perform linear potential scans within the voltage range of -1V to 6V, and the current response curves were recorded. The ambient temperature was strictly controlled at 25±1℃ during the test to obtain the oxidation / reduction decomposition potential of the solid electrolyte, ultimately determining its electrochemical stability window.

[0120] 5) Lithium-ion transport number test. The lithium-ion transport number in the electrolyte quantitatively characterizes the contribution ratio of lithium ions to the total charge carriers, and its value directly reflects the selectivity of lithium-ion conduction. The lithium-ion transport number determination experiment uses a Li|SSE|Li symmetric battery system. The specific operation procedure includes: first, acquiring the initial impedance spectrum of the battery in the open circuit state; then applying a 10mV DC bias voltage for 4 hours and monitoring the current decay process; finally, recording the steady-state current value and combining it with the formula... The number of migrations was calculated;

[0121] 6) Charge-discharge test. A LAND CT2001A test system was used to assemble Li|electrolyte|LiFePO4 coin cells and conduct multi-rate charge-discharge tests within the operating voltage range of 2.6-4.0V. The system was used to examine the cycle stability and rate performance of the cells to verify the applicability of polymer electrolytes in practical battery systems.

[0122] Figure 25 The ionic conductivity of PAN / PVDF electrolyte under different raw material contents is as follows. The formulation content optimization of LiTFSI / PAN / PVDF solid electrolyte is as follows: (1) Fix the PVDF content, fix the mass fraction of LiTFSI to 60%, and optimize the PAN content. The optimal ratio of PVDF and PAN is determined by measuring the ionic conductivity of LiTFSI / PAN / PVDF electrolyte. (2) Fix the optimal ratio of PAN / PVDF, start optimizing the mass fraction of LiTFSI, and determine the optimal ratio of LiTFSI, PVDF, and PAN by measuring the ionic conductivity of LiTFSI / PAN / PVDF electrolyte. Figure 25Data analysis showed that in a system with a fixed LiTFSI content of 60%, the system exhibited optimal conductivity when the PAN addition was 17%. The measured ionic conductivity at this point was 2.73 × 10⁻⁶. -5 S cm -1 The performance was significantly improved compared to other formulations. With fixed PAN and PVDF additions, when the mass fraction of LiTFSI was 100%, the ionic conductivity reached 3.0 × 10⁻⁶. -5 S cm -1 The optimal composition of the polymer matrix for the electrolyte is: 0.30 g PVDF, 0.05 g PAN, and 0.35 g LiTFSI.

[0123] Figure 1 This figure shows the electrochemical stability window of a polymer electrolyte for solid-state lithium-ion batteries prepared using potassium titanate as a filler. A three-electrode system (Li|electrolyte|stainless steel) was used, and measurements were taken by linear sweep voltammetry (LSV) at a scan rate of 0.2 mV / s, at a test temperature of 25 ± 1 °C, and with humidity controlled below RH 5%. The electrochemical stability window is an important factor in evaluating the electrochemical performance of solid-state polymer electrolytes. The figure shows that the modified polymer electrolyte has a high electrochemical stability window of 4.62 V, indicating its suitability for high-voltage batteries.

[0124] Figure 2 This image shows the cyclic voltammograms of a lithium iron phosphate half-cell assembled using a polymer electrolyte prepared by a method for preparing a solid-state lithium-ion battery polymer electrolyte with potassium titanate as a filler. The figure shows that the current curve with a current density greater than zero represents the oxidation peak, while the current density less than zero represents the reduction peak. The reduction potential is 4.0 V, and the oxidation potential is 2.9 V. The potential difference between the two peaks is approximately an integer multiple of 0.0592 V. The lithium metal battery assembled using this solid-state polymer electrolyte membrane exhibits good reversibility, demonstrating excellent redox reversibility and cycle stability during the charge-discharge process.

[0125] Figure 3 This paper presents the impedance diagrams before and after polarization and the current-time variation curves during polarization of a lithium iron phosphate half-cell assembled with a polymer electrolyte prepared using potassium titanate as a filler, according to a method for preparing polymer electrolytes for solid-state lithium-ion batteries. A Li|electrolyte|LiFePO4 three-electrode system was used, and measurements were simultaneously obtained using potentiostatic polarization (10mV bias, 25±0.5℃) combined with electrochemical impedance spectroscopy (EIS, frequency range 0.1Hz-1 MHz). The data were fitted using an equivalent circuit model (R(QR)(QR)) in ZView software. The figures show that the initial current is 0.44 μA, the steady-state current is 0.34 μA, and the interfacial resistance starts from 55.4 Ωcm. 2 Increased to 68.8Ωcm 2Calculations showed a lithium-ion transport number of 0.8, indicating good lithium-ion transport efficiency. The -OH groups on the surface of the potassium titanate filler react with LiTFSI anions to form [TiO]···[TFSI]. + The coordination structure reduces anion migration and effectively prevents the formation of dendrites on the negative electrode surface.

[0126] Figure 4 This is an X-ray diffraction (XRD) pattern of the original potassium titanate used in a method for preparing a polymer electrolyte for solid-state lithium-ion batteries using potassium titanate as a filler. The pattern shows that the prepared filler conforms to the standard card, and characteristic diffraction peaks of potassium titanate are visible at 2θ of 8.5° and 29.8°, corresponding to the (200) and (003) and (020) crystal planes of potassium titanate, respectively. The grain size was calculated using the Scherrer formula based on the full width at half maximum (FWHM) of the (003) peak (FWHM = 0.12°).

[0127] (K = 0.89, β is the corrected broadening). (003) Spacing (Calculated value), matching Li + Transmission channel size requirements The 8.5° peak shape symmetry (FWHM = 0.15°) demonstrates that the sol-gel method reduces lattice strain by 30% compared to the solid-state method. The 29.8° peak position shift < 0.05° indicates that the sintering process did not induce K-vacancy defects.

[0128] Figure 5 This image shows a scanning electron microscope (SEM) image of potassium titanate used in a method for preparing polymer electrolytes for solid-state lithium-ion batteries using potassium titanate as a filler. The image clearly shows that potassium titanate exists in powder form, exhibiting typical powder particle structure characteristics. The particles are distributed independently with non-close packing (coverage ≈75%), with localized weak agglomeration (<5% area), but no hard agglomerates. Furthermore, the particle size uniformity is excellent, indicating that in the potassium titanate powder system, the vast majority of particles are similar in size, and the particle size difference is strictly controlled within the micrometer range. Compared with the traditional solid-state method, the sol-gel method improves particle size uniformity by 50%. The stepped sintering process (750℃×4h) suppresses abnormal grain growth (no coarse particles >3μm). This uniform particle size distribution is crucial for potassium titanate to maintain the electrochemical stability of the battery as a filler in the solid-state electrolyte system. Uniform particle size ensures consistent filler-polymer contact area, avoiding localized current concentration.

[0129] Figure 6This is a scanning electron microscope (SEM) image of a polymer electrolyte prepared using potassium titanate as a filler in a method for preparing polymer electrolytes for solid-state lithium-ion batteries. The image shows that the addition of potassium titanate alters the microstructure, increasing uniform porosity and creating ion channels, which improves the lithium-ion transport capacity of the solid-state electrolyte and enhances its electrochemical performance. Potassium titanate particles (~0.5-2 μm) act as pore-forming templates, generating three-dimensional interconnected channels during solvent evaporation. Hydrogen bonding between the -OH groups on the filler surface and the PAN cyano groups inhibits phase separation. Three-dimensional reconstruction reveals high porosity (compared to the unfilled sample); the ionic conductivity is increased to 1.69 × 10⁻⁶. -4 S / cm (EIS test, 25℃), compared to the matrix (2.6×10). -6 The S / cm ratio increased by 32 times. Lithium salts were adsorbed on the inner walls of the pores; the migration number t Li+ =0.80 (Bruce method), close to the level of liquid electrolyte.

[0130] Figure 7 Scanning electron microscope (SEM) images of polymer electrolyte control samples (without filler) for a method of preparing solid-state lithium-ion battery polymer electrolytes using potassium titanate as filler: (a) LiTFSI / PVDF; (b) LiTFSI / PAN / PVDF. The images show that the polymer electrolyte control samples have internal pores, but the pore density is lower than that of the polymer electrolyte membrane with potassium titanate filler.

[0131] Figure 8 This is an electrochemical stability window diagram of a polymer electrolyte control sample (without filler) prepared using potassium titanate as a filler in a method for preparing polymer electrolytes for solid-state lithium-ion batteries. The diagram shows that the electrolyte oxidation initiation potential of the polymer electrolyte matrix precursor is 3.883 V, and the reduction initiation potential is -0.759 V. Calculations of the redox potential difference yield a stability window of 4.64 V for the electrolyte.

[0132] Figure 9 This is a cyclic voltammogram of a polymer electrolyte control sample (without filler) prepared using potassium titanate as a filler in a method for preparing polymer electrolytes for solid-state lithium-ion batteries. The figure shows that after an initial scan at 4.5 V, the oxidation peak appears near 4.0 V, and the reduction peak is located around 2.8 V. The potential difference between the two peaks is approximately an integer multiple of 0.0592 V, indicating that this battery system possesses excellent electrochemical reversibility.

[0133] Figure 10This image shows the impedance diagrams before and after polarization of a Li|electrolyte|Li battery prepared using a method for preparing polymer electrolytes for solid-state lithium-ion batteries with potassium titanate as filler, and the current versus time curve during polarization. The initial current is 0.53 μA, the steady-state current is 0.41 μA, and the interface resistance starts from 60 Ω·cm. 2 Increased to 82Ω·cm 2 Calculations show that the lithium-ion transference number of this system reaches 0.73.

[0134] Figure 11 This is an elemental energy distribution surface plot (EDS-mapping) of potassium titanate used in a method for preparing polymer electrolytes for solid-state lithium-ion batteries using potassium titanate as a filler. It can be seen that Ti, O, K, and other elements are uniformly distributed on the potassium titanate filler. This uniform distribution of elements demonstrates the chemical composition and elemental distribution of the potassium titanate filler, further confirming the successful synthesis of the potassium titanate filler.

[0135] Figure 12 This is an electrochemical impedance spectroscopy (EIS) spectrum of a polymer electrolyte prepared using potassium titanate as a filler for solid-state lithium-ion batteries, used to test its conductivity. The highest ionic conductivity of 1.69 × 10⁻⁶ was observed when the potassium titanate content was 10%. -4 S / cm.

[0136] Figure 13 This is an electrochemical impedance spectroscopy (EIS) spectrum of a polymer electrolyte prepared using potassium titanate as a filler in a method for preparing polymer electrolytes for solid-state lithium-ion batteries. The EIS is shown in Comparative Example 1, where the potassium titanate content is 5%, and the conductivity of the polymer electrolyte is 7.0 × 10⁻⁶. -5 S / cm.

[0137] Figure 14 This is an electrochemical impedance spectroscopy (EIS) spectrum of a polymer electrolyte prepared using potassium titanate as a filler in a method for preparing polymer electrolytes for solid-state lithium-ion batteries. The EIS spectrum shows the conductivity of the polymer electrolyte prepared using potassium titanate as a filler in Comparative Example 2. The potassium titanate content in the figure is 15%, and the conductivity of the polymer electrolyte is 1.05 × 10⁻⁶. -5 S / cm.

[0138] Figure 15 This is an electrochemical impedance spectroscopy (EIS) spectrum of a polymer electrolyte prepared using potassium titanate as a filler in a method for preparing polymer electrolytes for solid-state lithium-ion batteries. The EIS is shown in Comparative Example 3, where the potassium titanate content is 20%, and the conductivity of the polymer electrolyte is 2.90 × 10⁻⁶. -5 S / cm.

[0139] Figure 16This is a voltage-specific capacity curve of a lithium iron phosphate half-cell assembled with a polymer electrolyte prepared using potassium titanate as a filler, as an example of a method for preparing polymer electrolytes for solid-state lithium-ion batteries, at 1C. The graph shows a stable charge-discharge curve with good stability, and an initial discharge specific capacity of 125 mAh g⁻¹. -1 After 100 cycles, the discharge specific capacity is still 100 mAh g. -1 .

[0140] Figure 17 This is a voltage-specific capacity curve of a lithium iron phosphate half-cell assembled with the polymer electrolyte prepared in Comparative Example 1, using potassium titanate as a filler, as a method for preparing polymer electrolytes for solid-state lithium-ion batteries. It can be seen that the initial discharge specific capacity is 98 mAh g. -1 After 100 cycles, the discharge specific capacity is still 80 mAh g. -1 The charge-discharge platform is stable and the capacity retention rate is high, but the specific capacity of this battery system is lower than that of the example.

[0141] Figure 18 This is a voltage-specific capacity curve of a lithium iron phosphate half-cell assembled with the polymer electrolyte prepared in Comparative Example 2, which is a method for preparing polymer electrolytes for solid-state lithium-ion batteries using potassium titanate as filler, at 1C. The graph shows that the initial discharge specific capacity of the polymer electrolyte is 116 mAh g⁻¹. -1 After 100 cycles, the discharge specific capacity is 59 mAh g. -1 The capacity retention rate is low, and the battery specific capacity is lower than that of the previous embodiment.

[0142] Figure 19 This is the electrochemical impedance spectroscopy (EIS) of an uncycled lithium iron phosphate half-cell assembled using a polymer electrolyte prepared by a method for preparing solid-state lithium-ion battery polymer electrolytes with potassium titanate as filler. The figure shows that the impedance of the solid electrolyte interfacial film after battery assembly is 1193 Ohm cm⁻¹. 2 It has relatively low impedance.

[0143] Figure 20 This is the electrochemical impedance spectroscopy (EIS) of a non-cycled lithium iron phosphate half-cell, a comparative sample (without filler) of a method for preparing a solid-state lithium-ion battery polymer electrolyte using potassium titanate as a filler. The figure shows that the interfacial impedance of the solid electrolyte after assembling the battery with the precursor electrolyte is 1402 Ohm / cm². 2 It has a relatively high impedance.

[0144] Figure 21This is a constant-current polarization diagram of a lithium-ion symmetric battery assembled using a method for preparing a polymer electrolyte for solid-state lithium-ion batteries with potassium titanate as the filler. The diagram shows that the modified polymer electrolyte exhibits excellent cycle stability at room temperature. Its stable voltage curve and effective suppression of lithium dendrite growth ensure a long cycle life.

[0145] Figure 22 This image shows the specific capacity-efficiency curve of a lithium iron phosphate half-cell assembled using a polymer electrolyte prepared by a method for preparing polymer electrolytes for solid-state lithium-ion batteries with potassium titanate as filler, under 1C cycling conditions. The initial discharge specific capacity of the assembled lithium iron phosphate half-cell is 125 mAh g. -1 After 100 cycles, the discharge specific capacity is 100 mAh g. -1 The coulombic efficiency remained at 99%, and the capacity retention rate was 80%, which confirms the stability of the battery after the addition of potassium titanate.

[0146] Figure 23 This is a specific capacity-efficiency diagram of a lithium iron phosphate half-cell assembled using a method for preparing polymer electrolytes for solid-state lithium-ion batteries with potassium titanate as filler, under 1C cycling conditions. The initial discharge specific capacity of the assembled lithium iron phosphate half-cell is 98 mAh·g. -1 The discharge specific capacity decreased to 80 mAh·g after 100 cycles. -1 Coulomb efficiency remains at 98%.

[0147] Figure 24 This is a specific capacity-efficiency diagram of a lithium iron phosphate half-cell assembled using a polymer electrolyte prepared by a method for preparing polymer electrolytes for solid-state lithium-ion batteries with potassium titanate as filler, under 1C cycling conditions. The initial discharge specific capacity of the assembled lithium iron phosphate half-cell is 116 mAh·g. -1 The discharge specific capacity decreased to 59 mAh·g after 100 cycles. -1 The Coulomb efficiency is 99%.

[0148] Figure 25 The ionic conductivity of the PAN / PVDF electrolyte is shown for different raw material contents. The optimal composition of the polymer matrix of the electrolyte is: 0.30g PVDF, 0.05g PAN, and 0.35g LiTFSI. This lays the foundation for the compatibility matrix of the filler potassium titanate.

[0149] In summary, this invention provides a solid-state lithium-ion battery polymer electrolyte prepared with potassium titanate as a filler. The excellent ionic conductivity of potassium titanate synergistically enhances the PAN / PVDF matrix. The innovation of this invention lies in the fact that the addition of potassium titanate improves mechanical strength, resists dendrite formation, provides additional fast lithium-ion transport channels, enhances thermal stability, improves the interface, and promotes uniform lithium deposition. This multifunctional synergistic effect ultimately makes the PAN / PVDF / potassium titanate composite material superior to pure polymers or simple blends in terms of ionic conductivity, mechanical strength, thermal stability, and interfacial stability, thus exhibiting superior electrochemical performance. The electrolyte achieves an ionic conductivity of 1.69 × 10⁻⁶. -4 The electrochemical stability window extends to 4.62 V, with a S / cm. After 100 cycles at 1C, the discharge specific capacity remains stable at 100 mAh g⁻¹. -1 This optimization not only comprehensively improves the overall performance of the electrolyte, but also significantly enhances its interfacial stability with the electrode, thus pointing to a highly feasible technical path for the development of next-generation solid electrolytes.

Claims

1. A method for preparing a solid-state lithium-ion battery polymer electrolyte using potassium titanate as a filler, characterized in that... A method for preparing a solid-state lithium-ion battery polymer electrolyte using potassium titanate as a filler is carried out according to the following steps: I. Preparation of Potassium Titanate The titanate precursor and alcohol solvent are mixed at a volume ratio of 1:5 to 1:

10. After forming a homogeneous solution by magnetic stirring, citric acid with a mass of 0.5 times that of the alcohol solvent is added as a complexing agent. Stirring is continued for 20-60 minutes until completely dissolved. Dissolve the potassium source in an alcohol / water mixture with a mass ratio of 1:1 to 1:10, stir until clear, and then add it dropwise to the titanate precursor solution. Adjust the pH value to 2-5 with dilute nitric acid, and stir in a water bath at 40-80℃ for 2-8 hours to obtain a sol. The sol was allowed to stand at room temperature for 12-48 hours to form a wet gel, then dried at 100-150℃ for 2-8 hours and milled, with each milling cycle occurring at 2℃ min. -1 Heat to 300-500℃ and hold for 1-6 hours to remove organic matter, then heat at 5℃ for 5 minutes. -1 Heat to 650-900℃ and hold for 2-8 hours, then cool with the furnace to obtain potassium titanate (K2Ti6O). 13 )filler; II. Preparation of polymer electrolyte matrix precursor solution Polyacrylonitrile and polyvinylidene fluoride were dissolved in N,N-dimethylformamide at a mass ratio of 1:1 to 1:10 and stirred at room temperature until dissolved. III. Preparation of Polymer Electrolyte Precursor Solutions Add 1-20% by weight of potassium titanate filler and 5-100% by weight of lithium salt to the solution in step two, and stir to mix evenly; IV. Preparation of Polymer Electrolytes The precursor solution was poured into a mold and vacuum dried at 60-140℃ to form a film. V. Assembly of Solid-State Lithium-ion Batteries The thin film, along with a lithium iron phosphate cathode and lithium sheets, were assembled into a solid-state battery in an argon-filled glove box.

2. The method for preparing a solid-state lithium-ion battery polymer electrolyte using potassium titanate as a filler according to claim 1, characterized in that, The potassium source mentioned in step one is selected from at least one of potassium nitrate and potassium acetate.

3. The method for preparing a solid-state lithium-ion battery polymer electrolyte using potassium titanate as a filler according to claim 1, characterized in that, In step one, the mass ratio of potassium source to alcohol / water mixed solvent is 1:1-1:

2.

4. The method for preparing a solid-state lithium-ion battery polymer electrolyte using potassium titanate as a filler according to claim 1, characterized in that, In step one, the alcohol solvent is ethanol or isopropanol.

5. The method for preparing a solid-state lithium-ion battery polymer electrolyte using potassium titanate as a filler according to claim 1, characterized in that, In step three, the lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium hexafluorophosphate.

6. A solid-state lithium-ion battery, characterized in that: The polymer electrolyte film prepared by the method of claim 1, which simultaneously includes all the features of claims 2-4, is used as the electrolyte component.

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