Separators, electrochemical devices including the same, and electronic devices

Abstract

The application 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 substrate and a porous coating on at least one side surface of the porous substrate, and the porous coating comprises fibrous fillers; the fibrous fillers comprise a core layer and a shell layer on the surface of the core layer, the core layer comprises at least one of Mxene and an oxide thereof, MOFs and an oxide thereof, black phosphorus and an oxide thereof, and carbon; the shell layer comprises at least one of silicon dioxide and a lithiumophilic metal oxide; the mass ratio of the shell layer to the core layer of the fibrous fillers is M; the thermal conductivity of the diaphragm is lambda W / (m.K), the specific heat capacity is Cp J / (g.K), and the density is rho g / cm 3 ; the following relationships are satisfied: 0.010 <= (M*lambda) / (2Cp) <= 0.017 and 0.4 <= lambda / (rho*Cp) <= 1.0. The diaphragm can improve the safety performance, cycle life and rate performance of a battery.

Description

Technical Field

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

[0002] Traditional commercial lithium-ion battery separators are primarily polyolefin membranes, but they suffer from poor thermal stability, poor electrolyte wettability, and low puncture resistance. During charge-discharge cycles, they are easily punctured by lithium dendrites or prone to thermal shrinkage and deformation at high temperatures, leading to internal short circuits and severely impacting battery safety. Currently, the main approach is to modify the polyolefin membrane by coating it with inorganic ceramic materials to improve its thermal stability and safety. However, ceramic coatings suffer from problems such as particle shedding, decreased ionic conductivity due to high addition levels, and insufficient dendrite suppression, resulting in limited improvement in battery safety, cycle life, and rate performance. 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 porous coating located on at least one surface of the porous substrate, the porous coating comprising fibrous filler. The fibrous filler includes a core layer and a shell layer located on the surface of the core layer; The core layer comprises at least one of MXene and its oxides, MOFs and their oxides, black phosphorus and its oxides, and carbon; the shell layer comprises at least one of silicon dioxide and lithium-loving metal oxides. The mass ratio of the shell to the core of the fibrous filler is M; The diaphragm has a thermal conductivity of λW / (m·K), a specific heat capacity of CpJ / (g·K), and a density of ρg / cm³. 3 ; The following relationships are satisfied: 0.010≤(M×λ) / (2Cp)≤0.017 and 0.4≤λ / (ρ×Cp)≤1.0.

[0005] In some embodiments of this application, the diaphragm satisfies at least one of the following conditions: (1) Based on the diameter of the fibrous filler, the average thickness of the shell layer accounts for 15% to 30%; (2) Based on the total mass of the porous coating, the mass percentage of the fibrous filler is 20% to 30%; (3) The average thickness of the single-layer porous coating is 0.5 μm to 3.0 μm.

[0006] In some embodiments of this application, the diaphragm satisfies at least one of the following conditions: (1) 3.0% ≤ M ≤ 6.0%; (2)1.5W / (m·K)≤λ≤2.0W / (m·K); (3)2.0J / (g·K)≤Cp≤3.5J / (g·K); (4) 0.3 g / cm 3 ≤ρ≤2.3g / cm 3 .

[0007] In some embodiments of this application, the fibrous filler satisfies at least one of the following conditions: (1) The aspect ratio of the fibrous packing is 20 to 100; (2) The average thickness of the core layer of the fibrous filler is 50 nm to 100 nm; (3) The average thickness of the shell of the fibrous filler is 10 nm to 30 nm.

[0008] In some embodiments of this application, at least a portion of the surface of the shell layer of the fibrous filler is provided with a polymer coating layer.

[0009] In some embodiments of this application, the average thickness of the polymer coating layer is 30 nm to 50 nm.

[0010] In some embodiments of this application, the porous coating further includes a ceramic material.

[0011] In some embodiments of this application, the volumetric particle size Dv50 of the ceramic material is 0.5 μm to 1.5 μm; and / or, based on the total mass of the porous coating, the mass percentage of the ceramic material is 40% 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 porous coating of the separator in this application includes a fibrous filler with a core-shell structure. The core and shell layers of the fibrous filler form a synergistic interface through chemical bonding and charge gradient. The core layer provides a high-speed lithium-ion channel, while the shell layer inhibits electron shuttle and uniformly distributes lithium-ion flow. The heterogeneous interface optimizes the ion transport path, simultaneously improving ionic conductivity and interface stability, and reducing polarization effects. By controlling (M×λ) / (2Cp), the transient heat during fast charging or short circuits is ensured to effectively prevent battery thermal runaway, while avoiding excessive filling of pores by high thermal conductivity materials, which could lead to a decrease in ionic conductivity or the risk of lithium dendrite formation, thus increasing the critical heat level for triggering thermal runaway. By controlling λ / (ρ×Cp), the heat transfer rate of the battery at high temperatures is made greater than the exothermic rate of side reactions, effectively blocking the chain exothermic reaction, while preventing the formation of a continuous thermal short-circuit network by the high thermal conductivity material in the core layer, suppressing battery self-discharge, and thus improving the battery's safety performance, cycle life, and rate performance. Detailed Implementation

[0015] 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.

[0016] <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.

[0017] The term "porous coating" refers to one or more layers of material coated on one or both sides of a porous substrate. A porous coating includes at least one fibrous filler. In addition to fibrous fillers, a porous coating may also include one or more additives. A porous coating can be a single-layer, double-layer, or multi-layer structure.

[0018] The term "fibrous filler" refers to a linear material with a certain aspect ratio (length is greater than diameter).

[0019] The term "MXene" refers to a class of transition metal carbides, transition metal nitrides, or transition metal carbonitrides with a two-dimensional layered structure. These are novel materials with a structure similar to graphene, obtained by processing the MAX phase.

[0020] The term "MOFs" refers to metal-organic frameworks, which are crystalline porous materials with a periodic network structure formed by the self-assembly of inorganic metal centers (metal ions or metal clusters) and bridging organic ligands.

[0021] The term "lithophile metal oxide" refers to a class of metal oxides whose surfaces have a good affinity for lithium metal, enabling them to guide the uniform deposition / deintercalation of lithium ions and inhibit the growth of lithium dendrites. They typically possess high lithium-ion conductivity or have specific adsorption properties for lithium ions.

[0022] 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.

[0023] In the following description, all figures disclosed in this application are approximations.

[0024] 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.

[0025] I. Diaphragm This application provides a diaphragm comprising a porous substrate and a porous coating located on at least one side surface of the porous substrate, the porous coating comprising fibrous filler; The fibrous filler includes a core layer and a shell layer located on the surface of the core layer; The core layer contains at least one of MXene and its oxides, MOFs and their oxides, black phosphorus and its oxides, and carbon; the shell layer contains at least one of silicon dioxide (SiO2) and lithium-loving metal oxides. The mass ratio of the shell to the core of the fibrous packing is M; The diaphragm has a thermal conductivity of λW / (m·K), a specific heat capacity of CpJ / (g·K), and a density of ρg / cm³. 3 ; The following relationships are satisfied: 0.010≤(M×λ) / (2Cp)≤0.017 and 0.4≤λ / (ρ×Cp)≤1.0.

[0026] The porous coating of the separator in this application includes a fibrous filler with a core-shell structure. The core and shell layers of the fibrous filler form a synergistic interface through chemical bonding and charge gradient. The core layer provides a high-speed lithium-ion channel, while the shell layer inhibits electron shuttle and uniformly distributes lithium-ion flow. The heterogeneous interface optimizes the ion transport path, simultaneously improving ionic conductivity and interface stability, and reducing polarization effects. By controlling (M×λ) / (2Cp), the transient heat during fast charging or short circuits is ensured to effectively prevent battery thermal runaway, while avoiding excessive filling of pores by high thermal conductivity materials, which could lead to a decrease in ionic conductivity or the risk of lithium dendrite formation, thus increasing the critical heat level for triggering thermal runaway. By controlling λ / (ρ×Cp), the heat transfer rate of the battery at high temperatures is made greater than the exothermic rate of side reactions, effectively blocking the chain exothermic reaction, while preventing the formation of a continuous thermal short-circuit network by the high thermal conductivity material in the core layer, suppressing battery self-discharge, and thus significantly improving the battery's safety performance, cycle life, and rate performance.

[0027] When the calculated value of (M×λ) / (2Cp) is too small, the local temperature rise rate of the separator will be too fast, which will shorten the thermal runaway trigger time. When (M×λ) / (2Cp) is too large, it may lead to a decrease in the wettability of the electrolyte to the separator, which may induce lithium dendrite growth, thereby degrading the safety and cycle performance of the battery.

[0028] When the calculated value of λ / (ρ×Cp) is too small, heat diffuses slowly inside the separator, easily accumulates, forms local hot spots, and eventually leads to thermal runaway. When the calculated value of λ / (ρ×Cp) is too large, the ionic conductivity and porosity of the separator decrease, which will block the ion transport channels, affect the electrolyte retention, significantly increase the interfacial impedance and bulk impedance, and lead to a decrease in battery rate performance and an increase in polarization voltage.

[0029] "Porous coating located on at least one surface of a porous substrate" means that the porous 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.

[0030] In some implementations, some non-limiting examples of MXene include Ti3C2T. x Ti2CT x Nb2CT x Mo2CT x Ti4N3T x Ta4C3T x Cr2TiC2T x V2CT x Zr3C2T x 、(Nb 0.8 Zr 0.2 )4C3T x At least one of them.

[0031] In some implementations, some non-limiting examples of MOFs include at least one of ZIFs (zeolite imidazole ester framework materials), the UiO series (zirconium-based MOFs), the MIL series, and the HKUST series (copper-based MOFs).

[0032] In some embodiments, non-limiting examples of lithium-loving metal oxides include at least one of aluminum oxide (Al2O3), titanium oxide (TiO2), zinc oxide (ZnO), zirconium oxide (ZrO2), magnesium oxide (MgO), and hafnium oxide (HfO2).

[0033] In some implementations, the calculated value of (M×λ) / (2Cp) may be, but is not limited to, 0.010, 0.011, 0.012, 0.013, 0.014, 0.015, 0.016 or 0.017, or fall within the range of any two of the above values.

[0034] In some implementations, the calculated value of λ / (ρ×Cp) may be, but is not limited to, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0, or fall within the range of any two of the above values.

[0035] In some embodiments, the thermal conductivity (λ) of the separator is from 1.5 W / (m·K) to 2.0 W / (m·K), for example, but not limited to 1.5 W / (m·K), 1.6 W / (m·K), 1.7 W / (m·K), 1.8 W / (m·K), 1.9 W / (m·K), or 2.0 W / (m·K), or falls within any two of the above values. A thermal conductivity within this range not only facilitates rapid dissipation of localized heat during fast charging or short circuits to reduce the risk of thermal runaway, but also maintains high ionic conductivity, enabling the battery to exhibit good cycle performance.

[0036] In some embodiments, the specific heat capacity (Cp) of the diaphragm is from 2.0 J / (g·K) to 3.5 J / (g·K), for example, but not limited to 2.0 J / (g·K), 2.1 J / (g·K), 2.2 J / (g·K), 2.3 J / (g·K), 2.4 J / (g·K), 2.5 J / (g·K), 2.6 J / (g·K), 2.7 J / (g·K), 2.8 J / (g·K), 2.9 J / (g·K), 3 J / (g·K), 3.1 J / (g·K), 3.2 J / (g·K), 3.3 J / (g·K), 3.4 J / (g·K), or 3.5 J / (g·K), or falls within the range of any two of the above values. When the specific heat capacity of the separator is within the above range, it can not only absorb more heat to delay the temperature rise and improve thermal safety, but also avoid causing thermal effect lag and affecting the transient thermal management of the battery.

[0037] In some embodiments, the density (ρ) of the diaphragm is 0.3 g / cm³. 3 Up to 2.3 g / cm 3 For example, it can be, but is not limited to, 0.3 g / cm³. 3 0.4g / cm 3 0.5g / cm 3 0.6g / cm 3 0.7g / cm 3 0.8g / cm 3 0.9g / cm 3 1.0g / cm 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 Or 2.3g / cm 3 The density of the membrane should be within the range of either of the two values ​​mentioned above, or within the range of any two values ​​above. A membrane density within this range better balances mechanical strength and pore structure, thereby better ensuring electrolyte wetting and ion transport.

[0038] <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.

[0039] 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.

[0040] 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.

[0041] In some embodiments, the melting point of the porous substrate is between 130°C and 160°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, or 160°C, or within 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.

[0042] In some embodiments, the thickness of the porous substrate is from 2 μm to 16 μm, for example, but not limited to 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or 16 μm, or within any two of the above values. A porous substrate thickness within the above range not only allows the separator to possess higher puncture strength to better suppress lithium dendrites, but also maintains lower internal resistance and higher energy density.

[0043] In some embodiments, the porosity of the porous substrate is 20% to 60%, for example, but not limited to 20%, 23%, 25%, 28%, 30%, 32%, 35%, 37%, 40%, 43%, 45%, 48%, 50%, 52%, 55%, 58%, or 60%, or within any two of the above values. A porosity within the above 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; it also allows the membrane to possess higher mechanical strength, thereby reducing the risk of lithium dendrite penetration.

[0044] In some embodiments, the air permeability of the porous substrate is from 30 sec / 100cc to 400 sec / 100cc, for example, but not limited to 30 sec / 100cc, 50 sec / 100cc, 80 sec / 100cc, 100 sec / 100cc, 130 sec / 100cc, 150 sec / 100cc, 170 sec / 100cc, 200 sec / 100cc, 230 sec / 100cc, 250 sec / 100cc, 280 sec / 100cc, 300 sec / 100cc, 330 sec / 100cc, 350 sec / 100cc, 370 sec / 100cc or 400 sec / 100cc, or within the range of any two of the above values. When the permeability of the porous substrate is within the above range, it can not only better ensure the transport of lithium ions in the separator and the timely discharge of gases generated during charging and discharging, but also effectively reduce the risk of the separator being penetrated by lithium dendrites.

[0045] <Porous Coating> In some embodiments, the average thickness of the single-layer porous coating (i.e., the average thickness of the porous coating on one side surface of the porous substrate) is from 0.5 μm to 3.0 μm, and may include, but is not limited to, 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, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, or 3.0 μm, or falls within the range of any two of the above values. The average thickness of a single-layer porous coating within the above range can better balance the overall thermal conductivity, mechanical strength and ion transport of the separator; a thinner average thickness may lead to insufficient thermal management or uneven coating, while a thicker average thickness will increase internal resistance and battery volume.

[0046] <Fibrous packing> In some embodiments, the mass ratio (M) of the shell to core layer of the fibrous filler is 3.0% to 6.0%, for example, it may include, but is not limited to, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%, 5.1%, 5.2%, 5.3%, 5.4%, 5.6%, 5.7%, 5.8%, 5.9%, or 6.0%, or falls within the range of any two of the above values. A mass ratio of the shell to core layer of the fibrous filler within the above range not only ensures efficient lithium-ion penetration but also contributes to maintaining a higher energy density in the battery.

[0047] In some embodiments, based on the diameter of the fibrous filler, the average thickness of the shell layer accounts for 15% to 30%, for example, it may include, but is not limited to, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%, or falls within any two of the above values. An average shell layer thickness within the above range in the fibrous filler not only effectively prevents electron tunneling to mitigate battery self-discharge and improve its coulombic efficiency, but also enhances the homogenization of lithium-ion flow to better suppress lithium dendrites; simultaneously, it avoids excessive electron blocking ability, better promotes lithium-ion migration, thereby reducing battery resistance and improving its rate performance; furthermore, it also helps to improve the overall thermal conductivity of the separator.

[0048] The average thickness percentage of the shell layer in fibrous fillers can be obtained by taking pictures of at least 50 randomly selected fibrous fillers using a transmission electron microscope (TEM), then using image analysis software to measure the diameter of the fibrous filler and the diameter of its core layer to obtain the shell thickness percentage, and calculating the average of all measured values ​​to obtain the average shell thickness percentage.

[0049] In some embodiments, the mass percentage of fibrous filler in the porous coating is 20% to 30% based on the total mass of the porous coating. For example, it can be, but is not limited to, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%, or falls within any two of the above values. A mass percentage of fibrous filler in the porous coating within the above range not only enables the formation of a continuous three-dimensional network structure in the porous coating to better enhance thermal conductivity and ion transport, but also allows the membrane to maintain a high porosity to promote increased electrolyte retention, thereby further improving ionic conductivity.

[0050] In some embodiments, the aspect ratio (i.e., the ratio of length to diameter) of the fibrous filler is between 20 and 100, for example, but not limited to 20, 23, 25, 27, 30, 33, 35, 38, 40, 43, 45, 47, 50, 53, 55, 58, 60, 63, 65, 68, 70, 73, 75, 77, 80, 83, 85, 88, 90, 93, 95, 98, or 100, or falls within any two of the above values. An aspect ratio within the above range not only facilitates the formation of a three-dimensional network structure in the porous coating, but also effectively prevents entanglement between the fibrous fillers, thus avoiding difficulties in dispersion in the slurry. This further improves the uniformity of the formed porous coating, thereby enhancing the thickness consistency of the diaphragm and effectively preventing the generation of local short-circuit points.

[0051] In some embodiments, the average thickness of the core layer of the fibrous filler is from 50 nm to 100 nm, for example, but not limited to 50 nm, 52 nm, 54 nm, 56 nm, 58 nm, 60 nm, 62 nm, 64 nm, 66 nm, 68 nm, 70 nm, 72 nm, 74 nm, 76 nm, 78 nm, 80 nm, 82 nm, 84 nm, 86 nm, 88 nm, 90 nm, 92 nm, 94 nm, 96 nm, 98 nm, or 100 nm, or within any two of the above values. An average thickness of the core layer of the fibrous filler within the above range not only provides an effective ion transport channel to better promote ion transport, but also allows the fibrous filler to maintain a certain degree of flexibility and is beneficial to improving the uniformity of the porous coating.

[0052] In some embodiments, the average thickness of the shell layer of the fibrous filler is from 10 nm to 30 nm, for example, it can be 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, or 30 nm, or within any two of the above values. An average shell thickness of the fibrous filler within the above range can effectively suppress electron shuttle while better uniformizing the lithium-ion flow.

[0053] <Polymer Coating> In some embodiments, at least a portion of the surface of the shell of the fibrous filler is provided with a polymer coating layer. Coating the surface of the shell of the fibrous filler with a polymer coating layer can effectively improve the tensile strength of the fibrous filler, which is more conducive to maintaining the structural integrity of the fibrous filler during battery assembly or cycling (i.e., reducing fiber breakage), thereby maintaining the structural stability of the three-dimensional network constructed by the fibrous filler, and thus better improving the cycle performance and safety performance of the battery.

[0054] In some embodiments, the polymeric coating layer includes, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyacrylic acid (PAA), polyimide (PI), sodium carboxymethyl cellulose (CMC), and sodium alginate (SA).

[0055] In some embodiments, the average thickness of the polymer coating is 30 nm to 50 nm, for example, but not limited to 30 nm, 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, 40 nm, 41 nm, 42 nm, 43 nm, 44 nm, 46 nm, 47 nm, 48 nm, 49 nm, or 50 nm, or within any two of the above values. An average thickness of the polymer coating within the above range can not only effectively improve the structural stability of the three-dimensional network constructed by the fibrous filler in the porous coating to better enhance thermal conductivity and ion transport, but also prevent clogging of the pores between the fibrous fillers, thus maintaining a high porosity in the porous coating, better promoting ion transport, reducing battery internal resistance, and improving battery rate performance; it can also prevent the polymer coating from melting at high temperatures and clogging the pores, reducing safety risks.

[0056] <Ceramic Materials> In some embodiments, the porous coating also includes ceramic materials.

[0057] In some embodiments, the ceramic material may include at least one of alumina (Al2O3), silicon oxide (SiO2), titanium oxide (TiO2), zirconium oxide (ZrO2), magnesium oxide (MgO), zinc oxide (ZnO), boron nitride (BN), and aluminum nitride (AlN).

[0058] This application does not impose any particular limitation on the shape of the ceramic material, as long as it can achieve the purpose of this application. The ceramic material can be spherical, rod-shaped, plate-shaped, disc-shaped, needle-shaped, cylindrical, irregular, or other known particle shapes.

[0059] In some embodiments, the ceramic material is not spherical, rod-shaped, plate-shaped, disc-shaped, needle-shaped, cylindrical, or irregular. Preferably, the ceramic material is spherical. Spherical particles have a higher packing density, which can form a continuous thermally conductive network, reducing the risk of local thermal runaway. Spherical particles have a small surface curvature, a low contact angle with the electrolyte, a higher liquid absorption rate, and better wettability.

[0060] In some embodiments, the volumetric particle size distribution Dv50 of the ceramic material is from 0.5 μm to 1.5 μm. For example, Dv50 can be, but is not limited to, 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, or 1.5 μm, or falls within any two of the above values. A volumetric particle size distribution Dv50 within the above range is not only more beneficial for improving the smoothness and uniformity of the porous coating to reduce the risk of battery short circuits, but also for its uniform dispersion in the porous coating and for maintaining a high porosity in the porous coating, thereby improving the ionic conductivity of the separator and enhancing the cycle performance of the battery.

[0061] In some embodiments, the ceramic material constitutes 40% to 70% of the total mass of the porous coating, for example, but not limited to 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, or 70%, or within any range of two of the aforementioned values. When the mass percentage of ceramic material in the porous coating is within the aforementioned range, it can better synergize with the fibrous filler, thereby achieving better anisotropic thermal conductivity and ion flow regulation, thus better improving the cycle performance and safety performance of the battery.

[0062] 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.

[0063] In some embodiments, the electrochemical device includes a positive electrode, a negative electrode, an electrolyte, and a membrane, the membrane being located between the positive and negative electrodes, and the membrane used in the electrochemical device is the membrane described above in this application.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] <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.

[0077] 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.

[0078] 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.

[0079] 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 the following: 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.

[0080] 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.

[0081] 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.

[0082] Electrolytes In some embodiments, the electrolyte may include at least one of a gel electrolyte, a solid electrolyte, and a liquid electrolyte.

[0083] In some embodiments, the liquid electrolyte may include a non-aqueous solvent and a lithium salt.

[0084] 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.

[0085] In some embodiments, the non-aqueous solvent may be at least one of carbonate compounds, carboxylic acid ester compounds, and ether compounds.

[0086] In some embodiments, the carbonate compound may include at least one of chain carbonate compounds, cyclic carbonate compounds, and fluorocarbonate compounds.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] III. Electronic Devices This application provides an electronic device that includes the electrochemical device described above.

[0094] The electronic device described in this application is not particularly limited and may be any electronic device known in the prior art.

[0095] 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.

[0096] 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.

[0097] <Testing Methods> 1. Thermal conductivity test of the diaphragm: The test was conducted using the laser flash method, referring to the standard ASTM E1461-11.

[0098] 2. Specific heat capacity test of the diaphragm: Differential scanning calorimetry (DSC) was used for the test, referring to the standard ASTM E1269-11.

[0099] 3. Diaphragm density test: It can be calculated by measuring the mass and geometric volume of the diaphragm. Specifically, it includes the following steps: S1. Take a diaphragm sample, cut it into a regular shape (rectangle), and measure its area (S) and thickness (h). The thickness needs to be measured at multiple points and the average value is taken. S2. Weigh the sample mass (m) using a precision balance, accurate to 0.1 mg; S3. Calculate the geometric volume: V = S × h; Calculate density: ρ = m / V (unit: g / cm³) 3 ); Repeat the test three times and take the average value to ensure the reliability of the results.

[0100] 4. Test of the mass ratio of shell to core in fibrous packing: determined by thermogravimetric analysis (TGA); the core will burn and lose weight in air atmosphere, while the shell remains stable. The mass ratio of shell to core can be calculated by the weight loss ratio.

[0101] 5. Cyclic Performance Test: The capacity-graded pouch cells were charged to 4.53V at a constant current and constant voltage of 2C in a 25℃ environment, with a cutoff current of 0.05C. Then, they were discharged to 3.0V at a constant current of 0.7C. This constitutes one cycle, which was repeated 500 times. After 500 cycles, the capacity retention rate and thickness expansion rate were calculated using the following formulas. Full charge refers to 100% SOC: Capacity retention rate = (500th cycle discharge capacity / 1st cycle discharge capacity) × 100%; Thickness expansion rate = (thickness at full charge in the 500th cycle - thickness at full charge in the 1st cycle) / thickness at full charge in the 1st cycle × 100%.

[0102] 6. Rate Performance Test: At 25℃, the soft-pack battery is charged at a constant current of 0.2C to 4.53V, then charged at a constant voltage to a current of 0.05C. After resting for 5 minutes, it is discharged at a constant current of 0.2C to 3V. The discharge capacity of this discharge is recorded as the 0.2C discharge capacity. After resting for 5 minutes, it is charged at a constant current of 0.2C to 4.53V, then charged at a constant voltage to a current of 0.05C. After resting for 5 minutes, it is discharged at a constant current of 0.5C to 3V. The discharge capacity of this discharge is recorded as the 0.5C discharge capacity retention rate = (0.5C discharge capacity / 0.2C discharge capacity) × 100%.

[0103] 7. Thermal runaway performance test: Under 25℃ ambient conditions, the pouch battery is discharged at a constant current density of 0.2C to the cutoff voltage of 2.8V; after resting for 5 minutes, it is charged at a constant current and constant voltage of 0.5C to 4.55V, with a cutoff current of 0.02C; the pouch battery is placed in an oven, and the oven temperature is increased to 130±2℃ at a rate of 5±2℃ / min and maintained for 60 minutes before stopping. During the test, the surface temperature of the pouch battery needs to be monitored and thermal runaway needs to be observed.

[0104] Example 1 <Preparation of the positive electrode> The positive electrode active material (lithium cobalt oxide), conductive agent (acetylene black), and binder (polyvinylidene fluoride (PVDF)) are thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 98:1.2:0.8 to obtain a positive electrode slurry. The positive electrode slurry is then coated onto an Al foil, and after drying, rolling, and slitting, the positive electrode is obtained.

[0105] <Preparation of the negative electrode> The negative electrode active material (graphite), conductive agent (acetylene black), binder (styrene-butadiene rubber (SBR)) and thickener (sodium carboxymethyl cellulose (CMC)) are thoroughly mixed in a deionized water solvent system at a mass ratio of 98.1:0.5:0.7:0.7 to obtain a negative electrode slurry. The negative electrode slurry is then coated onto Cu foil, and after drying, rolling, and slitting, the negative electrode is obtained.

[0106] <Preparation of the diaphragm> S1, 2.017g of MXene (Ti3C2T) x The solution was dispersed in 20 mL of solvent system (composed of DMF and anhydrous ethanol in a mass ratio of 7:3) to form a homogeneous suspension, and stirred for 30 min; then 8 g of PVP (polyvinylpyrrolidone) was added, and stirring was continued for 5 h to obtain the core layer precursor solution of fibrous filler. S2. Disperse 0.280 g of tetraethyl orthosilicate (TEOS) in 20 mL of solvent system (composed of DMF and anhydrous ethanol in a mass ratio of 7:3) and stir for 30 min; then add 6 g of PVP (polyvinylpyrrolidone) and continue stirring for 5 h to obtain the shell precursor solution of fibrous filler. S3. Inject the core precursor solution and the shell precursor solution into the coaxial spinning needle respectively, apply a voltage of 15kV, use a rotating drum receiver (rotation speed 300rpm), receive at a distance of 12cm, and advance at a speed of 1mm / s to obtain a fiber web material. S4. Place the fiber web material in a tube furnace and perform step calcination under an argon atmosphere; First stage: Increase the temperature to 350℃ at a rate of 2℃ / min and hold for 1 hour; Second stage: Increase the temperature to 600℃ at a rate of 1℃ / min and hold for 4 hours; Then, the temperature is reduced to below 80°C at a rate of 1°C / min, and the calcined fiber web is obtained. S5. Immerse the calcined fiber web in a 5 wt% PVDF / NMP solution for 10 seconds, then remove and dry at 80°C for 10 minutes to obtain the composite fiber material. S6. The above-mentioned composite fiber material, ceramic material (composed of alumina and zirconium oxide in a mass ratio of 7:3, Dv50 = 0.7μm), binder (polyvinylidene fluoride PVDF) and dispersant (polyvinylpyrrolidone PVP) are added to the organic solvent N-methylpyrrolidone (NMP) in a certain mass ratio (ceramic material: composite fiber material: binder: dispersant = 70:25:4:1). The mixture is thoroughly stirred and dispersed using a ball mill until all components are evenly mixed to form a slurry with stable viscosity and good dispersion. The resulting slurry is uniformly coated on both sides of a porous substrate (PE membrane). After drying, a firm and porous coating is formed to obtain a diaphragm.

[0107] The average thickness of the porous coating in the diaphragm was measured to be 1.0 μm. The mass percentage of the fibrous filler in the porous coating was 25%, and the mass percentage of the ceramic material was 73%. The average length of the fibrous filler was 4300 μm, and the average thickness of the core layer of the fibrous filler was 75 nm, while the average thickness of the shell layer was 20 nm.

[0108] <Preparation of Electrolyte> The lithium salt (LiPF6) and a non-aqueous organic solvent were prepared in a mass ratio of 8:92; wherein the non-aqueous organic solvent was composed of ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propyl propionate (PP), and ethylene carbonate (VC) in a mass ratio of 25:25:15:31:4.

[0109] <Preparation of Pouch Cells> The obtained positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes, and wound to obtain a bare cell. The bare cell is then placed in an aluminum-plastic film outer packaging for sealing, and then baked in an 85°C vacuum oven for 48 hours. The obtained electrolyte is injected into the dried battery, which is then sealed, allowed to stand, formed, shaped, and capacity tested, and then resealed to obtain a soft-pack battery.

[0110] Examples 2 to 4 Except for the mass ratio of the shell to the core in the fibrous filler in the <Preparation of the diaphragm> section, as well as the thermal conductivity, specific heat capacity, and density of the diaphragm, which differ from those in Example 1, the rest are the same as in Example 1.

[0111] The thermal conductivity, specific heat capacity, and density of the diaphragm are mainly adjusted by controlling the mass ratio of fibrous filler and ceramic material in the porous coating.

[0112] Example 5 Except for replacing MXene with MOFs (Cu3(HHTP)2) in step S1 of <Preparation of the diaphragm> and replacing tetrabutyl titanate with tetrabutyl titanate in step S2, the rest is the same as in Example 1.

[0113] Example 6 Except for replacing MXene with two-dimensional black phosphorus in step S1 of <Preparation of the diaphragm> and replacing tetraethyl orthosilicate with zinc chloride trihydrate in step S2, the rest is the same as in Example 1.

[0114] Example 7 Except for replacing MXene with sodium alginate in step S1 of <Preparation of the diaphragm> and replacing tetraethyl orthosilicate with magnesium chloride hexahydrate in step S2, the rest is the same as in Example 1.

[0115] Comparative Example 1 Except for step S3 of <Separator Preparation>, in which only the shell precursor solution is injected into the coaxial spinning needle, the rest is the same as in Example 1.

[0116] Comparative Example 2 Except for step S3 of the <Preparation of the diaphragm>, in which only the core layer precursor solution is injected into the coaxial spinning needle, the rest is the same as in Example 1.

[0117] Comparative Examples 3 to 5 Except for the thermal conductivity, specific heat capacity, and density of the diaphragm in the <Preparation of Diaphragm> section, which differ from those in Example 1, the rest are the same as in Example 1.

[0118] The thermal conductivity, specific heat capacity, and density of the diaphragm are mainly adjusted by controlling the mass ratio of fibrous filler and ceramic material in the porous coating.

[0119] Table 1 In Table 1, " / " indicates that no relevant parameters are provided. The units for thermal conductivity λ are W / (m·K), specific heat capacity Cp is J / (g·K), and density ρ is g / cm³. 3 .

[0120] Table 2 According to the data in Table 2, the capacity retention rate of the soft-pack batteries in Examples 1 to 7 after 500 cycles is ≥88% and the thickness expansion rate is ≤8.5%. At the same time, the capacity retention rate at 0.5C discharge is ≥96.5%, and the time for thermal runaway at 130°C is ≥42 minutes. This shows that the separator of this application can improve the safety performance, cycle life and rate performance of the battery.

[0121] Comparative Examples 1 and 2 show that when the fibrous filler in the porous coating of the separator only has a core layer or a shell layer, it is difficult to effectively improve the safety performance, cycle life and rate performance of the battery. Comparative Examples 3 to 5 also show that when (M×λ) / (2Cp) is too large, or when λ / (ρ×Cp) is too large or too small, the safety performance, cycle life and rate performance of the battery will be degraded.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A diaphragm comprising a porous substrate and a porous coating located on at least one surface of the porous substrate, characterized in that, The porous coating includes fibrous fillers; The fibrous filler includes a core layer and a shell layer located on the surface of the core layer; The core layer comprises at least one of MXene and its oxides, MOFs and their oxides, black phosphorus and its oxides, and carbon; the shell layer comprises at least one of silicon dioxide and lithium-loving metal oxides. The mass ratio of the shell to the core of the fibrous filler is M; The diaphragm has a thermal conductivity of λ W / (m·K), a specific heat capacity of Cp J / (g·K), and a density of ρ g / cm³. 3 ; It satisfies the following relationships: 0.010≤(M×λ) / (2Cp)≤0.017 and 0.4≤λ / (ρ×Cp)≤1.0; The diaphragm satisfies the following conditions: （1）3.0%≤M≤6.0%； (2)1.5W / (m·K)≤λ≤2.0W / (m·K); (3) 2.0J / (g·K)≤Cp≤3.5J / (g·K); (4)0.3g / cm 3 ≤ρ≤2.3g / cm 3 。 2. The diaphragm as described in claim 1, characterized in that, The diaphragm satisfies at least one of the following conditions: (1) Based on the diameter of the fibrous filler, the average thickness of the shell layer accounts for 15% to 30%; (2) Based on the total mass of the porous coating, the fibrous filler accounts for 20% to 30% of the mass; (3) The average thickness of the single-layer porous coating is 0.5 μm to 3.0 μm.

3. The diaphragm as described in claim 1, characterized in that, The fibrous filler satisfies at least one of the following conditions: (1) The aspect ratio of the fibrous packing is 20 to 100; (2) The average thickness of the core layer of the fibrous filler is 50 nm to 100 nm; (3) The average thickness of the shell of the fibrous filler is 10 nm to 30 nm.

4. The diaphragm as described in claim 1, characterized in that, At least a portion of the surface of the shell layer of the fibrous filler is provided with a polymer coating layer.

5. The diaphragm as described in claim 4, characterized in that, The average thickness of the polymer coating layer is 30 nm to 50 nm.

6. The diaphragm as described in claim 1, characterized in that, The porous coating also includes ceramic materials.

7. The diaphragm as described in claim 6, characterized in that, The volumetric particle size distribution Dv50 of the ceramic material is 0.5 μm to 1.5 μm; And / or, based on the total mass of the porous coating, the ceramic material accounts for 40% to 70% of the mass.

8. An electrochemical device, characterized in that, Includes the diaphragm as described in any one of claims 1 to 7.

9. An electronic device, characterized in that, Includes the electrochemical device as described in claim 8.

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