Breakdown-resistant lithium ion solid-state battery diaphragm, preparation method thereof and lithium ion battery

Abstract

The invention relates to a breakdown-resistant lithium ion solid-state battery diaphragm, a preparation method thereof and a lithium ion battery. The breakdown-resistant lithium-ion solid-state battery diaphragm is of a layered structure and comprises a base membrane layer, a self-repairing polymer layer and a composite coating, the self-repairing polymer layer and the composite coating are sequentially arranged on the outer surface of the base membrane layer, the thickness of the self-repairing polymer layer is 1-5 microns, and the composite coating comprises a nano-particle reinforced polymer and an interface reinforcing agent. According to the breakdown-resistant lithium ion solid-state battery diaphragm provided by the invention, the breakdown-resistant performance, the self-repairing capability and the overall electrochemical performance of the lithium ion battery diaphragm can be effectively improved on the whole, the safety and the performance of a lithium ion battery can be remarkably improved, and particularly, the breakdown-resistant lithium ion solid-state battery diaphragm has obvious advantages in high-energy density and high-power application.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery materials, and particularly to a lithium-ion solid-state battery separator resistant to breakdown, a preparation method thereof, and a lithium-ion battery. Background Art

[0002] Lithium-ion batteries have become an indispensable energy solution in modern electronic devices and electric vehicles. However, traditional liquid electrolyte lithium-ion batteries have safety hazards, such as leakage, thermal runaway, and battery short circuit. Solid-state batteries have become a research hotspot due to their high safety, high energy density, and long cycle life. The battery separator plays a crucial role in solid-state batteries. Its main function is to separate the positive and negative electrodes of the battery, ensure the passage of lithium ions while blocking electron transmission. It is a thin film with a microporous structure and has the function of preventing the battery from overheating.

[0003] In lithium metal batteries, lithium metal forms lithium dendrites during charge and discharge processes. Lithium dendrites can pierce the separator, leading to internal short circuit of the battery. The formation of lithium dendrites is related to the high reactivity of lithium metal, uneven deposition, and the interfacial reaction between the electrolyte and lithium metal. There may be micropores, cracks, or other defects in the separator during the production process, and these defects may become channels for internal short circuit of the battery during battery operation, resulting in breakdown of the separator.

[0004] As the battery usage time increases and the number of charge and discharge cycles increases, the separator will gradually age. During the battery aging process, the separator may be affected by various factors such as chemical corrosion, thermal aging, and mechanical stress. These factors may cause structural changes, material degradation, or accumulation of microscopic damage in the separator material, which may reduce the mechanical strength of the separator, making it more likely to rupture or perforate under the action of factors such as internal battery pressure or lithium dendrite growth, thereby increasing the risk of separator breakdown. After the separator breaks down, a short circuit will occur between the positive and negative electrodes, which will trigger gas reactions inside the lithium battery, generating a large amount of heat and gas, which may cause the battery to overheat, catch fire, or even explode, affecting the overall performance and safety of the battery.

[0005] Therefore, it is necessary to provide a lithium-ion solid-state battery separator resistant to breakdown. Summary of the Invention

[0006] In the prior art, as the battery usage time increases and the number of charge and discharge cycles increases, the separator will gradually age, thereby increasing the risk of separator breakdown, and further affecting the overall performance and safety of the battery. Therefore, it is necessary to provide a lithium-ion solid-state battery separator resistant to breakdown, a preparation method thereof, and a lithium-ion battery to solve the above problems.

[0007] In a first aspect, the present invention provides a breakdown-resistant lithium-ion solid-state battery separator, which has a layered structure and includes a base film layer, a self-healing polymer layer, and a composite coating sequentially disposed on the outer surface of the base film layer. The thickness of the self-healing polymer layer is 1-5 μm, and the composite coating includes a nanoparticle-reinforced polymer and an interfacial enhancer.

[0008] In one implementation, the base film layer includes a matrix material, an inorganic filler, and an ion conductor. The matrix material includes any one of polyvinylidene fluoride, polyetherimide, or polyethylene oxide. The inorganic filler includes any one of alumina, zirconia, and lithium sulfide. The ion conductor includes any one of polyethylene oxide, lithium bis(trifluoromethanesulfonyl)imide, lithium sulfide, lithium lanthanum zirconium oxide, and lithium fluoride. The film thickness of the base film layer is 5-20 μm.

[0009] In one implementation, the self-healing polymer includes any one of polythiol, polymethyl methacrylate, and polyacrylate gel.

[0010] In one implementation, the nanoparticle-reinforced polymer includes a polymer matrix and nanoparticles. The polymer matrix is polyvinylidene fluoride or polyethyleneimine, and the nanoparticles include any one of graphene, carbon nanotubes, and silver nanoparticles.

[0011] In one implementation, in the nanoparticle-reinforced polymer, the mass ratio of the polymer matrix to the nanoparticles is 80:20 to 95:5.

[0012] In one implementation, the interfacial enhancer is a silane coupling agent or a titanate coupling agent.

[0013] In one implementation, the thickness of the composite coating is 2-5 μm.

[0014] In one implementation, the composite coating further includes a second network polymer that forms a self-healing interpenetrating network structure with the self-healing polymer. The second network polymer includes any one of 2-hydroxyethyl methacrylate, polyurethane prepolymer, polyvinyl alcohol, and isocyanate-terminated polymer. The mass fraction of the second network polymer in the composite coating is 2-10 wt%.

[0015] In a second aspect, the present invention further provides a method for preparing a breakdown-resistant lithium-ion solid-state battery separator, which is used for the breakdown-resistant lithium-ion solid-state battery separator of the present invention and includes the following specific steps: S1. Dispersing the polymer matrix and the inorganic filler in an organic solvent in proportion, mixing them evenly by ultrasonic wave / stirring, and forming a film on a flat plate by a casting method to obtain the base film layer; S2. Dissolve the self-healing polymer in a solvent to prepare a coating or colloid, and uniformly coat the outer surface of the base film layer by a coating method to obtain the self-healing polymer layer; S3. Mix the polymer matrix with the nanoparticles, and through ultrasonic treatment or ball milling dispersion, make the nanoparticles uniformly distributed. Add an interfacial enhancer and mix to obtain a mixed slurry, and coat the mixed slurry on the outer surface of the self-healing polymer layer; S4. Perform heat treatment on the coated film material. The heat treatment temperature is 120 - 180 °C, and the heat treatment time is 30 - 60 minutes to obtain the breakdown-resistant lithium-ion solid-state battery separator.

[0016] In a third aspect, the present invention also provides a lithium-ion battery, which includes the breakdown-resistant lithium-ion solid-state battery separator described in any one of the above.

[0017] Beneficial effects: The breakdown-resistant lithium-ion solid-state battery separator provided by the present invention can not only improve the durability of the film through the self-healing polymer layer, but also automatically repair when micro-damage occurs, increasing the safety of the battery; through the composite coating, the anti-electric breakdown function and interfacial enhancement technology are integrated, further enhancing the stability and safety of the overall film; by setting the layered structure, the advantages of the composite coating and the self-healing polymer layer are fully utilized. Generally, it can effectively improve the breakdown resistance performance, self-healing ability and overall electrochemical performance of the lithium-ion battery separator, and can significantly improve the safety and performance of the lithium-ion battery, especially having obvious advantages in high energy density and high power applications. Description of the Drawings

[0018] Figure 1 is a step flow chart of the preparation method of the breakdown-resistant lithium-ion solid-state battery separator provided by the present invention.

[0019] The realization, functional characteristics and advantages of the object of the present invention will be further described with reference to the embodiments and the drawings. Detailed Embodiments

[0020] In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention. In addition, the descriptions of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. below mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms are not necessarily directed to the same embodiment or example. Moreover, the technical features involved in various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0021] The present invention provides a breakdown-resistant lithium-ion solid-state battery separator, which has a layered structure and includes a base film layer, a self-healing polymer layer, and a composite coating sequentially disposed on the outer surface of the base film layer. The thickness of the self-healing polymer layer is 1-5 μm, and the composite coating includes nanoparticle-reinforced polymer and interface enhancer. The breakdown-resistant lithium-ion solid-state battery separator provides basic mechanical strength and structural stability by providing the base film layer; by providing the self-healing polymer layer, it can self-heal when mechanically damaged by cracks or small holes, effectively avoiding battery short circuit or failure caused by damage to the battery separator, and improving the service life and safety of the battery; by providing the composite coating, the breakdown resistance and interface stability of the separator are improved.

[0022] Specifically, the base film layer includes a matrix material, an inorganic filler, and an ion conductor. The matrix material includes any one of polyvinylidene fluoride (PVDF), polyetherimide (PEI), or polyethylene oxide (PEO). The inorganic filler includes any one of aluminum oxide (Al2O3), zirconia, and lithium sulfide. The film thickness of the base film layer is 5-20 μm. The ion conductor includes any one of polyethylene oxide (PEO), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium sulfide (Li3PS4), lithium lanthanum zirconium oxide (LLZO), and lithium fluoride (LiF).

[0023] Among them, the matrix material is used to provide the structural strength and mechanical stability of the separator, the inorganic filler is used to improve the thermal stability, mechanical strength, and electrolyte permeability of the separator; the ion conductor can enhance the ionic conductivity and improve the overall performance of the battery. By comprehensively utilizing the base film layer, the solid-state battery separator not only has a good isolation function, but also can provide sufficient ionic conductivity and mechanical strength, while improving the safety of the battery.

[0024] Specifically, the self-healing polymer includes any one of polythiol, polymethyl methacrylate, and polyacrylate gel. The self-healing polymer has self-healing ability, which can significantly improve the durability and safety of the separator.

[0025] Specifically, in the composite coating, the nanoparticle-reinforced polymer includes a polymer matrix and nanoparticles. The polymer matrix is polyvinylidene fluoride (PVDF) or polyethyleneimine (PEI), and the nanoparticles include any one of graphene, carbon nanotubes (CNTs), and silver nanoparticles. Among them, the nanoparticles can significantly improve the mechanical strength and wear resistance of the separator, preventing the separator from cracking or wearing due to mechanical stress during use. The nanoparticles have high thermal stability, which can improve the stability of the separator under high-temperature conditions, preventing the separator from deforming or failing due to temperature changes. The combination of the nanoparticles and the polymer matrix can optimize the electrochemical performance of the separator, improve the conduction efficiency of lithium ions, and thus enhance the overall performance of the battery.

[0026] Among them, in the nanoparticle-reinforced polymer, the mass ratio of the polymer matrix to the nanoparticles is between 80:20 and 95:5. The interfacial enhancer is a silane coupling agent or a titanate coupling agent. Preferably, the thickness of the composite coating is 2 - 5 μm. Preferably, the silane coupling agent is KH-550. The nanoparticle-reinforced polymer can enhance the mechanical strength and conductivity of the separator, while the silane coupling agent or titanate coupling agent can improve the interfacial stability of the composite coating, reduce the interfacial resistance, and improve the overall performance.

[0027] Furthermore, the composite coating further includes a second network polymer that forms a self-healing interpenetrating polymer network structure (IPN) with the self-healing polymer. The second network polymer includes any one of poly(2-hydroxyethyl methacrylate), polyurethane prepolymer (PU), polyvinyl alcohol (PVA), and isocyanate-terminated polymer. The mass fraction of the second network polymer in the composite coating is 2 - 10 wt%. Among them, poly(2-hydroxyethyl methacrylate) (PHEMA) can be polymerized and crosslinked into a network; the polyurethane prepolymer (PU) contains -NH- and -C=O and can form hydrogen bonds with thiols; polyvinyl alcohol (PVA) is water-soluble, can form a hydrogen bond network, and has good interfacial affinity with polythiol; the isocyanate-terminated polymer can undergo an addition reaction with SH to form crosslinks and has a chemical coupling self-healing function.

[0028] After adding the second network polymer, a self-healing interpenetrating polymer network structure can be formed, significantly enhancing the self-healing ability of the material, enabling the separator to self-repair more quickly and effectively when damaged. In addition, the introduction of the second network polymer can improve the structural stability of the composite coating, preventing the separation or peeling off of the composite coating caused by external stress or environmental changes. The second network polymer can improve the interfacial bonding force between the composite coating and the self-healing polymer layer, ensure the tight bonding between layers, and improve the overall performance of the entire separator.

[0029] Refer to in combination Figure 1 , Figure 1It is the process flow diagram of the preparation method of the breakdown-resistant lithium-ion solid-state battery separator provided by the present invention.

[0030] The present invention also provides a preparation method of a breakdown-resistant lithium-ion solid-state battery separator, which includes the following specific steps: S1. Dispersing the polymer matrix and the inorganic filler in an organic solvent in proportion, mixing evenly by ultrasonic wave / stirring, and forming a film on a flat plate by the casting method to obtain the base film layer; S2. Dissolving the self-healing polymer in a solvent to prepare a coating or a colloid, and uniformly coating the outer surface of the base film layer by a coating method to obtain the self-healing polymer layer; S3. Mixing the polymer matrix and the nanoparticles, uniformly distributing the nanoparticles by ultrasonic treatment or ball milling dispersion, adding an interfacial enhancer and mixing to obtain a mixed slurry, and coating the mixed slurry on the outer surface of the self-healing polymer layer; S4. Performing heat treatment on the coated film material, the heat treatment temperature is 120-180 °C, and the heat treatment time is 30-60 minutes to obtain the breakdown-resistant lithium-ion solid-state battery separator.

[0031] When the composite coating further includes a second network polymer that forms a self-healing interpenetrating polymer network structure (IPN) with the self-healing polymer, it further includes in S3: adding the self-healing polymer to the composite coating slurry, after the composite coating contacts the self-healing layer, part of the self-healing polymer penetrates into the self-healing polymer layer, heating to 70-100 °C, triggering the cross-linking and forming of the self-healing interpenetrating polymer network structure to form the final composite coating.

[0032] The layered structure in the present invention can more precisely control the thickness, composition and function of each layer, so as to optimize the performance of each layer. At the same time, when preparing the layered structure, the characteristics of each layer can be precisely controlled through coating or heat treatment of each layer, and the unique properties of each layer of material can be fully utilized. The composite coating and the self-healing polymer layer can play their respective advantages targeted to achieve the synergistic function of the materials. Compared with mixing the materials into a slurry, the layered structure provided by the present invention has higher adjustability and optimization, which helps to maximize the functions of the materials of each layer.

[0033] Example 1 Material selection: Base film layer: Select polyvinylidene fluoride (PVDF) as the matrix material, alumina (Al2O3) as the inorganic filler, and lithium sulfide (Li3PS4) as the ion conductor.

[0034] Self-healing polymer layer: Select polythiol.

[0035] Composite coating: PVDF is selected as the polymer matrix, graphene as the nanoparticles, and silane coupling agent (KH-550) as the interface enhancer.

[0036] Preparation steps: S1. PVDF and alumina are dispersed in dimethylacetamide (DMAc) solvent at a mass ratio of 90:10, ultrasonicated for 30 minutes, and stirred and mixed evenly. Lithium sulfide (Li3PS4) is added and stirring continues for 1 hour to ensure uniform mixing. A film is formed on a flat plate using the casting method, with the film thickness controlled at 15 μm, and a base film layer is obtained through drying treatment.

[0037] S2. Preparation of the self-healing polymer layer: Polythiol is dissolved in toluene solvent to prepare a coating with a concentration of 5%. It is uniformly coated on the outer surface of the base film layer using the coating method, with the coating thickness controlled at 2 μm, and a self-healing polymer layer is obtained through drying treatment.

[0038] S3. Preparation of the composite coating: PVDF and graphene are mixed at a mass ratio of 90:10, ultrasonicated for 30 minutes to ensure uniform distribution of the nanoparticles. Silane coupling agent (KH-550) is added and stirred and mixed evenly. The mixed slurry is uniformly coated on the outer surface of the self-healing polymer layer using the coating method, with the coating thickness controlled at 3 μm, and a composite coating is obtained through drying treatment.

[0039] S4. Heat treatment: The coated film material is heat-treated at a temperature of 150 °C for 45 minutes to obtain the final breakdown-resistant lithium-ion solid-state battery separator.

[0040] Example 2 Base film layer: PVDF + Al2O3 + Li3PS4, thickness 15 μm; Self-healing polymer layer: Polymethyl methacrylate (PMMA), thickness 2 μm; Composite coating: PVDF + graphene + KH-550, thickness 3 μm.

[0041] The specific preparation process is the same as that in Example 1 and will not be elaborated here.

[0042] Example 3 Base film layer: PVDF + Al2O3 + Li3PS4, thickness 15 μm; Self-healing polymer layer: Polythiol, thickness 2 μm; Composite coating: PEI + graphene + titanate coupling agent, thickness 3 μm.

[0043] The specific preparation process is the same as that in Example 1 and will not be elaborated here.

[0044] Example 4 Base film layer: PVDF + Al2O3 + Li3PS4, with a thickness of 15 μm; Self-healing polymer layer: polyacrylate gel, with a thickness of 2 μm; Composite coating: PEI + graphene + titanate coupling agent, with a thickness of 3 μm.

[0045] The specific preparation process is the same as that in Example 1 and will not be elaborated here.

[0046] Example 5, Base film layer: PEO + alumina (Al2O3) + lithium fluoride (LiF), with a thickness of 15 μm; Self-healing polymer layer: polythiol, with a thickness of 2 μm; Composite coating: PEO + carbon nanotubes + titanate coupling agent, with a thickness of 3 μm; The specific preparation process is the same as that in Example 1 and will not be elaborated here.

[0047] Example 6, Base film layer: PVDF + zirconia (ZrO2) + lithium sulfide (Li3PS4), with a thickness of 15 μm; Self-healing polymer layer: polythiol, with a thickness of 2 μm; Composite coating: PVDF + graphene + silane coupling agent (KH-550), with a thickness of 3 μm; The specific preparation process is the same as that in Example 1 and will not be elaborated here.

[0048] Example 7, Base film layer: polyethylene oxide (PEO) + alumina (Al2O3) + lithium sulfide (Li3PS4), with a thickness of 15 μm; Self-healing polymer layer: polyacrylate gel, with a thickness of 2 μm; Composite coating: PEO + carbon nanotubes + silane coupling agent (KH-550), with a thickness of 3 μm; The specific preparation process is the same as that in Example 1 and will not be elaborated here.

[0049] Example 8, Base film layer: PEI + alumina (Al2O3) + LiTFSI, with a thickness of 15 μm; Self-healing polymer layer: polymethyl methacrylate (PMMA), with a thickness of 15 μm; Composite coating: PEI + graphene + titanate coupling agent, with a thickness of 15 μm; The specific preparation process is the same as that in Example 1 and will not be elaborated here.

[0050] Example 9, Base film layer: PVDF + aluminum oxide (Al2O3) + lithium sulfide (Li3PS4), with a thickness of 15 μm; Self-healing polymer layer: polymethyl methacrylate (PMMA), with a thickness of 2 μm; Composite coating: PVDF + graphene + KH-550 + polyurethane prepolymer (PU), with a thickness of 3 μm; The specific preparation process is the same as that in Example 1 and will not be elaborated here.

[0051] Example 10, Base film layer: PEO + aluminum oxide (Al2O3) + lithium fluoride (LiF), with a thickness of 15 μm; Self-healing polymer layer: polythiol, with a thickness of 2 μm; Composite coating: PEO + carbon nanotubes + titanate coupling agent + 2-hydroxyethyl methacrylate, with a thickness of 3 μm; The specific preparation process is the same as that in Example 1 and will not be elaborated here.

[0052] Comparative Example 1, Base film layer: PVDF + aluminum oxide (Al2O3) + lithium sulfide (Li3PS4), with a thickness of 15 μm; Composite coating: PVDF + graphene + KH-550, with a thickness of 3 μm; Comparative Example 2, Base film layer: PVDF + aluminum oxide (Al2O3) + lithium sulfide (Li3PS4), with a thickness of 15 μm; Self-healing polymer layer: polythiol, with a thickness of 2 μm; Comparative Example 3, Base film layer: PEO + aluminum oxide (Al2O3) + lithium fluoride (LiF), with a thickness of 15 μm; Self-healing polymer layer: polythiol, with a thickness of 2 μm; Composite coating: PEO + silane coupling agent (KH-550), with a thickness of 3 μm.

[0053] Comparative Example 4, Base film layer: PEI + aluminum oxide (Al2O3) + lithium sulfide (Li3PS4), with a thickness of 15 μm; Self-healing polymer layer: polyacrylate gel, with a thickness of 2 μm; Composite coating: PEI + graphene, with a thickness of 3 μm.

[0054] Perform electrical performance, mechanical performance, and cyclic charge-discharge tests on the breakdown-resistant lithium-ion solid-state battery separators provided in the above examples and comparative examples.

[0055] 1. Electrical performance testing Breakdown voltage testing: Use standard voltage breakdown testing equipment to conduct breakdown voltage testing on the separator material according to ISO 18079 standard. The testing process is to apply a gradually increasing voltage across the sample until the separator breaks down. Record the breakdown voltage.

[0056] Ionic conductivity testing: Apply electrodes on both sides of the sample using an electrochemical impedance spectroscopy (EIS) instrument to measure the impedance. Analyze the Nyquist plot to obtain the ionic conductivity. The test results are shown in Table 1.

[0057] Table 1. Breakdown voltage test results As can be seen from Table 1, the breakdown voltage of the separator of the lithium-ion solid-state battery of the present invention is significantly higher than that of traditional polypropylene and polyethylene separators. The separators of the examples have higher breakdown voltages and ionic conductivities, indicating that the designs of these examples improve the conductivity and breakdown resistance of the separators, can withstand higher voltages, and greatly reduce the risks of battery short circuit and fire. Among them, the data of Example 9 and Example 10 can reach the optimum, indicating that the addition of the second network polymer in the composite coating can play a certain promoting role.

[0058] 2. Mechanical performance testing Tensile strength testing: Use an electronic universal testing machine to conduct tensile testing according to ASTM D882 standard. Prepare separator samples with standard dimensions (10 mm x 50 mm), and record the maximum tensile strength and elongation of the material.

[0059] Tear strength testing: Conduct tear strength testing according to ASTM D1004 standard. Use standard tear test equipment to prepare standard tear samples, test the tear resistance of the separator under external force, and record the tear strength. The test results are shown in Table 2.

[0060] Table 2. Mechanical performance test results From the results in Table 2, it can be seen that the separators in the examples provided by the present invention far exceed the comparative examples and traditional PP and PE separators in terms of tensile strength, elongation, and tear strength. Among them, Example 9 performs excellently in terms of tensile strength and elongation, which is attributed to the excellent combination of its thickness and self-healing material, and the addition of the second network polymer.

[0061] 3. Cyclic charge and discharge testing Use the separators corresponding to the examples and comparative examples as the separators of lithium-ion solid-state batteries, and prepare button cells according to the following method: Take Example 1 as an example: Cathode material: LiFePO4; Anode material: graphite; Electrolyte: LiPF6 solution; Separator: The PVDF + Al2O3 + Li3PS4 separator prepared in Example 1, with the self-healing layer and composite coating already processed.

[0062] Electrode preparation: Mix LiFePO4 with a conductive agent (carbon black) and a binder (PVDF) in proportion, coat it on aluminum foil, and cut it into circular pieces after drying as the positive electrode. Mix graphite with a conductive agent and a binder in proportion, coat it on copper foil, and cut it into circular pieces after drying as the negative electrode.

[0063] Button cell assembly: Place the separator on the negative electrode sheet in a glove box. After adding the electrolyte, align and press the positive electrode sheet with the separator. Use a button cell encapsulation device for encapsulation to ensure the battery's airtightness.

[0064] Testing equipment: Use a battery testing system to perform multiple charge-discharge cycles. The charging voltage of the battery is set to 4.2V, and the discharging voltage is 2.5V.

[0065] Number of cycles: The test was conducted for 500 charge-discharge cycles, and the charge-discharge time for each cycle was 1 hour. Record the capacity retention rate and Coulomb efficiency for each cycle.

[0066] The test results are shown in Table 3.

[0067] Table 3. Table of charge-discharge cycle test results From the data in Table 3, it can be concluded that the materials of the examples perform well in terms of capacity retention rate. Especially for Example 1, Example 6, Example 9, and Example 10, they can all maintain a high capacity retention rate (above 90%) after 500 cycles, proving that the anti-breakdown lithium-ion solid-state battery separator provided by the present invention improves the battery's initial capacity, capacity retention rate, Coulomb efficiency, etc., and can effectively extend the battery's service life, enhance its safety and stability. Especially for Example 9 and Example 10, they show the highest initial capacity, capacity retention rate, and Coulomb efficiency, while the performance of the comparative examples and traditional PP and PE separators is significantly worse.

[0068] Due to the introduction of the self-healing polymer layer and the composite coating in the lithium-ion solid-state battery separator in the embodiment, the separator can effectively prevent battery short circuits and enhance the breakdown resistance of the battery, ensuring the safety of the battery during long-term use. The materials of the embodiment exhibit good electrochemical performance, which can significantly improve the capacity retention rate, cycle performance, and charge-discharge efficiency of lithium-ion batteries. Especially in high-energy density and high-power applications, the separator materials in the embodiment demonstrate significant advantages, meeting the requirements and market trends of modern lithium-ion batteries, further indicating the superiority of the novel separator materials provided by the present invention in lithium-ion solid-state batteries.

[0069] In the present invention, by providing a composite coating of nanoparticle-reinforced polymer and interface enhancer, the breakdown resistance of the separator is improved, and the risk of battery short circuits is reduced; by adding a self-healing polymer layer, it can self-repair when mechanically damaged, extending the service life of the separator and enhancing the safety of the battery; after adding a second network polymer to the composite coating, a self-healing interpenetrating network structure can be formed, significantly enhancing the self-healing ability of the material, enabling the separator to self-repair more quickly and effectively when damaged; at the same time, materials with good ionic conductivity, such as polyethylene oxide (PEO) and lithium sulfide (Li3PS4), are used in the base film layer to ensure the efficient charge-discharge performance of the battery. And by using appropriate matrix materials and inorganic fillers, the separator has excellent mechanical strength and thermal stability and can work stably in high-temperature environments. The breakdown-resistant lithium-ion solid-state battery separator provided by the present invention can generally effectively improve the breakdown resistance, self-healing ability, and overall electrochemical performance of lithium-ion battery separators, has good mechanical strength, conductivity, and thermal stability, ensuring that the separator can work effectively in high-energy density and high-power applications, and can significantly improve the safety and performance of lithium-ion batteries, especially having obvious advantages in high-energy density and high-power applications.

[0070] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural or equivalent process transformations made using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are similarly included in the patent protection scope of the present invention.

Claims

1. A lithium-ion solid-state battery separator with breakdown resistance, characterized in that, It has a layered structure, including a base film layer, a self-healing polymer layer and a composite coating sequentially arranged on the outer surface of the base film layer. The thickness of the self-healing polymer layer is 1-5 μm, and the composite coating includes a nanoparticle-reinforced polymer and an interfacial enhancer.

2. The lithium-ion solid-state battery separator with breakdown resistance according to claim 1, characterized in that, The base film layer includes a matrix material, an inorganic filler and an ion conductor. The matrix material includes any one of polyvinylidene fluoride, polyetherimide or polyethylene oxide. The inorganic filler includes any one of alumina, zirconia and lithium sulfide. The ion conductor includes any one of polyethylene oxide, lithium bis(trifluoromethanesulfonyl)imide, lithium sulfide, lithium lanthanum zirconium oxide and lithium fluoride. The film thickness of the base film layer is 5-20 μm.

3. The lithium-ion solid-state battery separator with breakdown resistance according to claim 1, wherein The self-healing polymer includes any one of polythiol, polymethyl methacrylate and polyacrylate gel.

4. The lithium-ion solid-state battery separator with breakdown resistance according to claim 1, characterized in that, The nanoparticle-reinforced polymer includes a polymer matrix and nanoparticles. The polymer matrix is polyvinylidene fluoride or polyethyleneimine. The nanoparticles include any one of graphene, carbon nanotubes and silver nanoparticles.

5. The lithium-ion solid-state battery separator with breakdown resistance according to claim 1, wherein, In the nanoparticle-reinforced polymer, the mass ratio of the polymer matrix to the nanoparticles is 80:20 to 95:

5.

6. The lithium-ion solid-state battery separator with breakdown resistance according to claim 1, wherein, The interfacial enhancer is a silane coupling agent or a titanate coupling agent.

7. The lithium-ion solid-state battery separator with breakdown resistance according to claim 1, wherein The composite coating further includes a second network polymer that forms a self-healing interpenetrating network structure with the self-healing polymer. The second network polymer includes any one of 2-hydroxyethyl methacrylate, polyurethane prepolymer, polyvinyl alcohol and isocyanate-terminated polymer. The mass fraction of the second network polymer in the composite coating is 2-10 wt%.

8. The lithium-ion solid-state battery separator with breakdown resistance according to claim 1, characterized in that The thickness of the composite coating is 2-5 μm.

9. A preparation method of a breakdown-resistant lithium-ion solid-state battery separator, which is used to prepare the breakdown-resistant lithium-ion solid-state battery separator according to any one of claims 1 to 8, and includes the following specific steps: S1. Dispersing the polymer matrix and the inorganic filler in an organic solvent in proportion, mixing evenly by ultrasonic wave / stirring, and forming a film on a flat plate by a casting method to obtain the base film layer; S2. Dissolving the self-healing polymer in a solvent to prepare a coating or a colloid, and uniformly coating the outer surface of the base film layer by a coating method to obtain the self-healing polymer layer; S3. Mixing the polymer matrix and the nanoparticles, and uniformly distributing the nanoparticles by ultrasonic treatment or ball milling dispersion, adding an interfacial enhancer and mixing to obtain a mixed slurry, and coating the mixed slurry on the outer surface of the self-healing polymer layer; S4. Performing heat treatment on the coated film material, the heat treatment temperature is 120-180 °C, and the heat treatment time is 30-60 minutes to obtain the breakdown-resistant lithium-ion solid-state battery separator.

10. A lithium-ion battery, characterized in that, It includes the breakdown-resistant lithium-ion solid-state battery separator according to any one of claims 1 to 8.

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