Modified solid electrolyte particles and their preparation methods, solid electrolyte membranes and solid batteries

Abstract

This invention relates to the field of battery technology, and in particular to a modified solid electrolyte particle and its preparation method, a solid electrolyte membrane, and a solid-state battery. The modified solid electrolyte particle comprises a solid electrolyte, a polydopamine coating disposed on the surface of the solid electrolyte, and a metalloid element (MOF) disposed on the surface of the polydopamine coating. This invention significantly improves the ionic conductivity and lithium-ion transference number of the composite solid electrolyte and reduces the electrode / electrolyte interface impedance through the synergistic effect of PDA surface modification, MOF interface regulation, introduction of crown ether functionalized single-ion conductors, and gradient structure design. Simultaneously, the three-dimensional fibrous skeleton of the base film enhances the mechanical strength of the material and effectively inhibits lithium dendrite growth, thereby achieving excellent cycle stability and electrochemical stability, making it suitable for high-energy-density solid-state lithium batteries.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a modified solid electrolyte particle and its preparation method, a solid electrolyte membrane, and a solid battery. Background Technology

[0002] With the development of high-energy-density energy storage technology, solid-state lithium batteries have gradually become an important development direction for next-generation energy storage systems due to their high safety, high energy density, and good cycle stability. Among these, solid-state electrolytes, as key core materials, directly determine the overall battery performance through their ion transport performance and interfacial stability. Currently, solid-state electrolytes mainly include two categories: inorganic solid-state electrolytes and polymer solid-state electrolytes. Although inorganic solid-state electrolytes (such as garnet oxide LLZTO) have high room-temperature ionic conductivity and excellent electrochemical stability, their inherent rigidity is relatively high, resulting in poor contact with the electrode interface and high interfacial impedance. In practical applications, they are prone to interfacial voids, affecting the continuity of ion transport; their processability is also poor, hindering large-scale production. Meanwhile, polymer solid-state electrolytes possess good flexibility and interfacial contact performance, but they also suffer from low room-temperature ionic conductivity, poor anion-cation co-migration, low lithium-ion transference number, and insufficient stability under high voltage and lithium metal anode conditions. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings and defects of the prior art and to provide a modified solid electrolyte particle and its preparation method, a solid electrolyte membrane and a solid battery.

[0004] To achieve the above objectives, this application adopts the following solution: A modified solid electrolyte particle includes a solid electrolyte, a polydopamine coating disposed on the surface of the solid electrolyte, and a MOF disposed on the surface of the polydopamine coating.

[0005] The solid electrolyte includes LLZTO; the MOF includes at least one of ZIF-8, ZIF-67, UiO-66, MIL-101(Cr), and MOF-74.

[0006] The present invention also includes a method for preparing the modified solid electrolyte particles, characterized by comprising the following steps: 1) performing interface modification treatment on the solid electrolyte particles; taking solid electrolyte and dispersing it in methanol, simultaneously adding Tris buffer to the system and adjusting the solution pH, then adding dopamine hydrochloride, stirring the reaction under air or oxygen conditions, so that dopamine undergoes self-polymerization and forms a polydopamine PDA coating on the surface of the solid electrolyte particles to obtain PDA@LLZTO; 2) performing MOF in-situ growth coating on PDA@LLZTO; dispersing PDA@LLZTO in methanol and sonicating to obtain a uniform dispersion system, then adding MOF precursor, and MOF grows in-situ on the particle surface to form a coating layer to obtain MOF@PDA@LLZTO.

[0007] The mass ratio of the solid electrolyte to dopamine hydrochloride is 5:(0.06-0.24); preferably 5:0.12. Preferably, the molar ratio of PDA@LLZTO to MOF is 1g:(0.0005-0.0015)mol; more preferably, it is 1g:0.001mol.

[0008] The present invention also includes a solid electrolyte membrane, comprising a base membrane and an electrolyte layer disposed on the surface of the base membrane; the electrolyte layer comprises a first electrolyte layer, a second electrolyte layer and a third electrolyte layer from near the base membrane to far away from the base membrane; the base membrane and the electrolyte layer contain the modified solid electrolyte particles and the crown ether functionalized single-ion conductor polymer.

[0009] The base membrane is prepared by adding modified solid electrolyte particles to a polyamic acid (PAA) solution, spinning to obtain a fiber membrane, and then subjecting the fiber membrane to thermal imidization treatment to obtain the base membrane; preferably, the mass ratio of modified solid electrolyte particles to polyamic acid (PAA) is (5-8):(2-5); more preferably, it is 7:3.

[0010] The crown ether functionalized single-ion conductor polymers include polyacrylic acid and crown ethers modified on the polyacrylic acid; Preferably, the crown ether functionalized single-ion conductor polymer is prepared by dissolving polyacrylic acid in DMF solution, adding EDC and DMAP to activate the carboxyl groups, then adding 12-crown-4, and reacting at room temperature to graft the crown ether groups onto the polymer backbone. Preferably, the mass ratio of polyacrylic acid to 12-crown-4 is 5:(0.225-0.9); more preferably, it is 5:0.45.

[0011] The content of modified solid electrolyte particles in the first electrolyte layer, the second electrolyte layer, and the third electrolyte layer decreases sequentially, while the content of crown ether functionalized single-ion conductor polymer increases sequentially. Preferably, the thickness ratio of the first electrolyte layer, the second electrolyte layer, and the third electrolyte layer is (5-10):(20-30):(5-10).

[0012] The first electrolyte layer comprises MOF@PDA@LLZTO, crown ether functionalized single-ion conductor polymer, LiTFSI, and SiO2; preferably, the mass ratio of MOF@PDA@LLZTO, crown ether functionalized single-ion conductor polymer, LiTFSI, and SiO2 is (20-50):(30-60):(15-20):5; more preferably, it is 40:40:15:5; The second electrolyte layer comprises MOF@PDA@LLZTO, crown ether functionalized single-ion conductor, LiTFSI, and SiO2; preferably, the mass ratio of MOF@PDA@LLZTO, crown ether functionalized single-ion conductor polymer, LiTFSI, and SiO2 is (10-25):(55-60):(15-25)::5; more preferably, it is 10:60:25:5; The third electrolyte layer comprises MOF@PDA@LLZTO, crown ether functionalized single-ion conductor, LiTFSI, LiNO3, and FEC; the mass ratio of MOF@PDA@LLZTO, crown ether functionalized single-ion conductor, LiTFSI, LiNO3, and FEC is (5-15):(60-70):(10-15):5:5; preferably 5:65:20:5:5.

[0013] The present invention also includes a solid-state battery, comprising a positive electrode, the aforementioned solid electrolyte membrane, and a negative electrode, wherein the base membrane is disposed near the positive electrode side; and the electrolyte layer is disposed near the negative electrode side.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention significantly improves the ionic conductivity and lithium-ion transference number of the composite solid electrolyte and reduces the electrode / electrolyte interface impedance through the synergistic effect of PDA surface modification, MOF interface regulation, introduction of crown ether functionalized single-ion conductors, and gradient structure design. At the same time, the three-dimensional fiber skeleton of the base film enhances the mechanical strength of the material and effectively inhibits lithium dendrite growth, thereby achieving excellent cycle stability and electrochemical stability, making it suitable for high-energy-density solid-state lithium batteries. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0016] Example 1: 1. Preparation of MOF@PDA@LLZTO composite particles 1) Interface modification of solid electrolyte particles. 5 g of LLZTO powder was dispersed in 60 mL of methanol solution. Simultaneously, 0.072 g of Tris buffer was added to the system, and the pH was adjusted to approximately 8.5. Then, 0.12 g of dopamine hydrochloride was added. The mixture was stirred under air or oxygen conditions for 12 h to allow dopamine to self-polymerize and form a polydopamine (PDA) coating on the surface of the LLZTO particles. After the reaction, the solid product was separated by centrifugation and washed three times with methanol to remove unreacted substances. Subsequently, it was vacuum dried at 60 °C for 12 h to obtain PDA-modified solid electrolyte particles (PDA@LLZTO).

[0017] 2) MOF in-situ growth and coating of PDA@LLZTO particles. 1.0 g of PDA@LLZTO was dispersed in 50 mL of methanol and sonicated for 30 min to obtain a uniform dispersion. Then, 0.30 g of Zn(NO3)2·6H2O was added and stirred for 30 min to allow metal ions to fully adsorb onto the PDA surface. Next, 0.66 g of 2-methylimidazole was dissolved in the remaining methanol and slowly added to the reaction system. The reaction was carried out at room temperature (20-30℃) for 6 h, allowing ZIF-8 to grow in situ on the particle surface to form a coating layer. After the reaction was complete, the product was collected by centrifugation, washed three times with methanol, and finally dried under vacuum to obtain MOF@PDA@LLZTO composite particles.

[0018] 2. Preparation of the base membrane: The MOF@PDA@LLZTO composite particles obtained in Example 1 were added to a 10 wt% polyamic acid (PAA) solution at a MOF@PDA@LLZTO:polyamic acid (PAA) ratio of 7:3. The solution was magnetically stirred at room temperature for 12 h to form a uniform spinning solution. The solution was then placed in an electrospinning apparatus and spun under conditions of 18 kV voltage, a feed rate of 0.5 mL / h, and a receiving distance of 15 cm to obtain a fiber membrane. Subsequently, the fiber membrane was subjected to thermal imidization treatment at 200℃ for 2 h to convert PAA into polyimide (PI), thereby obtaining a nanofiber framework with a three-dimensional continuous network structure.

[0019] 3. Preparation of crown ether functionalized single-ion conductor polymer: 5 g of polyacrylic acid was dissolved in 50 mL of DMF solution. 1.15 g of EDC and 0.05 g of DMAP were added to activate the carboxyl groups. Subsequently, 0.45 g of 12-crown-4 was added, and the reaction was carried out at room temperature for 24 h to graft the crown ether groups onto the polymer backbone. After the reaction was completed, unreacted substances were removed by precipitation and washing, and the polymer was dried under vacuum to obtain the crown ether functionalized single-ion conductor polymer.

[0020] 4. Preparation of solid electrolyte membrane: A gradient structure composite solid electrolyte membrane was constructed using a layered coating method.

[0021] First, a positive electrode slurry (first electrolyte layer slurry) was prepared, in which the mass fractions of MOF@PDA@LLZTO, crown ether functionalized single-ion conductor polymer, LiTFSI and SiO2 were 40 wt%, 40 wt%, 15 wt% and 5 wt%, respectively. DMF solvent with a mass of 3 times the total solids was added. After stirring thoroughly to form a uniform slurry, a first electrolyte layer of about 10 μm thickness was formed by coating on the surface of the three-dimensional fiber skeleton and drying at 60°C for 30 min.

[0022] Subsequently, an intermediate layer slurry (second electrolyte layer slurry) was prepared, in which the mass fractions of MOF@PDA@LLZTO, crown ether functionalized single ion conductor, LiTFSI, and SiO2 were 10 wt%, 60 wt%, 25 wt%, and 5 wt%, respectively. The second electrolyte layer with a thickness of about 20 μm was then formed by scraping on the surface of the first layer and dried at 60 °C for 30 min.

[0023] Finally, the negative electrode side slurry (third electrolyte layer slurry) is prepared, in which the mass fractions of MOF@PDA@LLZTO, crown ether functionalized single ion conductor, LiTFSI, FEC, LiNO3 and are 5 wt%, 65 wt%, 20 wt%, 5 wt%, and 5 wt%, respectively, and the third electrolyte layer with a thickness of about 10 μm is formed by scraping.

[0024] After all coatings were completed, the membrane was vacuum dried at 80°C for 12 h to obtain a composite solid electrolyte membrane with a distinct gradient structure.

[0025] Example 2: Preparation of MOF@PDA@LLZTO composite particles. The amount of MOF was increased to 0.45g, Zn(NO3)2·6H2O was increased to 1.0g, and the remaining steps were the same as those in Example 1.

[0026] Example 3: Preparation of MOF@PDA@LLZTO composite particles. PDA and dopamine were increased to 0.24g, and the remaining steps were the same as those in Example 1.

[0027] Example 4: Preparation of MOF@PDA@LLZTO composite particles. The amount of MOF was reduced to 0.15g and the amount of Zn(NO3)2·6H2O was reduced to 0.33g. The remaining steps were the same as those in Example 1.

[0028] Example 5: Preparation of MOF@PDA@LLZTO composite particles with reduced PDA: In Example 7, dopamine was reduced to 0.06g, and the remaining steps were the same as in Example 1.

[0029] Example 6: Preparation of MOF@PDA@LLZTO composite particles with ZIF-67 replacement: replace Zn(NO3)2·6H2O with Co(NO3)2·6H2O, replace MOF with ZIF-67, and keep the remaining steps the same as in Example 1.

[0030] Example 7: Preparation of MOF@PDA@LLZTO composite particles with UiO-66 as a substitute: In Example 16, 1.0 g of PDA@LLZTO was dispersed in 50 ml of DMF (ultrasonicated for 30 min), and 0.25 g of ZrCl4 was added and stirred for 30 min. 0.2 g of terephthalic acid ligand was added, and the mixture was solvothermal reacted at 120 °C for 12 h. After cooling, the mixture was centrifuged, washed alternately with DMF and methanol, and vacuum dried (80 °C, 12 h). The MOF was replaced with UiO-66, and the remaining steps were consistent with those in Example 1.

[0031] Example 8: Preparation of MOF@PDA@LLZTO composite particles with MIL-101(Cr) as a substitute: 1.0 g PDA@LLZTO was dispersed in 50 ml DMF or deionized water (ultrasonicated for 30 min), and 0.4 g Cr(NO3)3·9H2O was added and stirred for 30 min. 0.2 g terephthalic acid ligand was added, and the mixture was solvothermal reacted at 180 °C for 10 h. After cooling, the mixture was centrifuged, washed alternately with deionized water and ethanol, and vacuum dried (80 °C, 12 h). MOF was replaced with MIL-101(Cr), and the remaining steps were the same as in Example 1.

[0032] Example 9: Preparation of MOF@PDA@LLZTO composite particles (replaced with MOF-74): 1.0 g PDA@LLZTO was dispersed in 50 ml DMF or ethanol (ultrasonicated for 30 min), and 0.3 g Zn(NO3)2·6H2O was added and stirred for 30 min. 0.25 g p-2,5-hydroxyterephthalic acid ligand was added, and the mixture was solvothermal reacted at 120 °C for 10 h. After cooling, the mixture was centrifuged, washed alternately with DMF and ethanol, and vacuum dried (80 °C, 12 h). MOF was replaced with MOF-74, and the remaining steps were the same as in Example 1.

[0033] Example 10: The preparation of the base film involves adding a framework, with MOF@PDA@LLZTO:PAA = 8:2, and the remaining steps are consistent with those in Example 1.

[0034] Example 11: The preparation of the base film reduces the skeleton, MOF@PDA@LLZTO:PAA=5:5, and the remaining steps are consistent with those in Example 1.

[0035] Example 12: Preparation of crown ether functionalized single-ion conductor polymer, with 12-crown-4 increased to 0.9 g, and the remaining steps consistent with those in Example 1. Example 13: Preparation of crown ether functionalized single-ion conductor polymer, 12-crown-4 reduced to 0.225 g, the remaining steps are consistent with those in Example 1.

[0036] Example 14: Preparation of solid electrolyte membrane, changing the concentration of the positive electrode side slurry (first electrolyte layer slurry): the proportion of MOF@PDA@LLZTO near the positive electrode side layer was reduced to 20wt%, the crown ether functionalized single ion conductor polymer was increased to 60wt%, and the remaining steps were consistent with those in Example 1.

[0037] Example 15: Preparation of solid electrolyte membrane. The thickness was changed. The thickness of the first electrolyte layer was 5 μm, the thickness of the second electrolyte layer was 30 μm, the thickness of the third electrolyte layer was 5 μm, and the total thickness remained unchanged at 40 μm. The remaining steps were the same as those in Example 1.

[0038] Example 16: Preparation of a solid electrolyte membrane. The gradient between the positive and negative electrodes was altered. The first electrolyte layer consisted of MOF@PDA@LLZTO, crown ether functionalized single-ion conductor polymer, LiTFSI, and SiO2, with mass fractions of 30 wt%, 45 wt%, 20 wt%, and 5 wt%, respectively. The second electrolyte layer consists of MOF@PDA@LLZTO, crown ether-functionalized single-ion conductor polymer, LiTFSI, and SiO2, with mass fractions of 20 wt%, 55 wt%, 20 wt%, and 5 wt%, respectively. The third electrolyte layer consists of MOF@PDA@LLZTO, crown ether functionalized single-ion conductor polymer, LiTFSI, LiNO3 and FEC with mass fractions of 15 wt%, 60 wt%, 15 wt%, 5 wt% and 5 wt%, respectively, and the remaining steps are consistent with those in Example 1.

[0039] Example 17: Preparation of a solid electrolyte membrane with varying positive and negative electrode gradients. The first electrolyte layer consists of MOF@PDA@LLZTO, crown ether functionalized single-ion conductor polymer, LiTFSI, and SiO2 with mass fractions of 50 wt%, 30 wt%, 15 wt%, and 5 wt%, respectively. The second electrolyte layer consists of MOF@PDA@LLZTO, crown ether functionalized single-ion conductor polymer, LiTFSI, and SiO2 with mass fractions of 25 wt%, 55 wt%, 15 wt%, and 5 wt%, respectively. The third electrolyte layer consists of MOF@PDA@LLZTO, crown ether functionalized single-ion conductor polymer, LiTFSI, LiNO3, and FEC with mass fractions of 10 wt%, 70 wt%, 10 wt%, 5 wt%, and 5 wt%, respectively. The remaining steps are consistent with those in Example 1.

[0040] Example 18: Preparation of solid electrolyte membrane with positive and negative electrode sides (first electrolyte layer and third electrolyte layer) interchanged; Comparative Example 1: (Without PDA Interface Modification) In this comparative example, the remaining steps were the same as in Example 1, except that no PDA surface modification was performed. Specifically, the original LLZTO powder was used directly for MOF in-situ growth, that is, LLZTO was dispersed in methanol and then Zn salt and organic ligands were directly added to react and obtain MOF@LLZTO composite particles without introducing a PDA interface layer. Subsequently, the obtained particles were used for three-dimensional framework construction and gradient electrolyte membrane preparation, and the remaining steps were consistent with those in Example 1.

[0041] Comparative Example 2: (No MOF layer) In this comparative example, the remaining preparation steps are basically the same as in Example 1, except that MOF coating treatment was not performed, i.e., the in-situ MOF growth in step 2 was not performed. Specifically, LLZTO powder was modified with PDA to obtain PDA@LLZTO particles, which were directly used for subsequent three-dimensional fiber skeleton construction and electrolyte membrane preparation. In the gradient structure, the original MOF@PDA@LLZTO composite particles in each layer were replaced with an equal mass of PDA@LLZTO particles, while the remaining components and proportions remained unchanged, and the remaining steps were consistent with those in Example 1.

[0042] Comparative Example 3: (Unfunctionalized without crown ether) In this comparative example, the remaining steps are the same as in Example 1, except that crown ether functionalized single-ion conductor polymers are not used. Specifically, the single-ion conductor obtained in step 4 is replaced with an unfunctionalized ordinary polymer (polyacrylic acid), while keeping the proportions of other components unchanged. In each layer of the gradient structure, this ordinary polymer is used as the matrix material, and the remaining steps are consistent with those in Example 1.

[0043] Comparative Example 4: (Gradient-free structure) In this comparative example, the remaining preparation steps are the same as in Example 1, except that the electrolyte membrane does not adopt a layered structure, but a uniform structure. Specifically, MOF@PDA@LLZTO, single-ion conductor polymer, LiTFSI, and inorganic additive SiO2 are mixed according to the average ratio of the three layers in Example 1 to form a uniform slurry, wherein the mass fraction of each component is: MOF@PDA@LLZTO about 18 wt%, single-ion conductor about 55 wt%, LiTFSI about 22 wt%, and SiO2 about 5 wt%. This slurry is coated onto the surface of the three-dimensional fiber skeleton in one go, controlling the film thickness to be about 40 μm, and dried under the same conditions to obtain a gradient-free composite solid electrolyte membrane. The remaining steps are consistent with the steps in Example 1.

[0044] Example 19: Battery fabrication, a solid-state lithium battery, comprising a positive electrode, a solid electrolyte membrane and a negative electrode as described in the examples and comparative examples, and may also include a conventional packaging structure. The positive electrode active material is a conventional commercial electrode material, including one or more of lithium cobalt oxide (LCO), lithium iron phosphate (LFP), and lithium nickel cobalt manganese oxide (NCM). The positive electrode active material, super P, PVDF, and LiTFSI are mixed in N-methylpyrrolidone (NMP) at a mass ratio of 80:10:8:2. After uniform mixing, the slurry is coated onto aluminum foil and dried in a vacuum oven at 80 °C for 24 h. The dried electrode sheet was cut into 10 mm diameter discs and stored for later use. The negative electrode was one or more of lithium metal or lithium metal alloy, which are conventional commercial electrode materials. To achieve good interfacial contact and ion conduction between the electrolyte and the composite electrode sheet, 1.0 μL·mAh-1 electrolyte was dropped onto the surface of the composite electrode (1 M LiTFSI EC / DEC=1:1, v / v, LFP; 1.2M LiPF6 EC / EMC=3:7, v / v, NCM).

[0045] Composite solid electrolyte membrane and battery testing: a. Ionic conductivity testing: A clean, smooth stainless steel sheet (SS) was used as the blocking electrode. The electrolyte was sandwiched between two SS sheets and sealed within a coin cell. The assembled cell was placed in a 60 °C oven for 1 h to ensure adequate interface contact. After cooling to room temperature, the cell was connected to an electrochemical workstation using a coin cell clamp, and AC impedance spectra were recorded at different temperatures. The frequency range was 0.1 Hz to 1 MHz, and the AC amplitude was 10 mV. The ionic conductivity of the corresponding electrolyte was calculated.

[0046] b. Electrolyte-Li Electrode Interfacial Voltage Window (LSV) Test: A clean, smooth stainless steel sheet (SS) was used as the blocking electrode. The electrolyte was sandwiched between two SSs and sealed within a coin cell. The assembled cell was placed in a 60°C oven for 1 hour to ensure adequate interfacial contact. After cooling to room temperature, the cell was connected to an electrochemical workstation using a coin cell clamp. Voltage was measured at 0.5 mV s in the 0-6 V range. -1 Linear scan voltammetry was performed at the scan rate, and the electrochemical stability window was determined by the potential corresponding to a significant increase in current.

[0047] c. Electrolyte-Li Electrode Interface Stability Test: The electrolyte was sandwiched between two Li electrodes and sealed in a coin cell casing to assemble a Li||Li battery. The assembled battery was placed in a 60 ℃ oven for 1 h to ensure full interface contact. After cooling to room temperature, the battery was placed in a 25 ℃ oven, and the symmetrical battery was connected to the battery testing system. The Li electrode interface stability was tested using a current density of 0.1 mA·cm⁻² at 25 ℃.

[0048] d. Solid-state battery assembly and testing: After assembly, the batteries were allowed to stand for approximately 6 hours, then placed in a 60°C oven for 1 hour to ensure sufficient interface contact. After cooling to room temperature, charge-discharge tests were performed using a battery testing system. Capacity testing was conducted at 0.1C rate with a voltage window of 2.7-4.2 V, and cycle testing was conducted at 0.5C rate with a voltage window of 2.7-4.2 V at a test temperature of 25°C.

[0049] The test results are shown in Table 1: Table 1

[0050]

[0051] The following points can be observed from Table 1: (1) In terms of ion conduction, the ion conductivity of Example 1 reaches 1.25 × 10⁻⁶.-3 S·cm -1 It is significantly higher than that of systems without interface modification or without MOF (less than 7.5 × 10⁻⁶). -4 S·cm -1 This indicates that the composite filler structure effectively constructs a continuous ion transport channel; (2) Regarding lithium-ion migration behavior, increasing or decreasing the crown ether structure (Examples 12 and 13), Li + The significant decrease in conductivity indicates that too much steric hindrance in the crown ether structure will hinder ion transport, while too little will result in insufficient ion channels. (3) In terms of interface stability, the ionic conductivity of Example 1 is better than that of Comparative Example 1, indicating that the PDA interface layer significantly improves the interface contact. (4) In terms of cycle stability, the system of Example 1 can cycle stably for more than 1200 h in Li|Li symmetric battery, while the comparative system is generally less than 700 h, indicating that the present invention effectively suppresses lithium dendrite growth; (5) In terms of actual battery performance, when using NCM811 cathode, Example 1 achieved a capacity retention rate of 91% after 200 cycles, which is significantly better than the comparative example (about 68-78%), demonstrating excellent interface compatibility and cycle stability. (6) Further, through Examples 14-18, the control of the gradient structure is illustrated. The gradient structure of Example 1 better matches the positive and negative poles, which helps to reduce the interface impedance and improve the cycle life, while the gradient reverse structure significantly reduces the performance, further proving the importance of the gradient design direction.

[0052] (7) The MOF material in this invention is not limited to ZIF-8. By selecting different metal centers (such as Zn, Co, Zr, Cr, etc.) and different organic ligand structures (imidazolium, carboxylic acid, etc.), a porous structure layer can be constructed in situ on the surface of PDA-modified solid electrolyte particles, and the ion transport and interface stability can be effectively controlled. This shows that the technical solution of this invention has good universality and scalability.

[0053] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of the equivalents of the claims be included within the invention.

[0054] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A modified solid electrolyte particle, characterized in that, It includes a solid electrolyte, a polydopamine coating disposed on the surface of the solid electrolyte, and a MOF disposed on the surface of the polydopamine coating.

2. The modified solid electrolyte particles according to claim 1, characterized in that, The solid electrolyte includes LLZTO; the MOF includes at least one of ZIF-8, ZIF-67, UiO-66, MIL-101(Cr), and MOF-74.

3. A method for preparing the modified solid electrolyte particles according to any one of claims 1-2, characterized in that, The process includes the following steps: 1) Interfacial modification of solid electrolyte particles; solid electrolyte is dispersed in methanol, Tris buffer is added to the system and the pH of the solution is adjusted, then dopamine hydrochloride is added, and the reaction is stirred under air or oxygen conditions to allow dopamine to self-polymerize and form a polydopamine PDA coating on the surface of the solid electrolyte particles to obtain PDA@LLZTO; 2) MOF in-situ growth coating of PDA@LLZTO; PDA@LLZTO is dispersed in methanol and sonicated to obtain a uniform dispersion system, then MOF precursor is added, and MOF grows in situ on the particle surface to form a coating layer to obtain MOF@PDA@LLZTO.

4. The method for preparing modified solid electrolyte particles according to claim 3, characterized in that, The mass ratio of the solid electrolyte to dopamine hydrochloride is 5:(0.06-0.24); preferably 5:0.

12. Preferably, the molar ratio of PDA@LLZTO to MOF is 1g:(0.0005-0.0015)mol; more preferably, it is 1g:0.001mol.

5. A solid electrolyte membrane, characterized in that, It includes a base film and an electrolyte layer disposed on the surface of the base film; the electrolyte layer includes a first electrolyte layer, a second electrolyte layer and a third electrolyte layer from near the base film to far away from the base film; the base film and the electrolyte layer contain the modified solid electrolyte particles as described in any one of claims 1-2 and the crown ether functionalized single ion conductor polymer.

6. The solid electrolyte membrane according to claim 5, characterized in that, The base membrane is prepared by adding modified solid electrolyte particles to a polyamic acid (PAA) solution, spinning to obtain a fiber membrane, and then subjecting the fiber membrane to thermal imidization treatment to obtain the base membrane; preferably, the mass ratio of modified solid electrolyte particles to polyamic acid (PAA) is (5-8):(2-5); more preferably, it is 7:

3.

7. The solid electrolyte membrane according to claim 5, characterized in that, The crown ether functionalized single-ion conductor polymers include polyacrylic acid and crown ethers modified on the polyacrylic acid; Preferably, the crown ether functionalized single-ion conductor polymer is prepared by dissolving polyacrylic acid in DMF solution, adding EDC and DMAP to activate the carboxyl groups, then adding 12-crown-4, and reacting at room temperature to graft the crown ether groups onto the polymer backbone. Preferably, the mass ratio of polyacrylic acid to 12-crown-4 is 5:(0.225-0.9); more preferably, it is 5:0.

45.

8. The solid electrolyte membrane according to claim 6, characterized in that, The content of modified solid electrolyte particles in the first electrolyte layer, the second electrolyte layer, and the third electrolyte layer decreases sequentially, while the content of crown ether functionalized single-ion conductor polymer increases sequentially. Preferably, the thickness ratio of the first electrolyte layer, the second electrolyte layer, and the third electrolyte layer is (5-10):(20-30):(5-10).

9. The solid electrolyte membrane according to claim 6, characterized in that, The first electrolyte layer comprises MOF@PDA@LLZTO, crown ether functionalized single-ion conductor polymer, LiTFSI, and SiO2; preferably, the mass ratio of MOF@PDA@LLZTO, crown ether functionalized single-ion conductor polymer, LiTFSI, and SiO2 is (20-50):(30-60):(15-20):5; more preferably, it is 40:40:15:5; The second electrolyte layer comprises MOF@PDA@LLZTO, crown ether functionalized single-ion conductor, LiTFSI, and SiO2; preferably, the mass ratio of MOF@PDA@LLZTO, crown ether functionalized single-ion conductor polymer, LiTFSI, and SiO2 is (10-25):(55-60):(15-25)::5; more preferably, it is 10:60:25:5; The third electrolyte layer comprises MOF@PDA@LLZTO, crown ether functionalized single-ion conductor, LiTFSI, LiNO3, and FEC; the mass ratio of MOF@PDA@LLZTO, crown ether functionalized single-ion conductor, LiTFSI, LiNO3, and FEC is (5-15):(60-70):(10-15):5:5; preferably 5:65:20:5:

5.

10. A solid-state battery, characterized in that, It includes a positive electrode, a solid electrolyte membrane as described in any one of claims 5-9, and a negative electrode, wherein the base film is disposed near the positive electrode side; and the electrolyte layer is disposed near the negative electrode side.

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