Separator, and electrochemical device and electronic device including same

Abstract

The invention relates to a diaphragm and an electrochemical device and an electronic device comprising the same, and belongs to the technical field of electrochemical energy storage. The diaphragm comprises a porous base material and a coating located on at least one side surface of the porous base material, wherein the coating contains melamine salt; the melamine salt is spherical or irregular granular; the volume distribution particle size Dv10 of the melamine salt is a [mu] m, the volume distribution particle size Dv90 of the melamine salt is c [mu] m, and c / a is larger than or equal to 3.0 and smaller than or equal to 13.0. The diaphragm can improve the thermal safety performance and high-temperature cycle performance of the battery.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, and more specifically, to diaphragms and electrochemical and electronic devices comprising them. Background Technology

[0002] Commercial polyolefin separators (such as PP / PE) are prone to melting and shrinkage at high temperatures and are highly flammable. When the battery is short-circuited or overcharged, the polyolefin separator is prone to failure, which can cause the electrolyte to burn, leading to thermal runaway or even an explosion. Summary of the Invention

[0003] The purpose of this application is to overcome the shortcomings of the prior art and provide a diaphragm and an electrochemical and electronic device comprising the diaphragm.

[0004] To achieve the above objectives, the technical solution adopted in this application is as follows: A first aspect of this application provides a diaphragm comprising a porous substrate and a coating located on at least one surface of the porous substrate, the coating comprising a melamine salt; The melamine salt is in the form of spherical or irregular granules; the volume distribution particle size of the melamine salt is a μm for Dv10 and c μm for Dv90, and satisfies: 3.0≤c / a≤13.0.

[0005] In some embodiments of this application, the melamine salt satisfies at least one of the following conditions: (1)0.1μm≤Dv10≤0.8μm; (2)1.0μm≤Dv90≤2.8μm; (3) The density is 1.0 g / cm³ 3 Up to 3.0 g / cm 3 ; (4) Specific surface area is 4.0 m² 2 / g to 12.0m 2 / g; (5) The pH value is 7.0 to 8.0; (6) Melamine salts include at least one of melamine cyanurate, melamine polyphosphate, melamine thiocyanate, melamine hydrofluoric acid, melamine phosphate, melamine pyrophosphate, melamine borate, melamine phthalate, and melamine oxalate.

[0006] In some embodiments of this application, the volume distribution particle size Dv50 of the melamine salt is b μm, and satisfies: 1.0≤(ca) / b≤11.5.

[0007] In some embodiments of this application, the volume distribution particle size Dv50 of the melamine salt satisfies: 0.2μm≤Dv50≤2.0μm.

[0008] In some embodiments of this application, the areal density per unit thickness of the coating is dg / (m²). 2 (·μm), and satisfy: 0.5≤c / d≤5.0.

[0009] In some embodiments of this application, the areal density per unit thickness of the coating is 0.2 g / (m²). 2 ·μm) to 1.2g / (m 2 ·μm).

[0010] In some embodiments of this application, the coating satisfies at least one of the following conditions: (1) The average thickness of the coating is 1.2 μm to 2.8 μm; (2) The areal density of the coating is 1.0 g / m³. 2 Up to 3.0g / m 2 ; (3) The melamine salt accounts for 80% to 99% of the total mass of the coating.

[0011] In some embodiments of this application, the diaphragm or the porous substrate satisfies at least one of the following conditions: (1) The air permeability of the diaphragm is 50 sec / 100cc to 300 sec / 100cc; (2) The elongation of the diaphragm in its transverse direction is 40% to 100%; (3) The elongation of the diaphragm in its longitudinal direction is 30% to 150%; (4) The tensile strength of the diaphragm in its transverse direction is 1000 MPa to 4000 MPa; (5) The tensile strength of the diaphragm in its longitudinal direction is 1000 MPa to 4000 MPa; (6) The melting point of the porous substrate is 130°C to 170°C; (7) The thickness of the porous substrate is 3 μm to 12 μm; (8) The porosity of the porous substrate is 30% to 70%.

[0012] A second aspect of this application provides an electrochemical device comprising the diaphragm provided in the first aspect of this application.

[0013] A third aspect of this application provides an electronic device that includes the electrochemical device provided in the second aspect of this application.

[0014] Compared with the prior art, the beneficial effects of this application are as follows: The coating of the separator in this application contains spherical or irregularly shaped melamine salts. The melamine salts can stabilize the electrolyte and inhibit the generation of hydrogen fluoride, thereby reducing the concentration of hydrogen fluoride in the battery, improving the structural stability of the positive electrode, and reducing the gas production volume. At the same time, by controlling the ratio of the volume distribution particle size Dv90 to Dv10 of the melamine salts, the uniformity of the coating is improved, local defects are reduced, and the contact area between the melamine salts and the porous substrate is increased, promoting its embedding in the microstructure of the porous substrate. This enhances the bonding force between the coating and the porous substrate, thereby improving the thermal safety performance and high-temperature cycle performance of the battery. Attached Figure Description

[0015] The embodiments described in this application are not limited to the accompanying drawings, which are only some of the embodiments described herein. Those skilled in the art can obtain drawings of other embodiments based on the content of this application.

[0016] Figure 1 This is a SEM image of the coating surface in a diaphragm according to one embodiment of this application. Detailed Implementation

[0017] To better illustrate the purpose, technical solution, and advantages of this application, the following detailed description, in conjunction with specific embodiments, aims to explain the content of this application in detail, rather than to limit it. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this application.

[0018] <General Definition> The term "porous substrate" refers to a substrate having pores or voids within it. Materials used as porous substrates can be organic or inorganic, provided they are electrically insulating. This application may use any electrically insulating porous substrate.

[0019] The term "melamine salt" refers to salt compounds formed by the reaction of melamine with organic or inorganic acids.

[0020] The term "spherical" refers to particles that have a spherical shape or are substantially spherical in shape.

[0021] The term "irregular granular" refers to granules that are asymmetrical or lack symmetry in shape, and whose surfaces may be rough, porous, or have complex textures.

[0022] The term "polymer" refers to natural high molecular weight compounds or synthetic high molecular weight compounds prepared by polymerizing the same or different types of monomers. Synthetic high molecular weight compounds include, but are not limited to, homopolymers, copolymers, trimers, polymers, and interpolymers.

[0023] The term "volume distribution particle size Dv50" refers to the particle size that, in the volumetric particle size distribution of a material, reaches 50% of the cumulative volume, starting from the smallest particle size.

[0024] The term "volume distribution particle size Dv10" refers to the particle size that, in the volumetric particle size distribution of a material, reaches 10% of the cumulative volume, starting from the smallest particle size.

[0025] The term "volume distribution particle size Dv90" refers to the particle size that, in the volumetric particle size distribution of a material, reaches 90% of the cumulative volume, starting from the smallest particle size.

[0026] In the following description, all figures disclosed in this application are approximations.

[0027] Throughout this specification, references to “implementation,” “partial implementation,” “one implementation,” “another enumerated method,” “specific method,” or “partial method” mean that at least one implementation or embodiment in this application includes the specific features, structures, materials, or characteristics described in that implementation or embodiment.

[0028] I. Diaphragm This application provides a diaphragm comprising a porous substrate and a coating located on at least one surface of the porous substrate, the coating comprising a melamine salt; Melamine salts are spherical or irregular granules; the volume distribution particle size of melamine salts is a μm for Dv10 and c μm for Dv90, and satisfies: 3.0≤c / a≤13.0.

[0029] The coating of the separator in this application contains spherical or irregularly shaped melamine salts. The melamine salts can stabilize the electrolyte and inhibit the generation of hydrogen fluoride, thereby reducing the concentration of hydrogen fluoride in the battery, improving the structural stability of the positive electrode, and reducing the gas production volume. At the same time, by controlling the ratio of the volume distribution particle size Dv90 to Dv10 of the melamine salts, the uniformity of the coating is improved, local defects are reduced, and the contact area between the melamine salts and the porous substrate is increased, promoting its embedding in the microstructure of the porous substrate. This enhances the bonding force between the coating and the porous substrate, thereby improving the thermal safety performance and high-temperature cycle performance of the battery.

[0030] "Coating located on at least one surface of a porous substrate" means that the coating can be located on one surface of the porous substrate along its own thickness direction, or on two surfaces of the porous substrate along its own thickness direction.

[0031] In some implementations, the calculated value of c / a may be, but is not limited to, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, 11.5, 12.0, 12.5, or 13.0, or fall within the range of any two of the above values.

[0032] In some embodiments, the permeability of the diaphragm is from 50 sec / 100cc to 300 sec / 100cc, for example, but not limited to 50 sec / 100cc, 60 sec / 100cc, 70 sec / 100cc, 80 sec / 100cc, 90 sec / 100cc, 100 sec / 100cc, 110 sec / 100cc, 120 sec / 100cc, 130 sec / 100cc, 140 sec / 100cc, 150 sec / 100cc, 160 sec / 100cc. 170sec / 100cc, 180sec / 100cc, 190sec / 100cc, 200sec / 100cc, 210sec / 100cc, 220sec / 100cc, 230sec / 100cc, 240sec / 100cc, 250sec / 100cc, 260sec / 100cc, 270sec / 100cc, 280sec / 100cc, 290sec / 100cc, or 300sec / 100cc, or within the range of any two of the above values. When the permeability of the separator is within the above range, Li⁺ has low resistance and a short migration path in the electrolyte, and high ionic conductivity. When the battery is charged and discharged at high rates (such as fast charging and high current discharge, which are common in electric vehicles and energy storage scenarios), Li⁺ can migrate quickly between the positive and negative electrodes, avoiding voltage drop and capacity decay due to "insufficient ion supply", resulting in better rate performance.

[0033] In some embodiments, the elongation of the diaphragm in its transverse direction (TD) is 40% to 100%, for example, but not limited to 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, or 100%, or within the range of any two of the above values.

[0034] In some embodiments, the elongation of the diaphragm in its longitudinal direction (MD) is 30% to 150%, for example, but not limited to 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 115%, 120%, 125%, 130%, 135%, 140%, 145%, or 150%, or within the range of any two of the above values.

[0035] When the elongation of the separator in its transverse direction (TD) or longitudinal direction (MD) is within the above range, it can better absorb the stress of electrode expansion through a certain elastic deformation during battery charging and discharging, thereby maintaining the integrity of the separator's microporous structure and promoting tight adhesion between the separator and the positive and negative electrodes, ensuring the stability of the ion transport channels, and thus improving the battery's cycle life and safety performance.

[0036] In some embodiments, the tensile strength of the diaphragm in its transverse direction (TD) is 1000 MPa, 1200 MPa, 1400 MPa, 1600 MPa, 1800 MPa, 2000 MPa, 2200 MPa, 2400 MPa, 2600 MPa, 2800 MPa, 3000 MPa, 3200 MPa, 3400 MPa, 3600 MPa, 3800 MPa, or 4000 MPa, or falls within the range of any two of the above values.

[0037] In some embodiments, the tensile strength of the diaphragm in its longitudinal direction (MD) is 1000 MPa, 1200 MPa, 1400 MPa, 1600 MPa, 1800 MPa, 2000 MPa, 2200 MPa, 2400 MPa, 2600 MPa, 2800 MPa, 3000 MPa, 3200 MPa, 3400 MPa, 3600 MPa, 3800 MPa, or 4000 MPa, or falls within the range of any two of the above values.

[0038] When the tensile strength of the separator in its transverse (TD) or longitudinal (MD) direction is within the above range, it can not only better ensure the stability of the battery assembly process and reduce the production defect rate, but also resist the volume expansion of the electrodes during charge and discharge cycles, thereby better maintaining the structural integrity of the separator.

[0039] <Porous Substrates> In some embodiments, the porous substrate comprises woven or nonwoven polymer fibers. In some embodiments, the porous substrate is a nonwoven material comprising polymer fibers.

[0040] In some embodiments, the porous substrate is, but is not limited to, at least one of polyolefin, polyester, polyacetal, polyamide, polyethylene terephthalate, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, polyacrylonitrile, polyvinylidene fluoride, polyoxymethylene, polyoxymethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, polysulfone, and polymethyl methacrylate.

[0041] Some non-limiting examples of polyolefins include at least one of polyethylene (PE), ultra-high molecular weight polyethylene (UHMWPE), high-density polyethylene (HDPE), polypropylene (PP), polyethylene-polypropylene copolymer (PE-PP), and polyethylene-polypropylene-polyethylene copolymer.

[0042] In some embodiments, the melting point of the porous substrate is between 130°C and 170°C, for example, but not limited to, 130°C, 132°C, 134°C, 136°C, 138°C, 140°C, 142°C, 144°C, 146°C, 148°C, 150°C, 152°C, 154°C, 156°C, 158°C, 160°C, 162°C, 164°C, 166°C, 168°C, or 170°C, or falls within the range of any two of the above values. A melting point within this range allows the membrane to more effectively close its pores under high-temperature conditions, thereby preventing thermal runaway and improving safety.

[0043] In some embodiments, the thickness of the porous substrate is from 3 μm to 12 μm, for example, but not limited to 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, or 12 μm, or within any two of the above values. A porous substrate thickness within the above range not only enables the separator to have higher puncture strength to better suppress lithium dendrites, but also maintains lower internal resistance and higher energy density.

[0044] In some embodiments, the porosity of the porous substrate is 30% to 70%, for example, but not limited to 30%, 32%, 35%, 37%, 40%, 43%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 63%, 65%, 68%, or 70%, or within any two of the above values. A porosity within this range not only benefits the membrane by providing more ion channels, thereby reducing internal resistance and improving charge / discharge efficiency and high-rate discharge capability, but also gives the membrane higher mechanical strength, thus reducing the risk of lithium dendrite penetration.

[0045] <Coating> In some embodiments, the areal density (d) per unit thickness of the coating and the volume distribution particle size Dv90 (c) of the melamine salt satisfy: 0.5 ≤ c / d ≤ 5.0. For example, the calculated value of c / d can be, but is not limited to, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8 or 5.0, or fall within the range of any two of the above values. When the ratio of the volume distribution particle size Dv90 of melamine salt to the areal density per unit thickness of the coating is within the above range, the particle size and packing density of melamine salt can be better matched. The melamine salt particles are uniformly filled by the binder, and the coating has neither excessive agglomeration nor large gaps, thus combining crack resistance and flexibility, thereby better ensuring the integrity of the coating during long-term use.

[0046] In some embodiments, the areal density per unit thickness of the coating is 0.2 g / (m²). 2 ·μm) to 1.2g / (m 2 (·μm), for example, it can be, but is not limited to, 0.2g / (m 2 ·μm), 0.3g / (m 2 ·μm), 0.4g / (m 2 ·μm), 0.5g / (m 2 ·μm), 0.6g / (m 2 ·μm), 0.7g / (m 2 ·μm), 0.8g / (m 2 ·μm), 0.9g / (m 2 ·μm), 1.0g / (m 2 ·μm), 1.1g / (m 2 ·μm) or 1.2g / (m 2 The areal density per unit thickness of the coating (μm) or within the range of any two of the above values ​​is considered to be within the specified range. A areal density within this range better ensures sufficient melamine salt content and a dense structure in the coating.

[0047] In some embodiments, the average thickness of the coating is from 1.2 μm to 2.8 μm, for example, but not limited to 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, or 2.8 μm, or within any two of the above values. The average thickness of the coating refers to the average thickness of the porous coating on one side of the porous substrate. An average coating thickness within the above range allows for a better balance between the coating's ion transport efficiency and its protective capability.

[0048] In some embodiments, the areal density of the coating is 1.0 g / m³. 2 Up to 3.0g / m 2 For example, it can be, but is not limited to, 1.0 g / m³. 2 1.1g / m 2 1.2g / m 2 1.3g / m 2 1.4g / m 2 1.5g / m 2 1.6g / m 2 1.7g / m 2 1.8g / m 2 1.9g / m 2 2.0g / m 2 2.1g / m 2 2.2g / m 2 2.3g / m 2 2.4g / m 2 2.5g / m 2 2.6g / m 2 2.7g / m 2 2.8g / m 2 2.9g / m 2 Or 3.0g / m 2 The areal density of the coating is within the range of any two of the above values, or within the range of any two of the above values. Sufficient melamine salt content within this range is beneficial for improving the thermal safety performance of the battery.

[0049] In some embodiments, the melamine salt content is between 80% and 99% based on the total mass of the coating. For example, it can be, but is not limited to, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%, or falls within any range of two of the aforementioned values. A melamine salt content within the above range is more conducive to forming a stable coating structure during the coating process.

[0050] In some embodiments, the coating may also contain inorganic fillers, which may include boehmite, ceramic fibers, Al2O3, SiO, SiO2, CaO, ZnO, TiO2, ZrO2, Mg(OH)2, MgO, SnO2, CaCO3, BaSO4, BaTi2O5, BaTiO3, TiN, AlN, Na2O·mTiO2 (m is 3 or 6), K2O·nTiO2 (n is 1, 2, 4, 6 or 8), BaO x (x is 1 or 2), MTiO3 (M is Ba, Sr or Ca) at least one of the following. Preferably, the inorganic particles include at least one of silica particles, barium disitinathate particles, zirconium dioxide particles, alumina particles, barium metatitanate particles, barium sulfate particles, tin oxide particles, titanium nitride particles, aluminum nitride particles, silica particles, calcium oxide particles, magnesium oxide particles, magnesium hydroxide particles, zinc oxide particles, titanium dioxide particles, boehmite particles, hydrated alumina particles, and ceramic particles.

[0051] This application does not impose any particular restrictions on the shape of the inorganic filler, as long as it can achieve the purpose of this application.

[0052] Inorganic fillers can be spherical, rod-shaped, sheet-shaped, disc-shaped, needle-shaped, cylindrical, irregular, or other known particle shapes. In some embodiments, the inorganic material is not spherical, rod-shaped, sheet-shaped, disc-shaped, needle-shaped, cylindrical, or irregular. Preferably, the inorganic filler is spherical. Spherical particles have a higher packing density, can form a continuous thermally conductive network, reduce the risk of local thermal runaway, and have a small surface curvature, a low contact angle with the electrolyte, higher liquid absorption, and better wettability.

[0053] Melamine salts In some embodiments, the volume distribution particle size Dv10 of the melamine salt is from 0.1 μm to 0.8 μm, for example, but not limited to 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, or 0.8 μm, or within any two of the above values. A volume distribution particle size Dv10 of melamine salt within the above range is more conducive to forming a suitable coating structure, ensuring efficient lithium-ion transport while preventing electrode particle embedding.

[0054] In some embodiments, the volume distribution particle size Dv90 of the melamine salt is from 1.0 μm to 2.8 μm, for example, but not limited to 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, or 2.8 μm, or falls within the range of any two of the above values. A volume distribution particle size Dv90 of melamine salt within the above range is more conducive to forming a suitable coating structure, ensuring efficient lithium-ion transport while preventing electrode particle embedding.

[0055] In some embodiments, the density of melamine salt is 1.0 g / cm³. 3 Up to 3.0 g / cm 3 For example, it can be, but is not limited to, 1.0 g / cm³. 3 1.1g / cm 3 1.2g / cm 3 1.3g / cm 3 1.4g / cm 3 1.5g / cm 3 1.6g / cm 3 1.7g / cm 3 1.8g / cm 3 1.9g / cm 3 2.0g / cm 3 2.1g / cm 3 2.2g / cm 3 2.3g / cm 3 2.4g / cm 3 2.5g / cm 3 2.6g / cm 3 2.7g / cm 3 2.8g / cm 3 2.9g / cm 3 Or 3.0g / cm 3The density of melamine salt within the above range is more conducive to improving the compactness of the coating, thereby better suppressing the shrinkage of the porous substrate at high temperatures. Even if the porous substrate softens due to heat, the structural integrity of the coating can be maintained, thus effectively preventing short circuits between the positive and negative electrodes.

[0056] In some embodiments, the specific surface area of ​​the melamine salt is 4.0 m². 2 / g to 12.0m 2 / g, for example, can be but is not limited to 4.0m 2 / g, 4.5m 2 / g, 5.0m 2 / g, 5.5m 2 / g, 6.0m 2 / g, 6.5m 2 / g, 7.0m 2 / g, 7.5m 2 / g, 8.0m 2 / g, 8.5m 2 / g, 9.0m 2 / g, 9.5m 2 / g, 10.0m 2 / g, 10.5m 2 / g, 11.0m 2 / g, 11.5m 2 / g or 12.0m 2 / g, or within the range of any two of the above values. A specific surface area of ​​melamine salt within the above range is beneficial for improving the thermomechanical stability and heat dissipation performance of the separator, thereby better improving the thermal safety performance and high-temperature cycle performance of the battery.

[0057] The specific surface area of ​​melamine salts can be controlled by adjusting the reaction conditions of their preparation method.

[0058] In some implementations, reducing the initial concentrations of melamine and cyanuric acid in the reaction system reduces the probability of particle collision and aggregation, which is conducive to the formation of fine assemblies, thereby increasing the specific surface area.

[0059] In some implementations, the reaction rate is slow at low temperatures (40°C to 60°C), crystal growth is slow, and porous or loose structures are easily formed, which is beneficial to increasing the specific surface area; high temperatures easily lead to particle sintering and agglomeration, which is beneficial to reducing the specific surface area.

[0060] In some implementations, the pH of the reaction system is controlled within the range of 5 to 7, the solubility of melamine and cyanuric acid is moderate, the crystallization process is uniform, particle aggregation caused by local supersaturation is avoided, and the specific surface area is increased.

[0061] In some embodiments, the pH value of the melamine salt is 7.0 to 8.0, for example, but not limited to 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, or 8.0, or within any two of the above values. A pH value within this range not only better reduces the introduction of acid into the battery but also helps reduce its direct reactivity with the electrolyte, thereby improving the battery's thermal safety and high-temperature cycling performance.

[0062] In some embodiments, the melamine salt includes at least one of melamine cyanurate, melamine polyphosphate, melamine thiocyanate, melamine hydrofluoric acid, melamine phosphate, melamine pyrophosphate, melamine borate, melamine phthalate, and melamine oxalate.

[0063] In some embodiments, the volume distribution particle sizes Dv50(b) of the melamine salt satisfy the following condition: 1.0 ≤ (ca) / b ≤ 11.5. A calculated value of (ca) / b within this range is more conducive to improving the uniformity of coating deposition, eliminating obvious dense / loose regions, enhancing the consistency of lithium-ion migration impedance within the coating, and promoting uniform current distribution during battery charging and discharging, thereby reducing the risk of lithium dendrite formation and localized heating.

[0064] In some implementations, the calculated value of (ca) / b may be, but is not limited to, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0, or 11.5, or fall within the range of any two of the above values.

[0065] In some embodiments, the volume distribution particle size Dv50 of the melamine salt is from 0.2 μm to 2.0 μm, for example, but not limited to 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, or 2.0 μm, or falls within the range of any two of the above values. A volume distribution particle size Dv50 of melamine salt within the above range is more conducive to forming a suitable coating structure, ensuring efficient lithium-ion transport while preventing electrode particle embedding.

[0066] <Adhesive> The coating of the diaphragm in this application also includes an adhesive, which can be a water-soluble or oil-soluble organic polymer. It is mainly used to provide the adhesion and bonding performance of melamine salt to the porous substrate, and also provides certain heat resistance.

[0067] In some embodiments, the adhesive may include polyvinylidene fluoride (PVDF), polyester, polyamide, polyether, polycarboxylate, polycarboxylic acid, polyvinyl compounds, polyolefins, rubber, polyvinylpyrrolidone, polyacrylic acid, polyacrylate, polymethacrylic acid, polymethacrylate, polystyrene, polyvinyl alcohol, polyvinyl acetate, polyacrylamide, cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, carboxymethyl cellulose, cyanoethyl cellulose, cyanoethyl sucrose, polyurethane, nitrile rubber, styrene-butadiene rubber, styrene-acrylic rubber, latex, acrylonitrile-styrene-butadiene copolymer, halogenated polymer, fluorinated polymer, chlorinated polymer, unsaturated polymer, acrylic acid-acrylonitrile-acrylamide copolymer, acrylic acid-acrylonitrile-acrylate copolymer, conjugated diene polymers, and combinations thereof.

[0068] In some implementations, the adhesive content is 2% to 8% of the total mass of the coating, for example, but not limited to 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5% or 8%, or within any two of the above values.

[0069] Thickener Preferably, the coating of the diaphragm in this application further includes a thickener, the main function of which is to stabilize the viscosity of the coating slurry to prevent particle sedimentation and agglomeration, and to improve the adhesion of the coating slurry to the porous substrate during coating.

[0070] In some embodiments, the thickener may be, but is not limited to, at least one of methylcellulose, hydroxyethylcellulose, hydroxypropyl methylcellulose, polyvinyl alcohol, polyurethane, and polyacrylates.

[0071] In some implementations, the thickener is present in a mass ratio of 0.2% to 3% based on the total mass of the coating, for example, but not limited to 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, or 3%, or within any two of the above values.

[0072] <Wetting agent> Preferably, the coating of the diaphragm in this application further includes a wetting agent, the main function of which is to improve the wetting and spreading properties of the coating slurry on the porous substrate, enhance the smoothness and flatness of the coating surface, and prevent defects such as pinholes and edge shrinkage caused by the low surface tension of the porous substrate.

[0073] In some embodiments, the wetting agent may be, but is not limited to, at least one of ethylene oxide adducts, polyether silicone compounds, and nonionic fluorocarbon polymer compounds.

[0074] In some embodiments, the wetting agent is 0.05% to 2% of the total mass of the coating, for example, but not limited to 0.05%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8% or 2%, or within any two of the above values.

[0075] <Preparation of the diaphragm> The preparation method of the diaphragm may include the following steps: applying a coating slurry to the surface of one side of a porous substrate, drying it to form a coating, and obtaining a diaphragm.

[0076] In some embodiments, the drying process of the coating slurry may be vacuum drying.

[0077] In some embodiments, the drying temperature of the coating slurry can be from 40°C to 60°C.

[0078] In some embodiments, the coating slurry can be applied by any of the following methods: gravure coating, extrusion coating, dip coating, spray coating, dot coating, or wire rod coating.

[0079] II. Electrochemical Device This application provides an electrochemical device, including any apparatus in which an electrochemical reaction occurs to interconvert chemical energy and electrical energy. Specific, non-limiting examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0080] In some embodiments, the electrochemical device includes a positive electrode, a negative electrode, an electrolyte, and a membrane located between the positive and negative electrodes, and the membrane used in the electrochemical device is any of the membranes described herein.

[0081] Positive electrode In some embodiments, the positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector.

[0082] In some embodiments, the positive current collector is a metal foil or a composite current collector. In some embodiments, the metal foil is an aluminum foil. The composite current collector may include a metal foil substrate and a conductive layer disposed on at least one side of the metal foil substrate.

[0083] In some embodiments, the conductive layer may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fiber, carbon nanofiber, graphitized carbon sheet, carbon tube, carbon nanotube, activated carbon, and mesoporous carbon.

[0084] In some embodiments, the positive electrode active material layer may include a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent.

[0085] In some embodiments, the positive electrode active material is selected from LiCoO2, LiNiO2, and LiNi x Mn y O2, Li 1+ z Ni x Mn y Co 1-x-y O2, LiNi x Co y Al z The group consisting of O2, LiV2O5, LiTiS2, LiMoS2, LiMnO2, LiCrO2, LiMn2O4, Li2MnO3, LiFeO2, LiFePO4, LiMnPO4, and combinations thereof, wherein each x is independently 0.2 to 0.9; each y is independently 0.1 to 0.45; and each z is independently 0 to 0.2. The positive electrode active material of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as positive electrode active materials.

[0086] In some embodiments, the positive electrode active material is selected from LiCoO2, LiNiO2, and LiNi x Mn y O2, Li 1+ z Ni x Mn y Co 1-x-y O2, LiNi x Co y Al z The group consisting of O2, LiV2O5, LiTiS2, LiMoS2, LiMnO2, LiCrO2, LiMn2O4, LiFeO2, LiFePO4 and combinations thereof, wherein each x is independently 0.4 to 0.6; each y is independently 0.2 to 0.4; and each z is independently 0 to 0.1.

[0087] In some embodiments, the positive electrode active material is Li 1+x Ni a Mn b Co c Al (1-a-b-c) O2; where -0.2≤x≤0.2, 0≤a<1, 0≤b<1, 0≤c<1 and a+b+c≤1.

[0088] In some embodiments, the positive electrode active material has the general formula Li 1+x Ni a Mn b Co c Al (1-a-b-c) O2, where 0.33≤a≤0.92, 0.33≤a≤0.9, 0.33≤a≤0.8, 0.5≤a≤0.92, 0.5≤a≤0.9, 0.5≤a≤0.8, 0.6≤a≤0.92 or 0.6≤a≤0.9; 0≤b≤0.5, 0≤b≤0.3, 0.1≤b≤0.5, 0.1≤b≤0.4, 0.1≤b≤0.3, 0.1≤b≤0.2 or 0.2≤b≤0.5; 0≤c≤0.5, 0≤c≤0.3, 0.1≤c≤0.5, 0.1≤c≤0.4, 0.1≤c≤0.3, 0.1≤c≤0.2 or 0.2≤c≤0.5.

[0089] In some embodiments, the positive electrode active material is doped with a dopant selected from the group consisting of Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, Si, Ge, and combinations thereof. In some embodiments, the dopant is not Fe, Ni, Mn, Mg, Zn, Ti, La, Ce, Ru, Si, or Ge. In some embodiments, the dopant is not Al, Sn, or Zr.

[0090] In some embodiments, the positive electrode active material may include LiNi. 0.33 Mn 0.33 Co 0.33 O2, LiNiO2, LiNi 0.4 Mn 0.4 Co 0.2 O2, LiNi 0.5 Mn 0.3 Co 0.2 O2, LiNi 0.6 Mn 0.2 Co 0.2 O2, LiNi 0.7 Mn 0.15 Co 0.15 O2, LiNi 0.8 Mn 0.1 Co 0.1O2, LiNi 0.92 Mn 0.04 Co 0.04 O2, LiNi 0.8 Co 0.15 Al 0.05 At least one of O2.

[0091] In some embodiments, the positive electrode binder includes at least one of polyvinylidene fluoride (PVDF), poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polyvinyl butyral, polyvinylpyrrolidone (PVP), acrylic acid-acrylonitrile-acrylamide copolymer, and acrylic acid-acrylonitrile-acrylate copolymer. The positive electrode binder of this application is not limited to the above materials, but also includes other materials that can be used as battery positive electrode binders.

[0092] In some embodiments, the positive electrode conductive agent may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon nanotubes, carbon nanotubes, activated carbon, and mesoporous carbon. The positive electrode conductive agent in this application is not limited to the above materials, but also includes other materials that can be used as positive electrode conductive agents in batteries.

[0093] <Negative electrode> In some embodiments, the negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector.

[0094] In some embodiments, the negative current collector is a metal foil or a composite current collector. In some embodiments, the metal foil is a copper foil. The composite current collector may include a metal foil substrate and a conductive layer disposed on at least one side of the metal foil substrate.

[0095] In some embodiments, the conductive layer may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, carbon fiber, carbon nanofiber, graphitized carbon sheet, carbon tube, carbon nanotube, activated carbon, and mesoporous carbon.

[0096] In some embodiments, the negative electrode active material may include natural graphite particles, synthetic graphite particles, hard carbon, soft carbon, mesophase carbon microspheres (MCMB), Sn, SnO2, SnO, Li4Ti5O 12The negative electrode active material is selected from at least one of LTO, Si material, silicon-carbon (Si-C) composite material, silicon-nitrogen (Si-N) composite material, and silicon-oxygen (Si-O) composite material. The negative electrode active material of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as negative electrode active materials for batteries.

[0097] In some embodiments, the negative electrode binder may include at least one of polyacrylic acid, polymethacrylic acid, polyacrylate, polymethacrylate, polyacrylamide, styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylic acid-acrylonitrile-acrylamide copolymer, acrylic acid-acrylonitrile-acrylate copolymer, acrylonitrile-butadiene rubber, nitrile rubber, acrylonitrile-styrene-butadiene copolymer, acryloyl rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polyepoxychloropropane, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, carboxymethyl chitosan, polyester, polyamide, polyether, polyimide, polycarboxylic acid ester, polycarboxylic acid, polyurethane, alginate, fluorinated polymer, chlorinated polymer, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropylene. The negative electrode binder of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as battery negative electrode binders.

[0098] In some embodiments, the negative electrode conductive agent may include at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanosheets, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon nanotubes, carbon nanotubes, activated carbon, and mesoporous carbon. The negative electrode conductive agent of this application is not limited to the above-mentioned materials, but also includes other materials that can be used as battery negative electrode conductive agents.

[0099] Electrolytes In some embodiments, the electrolyte may include at least one of a gel electrolyte, a solid electrolyte, and a liquid electrolyte.

[0100] In some embodiments, the liquid electrolyte may include a non-aqueous solvent and a lithium salt.

[0101] In some embodiments, the lithium salt may include at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and lithium difluoroborate.

[0102] In some embodiments, the non-aqueous solvent may be at least one of carbonate compounds, carboxylic acid ester compounds, and ether compounds.

[0103] In some embodiments, the carbonate compound may include at least one of chain carbonate compounds, cyclic carbonate compounds, and fluorocarbonate compounds.

[0104] In some embodiments, the chain carbonate compound may include diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and combinations thereof.

[0105] In some embodiments, the cyclic carbonate compound may include ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), vinyl ethylene carbonate (VEC), and combinations thereof.

[0106] In some embodiments, the fluorocarbonate compound may include at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, and trifluoromethylethylene carbonate.

[0107] In some embodiments, the carboxylic acid ester compound may include at least one of methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid lactone, valerate lactone, mevalonate lactone, caprolactone, and methyl formate.

[0108] In some embodiments, the ether compound may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.

[0109] In some embodiments, the non-aqueous solvent may also include at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters.

[0110] III. Electronic Devices This application provides an electronic device that includes any of the electrochemical devices described herein.

[0111] The electronic device described in this application is not particularly limited and may be any electronic device known in the prior art.

[0112] The application of the electrochemical device in this application is not particularly limited, and it can be used in any electronic device known in the prior art. According to some embodiments of this application, the electronic device includes, but is not limited to, mobile phones, smartphones, laptops, tablets, wearable devices, smartwatches, smart bracelets, smart glasses, power banks, televisions, game consoles, game controllers, digital cameras, smart speakers, headphones, keyboards, mice, monitors, drones, audio equipment, home appliances, toys, power tools, automobiles, motorcycles, electric bicycles, bicycles, robots, robot dogs, industrial robots, android robots, etc.

[0113] To clearly understand the technical solution of this application, the preparation of the diaphragm and electrochemical device is described below with examples and specific preparation methods. Those skilled in the art will understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0114] <Testing Methods> 1. Volume distribution and particle size test of melamine salts The separator was removed from the battery cell. The separator in the electrode area of ​​the battery cell was selected. Here, the separator adhesive layer was bonded to the electrode. A large area of ​​the adhesive layer coating was transferred to the electrode surface, leaving only the melamine salt coating. The separator was cleaned with N-methylpyrrolidone (NMP) to remove electrolyte and residual lithium salt. The melamine salt coating was collected using an electrostatic brush and dried. The volume distribution particle sizes of the melamine salt were obtained by testing with a laser particle size analyzer (Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK) Dv10, Dv50 and Dv90.

[0115] 2. Density test of melamine salt The separator was removed from the battery cell. The separator was selected from the electrode area, where the adhesive layer adhered to the electrode. A large area of ​​the adhesive layer had transferred to the electrode surface, leaving only the melamine salt coating. The separator was cleaned with N-methylpyrrolidone (NMP) to remove electrolyte and residual lithium salt. The melamine salt coating was collected using an electrostatic brush and dried to obtain the melamine salt. Then, a true density meter was used with helium as the displacement medium. Based on Archimedes' principle, the true volume of the sample was calculated by measuring the volume of gas displaced from the sample. Combined with the sample mass, the density (g / cm³) was determined. 3 = Sample mass / Actual volume

[0116] 3. Specific surface area test of melamine salts The separator is removed from the battery cell. The separator in the electrode area of ​​the battery cell is selected, where the separator adhesive layer is bonded to the electrode. A large area of ​​the adhesive layer coating is transferred to the electrode surface, leaving only the melamine salt coating. The separator is cleaned with N-methylpyrrolidone (NMP) to remove electrolyte and residual lithium salt. The melamine salt coating is collected using an electrostatic brush and dried to obtain the melamine salt. The specific surface area of ​​the melamine salt is then determined by the gas adsorption BET method. For details, please refer to GB T19587-2017 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method".

[0117] 4. pH test of melamine salt The separator was removed from the battery cell. The separator in the electrode area of ​​the battery cell was selected, where the separator adhesive layer was bonded to the electrode. A large area of ​​the adhesive layer was transferred to the electrode surface, leaving only the melamine salt coating. The separator was cleaned with N-methylpyrrolidone (NMP) to remove electrolyte and residual lithium salt. The melamine salt coating was collected using an electrostatic brush and dried to obtain melamine salt. The melamine salt was then added to deionized water and mixed evenly to prepare a 1% (w / w) melamine salt suspension. The pH value of the melamine salt suspension was measured using a pH meter electrode.

[0118] 5. Coating surface density and surface density per unit thickness test Remove the separator from the battery cell. Select the separator in the electrode area of ​​the battery cell. Here, the separator adhesive layer is bonded to the electrode, and a large area of ​​the adhesive layer coating is transferred to the electrode surface, leaving only the melamine salt coating. Take a section of the separator with area S and clean it with N-methylpyrrolidone (NMP) to remove the electrolyte and residual lithium salt. Dry it and record the weight as M1. Measure the coating thickness as h. Clean the separator again with N-methylpyrrolidone (NMP) using ultrasound. Use an electrostatic brush to remove the melamine salt coating. Dry it and record the weight as M2. Areal density of coating (g / m³) 2 = (M1-M2) / S; Areal density per unit thickness of coating (g / (m²)) 2 ·μm))=(M1-M2) / (S×h).

[0119] 6. Average coating thickness test The diaphragm was longitudinally cut along its thickness direction using plasma and polished using argon ion polishing technology to obtain a flat cross-section. The cross-section was then observed using a scanning electron microscope, and the thickness of the coating was measured at five test points. The arithmetic mean was calculated to obtain the average thickness of the coating.

[0120] 7. Membrane air permeability test The air permeability of the diaphragm was measured using a Wang Yan-style air permeability tester EG01-55-1MR, and the average value of three test results was taken as the air permeability of the diaphragm.

[0121] 8. Diaphragm elongation test The TD elongation and MD elongation of the separator were measured according to the standard GB / T36363-2018 "Polyolefin Separator for Lithium Batteries", with a stretching rate of 200 mm / min.

[0122] 9. Tensile strength test of the diaphragm The TD tensile strength and MD tensile strength of the separator were measured according to the standard GB / T36363-2018 "Polyolefin Separators for Lithium Batteries", with a tensile rate of 200 mm / min.

[0123] 10. Thermal safety performance test Charge the battery at a constant current and constant voltage of 0.5C to 4.53V, with a cutoff current of 0.02C; let it rest for 5 minutes; place the pouch battery in an oven (suspended test), and heat it using convection or circulating hot air at an initial temperature of 25±3℃. Increase the oven temperature at 5±2℃ / min to 12X±2℃ (X=0, 1, 2, 3….), and maintain this temperature for 60 minutes before stopping. During the test, monitor the pouch battery surface temperature, ambient temperature, and voltage. After resting for 1 hour, measure OCV and IMP. The oven temperature is initially set at 120℃. If the battery passes 120℃, the temperature is increased by 1℃ until the test fails. The maximum heat resistance temperature of the calibrated cell is the temperature one stage before the failure temperature (3 cells are tested in each temperature test group; if all cells pass, the test is considered successful).

[0124] 11. Loop Testing First, place the soft-pack battery in a 45℃ incubator for 2 hours to allow it to heat up evenly. Then, charge it at a constant current of 2.5C to 4.53V, switch to constant voltage charging until the current drops to 0.05C, then stop the charging. Let it stand for 10 minutes. Then, discharge it at a constant current of 0.7C to 3.0V, then stop the discharge. Let it stand for 10 minutes and record the discharge capacity of the first cycle. Then, perform 400 charge and discharge cycles and record the discharge capacity of the 400th cycle.

[0125] Cycle capacity retention rate = (discharge capacity of the 400th cycle / discharge capacity of the first cycle) × 100%; the test samples were set as 5 parallel samples, and the final test results were calculated as the average of the 5 parallel samples.

[0126] Example 1 <Preparation of the diaphragm> Melamine salt, ammonium polyacrylate salt (purchased from BASF), sodium carboxymethyl cellulose thickener, and a portion of deionized water were mixed evenly to obtain a melamine salt dispersion. Polyacrylic acid binder (purchased from Gaorui Materials) and the remaining deionized water were added to the melamine salt dispersion and stirred to obtain a coating slurry. The mass ratio of melamine salt, ammonium polyacrylate salt, sodium carboxymethyl cellulose thickener, polyacrylic acid binder, and deionized water in the coating slurry was 924:1:5:70:4000. A coating slurry is applied to one side of a porous substrate (polyethylene film), and after drying, a single-sided coated diaphragm is obtained. The above steps are repeated on the other side of the porous substrate within the single-sided coated diaphragm to obtain a double-sided coated diaphragm. SEM images of the coated surfaces are shown below. Figure 1 As shown.

[0127] <Preparation of the negative electrode> The negative electrode active material (artificial graphite), conductive agent (Super P), binder (styrene-butadiene rubber), and thickener (sodium carboxymethyl cellulose) were thoroughly mixed in a deionized water solvent system at a mass ratio of 98:0.5:1:0.5 to obtain a negative electrode slurry. The negative electrode slurry was coated onto the negative electrode current collector copper foil, dried, cold-pressed, slit, dried under vacuum at 85°C for 6 hours, and then the tabs were welded to obtain the negative electrode.

[0128] <Preparation of the positive electrode> The positive electrode active material (lithium cobalt oxide), conductive agent (Super P), and binder (polyvinylidene fluoride) were thoroughly mixed in N-methylpyrrolidone solvent at a mass ratio of 96:2:2 to obtain a positive electrode slurry. The positive electrode slurry was coated onto a current collector aluminum foil, dried at 85°C, and then cold-pressed. After trimming and slitting, it was dried under vacuum at 85°C for 6 hours and then the tabs were welded to obtain the positive electrode.

[0129] <Preparation of Electrolyte> An electrolyte was prepared by mixing lithium salt (LiPF6) with a non-aqueous organic solvent at a mass ratio of 8:92. The non-aqueous organic solvent consisted of ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propyl propionate (PP), and ethylene carbonate (VC) at a mass ratio of 20:30:20:28:2.

[0130] <Battery Manufacturing> The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide insulation. The electrode assembly is then wound up. After welding the tabs, the electrode assembly is placed in an aluminum-plastic film packaging bag, dried at 80°C, and then injected with electrolyte. Following vacuum sealing, settling, formation, shaping, and capacity testing, a soft-pack battery is obtained.

[0131] Examples 2 to 3 Except for the volume distribution particle sizes Dv10, Dv50, and Dv90 of melamine salt in the <Preparation of the Separator>, which are different from those in Example 1, the rest are the same as in Example 1.

[0132] Examples 4 to 5 Except for the density of the melamine salt in the <Preparation of the Separator>, which is different from that in Example 1, the rest is the same as in Example 1.

[0133] Examples 6 to 7 Except for the specific surface area of ​​melamine salt in the <Preparation of the diaphragm>, which is different from that in Example 1, the rest is the same as in Example 1.

[0134] Examples 8 to 9 Except for the difference in the average coating thickness in the <Separator Preparation> section compared to Example 1, the rest is the same as in Example 1. The average coating thickness is mainly adjusted by controlling the concentration of the coating slurry.

[0135] Examples 10 to 11 Except for the difference in the areal density of the coating in the <Preparation of the Separator> section compared to Example 1, the rest is the same as in Example 1. The areal density of the coating is mainly adjusted by improving the dispersibility of the coating slurry and controlling the particle size of the melamine salt particles.

[0136] Examples 12 to 13 Except for the type of melamine salt used in the <Preparation of the Separator>, which is different from that in Example 1, the rest is the same as in Example 1.

[0137] Comparative Examples 1 to 2 Except for the volume distribution particle sizes Dv10, Dv50, and Dv90 of melamine salt in the <Preparation of the Separator>, which are different from those in Example 1, the rest are the same as in Example 1.

[0138] Table 1 Table 2 Table 3 According to the data in Tables 1, 2, and 3, the air permeability of the separators in Examples 1 to 13 ranges from 156 sec / 100cc to 231 sec / 100cc; the TD elongation is greater than or equal to 41%; the MD elongation is greater than or equal to 33%; the TD tensile strength is greater than or equal to 2160 MPa; and the MD tensile strength is greater than or equal to 2689 MPa. The maximum temperature reached by the hot box of the pouch batteries in Examples 1 to 13 is greater than or equal to 128°C, and the capacity retention after 400 cycles at 45°C is greater than 86.1%, indicating that the separator of this application can improve the battery's high-temperature cycling performance while enhancing its thermal safety performance. Meanwhile, according to Comparative Examples 1 and 2, when the ratio of the melamine salt volume distribution particle size Dv90 to Dv10 in the separator coating is too small or too large, it is difficult to effectively improve the high-temperature cycling performance while maintaining the battery's thermal safety performance.

[0139] When the term "embodiment" is mentioned in the specification, it means that there is at least one embodiment in this application that includes the specific feature, structure, material, or characteristic. Therefore, expressions such as "in some embodiments," "in some embodiments," and "exemplary" used throughout the document do not necessarily refer to the same embodiment. Furthermore, the specific feature, structure, material, or characteristic may be combined in any suitable manner in one or more embodiments.

[0140] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A diaphragm, characterized in that A porous substrate and a coating layer on at least one surface of the porous substrate, the coating layer comprising melamine salt; The melamine salt is in a spherical or irregular particle shape; the volume distribution particle size Dv10 of the melamine salt is a μm, Dv90 is c μm, and satisfies: 3.0≤c / a≤13.

0.

2. The separator of claim 1, wherein The melamine salt satisfies at least one of the following conditions: (1) 0.1 μm≤Dv10≤0.8 μm; (2) 1.0 μm≤Dv90≤2.8 μm; (3) density of 1.0 g / cm 3 to 3.0 g / cm 3 ; (4) a specific surface area of 4.0 m 2 / g to 12.0 m 2 / g; (5) the pH value is 7.0 to 8.0; (6) the melamine salt comprises at least one of melamine cyanurate, melamine polyphosphate, melamine trithiocyanate, melamine hydrogen fluoride, melamine phosphate, melamine pyrophosphate, melamine borate, melamine phthalate, and melamine oxalate.

3. The septum of claim 1 wherein, The volume distribution particle size Dv50 of the melamine salt is b μm, and satisfies: 1.0≤(c-a) / b≤11.

5.

4. The septum of claim 3, wherein The volume distribution particle size Dv50 of the melamine salt satisfies: 0.2 μm≤Dv50≤2.0 μm.

5. The septum of claim 1 wherein, The unit thickness area density of the coating is d g / (m 2 ·μm) and satisfies: 0.5≤c / d≤5.

0.

6. The septum of claim 5, wherein The unit thickness area density of the coating is 0.2 g / (m 2 ·μm) to 1.2 g / (m 2 ·μm).

7. The separator according to any one of claims 1 to 6, wherein The coating layer satisfies at least one of the following conditions: (1) the average thickness of the coating layer is 1.2 μm to 2.8 μm; (2) the areal density of the coating is 1.0 g / m 2 to 3.0 g / m 2 ; (3) the mass ratio of the melamine salt is 80% to 99% based on the total mass of the coating layer.

8. The separator according to any one of claims 1 to 6, wherein The separator or the porous substrate satisfies at least one of the following conditions: (1) the air permeability of the separator is 50 sec / 100cc to 300 sec / 100cc; (2) the elongation of the separator in the transverse direction thereof is 40% to 100%; (3) the elongation of the separator in the longitudinal direction thereof is 30% to 150%; (4) the tensile strength of the separator in the transverse direction thereof is 1000 MPa to 4000 MPa; (5) the tensile strength of the separator in the longitudinal direction thereof is 1000 MPa to 4000 MPa; (6) the melting point of the porous substrate is 130℃ to 170℃; (7) the thickness of the porous substrate is 3 μm to 12 μm; (8) the porosity of the porous substrate is 30% to 70%.

9. An electrochemical device, characterized by, The separator of any one of claims 1 to 8.

10. An electronic device, comprising: The electrochemical device of claim 9.

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