Lithium-ion battery thin film and method of making

Abstract

The application discloses a lithium ion battery film and a preparation method thereof, and belongs to the technical field of lithium ion batteries. The lithium ion battery film comprises modified PET material, inorganic nanoparticles, a dispersing agent and an antioxidant. The lithium ion battery film prepared from the modified PET material can solve the problem of precipitation of the film in a lithium ion battery.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a lithium-ion battery thin film and its preparation method. Background Technology

[0002] As a core component of new energy vehicles, consumer electronics, and energy storage systems, the safety and reliability of lithium-ion batteries highly depend on the stability of their internal materials. In battery packaging, PET (Polyethylene Terephthalate) film is widely used as an insulating layer or encapsulation material between cells due to its excellent insulation, mechanical strength, and cost advantages, providing an important guarantee for the stable operation of lithium-ion batteries.

[0003] However, the PET film material of conventional lithium-ion batteries is prone to precipitation in high-temperature and electrolyte environments, which can contaminate the electrodes, damage the structure and performance of the electrode surface, reduce the activity of the electrodes, and thus affect the charging and discharging efficiency and capacity of the battery, shortening the battery's lifespan. Summary of the Invention

[0004] The main objective of this application is to provide a lithium-ion battery thin film and its preparation method, aiming to solve the technical problem that conventional thin films are prone to precipitation in lithium-ion batteries.

[0005] To achieve the above objectives, this application provides a lithium-ion battery film comprising modified PET material, inorganic nanoparticles, dispersant, and antioxidant.

[0006] Optionally, the modified PET material is obtained through the following steps:

[0007] Terephthalic acid, ethylene glycol and spirocyclic glycol were mixed and heated to prepare the first reactant;

[0008] A catalyst is added to the first reactant, and the temperature is increased to carry out a co-condensation reaction to obtain the modified PET material.

[0009] Optionally, the molar ratio of terephthalic acid: ethylene glycol: spirocyclic diol is 1:(1.8-2.2):(0.05-0.15).

[0010] Optionally, the spirocyclic diol comprises 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane.

[0011] Optionally, the lithium-ion battery film comprises, by weight parts:

[0012] Modified PET material: 80-90 parts;

[0013] Inorganic nanoparticles: 5-15 parts;

[0014] Dispersant: 1-3 parts;

[0015] Antioxidant: 0.5 to 2 parts.

[0016] Optionally, the inorganic nanoparticles include at least one of boehmite, silica, and montmorillonite.

[0017] Optionally, the dispersant includes at least one of polycarboxylate dispersants and polyacrylate dispersants;

[0018] And / or, the antioxidant includes at least one of phenolic antioxidants and amine antioxidants.

[0019] Optionally, the thickness of the lithium-ion battery film is 20–200 μm.

[0020] This application also provides a method for preparing a lithium-ion battery thin film, the method comprising the following steps:

[0021] We provide modified PET materials, inorganic nanoparticles, dispersants, and antioxidants.

[0022] The modified PET material, the inorganic nanoparticles, the dispersant, and the antioxidant were melt-co-extruded to obtain a mixture.

[0023] The mixture is then formed into a sheet;

[0024] The sheet is biaxially stretched to obtain a lithium-ion battery film.

[0025] Optionally, the temperature of the melt co-extrusion is 260–290°C.

[0026] This application discloses a lithium-ion battery thin film and its preparation method. The lithium-ion battery thin film includes modified PET material, inorganic nanoparticles, a dispersant, and an antioxidant. The modified PET material serves as the matrix, and its high-temperature resistance and electrolyte resistance are enhanced through chemical modification, reducing the dissolution or decomposition of film components caused by interfacial side reactions. The inorganic nanoparticles are uniformly dispersed in the modified PET material, forming a physical barrier network within the lithium-ion battery thin film, making the various components in the film more stable within the system. The dispersant enables the inorganic nanoparticles to be uniformly dispersed in the modified PET material, preventing agglomeration and making the interface more stable. The antioxidant inhibits the oxidation reaction between the modified PET material and other components, preventing the material from decomposing due to oxidation and producing small molecule precipitation. Therefore, the lithium-ion battery thin film of this application possesses chemical stability and can act as a barrier and protector, preventing precipitation in the lithium-ion battery. Attached Figure Description

[0027] Figure 1 This is a schematic flowchart of the lithium-ion battery thin film preparation method involved in the embodiments of this application.

[0028] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0030] Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution that simultaneously satisfies A and B. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0031] The first aspect of this application provides a lithium-ion battery film, which includes modified PET material, inorganic nanoparticles, dispersant, and antioxidant.

[0032] In one feasible embodiment, the lithium-ion battery film comprises modified PET material, inorganic nanoparticles, dispersant, and antioxidant.

[0033] Optionally, PET itself possesses excellent mechanical properties, transparency, chemical resistance, and gas barrier properties, providing fundamental performance guarantees for composite materials. Modified PET materials, through chemical modification, introduce chemical groups into PET materials, improving their mechanical properties, high-temperature resistance, and electrolyte resistance. Furthermore, modified PET materials serve as a matrix material, providing a dispersion matrix for inorganic nanoparticles, dispersants, and antioxidants, jointly preparing lithium-ion battery films.

[0034] Optionally, inorganic nanoparticles refer to inorganic material particles with a size in the nanometer range. Inorganic nanoparticles can be dispersed in the modified PET material matrix, forming a strong interfacial bond with the matrix, thus enhancing and toughening the material. Inorganic nanoparticles also possess good thermal stability and thermal conductivity, which can improve the heat distortion temperature and thermal conductivity of the modified PET material.

[0035] Optionally, the main function of the dispersant is to improve the dispersion state of various additives and fillers in the modified PET material matrix, prevent the agglomeration of additive and filler particles, and thus improve the overall performance of the lithium-ion battery film.

[0036] Optionally, antioxidants refer to substances that can prevent or delay the oxidative degradation of modified PET materials, slow down the breakage of PET chains, and reduce the precipitation of degradation products.

[0037] In one feasible embodiment, the modified PET material is obtained through the following steps:

[0038] Terephthalic acid, ethylene glycol and spirocyclic glycol were mixed and heated to prepare the first reactant;

[0039] A catalyst was added to the first reactant, and the temperature was increased to carry out a co-condensation reaction to obtain the modified PET material.

[0040] Optionally, modified PET materials are made by adjusting the chemical structure of PET to give it better properties, such as better flexibility, high temperature resistance, and corrosion resistance, thereby broadening its application range.

[0041] Optionally, spirocyclic diols are key modifying components. As comonomers, the introduction of spirocyclic structures can enhance the rigidity and heat resistance of PET. Specifically, spirocyclic diols possess unique spirocyclic structures with high symmetry and rigidity. Introducing spirocyclic structures into the polymer molecular chain increases the rigidity of the chain, making it less prone to twisting and deformation, thereby improving the overall stability of the material. The greater steric hindrance of the spirocyclic structure prevents close packing between molecular chains, increasing the distance between them. This helps reduce the interaction forces between molecular chains, improving the processing performance of the material; on the other hand, it also provides some space for the molecular chains to move, allowing the material to disperse stress through appropriate movement of the molecular chains under stress, thus enhancing the toughness of the material. Furthermore, the hydroxyl groups in spirocyclic diols and spirocyclic diacids have high reactivity, enabling them to rapidly undergo esterification reactions with terephthalic acid and ethylene glycol monomers, participating in the polymer synthesis process. This allows for efficient reactions during the preparation of modified PET materials, shortening reaction time and improving production efficiency. Moreover, the spirocyclic structure has high bond energy, making it less prone to breakage at high temperatures. In the synthesis of PET molecular chains, the thermal stability of the molecular chains can be enhanced, increasing the thermal decomposition temperature of the material. The introduction of spiro-ring structures can improve the microstructure of composite materials, enabling them to form a denser molecular network. This dense structure can effectively prevent the penetration and diffusion of electrolyte molecules, reducing the contact area between the electrolyte and the material's interior, thereby improving the material's electrolyte resistance.

[0042] Optionally, the first reactants are a mixture of oligomers generated by esterification of terephthalic acid, ethylene glycol, and spirocyclic glycol under the catalysis of a catalyst. The first reactants include hydroxyethyl-terephthalate oligomers and spirocyclic prepolymers.

[0043] Optionally, a catalyst is added to raise the temperature and continue the reaction. After depressurization, a co-condensation reaction is carried out in a vacuum environment. The temperature of the co-condensation reaction is 245-260℃, the reaction time is 1-1.5h, and the pressure is 0.1-0.2MPa.

[0044] In one feasible embodiment, the temperature of the co-condensation reaction is 245–260°C.

[0045] Optionally, the temperature of the cocondensation reaction can be 245℃, 250℃, 255℃, 260℃, etc.

[0046] Optionally, the reaction time for the copolymerization reaction can be 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, etc.

[0047] Optionally, the pressure for the copolymerization reaction can be 0.1 kPa, 0.15 kPa, 0.2 kPa, etc.

[0048] The catalyst is a metal catalyst used to accelerate esterification or polycondensation reactions. The catalyst can be at least one of zinc acetate and antimony glycolate.

[0049] Optionally, the molar ratio of terephthalic acid: ethylene glycol: spirocyclic glycol is 1:(1.8–2.2):(0.05–0.15). For example, terephthalic acid: ethylene glycol: spirocyclic glycol = (1:1.8:0.05), (1:1.8:0.1), (1:1.8:0.15), (1:2.0:0.05), (1:2.0:0.1), (1:2.2:0.15), etc.

[0050] Optionally, under appropriate ratios, modified PET materials prepared from terephthalic acid, ethylene glycol, and spirocyclic glycol can impart high-temperature resistance and electrolyte resistance to lithium-ion battery films. However, excessively high spirocyclic glycol ratios can lead to the formation of unique crystalline structures that negatively impact the thermal properties of the modified PET material. Furthermore, an excessively high spirocyclic glycol ratio can cause the material to become brittle, resulting in decreased tensile strength and modulus, as well as a significant reduction in elongation at break, thus affecting the material's mechanical properties. An excessively high spirocyclic glycol ratio may also lead to increased film swelling due to an excessively high proportion of amorphous regions, causing the precipitation of low-molecular-weight segments or unreacted monomers in the electrolyte. Conversely, an excessively low spirocyclic glycol ratio can decrease the material's mechanical properties, such as tensile strength, flexural strength, and modulus. The material may become softer and more easily deformed, failing to meet the mechanical performance requirements of lithium-ion battery films. Additionally, an excessively low spirocyclic glycol ratio may lower the thermal decomposition temperature of the modified PET material, increase its coefficient of thermal expansion, and make it more prone to deformation and aging at high temperatures.

[0051] Optionally, the spirocyclic diol includes 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane.

[0052] Optionally, the weather-resistant PET composite material includes, by parts by weight:

[0053] The lithium-ion battery thin film includes:

[0054] Modified PET material: 80-90 parts;

[0055] Inorganic nanoparticles: 5-15 parts;

[0056] Dispersant: 1-3 parts;

[0057] Antioxidant: 0.5 to 2 parts.

[0058] Optionally, the lithium-ion battery film comprises 80 to 90 parts by weight of modified PET material, for example, the modified PET material may be 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90 parts, etc.

[0059] Optionally, modified PET material is a major component of lithium-ion battery films, providing the films with basic mechanical properties, processing performance, and chemical stability. If the amount of modified PET material is too small, the relative content of other components (such as inorganic nanoparticles and additives) in the lithium-ion battery film increases, which may disrupt the continuity and integrity of the film, leading to a decrease in its mechanical properties. Conversely, if the amount of modified PET material is too large, the effects of other components cannot be fully realized, failing to achieve the desired film performance. Furthermore, if the amount of modified PET material is too small, the film viscosity may be too low, leading to molding difficulties and making the product prone to defects; while if the amount of modified PET material is too large, the viscosity may be too high, increasing processing difficulty and costs. Therefore, selecting 80–90 parts of modified PET material allows for reasonable cost control while ensuring sufficient strength and rigidity of the film.

[0060] Optionally, the lithium-ion battery film includes 5 to 15 parts of inorganic nanoparticles by weight, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 parts of inorganic nanoparticles, etc.

[0061] Optionally, inorganic nanoparticles refer to inorganic material particles with a size in the nanometer range. When subjected to external forces, inorganic nanoparticles can effectively transfer and disperse stress, hindering crack propagation, thereby improving the strength, hardness, and toughness of the composite material. If the amount is too small, the reinforcing effect of the nanoparticles is not obvious; if the amount is too large, the nanoparticles are prone to agglomeration, forming stress concentration points, which will reduce the mechanical properties of the composite material. Furthermore, adding 5-15 parts of inorganic nanoparticles to lithium-ion battery films can increase the heat distortion temperature of the material and enhance its dimensional stability under high-temperature environments. At the same time, it can also accelerate heat transfer, improve the heat dissipation performance of the material, and reduce material aging and damage caused by heat accumulation. The lamellar structure or nanoscale dispersion of inorganic nanoparticles can form tortuous channels in the modified PET material matrix, hindering the penetration of small molecules such as gases and liquids. Furthermore, if the amount of inorganic nanoparticles dispersed in lithium-ion battery films is too large, the interaction forces between the nanoparticles will increase, making them prone to agglomeration, resulting in uneven dispersion and affecting the performance and processing quality of the film. A quantity of 5 to 15 parts can ensure performance improvement while achieving uniform dispersion of nanoparticles in the matrix through appropriate processing techniques.

[0062] Optionally, the lithium-ion battery film includes 1 to 3 parts by weight of a dispersant, for example, 1 part, 2 parts, or 3 parts of the dispersant.

[0063] Optionally, in lithium-ion battery films, the main function of dispersants is to improve the dispersion of various additives and fillers in the modified PET matrix, prevent agglomeration between additive and filler particles, and thus improve the performance of the composite material. Dispersant molecules adsorb onto the surface of additive or filler particles, forming an adsorption layer of a certain thickness. When particles approach each other, steric hindrance is generated between the adsorption layers, preventing particle agglomeration and allowing the particles to be uniformly dispersed in the modified PET matrix. If the amount of dispersant is less than 1 part, a complete adsorption layer may not be formed on the surface of the additive particles, resulting in poor dispersion and easy agglomeration of additive particles, affecting the performance of the film. Excessive amounts of dispersant molecules may weaken the interaction between the molecular chains of the modified PET material, destroying the structural integrity of the material and thus reducing the mechanical properties of the lithium-ion battery film. Therefore, 1 to 3 parts of dispersant can form a sufficient adsorption layer on the surface of additive or filler particles, providing effective steric hindrance or electrostatic repulsion, allowing the additive or filler particles to be uniformly dispersed in the modified PET matrix.

[0064] Optionally, the lithium-ion battery film includes 0.5 to 2 parts by weight of antioxidant, for example, 0.5 parts, 0.7 parts, 0.9 parts, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, or 2 parts of antioxidant.

[0065] Optionally, antioxidants refer to substances that can prevent or delay the oxidative degradation of lithium-ion battery films. Antioxidants can inhibit oxidation reactions by scavenging free radicals and decomposing peroxides, thereby extending the lifespan of lithium-ion battery films and maintaining their performance stability. If the amount of antioxidant is less than 0.5 parts, it may not provide sufficient antioxidant capacity and cannot effectively inhibit oxidation reactions, leading to easy oxidative degradation of the lithium-ion battery film during processing and use, resulting in a rapid decline in performance. When the amount of antioxidant is between 0.5 and 2 parts, an effective antioxidant protection system can be formed in the lithium-ion battery film. Antioxidants can effectively scavenge free radicals and decompose peroxides, inhibiting the occurrence of oxidation reactions, thereby significantly improving the antioxidant performance of lithium-ion battery films.

[0066] In one feasible embodiment, the inorganic nanoparticles include at least one of boehmite, silica, and montmorillonite.

[0067] Optionally, inorganic nanoparticles, due to their small size, large specific surface area, and high number of surface atoms, are often added to polymer matrix resins to prepare high-performance composite materials. Adding boehmite nanoparticles to lithium-ion battery films can improve the flame retardant properties of the material. Boehmite undergoes a dehydration reaction at high temperatures, absorbing a large amount of heat and releasing water vapor, diluting the concentration of flammable gases and thus playing a flame-retardant role. Furthermore, nano-sized boehmite particles can form a good interfacial bond with the modified PET matrix, effectively transferring stress and thus enhancing the mechanical properties of the lithium-ion battery film, such as increasing tensile and flexural strength. Adding nano-silica to lithium-ion battery films can significantly improve the mechanical, thermal, and optical properties of the film. From a mechanical perspective, nano-silica particles can fill the gaps between modified PET molecular chains, enhancing the interaction between molecular chains and improving the strength and toughness of the material. In terms of thermal properties, it can increase the heat distortion temperature of the film and enhance the heat resistance of the material; when nano-montmorillonite is dispersed in the modified PET matrix, it can form composite materials with intercalation or exfoliation structures. It can significantly improve the barrier properties of the film, such as preventing the penetration of small molecules like oxygen and water vapor, and extending the film's service life. At the same time, the nanoscale montmorillonite sheets can effectively restrict the movement of modified PET molecular chains, and montmorillonite can also improve the film's mechanical properties and thermal stability.

[0068] In one feasible embodiment, the dispersant includes at least one of polycarboxylate dispersants and polyacrylate dispersants;

[0069] Optionally, the addition of dispersants can prevent particle agglomeration, ensuring uniform and stable dispersion within the matrix resin. The carboxyl groups of polycarboxylate dispersants can be adsorbed onto the surface of inorganic nanoparticles via electrostatic interactions, giving the particle surface a negative charge. Due to the repulsion between like charges, the particles repel each other, thus preventing agglomeration. Furthermore, the polymer chains of polycarboxylate dispersants form an adsorption layer on the particle surface, which acts as a steric hindrance, further preventing particle proximity and agglomeration. Polyacrylate dispersants primarily achieve dispersion through steric hindrance. Their polymer chains adsorb onto the surface of inorganic nanoparticles, forming a relatively thick adsorption layer. When particles approach each other, steric hindrance occurs between the adsorption layers, preventing particle agglomeration. In addition, polyacrylate dispersants can reduce the interfacial tension between the particles and the modified PET matrix, improving the dispersibility and compatibility of the particles in the matrix. Depending on the specific addition of inorganic nanoparticles, at least one most suitable dispersant can be selected to achieve the best dispersion effect. If two dispersants are used at the same time, a synergistic effect may occur, further improving the dispersion effect and making the particles more uniformly and stably dispersed in the PET matrix.

[0070] Optionally, polycarboxylate dispersants include sodium polyacrylate, sodium polymethacrylate, etc.

[0071] Optionally, polyacrylate dispersants include acrylic-acrylate copolymers.

[0072] Optionally, the antioxidant includes at least one of phenolic antioxidants and amine antioxidants.

[0073] Optionally, antioxidants can inhibit oxidation reactions by capturing free radicals and decomposing peroxides, thereby improving the stability and durability of lithium-ion battery films. Phenolic antioxidants primarily react with free radicals generated during oxidation through the reaction of hydrogen atoms on the phenolic hydroxyl group, producing relatively stable phenoxy radicals. Because phenoxy radicals possess a certain degree of stability, they can further react with other free radicals, thus terminating the free radical chain reaction and achieving the purpose of antioxidation. Amine antioxidants primarily react with free radicals through the reaction of hydrogen atoms on the amino group, producing relatively stable amino radicals, which in turn terminate the free radical chain reaction. Furthermore, amine antioxidants can also decompose peroxides, reducing the initiation sources of oxidation reactions.

[0074] Alternatively, phenolic antioxidants may include 2,6-di-tert-butyl-4-methylphenol.

[0075] Optionally, amine antioxidants may include 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (antioxidant KY-405).

[0076] In one feasible embodiment, the thickness of the lithium-ion battery film is 20–200 μm.

[0077] Optionally, the thickness of the lithium-ion battery film can be 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm, etc.

[0078] Optionally, in lithium-ion batteries, an appropriate film thickness can achieve effective isolation. When the film thickness is too low (e.g., less than 20 μm), the mechanical strength and integrity may be insufficient, making the battery prone to breakage during manufacturing, assembly, or use, thus causing safety issues such as overheating, fire, or even explosion. Insufficient film thickness can also lead to punctures caused by tiny particles or impurities inside the battery, affecting the performance of the lithium-ion battery. Furthermore, during the film preparation process, insufficient film thickness can cause residual stress concentration, easily leading to excessive local shrinkage.

[0079] This application provides a method for preparing a lithium-ion battery thin film. The method includes the following steps:

[0080] Step S10: Provide modified PET material, inorganic nanoparticles, dispersant and antioxidant;

[0081] Step S20: The modified PET material, the inorganic nanoparticles, the dispersant, and the antioxidant are melt-co-extruded to obtain a mixture;

[0082] Optionally, the dried modified PET material, inorganic nanoparticles, dispersant, and antioxidant are added to a high-speed mixer in the designed proportions and stirred at 300-500 r / min for 10-15 min at room temperature to ensure thorough and uniform mixing. The mixed material is then added to a twin-screw extruder for melt blending. The melt-blended material is extruded from the extruder die and cooled through a water tank to obtain a mixture. Step S30: The mixture is then formed into sheets.

[0083] Step S40: The sheet is biaxially stretched to obtain a lithium-ion battery film.

[0084] Optionally, biaxial stretching refers to stretching a sheet in two mutually perpendicular directions (usually longitudinal and transverse). Biaxial stretching can orient the polymer chains in both directions, thereby improving the mechanical properties, transparency, and dimensional stability of the film. The sheet is preheated and stretched in the longitudinal direction, typically using stretching rollers or a stretching machine. The stretch ratio is 3–5 times, and the temperature is 90–100°C. The longitudinally stretched sheet is then stretched in the transverse direction, typically using a tenter frame. The transverse stretch ratio is 3–5 times, and the temperature is 100–110°C. The biaxially stretched film is then heat-set at a high temperature to eliminate internal stress and stabilize the film's dimensions and properties. The heat-setting temperature is 180–220°C. After heat setting, the film is cooled by cooling rollers and then wound up to obtain the finished lithium-ion battery film.

[0085] In one feasible embodiment, the melt co-extrusion temperature is 260–290°C.

[0086] Optionally, the temperature of melt co-extrusion can be 260℃, 265℃, 270℃, 275℃, 280℃, 285℃, or 290℃.

[0087] Optionally, a temperature range of 260–290°C allows the mixture to fully melt, ensuring good flowability, facilitating extrusion processing, and preventing unmelted particles from affecting film quality. Simultaneously, this temperature prevents excessive thermal degradation of PET, maintaining its performance stability. For adhesive layer materials, this temperature allows them to reach a suitable molten state, ensuring good adhesion to PET and maintaining chemical stability. Furthermore, this temperature range meets equipment operating requirements, reduces thermal damage, and makes process parameters easier to control, helping to ensure film thickness uniformity and dimensional accuracy.

[0088] To enable those skilled in the art to clearly understand the details and operations of the above embodiments of this application, and to demonstrate the significant improvement in the performance of the flame-retardant resin materials and preparation methods of the embodiments of this application, the above technical solutions are illustrated below through multiple embodiments.

[0089] Example 1

[0090] Terephthalic acid, ethylene glycol, and spirocyclic glycol were added to a reaction vessel and stirred and heated to obtain the first reactant, wherein the ratio of terephthalic acid: ethylene glycol: spirocyclic glycol was 1:1.8:0.05. After adding zinc acetate, the temperature was raised to 260℃ and reacted for 1.5 h to obtain the modified PET material.

[0091] Mixture 1 was obtained by melt-blending and extruding 80 parts of modified PET material, 6 parts of nano silica particles, 2 parts of polycarboxylate and 1 part of phenolic antioxidant, and then cooling.

[0092] The mixture was melt-co-extruded to obtain a lithium-ion battery film at a melt co-extruded temperature of 285°C, and sheet 1 was obtained.

[0093] The lithium-ion battery film 1 is prepared by biaxial stretching of sheet 1.

[0094] Example 2

[0095] The steps are the same as in Example 1, except that: terephthalic acid: ethylene glycol: spirocyclic glycol = 1:2:0.1, to prepare lithium-ion battery film 2.

[0096] Example 3

[0097] The steps are the same as in Example 1, except that: terephthalic acid: ethylene glycol: spirocyclic glycol = 1:2.2:0.15, to obtain lithium-ion battery film 3.

[0098] Comparative Example 1

[0099] PET is prepared by adding terephthalic acid and ethylene glycol into a reaction vessel, stirring and heating.

[0100] 80 parts PET, 6 parts nano silica particles, 2 parts polycarboxylate and 1 part phenolic antioxidant were melt-blended and extruded, and then cooled to obtain mixture 4.

[0101] The mixture was melt-co-extruded to obtain a lithium-ion battery film at a melt co-extruded temperature of 285°C, and sheet 4 was obtained.

[0102] The lithium-ion battery film 4 is prepared by biaxial stretching of sheet 1.

[0103] Comparative Example 2

[0104] Terephthalic acid, ethylene glycol, and 1,4-cyclohexanediethanol were added to a reaction vessel and stirred and heated to obtain the first reactant, wherein the ratio of terephthalic acid: ethylene glycol: 1,4-cyclohexanediethanol was 1:1.8:0.05. After adding zinc acetate, the temperature was raised to 260℃ and reacted for 1.5 h to obtain modified PET.

[0105] 80 parts of modified PET, 6 parts of nano silica particles, 2 parts of polycarboxylate and 1 part of phenolic antioxidant were melt-blended and extruded, and then cooled to obtain mixture 5;

[0106] The mixture was melt-co-extruded to obtain a lithium-ion battery film at a melt co-extruded temperature of 285°C, and a sheet 5 was obtained.

[0107] The lithium-ion battery film 5 is prepared by biaxial stretching of sheet 1.

[0108] Comparative Example 3

[0109] The steps are the same as in Example 1, except that: terephthalic acid: ethylene glycol: spirocyclic glycol = 1:1.8:0.2, to obtain lithium-ion battery film 6.

[0110] Comparative Example 4

[0111] The steps are the same as in Example 1, except that no nano-silica particles are added to obtain the lithium-ion battery film 7.

[0112] Furthermore, to verify the progressiveness of the embodiments of this application, the following performance tests were performed on each embodiment and comparative example:

[0113] 1. High temperature resistance

[0114] The lithium-ion battery films prepared in Examples 1-4 and Comparative Examples 1-3 were baked at 80°C for 3 hours, and the color difference and surface morphology of the lithium-ion battery films were observed. If the color difference of the film is small and the surface morphology is intact, it indicates good high-temperature resistance, and is marked as √; otherwise, it is marked as ×. The test results are shown in Table 1.

[0115] 2. Electrolyte resistance

[0116] The lithium-ion battery films prepared in Examples 1-4 and Comparative Examples 1-3 were placed in electrolyte and immersed at 80°C for 4 hours. The color difference, corrosion, and turbidity of the electrolyte were observed compared to before immersion. A small color difference in the film indicates excellent high-temperature resistance and electrolyte resistance, marked as √; if the electrolyte becomes turbid, it indicates poor electrolyte resistance, marked as ×. The test results are shown in Table 1.

[0117] The electrolyte is a mixed solution of dimethyl carbonate, ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1:1:1, with lithium hexafluorophosphate added and mixed evenly.

[0118] The test results are shown in Table 1 below:

[0119] Table 1

[0120]

[0121]

[0122] As shown in Table 1, Examples 1-3 are examples of lithium-ion battery films prepared using modified PET materials in this application. Table 1 shows that, compared to Comparative Example 1 using unmodified PET and Comparative Example 2 using other modified PET materials, these films exhibited better high-temperature resistance and electrolyte resistance. This indicates that the introduction of the spirocyclic structure enhances the rigidity and heat resistance of the modified PET material. Furthermore, the dense network formed by the spirocyclic structure improves the electrolyte resistance of the modified PET material. Compared to Comparative Example 4 without added nano-silica particles, Examples 1-3 improved the high-temperature resistance and electrolyte resistance of the lithium-ion battery films by adding nano-silica particles. Moreover, the proportion of the spirocyclic material used for modification in the modified PET material needs to be within a suitable range. Compared to Comparative Example 3 with an excessively high proportion, the films prepared in Examples 1-3 exhibited better high-temperature resistance and electrolyte resistance. The lithium-ion battery films prepared in this application have excellent high-temperature resistance and electrolyte resistance.

[0123] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the patent protection scope of this application.

Claims

1. A lithium-ion battery thin film, characterized in that, The lithium-ion battery film comprises modified PET material, inorganic nanoparticles, dispersant, and antioxidant; The modified PET material is obtained through the following steps: Terephthalic acid, ethylene glycol and spirocyclic glycol are mixed and heated to obtain the first reactant, wherein the molar ratio of terephthalic acid: ethylene glycol: spirocyclic glycol is 1:(1.8-2.2):(0.05-0.15). A catalyst is added to the first reactant, and the temperature is increased to carry out a co-condensation reaction to obtain the modified PET material.

2. The lithium-ion battery thin film as described in claim 1, characterized in that, The spirocyclic diol includes 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-oxospiro[5.5]undecane.

3. The lithium-ion battery thin film as described in claim 1, characterized in that, The lithium-ion battery film comprises, by weight parts: Modified PET material: 80-90 parts; Inorganic nanoparticles: 5-15 parts; Dispersant: 1-3 parts; Antioxidant: 0.5 to 2 parts.

4. The lithium-ion battery thin film as described in claim 1, characterized in that, The inorganic nanoparticles include at least one of boehmite, silica, and montmorillonite.

5. The lithium-ion battery thin film as described in claim 1, characterized in that, The dispersant includes at least one of polycarboxylate dispersants and polyacrylate dispersants; And / or, the antioxidant includes at least one of phenolic antioxidants and amine antioxidants.

6. The lithium-ion battery thin film as described in claim 1, characterized in that, The thickness of the lithium-ion battery film is 20~200μm.

7. A method for preparing a lithium-ion battery thin film, characterized in that, The method is used to prepare a lithium-ion battery thin film as described in any one of claims 1 to 6, and the method includes the following steps: We provide modified PET materials, inorganic nanoparticles, dispersants, and antioxidants. The modified PET material, the inorganic nanoparticles, the dispersant, and the antioxidant were melt-co-extruded to obtain a mixture. The mixture is then formed into a sheet; The sheet is biaxially stretched to obtain a lithium-ion battery film.

8. The method for preparing the lithium-ion battery thin film as described in claim 7, characterized in that, The temperature of the melt co-extrusion is 260–290°C.

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