A lithium battery separator and preparation method thereof

Abstract

The present invention discloses a lithium battery separator and a preparation method thereof. The lithium battery separator comprises a base film having a length and a width; a ceramic layer disposed on the base film, the ceramic layer comprising ceramic particles, elastic particles, and an adhesive, wherein the adhesive has an elastic modulus of 1.1 GPa to 1.6 GPa at 25°C after curing; and a plurality of support members disposed within the ceramic layer and sequentially distributed along the length of the base film. For each support member, the support member has a length, is parallel to the width of the base film, and has an elastic modulus greater than the elastic modulus of the adhesive after curing. The preparation method comprises the steps of preparing a slurry, applying a first coating, and applying a second coating. The lithium battery separator provided by the present invention has the effect of the ceramic layer and the support members jointly maintaining the stability of the separator.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a lithium battery separator and a preparation method thereof. Background Art

[0002] As one of the core components of lithium-ion batteries, lithium battery separators play the key function of isolating the positive and negative electrodes and preventing short circuits in the battery system. At the same time, they must ensure the efficient transmission of lithium ions to maintain the normal charge and discharge performance of the battery. The material properties and structural design of the separator directly affect the core performance indicators of the battery, such as safety, cycle life and energy density. At present, the mainstream separator materials mainly use polyolefin polymers or porous ceramic composites. These materials have the characteristics of high porosity, excellent chemical stability and mechanical strength. With the growing demand for high-energy-density and high-safety lithium batteries in the fields of new energy vehicles and energy storage, separator technology continues to iterate and upgrade. Among them, the research and development and application of ceramic-coated separators and high-performance polymer separators have significantly improved the overall performance of lithium batteries.

[0003] In the technical development of ceramic coated diaphragms, enhancing the mechanical strength of the ceramic layer is an important research direction for improving diaphragm performance. Its technical advantages are mainly reflected in the following aspects:

[0004] ① Improving mechanical strength significantly enhances the separator's resistance to mechanical damage. During battery assembly and use, the separator is susceptible to mechanical stresses such as extrusion and vibration. Furthermore, the growth of lithium dendrites can also pose a puncture risk. Improving the mechanical strength of the ceramic layer effectively prevents separator rupture and short circuits caused by direct contact between the positive and negative electrodes, thereby reducing the safety risk of thermal runaway.

[0005] ② The high-strength ceramic layer improves the thermal stability of the separator. Conventional polyolefin separators are prone to thermal shrinkage or even melting in high-temperature environments. The high-strength ceramic layer maintains the separator's structural integrity, preventing battery performance degradation or safety incidents caused by separator failure.

[0006] ③ The improvement in mechanical strength helps achieve a thinner and lighter separator design. While maintaining the same performance indicators, the high-strength ceramic layer can support a thinner separator structure, which not only helps to increase the energy density of the battery, but also reduces material costs and enhances the market competitiveness of the product.

[0007] However, while pursuing the improvement of the mechanical strength of the ceramic layer, this technical route also faces the following technical challenges:

[0008] ① The difficulty of balancing mechanical strength and ionic conductivity. Improving the mechanical strength of the ceramic layer is often accompanied by a decrease in porosity or pore size, which increases the transport resistance of lithium ions in the separator, resulting in a decrease in the battery's rate performance and affecting charge and discharge efficiency.

[0009] ② The contradiction between surface properties and electrolyte wettability. To achieve higher mechanical strength, high-concentration ceramic particles or a densified coating process are usually required. This may reduce the lyophilicity of the separator surface, affecting the wettability and uniform distribution of the electrolyte, and thus affecting the battery's interface stability and cycle performance.

[0010] ③Performance stability issues in high-temperature environments. Excessive mechanical strength may cause the thermal stability of the ceramic layer to decrease under extreme operating conditions (such as overcharging, short circuit, etc.). If the ceramic layer undergoes thermal expansion or structural changes at high temperatures, it may cause the risk of thermal runaway inside the battery.

[0011] In summary, the technical route of optimizing the performance of ceramic coating diaphragms by simply relying on improving the mechanical strength of the ceramic layer has faced significant technical bottlenecks, and it is urgent to explore new technological breakthroughs to achieve a comprehensive improvement in diaphragm performance. Summary of the Invention

[0012] In view of the deficiencies in the prior art, the present invention aims to provide a lithium battery separator and a preparation method thereof.

[0013] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0014] In one aspect, a lithium battery separator comprises:

[0015] a base film having a length and a width;

[0016] a ceramic layer disposed on the base film, the ceramic layer comprising ceramic particles, elastic particles, and an adhesive, wherein the adhesive has an elastic modulus of 1.1 GPa to 1.6 GPa at 25° C. after curing;

[0017] A plurality of support members, wherein the plurality of support members are arranged in the ceramic layer, and the plurality of support members are distributed in sequence along the length direction of the base film; for any of the support members, the support member has a length, the support member is parallel to the width direction of the base film, and the elastic modulus of the support member is greater than the elastic modulus of the adhesive after curing.

[0018] At present, the thickness of the ceramic layer of commercially available lithium battery separators is generally controlled within 10μm. The key materials of lithium batteries, including positive electrodes, separators and negative electrodes, are usually stacked in a curled or folded manner. Unlike traditional technologies, the support member in the present invention has a linear structure parallel to the width direction of the base film, rather than a mesh structure. Specifically, the support member of the present invention has a clear length direction, the ceramic layer can completely wrap the support member, and the effect on the porosity of the ceramic layer is significantly reduced. In contrast, the mesh support member has the following technical defects:

[0019] ① Processing difficulty: Linear supports can be produced through a stretching process, and their thickness is easy to control; however, mesh supports have a complex structure and are significantly more difficult to process, making it difficult to ensure uniform thickness of the supports.

[0020] ② Spreading flatness: The mesh support is prone to unevenness during the spreading process, which may lead to uneven porosity distribution of the ceramic layer, thus affecting battery performance.

[0021] ③Node thickness issue: When multiple support members intersect to form a mesh structure, the thickness at the nodes increases significantly. Due to the insufficient coverage of the ceramic layer at the nodes, the uniformity of the ceramic layer pores is destroyed, which in turn affects the overall performance of the diaphragm.

[0022] Preferably, the thickness of the ceramic layer of the present invention is 6 μm to 8 μm, the support member is a strip-shaped structure, the thickness of the support member is 2 μm to 4 μm, and the width of the support member is 4 μm to 8 μm.

[0023] Preferably, it further comprises two connecting parts, which extend along the length direction of the base film; for any one of the supporting members, both ends of the supporting member are respectively connected to the two connecting parts.

[0024] In the present invention, the support member and the connecting portion form a strip parallel to the length direction of the base film. When manufacturing a lithium battery separator, it is only necessary to align the strip-shaped support member and the connecting portion along the length direction of the base film to evenly distribute the support member in the ceramic layer, which is beneficial to reducing the difficulty of manufacturing the lithium battery separator.

[0025] Preferably, the plurality of support members are parallel to each other, and the distance between two adjacent support members is 0.02 cm to 0.06 cm.

[0026] Preferably, the material of the support member is selected from one or both of polyethylene terephthalate and epoxy resin.

[0027] In the present invention, the pH value of the lithium battery electrolyte is usually between 5.5 and 6.5, which is weakly acidic, and polyethylene terephthalate and epoxy resin can exist stably.

[0028] Preferably, the average particle size of the ceramic particles is 60 nm to 80 nm, the average particle size of the elastic particles is not greater than the average particle size of the ceramic particles, and the average particle size of the elastic particles is 40 nm to 60 nm.

[0029] In the present invention, the ceramic particles used in the ceramic layer have a relatively large particle size, and the gaps between the ceramic particles are larger, which is beneficial to increasing the porosity, facilitating the penetration of the electrolyte, and improving the performance of the lithium battery separator.

[0030] In the present invention, when the average particle size of the elastic particles is less than 40 nm, the elastic particles will affect the porosity between the ceramic particles; when the average particle size of the elastic particles is greater than 60 nm, an excessively large elastic space will be formed between the ceramic particles, affecting the mechanical properties of the lithium battery separator.

[0031] In the present invention, when the average particle size of the elastic particles is 40 nm to 60 nm, the obtained lithium battery separator can take into account both porosity and mechanical properties.

[0032] Preferably, the elastic particles account for 10% to 15% of the mass of the ceramic particles.

[0033] In the present invention, when the amount of elastic particles used is less than 10% of the mass of the ceramic particles, the hardness of the obtained lithium battery separator is too large and it is easy to be damaged when responding to mechanical stress and physical impact; when the amount of elastic particles used is greater than 15% of the mass of the ceramic particles, the elastic hardness of the obtained lithium battery separator is insufficient and it is easy to be deformed.

[0034] Preferably, the material of the elastic particles is selected from one or more of silicone rubber, polyurethane, thermoplastic copolyester, thermoplastic polyester elastomer, and thermoplastic polyamide elastomer.

[0035] In the present invention, the pH value of the lithium battery electrolyte is usually between 5.5 and 6.5, which is weakly acidic, and silicone rubber, polyurethane, thermoplastic copolyester, thermoplastic polyester elastomer, and thermoplastic polyamide elastomer can exist stably.

[0036] In the present invention, the elastic particles are specifically selected from thermoplastic polyester elastomer particles.

[0037] Preferably, the ceramic particles are selected from one or more of strontium titanate (SrTiO3), tin dioxide (SnO2), cerium dioxide (CeO2), magnesium oxide (MgO), nickel oxide (NiO), zinc oxide (ZnO), zirconium dioxide (ZrO2), yttrium oxide (Y2O3), aluminum oxide (Al2O3), titanium dioxide (TiO2), silicon carbide (SiC), boehmite (AlOOH), and silicon dioxide (SiO2).

[0038] In the present invention, α-Al2O3 is specifically selected as the ceramic particles as an example.

[0039] Preferably, the adhesive comprises a coupling agent and an adhesive resin, the amount of the coupling agent is 2% to 4% of the total mass of the ceramic particles and the elastic particles, and the amount of the adhesive resin is 8% to 12% of the total mass of the ceramic particles and the elastic particles;

[0040] The coupling agent is selected from one or more of 3-chloropropyltrimethoxysilane, methacryloxypropyltrimethoxysilane, and 3-aminotriethoxysilane coupling agents;

[0041] The adhesive resin is selected from one or both of high-density polyethylene and polypropylene.

[0042] On the other hand, the present invention also includes a method for preparing a lithium battery separator, comprising the following steps:

[0043] Preparing slurry: preparing ceramic particles, elastic particles and binder into slurry;

[0044] First coating: first apply the slurry on the base film, then place the support on the coated slurry, and then dry it to obtain the primary layer;

[0045] Second coating: Apply slurry again on the primary layer, cover the support, and then dry to obtain the lithium battery separator.

[0046] Preferably, the thickness of the primary layer is 40% to 50% of the thickness of the ceramic layer.

[0047] The main raw materials of the present invention are as follows:

[0048] Strontium titanate (SrTiO3): Strontium titanate has a high dielectric constant and excellent thermal stability, significantly improving the insulation and high-temperature resistance of the separator, enhancing battery safety and cycle life. Its unique crystal structure helps enhance the mechanical strength of the separator and prevent thermal runaway, while also optimizing ion transport efficiency and improving overall battery performance. Strontium titanate's chemical stability also makes it perform well in electrolytes, effectively extending the battery's lifespan.

[0049] Tin dioxide (SnO2): Tin dioxide has excellent electrochemical stability and semiconductor properties, which can optimize battery charge and discharge performance. Its coating can improve the conductivity of the separator and reduce internal resistance. It also has good wettability with the electrolyte, which helps to evenly distribute the electrolyte. In addition, tin dioxide can absorb impurities in the electrolyte, extending battery life.

[0050] Cerium dioxide (CeO2): Cerium dioxide exhibits excellent oxidation resistance and thermal stability, absorbing harmful impurities (such as HF) in the electrolyte and extending battery life. Its high chemical stability improves the corrosion resistance of the separator while also enhancing its thermal stability and mechanical strength. Cerium dioxide's unique properties enable it to excel in high-temperature and high-voltage environments, significantly enhancing battery safety and performance.

[0051] Magnesium oxide (MgO): With its high melting point and excellent insulation properties, magnesium oxide significantly improves the separator's high-temperature resistance and short-circuit resistance. Its strong chemical inertness prevents it from reacting with the electrolyte, ensuring a stable internal battery environment. Furthermore, magnesium oxide absorbs moisture from the electrolyte, reducing internal humidity and further enhancing battery safety.

[0052] Nickel Oxide (NiO): Nickel oxide has excellent oxidation resistance and semiconductor properties, which can optimize the battery's rate performance and charge-discharge efficiency. Its coating improves the corrosion resistance of the separator, preventing impurities in the electrolyte from corroding the separator. Furthermore, nickel oxide improves the separator's mechanical strength and puncture resistance, extending battery life.

[0053] Zinc oxide (ZnO): Zinc oxide has excellent insulation and thermal stability, maintaining the integrity of the separator at high temperatures. Its excellent antibacterial properties improve the internal battery environment and prevent microbial growth. Furthermore, zinc oxide absorbs impurities in the electrolyte, reducing internal acidity and improving the battery's corrosion resistance and service life.

[0054] Zirconium dioxide (ZrO2): Zirconium dioxide offers high-temperature and corrosion resistance, along with high mechanical strength. It significantly improves the thermal and structural stability of the separator, enhancing battery safety. Its low coefficient of thermal expansion helps maintain the separator's dimensional stability at high temperatures while optimizing ion transport efficiency. Zirconium dioxide's exceptional properties enable it to perform exceptionally well in high-temperature and high-voltage environments, significantly enhancing battery safety and performance.

[0055] Yttrium trioxide (Y2O3): Yttrium trioxide has a high melting point and excellent chemical stability, significantly improving the high-temperature resistance and deformation resistance of the separator. Its uniform particles form a dense ceramic coating, enhancing the separator's insulation and puncture resistance. Yttrium trioxide also improves the separator's gas permeability and ion transport properties.

[0056] Aluminum oxide (Al2O3): Aluminum oxide (aluminum oxide) possesses excellent chemical inertness, thermal stability, and mechanical properties. Its coating significantly improves the high-temperature resistance and thermal shrinkage resistance of the separator, preventing deformation at high temperatures. Furthermore, aluminum oxide neutralizes acidic impurities in the electrolyte, extending battery life. It is currently one of the most widely used ceramic coating materials.

[0057] Titanium dioxide (TiO2): Titanium dioxide has excellent chemical and thermal stability, maintaining the dimensional stability of the separator at high temperatures. Its coating has good wettability with the electrolyte, which helps evenly distribute the electrolyte and improve battery performance. Furthermore, titanium dioxide has certain photocatalytic properties, which can improve the internal environment of the battery.

[0058] Silicon carbide (SiC): With its high hardness and excellent high-temperature resistance, SiC significantly improves the mechanical strength and thermal stability of the separator, enhancing battery safety. Its low coefficient of thermal expansion helps maintain the separator's dimensional stability at high temperatures while optimizing ion transport efficiency. These exceptional properties enable SiC to excel in high-temperature and high-voltage environments, significantly improving battery safety and performance.

[0059] Boehmite (AlOOH): Boehmite's uniform particle morphology significantly improves the thermal stability and safety of separators at low coating thicknesses. Its coating exhibits excellent electrolyte wettability, improving the battery's rate capability and cycle performance. Furthermore, boehmite's low hardness minimizes damage to production equipment and its low water absorption makes it suitable for high-nickel batteries.

[0060] Silicon dioxide (SiO2): Silica has excellent chemical stability and insulating properties, significantly improving the separator's high-temperature resistance and short-circuit resistance. It is low-cost, environmentally friendly, and has good wettability in the electrolyte, which helps ensure uniform electrolyte distribution. Furthermore, silicon dioxide absorbs impurities in the electrolyte, extending battery life.

[0061] Compared with the prior art, the advantages of the present invention include:

[0062] (1) The present invention provides a lithium battery separator. When the temperature is low, the elasticity of the ceramic layer itself can cope with mechanical stress and physical impact, which is beneficial to reducing damage. When the temperature rises, the elastic modulus of the ceramic layer decreases. At this time, the ceramic layer and the support member jointly maintain their own shape, which is beneficial to maintaining the stability of the separator.

[0063] (2) The present invention provides a lithium battery separator in which the elasticity of the ceramic layer can adapt to thermal expansion and contraction, and is also conducive to curling or folding;

[0064] (3) The present invention provides a lithium battery separator. In this application, by adjusting the amount of adhesive, a balance can be achieved between the elastic modulus and the ionic conductivity, and the ionic conductivity can be maintained while the mechanical properties are kept within a reasonable range. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0066] Figure 1 Schematic diagram of the support belt in the present invention;

[0067] Figure 2It is a partial enlarged schematic diagram of the support belt in the present invention;

[0068] Figure 3 This is a schematic diagram of the support belt being located on the primary layer in the present invention;

[0069] Figure 4 It is a cross-sectional schematic diagram of the lithium battery separator in the present invention.

[0070] Reference numerals:

[0071] 11. Support member; 12. Connecting part; 2. Polyethylene film; 3. Ceramic layer. DETAILED DESCRIPTION

[0072] To help those skilled in the art understand the features and effects of this application, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings understood by those skilled in the art in connection with this application. In the event of any conflict, the definitions in this specification shall prevail.

[0073] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of this application in any way, that is, the content of this application can be implemented without being limited by any specific theory or mechanism.

[0074] As used herein, "this application" refers to "the present invention" or "this disclosure."

[0075] Where "a," "an," or similar expressions are used herein to describe components and technical features described herein, such descriptions are merely for convenience and to provide a general sense of the scope of this application. Therefore, such descriptions should be understood to include one or at least one, and the singular also includes the plural, unless it is obvious that another meaning is intended.

[0076] In this document, "or a combination thereof" means "or any combination thereof", and "any one", "any one", and "any one" means "any one", "any one", and "any one".

[0077] As used herein, the terms "comprising," "including," "having," "containing," and any similar terms are open-ended transitional phrases, intended to encompass a non-exclusive inclusion. For example, a composition or article comprising multiple elements is not limited to the elements listed herein but may also include other elements not specifically listed but customary to the composition or article. Furthermore, unless expressly stated to the contrary, the term "or" is intended to be inclusive, not exclusive. For example, the condition "A or B" is satisfied by any of the following: A is true (or present) and B is false (or absent); A is false (or absent) and B is true (or present); and both A and B are true (or present). Furthermore, as used herein, the terms "comprising," "including," "having," and "containing" are to be construed as specifically disclosing and encompassing closed transitional phrases such as "consisting of," "consisting of," and "the remainder of," as well as transitional phrases such as "consisting essentially of," "consisting primarily of," "consisting primarily of," "consisting essentially of," "consisting essentially of," "consisting essentially of," and "essentially containing."

[0078] Throughout this document, all features or conditions, such as values, amounts, amounts, and concentrations, defined in numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within those ranges (including integers and fractions), particularly integer values. For example, descriptions of ranges such as "1.0 to 8.0," "between 1.0 and 8.0," or "between 1.0 and 8.0" should be considered to specifically disclose all subranges such as 1.0 to 8.0, 1.0 to 7.0, 2.0 to 8.0, 2.0 to 6.0, 3.0 to 6.0, 4.0 to 8.0, 3.0 to 8.0, and so forth, and should be considered to include endpoints, particularly subranges defined by integer values, and should be considered to specifically disclose individual values ​​within those ranges such as 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, and 8.0. Unless otherwise indicated, the above interpretation method applies to all contents of the entire application, regardless of the scope.

[0079] If the quantity, concentration or other numerical value or parameter is expressed as a range, a preferred range (or a better range) or a series of upper and lower limits, it should be understood that all ranges consisting of any pair of the upper limit or preferred value (or better value) of the range and the lower limit or preferred value (or better value) of the range have been specifically disclosed herein, regardless of whether these ranges are disclosed separately. In addition, when a numerical range is mentioned herein, unless otherwise specified, the range should include its endpoints and all integers and fractions within the range.

[0080] In this document, numerical values ​​should be understood to have the accuracy of the number of significant digits of the numerical value, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover the range of 39.50 to 40.49.

[0081] Unless otherwise specified, in this application, a compound refers to a chemical substance formed by two or more elements connected by chemical bonds, including, but not limited to, small molecule compounds and polymer compounds. The term "compound" as used herein is not limited to a single chemical substance but may also refer to chemical substances of the same type with the same composition or properties.

[0082] Unless otherwise specified, the term "resin" in this application is a customary name for a synthetic polymer, which may include monomers, polymers thereof, combinations of monomers, combinations of polymers thereof, or combinations of monomers and polymers thereof, etc., and is not limited thereto.

[0083] Unless otherwise specified, in this application, modified products include products obtained by modifying the reactive functional groups of each resin, products obtained by prepolymerization of each resin with other resins, products obtained by cross-linking each resin with other resins, products obtained by copolymerization of each resin with other resins, and the like.

[0084] Unless otherwise specified, the unsaturated bond described in this application refers to a reactive unsaturated bond, such as but not limited to an unsaturated double bond that can undergo a cross-linking reaction with other functional groups, such as but not limited to an unsaturated carbon-carbon double bond that can undergo a cross-linking reaction with other functional groups.

[0085] Unless otherwise specified, parts by weight in this application represent relative parts by weight in a composition and may be any weight unit, such as, but not limited to, kilograms, grams, pounds, etc. For example, 100 parts by weight of polyphenylene ether resin may represent 100 kilograms of polyphenylene ether resin or 100 pounds of polyphenylene ether resin.

[0086] It should be understood that the features disclosed in the various embodiments herein may be arbitrarily combined to form the technical solution of the present application, as long as there is no contradiction in the combination of these features.

[0087] The present application will be described below with specific embodiments and examples. It should be understood that these specific embodiments and examples are merely illustrative and are not intended to limit the scope of the present application and its use.

[0088] Unless otherwise stated, the methods, reagents and conditions used in the following preparation examples, comparative examples and examples are conventional methods, reagents and conditions in the art.

[0089] In the following descriptions:

[0090] Polyethylene film: thickness is 9um, porosity is 40%.

[0091] Sodium carboxymethyl cellulose: active ingredient content ≥99.99%.

[0092] Sodium polyacrylate: active ingredient content ≥99.99%.

[0093] α-Al2O3: content ≥99.99%, with two average particle sizes of 60nm and 80nm.

[0094] 3-Chloropropyltrimethoxysilane: active ingredient content ≥99.99%, density 1.09g / ml, boiling point 195℃, pH=7.

[0095] Methacryloxypropyltrimethoxysilane (KH-570 silane coupling agent): active ingredient content ≥ 99.5%, density 0.9510±0.005kg / m³.

[0096] 3-Aminotriethoxysilane: active ingredient content ≥99%, density 1.081g / ml, boiling point, boiling point 195℃~196℃.

[0097] Thermoplastic polyester elastomer (TPEE): hardness is 55D.

[0098] High-density polyethylene: The elastic modulus at room temperature is 1.06 GPa.

[0099] Polypropylene: The elastic modulus at room temperature is 1.52 GPa.

[0100] Polyethylene terephthalate film (PET): elastic modulus at room temperature is 2.12 GPa, and there are two thickness specifications: 2μm and 4μm.

[0101] Epoxy resin film: elastic modulus 3.41 GPa at room temperature, thickness 2 μm.

[0102] Polypropylene film: elastic modulus 0.86 GPa at room temperature, thickness 2 μm.

[0103] Preparation Example

[0104] Preparation Example 1

[0105] The raw materials used in this preparation example include, by weight, 1 part of 3-chloropropyltrimethoxysilane and 1 part of high-density polyethylene.

[0106] The preparation method of this preparation example includes: uniformly mixing the above raw materials at room temperature to obtain an adhesive.

[0107] Preparation Example 2

[0108] The difference between this preparation example and preparation example 1 is that the raw materials used in this preparation example include, by weight, 1 part of 3-chloropropyltrimethoxysilane and 6 parts of high-density polyethylene.

[0109] Preparation Example 3

[0110] The raw materials used in this preparation example include, by weight, 1 part of methacryloxypropyltrimethoxysilane and 1 part of high-density polyethylene.

[0111] The preparation method of this preparation example includes: uniformly mixing the above raw materials at room temperature to obtain an adhesive.

[0112] Preparation Example 4

[0113] The difference between this preparation example and preparation example 3 is that the raw materials used in this preparation example include, by weight, 1 part of 3-chloropropyltrimethoxysilane and 6 parts of high-density polyethylene.

[0114] Preparation Example 5

[0115] The raw materials used in this preparation example include, by weight, 1 part of 3-aminotriethoxysilane and 1 part of high-density polyethylene.

[0116] The preparation method of this preparation example includes: uniformly mixing the above raw materials at room temperature to obtain an adhesive.

[0117] Preparation Example 6

[0118] The difference between this preparation example and preparation example 5 is that the raw materials used in this preparation example include, by weight, 1 part of 3-chloropropyltrimethoxysilane and 6 parts of high-density polyethylene.

[0119] Preparation Example 7

[0120] The raw materials used in this preparation example include, by weight, 1 part of 3-chloropropyltrimethoxysilane and 1 part of polypropylene.

[0121] The preparation method of this preparation example includes: uniformly mixing the above raw materials at room temperature to obtain an adhesive.

[0122] Preparation Example 8

[0123] The difference between this preparation example and preparation example 7 is that the raw materials used in this preparation example include, by weight, 1 part of 3-chloropropyltrimethoxysilane and 6 parts of polypropylene.

[0124] Preparation Example 9

[0125] The raw materials used in this preparation example include, by weight, 1 part of methacryloxypropyltrimethoxysilane and 1 part of polypropylene.

[0126] The preparation method of this preparation example includes: uniformly mixing the above raw materials at room temperature to obtain an adhesive.

[0127] Preparation Example 10

[0128] The difference between this preparation example and preparation example 9 is that the raw materials used in this preparation example include, by weight, 1 part of 3-chloropropyltrimethoxysilane and 6 parts of polypropylene.

[0129] Preparation Example 11

[0130] The raw materials used in this preparation example include, by weight, 1 part of 3-aminotriethoxysilane and 1 part of polypropylene.

[0131] The preparation method of this preparation example includes: uniformly mixing the above raw materials at room temperature to obtain an adhesive.

[0132] Preparation Example 12

[0133] The difference between this preparation example and preparation example 11 is that the raw materials used in this preparation example include, by weight, 1 part of 3-chloropropyltrimethoxysilane and 6 parts of polypropylene.

[0134]

[0135] Preparation Example 13

[0136] The raw materials used in this preparation example include: a polyethylene terephthalate film with a thickness of 2 μm.

[0137] Reference Figure 1 and Figure 2 In this preparation example, the connecting portion extends along the length direction of the base film, there are two connecting portions, the two connecting portions are parallel to each other, and the distance between the two connecting portions is smaller than the width of the base film.

[0138] In this preparation example, the connecting portion is strip-shaped and has a width of 2 μm. In this preparation example, each end of the support portion is connected to a connecting portion, the thickness of the support portion is equal to that of any connecting portion, the width of the support portion is 4 μm, and the distance between two adjacent support portions is 0.02 cm.

[0139] In this preparation example, a plurality of support parts and two connecting parts integrally form a strip-shaped support belt. The support belt is obtained by ultraviolet laser cutting of a polyethylene terephthalate film. The width of the support belt is 9 cm.

[0140] Preparation Example 14

[0141] The difference between this preparation example and preparation example 13 is that the width of the support portion is 6 μm, and the distance between two adjacent support portions is 0.04 cm.

[0142] Preparation Example 15

[0143] The difference between this preparation example and preparation example 13 is that the thickness of the polyethylene terephthalate film is 4 μm, the width of the support portion is 8 μm, and the distance between two adjacent support portions is 0.04 cm.

[0144] Preparation Example 16

[0145] The difference between this preparation example and preparation example 13 is that in this preparation example, the polyethylene terephthalate film is replaced by an epoxy resin film with a thickness of 2 μm, the width of the support portion is 8 μm, and the distance between two adjacent support portions is 0.08 cm.

[0146] Preparation Example 17

[0147] The difference between this preparation example and preparation example 13 is that the width of the support portion is 8 μm, and the distance between two adjacent support portions is 0.08 cm.

[0148] Preparation Example 18

[0149] The difference between this Preparation Example and Preparation Example 13 is that in this Preparation Example, a polypropylene film with a thickness of 2 μm is used instead of the polyethylene terephthalate film.

[0150] Example

[0151] Example 1

[0152] The raw materials used in this embodiment include, by weight: 100 parts of α-Al2O3 with an average particle size of 60 nm, 4 parts of sodium carboxymethyl cellulose, 3 parts of sodium polyacrylate, 100 parts of water, 10 parts of TPEE with an average particle size of 40 nm, the support tape obtained in Preparation Example 13, and 11 parts of the adhesive obtained in Preparation Example 1.

[0153] The preparation method of this embodiment includes:

[0154] S1. At 25°C, α-Al2O3, TPEE, sodium carboxymethyl cellulose, sodium polyacrylate, water, and a binder were uniformly mixed to prepare a slurry;

[0155] S2. First, the slurry was coated on a 10 cm wide polyethylene film by gravure printing. Then, a support tape was laid flat on the coated slurry. The long edges of the support tape and the polyethylene film were both 0.5 cm, and the coating thickness was 2 μm. The slurry was then heated at 80°C until the surface of the slurry was solid to obtain a primary layer.

[0156] S3. Apply the slurry to the primary layer and cover it with a support tape. The maximum coating thickness is 4 μm so that the total thickness on the polyethylene film is 6 μm. Then, dry it at 120° C. to obtain a lithium battery separator.

[0157] Example 2

[0158] The difference between this embodiment and embodiment 1 is that the average particle size of TPEE in the raw materials used in this embodiment is 60 nm.

[0159] Example 3

[0160] The difference between this embodiment and embodiment 1 is that among the raw materials used in this embodiment, the mass parts of TPEE are 15 parts, and the mass parts of the adhesive obtained in preparation example 1 are 11.5 parts.

[0161] Example 4

[0162] The difference between this embodiment and embodiment 1 is that among the raw materials used in this embodiment, the average particle size of α-Al2O3 is 80 nm, the average particle size of TPEE is 60 nm, the amount of TPEE used is 12 parts, the support tape comes from Preparation Example 14, the adhesive comes from Preparation Example 2, and the amount of adhesive used is 14.6 parts.

[0163] Example 5

[0164] The difference between this embodiment and embodiment 4 is that: the support tape used in this embodiment is derived from preparation example 15; the coating thickness in step S2 is 2 μm; and the maximum coating thickness in step S3 is 4 μm, so that the total thickness on the polyethylene film is 6 μm.

[0165] Example 6

[0166] The difference between this embodiment and Example 1 is that the average particle size of α-Al2O3 is 80 nm, the amount of TPEE is 15 parts, the support tape is derived from Preparation Example 16, the adhesive is derived from Preparation Example 3, and the amount of adhesive is 11.5 parts; the coating thickness in step S2 is 3 μm; the maximum coating thickness in step S3 is 5 μm, so that the total thickness on the polyethylene film is 8 μm.

[0167] Example 7

[0168] The difference between this embodiment and embodiment 1 is that the support tape comes from Preparation Example 16, the adhesive comes from Preparation Example 3, and the amount of adhesive used is 18.4 parts.

[0169] Example 8

[0170] The difference between this embodiment and embodiment 7 is that the support tape is derived from preparation example 17, and the adhesive is derived from preparation example 4; in step S2, after the polyethylene film is coated, it is heated at 65°C until the surface of the slurry becomes solid, thereby obtaining a primary layer.

[0171] Example 9

[0172] The difference between this embodiment and embodiment 8 is that the adhesive is derived from preparation example 5; in step S2, after the polyethylene film is coated, it is heated at 70°C until the surface of the slurry becomes solid, thereby obtaining a primary layer.

[0173] Example 10

[0174] The difference between this embodiment and embodiment 8 is that the adhesive is derived from preparation example 6; in step S2, after the polyethylene film is coated, it is heated at 75°C until the surface of the slurry becomes solid, thereby obtaining a primary layer.

[0175] Example 11

[0176] The difference between this embodiment and embodiment 8 is that the adhesive is derived from preparation example 7.

[0177] Example 12

[0178] The difference between this embodiment and embodiment 8 is that the adhesive is derived from preparation example 8; in step S2, after the polyethylene film is coated, it is heated at 85°C until the surface of the slurry becomes solid, thereby obtaining a primary layer.

[0179] Example 13

[0180] The difference between this embodiment and embodiment 8 is that the adhesive is derived from preparation example 9; in step S2, after the polyethylene film is coated, it is heated at 90°C until the surface of the slurry becomes solid, thereby obtaining a primary layer.

[0181] Example 14

[0182] The difference between this embodiment and embodiment 8 is that the adhesive is derived from preparation example 10; in step S2, after the polyethylene film is coated, it is heated at 95°C until the surface of the slurry becomes solid, thereby obtaining a primary layer.

[0183] Example 15

[0184] The difference between this embodiment and embodiment 8 is that: the adhesive is derived from preparation example 11; the coating thickness in step S2 is 4 μm; and the maximum coating thickness in step S3 is 4 μm so that the total thickness on the polyethylene film is 8 μm.

[0185] Example 16

[0186] The difference between this embodiment and embodiment 8 is that the adhesive is derived from preparation example 12.

[0187] Comparative Example

[0188] Comparative Example 1

[0189] The raw materials used in this comparative example include, by weight: 100 parts of α-Al2O3 with an average particle size of 60 nm, 4 parts of sodium carboxymethyl cellulose, 3 parts of sodium polyacrylate, 100 parts of water, 10 parts of TPEE with an average particle size of 40 nm, and 11 parts of the adhesive obtained in Preparation Example 1.

[0190] The preparation method of this comparative example comprises:

[0191] D1. At 25°C, α-Al2O3, TPEE, sodium carboxymethyl cellulose, sodium polyacrylate, water, and a binder were uniformly mixed to prepare a slurry;

[0192] D2. The slurry was coated on a 10 cm wide polyethylene film by gravure printing process with a coating thickness of 6 μm, and then dried at 120° C. to obtain a lithium battery separator.

[0193] Comparative Example 2

[0194] The difference between this comparative example and comparative example 1 is that the support tape is derived from Preparation Example 18.

[0195] Comparative Example 3

[0196] The difference between this comparative example and comparative example 1 is that the average particle size of TPEE is 20 nm.

[0197] Comparative Example 4

[0198] The difference between this comparative example and comparative example 1 is that the average particle size of TPEE is 80 nm.

[0199] Comparative Example 5

[0200] The difference between this comparative example and comparative example 1 is that the amount of TPEE used is 5 parts.

[0201] Comparative Example 6

[0202] The difference between this comparative example and comparative example 1 is that the amount of TPEE used is 20 parts.

[0203] Comparative Example 6

[0204] The difference between this comparative example and comparative example 4 is that high-density polyethylene is used as the adhesive.

[0205]

[0206] Performance Testing

[0207] The lithium battery separators prepared in Examples 1 to 16 and Comparative Examples 1 to 7 were tested according to the following test items:

[0208] (1) Determination of puncture strength: According to the provisions of GB / T36363-2018, the samples were tested at 25°C and 80°C respectively;

[0209] (2) Hot and cold alternating test: the decrease in puncture strength of the test specimen after alternating between 125°C and -20°C for 50 times;

[0210] (3) Ionic conductivity test: The test is carried out in accordance with the provisions of 6.2.2 Ionic conductivity performance test of the national standard GB / T36363-2018 "Polyolefin separators for lithium batteries".

[0211] Test results

[0212]

[0213] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly. It cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, they can make some simple deductions or substitutions without departing from the concept of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A lithium battery separator, characterized in that: include: a base film having a length and a width; a ceramic layer disposed on the base film, the ceramic layer comprising ceramic particles, elastic particles, and an adhesive, wherein the adhesive has an elastic modulus of 1.1 GPa to 1.6 GPa at 25° C. after curing; A plurality of support members, wherein the plurality of support members are all arranged in the ceramic layer, the ceramic layer completely wraps the support members, and the plurality of support members are distributed in sequence along the length direction of the base film; for any of the support members, the support member has a length, the support member is parallel to the width direction of the base film, and the elastic modulus of the support member is greater than the elastic modulus of the adhesive after curing.

2. A lithium battery separator according to claim 1, characterized in that: The thickness of the ceramic layer is 6 μm to 8 μm, the support member is a strip-shaped structure, the thickness of the support member is 2 μm to 4 μm, and the width of the support member is 4 μm to 8 μm.

3. The lithium battery separator according to claim 1, characterized in that: It also includes two connecting parts, which extend along the length direction of the base film; for any one of the supporting members, the two ends of the supporting member are respectively connected to the two connecting parts.

4. A lithium battery separator according to claim 3, characterized in that: The plurality of support members are parallel to each other, and the distance between two adjacent support members is 0.02 cm to 0.06 cm.

5. The lithium battery separator according to claim 1, characterized in that: The material of the support member is selected from one or both of polyethylene terephthalate and epoxy resin.

6. The lithium battery separator according to claim 1, characterized in that: The average particle size of the ceramic particles is 60nm to 80nm, the average particle size of the elastic particles is not greater than the average particle size of the ceramic particles, and the average particle size of the elastic particles is 40nm to 60nm; and / or, the elastic particles account for 10% to 15% of the mass of the ceramic particles; And / or, the material of the elastic particles is selected from one or more of silicone rubber, polyurethane, thermoplastic copolyester, thermoplastic polyester elastomer, and thermoplastic polyamide elastomer; And / or, the ceramic particles are selected from one or more of strontium titanate, tin dioxide, cerium dioxide, magnesium oxide, nickel oxide, zinc oxide, zirconium dioxide, yttrium oxide, aluminum oxide, titanium dioxide, silicon carbide, boehmite, and silicon dioxide.

7. The lithium battery separator according to claim 1, characterized in that: The adhesive comprises a coupling agent and an adhesive resin, wherein the coupling agent accounts for 2% to 4% of the total mass of the ceramic particles and the elastic particles, and the adhesive resin accounts for 8% to 12% of the total mass of the ceramic particles and the elastic particles; The coupling agent is selected from one or more of 3-chloropropyltrimethoxysilane, methacryloxypropyltrimethoxysilane, and 3-aminotriethoxysilane coupling agents; The adhesive resin is selected from one or both of high-density polyethylene and polypropylene.

8. A method for preparing a lithium battery separator according to claim 1, characterized in that: The steps include: Preparing slurry: preparing ceramic particles, elastic particles and binder into slurry; First coating: first apply the slurry on the base film, then place the support on the coated slurry, and then dry it to obtain the primary layer; Second coating: Apply slurry again on the primary layer, cover the support, and then dry to obtain the lithium battery separator.

9. The preparation method according to claim 8, characterized in that: The thickness of the initial layer is 40% to 50% of the ceramic layer.

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