Lithium battery diaphragm and preparation method thereof

Abstract

The invention discloses a lithium battery diaphragm and a preparation method thereof, the lithium battery diaphragm comprises a base membrane, and the base membrane has a length and a width; the ceramic layer is arranged on the base film, the ceramic layer comprises ceramic particles, elastic particles and an adhesive, and after the adhesive is cured, the elastic modulus at the temperature of 25 DEG C is 1.1 GPa to 1.6 GPa; the multiple supporting pieces are all arranged in the ceramic layer, and the multiple supporting pieces are sequentially distributed in the length direction of the base membrane; for any supporting piece, the supporting piece has a length, the supporting piece is parallel to the width direction of the base film, and the elastic modulus of the supporting piece is larger than that of the cured adhesive; the preparation method comprises the following steps: preparing slurry, coating for the first time and coating for the second time. The lithium battery diaphragm provided by the invention has the effect that the ceramic layer and the supporting piece jointly maintain the stability of the diaphragm.

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 have the key functions of isolating 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 charging and discharging 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 comprehensive 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 the performance of diaphragms. Its technical advantages are mainly reflected in the following aspects: ① Improving mechanical strength can significantly enhance the diaphragm's ability to resist mechanical damage. During battery assembly and use, the diaphragm is susceptible to mechanical stresses such as extrusion and vibration. At the same time, the growth of lithium dendrites may also pose a risk of puncture to the diaphragm. Improving the mechanical strength of the ceramic layer can effectively prevent the diaphragm from rupturing and avoid short circuits caused by direct contact between the positive and negative electrodes, thereby reducing the safety hazard of thermal runaway of the battery.

[0004] ② The high-strength ceramic layer can improve the thermal stability of the diaphragm. Under high temperature conditions, traditional polyolefin diaphragms are prone to thermal shrinkage or even melting, while the high-strength ceramic layer can maintain the structural integrity of the diaphragm and prevent battery performance degradation or safety accidents caused by diaphragm failure.

[0005] ③ The improvement of mechanical strength helps to achieve a lighter and thinner design of the diaphragm. Under the premise of ensuring the same performance indicators, the high-strength ceramic layer can support a thinner diaphragm structure, which is not only conducive to improving the energy density of the battery, but also can reduce material costs and enhance the market competitiveness of the product.

[0006] However, while pursuing the improvement of the mechanical strength of the ceramic layer, this technical route also faces the following technical challenges: ① The difficulty of balancing mechanical strength and ion conductivity. The improvement of the mechanical strength of the ceramic layer is often accompanied by a decrease in porosity or pore size, which will increase the transmission resistance of lithium ions in the separator, resulting in a decrease in the battery's rate performance and affecting the charge and discharge efficiency.

[0007] ② The contradiction between surface characteristics and electrolyte wettability. In order to achieve higher mechanical strength, high-concentration ceramic particles or densification coating processes are usually required, which may reduce the lyophilicity of the diaphragm surface, affect the wettability and uniform distribution of the electrolyte, and further affect the interface stability and cycle performance of the battery.

[0008] ③Performance stability issues under high temperature environments. Excessive mechanical strength may cause the thermal stability of the ceramic layer to decrease under extreme 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.

[0009] 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

[0010] In view of the deficiencies in the prior art, an object of the present invention is to provide a lithium battery separator and a preparation method thereof.

[0011] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes: In one aspect, a lithium battery separator comprises: a base film having a length and a width; A ceramic layer, the ceramic layer is arranged on the base film, the ceramic layer comprises ceramic particles, elastic particles and an adhesive, and the elastic modulus of the adhesive at 25° C. after curing is 1.1 GPa to 1.6 GPa; A plurality of support members, wherein the plurality of support members are all 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.

[0012] 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: ① Processing difficulty: Linear supports can be realized through stretching process, and their thickness is easy to control; however, due to the complex structure of mesh supports, the processing difficulty is significantly increased, and it is difficult to ensure the uniformity of the thickness of the supports.

[0013] 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.

[0014] ③Node thickness problem: When multiple supports cross to form a mesh structure, the thickness at the node will increase significantly. Due to the insufficient coverage thickness of the ceramic layer at the node, the uniformity of the pores in the ceramic layer will be destroyed, thus affecting the overall performance of the diaphragm.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] Preferably, the material of the support member is selected from one or both of polyethylene terephthalate and epoxy resin.

[0020] 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.

[0021] 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.

[0022] In the present invention, the particle size of the ceramic particles selected for the ceramic layer is relatively large, and the gaps between the ceramic particles are larger, which is beneficial to improving the porosity, facilitating the penetration of the electrolyte, and improving the performance of the lithium battery separator.

[0023] 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.

[0024] 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.

[0025] Preferably, the elastic particles account for 10% to 15% of the mass of the ceramic particles.

[0026] 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 deform.

[0027] 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.

[0028] 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.

[0029] In the present invention, the elastic particles are specifically selected from thermoplastic polyester elastomer particles.

[0030] Preferably, the ceramic particles are selected from strontium titanate (SrTiO 3 )、SnO 2 ), cerium dioxide (CeO 2 )、MgO、NiO、ZnO、ZrO 2 ), yttrium trioxide (Y 2 O 3 ), aluminum oxide (Al 2 O 3 ), titanium dioxide (TiO 2 ), silicon carbide (SiC), boehmite (AlOOH), silicon dioxide (SiO 2 ) one or more of the following.

[0031] In the present invention, the ceramic particles are specifically selected from α-Al 2 O 3 As an example.

[0032] Preferably, the adhesive comprises a coupling agent and an adhesive resin, the coupling agent is used in an amount of 2% to 4% of the sum of the mass of the ceramic particles and the elastic particles, and the adhesive resin is used in an amount of 8% to 12% of the sum of the 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.

[0033] On the other hand, the present invention also includes a method for preparing a lithium battery separator, comprising the following steps: Preparing slurry: preparing ceramic particles, elastic particles and a binder into slurry; First coating: first coat 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: Coat the slurry on the primary layer again, cover the support, and then dry to obtain the lithium battery separator.

[0034] Preferably, the thickness of the primary layer is 40% to 50% of the thickness of the ceramic layer.

[0035] The main raw materials of the present invention are introduced as follows: Strontium titanate (SrTiO 3 ): Strontium titanate has a high dielectric constant and excellent thermal stability, which can significantly improve the insulation and high temperature resistance of the diaphragm, and enhance the safety and cycle life of the battery. Its unique crystal structure helps to improve the mechanical strength of the diaphragm and prevent thermal runaway, while optimizing the ion transfer efficiency and improving the overall performance of the battery. The chemical stability of strontium titanate also makes it perform well in the electrolyte, which can effectively extend the service life of the battery.

[0036] Tin dioxide (SnO 2 ): Tin dioxide has good electrochemical stability and semiconductor properties, which can optimize the charge and discharge performance of the battery. Its coating can improve the conductivity of the diaphragm and reduce the internal resistance. At the same time, it has good wettability to the electrolyte, which helps to evenly distribute the electrolyte. In addition, tin dioxide can absorb impurities in the electrolyte and extend the battery life.

[0037] Cerium dioxide (CeO 2 ): Cerium dioxide has excellent oxidation resistance and thermal stability, and can absorb harmful impurities (such as HF) in the electrolyte to extend the battery life. Its high chemical stability helps to improve the corrosion resistance of the diaphragm, while enhancing the thermal stability and mechanical strength of the diaphragm. The unique properties of cerium dioxide enable it to perform well in high temperature and high voltage environments, significantly improving the safety and performance of the battery.

[0038] Magnesium oxide (MgO): Magnesium oxide has a high melting point and good insulation properties, which can significantly improve the high temperature resistance and short circuit resistance of the diaphragm. It is chemically inert and will not react with the electrolyte, ensuring a stable internal environment of the battery. In addition, magnesium oxide can absorb moisture in the electrolyte, reduce the humidity inside the battery, and further improve safety.

[0039] Nickel oxide (NiO): Nickel oxide has good oxidation resistance and semiconductor properties, which can optimize the battery's rate performance and charge and discharge efficiency. Its coating can improve the corrosion resistance of the diaphragm and prevent the erosion of the diaphragm by impurities in the electrolyte. In addition, nickel oxide can also improve the mechanical strength of the diaphragm, enhance its puncture resistance, and extend the battery life.

[0040] Zinc oxide (ZnO): Zinc oxide has good insulation and thermal stability, and can maintain the integrity of the diaphragm at high temperatures. Its excellent antibacterial properties can improve the internal environment of the battery and prevent the growth of microorganisms. In addition, zinc oxide can absorb impurities in the electrolyte, reduce the acidity inside the battery, and improve the corrosion resistance and service life of the battery.

[0041] Zirconium dioxide (ZrO 2 ): Zirconium dioxide is resistant to high temperatures and corrosion, has high mechanical strength, and can significantly improve the thermal stability and structural stability of the diaphragm, enhancing battery safety. Its low thermal expansion coefficient helps maintain the dimensional stability of the diaphragm at high temperatures while optimizing ion transfer efficiency. The excellent properties of zirconium dioxide enable it to perform well in high temperature and high voltage environments, significantly improving the safety and performance of the battery.

[0042] Yttrium trioxide (Y 2 O 3 ): Yttrium trioxide has a high melting point and good chemical stability, which can significantly improve the high temperature resistance and deformation resistance of the diaphragm. Its particles are uniform and can form a dense ceramic coating to enhance the insulation and puncture resistance of the diaphragm. In addition, yttrium trioxide can also improve the permeability and ion transmission performance of the diaphragm.

[0043] Aluminum oxide (Al 2 O 3 ): Aluminum oxide (aluminum oxide) has excellent chemical inertness, thermal stability and mechanical properties. Its coating can significantly improve the high temperature resistance and heat shrinkage resistance of the diaphragm and prevent the diaphragm from deforming at high temperatures. In addition, alumina can neutralize acidic impurities in the electrolyte and extend the battery life. It is currently one of the most widely used ceramic coating materials.

[0044] Titanium dioxide (TiO 2): Titanium dioxide has good chemical and thermal stability, and can maintain the dimensional stability of the separator at high temperatures. Its coating has good wettability to the electrolyte, which helps to evenly distribute the electrolyte and improve battery performance. In addition, titanium dioxide also has certain photocatalytic properties, which can improve the internal environment of the battery.

[0045] Silicon carbide (SiC): Silicon carbide has high hardness and excellent high temperature resistance, which can significantly improve the mechanical strength and thermal stability of the diaphragm and enhance the safety of the battery. Its low thermal expansion coefficient helps maintain the dimensional stability of the diaphragm at high temperatures while optimizing ion transmission efficiency. The excellent properties of silicon carbide enable it to perform well in high temperature and high voltage environments, significantly improving the safety and performance of the battery.

[0046] Boehmite (AlOOH): Boehmite particles have uniform morphology and can significantly improve the thermal stability and safety of the separator at a lower coating thickness. Its coating has good wettability to the electrolyte and can improve the rate performance and cycle performance of the battery. In addition, boehmite has low hardness, little damage to production equipment, and low water absorption, making it suitable for high-nickel batteries.

[0047] Silicon dioxide (SiO 2 ): Silicon dioxide has good chemical stability and insulation, which can significantly improve the high temperature resistance and short circuit resistance of the diaphragm. It is low-cost, environmentally friendly, and has good wettability to the electrolyte, which helps to evenly distribute the electrolyte. In addition, silicon dioxide can absorb impurities in the electrolyte and extend the battery life.

[0048] Compared with the prior art, the advantages of the present invention include: (1) The lithium battery separator provided by the present invention has a ceramic layer with elasticity that can cope with mechanical stress and physical impact when the temperature is low, 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; (2) The lithium battery separator provided by the present invention has a ceramic layer whose elasticity can adapt to thermal expansion and contraction and is also conducive to curling or folding; (3) The lithium battery separator provided by the present invention can achieve a balance between elastic modulus and ionic conductivity by adjusting the amount of adhesive used, and the ionic conductivity can be maintained while the mechanical properties are kept within a reasonable range. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0050] Figure 1 is a schematic diagram of the support belt in the present invention; Figure 2 It is a partial enlarged schematic diagram of the support belt in the present invention; Figure 3 This is a schematic diagram of the support belt being located on the primary layer in the present invention; Figure 4 It is a cross-sectional schematic diagram of the lithium battery separator in the present invention.

[0051] Reference numerals: 11. Support member; 12. Connecting portion; 2. Polyethylene film; 3. Ceramic layer. DETAILED DESCRIPTION

[0052] In order to enable those skilled in the art to understand the characteristics and effects of the present application, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein have the common meanings understood by those skilled in the art for the present application. In case of conflict, the definitions in this specification shall prevail.

[0053] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present application in any way, that is, the content of the present application can be implemented without being limited by any specific theory or mechanism.

[0054] As used herein, "this application" means "the present invention" or "the present disclosure".

[0055] The use of "one", "an", "a kind" or similar expressions to describe the components and technical features described in this application is merely for the convenience of expression and to provide a general meaning to the scope of this application. Therefore, such description should be understood to include one or at least one, and the singular also includes the plural, unless it is obvious that it refers to another meaning.

[0056] In this document, "or its combination" means "or any combination thereof", and "any one", "any one" means "any one", "any one" or "any one".

[0057] In this article, the terms "comprise", "include", "have", "contain" or any other similar terms are open-ended transitional phrases, which are intended to cover non-exclusive inclusions. For example, a composition or product containing multiple elements is not limited to the elements listed in this article, but may also include other elements that are not explicitly listed but are generally inherent to the composition or product. In addition, unless otherwise explicitly stated, the term "or" refers to an inclusive "or" rather than an exclusive "or". For example, any of the following situations satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), A and B are both true (or exist). In addition, in this article, the interpretation of the terms "comprise", "include", "have", and "contain" should be considered to have been specifically disclosed and simultaneously cover closed transitional phrases such as "consisting of", "consisting of", "the balance is", and "substantially consisting of", "mainly consisting of", "mainly consisting of", "basically containing", "basically consisting of", "basically consisting of", "essentially containing" and other transitional phrases.

[0058] In this article, all features or conditions such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are only for simplicity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be deemed to have covered and specifically disclosed all possible sub-ranges and individual values ​​within the range (including integers and fractions), especially integer values. For example, the range description of "1.0 to 8.0" or "between 1.0 and 8.0" or "between 1.0 and 8.0" should be deemed to have specifically disclosed all sub-ranges 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, etc., and should be deemed to cover endpoint values, especially sub-ranges defined by integer values, and should be deemed to have specifically disclosed individual values ​​such as 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, etc. Unless otherwise indicated, the foregoing method of interpretation applies to all contents of the entire application, regardless of whether the scope is broad or not.

[0059] 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 a better value) of the range and the lower limit or preferred value (or a better value) of the range have been specifically disclosed herein, regardless of whether these ranges are disclosed separately. In addition, if a numerical range is mentioned herein, unless otherwise specified, the range should include its endpoints and all integers and fractions within the range.

[0060] 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.

[0061] Unless otherwise specified, in this application, a compound refers to a chemical substance formed by two or more elements connected by chemical bonds, including small molecule compounds and polymer compounds, but not limited thereto. The interpretation of a compound in this article is not limited to a single chemical substance, but can also be interpreted as the same type of chemical substances with the same composition or the same properties.

[0062] Unless otherwise specified, the "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.

[0063] If not otherwise specified, in the present application, modified products include products after modification of reactive functional groups of each resin, products after prepolymerization of each resin with other resins, products after crosslinking of each resin with other resins, products after copolymerization of each resin with other resins, and the like.

[0064] If not otherwise specified, the unsaturated bonds described in the present application refer to reactive unsaturated bonds, such as but not limited to unsaturated double bonds that can undergo cross-linking reactions with other functional groups, such as but not limited to unsaturated carbon-carbon double bonds that can undergo cross-linking reactions with other functional groups.

[0065] Unless otherwise specified, in this application, parts by weight represent relative parts by weight in a composition, which may be any weight unit, such as but not limited to kilograms, 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.

[0066] 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.

[0067] The present application will be described below with specific implementations and examples. It should be understood that these specific implementations and examples are merely illustrative and are not intended to limit the scope of the present application and its use.

[0068] 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.

[0069] In the following descriptions: Polyethylene film: thickness is 9um and porosity is 40%.

[0070] Sodium carboxymethyl cellulose: active ingredient content ≥99.99%.

[0071] Sodium polyacrylate: Active ingredient content ≥99.99%.

[0072] α-Al 2 O 3 : Content ≥99.99%, with two average particle sizes of 60nm and 80nm.

[0073] 3-Chloropropyltrimethoxysilane: active ingredient content ≥99.99%, density 1.09g / ml, boiling point 195℃, pH=7.

[0074] Methacryloyloxypropyltrimethoxysilane (KH-570 silane coupling agent): active ingredient content ≥ 99.5%, density 0.9510±0.005kg / m³.

[0075] 3-Aminotriethoxysilane: active ingredient content ≥99%, density 1.081g / ml, boiling point, boiling point 195℃~196℃.

[0076] Thermoplastic polyester elastomer (TPEE): hardness is 55D.

[0077] High-density polyethylene: The elastic modulus at room temperature is 1.06 GPa.

[0078] Polypropylene: The elastic modulus at room temperature is 1.52 GPa.

[0079] Polyethylene terephthalate film (PET): elastic modulus at room temperature is 2.12 GPa, with two thickness specifications of 2μm and 4μm.

[0080] Epoxy resin film: elastic modulus 3.41 GPa at room temperature, thickness 2 μm.

[0081] Polypropylene film: elastic modulus at room temperature is 0.86 GPa, thickness is 2 μm.

[0082] Preparation Example Preparation Example 1 The raw materials used in this preparation example include, by weight: 1 part of 3-chloropropyltrimethoxysilane and 1 part of high-density polyethylene.

[0083] The preparation method of this preparation example comprises: uniformly mixing the above raw materials at room temperature to obtain an adhesive.

[0084] Preparation Example 2 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.

[0085] Preparation Example 3 The raw materials used in this preparation example include, by weight: 1 part of methacryloxypropyltrimethoxysilane and 1 part of high-density polyethylene.

[0086] The preparation method of this preparation example comprises: uniformly mixing the above raw materials at room temperature to obtain an adhesive.

[0087] Preparation Example 4 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.

[0088] Preparation Example 5 The raw materials used in this preparation example include, by weight: 1 part of 3-aminotriethoxysilane and 1 part of high-density polyethylene.

[0089] The preparation method of this preparation example comprises: uniformly mixing the above raw materials at room temperature to obtain an adhesive.

[0090] Preparation Example 6 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.

[0091] Preparation Example 7 The raw materials used in this preparation example include, by weight: 1 part of 3-chloropropyltrimethoxysilane and 1 part of polypropylene.

[0092] The preparation method of this preparation example comprises: uniformly mixing the above raw materials at room temperature to obtain an adhesive.

[0093] Preparation Example 8 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.

[0094] Preparation Example 9 The raw materials used in this preparation example include, by weight: 1 part of methacryloxypropyltrimethoxysilane and 1 part of polypropylene.

[0095] The preparation method of this preparation example comprises: uniformly mixing the above raw materials at room temperature to obtain an adhesive.

[0096] Preparation Example 10 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.

[0097] Preparation Example 11 The raw materials used in this preparation example include, by weight: 1 part of 3-aminotriethoxysilane and 1 part of polypropylene.

[0098] The preparation method of this preparation example comprises: uniformly mixing the above raw materials at room temperature to obtain an adhesive.

[0099] Preparation Example 12 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.

[0100] Preparation Example 13 The raw materials used in this preparation example include: a polyethylene terephthalate film with a thickness of 2 μm.

[0101] Reference Figure 1 and Figure 2 In this preparation example, the connection part extends along the length direction of the base film, the number of the connection parts is two, the two connection parts are parallel to each other, and the distance between the two connection parts is smaller than the width of the base film.

[0102] In this preparation example, the connecting part is strip-shaped, and the width of the connecting part is 2 μm. In this preparation example, both ends of the support part are connected to a connecting part respectively, the thickness of the support part is equal to any connecting part, the width of the support part is 4 μm, and the distance between two adjacent support parts is 0.02 cm.

[0103] In this preparation example, a plurality of support parts and two connecting parts integrally form a belt-shaped support belt, and the support belt is obtained by cutting a polyethylene terephthalate film by ultraviolet laser, and the width of the support belt is 9 cm.

[0104] Preparation Example 14 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.

[0105] Preparation Example 15 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.

[0106] Preparation Example 16 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.

[0107] Preparation Example 17 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.

[0108] Preparation Example 18 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.

[0109] Example Example 1 The raw materials used in this embodiment include, by weight: 100 parts of α-Al 2 O 3 , 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.

[0110] The preparation method of this embodiment includes: S1, 25 ℃, α-Al 2 O 3 , TPEE, sodium carboxymethyl cellulose, sodium polyacrylate, water and adhesive are uniformly mixed to prepare slurry; S2, firstly coat the slurry on a 10 cm wide polyethylene film by gravure printing, then lay the support tape on the coated slurry, the long edges of the support tape and the polyethylene film are both 0.5 cm, the coating thickness is 2 μm, and then heat at 80°C until the surface of the slurry is solid to obtain the primary layer; 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.

[0111] Example 2 The difference between this embodiment and embodiment 1 is that in the raw materials used in this embodiment, the average particle size of TPEE is 60 nm.

[0112] Example 3 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.

[0113] Example 4 The difference between this embodiment and embodiment 1 is that: in the raw materials used in this embodiment, α-Al 2 O 3 The average particle size of 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.

[0114] Example 5 The difference between this embodiment and embodiment 4 is that: among the raw materials used in this embodiment, the support tape comes 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.

[0115] Example 6 The difference between this embodiment and embodiment 1 is that: α-Al 2 O 3 The average particle size is 80nm, the amount of TPEE is 15 parts, the support tape comes from Preparation Example 16, the adhesive comes from Preparation Example 3, and the amount of adhesive is 11.5 parts; the coating thickness in step S2 is 3μm; the maximum coating thickness in step S3 is 5μm, so that the total thickness on the polyethylene film is 8μm.

[0116] Example 7 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.

[0117] Example 8 The difference between this embodiment and embodiment 7 is that the support tape comes from preparation example 17, and the adhesive comes 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 is solid, thereby obtaining a primary layer.

[0118] Example 9 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 is solid, thereby obtaining a primary layer.

[0119] Example 10 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 is solid, thereby obtaining a primary layer.

[0120] Embodiment 11 The difference between this embodiment and embodiment 8 is that the adhesive is derived from preparation example 7.

[0121] Example 12 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 is solid, thereby obtaining a primary layer.

[0122] Example 13 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 is solid, thereby obtaining a primary layer.

[0123] Embodiment 14 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 is solid, thereby obtaining a primary layer.

[0124] Embodiment 15 The difference between this embodiment and embodiment 8 is that: the adhesive comes 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.

[0125] Example 16 The difference between this embodiment and Embodiment 8 is that the adhesive is derived from Preparation Example 12.

[0126] Comparative Example Comparative Example 1 The raw materials used in this comparative example include, by weight: 100 parts of α-Al 2 O 3 , 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.

[0127] The preparation method of this comparative example comprises: D1, 25 ℃, α-Al 2 O 3 , TPEE, sodium carboxymethyl cellulose, sodium polyacrylate, water and adhesive are uniformly mixed to prepare slurry; D2. The slurry was coated on a polyethylene film with a width of 10 cm by gravure printing process with a coating thickness of 6 μm, and then dried at 120° C. to obtain a lithium battery separator.

[0128] Comparative Example 2 The difference between this comparative example and comparative example 1 is that the support belt comes from preparation example 18.

[0129] Comparative Example 3 The difference between this comparative example and comparative example 1 is that the average particle size of TPEE is 20 nm.

[0130] Comparative Example 4 The difference between this comparative example and comparative example 1 is that the average particle size of TPEE is 80 nm.

[0131] Comparative Example 5 The difference between this comparative example and comparative example 1 is that the amount of TPEE used is 5 parts.

[0132] Comparative Example 6 The difference between this comparative example and comparative example 1 is that the amount of TPEE used is 20 parts.

[0133] Comparative Example 6 The difference between this comparative example and comparative example 4 is that high-density polyethylene is used as the adhesive.

[0134] Performance Testing The lithium battery separators prepared in Examples 1 to 16 and Comparative Examples 1 to 7 were tested according to the following test items: (1) Determination of puncture strength: According to the provisions of GB / T36363-2018, the samples are tested at 25°C and 80°C respectively; (2) Hot and cold alternating test: the drop in puncture strength after the test sample is alternately placed at 125°C and -20°C for 50 times; (3) Ionic conductivity test: The test is conducted in accordance with the provisions of section 6.2.2 Ionic conductivity performance test of the national standard GB / T36363-2018 “Polyolefin separators for lithium batteries”.

[0135] Test Results 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, some simple deductions or substitutions can be made without departing from the concept of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope 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, the ceramic layer is arranged on the base film, the ceramic layer comprises ceramic particles, elastic particles and an adhesive, and the elastic modulus of the adhesive at 25° C. after curing is 1.1 GPa to 1.6 GPa; A plurality of support members, wherein the plurality of support members are all 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.

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. A 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. A 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. A 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 are 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. A 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 sum of the mass of the ceramic particles and the elastic particles, and the adhesive resin accounts for 8% to 12% of the sum of the 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 as claimed in claim 1, characterized in that: The steps include: Preparing slurry: preparing ceramic particles, elastic particles and a binder into slurry; First coating: first coat 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: Coat the slurry on the primary layer again, 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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