Diaphragm and device comprising same

Abstract

The invention relates to a diaphragm and a device comprising the same. Specifically, the diaphragm provided by the invention comprises a porous base material and a porous coating, the porous coating is arranged on at least one surface of the porous base material, the porous coating comprises inorganic particles and a binder, the binder comprises a first binder, and the first binder comprises a metal element. The diaphragm provided by the invention has excellent thermal safety stability and mechanical stability, which are mainly shown as follows: a circle needle with the diameter of R and heated to 500 DEG C is used for carrying out thermal puncture on the diaphragm to obtain a rupture hole formed in the diaphragm, any two points on the edge of the rupture hole are connected, the distance between the two points is calculated, and the maximum value is r, 400 [mu] m < = R < = 1000 [mu] m and 0.9 < = r / R < = 5.

Description

[0001] This application is a divisional application of the invention patent titled "Separator and Device Comprising the Same" with application number 202280005580.6 (International Application Number: PCT / CN2022 / 088840), filed on April 24, 2022. Technical Field

[0002] This application relates to the field of energy storage technologies, and more particularly, to a separator and a device comprising the same. Background Art

[0003] Due to advantages such as high energy density, relatively simple reaction mechanism, high working voltage, long lifespan, and environmental friendliness, rechargeable secondary batteries are considered one of the most attractive energy storage systems. Nowadays, secondary batteries have been widely applied in various fields such as wearable devices, smartphones, drones, laptop computers, etc.

[0004] With the wide application of secondary batteries in various fields, people's demand for secondary batteries is getting higher and higher. However, when secondary batteries are used in some extreme environments (such as impact, nail penetration, and thermal box) or are used abnormally under other circumstances, the safety performance of the batteries is difficult to guarantee, and even battery explosions may occur. In view of this, it is urgent to improve the safety performance of secondary batteries. Summary of the Invention

[0005] To at least solve the above problems, this application improves the safety performance of an electrochemical device by improving the separator of the electrochemical device. Specifically, this application provides a separator with high safety performance, and the separator has excellent heat shrinkage performance, thermal puncture performance, and thermal box performance.

[0006] According to one aspect of this application, this application provides a separator, which includes: a porous substrate; and a porous coating disposed on at least one surface of the porous substrate, the porous coating including inorganic particles and a binder, the binder including a first binder, and the first binder including a metal element; wherein, a circular needle with a diameter of R and heated to 500 °C is used to perform a thermal puncture on the separator to obtain a rupture hole generated on the separator, any two points on the edge of the rupture hole are connected and the distance between the two points is calculated, and the maximum value is taken as r, and wherein, 400 μm ≤ R ≤ 1000 μm and 0.9 ≤ r / R ≤ 5.

[0007] According to an embodiment of this application, wherein, 400 μm ≤ r ≤ 1500 μm.

[0008] According to an embodiment of this application, wherein, the compressive strength of the binder is α MPa, and 0.5 ≤ α ≤ 10.

[0009] According to an embodiment of the present application, wherein the glass transition temperature of the binder is Tg, and 150°C ≤ Tg ≤ 300°C.

[0010] According to an embodiment of the present application, wherein the metal element includes at least one of metal elements with a valence of +1, +2, or +3.

[0011] According to an embodiment of the present application, wherein the metal element includes at least two of the metal elements with a valence of +1, +2, or +3.

[0012] According to an embodiment of the present application, wherein the first binder satisfies at least one of the following conditions (a) to (c): (a) the metal element with a valence of +1 includes at least one of Li or Na; (b) the metal element with a valence of +2 includes at least one of Ca or Mg; (c) the metal element with a valence of +3 includes Al.

[0013] According to an embodiment of the present application, wherein the binder satisfies at least one of the following conditions (d) to (e): (d) the molar content ratio of the metal element with a valence of +1 to the metal element with a valence of +2 is a, and 1 ≤ a ≤ 10; (e) the molar content ratio of the metal element with a valence of +1 to the metal element with a valence of +3 is b, and 1 ≤ b ≤ 50.

[0014] According to an embodiment of the present application, wherein the first binder includes at least one of a carboxyl group or a sulfonic acid group, and the pH value of the first binder is pH1, and 7 ≤ pH1 ≤ 11.

[0015] According to an embodiment of the present application, wherein the first binder includes at least one of the following: sodium polymethylcellulose, lithium polymethylcellulose, lithium polycarboxymethylcellulose, lithium polyhydroxypropylmethylcellulose, calcium polyacrylate, lithium polyacrylate, or calcium polymethacrylate.

[0016] According to an embodiment of the present application, wherein the binder further includes a second binder, and based on the total weight of the porous coating, the weight ratio of the first binder to the second binder is β, and 0.2 ≤ β ≤ 4.

[0017] According to an embodiment of the present application, wherein the second binder includes at least one of a carboxyl group or a sulfonic acid group, and the pH value of the second binder is pH2, and 3 ≤ pH2 ≤ 7.

[0018] According to an embodiment of the present application, wherein the second binder includes at least one of the following: butyl polyacrylate, ethyl polyacrylate, butyl polymethacrylate, polymethyl methacrylate, or styrene-butadiene rubber.

[0019] According to an embodiment of the present application, wherein the specific surface area of the inorganic particles is S BET m 2 / g, 2 ≤ S BET ≤ 10.

[0020] According to an embodiment of the present application, wherein the particle sizes Dv50 and Dv99 of the inorganic particles respectively satisfy 0.3 μm ≤ Dv50 ≤ 3 μm and Dv99 ≤ 4 μm.

[0021] According to an embodiment of the present application, wherein the inorganic particles include at least one of the following: aluminum oxide, boehmite, zirconia, boron nitride, silicon nitride, or aluminum nitride.

[0022] According to an embodiment of the present application, wherein the porous coating further includes a wetting agent. Based on the total weight of the porous coating, the content of the inorganic particles is m1 wt%, the content of the binder is m2 wt%, and the content of the wetting agent is m3 wt%, where 90 ≤ m1 ≤ 96, 3 ≤ m2 ≤ 9, 0.5 ≤ m3 ≤ 2, and m1 + m2 + m3 = 100.

[0023] According to an embodiment of the present application, wherein the wetting agent includes at least one of the following: polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene-polyoxypropylene block copolymer, or silicone.

[0024] According to an embodiment of the present application, wherein the separator is placed at 150 °C for 1 hour. Compared with the initial length and width of the separator, the thermal shrinkage rate of the separator in the length (MD) direction is L1, and the thermal shrinkage rate in the width (TD) direction is L2, where L1 < 10%, L2 < 10%, and 0.75 ≤ L1 / L2 ≤ 1.2.

[0025] According to an embodiment of the present application, wherein the thickness of the porous coating is T μm, 0.5 ≤ T ≤ 3.

[0026] According to an embodiment of the present application, wherein the adhesion of the porous coating is F N / m, 5 ≤ F ≤ 100.

[0027] According to another aspect of the present application, the present application further provides an electrochemical device, which includes the separator described in the above embodiments of the present application.

[0028] According to another aspect of the present application, the present application further provides an electronic device, which includes the electrochemical device described in the above embodiments of the present application. Description of the Drawings

[0029] The accompanying drawings necessary for describing the embodiments of the present application or the prior art will be briefly described below to facilitate the description of the embodiments of the present application. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those skilled in the art, without creative efforts, other embodiment drawings can still be obtained according to the structures illustrated in these drawings.

[0030] Figure 1 The charge-coupled device (CCD) image of the diaphragm described in the present application after thermal puncture with a round needle having a diameter of R and heated to 500 °C is shown.

[0031] Figure 2 The CCD image of the diaphragm in the prior art after thermal puncture with a round needle having a diameter of R and heated to 500 °C is shown. Detailed Embodiments

[0032] The embodiments of the present application will be described in detail below. The embodiments of the present application should not be construed as limiting the present application.

[0033] As used in the present application, the terms "comprising", "containing" and "including" are used in their open, non-limiting sense.

[0034] In addition, sometimes quantities, ratios and other numerical values are presented in a range format in this document. It should be understood that such range formats are for convenience and brevity, and should be understood flexibly, including not only the explicitly specified numerical values as range limits, but also all individual numerical values or sub-ranges covered within the range, as if each numerical value and sub-range were explicitly specified.

[0035] In the detailed embodiments and claims, a list of items connected by the terms "one or more of", "one or more of", "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A or B" means only A; only B; or A and B. In another example, if items A, B and C are listed, then the phrase "at least one of A, B or C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0036] diaphragm

[0037] As an important component of an electrochemical device, the separator is located between the positive and negative electrodes of the electrochemical device to isolate the positive and negative electrodes while transporting metal ions (e.g., lithium ions), achieving the function of preventing short circuits. However, when used abnormally, the temperature inside the electrode assembly of the electrochemical device may rise sharply, causing the separator to undergo significant thermal shrinkage or even melting, resulting in direct contact between the positive and negative electrodes and short circuits. Once a short circuit occurs, thermal runaway will occur inside the electrochemical device, leading to safety problems such as fire and explosion.

[0038] In the prior art, an oil-based separator (e.g., aramid high-temperature resistant separator) is usually used in an electrochemical device to improve the high-temperature tolerance of the separator. However, the oil-based separator has high requirements for the production process and causes problems such as environmental pollution. In addition, compared with the water-based separator, the production cost of the oil-based separator is higher, thus correspondingly increasing the production cost of the electrochemical device.

[0039] Based at least on the above insights into the prior art, the present application takes a water-based separator as the research object and improves the thermal stability and mechanical safety performance of the separator by improving the composition and content of the porous coating in the separator. Specifically, the separator proposed in the present application includes a porous substrate and a porous coating. The porous coating is disposed on at least one surface of the porous substrate. The porous coating includes inorganic particles and a binder. Among them, a main feature of the separator of the present application is that: the binder includes a first binder, the first binder includes a metal element, wherein a circular needle with a diameter of R and heated to 500 °C is used to perform thermal puncture on the separator to obtain a rupture hole generated on the separator. Connect any two points on the edge of the rupture hole and calculate the distance between the two points. Take the maximum value as r, and wherein, 400 μm ≤ R ≤ 1000 μm and 0.9 ≤ r / R ≤ 5.

[0040] According to one embodiment of the present application, Figure 1 shows an image taken by a CCD camera of the separator after thermal puncture with a circular needle with a diameter of R (500 μm) and heated to 500 °C. As Figure 1 shown, a rupture hole will be generated on the separator after thermal puncture with a high-temperature circular needle. Under the observation of the CCD camera, find the two points on the edge of the rupture hole with the farthest distance, and calculate the distance r between the two points. Wherein r is 451 μm. In contrast, when the same thermal puncture experiment is carried out using the water-based separator commonly used in the prior art, it can be seen from Figure 2 that the water-based separator of the prior art will produce a larger damaged hole area. For example, the distance between the two points on the edge of the hole with the farthest distance is as high as 3088 μm. The increase in the damaged hole area will increase the contact risk between the positive and negative electrodes, resulting in internal short circuits of the battery and causing thermal runaway of the battery.

[0041] In some embodiments, R can be, but is not limited to, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, or 1000 μm, or within the range composed of any two of the above values. In some embodiments, r / R can be, but is not limited to, 0.9, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, or 5, or within the range composed of any two of the above values. In some embodiments, 1 ≤ r / R ≤ 1.5. In some embodiments, 1 ≤ r / R ≤ 2.5. In some embodiments, 1 ≤ r / R ≤ 3.5. In some embodiments, 1 ≤ r / R ≤ 4.5.

[0042] In some embodiments, 400 μm ≤ r ≤ 1500 μm. For example, r can be, but is not limited to, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, 1100 μm, 1200 μm, 1300 μm, 1400 μm, or 1500 μm, or within the range composed of any two of the above values.

[0043] In some embodiments, the compressive strength of the binder is α MPa, where 0.5 ≤ α ≤ 10. When the compressive strength of the binder is within the above range, the binder can not only firmly connect the dispersed inorganic particles into a network skeleton structure, but also bond the inorganic particles to the substrate to become an integral body, ultimately improving the overall compressive strength of the separator, enabling the separator to better resist stress shocks, further suppressing breakage caused by shocks, and thus further improving the thermal safety performance and mechanical safety performance of the electrochemical device. In some embodiments, α can be, but is not limited to, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, or within the range composed of any two of the above values.

[0044] In some embodiments, the glass transition temperature of the binder is Tg, where 150 °C ≤ Tg ≤ 300 °C. When the glass transition temperature of the binder is within the above range, the binder is not easily softened or embrittled at high temperatures, and can have an appropriate strength to resist stress shocks, reducing breakage caused by shocks, and thus further improving the thermal safety performance and mechanical safety performance of the electrochemical device. In some embodiments, Tg can be, but is not limited to, 150 °C, 200 °C, 250 °C, or 300 °C, or within the range composed of any two of the above values.

[0045] In some embodiments, the metal element in the first binder includes at least one of metal elements with a valence of +1, +2, or +3. In some embodiments, the first binder further includes at least one of a carboxyl group or a sulfonic acid group. The metal ions in the first binder can complex with the carboxyl group or sulfonic acid group therein to form metal bonds, further enhancing the strength of the binder (e.g., compressive strength), enabling the separator to better withstand stress shocks, suppressing breakage caused by shocks, and thus further improving the thermal safety performance and mechanical safety performance of the electrochemical device.

[0046] In some embodiments, the metal element in the first binder includes at least two of metal elements with a valence of +1, +2, or +3. Compared with containing only one metal element, using at least two different metal elements in the first binder can further enhance the strength of the binder, thereby further improving the ability of the separator to withstand stress shocks and its stability at high temperatures. This may be because different metal elements are more likely to form interpenetrating metal bonds with the carboxyl group and / or sulfonic acid group in the binder to construct an interpenetrating cross-linked network structure, thereby improving the mechanical properties of the material.

[0047] In some embodiments, the metal element with a valence of +1 includes at least one of Li, Na, or K. In some embodiments, the metal element with a valence of +2 includes at least one of Ca, Mg, or Ba. In some embodiments, the metal element with a valence of +3 includes Al. In some embodiments, the first binder includes at least one of Li, Na, Ca, Mg, or Al.

[0048] In some embodiments, the first binder simultaneously includes metal elements with valences of +1 and +2, and the molar content ratio of the metal element with a valence of +1 to the metal element with a valence of +2 is a, where 1 ≤ a ≤ 10. In some embodiments, a can be, but is not limited to, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, or within the range composed of any two of the above values.

[0049] In some embodiments, the first binder simultaneously includes metal elements with valences of +1 and +3, and the molar content ratio of the metal element with a valence of +1 to the metal element with a valence of +3 is b, where 1 ≤ b ≤ 50. In some embodiments, b can be, but is not limited to, 1, 10, 20, 30, 40, or 50, or within the range composed of any two of the above values.

[0050] In some embodiments, the first binder simultaneously includes metal elements with valences of +2 and +3, where the molar content ratio of the metal element with a valence of +2 to the metal element with a valence of +3 is p, and 1 ≤ p ≤ 10. In some embodiments, p can be, but is not limited to, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, or within the range formed by any two of the above values.

[0051] In some embodiments, the first binder satisfies at least one of the following conditions:

[0052] (1) The first binder simultaneously includes Li and Na, where the molar content ratio of Li to Na is c, and 1 ≤ c ≤ 8;

[0053] (2) The first binder simultaneously includes Li and Mg, where the molar content ratio of Li to Mg is d, and 2 ≤ d ≤ 4;

[0054] (3) The first binder simultaneously includes Na and Mg, where the molar content ratio of Na to Mg is e, and 2 ≤ e ≤ 4;

[0055] (4) The first binder simultaneously includes Li and Ca, where the molar content ratio of Li to Ca is f, and 2 ≤ f ≤ 4;

[0056] (5) The first binder simultaneously includes Na and Ca, where the molar content ratio of Na to Ca is g, and 2 ≤ g ≤ 4;

[0057] (6) The first binder simultaneously includes Li and Al, where the molar content ratio of Li to Al is m, and 1 ≤ m ≤ 20;

[0058] (7) The first binder simultaneously includes Na and Al, where the molar content ratio of Na to Al is n, and 1 ≤ n ≤ 20.

[0059] In some embodiments, the pH value of the first binder can be adjusted by adjusting the content and ratio of carboxyl or sulfonic acid groups and metal elements in the first binder. In some embodiments, the pH value of the first binder is pH1, and 7 ≤ pH1 ≤ 11. When the pH value of the first binder is within the above range, the first binder can provide sufficient metal ions to form metal ion complex bonds with the carboxyl or sulfonic acid groups therein, thereby further improving the thermal stability and mechanical properties of the separator. In some embodiments, pH1 can be, but is not limited to, 7, 8, 9, 10, or 11, or within the range formed by any two of the above values.

[0060] In some embodiments, the first binder includes, but is not limited to, at least one of the following: lithium methylcellulose, lithium carboxymethylcellulose, sodium hydroxypropyl methylcellulose, sodium acrylate, calcium methacrylate, calcium acrylate, magnesium acrylate, magnesium methylcellulose, sodium carboxymethylcellulose, calcium methylcellulose, or aluminum methylcellulose.

[0061] In some embodiments, based on the total weight of the porous coating, the weight content of the first binder is w1%, where 0.5 ≤ w1 ≤ 4. In some embodiments, w1 can be, but is not limited to, 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, or 4, or within the range formed by any two of the above values.

[0062] In some embodiments, the first binder is a solution-type binder. A solution-type binder refers to a binder polymer dissolved in a solvent to form a solution. In some embodiments, the solvent is water.

[0063] In some embodiments, the binder includes a second binder. In some embodiments, the second binder is a binder of a different type from the first binder. For example, the second binder is an emulsion binder. An emulsion binder refers to a binder polymer dispersed in a dispersion medium to form an emulsion. In some embodiments, the dispersion medium is water.

[0064] In some embodiments, based on the total weight of the porous coating, the weight content of the second binder is w2%, where 2.5 ≤ w2 ≤ 5. In some embodiments, w2 can be, but is not limited to, 2.5, 3, 4, or 5, or within the range formed by any two of the above values.

[0065] In some embodiments, the second binder includes at least one of a carboxyl group or a sulfonic acid group. When the binder includes both the first binder and the second binder, the metal ions in the first binder can also complex with the carboxyl group or sulfonic acid group in the second binder to form metal bonds and an interpenetrating network structure, thereby further improving the strength of the binder and enhancing the ability of the separator to resist external force impact, and thus further improving the thermal safety performance and mechanical safety performance of the electrochemical device.

[0066] In addition, when the binder includes both the first binder and the second binder, the strength of the binder can be further improved by optimizing the weight ratio of the first binder to the second binder. In some embodiments, based on the total weight of the porous coating, the weight ratio of the first binder to the second binder (i.e., w1 / w2) is β, where 0.2 ≤ β ≤ 4. In some embodiments, β can be, but is not limited to, 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, or 4, or within the range formed by any two of the above values.

[0067] In some embodiments, the pH value of the second binder can be adjusted by adjusting the content and ratio of carboxyl groups and / or sulfonic acid groups in the second binder. In some embodiments, the pH value of the second binder is pH2, where 3 ≤ pH2 ≤ 7. When the pH value of the second binder is within the above range, the thermal stability and mechanical properties of the separator can be further improved. This may be because the second binder can provide additional active groups (such as carboxyl groups or sulfonic acid groups), increasing the probability of its complexation with metal ions, forming more metal ion complexation bonds, and improving the mechanical properties of the material. In some embodiments, pH2 can be, but is not limited to, 3, 4, 5, 6, or 7, or within the range formed by any two of the above values.

[0068] In some embodiments, the second binder includes, but is not limited to, at least one of the following: butyl acrylate, ethyl acrylate, butyl methacrylate, polymethyl methacrylate, or styrene-butadiene rubber.

[0069] In some embodiments, the specific surface area of the inorganic particles in the porous coating is S BET m 2 / g, where 2 ≤ S BET ≤ 10. In some embodiments, S BET can be, but is not limited to, 2, 3, 4, 5, 6, 7, 8, 9, or 10, or within the range formed by any two of the above values. In some embodiments, 2 ≤ S BET ≤ 5.

[0070] In some embodiments, the particle size Dv50 of the inorganic particles satisfies 0.3 μm ≤ Dv50 ≤ 3 μm. In some embodiments, the particle size Dv99 of the inorganic particles satisfies Dv99 ≤ 4 μm. Among them, Dv50 can also be called the median particle size, which is the particle size value corresponding to 50% in the volume distribution; Dv99 is the particle size value corresponding to 99% in the volume distribution. When the particle size of the inorganic particles is within the above range, it is beneficial to reduce the thickness of the porous coating, improve the energy density of the electrochemical device, and ensure that the bonding sites are within a suitable range, reduce the amount of binder, and improve the kinetic performance of the electrochemical device.

[0071] In some embodiments, the inorganic particles that can be used for the separator of the present application include, but are not limited to, at least one of the following: aluminum oxide, boehmite, zirconia, boron nitride, silicon nitride, aluminum nitride, silicon dioxide, magnesium oxide, titanium oxide, silicon carbide, aluminum hydroxide, or magnesium hydroxide.

[0072] In some embodiments, the porous coating further includes a wetting agent, and the function of the wetting agent is to improve the wettability of the porous coating slurry to the substrate and avoid uncoated areas during the coating process. In addition, by optimizing the weight percentages of the inorganic particles, binder, and wetting agent in the porous coating, the thermal safety performance and mechanical stability of the separator can be further enhanced. In some embodiments, based on the total weight of the porous coating, the content of the inorganic particles is m1 wt%, the content of the binder is m2 wt%, and the content of the wetting agent is m3 wt%, where 90 ≤ m1 ≤ 96, 3 ≤ m2 ≤ 9, 0.5 ≤ m3 ≤ 2, and m1 + m2 + m3 = 100.

[0073] In some embodiments, the wetting agent includes, but is not limited to, at least one of the following: polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene-polyoxypropylene block copolymer, or siloxane.

[0074] In some embodiments, the separator of the present application is placed at 150 °C for 1 hour. Compared with the initial length of the separator, the thermal shrinkage rate of the separator in the length (MD) direction is L1, and compared with the initial width of the separator, the thermal shrinkage rate of the separator in the width (TD) direction is L2, where L1 < 10%, L2 < 10%, and 0.75 ≤ L1 / L2 ≤ 1.2. In some embodiments, L1 and L2 can be, but are not limited to, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or 9%, or within the range composed of any two of the above values. In some embodiments, L1 / L2 can be, but is not limited to, 0.8, 0.9, 1.0, 1.1, or 1.2, or within the range composed of any two of the above values.

[0075] In some embodiments, the thickness of the porous coating is T μm, where 0.5 ≤ T ≤ 3. When the thickness of the porous coating is within the above range, the energy density of the electrochemical device can be improved, and the kinetic performance of the electrochemical device can also be improved. In some embodiments, T can be, but is not limited to, 0.5, 1, 1.5, 2, 2.5, or 3, or within the range composed of any two of the above values. Wherein, when the porous coating is coated on both surfaces of the porous substrate, the "thickness of the porous coating" mentioned above refers to the sum of the thicknesses of the porous coatings coated on these two surfaces.

[0076] In some embodiments, the adhesion of the porous coating is F N / m, where 5 ≤ F ≤ 100. When the adhesion of the porous coating is within the above range, not only can the inorganic particles be firmly adhered to the porous substrate and not easily fall off, but also excessive binders do not have to be used to deteriorate the kinetic performance of the electrochemical device. In some embodiments, F can be, but is not limited to, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100, or within the range composed of any two of the above values. In some embodiments, 20 ≤ F ≤ 85.

[0077] In some embodiments, the porous substrate may include, but is not limited to, at least one of the following: polyethylene (PE), ultra-high molecular weight polyethylene (UHMWPE), high-density polyethylene (HDPE), polypropylene (PP), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), cellulose, polyimide, polystyrene (PS), poly-4-methyl-1-pentene (TPX), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polytetrafluoroethylene (PTFE), and polysulfone.

[0078] The present application further provides an electrochemical device comprising the separator of the above embodiments of the present application. In some embodiments, the electrochemical device further includes a negative electrode, a positive electrode, and an electrolyte, wherein the separator is located between the positive electrode and the negative electrode. As follows, the present application will describe in detail the compositions of the positive electrode, the negative electrode, and the electrolyte.

[0079] positive electrode

[0080] The positive electrode includes a positive electrode material, and the positive electrode material includes a positive electrode material capable of absorbing and releasing lithium (Li) (hereinafter, sometimes referred to as "a positive electrode material capable of absorbing / releasing lithium Li"). Examples of the positive electrode material capable of absorbing / releasing lithium (Li) may include lithium cobaltate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium manganate, lithium manganese iron phosphate, lithium vanadate, lithium vanadium oxyphosphate, lithium iron phosphate, lithium titanate, and lithium-rich manganese-based materials.

[0081] Specifically, the chemical formula of lithium cobaltate may be as shown in Chemical Formula 1:

[0082] Li x1 Co a1 M1 b1 O 2-c1 Chemical Formula 1

[0083] Where M1 represents at least one selected from nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), lanthanum (La), zirconium (Zr), and silicon (Si), and the values of x1, a1, b1, and c1 are respectively in the following ranges: 0.8 ≤ x1 ≤ 1.2, 0.8 ≤ a1 ≤ 1, 0 ≤ b1 ≤ 0.2, -0.1 ≤ c1 ≤ 0.2;

[0084] The chemical formula of lithium nickel cobalt manganate or lithium nickel cobalt aluminate can be as shown in Chemical Formula 2:

[0085] Li y1 Ni d1 M2 e1 O 2-f1 Chemical Formula 2

[0086] Where M2 represents at least one selected from cobalt (Co), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), zirconium (Zr), and silicon (Si), and the values of y1, d1, e1, and f1 are respectively in the following ranges: 0.8 ≤ y1 ≤ 1.2, 0.3 ≤ d1 ≤ 0.98, 0.02 ≤ e1 ≤ 0.7, -0.1 ≤ f1 ≤ 0.2;

[0087] The chemical formula of lithium manganate can be as shown in Chemical Formula 3:

[0088] Li z1 Mn 2-g1 M 3g1 O 4-h1 Chemical Formula 3

[0089] Where M3 represents at least one selected from cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W), and the values of z1, g1, and h1 are respectively in the following ranges: 0.8 ≤ z1 ≤ 1.2, 0 ≤ g1 < 1.0, and -0.2 ≤ h1 ≤ 0.2.

[0090] negative electrode

[0091] The negative electrode includes a negative electrode material, and the negative electrode material includes a negative electrode material capable of absorbing and releasing lithium (Li) (hereinafter, sometimes referred to as "negative electrode material capable of absorbing / releasing lithium Li"). Examples of the negative electrode material capable of absorbing / releasing lithium (Li) may include carbon materials, metal compounds, oxides, sulfides, nitrides of lithium such as LiN3, lithium metal, metals that form alloys with lithium, and polymer materials.

[0092] Examples of carbon materials may include low graphitized carbon, easily graphitized carbon, artificial graphite, natural graphite, mesocarbon microbeads, soft carbon, hard carbon, pyrolytic carbon, coke, glassy carbon, sintered bodies of organic polymer compounds, carbon fibers, and activated carbon. Among them, coke may include pitch coke, needle coke, and petroleum coke. The sintered body of organic polymer compound refers to a material obtained by carbonizing polymer materials such as phenol plastics or furan resins at an appropriate temperature, and some of these materials are classified into low graphitized carbon or easily graphitized carbon. Examples of polymer materials may include polyacetylene and polypyrrole.

[0093] Among these negative electrode materials capable of absorbing / releasing lithium (Li), furthermore, materials with charge and discharge voltages close to those of lithium metal are selected. This is because the lower the charge and discharge voltage of the negative electrode material, the easier it is for an electrochemical device (such as a lithium-ion battery) to have a higher energy density. Among them, carbon materials can be selected as the negative electrode material because their crystal structures only change slightly during charge and discharge, and thus, good cycle characteristics and large charge and discharge capacities can be obtained. In particular, graphite can be selected because it can provide a large electrochemical equivalent and a high energy density.

[0094] In addition, the negative electrode material capable of absorbing / releasing lithium (Li) may include elemental lithium metal, metal elements and semi-metal elements that can form alloys with lithium (Li), alloys and compounds including such elements, etc. In particular, they are used together with carbon materials because in this case, good cycle characteristics and high energy density can be obtained. In addition to alloys including two or more metal elements, the alloys used here also include alloys containing one or more metal elements and one or more semi-metal elements. The alloy can be in the following states: solid solution, eutectic crystal (eutectic mixture), intermetallic compound, and their mixtures.

[0095] Examples of metal elements and semi-metal elements may include tin (Sn), lead (Pb), aluminum (Al), indium (In), silicon (Si), zinc (Zn), antimony (Sb), bismuth (Bi), cadmium (Cd), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y), and hafnium (Hf). Examples of the above alloys and compounds may include those with the chemical formula: Mas Mb t Li u materials and having the chemical formula: Ma p Mc q Md r materials. In these chemical formulas, Ma represents at least one element selected from metallic elements and semi-metallic elements that can form an alloy with lithium; Mb represents at least one element selected from metallic elements and semi-metallic elements other than lithium and Ma; Mc represents at least one element selected from non-metallic elements; Md represents at least one element selected from metallic elements and semi-metallic elements other than Ma; and s, t, u, p, q, and r satisfy s > 0, t ≥ 0, u ≥ 0, p > 0, q > 0, and r ≥ 0.

[0096] In addition, inorganic compounds not including lithium (Li) can be used in the negative electrode, such as MnO2, V2O5, V6O 13 , NiS, and MoS.

[0097] electrolyte

[0098] The electrolyte can be one or more of a gel electrolyte, a solid electrolyte, and an electrolytic solution, and the electrolytic solution includes a lithium salt and a non-aqueous solvent.

[0099] The lithium salt is selected from one or more of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and lithium difluoroborate. For example, LiPF6 is selected as the lithium salt because it can give a high ionic conductivity and improve the cycling characteristics.

[0100] The non-aqueous solvent can be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof.

[0101] The carbonate compound can be a linear carbonate compound, a cyclic carbonate compound, a fluorinated carbonate compound, or a combination thereof.

[0102] Examples of chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and combinations thereof. Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene ethylene carbonate (VEC), and combinations thereof. Examples of fluorinated carbonate compounds are 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, trifluoromethyl ethylene carbonate, and combinations thereof.

[0103] Examples of carboxylic acid ester compounds are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, methyl formate, and combinations thereof.

[0104] Examples of ether compounds are dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.

[0105] Examples of other organic solvents are dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters, and combinations thereof.

[0106] The electrochemical device of the present application includes any device in which an electrochemical reaction occurs. Specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a sodium secondary battery, a lithium secondary battery, or a polymer secondary battery.

[0107] The present application further provides an electronic device, which includes the electrochemical device according to the present application.

[0108] The use of the electrochemical device of the present application is not particularly limited, and it can be used in any electronic device known in the prior art. In some embodiments, the electrochemical device of the present application can be used in, but not limited to, laptop computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, liquid crystal TVs, portable cleaners, portable CD players, minidiscs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorized bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and capacitors, etc.

[0109] Taking a lithium-ion battery as an example below and in combination with specific embodiments, the preparation of the lithium-ion battery will be described. Those skilled in the art will understand that the preparation methods described in the present application are only examples, and any other suitable preparation methods are within the scope of the present application.

[0110] example

[0111] The following describes the performance evaluation of the embodiments and comparative examples of the lithium-ion battery according to the present application.

[0112] Preparation of a lithium-ion battery

[0113] 1. Preparation of the binder

[0114] Preparation process of the acrylic binder: 1. Add an appropriate amount of acrylic monomer to the reaction kettle, and add an appropriate amount of catalyst, and stir evenly at a slow speed; 2. Add an appropriate amount of monomer containing a sulfonic acid group or a carboxyl group (for example: methanesulfonic acid or methacrylic acid) to the reaction kettle; 3. Introduce an inert gas into the reaction kettle to form a reaction protection atmosphere; 4. Heat the reaction kettle to the reaction temperature, and the monomers polymerize to obtain a binder containing two functional groups; 5. After the reaction is completed, the pH of the binder discharge can be adjusted by adding a metal base to obtain the required binder.

[0115] Among them, by changing the type of reaction monomers, binders containing different functional groups can be obtained. By selecting different types of metal bases (for example: sodium hydroxide, magnesium hydroxide) or different amounts of added metal bases, the design and regulation of the type and content ratio of the metal base in the binder can be achieved;

[0116] Preparation process of the cellulose binder: 1. Place an appropriate amount of raw material cellulose in the reaction kettle, and then add a metal base (sodium hydroxide) to alkalize the cellulose to obtain alkalized cellulose; 2. Add an appropriate amount of chloroacetic acid to the alkalized cellulose for etherification reaction, and finally obtain a sodium carboxymethyl cellulose binder.

[0117] Among them, during the alkalization treatment, by changing relevant process parameters such as the type of metal base or the proportion of metal base, the design and regulation of the type and content ratio of metal base in the binder can be achieved.

[0118] 2. Preparation method of separator

[0119] After fully mixing water and inorganic particles, a certain amount of binder is added, and the mixture is stirred evenly in a stirrer. Subsequently, a certain amount of wetting agent is added to the above slurry and stirred continuously until evenly mixed. Finally, it is evenly coated on one side of the substrate PE to an appropriate thickness, and after the coating is completed, it is placed in an oven to dry to obtain the separator of the present application. For the composition and content of inorganic particles, binder and wetting agent, as well as parameters such as the coating thickness, please refer to Table 1.

[0120] 3. Preparation method of lithium-ion battery

[0121] The cathode active material lithium cobaltate, conductive carbon (Super P), and binder polyvinylidene fluoride (PVDF) are dissolved in an N-methylpyrrolidone solvent system according to a weight ratio of 96:2:2, and stirred thoroughly and evenly to prepare a cathode slurry. The cathode slurry is coated on aluminum foil, dried, cold-pressed, and slit to obtain the cathode.

[0122] The anode active material artificial graphite, conductive agent (Super P), binder styrene-butadiene rubber, and thickening agent sodium carboxymethyl cellulose are dissolved in a deionized water solvent system according to a weight ratio of 98:0.5:1:0.5, and stirred thoroughly and evenly to prepare an anode slurry. The anode slurry is coated on copper foil, dried, cold-pressed, and slit to obtain the anode.

[0123] A solution prepared by mixing lithium salt LiPF6 and non-aqueous organic solvents (ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC): propyl propionate (PP): vinylene carbonate (VC)) = 20:30:20:28:2, mass ratio) according to a mass ratio of 8:92 is used as the electrolyte of the lithium-ion battery.

[0124] The cathode, separator, and anode are stacked in sequence, with the separator placed between the cathode and the anode, and wound to obtain an electrode assembly. The electrode assembly is placed in an outer package, injected with electrolyte and encapsulated, and after formation, the final lithium-ion battery product is made.

[0125] II. Test method

[0126] 1. Puncture test of separator

[0127] First, fix the porous coating diaphragm flat on the test fixture and place the fixture vertically below the moving bracket of the high-speed tensile testing machine. Secondly, vertically fix the test hot needle on the moving bracket of the high-speed tensile testing machine to ensure that the hot needle can vertically pierce the diaphragm. Then, the moving bracket of the high-speed tensile testing machine drives the hot needle to vertically pierce the diaphragm at a certain speed (20 cm / min), with a piercing depth of 2 - 4 cm. After piercing, the hot needle stops for 1 min and then returns to the initial position. Finally, take out the diaphragm sample, measure any two points on the edge of the rupture hole under the CCD camera, connect the two points, and calculate the distance between the two points. Take the maximum value as r.

[0128] 2. Compressive strength test of the adhesive

[0129] Place the adhesive film sample (with dimensions of 10 mm × 10 mm × 10 mm) in the middle position between the two pressing plates of the universal testing machine. Apply stress to compress the sample at a constant rate (10 mm / min) in the vertical direction along the two end faces of the sample, causing the sample to shorten axially and increase radially, resulting in compressive deformation until the sample ruptures. Read the maximum load stress value Pmax applied by the universal testing machine, and calculate the compressive strength α of the adhesive through the following formula:

[0130] α = Pmax / S,

[0131] where S is the initial cross-sectional area of the sample.

[0132] 3. Glass transition temperature test of the adhesive

[0133] Take a certain amount (10 - 20 mg) of the adhesive film sample and place it in the heating crucible of the differential scanning calorimeter. Start the equipment test program, and obtain the Temp-DSC curve graph through the test software. Generally, read the temperature corresponding to the first change step of the curve as the glass transition temperature of the adhesive.

[0134] 4. Determination of metal elements and their content ratios in the adhesive

[0135] Disassemble the battery in the glove box. After taking out the diaphragm and removing the PVDF / PMMA adhesive layer coated on the porous coating, leave the porous coating, and then redisperse the porous coating in water by the "water washing" method. After centrifuging to separate the inorganic particles, obtain the water-washed clear liquid, which includes the adhesive. Determine the water-washed clear liquid through inductively coupled plasma (ICP) testing to obtain the metal elements and their content ratios in the adhesive.

[0136] 5. Specific surface area test of inorganic particles

[0137] Start the test software, place a certain amount of inorganic particles in the sample test chamber, and use the BET specific surface area measurement method to measure the specific surface area of the inorganic particles. After the test is completed, the test software automatically reads the specific surface area value of the inorganic particles.

[0138] 6. Particle Size Test of Inorganic Particles

[0139] Start the test software, place the inorganic particles that meet the test quality requirements in the test chamber of the Malvern 3000 laser particle size analyzer, then start the ultrasound for 5 minutes to ensure that the particles are not agglomerated, and then enter the particle size test step, and the software outputs the particle size distribution curve.

[0140] 7. Thermal Shrinkage Test of the Diaphragm in the MD and TD Directions

[0141] First, cut the diaphragm into a size with a length of MD1 and a width of TD1 (MD1 = 10 cm, TD1 = 5 cm) to obtain a test diaphragm sample. Second, place the cut diaphragm sample between two A4 papers and bake it in an oven at 150 °C for 1 hour. Then, use a CCD camera to measure the length and width of the diaphragm sample baked at 150 °C for 1 hour, and record them as MD2 and TD2 respectively. Finally, calculate the thermal shrinkage rate L1 of the diaphragm in the MD direction and the thermal shrinkage rate L2 of the diaphragm in the TD direction through the following formula:

[0142] L1 = (MD1 - MD2) / MD1;

[0143] L2 = (TD1 - TD2) / TD1.

[0144] 8. Thickness Test of the Porous Coating

[0145] Use a bench-top diaphragm thickness gauge to measure the thickness of the substrate and the diaphragm respectively, and record them as T1 μm and T μm. Calculate the thickness T2 μm of the porous coating using the following formula:

[0146] T2 = T - T1.

[0147] 9. Adhesion Test of the Porous Coating

[0148] First, lay the coated separator sample flat on a glass plate, with the porous coating facing up, and fix the four sides with tape to ensure that the separator is flat and fixed on the glass plate. Secondly, attach a special tape for peel strength test flat on the surface of the porous coating. Then, use a 1KG roller to roll back and forth over the area where the special tape for peel strength test is pasted. After that, cut out a 15mm×54.2mm separator test sample from the area where the special tape for peel strength test is pasted. Finally, fix one side of the separator test sample at one end of a high-speed tensile testing machine, and fix the tape side at one end of the moving bracket of the high-speed tensile testing machine. The moving bracket stretches the tape at a certain speed to make the tape peel off from the separator surface at 180°, and the value read by the test software is the adhesion of the porous coating.

[0149] 10. Heat box test

[0150] Take 100 lithium-ion battery samples and charge them at a constant current of 0.5C rate to 4.5V at room temperature, and then further charge them at a constant voltage of 4.5V until the current is lower than 0.05C to make them in a fully charged state of 4.5V. Put the lithium-ion battery samples into an oven and place them at 137°C for 1h. If the lithium-ion batteries do not smoke, catch fire or explode, they are recorded as passing, otherwise they are recorded as failing. The heat box pass rate is the ratio of the number of lithium-ion batteries passing the test to the total number of lithium-ion batteries.

[0151] 11. Nail penetration test

[0152] First, check the appearance of the battery and take pictures before and after the nail penetration test. Secondly, stick the temperature sensing wire at the center of the battery surface. Then, in a test environment of 20±5°C, place the test battery on the test bench and use a steel nail with a diameter of 2.5mm to test from the center position of the sample at a speed of 150mm / s until the sample is completely pierced. If the battery does not catch fire or explode, it means the battery passes the test.

[0153] III. Test results

[0154] Table 1 shows the effects of the pH value and content of the binder on the properties of the binder, separator and electrochemical properties. It can be seen from Table 1 that compared with the comparative example, in the examples, both the first binder and the second binder are used simultaneously, and the pH value and content of the first binder and the second binder are adjusted to meet 7≤pH1≤11, 3≤pH2≤7, 0.5≤w1≤4 and 2.5≤w2≤5. (1) A binder with a larger compressive strength and a higher Tg temperature can be obtained; (2) After baking at 150°C for 1 hour, the MD and TD thermal shrinkage rates of the separators in the examples are lower and smaller rupture holes are generated during the thermal puncture experiment; (3) All the electrochemical devices in the examples pass the heat box test and the nail penetration test.

[0155] Table 2 is an improvement based on Example 1-1. The total content of the first binder and the second binder added is the same, and the difference lies only in the content ratio of the first binder to the second binder. From the data in Table 2, it can be seen that by further adjusting the content ratio w1 / w2 of the first binder to the second binder to satisfy 0.2 ≤ w1 / w2 ≤ 1.6, the tensile strength of the binder, the thermal stability of the separator, and the safety performance of the electrochemical device can be further improved.

[0156] Table 3 is an improvement based on Example 1-1. The total charge content of the metal elements added to the first binder is the same (i.e., one acidic group (carboxyl / sulfonic acid group) in the first binder reacts with one 1+ valence metal ion, and so on), and the difference lies only in the types and content ratios of the metal elements added. From the data in Table 3, it can be seen that compared with adding only one metal element, after adding two metal elements to the first binder, the compressive strength of the binder, the thermal stability of the separator, and the safety performance of the electrochemical device have all been further improved.

[0157] In addition, from Examples 3-6 to 3-15, it can be seen that when the content ratio a of the metal element with a valence of +1 to the metal element with a valence of +2 is in the range of 1 ≤ a ≤ 10, the performance of the binder, the separator, and the electrochemical device can be further improved. From Examples 3-16 to 3-20, it can be seen that when the content ratio b of the metal element with a valence of +1 to the metal element with a valence of +3 is in the range of 1 ≤ b ≤ 50, the performance of the binder, the separator, and the electrochemical device can be further improved.

[0158] Table 4 is an improvement based on Example 3-7, and the difference lies only in the components, median particle size, and content of the inorganic particles. From Examples 3-7 to 4-5, it can be seen that using aluminum oxide, boehmite, zirconia, boron nitride, silicon nitride, or aluminum nitride as the inorganic particles in the porous coating can obtain separators and electrochemical devices with excellent high-temperature performance.

[0159] From Examples 4-6 to 4-12, it can be seen that when the median particle size Dv50 of the inorganic particles satisfies 0.3 μm ≤ Dv50 ≤ 2 μm, separators and electrochemical devices with more excellent high-temperature performance can be obtained.

[0160] From Examples 4-13 to 4-16, it can be seen that when the content m1 weight % of the inorganic particles satisfies 90 ≤ m1 ≤ 96 based on the total weight of the porous coating, separators and electrochemical devices with more excellent high-temperature performance can be obtained.

[0161] Table 5 is an improvement based on Examples 3 - 7, with the difference only lying in the components and contents of the wetting agent. As can be seen from Table 5, using polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene polyoxypropylene block copolymer or siloxane as the wetting agent in the porous coating can obtain diaphragms and electrochemical devices with excellent high - temperature performance.

[0162] As can be seen from Examples 5 - 3 to 5 - 7, based on the total weight of the porous coating, when the content m3 (weight %) of the wetting agent satisfies 0.5 ≤ m3 ≤ 1.5, diaphragms and electrochemical devices with even more excellent high - temperature performance can be obtained.

[0163] Table 6 is an improvement based on Examples 4 - 6, with the difference only lying in the thickness of the porous coating. As can be seen from Table 6, when the thickness T of the porous coating is within the range of 0.5 ≤ T ≤ 3, diaphragms and electrochemical devices with more excellent high - temperature performance can be obtained.

[0164] Throughout the specification, the references to "example", "partial example", "one example", "another example", "example", "specific example" or "partial example" mean that at least one example or instance in this application includes the specific features, structures, materials or characteristics described in that example or instance. Therefore, the descriptions that appear throughout the specification, such as: "in some examples", "in an example", "in one example", "in another example", "in an example", "in a specific example" or "example", do not necessarily refer to the same example or instance in this application. In addition, the specific features, structures, materials or characteristics herein can be combined in any suitable manner in one or more examples or instances.

[0165] Although the illustrative examples have been demonstrated and described, those skilled in the art should understand that the above - mentioned examples cannot be construed as a limitation to this application, and the examples can be changed, substituted and modified without departing from the spirit, principle and scope of this application.

[0166]

[0167]

[0168]

[0169]

[0170]

[0171]

[0172]

[0173]

[0174]

Claims

1. A separator, comprising: a porous substrate and a porous coating, the porous coating being disposed on at least one surface of the porous substrate, the porous coating including inorganic particles and a binder, the binder including a first binder, the first binder including a metal element; wherein, a circular needle with a diameter of R and heated to 500 °C is used to perform thermal puncture on the separator to obtain a rupture hole generated on the separator, any two points on the edge of the rupture hole are connected and the distance between the two points is calculated, and the maximum value is taken as r, and wherein, 400 μm ≤ R ≤ 1000 μm and 0.99 ≤ r / R ≤ 3; wherein, the first binder includes at least one of the following: lithium methylcellulose, lithium carboxymethylcellulose, sodium hydroxypropylmethylcellulose, sodium acrylate, calcium methacrylate, calcium acrylate, magnesium acrylate, magnesium methylcellulose, sodium carboxymethylcellulose, calcium methylcellulose or aluminum methylcellulose.

2. The diaphragm according to claim 1, wherein, 400 μm ≤ r ≤ 1500 μm.

3. The diaphragm according to claim 1, wherein, The compressive strength of the first binder is α MPa, 0.5 ≤ α ≤ 10.

4. The diaphragm according to claim 1, wherein, The glass transition temperature of the first binder is Tg, 150 °C ≤ Tg ≤ 300 °C.

5. The diaphragm according to claim 1, wherein, The metal element includes at least one of metal elements with a valence of +1, +2 or +3.

6. The diaphragm according to claim 1, wherein, The metal element includes at least two of the metal elements with a valence of +1, +2 or +3.

7. The separator according to claim 1, wherein, The first binder satisfies at least one of the following conditions (a) to (c): (a) The metal element with a valence of +1 includes at least one of Li or Na; (b) The metal element with a valence of +2 includes at least one of Ca or Mg; (c) The metal element with a valence of +3 includes Al.

8. The diaphragm according to claim 1, wherein, The first binder satisfies at least one of the following conditions (d) to (e): (d) The molar content ratio of the metal element with a valence of +1 to the metal element with a valence of +2 is a, 1 ≤ a ≤ 10; (e) The molar content ratio of the metal element with a valence of +1 to the metal element with a valence of +3 is b, 1 ≤ b ≤ 50.

9. The diaphragm according to claim 1, wherein, The first binder includes at least one of carboxyl or sulfonic acid group, and the pH value of the first binder is pH1, 7 ≤ pH1 ≤ 11.

10. The diaphragm according to claim 1, wherein, The binder further includes a second binder, and based on the total weight of the porous coating, the weight ratio of the first binder to the second binder is β, 0.2 ≤ β ≤ 4.

11. The diaphragm according to claim 10, wherein, The second binder includes at least one of carboxyl or sulfonic acid group, and the pH value of the second binder is pH2, 3 ≤ pH2 ≤ 7.

12. The diaphragm according to claim 10, wherein, The second binder includes at least one of the following: butyl acrylate, ethyl acrylate, butyl polymethacrylate, polymethyl methacrylate or styrene-butadiene rubber.

13. The diaphragm according to claim 1, wherein, The specific surface area of the inorganic particles is S BET m 2 / g, 2 ≤ S BET ≤ 10 14. The diaphragm according to claim 1, wherein, The particle sizes Dv50 and Dv99 of the inorganic particles respectively satisfy 0.3 μm ≤ Dv50 ≤ 3 μm and Dv99 ≤ 4 μm.

15. The diaphragm according to claim 1, wherein, The inorganic particles include at least one of the following: aluminum oxide, boehmite, zirconia, boron nitride, silicon nitride or aluminum nitride.

16. The diaphragm according to claim 1, wherein, The porous coating further includes a wetting agent. Based on the total weight of the porous coating, the content of the inorganic particles is m1 wt%, the content of the binder is m2 wt%, and the content of the wetting agent is m3 wt%, where 90 ≤ m1 ≤ 96, 3 ≤ m2 ≤ 9, 0.5 ≤ m3 ≤ 2, and m1 + m2 + m3 = 100.

17. The diaphragm according to claim 16, wherein, The wetting agent includes at least one of the following: polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene-polyoxypropylene block copolymer, or silicone.

18. The diaphragm according to claim 1, wherein, The separator is placed at 150 °C for 1 hour. Compared with the initial length and width of the separator, the thermal shrinkage rate of the separator in the length MD direction is L1, and the thermal shrinkage rate in the width TD direction is L2. L1 < 10%, L2 < 10%, and 0.75 ≤ L1 / L2 ≤ 1.

2.

19. The separator according to claim 1, wherein the thickness of the porous coating is T μm, 0.5 ≤ T ≤ 3.

20. The separator according to claim 1, wherein the adhesion of the porous coating is F N / m, 5 ≤ F ≤ 100.

21. The separator according to claim 1, wherein, 1.21≤r / R≤3。 22. An electrochemical device comprising the separator according to any one of claims 1-21.

23. An electronic device comprising the electrochemical device according to claim 22.

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