Separator and preparation method therefor, and electrochemical device

Abstract

The present disclosure belongs to the technical field of separators. Disclosed are a separator and a preparation method therefor, and an electrochemical device. The separator comprises a bulk membrane and a composite material layer arranged on at least one side surface of the bulk membrane, wherein the composite material layer comprises inorganic particles and an inorganic binder; and the inorganic binder comprises a silicate, i.e., M2O·nSiO2, and / or an aluminum sol, i.e., a(Al2O3·mH2O)·bHx·cH2O, and / or a silica sol, i.e., SiO2·dH2O, where M comprises at least one of Na, K and Li, 1≤n≤4, Al2O3·mH2O is hydrated alumina, Hx is a peptizing agent, b is less than a, c and m, and 1≤d≤4. The separator not only has a relatively good peel strength, puncture strength, wettability and air permeability, but also has a good ionic conductivity, and can be used stably under high-temperature conditions for a long time; therefore, an electrochemical device comprising the separator can also work safely and efficiently under high-temperature conditions.

Description

A separating membrane, its preparation method, and an electrochemical device thereof

[0001] Cross-reference to related applications

[0002] This disclosure claims priority to Chinese Patent Application No. 202411709925.3, filed on November 27, 2024, entitled "A separating membrane and its preparation method and electrochemical device", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of separator technology, and more specifically, to a separator, a method for preparing the same, and an electrochemical device thereof. Background Technology

[0004] Lithium-ion batteries mainly consist of four parts: a positive electrode, a negative electrode, an electrolyte, and a separator. The separator is primarily used to separate the positive and negative electrodes of the electrochemical device, preventing direct contact between them, and to provide a transport path for lithium ions while blocking the passage of electrons to prevent short circuits. The performance of the separator has a significant impact on the interface structure and internal resistance of the electrochemical device, and directly affects its electrochemical performance and safety.

[0005] Currently, lithium-ion battery separators need to possess both high thermal stability and electrolyte wettability. Traditional battery separators typically use polyethylene (PE) or polypropylene (PP) as the matrix. These types of separators lack sufficient heat resistance; they soften and deform above 130℃ (PE) or 160℃ (PP), easily melting and shrinking, leading to battery short circuits. Under conditions of overcharging, over-discharging, rapid charging and discharging, abuse, or high temperatures, the separator is easily melted and ruptured, causing internal short circuits and thermal runaway, resulting in battery fires or even explosions. This makes it difficult to meet the stringent safety requirements of high-capacity, high-energy-density electrochemical devices. Furthermore, polyethylene and polypropylene have low surface energy and poor wettability with the electrolyte, meaning the separator pores cannot be completely filled with electrolyte, which also affects the performance of the electrochemical device.

[0006] Currently, heat resistance is usually improved by coating the base film surface with inorganic particles (such as Al2O3), but organic adhesives (such as polyacrylate) are commonly used, which have problems such as electrolyte swelling and high-temperature decomposition, leading to coating powdering and peeling.

[0007] Therefore, how to provide a separator that can effectively suppress thermal runaway and ensure that electrochemical devices can still operate safely and efficiently under high temperature conditions has become a current research hotspot, aiming to improve the heat resistance of the separator while maintaining high bonding strength.

[0008] In view of this, this disclosure is hereby made. Summary of the Invention

[0009] The purpose of this disclosure is to provide a separating membrane, a method for preparing the same, and an electrochemical device thereof, in order to solve or improve the aforementioned technical problems.

[0010] This disclosure can be implemented as follows:

[0011] In a first aspect, this disclosure provides a separation membrane, which includes a body membrane and a composite material layer disposed on at least one surface of the body membrane; the composite material layer includes inorganic particles and an inorganic binder.

[0012] Inorganic binders include components with the chemical formula M2O·nSiO2 and / or the chemical formula a(Al2O3·mH2O)·bH x Aluminum sol of ·cH2O, wherein M includes at least one of Na, K and Li, 1≤n≤4; Al2O3·mH2O is hydrated aluminum oxide, H x For the adhesive solvent, b is less than a, c, and m.

[0013] In a second aspect, this disclosure provides a separating membrane, the separating membrane comprising a body membrane and a composite material layer disposed on at least one surface of the body membrane; the composite material layer comprising inorganic particles and an inorganic binder;

[0014] The inorganic binder comprises silicates with the chemical formula M2O·nSiO2, and / or silicates with the chemical formula a(Al2O3·mH2O)·bH x Aluminum sol with the chemical formula ·cH2O, and / or silica sol with the chemical formula SiO2·dH2O, wherein M includes at least one of Na, K, and Li, 1≤n≤4; Al2O3·mH2O is hydrated alumina, H x For the adhesive solvent, b is less than a, c, and m; 1 ≤ d ≤ 4.

[0015] In an optional embodiment, the dry weight of the inorganic binder is 1% to 35% of the mass of the inorganic particles in the composite material layer, preferably 1% to 20%, and more preferably 1% to 12%.

[0016] In an optional embodiment, the aluminum sol and the silica sol are in particulate form before film formation, with a particle size of 5nm-400nm.

[0017] In an optional embodiment, the dry weight of the component with the chemical formula M2O·nSiO2 is 1% to 35% of the mass of inorganic particles in the composite material layer.

[0018] In an optional embodiment, the aluminum sol is essentially a colloidal solution formed by dispersing positively charged nanoscale alumina hydrate particles in acidic water. The acid contains H+. +Ions adsorb onto the surface of alumina hydrate particles, giving them a positive charge. These particles with the same positive charge generate electrostatic repulsion, which overcomes van der Waals attraction, preventing them from approaching each other and aggregating, thus allowing the sol to exist stably for a long time.

[0019] In an optional embodiment, the aluminum sol has at least one of the following characteristics:

[0020] Feature 1: The particle size range of aluminum sol is 5nm to 200nm;

[0021] Feature 2: The pH value of aluminum sol is 2-7;

[0022] Feature 3: The dry weight of the aluminum sol is 1%-20% of the mass of the inorganic particles in the composite material layer;

[0023] Feature 4: In the chemical formula of the aluminum sol, a is 1-5, b is 1-3, c is 1-5, and m is 1-7;

[0024] Feature 5: The adhesive solvent is one of hydrochloric acid, sulfuric acid and nitric acid.

[0025] In an optional embodiment, the silica sol is essentially a colloidal solution formed by dispersing negatively charged nano-sized silica particles in alkaline water. The silanol groups on the particle surface dissociate in the water, making the particles negatively charged. These particles with the same positive charge generate electrostatic repulsion between them, thereby overcoming van der Waals attraction, preventing them from approaching each other and aggregating, and allowing the sol to exist stably for a long time.

[0026] The silica sol has at least one of the following characteristics:

[0027] Feature 6: The particle size range of the silica sol is 5nm to 200nm;

[0028] Feature 7: The pH value of the silica sol is 7 to 11.

[0029] In an optional embodiment, the inorganic particles have at least one of the following characteristics:

[0030] Feature 8: The inorganic particles include at least one of kaolin, boehmite, clay, molecular sieve, Al2O3, SiO2, BaSO4, BaO, MgO, CuO, LiAlO2, ZrO2, Fe2O3, BaTiO3, α-V2O5, PbTiO3, CaSiO3, titanium dioxide, LiF, MgF2, BaF2, TiB2, Mg(OH)2, MoS2, SiC, Si3N4, and carbon nanotubes; preferably, at least one of boehmite, Al2O3, SiO2, and BaTiO3 is included.

[0031] Feature 9: The average particle size of the inorganic particles is 10 nm to 5 μm, preferably 11 nm to 4.9 μm.

[0032] In an optional embodiment, the thickness of the separator is 2.3 μm to 48 μm, preferably 3 to 45 μm, and more preferably 12 μm to 35 μm.

[0033] In optional embodiments, the thickness of the bulk film is 2 μm to 40 μm, preferably 3 μm to 39 μm, and more preferably 12 μm to 28 μm.

[0034] In an optional embodiment, the bulk membrane includes at least one of a polymer membrane and a ceramic membrane.

[0035] In an optional embodiment, the polymer membrane includes at least one of polyamide membrane, polyimide membrane, polyolefin membrane, polyacrylonitrile membrane, cellulose membrane, polyester membrane, nanofiber nonwoven membrane, and aramid membrane.

[0036] In an optional embodiment, the thickness of the composite material layer is 0.3 μm to 9 μm, preferably 0.4 μm to 8 μm, and more preferably 1.2 μm to 5 μm.

[0037] Thirdly, this disclosure provides a method for preparing an isolation membrane as described in any of the foregoing embodiments, comprising the following steps: coating at least one side surface of the bulk membrane with a composite material layer slurry containing an inorganic binder and inorganic particles, and drying.

[0038] In an optional embodiment, the composite layer slurry has at least one of the following characteristics:

[0039] Feature 10: The solid content of the composite material layer slurry is 2% to 50%, preferably 6% to 48%, and more preferably 20% to 43%;

[0040] Feature 11: The viscosity of the composite material layer slurry is 10cp to 1000cp, preferably 20cp to 350cp, and more preferably 20cp to 100cp.

[0041] In an optional embodiment, drying is carried out at 50°C to 70°C for 2 to 5 minutes.

[0042] Fourthly, this disclosure provides an electrochemical device comprising the isolation membrane of any of the foregoing embodiments.

[0043] Fifthly, this disclosure also provides a separator membrane, the separator membrane comprising a body membrane and a composite material layer disposed on at least one surface of the body membrane; the composite material layer contains crystals formed by an inorganic binder, the crystals comprising at least one of plate-like crystals and spherical crystals and needle-like whiskers.

[0044] In an optional embodiment, the diameter of the needle-like whiskers in the isolation film provided in the fifth aspect above is 40 nm to 900 nm, preferably 50 nm to 600 nm.

[0045] In an optional embodiment, in the isolation membrane provided by the fifth aspect above, some crystals together form a whisker group, and the remaining crystals are located between inorganic particles.

[0046] In an optional embodiment, the longest length of the whisker group in the isolation film provided in the fifth aspect above is 1 μm to 20 μm, preferably 5 μm to 11 μm.

[0047] In an optional embodiment, the whisker clusters in the isolation membrane provided by the fifth aspect above are in the form of "grass clumps".

[0048] In an optional embodiment, in the isolation membrane provided by the fifth aspect above, the longest distance between any two points on the surface of the plate-like crystal is 1 μm to 3 μm.

[0049] In an optional embodiment, in the isolation membrane provided by the fifth aspect above, the longest distance between any two points on the surface of the spherical crystal is 1 μm to 3 μm.

[0050] In an optional embodiment, the isolation membrane provided in the fifth aspect above further contains inorganic particles with an average particle size of 10 nm to 5 μm, preferably inorganic particles with an average particle size of 11 nm to 4.9 μm.

[0051] In an optional embodiment, the thickness of the isolation membrane provided in the fifth aspect above is 2.3 μm to 48 μm, preferably 3 to 45 μm, and more preferably 12 μm to 35 μm.

[0052] In an optional embodiment, the thickness of the composite material layer in the isolation membrane provided in the fifth aspect above is 0.3 μm to 9 μm, preferably 0.4 μm to 8 μm, and more preferably 1.2 μm to 5 μm.

[0053] In an optional embodiment, the thickness of the body film in the isolation membrane provided in the fifth aspect above is 2 μm to 40 μm, preferably 3 μm to 39 μm, and more preferably 12 μm to 28 μm.

[0054] The beneficial effects of this disclosure include:

[0055] This disclosure involves providing a composite material layer comprising an inorganic binder and inorganic particles on at least one surface of the bulk membrane. The inorganic particles exhibit excellent wettability to organic electrolytes, particularly to carbonate solvents with high dielectric constants that are difficult to wet by polyolefin membranes. Furthermore, the inorganic particles possess excellent temperature resistance, non-flammability, and refractory properties, which contribute to the membrane's superior temperature resistance and mechanical properties. Combined with the use of an inorganic binder, this ensures the membrane's stable and long-lasting operation under high-temperature conditions, thereby enabling the electrochemical device containing this membrane to operate safely and efficiently at high temperatures.

[0056] For example, the use of the aforementioned inorganic binder can avoid the problems of inorganic particles shedding and falling off in the composite material layer that are prone to occur when using organic adhesives in the prior art. The main reasons for these problems are: organic adhesives have significant swelling problems in electrolytes, and once they absorb electrolyte, they can easily cause a decline in cell performance. In addition, organic adhesives are unstable at high temperatures and are prone to melting or decomposition, causing their bonding effect with inorganic ceramic particles to fail.

[0057] Based on this, this disclosure eliminates the traditionally used organic adhesive in the composite material layer, instead employing an inorganic binder. Inorganic binders are less prone to swelling in the electrolyte, are low in cost, easy to operate, provide excellent bonding, and are environmentally friendly. Furthermore, inorganic binders overcome the instability of organic adhesives at high temperatures, exhibiting superior high-temperature resistance.

[0058] In other words, the separator provided in this disclosure has superior peel strength, puncture strength, wettability and air permeability, as well as good ionic conductivity, and can be used stably and for a long time under high temperature conditions, thereby enabling electrochemical devices containing the separator to operate safely and efficiently under high temperature conditions.

[0059] The method for preparing the separator membrane disclosed herein is simple, easy to scale up for industrial production, and has good prospects for industrialization. Attached Figure Description

[0060] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0061] Figure 1 is a schematic diagram of the structure of the aluminum sol provided in this disclosure;

[0062] Figure 2 is a SEM image of a certain region of the surface of the isolation membrane (denoted as 2NSO5-22) prepared in Example 3;

[0063] Figure 3 is a magnified view of the SEM results in the first box in Figure 2 (in order from top to bottom);

[0064] Figure 4 is a magnified view of the SEM results in the second box in Figure 2 (in order from top to bottom);

[0065] Figure 5 is a SEM image of another region of the surface of the isolation membrane (denoted as 2NSO5-22) prepared in Example 3;

[0066] Figure 6 is a SEM image of a certain region of the surface of the isolation membrane (denoted as 2NSO5-30) prepared in Example 5;

[0067] Figure 7 is a magnified view of the SEM results at the box in Figure 6;

[0068] Figure 8 is a magnified view of the SEM results at the box in Figure 7;

[0069] Figure 9 is a SEM image of a certain region of the surface of the isolation membrane (denoted as 2NSO10-22) prepared in Example 6;

[0070] Figure 10 is a SEM image of a certain region of the surface of the isolation membrane (denoted as 2NSO20-22) prepared in Example 7;

[0071] Figure 11 is a SEM image of another region of the surface of the isolation membrane prepared in Example 7;

[0072] Figure 12 is a SEM image of a certain region of the surface of the isolation membrane (denoted as NSO5-22) prepared in Example 11;

[0073] Figure 13 is a magnified view of the SEM results at the box in Figure 12;

[0074] Figure 14 is a SEM image of another region of the surface of the isolation membrane prepared in Example 11;

[0075] Figure 15 is a magnified view of the SEM results at the boxed area in Figure 14;

[0076] Figure 16 is a cross-sectional SEM image of the isolation membrane prepared in Example 4 after being kept at 130°C for 1 hour;

[0077] Figure 17 is a cross-sectional SEM image of the isolation membrane prepared in Example 3 after being kept at 200°C for 1 hour;

[0078] Figure 18 is a SEM image of a certain area of ​​the surface of the isolation membrane prepared in Example 20. Detailed Implementation

[0079] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions in the embodiments of this disclosure 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.

[0080] The following provides a detailed description of the separator membrane, its preparation method, and its applications.

[0081] This disclosure provides a separation membrane comprising a body membrane and a composite material layer coated on at least one surface of the body membrane; the composite material layer comprises an inorganic binder and inorganic particles.

[0082] The phrase "at least one side" can be understood as: a composite material layer can be provided on any one side of the body membrane, or a composite material layer can be provided on both sides of the body membrane.

[0083] Inorganic particles in the composite material layer have a high specific surface area (e.g., 10 m²). 2 / g~88m 2 The inorganic particles exhibit good hydrophilicity and excellent wettability in organic electrolytes, particularly carbonate solvents with high dielectric constants that are difficult to wet with polyolefin films. Furthermore, the inorganic particles possess excellent temperature resistance, non-flammability, and refractory properties, which are beneficial for imparting good temperature resistance and mechanical properties to the separator. The inorganic binder used in the composite material layer of this disclosure not only overcomes the instability of organic adhesives at high temperatures, exhibiting excellent high-temperature resistance, but also features low swelling in electrolytes, low cost, ease of operation, good bonding effect, and environmental friendliness.

[0084] In this disclosure, the inorganic binder includes components with the chemical formula M2O·nSiO2, and / or components with the chemical formula a(Al2O3·mH2O)·bH x Aluminum sol with the chemical formula ·cH2O, and / or silica sol with the chemical formula SiO2·dH2O, wherein M includes at least one of Na, K, and Li, 1≤n≤4; Al2O3·mH2O is hydrated alumina, H x For a gel solvent, b is less than a, c, and m, and 1 ≤ d ≤ 4.

[0085] That is, the inorganic binder includes the components with the chemical formula M2O·nSiO2 and the components with the chemical formula a(Al2O3·mH2O)·bH xAt least one of aluminum sol with the chemical formula ·cH2O and silica sol with the chemical formula SiO2·dH2O. Among them, the component with the chemical formula M2O·nSiO2 can also be called a silicate with the chemical formula M2O·nSiO2.

[0086] In some alternative embodiments, the inorganic binder includes components with the chemical formula M2O·nSiO2, but does not contain components with the chemical formula a(Al2O3·mH2O)·bH x Aluminum sol with the chemical formula ·cH2O and silica sol with the chemical formula SiO2·dH2O.

[0087] In some alternative embodiments, the inorganic binder comprises the chemical formula a(Al₂O₃·mH₂O)·bH x It is an aluminum sol with the chemical formula ·cH2O, but does not contain any components with the chemical formula M2O·nSiO2 or silica sol with the chemical formula SiO2·dH2O.

[0088] In some alternative embodiments, the inorganic binder comprises silica sol with the chemical formula SiO2·dH2O, but does not contain components with the chemical formula M2O·nSiO2 or a(Al2O3·mH2O)·bH2O. x Aluminum sol of ·CH2O.

[0089] In some alternative embodiments, the inorganic binder may simultaneously comprise a component with the chemical formula M2O·nSiO2 and a component with the chemical formula a(Al2O3·mH2O)·bH x In the case of aluminum sol with the chemical formula M2O·nSiO2 and a(Al2O3·mH2O)·bH2O, the composition is as follows: x The dry weight ratio of the aluminum sol of CH2O is 1:5 to 5:1.

[0090] In some alternative embodiments, the inorganic binder may simultaneously comprise a component with the chemical formula M2O·nSiO2 and a silica sol with the chemical formula SiO2·dH2O, wherein the dry weight ratio of the component with the chemical formula M2O·nSiO2 and the silica sol with the chemical formula SiO2·dH2O is 1:5 to 5:1.

[0091] In some alternative embodiments, the inorganic binder may simultaneously include the chemical formula a(Al₂O₃·mH₂O)·bH x Aluminum sol with the chemical formula ·cH2O and silica sol with the chemical formula SiO2·dH2O are both present. In this case, the chemical formula is a(Al2O3·mH2O)·bH2O. x The dry weight ratio of aluminum sol with the chemical formula ·cH2O and silica sol with the chemical formula SiO2·dH2O is 1:5 to 5:1.

[0092] In some alternative embodiments, the inorganic binder may simultaneously include components with the chemical formula M2O·nSiO2 and a(Al2O3·mH2O)·bH x Aluminum sol with the chemical formula ·cH2O and silica sol with the chemical formula SiO2·dH2O are present. At this point, the composition of the chemical formula M2O·nSiO2 and the composition of the chemical formula a(Al2O3·mH2O)·bH2O are also present. x The dry weight ratio of aluminum sol with the chemical formula ·cH2O and silica sol with the chemical formula SiO2·dH2O is 1-2:1-2:1-2.

[0093] The above-mentioned chemical formula M2O·nSiO2 is an inorganic compound composed of metal cations and polymer silicate anions.

[0094] In this disclosure, the cations in M2O·nSiO2 are selected from at least one of Na, Li, and K, which are relatively lightweight and have small ionic radii. This not only improves the energy density and ion mobility of the material but also avoids the hazards to the battery or the environment caused by using magnetic elements such as Fe, Cr, or Ni, or other heavy metal elements. In some typical embodiments, M is at least one of Na and Li.

[0095] In this disclosure, n in M2O·nSiO2 represents the number of SiO2 units in the polymer anion, called the modulus, and n = SiO2 / M2O (molar ratio). For example, the value of n can be 1, 1.5, 2, 2.5, 3, 3.5 or 4.

[0096] The inorganic binder used in this disclosure has a silicon atom outer electron configuration of 3s. 2 3p 2 It exhibits the property of heating and dehydrating polymerization. As the temperature rises, the water in the liquid inorganic binder evaporates, silicate anions aggregate to form a film, producing more silanol groups. The condensation between adjacent silanol groups forms Si-O-Si bonds. The remaining water molecules continue to catalyze the dehydration and condensation of silanol groups, and the viscosity of the adhesive continuously increases, eventually forming a three-dimensional network structure connected by Si-O-Si bonds. This structure has strong adhesive properties.

[0097] The modulus n in inorganic binders affects their bonding performance. A higher modulus results in stronger adhesion, easier curing into a film, and increased heat resistance of the release liner and peel strength of the composite layer. However, an excessively high modulus n not only increases the viscosity and reduces workability of the inorganic binder but also lowers the cationic proportion, leading to decreased ionic conductivity. Therefore, this disclosure specifically uses inorganic binders with n values ​​between 1 and 4.

[0098] In this disclosure, aluminum sol is essentially a colloidal solution in which charged alumina particles are uniformly dispersed in water. A schematic diagram of the aluminum sol structure is shown in Figure 1, where the core is composed of hydrated alumina. The bonding mechanism of aluminum sol is a multi-stage, continuous, and synergistic process. In the initial stage, the nanoscale hydrated alumina particles in the aluminum sol, with their abundant surface hydroxyl groups, are physically adsorbed onto the surface of the base film or inorganic particles through van der Waals forces and hydrogen bonds, achieving initial anchoring. As the drying process proceeds, water evaporation generates capillary forces, driving the particles closer together and rearranging them, thereby increasing the density of the composite layer and the contact area with the substrate, enhancing the initial bonding strength. The most critical process occurs during the heat treatment stage: the system first gels to form a three-dimensional network connected by hydrogen bonds, and then, under high temperature conditions, adjacent hydroxyl groups on the particle surface undergo dehydration condensation reactions to generate strong Al-O-Al bridge bonds. This chemical change transforms physical adsorption into stable chemical bonding, forming a high-strength, high-temperature-resistant inorganic oxide network. Ultimately, through mechanical interlocking and strong hydrogen bonding, a durable and robust bond is achieved between inorganic particles and between the composite material layer and the base film.

[0099] In this disclosure, silica sol is essentially a colloidal solution in which nano-sized silica (SiO2) particles are stably dispersed in water. Its bonding mechanism differs from the polymerization reaction of silicates and the condensation reaction of alumina sol, mainly relying on the combined effect of the physical stacking of nanoparticles and surface chemical condensation.

[0100] After the slurry is coated, as the moisture initially evaporates, the SiO2 nanoparticles in the silica sol move closer together due to the weakening of Brownian motion, resulting in initial aggregation through van der Waals forces. As the drying process continues, the strong capillary forces generated by further moisture evaporation drive these nanoparticles to tightly pack around the inorganic particles and onto the substrate surface, forming an initial bonding network primarily based on physical interactions. During this process, a dehydration condensation reaction occurs between the numerous exposed silanol groups (-Si-OH) on the particle surface, forming strong Si-O-Si chemical bonds. This strengthens the physically packed particle network into a robust, three-dimensionally cross-linked silica solid framework. This framework, through its large specific surface area and abundant surface silanol groups, generates strong hydrogen bonds and chemical bonds with the inorganic particles and the substrate surface, ultimately achieving strong adhesion.

[0101] In some optional embodiments, the particle size range of the aluminum sol can be 5nm to 200nm, such as 5nm, 10nm, 20nm, 50nm, 80nm, 100nm, 120nm, 150nm, 180nm or 200nm, or other values ​​within the range of 5nm to 200nm.

[0102] In some alternative implementations, the pH value of the aluminum sol can be 2 to 7, such as 2, 3, 4, 5, 6 or 7, or other values ​​within the range of 2 to 7.

[0103] In some optional embodiments, the dry weight of the aluminum sol is 1%-20% of the mass of the inorganic particles in the composite material layer; such as 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, etc., or other values ​​in the range of 1% to 20%, preferably 1% to 12%.

[0104] In some alternative embodiments, the chemical formula of the aluminum sol is 1-5, b is 1-3, c is 1-5, and m is 1-7.

[0105] In some alternative embodiments, the adhesive solvent is one of hydrochloric acid, sulfuric acid, and nitric acid.

[0106] In this disclosure, the chemical formula of the silica sol is SiO2·dH2O, and the particle size range of the silica sol is 5nm to 200nm; for example, it can be 5nm, 10nm, 20nm, 50nm, 80nm, 100nm, 120nm, 150nm, 180nm or 200nm, or other values ​​in the range of 5nm to 200nm.

[0107] The pH value of silica sol is 7 to 11, for example, it can be any one of 7, 8, 9, 10 or 11 or any range between two of them.

[0108] In this disclosure, the composite material layer contains crystals formed by an inorganic binder; some of the crystals together form a whisker group, the crystals including at least needle-shaped whiskers, and the remaining crystals are located between the inorganic particles.

[0109] In some alternative embodiments, the crystal further includes at least one of plate-like crystals and spherical crystals.

[0110] Specifically, in some schemes, the crystal has only needle-like whiskers; in some schemes, the crystal has both needle-like whiskers and plate-like crystals; in some schemes, the crystal has both needle-like whiskers and spherical crystals; and in some schemes, the crystal has needle-like whiskers, plate-like crystals, and spherical crystals.

[0111] The diameter of the whiskers is 40nm to 900nm. In some preferred embodiments, the diameter of the whiskers can be 50nm to 600nm, such as 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, or 600nm, or any value or range within the 50nm to 600nm range.

[0112] The longest length of the aforementioned whisker group is 1 μm to 20 μm. In some preferred embodiments, the longest length of the whisker group can be 5 μm to 11 μm, such as 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, or 11 μm, or any value or range within the range of 5 μm to 11 μm.

[0113] In this paper, the diameter of whiskers and the longest length of whisker clusters can be measured using scanning electron microscopy. Whiskers are a special crystal form, fibrous crystals grown from high-purity raw materials. The diameter of a whisker can be understood as its width relative to its length. The diameter of other crystal shapes can be understood as the maximum value obtained by comparing the shortest distances between any two points on the crystal surface.

[0114] In some alternative implementations, the whisker clusters can appear as "grass clumps".

[0115] In some alternative implementations, the longest distance between any two points on the surface of the plate-like crystal is 1 μm to 3 μm.

[0116] In some alternative implementations, the longest distance between any two points on the surface of the spherical crystal is 1 μm to 3 μm.

[0117] In the present disclosure, during the drying and dehydration process of the separator membrane, the inorganic binder in the composite material layer crystallizes. The crystallization stage is the hardening process of the inorganic binder. At this time, the gel transforms into crystals. In some areas, the crystals gradually grow, interpenetrate between the composite material layers, and overlap and cross-attach, transforming the gel into a three-dimensional, firmly bonded, dense "grass-like" whisker cluster. In other areas, the whiskers are located (e.g., uniformly dispersed) between the inorganic particles, interlacing to form a network support. The whiskers in the composite material layer are tightly bonded to the inorganic particles, forming a "reinforced concrete" structure.

[0118] The heat resistance of the isolation membrane in this disclosure is related to the whiskers grown in the composite material layer. The "grass-like" whisker clusters are "rooted" in the composite material layer and "pin" the moving shrinkage interface at high temperatures, playing a "pinning effect" in the isolation membrane, which can effectively inhibit the shrinkage of the isolation membrane. In addition, the dispersed high-temperature resistant inorganic whiskers form a network, giving the composite material layer a continuous self-supporting characteristic. This allows the composite material layer to maintain good integrity at high temperatures and when the bulk membrane melts, without breaking or pulverizing, exhibiting excellent geothermal protection effect.

[0119] In some alternative embodiments, the dry weight of the inorganic binder is 1% to 35% of the mass of the inorganic particles in the composite material layer, such as 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, or 35%, etc., or other values ​​in the range of 1% to 35%, preferably 1% to 20%, more preferably 1% to 12%.

[0120] In some optional embodiments, the aluminum sol and silica sol are in particulate form before film formation, with a particle size of 5nm-400nm. Examples include 5nm, 10nm, 30nm, 50nm, 70nm, 80nm, 90nm, 100nm, 120nm, 140nm, 160nm, 180nm, 200nm, 220nm, 240nm, 260nm, 280nm, 300nm, 320nm, 340nm, 360nm, 380nm, or 400nm, or other values ​​within the 10nm-400nm range, preferably 10nm-200nm.

[0121] In some optional embodiments, the dry weight of the component with the chemical formula M2O·nSiO2 is 1% to 35% of the mass of inorganic particles in the composite material layer, such as 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, or 35%, or other values ​​within the range of 1% to 35%. In some preferred embodiments, the dry weight of the component with the chemical formula M2O·nSiO2 is 1% to 20% of the mass of inorganic particles in the composite material layer; in some more preferred embodiments, the dry weight of the component with the chemical formula M2O·nSiO2 is 1% to 12% of the mass of inorganic particles in the composite material layer.

[0122] The higher the content of the component with the chemical formula M2O·nSiO2 in the composite material layer, the larger the whiskers contained in the composite material layer. Furthermore, the modulus of the component with the chemical formula M2O·nSiO2 also affects the size of the whiskers; the higher the modulus, the larger the diameter of both the "grass-like" whisker clusters and the dispersed whiskers, resulting in better heat resistance of the corresponding separator. In addition, the content range of the component with the chemical formula M2O·nSiO2 mentioned above avoids the problem of insufficient addition leading to low bonding strength, while avoiding the problem of excessive addition causing rapid agglomeration of slurry particles, resulting in phenomena such as incomplete coating, uneven composite layer thickness, shrinkage, and edge curling.

[0123] By combining inorganic binders with the above characteristics with inorganic particles, the inorganic particles can act as curing agents for the inorganic binders. The inorganic particles and inorganic binders can form a network structure through hydrogen bonds, van der Waals forces, and their own bonding, achieving a good bonding effect. Even under high temperature conditions, they will not melt or decompose, maintaining their own size and structure well, which is beneficial to improving the performance of the battery.

[0124] In some optional embodiments, when the component with the chemical formula M2O·nSiO2 accounts for 5% of the mass of inorganic particles in the composite material layer, the diameter of the whiskers is 50nm to 415nm, such as 50nm, 70nm, 80nm, 90nm, 100nm, 120nm, 140nm, 160nm, 180nm, 200nm, 220nm, 240nm, 260nm, 280nm, 300nm, 320nm, 340nm, 360nm, 380nm, 400nm, or 415nm, or any value or range within the range of 50nm to 415nm.

[0125] In some optional embodiments, when the component with the chemical formula M2O·nSiO2 accounts for 20% of the mass of inorganic particles in the composite material layer, the diameter of the whiskers is 300nm to 600nm, such as 300nm, 320nm, 340nm, 360nm, 380nm, 400nm, 420nm, 440nm, 460nm, 480nm, 500nm, 520nm, 540nm, 560nm, 580nm, or 600nm, etc., or any value or range within the range of 300nm to 600nm.

[0126] In some alternative embodiments, the inorganic particles may, by way of example but not limitation, include at least one of the following: kaolin, boehmite, clay, molecular sieves (such as ZSM-5), Al2O3 (including α-type, β-type, and / or γ-type), SiO2, BaSO4, BaO, MgO, CuO, LiAlO2, ZrO2, Fe2O3, BaTiO3, α-V2O5, PbTiO3, CaSiO3, titanium dioxide (including TiO2, rutile, and / or anatase), LiF, MgF2, BaF2, TiB2, Mg(OH)2, MoS2, SiC, Si3N4, and carbon nanotubes (CNTs). In some preferred embodiments, the inorganic particles may include at least one of boehmite, Al2O3, SiO2, and BaTiO3.

[0127] In some optional embodiments, the average particle size of the inorganic particles can be from 10 nm to 5 μm, such as 10 nm, 20 nm, 50 nm, 80 nm, 100 nm, 200 nm, 500 nm, 800 nm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm, or any value or range within the range of 10 nm to 5 μm. In some preferred embodiments, the average particle size of the inorganic particles is from 11 nm to 4.9 μm.

[0128] In some optional embodiments, the body membrane includes at least one of a polymer membrane and a ceramic membrane. The polymer membrane may, by way of example but not limitation, include at least one of a polyamide membrane, a polyimide membrane, a polyolefin membrane, a polyacrylonitrile membrane, a cellulose membrane, a polyester membrane, and an aramid membrane. The polyolefin may, by way of example, include polyethylene, polypropylene, polyvinylidene fluoride, and polytetrafluoroethylene, etc., and the polyester may, by way of example, include polyethylene terephthalate, etc. Furthermore, other body membranes may be used as needed.

[0129] In some alternative embodiments, the bulk film can be a single layer, a double layer, or a multilayer (number of layers > 2). When the number of bulk film layers is ≥ 2, the thickness of each bulk film layer can be equal or unequal, and the material of each bulk film layer can be the same or different. When the number of bulk film layers is ≥ 2, the layers can be bonded together by lamination and / or co-extrusion.

[0130] In some optional embodiments, the thickness of the bulk film can be from 2 μm to 40 μm, such as 2 μm, 2.5 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm, or 40 μm, or any value or range within the range of 2 μm to 40 μm. In some preferred embodiments, the thickness of the bulk film is from 3 μm to 39 μm; in some more preferred embodiments, the thickness of the bulk film is from 12 μm to 28 μm.

[0131] In some optional embodiments, the thickness of the composite material layer can be 0.3 μm to 9 μm, such as 0.3 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, or 9 μm, or any value or range within the range of 0.3 μm to 9 μm. In some preferred embodiments, the thickness of the composite material layer is 0.4 μm to 8 μm; in some more preferred embodiments, the thickness of the composite material layer is 1.2 μm to 5 μm.

[0132] If the thickness of the composite material layer is greater than 9 μm, it will easily lead to increased coating difficulty, and at the same time, the electrolyte retention rate and the mass of the separator will increase, resulting in a decrease in the energy density of the battery. If the thickness of the composite material layer is less than 0.3 μm, it will easily lead to a decrease in the thermal dimensional stability, electrolyte retention rate and capacity retention rate of the separator.

[0133] With increasing inorganic binder content and composite layer thickness, the heat resistance and peel strength of the release liner both show an improving trend. This trend generally applies to three types of inorganic binder systems: silicate, silica sol, and alumina sol. The common mechanism is as follows: Firstly, increasing the composite layer thickness is equivalent to increasing the total amount of inorganic binder and inorganic particles per unit area, enhancing the overall structural density and thermal stability, and effectively suppressing the shrinkage of the base film at high temperatures. Secondly, increasing the amount of inorganic binder strengthens the interaction force between it and the inorganic particles, improving the cohesive strength and interfacial bonding of the coating.

[0134] In terms of electrochemical performance, the introduction of the composite material layer significantly improves the wettability of the separator. The bulk membrane (such as PE) is hydrophobic, resulting in poor electrolyte retention and absorption rates; however, the abundant porous structure and the good hydrophilicity of the inorganic particles in the composite material layer jointly promote rapid electrolyte penetration and storage. This improved wettability not only shortens the battery electrolyte filling time but also enhances the electrolyte retention capacity under operating conditions, which is beneficial for ion transport. Furthermore, increasing the thickness of the composite material layer increases electrolyte retention, while the inorganic binder itself contributes to ion conduction channels; both work together to improve ionic conductivity. However, it should be noted that an excessively thick coating can prolong the ion migration path, potentially leading to a decrease in ionic conductivity.

[0135] Specifically, different types of adhesives also differ in their mechanisms of action and performance:

[0136] Silicates (M2O·nSiO2): During drying and heat treatment, silicate anions gradually polymerize to form a three-dimensional network structure dominated by Si-O-Si bonds, achieving the coating and bonding of inorganic particles. The higher the modulus (n), the greater the degree of polymerization, the stronger the bonding force, and the corresponding improvement in heat resistance.

[0137] Silica sol (SiO2·dH2O): Its bonding mechanism relies on the close packing of nano-SiO2 particles and the condensation reaction of surface silanol groups. The particles are bonded together by van der Waals forces, hydrogen bonds, and Si-O-Si bonds, forming a stable framework with high porosity. This structure provides good bonding strength while also exhibiting excellent electrolyte wettability and ion transport channels.

[0138] Aluminum sol (a(Al2O3·mH2O)·bH x• cH2O): Its bonding process is mainly based on the physical adsorption and chemical bridging of nano-hydrated alumina particles. During drying and heat treatment, the hydroxyl groups on the particle surface undergo dehydration condensation to form an Al-O-Al bridging structure with high bond energy and strong thermal stability, which endows the coating with excellent high-temperature stability and is particularly suitable for applications with stringent requirements for heat resistance.

[0139] It is particularly important to note that regardless of the type of inorganic binder used, its dosage must be controlled within a reasonable range. Excessive content will lead to increased slurry viscosity, a greater tendency for particle agglomeration, and reduced slurry stability, which in turn will cause process problems such as uneven coating and missed coating, thus affecting the overall performance.

[0140] In summary, the overall performance of separators can be optimized by adjusting the dosage and coating thickness of silicates, silica sols, and alumina sols, each with its own characteristics in terms of bonding mechanism and performance emphasis. This disclosure achieves a balance between heat resistance, bonding strength, and ionic conductivity by rationally selecting and compounding different inorganic binders, thus meeting the diverse needs of battery design and application.

[0141] In some optional embodiments, the total thickness of the separator can be from 2.3 μm to 48 μm, such as 2.3 μm, 2.5 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, or 48 μm, or any value or range within the range of 2.3 μm to 48 μm. In some preferred embodiments, the total thickness of the separator is from 3 μm to 45 μm; in some more preferred embodiments, the total thickness of the separator is from 12 μm to 35 μm.

[0142] As mentioned above, the separator provided in this disclosure has superior peel strength, puncture strength, wettability and air permeability, as well as good ionic conductivity. It can be used stably and for a long time under high temperature conditions, thereby enabling electrochemical devices containing the separator to operate safely and efficiently under high temperature conditions.

[0143] Accordingly, this disclosure also provides a method for preparing the above-mentioned isolation membrane, comprising the following steps: coating at least one side surface of the bulk membrane with a composite material layer slurry containing an inorganic binder and inorganic particles, and drying.

[0144] The coating can be performed by, but is not limited to, coating methods such as extrusion transfer coating or dip coating, blade coating, electrostatic spraying, gravure or microgravure coating, as long as the composite material layer slurry can be coated on the surface of the bulk film.

[0145] In some optional embodiments, the solid content of the composite layer slurry can be 2% to 50%, such as 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%, or any value or range within the 2% to 50% range. In some preferred embodiments, the solid content of the composite layer slurry is 6% to 48%; in some more preferred embodiments, the solid content of the composite layer slurry is 20% to 43%.

[0146] In some optional embodiments, the viscosity of the composite material layer slurry can be from 10 cp to 1000 cp, such as 10 cp, 20 cp, 50 cp, 80 cp, 100 cp, 200 cp, 500 cp, 800 cp, or 1000 cp, or any value or range within the range of 10 cp to 1000 cp. In some preferred embodiments, the viscosity of the composite material layer slurry is from 20 cp to 350 cp; in some more preferred embodiments, the viscosity of the composite material layer slurry is from 20 cp to 100 cp.

[0147] The aforementioned composite material layer slurry is obtained by mixing the raw materials for preparing the composite material layer with a solvent, and the solvent can be water, for example.

[0148] The raw materials for preparing the composite material layer include inorganic binders and inorganic particles, and may further include at least one of additives such as dispersants, wetting agents, thickeners and flame retardants.

[0149] The dispersant may include, for example, at least one of polyacrylamide, sodium hexametaphosphate, and methylpentanol.

[0150] Wetting agents may include, for example, at least one of ethanol, propylene glycol, glycerin, polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, fatty acid ester sulfate, and vinyltriethoxysilane.

[0151] Thickeners may include, for example, carboxymethyl cellulose (CMC).

[0152] Flame retardants may include, for example, at least one of brominated flame retardants, ammonium phosphate, ammonium hydroxide, alumina trihydrate, and phosphate esters.

[0153] The dry weight of the dispersant can be 0.2% to 5% of the mass of the inorganic particles, such as 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, or any value or range within the range of 0.2% to 5%.

[0154] The dry weight of the wetting agent can be 0.05% to 5% of the mass of the inorganic particles, such as 0.05%, 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, or any value or range within the range of 0.05% to 5%.

[0155] The dry weight of the thickener can be 0.5% to 5% of the mass of the inorganic particles, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, or any value or range within the range of 0.5% to 5%.

[0156] The dry weight of the flame retardant can be 1% to 5% of the mass of the inorganic particles, such as 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, or any value or range within the range of 1% to 5%.

[0157] In some alternative embodiments, the drying temperature can be set at 50°C to 70°C (e.g., 50°C, 55°C, 60°C, 65°C, or 70°C) for 2 to 5 minutes (e.g., 2 minutes, 2.5 minutes, 3 minutes, 3.5 minutes, 4 minutes, 4.5 minutes, or 5 minutes).

[0158] Drying conditions affect crystal formation. At the start of drying, water in the adhesive evaporates, anions aggregate to form a film, generating numerous silanol groups. Water molecules in the adhesive rearrange, catalyzing the condensation between adjacent silanol groups to form Si-O-Si bonds. As temperature increases or drying time extends, remaining water molecules continue to catalyze the dehydration and condensation of silanol groups. Subsequently, localized reactions occur on the surface of the dispersed anhydrous compound particles, forming a gel with a significant exothermic effect. The crystallization stage is the hardening process of the inorganic binder. At this point, the gel transforms into crystals. The crystals gradually grow and overlap, cross-attaching and transforming the gel into a firmly bonded, dense three-dimensional solid, accompanied by a small amount of heat release.

[0159] If the drying temperature is too high, the whiskers may not grow densely enough, resulting in a loose crystal structure and weakening its mechanical properties. If the drying temperature is set too low, it will not only cause a slow crystal growth rate but also require extending the drying cycle to ensure the separator membrane reaches the predetermined moisture standard, reducing production efficiency. In addition, high-temperature drying will increase the energy consumption of the drying equipment, negatively impacting cost control.

[0160] If the drying time is too long, it will cause the whisker size to increase abnormally, and it will also be accompanied by an increase in energy consumption. This is not only detrimental to cost control, but also hinders the improvement of production efficiency. If the drying time is too short, it is difficult to ensure that the moisture content in the separator meets the production standards.

[0161] In addition, this disclosure also provides an electrochemical device (such as a lithium-ion battery) that includes the aforementioned separator membrane.

[0162] Specifically, the electrochemical device includes a positive electrode, a negative electrode, and a separating membrane, which separates the positive and negative electrodes. Electrochemical devices with this separating membrane offer good safety in use.

[0163] The features and performance of this disclosure will be further described in detail below with reference to embodiments.

[0164] Example 1

[0165] This embodiment provides a separator with a total thickness of 13 μm, which includes a porous polyethylene (PE) body film with a thickness of 9 μm and composite material layers coated on both sides of the body film (each side of the composite material layer has a thickness of 2 μm).

[0166] The composite material layer slurry used to prepare the composite material layer is obtained by dissolving the raw materials in water. The solid content of the composite material layer slurry is 26.3%, and the viscosity is about 20 cp.

[0167] The raw materials, by mass, include 100 parts inorganic particles (alumina powder with an average particle size of 500 nm), 5 parts inorganic binder (Na2O·3SiO2), 1.5 parts thickener (CMC), 0.5 parts dispersant (polyacrylamide), and 0.1 parts wetting agent (vinyltriethoxysilane).

[0168] The preparation method of the above-mentioned separator membrane includes:

[0169] Step 1: According to the above-mentioned amount of raw materials, add inorganic particles, dispersant, and thickener to 300 parts of deionized water, stir at 2000 rpm for 4 hours to obtain the first slurry; ball mill the first slurry in a ball mill jar at a ball milling rate of 60 rpm for 24 hours to obtain the second slurry.

[0170] Step 2: Filter the second slurry, add inorganic binder and wetting agent to the filtered second slurry, and stir at 500 rpm for 1 hour to obtain composite material layer slurry.

[0171] Step 3: The above composite material layer slurry is evenly coated on both sides of the body film on a coating machine, and vacuum dried at 60°C for 5 minutes to obtain a separation film with composite material layers on both sides of the body film.

[0172] Example 2

[0173] The difference between this embodiment and Embodiment 1 is that the amount of inorganic binder used is 2 parts, and the inorganic binder is Na2O·2SiO2.

[0174] Example 3

[0175] The difference between this embodiment and Embodiment 2 is that the amount of inorganic binder used is 5 parts.

[0176] Example 4

[0177] The difference between this embodiment and embodiment 3 is that a 2μm composite material layer is only provided on one side of the body film.

[0178] Example 5

[0179] The difference between this embodiment and Embodiment 4 is that the thickness of the composite material layer is 3 μm.

[0180] Example 6

[0181] The difference between this embodiment and Embodiment 2 is that the amount of inorganic binder used is 10 parts.

[0182] Example 7

[0183] The difference between this embodiment and Embodiment 2 is that the amount of inorganic binder used is 20 parts.

[0184] Example 8

[0185] The difference between this embodiment and embodiment 3 is that the inorganic binder is Na2O·1.5SiO2.

[0186] Example 9

[0187] The difference between this embodiment and embodiment 8 is that a 2μm composite material layer is only provided on one side of the body film.

[0188] Example 10

[0189] The difference between this embodiment and embodiment 9 is that a 3μm composite material layer is only provided on one side of the body film.

[0190] Example 11

[0191] The difference between this embodiment and embodiment 3 is that the inorganic binder is Na2O·SiO2.

[0192] Example 12

[0193] The difference between this embodiment and Embodiment 11 is that the amount of inorganic binder used is 10 parts.

[0194] Example 13

[0195] The difference between this embodiment and Embodiment 1 is that the inorganic binder is Na2O·4SiO2.

[0196] Example 14

[0197] The difference between this embodiment and Embodiment 1 is that the inorganic binder is K2O·3SiO2.

[0198] Example 15

[0199] The difference between this embodiment and Embodiment 1 is that the inorganic binder is Li2O·3SiO2.

[0200] Example 16

[0201] The difference between this embodiment and Embodiment 1 is that the thickness of the main body film is 2 μm, and the thickness of the composite material layer on each side of the main body film is 0.3 μm.

[0202] The solid content of the composite layer slurry is 2%, and the viscosity of the composite layer slurry is 10 cp.

[0203] The inorganic particles are SiO2; the dry weight of Na2O·3SiO2 is 1% of the mass of inorganic particles in the composite material layer; the dry weight of the thickener is 0.5% of the mass of inorganic particles; the dry weight of the dispersant is 0.2% of the mass of inorganic particles; the dry weight of the flame retardant (ammonium phosphate) is 1% of the mass of inorganic particles; and the dry weight of the wetting agent is 0.1% of the mass of inorganic particles.

[0204] The drying temperature is 50℃ and the drying time is 5 minutes.

[0205] Example 17

[0206] The difference between this embodiment and Embodiment 1 is that the thickness of the main body film is 40 μm, and the thickness of the composite material layer on each side of the main body film is 9 μm.

[0207] The solid content of the composite layer slurry is 50%, and the viscosity of the composite layer slurry is 1000 cp.

[0208] The inorganic particles are BaTiO3; the dry weight of Na2O·3SiO2 is 35% of the mass of inorganic particles in the composite layer; the dry weight of the thickener is 5% of the mass of inorganic particles; the dry weight of the dispersant is 5% of the mass of inorganic particles; the dry weight of the flame retardant (alumina trihydrate) is 5% of the mass of inorganic particles; and the dry weight of the wetting agent is 5% of the mass of inorganic particles.

[0209] The drying temperature is 70℃ and the drying time is 2 minutes.

[0210] Example 18

[0211] The difference between this embodiment and Embodiment 1 is that the dry weight of Na2O·3SiO2 is 12% of the mass of inorganic particles in the composite material layer. The inorganic particles are boehmite.

[0212] Example 19

[0213] The difference between this embodiment and Embodiment 1 is that the thickness of the composite material layer is 12 μm.

[0214] Example 20

[0215] This embodiment provides a separator with a total thickness of 13 μm, which includes a porous polyethylene (PE) body film with a thickness of 9 μm and composite material layers coated on both sides of the body film (each side of the composite material layer has a thickness of 2 μm).

[0216] The composite material layer slurry used to prepare the composite material layer is obtained by dissolving the raw materials in water. The solid content of the composite material layer slurry is 26.3%, and the viscosity is about 20 cp.

[0217] The raw materials, by mass, include 100 parts of inorganic particles (alumina powder with an average particle size of 500 nm), 5 parts of inorganic binder (2(Al2O3·3H2O)·HCl·2H2O, with a particle size of 100 nm), 1 part of thickener (CMC), 0.5 parts of dispersant (polyacrylamide), and 0.1 parts of wetting agent (vinyltriethoxysilane).

[0218] The preparation method of the above-mentioned separator membrane includes:

[0219] Step 1: According to the above-mentioned amount of raw materials, add inorganic particles, dispersant, and thickener to 300 parts of deionized water, stir at 2000 rpm for 4 hours to obtain the first slurry; ball mill the first slurry in a ball mill jar at a ball milling rate of 60 rpm for 24 hours to obtain the second slurry.

[0220] Step 2: Filter the second slurry, add inorganic binder and wetting agent to the filtered second slurry, and stir at 500 rpm for 1 hour to obtain composite material layer slurry.

[0221] Step 3: The above composite material layer slurry is evenly coated on both sides of the body film on a coating machine, and vacuum dried at 60°C for 5 minutes to obtain a separation film with composite material layers on both sides of the body film.

[0222] Example 21

[0223] The difference between this embodiment and Embodiment 20 is that a 2μm composite material layer is only provided on one side of the base film.

[0224] Example 22

[0225] The difference between this embodiment and Embodiment 20 is that the thickness of the composite material layer on each side is 3 μm.

[0226] Example 23

[0227] The difference between this embodiment and embodiment 20 is that the amount of inorganic binder used is 1 part.

[0228] Example 24

[0229] The difference between this embodiment and Embodiment 20 is that the amount of inorganic binder used is 10 parts.

[0230] Example 25

[0231] The difference between this embodiment and Embodiment 20 is that the amount of inorganic binder used is 20 parts.

[0232] Example 26

[0233] The difference between this embodiment and Embodiment 20 is that the inorganic binder is aluminum sol, with the chemical formula 3(Al2O3·5H2O)·HCl·2H2O.

[0234] Example 27

[0235] The difference between this embodiment and Embodiment 20 is that the inorganic binder is aluminum sol, with the chemical formula 2(Al2O3·2H2O)·HCl·4H2O and a particle size of 30nm. The amount of inorganic binder used is 8 parts.

[0236] Example 28

[0237] The difference between this embodiment and Embodiment 27 is that the chemical formula of the aluminum sol is Al2O3·2H2O·HNO3·3H2O, and the particle size is 80nm.

[0238] Example 29

[0239] The difference between this embodiment and Embodiment 28 is that the particle size of the aluminum sol is 5 nm.

[0240] Example 30

[0241] The difference between this embodiment and Embodiment 28 is that the particle size of the aluminum sol is 150 nm.

[0242] Example 31

[0243] The difference between this embodiment and embodiment 28 is that the amount of inorganic binder is 15 parts, and a 2μm composite material layer is only provided on one side of the bulk film.

[0244] Example 32

[0245] The difference between this embodiment and Embodiment 20 is that the inorganic binder is silica sol with the chemical formula SiO2·H2O and a particle size of 20nm. The amount of inorganic binder used is 6 parts.

[0246] Example 33

[0247] The difference between this embodiment and embodiment 32 is that the chemical formula of the silica sol is SiO2·3H2O and the particle size is 100nm.

[0248] Example 34

[0249] The difference between this embodiment and embodiment 33 is that the particle size of the silica sol is 10 nm.

[0250] Example 35

[0251] The difference between this embodiment and embodiment 33 is that the particle size of the silica sol is 200 nm.

[0252] Example 36

[0253] The difference between this embodiment and embodiment 33 is that the amount of inorganic binder used is 12 parts, and the thickness of the composite material layer is 3 μm.

[0254] Example 37

[0255] The difference between this embodiment and Embodiment 20 is that the inorganic binder is a mixture of sodium silicate (Na2O·3SiO2) and aluminum sol (2(Al2O3·H2O)·HCl·4H2O) in a mass ratio of 2:1, with a total amount of 6 parts.

[0256] Example 38

[0257] The difference between this embodiment and embodiment 37 is that the inorganic binder is a mixture of lithium silicate (Li2O·3SiO2) and silica sol (SiO2·2H2O) in a mass ratio of 1:2, with a total amount of 6 parts.

[0258] Example 39

[0259] The difference between this embodiment and embodiment 37 is that the inorganic binder is a mixture of silica sol (SiO2·H2O) and aluminum sol (Al2O3·2H2O·HNO3·3H2O) in a mass ratio of 1:1, with a total amount of 8 parts.

[0260] Example 40

[0261] The difference between this embodiment and embodiment 37 is that the inorganic binder is a mixture of aluminum sol (3(Al2O3·5H2O)·Hx·2H2O) and silica sol (SiO2·2H2O) in a mass ratio of 1:1, with a total amount of 7 parts.

[0262] Example 41

[0263] The difference between this embodiment and embodiment 37 is that the inorganic binder is a mixture of sodium silicate (K2O·3SiO2), silica sol (SiO2·3H2O) and aluminum sol (2(Al2O3·H2O)·HCl·4H2O) in a mass ratio of 1:2:1, with a total amount of 10 parts.

[0264] Comparative Example 1

[0265] The difference between this comparative example and Example 1 is that no composite material layer is provided on the surface of the bulk film.

[0266] Comparative Example 2

[0267] The difference between this comparative example and Example 1 is that the inorganic binder is replaced with polymethyl methacrylate adhesive.

[0268] Comparative Example 3

[0269] The difference between this comparative example and Example 1 is that the inorganic binder is replaced with a polyacrylamide adhesive.

[0270] Comparative Example 4

[0271] The difference between this comparative example and Example 1 is that the inorganic binder is Na2O·5SiO2.

[0272] Comparative Example 5

[0273] The difference between this comparative example and Example 1 is that the dry weight of the inorganic binder is 40% of the mass of the inorganic particles in the composite material layer.

[0274] Test case

[0275] (1) The performance of the separators obtained in Examples 1 to 41 and Comparative Examples 1 to 5 was tested, and the performance results are shown in Table 1 and Table 2.

[0276] Performance testing methods are as follows:

[0277] ① Shrinkage Rate: The release film was cut into multiple 120mm × 100mm (length × width) pieces along the longitudinal (MD) and transverse (TD) directions. An A4 sheet of paper was placed over the release film, and the films were placed in an oven at 130℃, 150℃, and 200℃ for 1 hour each. The shrinkage in each direction was measured, and the shrinkage percentage was calculated. The shrinkage rates in Table 1 are based on the average values ​​obtained from three measurements in the MD and TD directions.

[0278] ② Peel Strength: The peel strength between the composite material layer and the base film was tested using a universal tensile testing machine. A sampler was used to cut the composite material layer release film into 150mm × 30mm (length × width) sample strips, which were then adhered to double-sided adhesive tape on the test plate. A 200mm × 20mm (length × width) transparent tape was then adhered above the sample strips. A cylindrical pressure roller was then used to press the release film naturally in the same direction. When the release film was a single-sided composite material layer coating, the corresponding base film side faced down, and the composite material layer side faced up. One end of the transparent tape was peeled off from the composite material layer of the release film until the adhesion length between the transparent tape and the composite material layer was 80mm. The free end of the transparent tape was folded in half, and the free end of the transparent tape and the test plate were clamped onto upper and lower clamps respectively. In the same environment, a tensile testing machine was used to continuously peel the film at a tensile speed of 100mm / min until the composite material layer and the base film were completely separated. The peel strength of the composite material layer of the release film was directly read and recorded.

[0279] ③ Air permeability and puncture strength: refer to the standard GBT36363-2018; thickness is measured using a Mal film thickness gauge.

[0280] ④ Water contact angle: The contact angle was measured using a contact angle measuring instrument in accordance with the GB / T 30693-2014 standard.

[0281] ⑤ Electrolyte wettability: The wettability of the separator is characterized by measuring the size change of the droplets formed at 5s and 5min after adding electrolyte droplets to the surface of the separator. Specifically, the droplet size is represented by the sum of the longest distances in the MD and TD directions divided by 2. The wettability is represented by the difference between the droplet sizes at 5s and 5min and then divided by 2.

[0282] ⑥ Ionic conductivity: Cut 5 isolation membranes that match the resistance test mold. Immerse the isolation membranes in a 1 mol / L lithium hexafluorophosphate (LiPF6) electrolyte. The solvent in this electrolyte is ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1. Keep the solution sealed and soak for 2 hours. Use an electrochemical workstation at 25℃, 0.01Hz~1×10⁻⁶ Hz. 6 Electrochemical impedance spectroscopy was tested and recorded within a frequency range of Hz. The slope and linearity of the curve were calculated by plotting the number of separator layers on the x-axis and the separator resistance on the y-axis. When the linearity was greater than 0.99, the slope (k) was taken as the separator impedance value. The ionic conductivity of the separator was calculated using the formula σ = d / ks, where σ is the ionic conductivity of the separator, d is the separator thickness, k is the separator impedance value, and s is the area of ​​the separator used during testing.

[0283] ⑦ Slurry particle size: The particle size of the prepared composite material layer slurry was tested using a Malvern MS3000 laser particle size analyzer.

[0284] ⑧. Slurry stabilization time: Particle size D measured by Malvern MS3000 laser particle size analyzer 50 Time greater than 2μm.

[0285] Table 1 Performance Test Results

[0286] Table 2 Performance Test Results (Continued)

[0287] As shown in Tables 1 and 2, the embodiments of this disclosure use inorganic binders instead of traditional organic adhesives. By controlling the amount and modulus of the inorganic binder, the prepared separator membrane exhibits high ionic conductivity, good wettability, excellent high-temperature resistance, and a complete membrane structure. In some preferred embodiments, with a composite material layer thickness of 4 μm and a separator membrane thickness not exceeding 13 μm, the shrinkage rate after heat treatment at 200°C for 1 hour is less than 3% without powdering. This indicates that the adhesive has not failed, significantly improving the safety of the separator membrane and meeting usage requirements.

[0288] Comparing Examples 2-7, 9-10, and 20-25, it can be seen that as the amount of inorganic binder and the thickness of the composite material layer increase, the heat resistance of the separator improves and the peel strength of the composite material layer increases. This is because the increased amount of inorganic binder intensifies the interaction between the inorganic binder and the inorganic particles, resulting in a tighter bond between them. The increased thickness of the composite material layer is equivalent to increasing the content of inorganic binder and inorganic particles per unit area, thereby increasing the bonding strength between the inorganic particles and the bulk membrane, inhibiting the shrinkage of the separator at high temperatures, and improving heat resistance.

[0289] Furthermore, compared to Comparative Example 1, the ionic conductivity of the separator provided in the above embodiments is significantly increased, and this increase is accompanied by an increase in the amount of inorganic binder and the thickness of the composite material layer. This can be attributed to the fact that the bulk membrane (PE) is difficult to wet, resulting in poor electrolyte retention and absorption rates. The highly developed porous structure of the inorganic composite material layer and the excellent hydrophilic properties of the inorganic particles significantly increase the wettability of the separator (contact angle decreases from 114° to below 14°). Good wettability of the separator not only effectively shortens the electrolyte filling time during battery assembly but also improves electrolyte retention, facilitating effective ion transport during battery operation. Moreover, a thicker composite material layer results in greater electrolyte retention and absorption, and a higher content of inorganic binder increases the content of conductive ions, all of which improve the ionic conductivity of the separator. However, excessively thick composite material layers can increase ion transport distance, thereby reducing ionic conductivity. In addition, when the content of inorganic binder is too high, not only is it difficult to coat the composite material layer slurry, but it also causes the composite material layer slurry to agglomerate rapidly, the particle size to increase significantly, the stability of the composite material layer slurry to deteriorate, and phenomena such as incomplete coating of the composite material layer.

[0290] A comparison of Examples 3, 8, 11, and 12 shows that, for the same thickness and inorganic binder content, the heat resistance of the separator and the peel strength of the composite layer increase with the increase of the inorganic binder modulus. However, the increased modulus reduces the cation content, resulting in a slight decrease in ionic conductivity. Furthermore, Example 3, containing 5 parts Na₂O·2SiO₂, exhibits a lower shrinkage rate than Example 12, containing 10 parts Na₂O·SiO₂ at the same temperature, indicating that the inorganic binder modulus has a significant impact on the heat resistance of the separator.

[0291] As can be seen from Example 1, Comparative Examples 4-5, and Example 19, an excessively high modulus (such as in Comparative Example 4) can actually reduce heat resistance, ionic conductivity, and slurry stability. Higher adhesive content results in larger slurry particle sizes, shorter stabilization times, and beyond a certain amount (such as in Comparative Example 5), can cause incomplete coating, leading to a sharp deterioration in performance. While increasing thickness improves heat resistance, it also increases air permeability, reduces ionic conductivity, and decreases the volumetric energy density of the battery (as in Example 19).

[0292] This indicates that the modulus and amount of inorganic binder, as well as the thickness of the composite material layer, all affect the performance of the separator. If the conditions are not set properly, the performance of the separator will be reduced.

[0293] As can be seen from Examples 20 to 32, the separator using aluminum sol as an inorganic binder exhibits extremely excellent high-temperature resistance. Even under extreme conditions of 200°C, its shrinkage rate is generally less than 2% (as in Examples 20, 27-30), significantly better than the sodium silicate system under the same conditions. This is attributed to the formation of a more robust and heat-resistant inorganic network by the aluminum sol during heating. Simultaneously, the aluminum sol system also maintains good hydrophilicity and ionic conductivity, with water contact angles all below 8.5°, electrolyte wettability greater than 3.2 mm, and ionic conductivity comparable to the preferred sodium silicate system (as in the comparison between Example 20 and Example 1).

[0294] Comparing Examples 20 with Examples 23-25 ​​reveals that, similar to the sodium silicate system, the amount of alumina sol significantly affects performance. Too low a dosage (Example 23, 1 part) leads to insufficient bond strength and decreased heat resistance; while within the dosage range of 5 to 20 parts (Examples 20, 24, 25), as the dosage increases, peel strength increases, slurry particle size increases, and stabilization time shortens, but its heat resistance remains at a high level. This indicates that alumina sol provides reliable thermal stability over a wide dosage range.

[0295] As can be seen from Examples 32 to 36, the separator membrane using silica sol as an inorganic binder has the most similar overall performance to the sodium silicate system, exhibiting low shrinkage, high ionic conductivity, and excellent hydrophilicity. This indicates that different types of silicon-based inorganic binders (silicates, silica sols) can all play similar core roles in constructing lithium battery separator composite material layers.

[0296] In particular, as can be seen from Examples 37 to 41, the combined use of different types of inorganic binders can produce a synergistic effect, thereby obtaining a separator with more balanced or superior performance. For example, Example 37 combines sodium silicate with alumina sol, which exhibits better heat resistance than a single sodium silicate system, while its slurry stability is superior to a high-volume single alumina sol system. Example 41 further combines silicate, silica sol, and alumina sol, exhibiting the lowest shrinkage rate at all test temperatures (MD / TD of only 1.1% / 1.3% at 200℃), while key indicators such as peel strength and ionic conductivity are also at excellent levels. This demonstrates that by carefully designing a composite binder system, it is possible to simultaneously consider the good film-forming properties and electrochemical performance of silicon-based binders with the excellent heat resistance of aluminum-based binders, achieving a "compensating for each other's shortcomings" effect.

[0297] Compared to Comparative Examples 2 and 3, the release films obtained from all examples using inorganic binders with the same amount of organic adhesive and composite layer thickness as those two comparative examples exhibited higher heat resistance, peel strength, and ionic conductivity.

[0298] (2) Scanning electron microscopy (SEM) observation of the isolation membranes obtained in the embodiments of this disclosure revealed that the composite material layer of the isolation membranes prepared in the embodiments of this disclosure contains crystals. Some crystals collectively form whisker clusters resembling "grass clumps," while the remaining crystals are located between inorganic particles. The crystal shapes include needle-like, plate-like, and spherical shapes; the diameter of the whiskers ranges from 40 nm to 900 nm, and the longest length of the whisker clusters ranges from 1 μm to 20 μm. The longest distance between any two points on the surface of plate-like crystals and the longest distance between any two points on the surface of spherical crystals are 1 μm to 3 μm.

[0299] The scanning electron microscope images of the isolation membranes prepared in Examples 3, 5-7 and 11 are used as examples. Please refer to Figures 2 to 15 for details.

[0300] As can be seen from Figures 2 to 15, the composite material layer of the separator contains crystals, and the shapes of the crystals include needle-like, plate-like, and spherical.

[0301] As can be seen from Figures 2 to 8, in some areas of the composite material layer, crystals are interspersed between the composite material layers and overlap and cross each other to form a dense "grass-like" group of crystals that are firmly bonded in three-dimensional space; in other areas, crystals are evenly dispersed among inorganic particles and intersect to form a network support. The crystals between the composite material layers are tightly bonded to the inorganic particles, forming a "reinforced concrete" structure.

[0302] Furthermore, as the amount of inorganic binder increases, the whiskers formed in the composite material layer become larger. In Example 3, with an inorganic binder content of 5 parts, the diameter of the whiskers formed in the composite material layer is approximately 78 nm to 415 nm. In Example 7, with an inorganic binder content of 20 parts, the diameter of the whiskers formed in the composite material layer is approximately 300 nm to 586 nm, and the morphology has also changed compared to Example 3. The whiskers in Example 7 are plate-like or spherical, and the main body size of the whisker group (i.e., the longest length of the whisker) is mostly in the range of 5 μm to 11 μm.

[0303] As can be seen from the SEM images corresponding to Examples 3 and 11, the modulus of the inorganic binder affects the size of the whiskers. The higher the modulus, the larger the "grass-like" whisker clusters and the larger the whisker diameter, and the better the heat resistance of the corresponding separator. This further illustrates the influence of whisker size on the heat resistance of the separator.

[0304] It should be noted that when the ceramic separator is heated, the friction and adhesion between the ceramic layer and the main film layer, the gravity of the ceramic layer, or the pressure during battery assembly will all hinder the shrinkage and movement of the main film, thus maintaining its structural integrity and increasing its stability.

[0305] Figure 16 is a SEM cross-sectional image of the separator membrane of Example 4 after being kept at 130°C for 1 hour. As can be seen from the figure, the pores of the bulk membrane and the ceramic particle layer structure remain intact at this temperature. At higher temperatures, the bulk membrane melts and the pores close, but the ceramic particles embed into the bulk membrane to form an interlocking structure, ensuring the separator membrane structure remains intact. This prevents direct contact between the positive and negative electrodes, inhibits further temperature increases, and thus improves the thermal safety of the separator membrane.

[0306] Figure 17 is a SEM cross-sectional image of the separator membrane of Example 3 after being kept at 200°C for 1 hour. As can be seen from the figure, the molten bulk film is embedded in the voids of the alumina particles, forming an interlocking interface structure. This structure significantly increases the contact area between the alumina particles and the bulk film, ensuring the integrity of the separator membrane structure and thus improving its thermal safety.

[0307] Figure 18 is a SEM image of the separator in Example 20. As can be seen from this image, using 2(Al₂O₃·3H₂O)·H₂O... x • 2H2O, as an inorganic binder, produces a membrane with a complete surface and no whisker-like or clustered crystals.

[0308] (3) Taking Examples 1, 3, 6-8, 12, 20 and 41, and Comparative Examples 1-3 as examples, the separators and positive and negative electrode sheets prepared in the above examples and comparative examples were stacked to form battery cells, and insulation breakdown short-circuit tests were performed. The number of cells that passed the 250V voltage test was counted. The results are shown in Table 3.

[0309] Table 3 Results of Insulation Breakdown Short Circuit Test

[0310] As can be seen from the test results in Table 3, compared with the organic adhesive composite separator with PE as the main film and the PE separator without inorganic composite material layer, the separator provided in this disclosure has better insulation resistance, with a 250V breakdown short circuit test pass rate of over 95%, while the pass rate of the PE separator without inorganic composite material layer is 79%, and the pass rate of the organic adhesive composite separator with PE as the main film is less than 90%.

[0311] This indicates that the separator provided in this disclosure has high insulation performance, which is beneficial to improving the yield of batteries.

[0312] (4) Taking Examples 1, 3, 6-8, 12, 20 and 41 and Comparative Examples 1-3 as examples, the separators and positive and negative electrodes prepared in the above examples and comparative examples were used to prepare cells by stacking process. Then, conventional lithium battery processes such as liquid injection, encapsulation and formation were carried out. The completed batteries were tested for safety performance, and the results are shown in Table 4.

[0313] 150℃ thermal shock pass rate: Tested according to the national standard GB / T18287-2013, the judgment criteria are no leakage, no fire and no explosion.

[0314] Short circuit pass rate: Tested according to the national standard GB / T18287-2013. The judgment criteria are no fire, no explosion, and external surface temperature below 150℃.

[0315] 10V / 3C overcharge pass rate: Tested according to the national standard GB / T18287-2013, the judgment standard is no fire and no explosion.

[0316] Table 4 Safety Performance Test Results

[0317] As can be seen from the tests in Table 4, compared with organic adhesive composite separators with PE as the body film and PE separators without inorganic composite material coating, the batteries prepared by the separator of this disclosure have superior safety performance in testing.

[0318] The separator provided in this disclosure has a low thermal shrinkage rate at high temperatures, which can give the battery good safety performance. In the event of thermal runaway or accidents caused by improper use, it can more effectively prevent battery fires and explosions.

[0319] In summary, this disclosure successfully prepared a lithium battery separator with ultra-high heat resistance, excellent electrolyte wettability, high ionic conductivity, and a robust coating structure by employing an inorganic binder system including silicates, alumina sol, silica sol, and mixtures thereof, and by strictly controlling its modulus, dosage, and the thickness of the composite material layer. This technical solution effectively solves the problems of electrolyte swelling and high-temperature decomposition leading to coating powdering and detachment caused by traditional organic binders, significantly improving the safety and electrochemical performance of the battery.

[0320] The preparation method of this separator is simple and easy to scale up for industrial production, and it has good prospects for industrialization.

[0321] The above description is merely a preferred embodiment of this disclosure and is not intended to limit this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure. Industrial applicability

[0322] The separator disclosed herein possesses ultra-high heat resistance, excellent electrolyte wettability, high ionic conductivity, and a robust coating structure. This technical solution effectively solves the problems of electrolyte swelling and high-temperature decomposition leading to coating powdering and detachment associated with traditional organic binders, significantly improving battery safety and electrochemical performance. The separator's preparation method is simple and easy to scale up for industrial production, demonstrating promising industrialization prospects.

Claims

1. A separating membrane, characterized in that, The isolation membrane includes a body membrane and a composite material layer disposed on at least one surface of the body membrane; the composite material layer includes inorganic particles and an inorganic binder; The inorganic binder includes components with the chemical formula M2O·nSiO2 and / or components with the chemical formula a(Al2O3·mH2O)·bH x Aluminum sol of ·cH2O, wherein M includes at least one of Na, K and Li, 1≤n≤4; Al2O3·mH2O is hydrated aluminum oxide, H x For the adhesive solvent, b is less than a, c, and m.

2. A separating membrane, characterized in that, The isolation membrane includes a body membrane and a composite material layer disposed on at least one surface of the body membrane; the composite material layer includes inorganic particles and an inorganic binder; The inorganic binder comprises silicates with the chemical formula M2O·nSiO2, and / or silicates with the chemical formula a(Al2O3·mH2O)·bH x Aluminum sol with the chemical formula ·cH2O, and / or silica sol with the chemical formula SiO2·dH2O, wherein M includes at least one of Na, K, and Li, 1≤n≤4; Al2O3·mH2O is hydrated alumina, H x For the adhesive solvent, b is less than a, c, and m; 1 ≤ d ≤ 4.

3. The separator according to claim 1 or 2, characterized in that, The dry weight of the inorganic binder is 1% to 35% of the mass of the inorganic particles in the composite material layer; And / or, the aluminum sol and the silica sol are in particulate form before film formation, with a particle size of 5nm-400nm.

4. The separator membrane according to claim 3, characterized in that, The dry weight of the component with the chemical formula M2O·nSiO2 is 1% to 35% of the mass of inorganic particles in the composite material layer.

5. The separator according to claim 1 or 2, characterized in that, The aluminum sol has at least one of the following characteristics: Feature 1: The particle size range of the aluminum sol is 5nm to 200nm; Feature 2: The pH value of the aluminum sol is 2-7; Feature 3: The dry weight of the aluminum sol is 1%-20% of the mass of the inorganic particles in the composite material layer; Feature 4: In the chemical formula of the aluminum sol, a is 1-5, b is 1-3, c is 1-5, and m is 1-7; Feature 5: The adhesive solvent is one of hydrochloric acid, sulfuric acid and nitric acid.

6. The separator according to claim 2, characterized in that, The silica sol has at least one of the following characteristics: Feature 6: The particle size range of the silica sol is 5nm to 200nm; Feature 7: The pH value of the silica sol is 7 to 11.

7. The separator according to claim 1 or 2, characterized in that, The inorganic particles have at least one of the following characteristics: Feature 8: The inorganic particles include at least one of kaolin, boehmite, clay, molecular sieve, Al2O3, SiO2, BaSO4, BaO, MgO, CuO, LiAlO2, ZrO2, Fe2O3, BaTiO3, α-V2O5, PbTiO3, CaSiO3, titanium dioxide, LiF, MgF2, BaF2, TiB2, Mg(OH)2, MoS2, SiC, Si3N4, and carbon nanotubes; Feature 9: The average particle size of the inorganic particles is 10 nm to 5 μm.

8. The separator according to claim 1 or 2, characterized in that, The thickness of the isolation membrane is 2.3 μm to 48 μm; And / or, the thickness of the bulk film is 2 μm to 40 μm; And / or, the bulk membrane includes at least one of a polymer membrane and a ceramic membrane; And / or, the thickness of the composite material layer is 0.3 μm to 9 μm.

9. A method for preparing a separating membrane as described in claim 1 or 2, characterized in that, Includes the following steps: A composite material layer slurry containing the inorganic binder and the inorganic particles is coated onto at least one surface of the bulk membrane and then dried.

10. The preparation method according to claim 9, characterized in that, The composite material layer slurry has at least one of the following characteristics: Feature 10: The solid content of the composite material layer slurry is 2% to 50%; Feature 11: The viscosity of the composite material layer slurry is 10cp to 1000cp.

11. The preparation method according to claim 9, characterized in that, Drying is carried out at 50℃~70℃ for 2min~5min.

12. An electrochemical device, characterized in that, The electrochemical device includes the isolation membrane as described in any one of claims 1 to 8.

13. A separating membrane, characterized in that, The isolation membrane includes a body membrane and a composite material layer disposed on at least one surface of the body membrane; the composite material layer contains crystals formed by an inorganic binder, the crystals including at least one of plate-like crystals and spherical crystals as well as needle-like whiskers.

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