Separator and battery

Abstract

The present disclosure relates to the field of batteries, and particularly relates to a separator and a battery. The separator comprises a substrate and a ceramic layer, wherein the ceramic layer comprises inorganic particles and has a porous structure. The porous structure comprises first pores having a diameter greater than or equal to 0.5 μm. Within the range of 100×100 μm arbitrarily selected on the surface of the ceramic layer, the number of the first pores is 10-800. The separator satisfies the following relational expression: 1<D1 / D2<20, or 1<D1 / D3<20, wherein D1 is the average diameter of the first pores in the ceramic layer, with the unit thereof being μm; D2 is the average particle size of the inorganic particles, with the unit thereof being μm; and D3 is the Dv50 of the inorganic particles, with the unit thereof being μm. The separator of the present disclosure can have relatively high needling strength while maintaining a relatively high porosity, such that it can be ensured that the self-discharge and safety performance of a battery are not affected, while maintaining the rate, low-temperature discharge and long cycle performance of the battery.

Description

A separator and a battery Technical Field

[0001] This disclosure relates to the field of batteries, and more particularly to a separator and a battery including the separator. Background Technology

[0002] With the widespread adoption of 3C products and the rise of the electric vehicle market, the demand for lithium-ion rechargeable batteries is increasing. As a key component of lithium-ion rechargeable batteries, the separator directly affects their safety, long cycle life, and fast charging performance.

[0003] To improve the rate capability, low-temperature discharge performance, and fast-charge cycle performance of lithium-ion rechargeable batteries, the traditional solution is mainly to increase the porosity of the substrate. While increasing the porosity of the substrate can enhance the ion conductivity of the separator, thereby improving the battery's rate capability, low-temperature discharge performance, and fast-charge cycle performance, the needle penetration strength of the separator decreases with increasing substrate porosity, thus affecting the battery's self-discharge and safety performance. Summary of the Invention

[0004] To address the problem that existing separators cannot simultaneously achieve high porosity and high needle penetration strength, this disclosure provides a separator and a battery including the separator. The separator of this disclosure can maintain high porosity while possessing strong needle penetration strength, thereby ensuring that the battery's rate capability, low-temperature discharge performance, and long cycle life are not affected, while also guaranteeing that the battery's self-discharge and safety performance remain unaffected.

[0005] To achieve the above objectives, a first aspect of this disclosure provides a diaphragm comprising a substrate and a ceramic layer located on one or both surfaces of the substrate. The ceramic layer comprises inorganic particles and has a porous structure, comprising a first pore with a diameter greater than or equal to 0.5 μm. The number of the first pores is 10 to 800 within an arbitrarily selected range of 100 μm × 100 μm on the surface of the ceramic layer. The diaphragm satisfies the following relationship: 1 < D1 / D2 < 20, or 1 < D1 / D3 < 20, where D1 is the average diameter of the first pore in the ceramic layer in μm; D2 is the average particle size of the inorganic particles in μm; and D3 is the Dv50 of the inorganic particles in μm.

[0006] A second aspect of this disclosure provides a battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator as described in the first aspect of this disclosure, the separator being located between the positive electrode and the negative electrode.

[0007] Compared with the prior art, the present disclosure has at least the following advantages through the above technical solution:

[0008] The ceramic layer in the separator, containing highly stable inorganic particles, enhances the separator's high-temperature tolerance and reduces the risk of battery failure. The separator disclosed herein improves porosity by controlling the number of pores with a diameter ≥0.5 μm, thereby enhancing its ion conduction performance and improving the battery's fast-charging performance. Furthermore, by controlling the separator to satisfy the relationship 1 < D1 / D2 < 20 or 1 < D1 / D3 < 20, the separator's porosity is ensured, resulting in good lithium-ion transport capabilities, which helps improve the battery's rate capability and low-temperature discharge performance. Simultaneously, the appropriate packing density of inorganic particles further improves the separator's thermal stability and electrolyte storage performance, thus contributing to increased battery cycle life while ensuring that the battery's self-discharge and safety performance remain unaffected.

[0009] Other features and advantages of this disclosure will be described in detail in the following detailed description section.

[0010] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Attached Figure Description

[0011] Figure 1 shows a SEM image of the diaphragm in one embodiment of this disclosure.

[0012] Figure 2 shows the pore size distribution curve of the diaphragm in Embodiment II-1 of this disclosure.

[0013] Figure 3 shows a cross-sectional schematic diagram of the diaphragm of this disclosure.

[0014] Figure 4 shows a top view of the diaphragm of this disclosure.

[0015] Figure 5 shows a schematic diagram of the diaphragm structure of this disclosure.

[0016] Figure 6 shows an SEM image of the ceramic layer included in the diaphragm of Embodiment I-1 of this disclosure.

[0017] Figure 7 shows the pore size distribution of the diaphragms provided in Embodiment I-1 and Comparative Example I-1 of this disclosure.

[0018] Figure 8 shows a SEM image of the separator (ceramic layer excluding the first polymer) in a battery according to an embodiment of the present disclosure.

[0019] Figure 9 shows a SEM image of the separator (ceramic layer including a first polymer) in a battery according to an embodiment of the present invention.

[0020] Figure 10 shows a pore size distribution curve of the ceramic layer in one embodiment of the present invention.

[0021] Figure 11 shows a cross-sectional schematic diagram of the diaphragm (ceramic layer including the first polymer) of the present invention.

[0022] Figure 12 shows a top view of the diaphragm (ceramic layer including the first polymer) of the present invention.

[0023] Figure 13 shows a cross-sectional schematic diagram of the diaphragm (ceramic layer excluding the first polymer) of the present invention.

[0024] Figure 14 shows a top view of the diaphragm (ceramic layer excluding the first polymer) of the present invention. Detailed Implementation

[0025] The technical solutions of this disclosure will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of this disclosure and should not be construed as limiting the scope of protection of this disclosure. All technologies implemented based on the above content of this disclosure are covered within the scope of protection intended by this disclosure.

[0026] It should be noted that the numerical designations such as "first" and "second" in this disclosure are only used to distinguish different substances or methods of use, and do not represent a difference in order.

[0027] This disclosure provides a diaphragm comprising a substrate and a ceramic layer located on one or both surfaces of the substrate. The ceramic layer comprises inorganic particles and has a porous structure, the porous structure including a first pore with a diameter greater than or equal to 0.5 μm. Within an arbitrarily selected range of 100 μm × 100 μm on the surface of the ceramic layer, the number of the first pores is 10 to 800 (e.g., 10, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, or 80). (0), wherein the diaphragm satisfies the following relationship: 1 < D1 / D2 < 20 (e.g., 1.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 19.9), or, 1 < D1 / D3 < 20 (e.g., 1.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 19.9), where D1 is the average diameter of the first pore in the ceramic layer, in μm; D2 is the average particle size of the inorganic particles, in μm; and D3 is the Dv50 of the inorganic particles, in μm.

[0028] Figure 1 is a SEM image of the diaphragm in one embodiment of this disclosure. As can be seen from Figures 1, 8, and 9, the ceramic layer has a porous structure. The red circles in Figures 1, 8, and 9 mark pores with a diameter ≥ 0.5 μm. Each solid black circle represents a single pore with a diameter ≥ 0.5 μm. It should be noted that the solid black circles only mark some of the pores with a diameter ≥ 0.5 μm in Figures 1, 8, and 9, and do not represent all the pores with a diameter ≥ 0.5 μm in Figure 1. Figure 6 also shows that the ceramic layer includes pores with a diameter ≥ 0.5 μm.

[0029] As shown in Figures 3, 4, 5, 11, 12, 13 and 14, the diaphragm includes a substrate 1 and ceramic layers 2 located on both sides of the substrate 1. The ceramic layers include inorganic particles 23 and have a porous structure, with 22 being the pores of the ceramic layers.

[0030] The number of the first pores can be measured using a scanning electron microscope (SEM): under a scanning electron microscope (SEM), any area of ​​10000 μm on the surface of the ceramic layer... 2 Within a region (100μm×100μm), record the number of the first wells in that region. Repeat this operation 5 times and take the average value.

[0031] In this disclosure, the terms "diameter" and "average diameter" have different meanings. The term "diameter" refers to the diameter of a single pore. For example, "first pore" with a diameter ≥ 0.5 μm means a single pore with a diameter ≥ 0.5 μm; "number of first pores" means the number of pores with a diameter ≥ 0.5 μm. The term "average diameter" refers to the average diameter of all pores in a system. For example, the average diameter of the first pores in a ceramic layer means the average diameter of all pores in a system with a diameter ≥ 0.5 μm.

[0032] Both the diameter and the average diameter can be obtained through SEM testing. For example, they can be obtained by observing the surface of the ceramic layer at 50,000x magnification using an electrolytic radiometric scanning electron microscope (Hitachi, Ltd. S-3400N). The image size is 2.5μm × 1.8μm. It should be noted that the pixel count is 1,280 pixels × 960 pixels, and the size of one pixel is 2nm × 1.9nm. For the diameter, the smallest square or rectangle that completely surrounds a hole is drawn on the obtained image; that is, the square or rectangle whose ends meet the four sides of the square or rectangle. In the case of a square, the length of one side is taken as the diameter of the hole; in the case of a rectangle, the length of the longest side (major axis diameter) is taken as the diameter of the hole. For any 81 holes, the diameter of each hole is measured, and the average of these measurements is taken as the average diameter. It should be noted that when more than 81 holes are observed in the captured image, the average number of any 81 holes in that image is taken as the average diameter of the holes. If no 81 holes are observed in the image, multiple images are captured, and the average number of holes in the total of 81 holes is taken as the average diameter. Alternatively, the average diameter of the first hole can also be obtained by testing using SEM: Under a scanning electron microscope (SEM), the diameter of any area of ​​10000 μm on the surface of the porous ceramic layer is measured. 2 Within a 100μm × 100μm area, measure the diameter of pores with a diameter greater than or equal to 0.5μm within the area, and record the average pore diameter of the pores within the area (average pore diameter = sum of all pore diameters / total number of pores). Repeat the operation 5 times and take the average value as D1.

[0033] In this disclosure, the term "average particle size" refers to the average diameter of all particles in a system. The average particle size can be obtained by observing the surface of a ceramic layer at 50,000x magnification using an electrolytic radiometric scanning electron microscope (Hitachi, Ltd. S-3400N). The image size at this time is 2.5 μm × 1.8 μm. It should be noted that the pixel count is 1,280 pixels × 960 pixels, and the size of one pixel is 2 nm × 1.9 nm. For the average particle size, a square or rectangle with the smallest area completely surrounding a single particle is drawn on the obtained image; that is, a square or rectangle where the end of the particle is connected to the four sides of the square or rectangle. In the case of a square, the length of one side is taken as the particle size; in the case of a rectangle, the length of the longest side (major axis diameter) is taken as the particle size. For any 81 particles, their individual particle sizes are measured, and the average of these measurements is taken as the average particle size. It should be noted that when more than 81 particles are observed in the captured image, the average number of any 81 particle sizes in the image is taken as the average particle size. When no 81 particles are observed in the image, multiple images are captured, and the average number of a total of 81 particle sizes is taken as the average particle size.

[0034] The ceramic layer in the separator disclosed herein has a porous structure, comprising pores with a diameter ≥ 0.5 μm. Within an arbitrarily selected 100 μm × 100 μm range on the surface of the ceramic layer, the number of pores with a diameter ≥ 0.5 μm ranges from 10 to 800. By controlling the number of pores with a diameter ≥ 0.5 μm and the number of pores with a diameter ≥ 0.5 μm in the porous structure, a large number of pores can be present on the surface or inner layer of the ceramic layer of the separator, thereby increasing the porosity of the separator, improving its ion conductivity, and enhancing the rate capability and low-temperature discharge performance of the battery. This is achieved by controlling the number of pores with a diameter ≥ 0.5 μm in the ceramic layer. The ratio of the average diameter (D1) of the 5μm pores to the average particle size (D2) of the inorganic particles satisfies the relationship 1 < D1 / D2 < 20. This ratio allows for a large number of pores in the separator, further increasing its porosity and thus its ion transport performance, thereby enhancing the battery's fast-charging performance. Furthermore, it increases the packing density between inorganic particles, improving the separator's needle penetration strength and thermal stability, thereby reducing self-discharge and improving battery safety. This ensures that self-discharge and safety performance are not affected, while also improving the battery's long-cycle stability. When D1 / D2 ≤ 1, the packing density between inorganic particles is too low, resulting in poor separator thermal stability and lower battery safety. When D1 / D2 ≥ 20, the pore size is too large, leading to poor separator thermal stability and lower battery safety. Alternatively, by further defining the relationship between the first pore and the Dv50 of the inorganic particles, on the one hand, the porosity of the separator can be guaranteed, thereby giving the separator good lithium-ion transport capability, which helps to improve the battery rate and low-temperature discharge; on the other hand, the packing density between inorganic particles can be increased, improving the thermal stability of the separator, which helps to further ensure the battery's self-discharge, safety performance and cycle life.

[0035] In this disclosure, by controlling the number of pores with a diameter ≥ 0.5 μm and the ratio of the average diameter (D1) of the pores with a diameter ≥ 0.5 μm in the ceramic layer to the average particle size (D2) of the inorganic particles, or the ratio of the average diameter (D1) of the pores with a diameter ≥ 0.5 μm in the ceramic layer to the Dv50 (D3) of the inorganic particles, the battery can achieve higher fast-charging performance and higher long-cycle performance compared to the prior art. To further improve the effect, one or more of these technical features can be further optimized.

[0036] In one example, the number of the first pores is 50 to 500 within an arbitrarily selected 100μm × 100μm range on the surface of the ceramic layer.

[0037] In one instance, 2 ≤ D1 / D2 ≤ 16.

[0038] In one instance, 2 ≤ D1 / D2 ≤ 15.

[0039] In one instance, D1 is 0.5μm-10μm (e.g., 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm or 10μm).

[0040] In one instance, D1 is 1μm-8μm.

[0041] In one instance, D1 is 2μm-8μm.

[0042] In one instance, D2 is 0.1μm-3μm (e.g., 0.1μm, 0.5μm, 0.7μm, 0.8μm, 1μm, 1.2μm, 1.5μm, 1.7μm, 1.8μm, 2μm, 2.2μm, 2.5μm, 2.7μm, 2.8μm or 3μm).

[0043] In one instance, D2 is 0.5μm-2.5μm.

[0044] In one instance, D2 is 0.5μm-2μm.

[0045] According to one specific implementation, D1 is 0.5-10, D2 is 0.1-3, and the diaphragm satisfies the following relationship: 1 < D1 / D2 < 20.

[0046] According to one specific implementation, D1 is 0.5-8, D2 is 0.5-2.5, and the diaphragm satisfies the following relationship: 2≤D1 / D2≤16.

[0047] According to one specific implementation, D1 is 2-8, D2 is 0.5-2, and the diaphragm satisfies the following relationship: 2≤D1 / D2≤15.

[0048] In one example, the Dv50 of the inorganic particles is 0.1 μm-3 μm (e.g., 0.1 μm, 0.5 μm, 0.7 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.7 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.7 μm, 2.8 μm, or 3 μm). The Dv50 of the materials involved in this disclosure refers to the particle size value corresponding to 50% (by volume) of the cumulative particle size distribution curve, which can be considered as the median particle size of the material and is generally obtained by laser diffraction particle size analyzer.

[0049] In one example, the average diameter D1 of the first pore is 0.5 μm-10 μm, and the Dv50 of the inorganic particles is 0.1 μm-3 μm.

[0050] According to one specific implementation, D1 is 0.5-10, D3 is 0.1-3, and the diaphragm satisfies the following relationship: 1 < D1 / D3 < 20.

[0051] In one example, the substrate is a porous membrane layer, including at least one of woven membrane, nonwoven membrane, polyolefin membrane, separator paper, polyethylene terephthalate, polybutylene terephthalate, polystyrene, poly(p-phenylene), polynaphthalene, polyimide, polyamide, aramid, and poly(p-phenylenebenzodithiazole), wherein the material of the polyolefin membrane includes one or more of polyethylene, polypropylene, and composites of polyethylene and polypropylene.

[0052] To further improve the packing density between inorganic particles, thereby giving the separator good heat resistance and ensuring battery safety, and / or to further increase the porosity of the separator, thereby giving the separator good ion conduction and ensuring battery low-temperature and rate performance, in one specific embodiment, based on the total volume of pores in the ceramic layer, the volume ratio of the first pore is 20%-90% (e.g., 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%).

[0053] In this disclosure, the volume percentage of pores with a diameter ≥ 0.5 μm in the total volume of pores in the ceramic layer can be obtained by testing in the following way: For example, a mercury porosimetry test method can be used. Specifically, the pore size distribution curve of the entire diaphragm is obtained by testing with a mercury porosimetry instrument (as shown in Figures 2 and 7). The pore size of the substrate layer in the diaphragm does not exceed 0.08 μm. Therefore, the pore size distribution curve of the ceramic layer can be obtained by removing pores with a diameter ≤ 0.08 μm from the pore size distribution curve of the entire diaphragm. The ratio of the integral area of ​​pores with a diameter ≥ 0.5 μm in the pore size distribution curve of the ceramic layer to the total integral area of ​​the pore size distribution curve of the ceramic layer is the volume percentage of pores with a diameter ≥ 0.5 μm in the total volume of pores in the ceramic layer.

[0054] In some embodiments, the volume percentage of the first pore is 50%-80% based on the total volume of the pores in the ceramic layer; more specifically, V2 / V1 is any value among 21%, 23%, 25%, 27%, 30%, 35%, 37%, 40%, 45%, 47%, 50%, 55%, 57%, 60%, 65%, 67%, 70%, 75%, 77%, 80%, etc.

[0055] In one example, based on the total volume of pores in the ceramic layer, the volume percentage of pores with a diameter ≥ 0.5 μm is 20%-70% (e.g., 20%, 30%, 40%, 50%, 60%, or 70%). Controlling the volume percentage of pores with a diameter ≥ 0.5 μm in the total volume of the ceramic layer within this range allows the separator to have good heat resistance, thereby improving battery safety. It also increases the porosity of the separator, resulting in good ion permeability and improving the battery's fast-charge and long-cycle performance. When the volume percentage of pores with a diameter ≥ 0.5 μm in the total volume of the ceramic layer is less than 20%, the separator's porosity is low, resulting in insufficient ion permeability and failing to effectively improve the battery's fast-charge and long-cycle performance. When the volume percentage of pores with a diameter ≥ 0.5 μm in the total volume of the ceramic layer is higher than 70%, the separator's heat resistance is low, and battery safety cannot be guaranteed.

[0056] In this disclosure, the volume percentage of pores with a diameter ≥ 0.5 μm in the total volume of pores in the ceramic layer can be obtained by testing in the following way: For example, a mercury porosimetry test method can be used. Specifically, the pore size distribution curve of the entire diaphragm is obtained by testing with a mercury porosimetry instrument (as shown in Figures 2, 7, and 10). The pore size of the substrate layer in the diaphragm does not exceed 0.08 μm. Therefore, the pore size distribution curve of the ceramic layer can be obtained by removing pores with a diameter ≤ 0.08 μm from the pore size distribution curve of the entire diaphragm. The ratio of the integral area of ​​pores with a diameter ≥ 0.5 μm in the pore size distribution curve of the ceramic layer to the total integral area of ​​the pore size distribution curve of the ceramic layer is the volume percentage of pores with a diameter ≥ 0.5 μm in the total volume of pores in the ceramic layer.

[0057] In one example, based on the total volume of pores in the ceramic layer, the volume ratio of pores with a diameter ≥ 0.5 μm is 30%-60%.

[0058] In one example, the coverage of the first pore on the surface of the ceramic layer is 10%-50% (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%). The coverage of the first pore on the surface of the ceramic layer represents the ratio of the sum of the projected areas of the first pores on the surface of the ceramic layer onto the substrate surface to the projected area of ​​the ceramic layer on the substrate surface. In the battery disclosed herein, the ceramic layer of the separator has a porous structure. By controlling the coverage of pores with a diameter ≥ 0.5 μm in the porous structure, the porosity of the separator can be increased, thereby improving the ion transport capacity of the separator and thus improving the rate performance and fast-charge cycle performance of the battery. When the coverage of pores with a diameter ≥ 0.5 μm on the surface of the ceramic layer is less than 10%, the ion permeability of the separator is low, and the fast-charge cycle and rate performance of the battery cannot be effectively improved; when the coverage of pores with a diameter ≥ 0.5 μm on the surface of the ceramic layer is higher than 50%, the heat resistance of the separator is low, and the safety performance of the battery cannot be guaranteed.

[0059] In one example, the coverage of the first pore on the ceramic layer surface is 20%-40%.

[0060] In this disclosure, the coverage rate of the first pore on the ceramic layer surface can be tested by the following method: for example, by using a scanning electron microscope (SEM). Specifically, a microscopic image of the ceramic layer surface is obtained using SEM. A region with an area of ​​100 μm² (e.g., 100 μm × 100 μm) is randomly divided in the image. This area is then divided into uniform squares of 100 × 100. If the coverage area of ​​the squares with pores ≥ 0.5 μm in diameter exceeds half of the square area, it indicates that the square is occupied by pores ≥ 0.5 μm in diameter. Otherwise, it indicates that the square is not occupied by pores ≥ 0.5 μm in diameter. The number of squares occupied by pores ≥ 0.5 μm in diameter is counted, and the total number of squares occupied by pores ≥ 0.5 μm in diameter is recorded as X. Then, the coverage rate = (X / 100 × 100) × 100%. The above operation is repeated 5 times, and the average value of the 5 times is the coverage rate of pores with a diameter ≥ 0.5 μm on the ceramic layer surface.

[0061] In one example, within an arbitrarily selected 100μm × 100μm range on the surface of the ceramic layer, the number of pores with a diameter ≥ 0.5μm is 10 to 800 (e.g., 10, 50, 100, 200, 300, 400, 500, 600, 700, or 800). Controlling the number of pores with a diameter ≥ 0.5μm within this range ensures that the coverage of pores with a diameter ≥ 0.5μm on the ceramic layer surface is 10%-50%, thereby improving the porosity of the separator and enhancing the battery's rate performance and fast-charge cycle performance. When the number of pores with a diameter ≥ 0.5 μm is less than 10 within an arbitrarily selected 100 μm × 100 μm area on the surface of the ceramic layer, the coverage rate of pores with a diameter ≥ 0.5 μm on the surface of the ceramic layer is less than 10%, the ion permeability of the separator is low, and the fast charging cycle and rate performance of the battery cannot be effectively improved; when the number of pores with a diameter ≥ 0.5 μm is more than 800 within an arbitrarily selected 100 μm × 100 μm area on the surface of the ceramic layer, the coverage rate of pores with a diameter ≥ 0.5 μm on the surface of the ceramic layer is more than 50%, the heat resistance of the separator is low, and the safety performance of the battery cannot be guaranteed.

[0062] In one example, the number of pores with a diameter ≥ 0.5 μm is 50 to 500 within an arbitrarily selected 100 μm × 100 μm range on the surface of the ceramic layer.

[0063] According to one specific embodiment, the coverage rate of pores with a diameter ≥ 0.5 μm on the surface of the ceramic layer is 20%-40%, and the number of pores with a diameter ≥ 0.5 μm is 50-500 within an arbitrarily selected 100 μm × 100 μm range on the surface of the ceramic layer.

[0064] In one example, the ceramic layer covers 50%-100% of the substrate surface (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%). Controlling the coverage of the ceramic layer on the substrate surface within this range enables the separator to have good thermal stability, thereby providing the battery with excellent safety performance. When the coverage of the ceramic layer on the substrate surface is less than 50%, the separator has poor thermal stability, thus reducing the battery's safety performance.

[0065] In one example, the ceramic layer covers 60%-90% of the surface of the substrate.

[0066] In this disclosure, the coverage of the ceramic layer on the substrate surface represents the ratio of the orthographic projection area of ​​the ceramic layer on the substrate surface to the surface area of ​​the substrate. Since the ceramic layer has a porous structure, as shown in Figure 1, some of the pores in the porous structure expose the substrate, while others do not. The orthographic projection area of ​​the ceramic layer on the substrate surface will subtract the area of ​​the exposed pores from the substrate surface.

[0067] In one specific embodiment, the inorganic particles are selected from one or more of alumina, boehmite, magnesium oxide, magnesium hydroxide, barium sulfate, barium titanate, zinc oxide, calcium oxide, silicon dioxide, silicon carbide, and boron nitride.

[0068] For example, the ceramic layer further includes excipients, which include at least one of a dispersant, a membrane binder, and a thickener.

[0069] In one example, the dispersant is selected from one or more of fluoroalkyl methoxy alcohol ethers, polyoxyethylene alkylamines, sodium butylnaphthalene sulfonate, sodium arylnaphthalene sulfonate, sodium dodecylbenzene sulfonate, sodium alkyl sulfate, sodium polyacrylate, sodium polymethphosphate, sodium silicate, and sodium dodecyl sulfate.

[0070] In one example, the membrane adhesive includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyimide, polyacrylonitrile, poly(meth)acrylate, aramid resin, poly(meth)acrylic acid, styrene-butadiene rubber (SBR), polyvinyl alcohol, polyvinyl acetate, and carboxyethyl cellulose.

[0071] In one example, the diaphragm adhesive is selected from one or more of styrene-butadiene rubber, polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene, polyvinylidene fluoride-tetrafluoroethylene, polyvinylidene fluoride-hexafluoroethylene, polyvinylidene fluoride-hexafluoropropylene, styrene-acrylic emulsion, ethyl polyacrylate, polymethyl methacrylate, polybutyl methacrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, and polyurethane.

[0072] In one example, the thickener includes one or more of methylcellulose (CMC), sodium carboxymethylcellulose (CMC-Na), and lithium carboxymethylcellulose (CMC-Li).

[0073] In one example, the thickener is selected from one or both of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose.

[0074] In one specific embodiment, the thickness of the ceramic layer is 1μm-5μm (e.g., 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, or 5μm). Here, the thickness of the ceramic layer refers to the thickness of the ceramic layer on one surface of the substrate. This embodiment, by adjusting the thickness of the ceramic layer, ensures, on the one hand, that the separator has good heat resistance, thereby giving the battery good safety performance; on the other hand, it ensures that the separator is not too thick, thus affecting the battery's volumetric energy density.

[0075] In one specific embodiment, the thickness of the ceramic layer is 1.5μm-4μm.

[0076] In one specific embodiment, the thickness of the ceramic layer is 1.5μm-3μm.

[0077] In one specific embodiment, the areal density of the ceramic layer is 1 g / m³. 2 -10g / m 2 (For example, 1g / m 2 2g / m 2 3g / m 2 4g / m 2 5g / m 2 6g / m 2 7g / m 2 8g / m 2 9g / m 2 or 10g / m 2The areal density of the ceramic layer is the areal density of one side of the ceramic layer, referring to the areal density of the ceramic layer on one surface of the substrate. For example, the areal density of the ceramic layer means that when there is a ceramic layer on one side of the substrate, the areal density of the ceramic layer is the areal density of that side (i.e., the side with the ceramic layer); when there are ceramic layers on both sides of the substrate, the areal densities of the ceramic layers on both sides of the separator are the same, and the areal density of the ceramic layer is the areal density of either side. This embodiment, by adjusting the areal density of the ceramic layer, ensures that the separator has good isolation properties, thereby giving the battery good safety performance; on the other hand, it ensures that the separator is not too heavy and affects the battery's weight energy density.

[0078] For example, the surface density of the ceramic layer can be tested by a method including the following process: peeling a ceramic layer sample of a unit area from the diaphragm, weighing the total mass of the sample using a high-precision balance, and dividing the total mass of the sample by the area to obtain the surface density of the ceramic layer.

[0079] In one example, the areal density of the ceramic layer is 1 g / m³. 2 -8g / m 2 (For example, 1g / m 2 2g / m 2 3g / m 2 4g / m 2 5g / m 2 6g / m 2 7g / m 2 or g / m 2 ).

[0080] In one example, the areal density of the ceramic layer is 1.5 g / m³. 2 -6g / m 2 .

[0081] In one specific embodiment, the ceramic layer further includes a second pore with a diameter of less than 0.5 μm. This second pore is a micropore formed by the accumulation of ceramic particles themselves.

[0082] In one example, the ceramic layer of the diaphragm further includes a first polymer, which is composed of adhesive particles, thus giving the ceramic layer adhesive properties. The first polymer is indicated by the black dashed circles in Figures 1 and 9. However, these black dashed circles only indicate a portion of the first polymer in Figures 1 and 9 and do not represent all of the first polymer in Figures 1 and 9.

[0083] In one example, within an arbitrarily selected 100μm × 100μm range on the surface of the ceramic layer, the number of the first polymer is 0-600 (e.g., 0, 10, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, or 600). When the number of the first polymer is 0, it indicates that the first polymer is absent from the ceramic layer. Even without the first polymer, the ceramic layer still possesses adhesive properties. Controlling the number of the first polymer within the arbitrarily selected 100μm × 100μm range on the surface of the ceramic layer allows the separator to have good ion permeability, thereby improving the battery's fast-charge cycle and rate performance. When the number of the first polymer exceeds 600 within the arbitrarily selected 100μm × 100μm range on the surface of the ceramic layer, the separator exhibits poor thermal stability, thereby reducing the battery's safety performance.

[0084] In one example, the number of the first polymers is 10 to 600 within an arbitrarily selected 100 μm × 100 μm range on the surface of the ceramic layer.

[0085] In one example, the number of the first polymer particles within an arbitrarily selected 100μm × 100μm range on the surface of the ceramic layer is 10 to 500 (e.g., 10, 50, 100, 200, 300, 400, or 500). By controlling the number of the first polymer particles within an arbitrarily selected 100μm × 100μm range on the surface of the ceramic layer to be 10 to 500, the interface between the separator and the positive and negative electrode active layers can be made more stable, thereby improving the long-cycle performance of the battery. Moreover, since the first polymer is an adhesive particle, the separator of this disclosure does not require a separate adhesive coating layer, reducing the adverse effects of the adhesive coating layer on the battery's fast-charging performance. Therefore, the separator of this disclosure has the advantages of low self-discharge and high safety, as well as high long-cycle performance and high fast-charging performance.

[0086] According to one specific embodiment, the ceramic layer comprises inorganic particles and a first polymer. The ceramic layer has a porous structure, comprising pores with a diameter ≥ 0.5 μm. Within an arbitrarily selected 100 μm × 100 μm range on the surface of the ceramic layer, the number of pores with a diameter ≥ 0.5 μm is 10-800, and the number of the first polymer particles is 10-500. The diaphragm satisfies the following relationship: 1 < D1 / D2 < 20, where D1 is the average diameter of the pores with a diameter ≥ 0.5 μm in the ceramic layer, in μm; and D2 is the average particle size of the inorganic particles, in μm. As shown in Figures 3 and 4, the ceramic layer comprises inorganic particles 23 and a first polymer 21, the ceramic layer has a porous structure, and 22 represents the pores of the ceramic layer.

[0087] In one example, the number of the first polymers is 30 to 500 within an arbitrarily selected 100 μm × 100 μm range on the surface of the ceramic layer.

[0088] In one example, the number of the first polymers is 30 to 300 within an arbitrarily selected 100 μm × 100 μm range on the surface of the ceramic layer.

[0089] According to a specific embodiment, 2≤D1 / D2≤15, D1 is 2μm-8μm, D2 is 0.5μm-2μm, and within an arbitrarily selected range of 100μm×100μm on the surface of the ceramic layer, the number of pores with a diameter ≥0.5μm is 50-500 and the number of the first polymer is 30-300.

[0090] In one example, the diaphragm satisfies the following relationship: 2≤D4 / H1≤5 (e.g., 2, 2.5, 3, 3.5, 4, 4.5 or 5), where D4 is the average particle size of the first polymer in the ceramic layer in μm; and H1 is the thickness of the ceramic layer in μm.

[0091] Controlling D4 / H1 within the aforementioned range allows for a more suitable size of the first polymer protruding from the ceramic layer surface. On one hand, this enables the ceramic layer to have better adhesion, thereby achieving higher interfacial stability between the separator and the positive and negative active layers, further improving the battery's long-cycle performance. On the other hand, it allows for a more suitable spacing between the ceramic layer and the positive and negative active layers, resulting in a good interfacial distance between the separator and the positive and negative active layers, thus improving the battery's fast-charging long-cycle performance. When D4 / H1 < 2, the average particle size of the first polymer is too small, resulting in insufficient contact between the first polymer and the positive and negative active layers. This affects the interfacial adhesion between the separator and the positive and negative active layers, and cannot effectively improve the fast-charging and long-cycle performance of the battery. When D4 / H1 > 5, the average particle size of the first polymer is too large, resulting in an excessively large protrusion of the first polymer on the ceramic layer surface. This leads to an excessively large distance between the separator and the positive and negative active layers, affecting the interfacial stability between the separator and the positive and negative active layers, and cannot effectively improve the fast-charging and long-cycle performance of the battery.

[0092] It is understandable that the thickness of the ceramic layer cannot be perfectly uniform during the membrane fabrication process. Therefore, the thickness H1 of the ceramic layer described in this disclosure is the maximum value of the ceramic layer thickness. The thickness of the ceramic layer can be obtained through SEM testing.

[0093] In one instance, D4 ​​is 2μm-10μm (e.g., 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm or 10μm).

[0094] In one instance, D4 ​​is 3μm-8μm.

[0095] In one instance, D4 ​​is 3μm-6μm.

[0096] According to one specific embodiment, D4 is 3μm-8μm, H1 is 1.5μm-4μm, and the diaphragm satisfies the following relationship: 2≤D4 / H1≤5.

[0097] According to one specific embodiment, D4 is 3μm-6μm, H1 is 1.5μm-3μm, and the diaphragm satisfies the following relationship: 2≤D4 / H1≤5.

[0098] According to one specific embodiment, D4 is 3μm-8μm, H1 is 1.5μm-4μm, D1 is 1μm-8μm, and D2 is 0.5μm-2.5μm. The diaphragm satisfies the following relationships: 2≤D4 / H1≤5 and 2≤D1 / D2≤16.

[0099] According to one specific embodiment, D1 is 2μm-8μm, D2 is 0.5μm-2μm, D4 is 3μm-6μm, and H1 is 1.5μm-3μm. The diaphragm satisfies the following relationships: 2≤D1 / D2≤15 and 2≤D4 / H1≤5.

[0100] In one example, the coverage N1 of the first polymer in the ceramic layer on the surface of the ceramic layer is 0%-50% (e.g., 0%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%).

[0101] In one example, the coverage of the first polymer on the surface of the ceramic layer is 5%-50%.

[0102] In one example, the coverage N1 of the first polymer in the ceramic layer on the surface of the ceramic layer is 10%-40%.

[0103] In one example, the coverage of the first polymer on the surface of the ceramic layer is 5%-25% (e.g., 5%, 10%, 15%, 20%, or 25%). Controlling the coverage of the first polymer on the surface of the ceramic layer within this range allows the ceramic layer to have better adhesion, thereby resulting in higher interfacial stability between the separator and the positive and negative active layers, further improving the battery's long-cycle performance. Furthermore, it allows the spacing between the ceramic layer and the positive and negative active layers to maintain a suitable size, thus ensuring good interfacial spacing between the separator and the positive and negative active layers, thereby improving the battery's fast-charging long-cycle performance. When the coverage of the first polymer on the surface of the ceramic layer is less than 5%, the ceramic layer does not have enough first polymer to maintain good contact with the positive and negative active layers, thus affecting the interfacial adhesion between the separator and the positive and negative active layers, and failing to effectively improve the fast-charging and long-cycle performance of the battery. When the coverage of the first polymer on the surface of the ceramic layer is greater than 25%, the excessive number of first polymer particles and the excessively high coverage affect the ion conduction performance, and fail to effectively improve the fast-charging and long-cycle performance of the battery.

[0104] In one example, the coverage of the first polymer on the surface of the ceramic layer is 8%-20%.

[0105] In this disclosure, the coverage of the first polymer on the surface of the ceramic layer represents the ratio of the projected area of ​​the first polymer on the surface of the ceramic layer to the projected area of ​​the ceramic layer on the surface of the substrate.

[0106] In this disclosure, the coverage of the first polymer on the surface of the ceramic layer can be tested by the following method: for example, by scanning electron microscopy (SEM), specifically: using SEM to obtain a microscopic image of the surface of the ceramic layer, and randomly dividing the image into areas with a size of 100 μm. 2 The area (e.g., 100μm × 100μm) is divided into uniform 100×100 squares. If the area covered by the first polymer in a square exceeds half of the square's area, it means that the square is occupied by the first polymer; otherwise, it means that the square is not occupied by the first polymer. The number of squares occupied by the first polymer is counted, and the total number of squares occupied by the first polymer is recorded as X. The coverage rate is then calculated as (X / 100*100)*100%. This operation is repeated 5 times, and the average of the 5 counts is the coverage rate of the first polymer on the ceramic layer surface.

[0107] In one example, within an arbitrarily selected 100μm × 100μm range on the surface of the ceramic layer, the number of the first polymer is 30 to 300, and the coverage of the first polymer on the surface of the ceramic layer is 8% to 20%.

[0108] In one example, based on the total volume of pores in the ceramic layer, the volume ratio of pores with a diameter ≥ 0.5 μm is 30%-60%, and the coverage of the first polymer on the surface of the ceramic layer is 8%-20%.

[0109] In one example, the weight content W2 of the first polymer is 0-15% (e.g., 0, 0.1%, 0.5%, 1%, 3%, 5%, 8%, 10%, 13%, or 15%) based on the total weight of the ceramic layer. When the weight content of the first polymer in the ceramic layer is 0, it means that the ceramic layer does not contain the first polymer.

[0110] In one instance, the weight content of the first polymer is 1%-18% based on the total weight of the ceramic layer.

[0111] In one example, the weight content W2 of the first polymer is 5%-12% based on the total weight of the ceramic layer.

[0112] In one example, the ceramic layer further includes a diaphragm binder and a thickener.

[0113] In one example, based on the total weight of the ceramic layer, the inorganic particles have a weight content of 75%-98% (e.g., 75%, 80%, 85%, 90%, 95%, or 98%), the first polymer has a weight content of 1%-18% (e.g., 1%, 5%, 10%, 15%, or 18%), the membrane binder has a weight content of 0.5%-8% (e.g., 0.5%, 1%, 3%, 5%, or 8%), and the thickener has a weight content of 0.4%-4% (e.g., 0.4%, 1%, 2%, 3%, or 4%).

[0114] In one example, based on the total weight of the ceramic layer, the inorganic particles have a weight content of 85%-98% (e.g., 85%, 88%, 90%, 92%, 95%, or 98%), the thickener has a weight content of 1%-5% (e.g., 1%, 2%, 3%, 4%, or 5%), and the membrane binder has a weight content of 1%-10% (e.g., 1%, 3%, 5%, 8%, or 10%).

[0115] In one example, based on the total weight of the ceramic layer, the inorganic particles account for 86%-93% by weight, the thickener accounts for 1.5%-4% by weight, and the membrane binder accounts for 2%-6% by weight.

[0116] In one example, the first polymer includes a first monomer, a second monomer, and optionally (“optionally” means that it may or may not be present) a third monomer. The first polymer has adhesive properties and can replace the adhesive layer to improve the stability between the separator and the positive and negative electrode active layers.

[0117] In one example, the first monomer includes one or more of acrylonitrile monomers, styrene monomers, and acrylate monomers.

[0118] In one example, the acrylate monomers include one or more of methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, lauryl acrylate, and octadecyl acrylate.

[0119] In one example, the styrene monomer includes one or more of styrene, methylstyrene, tristyrene, and 4-methylstyrene.

[0120] In one example, the acrylonitrile monomer includes one or more of acrylonitrile, triphenylacrylonitrile, 3-cyclopentylacrylonitrile, and 3,3-(diphenyl)acrylonitrile.

[0121] In one example, the second monomer comprises one or more of dimethacrylamide, diethylacrylamide, divinylbenzene, trimethylolpropane triacrylate, ethylene glycol dimethacrylate, ethylene glycol diacrylate, triethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate.

[0122] In one example, the third monomer includes one or more of acrylic acid, butadiene, methacrylic acid, acrylamide, hydroxymethylacrylamide, hydroxyethylacrylamide, isopropylacrylamide, glycidyl (meth)acrylate, and allyl glycidyl ester.

[0123] In one example, the peeling force of the ceramic layer is ≥25 N / m.

[0124] In this disclosure, the peel force can be obtained by testing as follows: a 2.5 cm wide 3M tape is pressed onto the diaphragm with a 1 kg block for 1 min. The prepared sample diaphragm and 3M tape are placed at a 180-degree angle and tested on a universal tensile testing machine at a speed of 100 mm / min and a test displacement of 50 mm. The minimum peel force that enables the diaphragm and 3M tape to achieve a displacement of 50 mm is recorded as the peel force N (unit N / m) between the ceramic layer and the substrate.

[0125] This disclosure provides a method for preparing the above-mentioned diaphragm, comprising the following steps:

[0126] Polymer particles are added to a first slurry comprising inorganic particles, a membrane binder, and a first solvent, and the mixture is then mixed to obtain a second slurry comprising the polymer particles.

[0127] The second slurry is coated on at least one surface of the substrate and dried to form a ceramic layer, thereby obtaining a diaphragm precursor including a ceramic layer;

[0128] The ceramic layer is immersed in a second solvent until the polymer particles dissolve in the second solvent. Solid-liquid separation and drying are then performed to obtain the diaphragm.

[0129] The polymer particles have a Dv50 of D7, which satisfies the following conditions: 0.5μm≤D7≤10μm, 1<D7 / D3<20.

[0130] In the above preparation method, a second slurry including soluble polymer particles is first coated on the surface of the polymer layer. The polymer particles form occupants on the surface of the polymer layer. Then, the polymer particles are dissolved using a second solvent, and the space occupied by the polymer particles is vacated. After drying, a stable first pore is formed, while a second pore with a smaller pore size is formed between the inorganic particles.

[0131] It is understood that the main difference between the aforementioned membrane precursor and the final membrane is that it does not contain a first pore; the aforementioned first solvent is a solvent that does not dissolve the polymer particles, and the second solvent is a solvent that can dissolve the polymer particles. Exemplarily, the polymer particles are polymers selected from at least one monomer selected from acrylic acid, acrylate, styrene, and acrylonitrile, such as polyacrylate, polymethyl methacrylate, or a copolymer of polymethyl methacrylate and acrylonitrile. The first solvent is water, and the second solvent includes one or more of N-methylpyrrolidone (NMP), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and dimethylacetamide (DMAC).

[0132] In one specific embodiment, the process further includes accelerating the dissolution rate of the polymer particles by heat treatment. More specifically, the polymer particles are soaked in the second solvent at 80°C-100°C for 2-10 minutes to change the polymer particles from particulate to non-particulate and completely dissolve them in the second solvent. The membrane precursor is then washed with water and dried at 40-80°C to obtain the membrane.

[0133] The mass ratio of each component of the first slurry is not particularly limited in this disclosure. Those skilled in the art can continue to adjust it according to the required thickness and strength of the porous ceramic layer. In one specific embodiment, the ratio of the inorganic particles, polymer particles, membrane binder, dispersant, thickener and first solvent in the first slurry is 27.6:3:1.2:0.6:0.6:67 by mass.

[0134] For example, the diaphragm adhesive is selected from one or more of styrene-butadiene rubber, polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene, polyvinylidene fluoride-tetrafluoroethylene, polyvinylidene fluoride-hexafluoroethylene, polyvinylidene fluoride-hexafluoropropylene, styrene-acrylic emulsion, ethyl polyacrylate, polymethyl methacrylate, polybutyl methacrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, and polyurethane;

[0135] In one example, the first slurry may further include a dispersant and a thickener;

[0136] In one example, the dispersant is selected from one or more of fluoroalkyl methoxy alcohol ethers, polyoxyethylene alkylamines, sodium butylnaphthalene sulfonate, sodium arylnaphthalene sulfonate, sodium dodecylbenzene sulfonate, sodium alkyl sulfate, sodium polyacrylate, sodium polymethphosphate, sodium silicate, and sodium dodecyl sulfate.

[0137] In one example, the thickener is selected from one or both of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose.

[0138] To further improve the porosity of the porous ceramic layer, in one specific embodiment, the weight ratio of the polymer particles to the inorganic particles is (1-20):(80-99) (e.g., 1:99, 3:97, 5:95, 8:92, 10:90, 13:87, 15:85, 18:82 or 20:80).

[0139] This disclosure provides another method for preparing the aforementioned diaphragm, wherein the ceramic layer comprises inorganic particles and a first polymer, specifically comprising the following steps: mixing inorganic particles, water or deionized water, a thickener, and a diaphragm binder to prepare an aqueous slurry; adding an initial first polymer and a second polymer to the aqueous slurry to prepare a ceramic slurry; and coating the ceramic slurry onto one or both surfaces of a substrate to obtain an initial diaphragm. The initial diaphragm comprises a substrate and a ceramic layer located on one or both surfaces of the substrate, wherein the ceramic layer comprises inorganic particles, an initial first polymer, and a second polymer.

[0140] The initial separator is assembled with the positive electrode, negative electrode, and electrolyte to form a battery. The battery is then hot-pressed (hot-pressing conditions: hot-pressing temperature is 60℃-90℃ (e.g., 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, or 90℃), hot-pressing pressure is 0.1MPa-1.5MPa (e.g., 0.1MPa, 0.3MPa, 0.5MPa, 0.8MPa, 1MPa, 1.3MPa, or 1.5MPa), and hot-pressing time is 10min-60min (10min, 20min, 30min, 40min, 50min, or 60min)). After hot-pressing, since the initial first polymer partially dissolves and the second polymer completely dissolves, the ceramic layer of the separator contains the first polymer but not the second polymer, and the first polymer present in the ceramic layer is the partially undissolved initial first polymer. Partially dissolved initial first polymer and completely dissolved second polymer form numerous pores in the middle and surface of the ceramic layer, thus obtaining the separator with numerous pores as described in this disclosure. It is understood that the initial first polymer is of the same type as the first polymer in the ceramic layer, but the average particle size of the initial first polymer differs from that of the first polymer. In the battery fabrication process, hot pressing is an essential step, also known in the art as formation.

[0141] In one example, the initial first polymer includes a first monomer, a second monomer, and optionally (“optionally” means that it may or may not be present) a third monomer.

[0142] In one example, the second polymer comprises a fourth monomer and a fifth monomer.

[0143] In one example, the fourth monomer includes one or more of acrylonitrile monomers, styrene monomers, and acrylate monomers.

[0144] In one example, the acrylate monomers include one or more of methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, lauryl acrylate, and octadecyl acrylate.

[0145] In one example, the styrene monomer includes one or more of styrene, methylstyrene, tristyrene, and 4-methylstyrene.

[0146] In one example, the acrylonitrile monomer includes one or more of acrylonitrile, triphenylacrylonitrile, 3-cyclopentylacrylonitrile, and 3,3-(diphenyl)acrylonitrile.

[0147] In one example, the fifth monomer includes one or more of acrylic acid, butadiene, methacrylic acid, acrylamide, hydroxymethylacrylamide, hydroxyethylacrylamide, isopropylacrylamide, glycidyl (meth)acrylate, and allyl glycidyl ester.

[0148] In one example, the weight ratio of the inorganic particles, the thickener, and the membrane binder is (85%-98%):(1%-5%):(1%-10%).

[0149] In one example, the weight ratio of the initial first polymer, the second polymer, and the inorganic particles is (1%-15%):(1%-15%):(98%-70%). It is understood that the weight content of the first polymer can range from 1% to 15% (e.g., 1%, 5%, 10%, or 155%), the weight content of the second polymer can range from 1% to 15% (e.g., 1%, 5%, 10%, or 155%), and the weight content of the inorganic particles can range from 98% to 70% (e.g., 98%, 95%, 90%, 85%, 80%, 75%, or 70%).

[0150] In one example, the ratio of the weight of the initial first polymer, the weight of the second polymer, and the weight of the inorganic particles is (0%-15%):(2%-30%):(98%-70%). It is understood that the weight content of the initial first polymer can range from 0% to 15% (e.g., 0%, 0.1%, 0.5%, 1%, 3%, 5%, 8%, 10%, 13%, or 15%), the weight content of the second polymer can range from 2% to 30% (e.g., 2%, 5%, 10%, 15%, 20%, 25%, or 30%), and the weight content of the inorganic particles can range from 98% to 70% (e.g., 98%, 95%, 90%, 85%, 80%, 75%, or 70%), but the sum of the weight content of the polymer and the weight content of the inorganic particles must be 100%. When the initial weight content of the first polymer is 0%, it means that the first polymer does not exist.

[0151] In one example, the average particle size of the initial first polymer is 2 μm-10 μm (e.g., 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm).

[0152] In one example, the average particle size of the initial first polymer is 3 μm-6 μm.

[0153] In one example, the average particle size of the second polymer is 0.5 μm to 5 μm (e.g., 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm).

[0154] In one example, the average particle size of the second polymer is 1 μm-4 μm.

[0155] The second aspect of this disclosure provides a battery, the battery including a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive electrode and the negative electrode, the separator being the separator described in the first aspect of this disclosure.

[0156] Because the battery disclosed herein includes the separator described in the first aspect, the battery's rate performance, fast charging performance, and long cycle performance are improved.

[0157] In one example, the battery is a lithium-ion rechargeable battery.

[0158] In one example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, which is silicon material. The average particle size D5 of the silicon material is 1μm-10μm (e.g., 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, or 10μm). The battery satisfies the following relationship: 0.5≤D5 / D1≤5 (e.g., 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5). Wherein, D1 is the average diameter of the first pore of the ceramic layer, in μm.

[0159] In one example, the ceramic layer has a porous structure comprising pores with a diameter ≥ 0.5 μm. The coverage of pores with a diameter ≥ 0.5 μm on the surface of the ceramic layer is 10%-50%. The average particle size D5 of the silicon material is 1 μm-10 μm. The battery satisfies the following relationship: 0.5 ≤ D5 / D1 ≤ 5. Wherein, D1 is the average diameter of the first pore in the ceramic layer, in μm. The ceramic layer of the separator in this battery has a porous structure. By controlling the coverage of pores with a diameter ≥ 0.5 μm in the porous structure, the porosity of the separator can be increased, thereby improving the ion transport capacity of the separator and thus improving the rate performance and fast charge cycle performance of the battery. At the same time, by controlling the average particle size of the silicon material and 0.5 ≤ D5 / D2 ≤ 5 (e.g., 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5), the size of the silicon particles can be matched with the large pores (pores with a diameter ≥ 0.5 μm) in the ceramic layer of the separator. This allows the separator to provide a certain expansion space for the volume expansion of silicon particles, reducing the expansion rate of the battery, improving the structural stability of the negative electrode active material layer, and thus improving the rate performance and fast charge performance of the battery. In addition, it also enables the metal ion complex to be rapidly and orderly inserted and extracted on the negative electrode side during rapid charging and discharging, thereby improving the fast charge cycle performance of the battery. Furthermore, the ceramic layer of the separator disclosed herein has adhesive properties, which can replace the adhesive layer to improve the stability between the separator and the positive and negative active layers, thereby improving the specific energy of the battery and avoiding the adverse effects of the adhesive layer on the fast charging performance of the battery.

[0160] When D1 is below 1μm, the average particle size of the silicon material is too small, resulting in an excessively large specific surface area of ​​the silicon material. This leads to excessive side reactions between the negative electrode active material and the electrolyte, thus affecting the long-cycle performance of the battery. When D1 is above 10μm, the average particle size of the silicon material is too large, resulting in an excessively small specific surface area of ​​the silicon material. This results in an insufficient surface area of ​​the negative electrode active material to provide enough channels for charging and discharging, thus affecting the rate performance of the battery.

[0161] When D5 / D1 < 0.5, on the one hand, the average particle size of the silicon material is too small, resulting in an excessively large specific surface area of ​​the silicon material. This leads to excessive side reactions between the negative electrode active material and the electrolyte, thus affecting the long-cycle performance of the battery. On the other hand, the average diameter of the pores with a diameter ≥ 0.5 μm in the separator ceramic layer is too large, resulting in poor heat resistance of the separator, thus affecting the battery safety performance. When D5 / D1 > 5, the ceramic layer of the separator does not have sufficient porous areas to provide space for the expansion of the silicon material, resulting in excessive battery expansion and affecting the fast-charging cycle performance of the battery.

[0162] In one example, the average particle size D5 of the silicon material is 2 μm-8 μm.

[0163] In this disclosure, the term "average particle size" refers to the average diameter of all particles in a system. The average particle size can be obtained by observing the surface of a ceramic layer at 50,000x magnification using an electrolytic radiometric scanning electron microscope (Hitachi, Ltd. S-3400N). The image size at this time is 2.5 μm × 1.8 μm. It should be noted that the pixel count is 1,280 pixels × 960 pixels, and the size of one pixel is 2 nm × 1.9 nm. For the average particle size, a square or rectangle with the smallest area completely surrounding a single particle is drawn on the obtained image; that is, a square or rectangle where the end of the particle is connected to the four sides of the square or rectangle. In the case of a square, the length of one side is taken as the particle size; in the case of a rectangle, the length of the longest side (major axis diameter) is taken as the particle size. For any 81 particles, their individual particle sizes are measured, and the average of these measurements is taken as the average particle size. It should be noted that when more than 81 particles are observed in the captured image, the average number of any 81 particle sizes in the image is taken as the average particle size. When no 81 particles are observed in the image, multiple images are captured, and the average number of a total of 81 particle sizes is taken as the average particle size.

[0164] In one example, the battery satisfies the following relationship: 1 ≤ D5 / D1 ≤ 4.

[0165] According to one specific implementation, D5 is 2μm-8μm, D1 is 1μm-8μm, and the battery satisfies the following relationship: 1≤D5 / D1≤4.

[0166] In one example, the silicon material includes at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy.

[0167] In one example, the silicon-carbon composite comprises Si / C.

[0168] In one example, the silicon oxide compound includes SiOx / C.

[0169] In one example, the battery satisfies the following relationship: 0.5 ≤ W3 / N1 ≤ 10 (e.g., 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10), where W3 is the weight content of the silicon material based on the total weight of the negative electrode active material, in %; and N1 is the coverage of the first polymer in the ceramic layer on the surface of the ceramic layer, in %. Controlling W3 / N1 within the above range can, on the one hand, increase the adhesion between the separator and the negative electrode, thereby achieving good interfacial stability between the separator and the negative electrode; on the other hand, it can enable the battery to have a high energy density, while maintaining the interfacial stability between the separator and the negative electrode during rapid charge and discharge, thus enabling the battery to have good cycle performance.

[0170] In this disclosure, the coverage of the first polymer in the ceramic layer on the surface of the ceramic layer is expressed as the ratio of the projected area of ​​the first polymer in the ceramic layer on the substrate surface to the projected area of ​​the ceramic layer on the substrate surface.

[0171] In this disclosure, the coverage of the first polymer on the surface of the ceramic layer can be tested by the following method: for example, by scanning electron microscopy (SEM). Specifically, a microscopic image of the surface of the ceramic layer is obtained using SEM. A region with an area of ​​100 μm² (e.g., 100 μm × 100 μm) is randomly divided in the image. This region is then divided into uniform squares of 100 × 100. If the area covered by the first polymer in a square exceeds half of the square area, it indicates that the square is occupied by the first polymer. Otherwise, it indicates that the square is not occupied by the first polymer. The number of squares occupied by the first polymer is counted, and the total number of squares occupied by the first polymer is recorded as X. Then, the coverage rate = (X / 100 * 100) * 100%. The above operation is repeated 5 times, and the average of the 5 times is the coverage rate of the first polymer on the surface of the ceramic layer.

[0172] In one instance, 1 ≤ W3 / N1 ≤ 8.

[0173] In one instance, N1 is 0%–50% (e.g., 0%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%).

[0174] In one instance, N1 ranges from 5% to 25%.

[0175] In one instance, N1 is 10%-20%.

[0176] In one instance, N1 ranges from 10% to 40%.

[0177] In one example, W3 is 1%-100% (e.g., 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%). When W3 is 100%, it indicates that the negative electrode active material is silicon.

[0178] In one instance, W3 ranges from 5% to 50%.

[0179] According to one specific implementation, N1 is 5%-20%, W3 is 5%-95%, and the battery satisfies the following relationship: 1≤W3 / N1≤8.

[0180] In one example, the negative electrode active material further includes a carbon-based material, which includes graphite and / or hard carbon.

[0181] In one example, the weight content of the carbon-based material is 0%-99% (e.g., 0%, 0.1%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 99%), based on the total weight of the negative electrode active material. When the weight content of the carbon-based material in the negative electrode active material is 0%, it indicates that there is no carbon-based material in the negative electrode active material.

[0182] In one example, the carbon-based material comprises 5%-95% by weight, based on the total weight of the negative electrode active material.

[0183] In one example, the negative electrode active material layer further includes a negative electrode conductive agent and a negative electrode binder.

[0184] In one example, the negative electrode conductive agent is one or more of conductive carbon black, carbon nanotubes, conductive graphite, and graphene.

[0185] In one example, the negative electrode binder is one or more of the following: polyvinylidene fluoride (PVDF), acrylic acid-modified PVDF, polyacrylate polymers, polytetrafluoroethylene, perfluorosulfonic acid ionomers, polyacrylonitrile, polyimide, styrene-butadiene rubber, and styrene-acrylic rubber.

[0186] In one example, based on the total weight of the negative electrode active layer, the weight content of the negative electrode active material is 90%-98% (e.g., 90%, 92%, 95%, or 98%), the weight content of the negative electrode conductive agent is 0%-5% (e.g., 0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, or 5%), and the weight content of the negative electrode binder is 1%-5% (e.g., 1%, 2%, 3%, 4%, or 5%). When the weight content of the negative electrode conductive agent in the negative electrode active material layer is 0%, it indicates that there is no negative electrode conductive agent in the negative electrode active material layer.

[0187] In one example, based on the total weight of the negative electrode active layer, the weight content of the negative electrode active material is 92%-97%, the weight content of the negative electrode conductive agent is 1%-4%, and the weight content of the negative electrode binder is 1.5%-4.5%.

[0188] In one example, the negative electrode active layer includes a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and a negative electrode thickener. The negative electrode active material can be one or more of the negative electrode active materials known in the art for use in batteries, such as carbon-based materials, silicon-based materials, tin-based materials, and titanium-based materials; specifically, it can be one or more of artificial graphite, natural graphite, soft carbon, hard carbon, elemental silicon, silicon oxides (e.g., SiOx / C), silicon-carbon composites (e.g., Si / C), silicon-nitrogen composites, silicon alloys, elemental tin, tin oxides, tin alloys, elemental titanium, titanium oxides, and titanium alloys. The negative electrode current collector can be a conventional negative electrode current collector in the art, such as copper foil. The mass fraction of the negative electrode active material in the negative electrode active layer is 92%-98%, the mass fraction of the negative electrode binder is 0.5%-3%, the mass fraction of the negative electrode conductive agent is 0.5%-2.5%, and the mass fraction of the negative electrode thickener is 0.5%-2.5%.

[0189] In one example, the negative electrode conductive agent includes one or more of conductive carbon black, carbon nanotubes (e.g., single-walled carbon nanotubes and multi-walled carbon nanotubes), conductive graphite, and graphene; the negative electrode binder includes one or more of polyvinylidene fluoride (PVDF), a copolymer of polyvinylidene fluoride and hexafluoropropylene, acrylic acid-modified PVDF, polyacrylate polymers, polytetrafluoroethylene, perfluorosulfonic acid ionomers, polyacrylonitrile, polyimide, sodium carboxymethyl cellulose (CMC-Na), styrene-acrylic rubber, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber (SBR); and the negative electrode thickener includes sodium carboxymethyl cellulose (CMC-Na), etc.

[0190] In one specific embodiment, the positive electrode sheet includes a positive current collector and a positive active layer located on at least one surface of the positive current collector, the positive active layer containing a positive active material, the positive active material satisfying the following formula 1: 0.1 < D1 / (10×D6) < 1 Formula 1;

[0191] Wherein, D6 is the Dv50 of the positive electrode active material.

[0192] In the above embodiments, by adjusting the relationship between the Dv50 of the positive electrode active material and the pore size of the first pore, the positive electrode active material can have a larger specific surface area, thereby providing more charging and discharging channels for the positive electrode sheet. In addition, if the pore size of the first pore and the Dv50 of the positive electrode active material satisfy the relationship shown in Equation 1 above, the Li+ ion conductivity of the separator can be further improved, and the Li ion transport efficiency can be enhanced. If D1 / (10×D6) is greater than 1, the particle size of the positive electrode active material is small, which may block the pores of the separator, resulting in obstructed Li ion transport and thus affecting the electrochemical performance of the battery. Conversely, if D1 / (10×D6) is less than 0.1, the particle size of the positive electrode active material is large, which may reduce the diffusion path of Li ions and thus reduce the power performance of the battery.

[0193] To ensure that the pores of the membrane are not blocked by the positive electrode active material, and at the same time to ensure that the Li ion transport rate is within a high range, in one specific embodiment, the D6 satisfies: 0.3μm≤D6≤2μm (e.g., 0.3μm, 0.5μm, 0.8μm, 1μm, 1.3μm, 1.5μm, 1.8μm or 2μm).

[0194] Low bonding strength (low peel force) between positive electrode active materials can lead to voids and cracks inside the electrode, increasing the battery's internal resistance, reducing the contact area of ​​effective active materials, and hindering the battery's thermal cycling. Therefore, in order to further ensure the thermal cycling stability of the battery, in one specific embodiment, the peel force between the positive electrode active materials is greater than 1 N / m.

[0195] It is understood that the positive electrode sheet includes a positive current collector and a positive active layer located on at least one surface of the positive current collector, the positive active layer including the positive active material.

[0196] For example, the positive electrode active layer specifically includes the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder. The positive electrode active material can be selected from one or more of lithium nickel oxide, lithium titanate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide. The positive electrode current collector can be a conventional positive electrode current collector in the art, such as aluminum foil, etc. The mass fraction of the positive electrode active material in the positive electrode active layer is 94%-99% (e.g., 94%, 95%, 96%, 97%, 98%, or 99%), the mass fraction of the positive electrode binder is 0.5%-5% (e.g., 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%), and the mass fraction of the positive electrode conductive agent is 0.5%-3% (e.g., 0.5%, 1%, 1.5%, 2%, 2.5%, or 3%). The positive electrode binder is selected from one or more of polyvinylidene fluoride, polyimide, polyacrylic acid, polytetrafluoroethylene, perfluorosulfonic acid ionomer, polyacrylonitrile, acrylic acid modified PVDF, polyacrylate polymers, polyimide, styrene-butadiene rubber, and styrene-acrylic rubber.

[0197] In one example, the positive electrode conductive agent includes one or more of conductive carbon black, carbon nanotubes, conductive graphite, and graphene, and the positive electrode binder includes one or more of polyvinylidene fluoride (PVDF), a copolymer of polyvinylidene fluoride and hexafluoropropylene, acrylic acid-modified PVDF, polyacrylate polymers, polytetrafluoroethylene, perfluorosulfonic acid ionomers, polyimide, styrene-acrylic rubber, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber (SBR).

[0198] In one example, the positive electrode active material is selected from lithium iron phosphate or lithium iron phosphate that has been doped with two or more elements from Al, Mg, Mn, Cr, Ti, and Zr.

[0199] In one example, based on the total weight of the positive electrode active layer, the weight content of the positive electrode active material is 90%-98% (e.g., 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or 98%), the weight content of the positive electrode conductive agent is 1%-5% (e.g., 1%, 2%, 3%, 4%, or 5%), and the weight content of the positive electrode binder is 1%-5% (e.g., 1%, 2%, 3%, 4%, or 5%).

[0200] In one example, based on the total weight of the positive electrode active layer, the weight content of the positive electrode active material is 92%-97%, the weight content of the positive electrode conductive agent is 1.5%-4%, and the weight content of the positive electrode binder is 1.5%-4%.

[0201] In one instance, the positive electrode conductive agent and the negative electrode conductive agent may be the same or different.

[0202] In one instance, the positive electrode binder and the negative electrode binder may be the same or different.

[0203] For example, the magnitude of the peeling force between the positive electrode active materials can be obtained by a method including the following steps:

[0204] The pressure-sensitive tape is bonded to the stainless steel plate, and then the positive electrode active layer side of the positive electrode sheet is bonded to the pressure-sensitive tape. The tensile testing machine clamps the negative electrode sheet and peels it off at 180°. The required peeling force is recorded as FN / m. If F is greater than or equal to 1N / m, the thickness of the positive electrode active layer remaining on the current collector is observed. Otherwise, it is assumed that the peeling force between the positive electrode active materials is less than or equal to 1N / m. If the thickness of the remaining positive electrode active layer is greater than 1μm, it indicates that the peeling force between the positive electrode active materials in the positive electrode active layer is greater than the peeling force between the positive electrode active layer and the current collector. This indicates that the peeling force between the positive electrode active materials is greater than 1N / m.

[0205] Exemplarily, the battery further includes an electrolyte. This disclosure does not specifically limit the electrolyte; for example, an electrolyte comprising an organic solvent and an electrolyte salt can be used. The organic solvent, as a medium for transporting ions in the electrochemical reaction, can be any organic solvent known in the art for battery electrolytes, such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butenyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), and ethyl propionate. At least one of the following: ester (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE); the electrolyte salt, as the ion source, may be an electrolyte salt known in the art for use in battery electrolytes, such as: lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium difluorodioxalate phosphate, lithium tetrafluorooxalate phosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium perfluorobutyl sulfonate, and lithium fluorinated fatty acids.

[0206] In one specific embodiment, the organic solvent of the electrolyte is composed of EMC (10-70 parts), EA (10-70 parts), and EC (15-40 parts), and further includes lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate. The content of lithium bis(fluorosulfonyl)imide is 2-20 parts, preferably 3-9 parts; the concentration of lithium hexafluorophosphate is 0.3-1.8 mol / L, preferably 0.8-1.5 mol / L.

[0207] In one example, the electrolyte comprises an organic solvent.

[0208] In one example, the electrolyte comprises an organic solvent, which includes at least two of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), propyl propionate (PP), ethyl propionate (EP), and ethyl acetate (EA).

[0209] In one example, the organic solvent includes a first organic solvent and a second organic solvent.

[0210] In one example, the first organic solvent includes one or more of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), propyl propionate (PP), ethyl propionate (EP), and ethyl acetate (EA).

[0211] In one example, the second organic solvent is propylene carbonate (PC) and / or ethylene carbonate (EC).

[0212] In one example, the weight ratio of the first organic solvent to the second organic solvent is (0.05-20):1 (e.g., 0.05, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20). Controlling the weight ratio of the first organic solvent to the second organic solvent within this range allows the electrolyte to have suitable viscosity and good ionic conductivity, thereby giving the battery high long-cycle performance and superior fast-charging performance. When the weight ratio of the first organic solvent to the second organic solvent is less than 0.05:1, the content of the second organic solvent is too high, resulting in excessively high electrolyte viscosity and reduced fast-charging performance. When the weight ratio of the first organic solvent to the second organic solvent is greater than 20:1, the content of the first organic solvent is too high, resulting in low ionic conductivity and reduced long-cycle performance.

[0213] In one example, the weight ratio of the first organic solvent to the second organic solvent is (0.1-10):1.

[0214] In one example, the organic solvent includes ethyl methyl carbonate (EMC), ethyl acetate (EA), and ethylene carbonate (EC).

[0215] In one example, the weight ratio of ethyl methyl carbonate (EMC), ethyl acetate (EA), and ethylene carbonate (EC) in the organic solvent is (10%-70%):(10%-70%):(15%-40%). It is understood that the weight content of methyl ethyl carbonate in the organic solvent can be in the range of 10%-70% (e.g., 10%, 20%, 30%, 40%, 50%, 60%, or 70%), the weight content of ethyl acetate in the organic solvent can be in the range of 10%-70% (e.g., 10%, 20%, 30%, 40%, 50%, 60%, or 70%), and the weight content of ethylene carbonate in the organic solvent can be in the range of 15%-40% (e.g., 15%, 20%, 25%, 30%, 35%, or 40%). However, it is required that the sum of the weight contents of methyl ethyl carbonate, ethyl acetate, and ethylene carbonate in the organic solvent is 100%.

[0216] In one example, the organic solvent content is 70%-86% by weight (e.g., 70%, 73%, 75%, 78%, 80%, 85% or 86%) based on the total weight of the electrolyte.

[0217] In one example, the organic solvent content is 75%-81% by weight, based on the total weight of the electrolyte.

[0218] In one example, the organic solvent content is 64%-86% by weight (e.g., 64%, 65%, 70%, 75%, 80%, 85%, or 86%) based on the total weight of the electrolyte.

[0219] In one example, the organic solvent content is 70%-82% by weight, based on the total weight of the electrolyte.

[0220] In one example, the electrolyte further includes LiFSI and optionally additives.

[0221] In one example, the additive includes one or more of the following: fluoroethylene carbonate (FEC), 1,3-propanesulfonate lactone (PS), vinylene carbonate (VC), lithium difluorophosphate (LiPO2F2), lithium bis(oxalate borate) (LiBOB), lithium difluorooxalate borate (LiODFB), lithium difluorooxalate phosphate (LiODFP), lithium tetrafluoroborate (LiBF4), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0222] In one example, based on the total weight of the electrolyte, the weight content of LiFSI is 2%-20% (e.g., 2%, 5%, 10%, 15%, or 20%), and the weight content of the additive is 0%-10%. When the weight content of the additive in the electrolyte is 0%, it indicates that there is no additive in the electrolyte.

[0223] In one example, the LiFSI content is 3%-9% by weight and the additive content is 1%-8% by weight, based on the total weight of the electrolyte.

[0224] In one example, the electrolyte also includes a lithium salt.

[0225] In one example, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium perchlorate.

[0226] In one example, the lithium salt content is 12%-30% by weight (e.g., 12%, 15%, 18%, 20%, 22%, 25%, 28%, or 30%) based on the total weight of the electrolyte.

[0227] In one example, the lithium salt content is 15%-25% by weight, based on the total weight of the electrolyte.

[0228] In one example, the first polymer is immersed in a solvent at 60℃-90℃ for 2-10 minutes, and the solubility of the first polymer is ≤50% (e.g., 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 1%, 0.5%, 0.1%). Controlling the solubility of the first polymer within this range allows the ceramic layer to have better adhesion, thereby resulting in higher interfacial stability between the separator and the positive and negative active layers, further improving the battery's long-cycle performance. When the solubility of the first polymer is higher than 50%, after hot pressing, the amount of the first polymer retained in the ceramic layer is less, resulting in insufficient first polymer to maintain good contact with the positive and negative active layers, thus affecting the interfacial adhesion between the separator and the positive and negative active layers, and failing to effectively improve the battery's fast-charging long-cycle performance.

[0229] The solvent may be an organic solvent as described in this disclosure, or an electrolyte containing an organic solvent as described in this disclosure.

[0230] In one example, the first polymer was immersed in the solvent for 2 min to 10 min at 60°C to 90°C, and the solubility of the first polymer was 1% to 20%.

[0231] In this disclosure, the solubility can be obtained by the following method: taking EMC as the solvent, take a first polymer with a weight of M1, add it to an EMC beaker with a content of 20*M1, place the beaker in an oven at 80°C and let it stand for 10 minutes, take out the remaining first polymer, dry it, weigh it and record the weight of the remaining first polymer as M2, then the solubility of the first polymer in the solvent EMC is (M1-M2) / M1*100%.

[0232] In one example, the second polymer was immersed in a solvent at 60°C-90°C for 2-10 minutes, during which time the second polymer completely dissolved. Due to this property of the second polymer, it completely dissolved during the battery hot-pressing process, forming a large number of pores in the ceramic layer of the separator.

[0233] Battery fabrication: The initial separator is assembled with a positive electrode (a conventional positive electrode in the art), a negative electrode (a conventional negative electrode in the art) and an electrolyte to form a battery.

[0234] The prepared battery is subjected to hot pressing, wherein the hot pressing conditions include: a hot pressing temperature of 60℃-90℃ (e.g., 60℃, 65℃, 70℃, 75℃, 80℃, 85℃ or 90℃), a hot pressing pressure of 0.1MPa-1.5MPa (e.g., 0.1MPa, 0.3MPa, 0.5MPa, 0.8MPa, 1MPa, 1.3MPa or 1.5MPa), and a hot pressing time of 10min-60min (10min, 20min, 30min, 40min, 50min or 60min).

[0235] After hot pressing, because the initial first polymer is partially dissolved in the electrolyte and the second polymer is completely dissolved in the electrolyte, the ceramic layer of the separator contains both the first and second polymers. The partially dissolved first polymer and the completely dissolved second polymer form numerous pores in the middle and / or surface of the ceramic layer, resulting in the separator with numerous pores described in this disclosure. It is understood that the initial first polymer and the first polymer in the ceramic layer are of the same type, but the average particle size of the initial first polymer differs from the average particle size of the second polymer. Hot pressing is an essential step in the battery fabrication process and is also referred to as formation in the art.

[0236] In existing technologies, the adhesive layer has adhesive properties. During battery manufacturing, it can improve the stability between the separator and the positive and negative active layers, ensuring that the cell does not soften and affect the battery's manufacturing efficiency. However, during battery use, the adhesive layer reduces the battery's fast-charging performance. In contrast, the separator in the battery of this disclosure, during battery manufacturing, includes a ceramic layer comprising a first polymer and a second polymer. Both the first and second polymers have adhesive properties and can replace the adhesive layer to improve the stability between the separator and the positive and negative active layers. During battery use (after hot-pressing), the first polymer partially dissolves in the electrolyte, and the second polymer completely dissolves in the electrolyte, reducing the adverse effects of the first and second polymers on the battery's fast-charging performance.

[0237] The battery disclosed herein has high rate performance, high long cycle performance, and good fast charging performance.

[0238] The following examples illustrate the separator and battery of this disclosure.

[0239] Example Group I (Ceramic layer excluding the first polymer)

[0240] Example I-1

[0241] This example provides a diaphragm comprising a polymer layer and a porous ceramic layer on one surface of the polymer base layer. By weight, the porous ceramic layer comprises 20 parts of inorganic particles: alumina, 2 parts of binder: polyvinylidene fluoride, 4 parts of thickener: fluoroalkyl methoxyl ether, and 2 parts of dispersant: sodium carboxymethyl cellulose. The porous ceramic layer includes a first pore with a pore size of 0.5 μm and a second pore with a pore size less than 0.5 μm. The porous ceramic layer satisfies the following conditions: within any 10,000 μm² area on the surface of the porous ceramic layer, the number of first pores is 150; the Dv50 of the inorganic particles is 0.8 μm; the pore volume of the first pores accounts for 10% of the total pore volume of the porous ceramic layer; the thickness of the porous ceramic layer is 2 μm; the polymer layer is a polyethylene layer with a thickness of 7 μm and a porosity of 38%; and the surface density of the porous ceramic layer on one side is 2.6 g / m³. 2 .

[0242] Its preparation method includes the following steps:

[0243] 1) Mix 20 parts alumina, 4 parts sodium carboxymethyl cellulose, 2 parts polyvinylidene fluoride, 2 parts fluoroalkyl methoxy alcohol ether, and 72 parts deionized water to obtain the first slurry;

[0244] 2) Take 100 parts of the first slurry mentioned above, add polymer particles (polymethyl methacrylate-acrylonitrile copolymer particles), mix and stir to obtain the second slurry; wherein, the Dv50 of the polymethyl methacrylate-acrylonitrile copolymer particles is 5 μm, and the weight ratio of the polymethyl methacrylate-acrylonitrile copolymer particles to alumina is shown in Table 1.

[0245] 3) The second slurry is coated onto the upper and lower surfaces of the polymer substrate using a microgravure plate, and after drying, a diaphragm precursor is obtained;

[0246] 4) The above-mentioned diaphragm precursor is immersed in NMP at 80°C for 2 minutes, and then washed and dried to obtain the diaphragm.

[0247] Examples I-2 to I-12, Comparative Examples I-1 to Comparative Examples I-3

[0248] Each diaphragm is provided, the difference from Example I-1 being that the parameters in Table I-1 are modified.

[0249] Comparative Example I-4

[0250] Each diaphragm is provided, the difference from Example 1-1 being the modified parameters in Table I-1.

[0251] Comparative Example I-5

[0252] This example provides a diaphragm comprising a polymer layer and a porous ceramic layer on one surface of the polymer base layer. By weight, the porous ceramic layer comprises 20 parts of inorganic particles: alumina, 2 parts of binder: polyvinylidene fluoride, 4 parts of thickener: fluoroalkyl methoxyl ether, and 2 parts of dispersant: sodium carboxymethyl cellulose. The porous ceramic layer includes only secondary pores with a pore size less than 0.5 μm, and the thickness of the porous ceramic layer is 2 μm. The polymer layer is a polyethylene layer with a thickness of 7 μm and a porosity of 50%. The areal density of the porous ceramic layer on one side is 3.4 g / m³. 2 .

[0253] Its preparation method includes the following steps:

[0254] 1) Mix 20 parts alumina, 4 parts sodium carboxymethyl cellulose, 2 parts polyvinylidene fluoride, 2 parts fluoroalkyl methoxy alcohol ether, and 72 parts deionized water to obtain the first slurry;

[0255] 2) The first slurry is coated onto the upper and lower surfaces of the polymer substrate using a micro-gravure plate, and then dried to obtain a diaphragm.

[0256] Table I-1:

[0257] Experimental Example 1

[0258] This example provides a series of batteries, including a positive electrode, a negative electrode, a separator, and an electrolyte, the preparation of which includes the following steps:

[0259] (1) Preparation of positive electrode

[0260] The positive electrode active material (lithium iron phosphate (LFP) doped with titanium and vanadium, Dv50 = 1 μm), positive electrode binder (polyvinylidene fluoride (PVDF)), and positive electrode conductive agent (acetylene black) were mixed in a weight ratio of 96.5:1.5:2.0. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until a uniform and fluid positive electrode slurry was formed. The positive electrode slurry was uniformly coated on both sides of an aluminum foil with a thickness of 10 μm. The coated aluminum foil was baked in an oven with five different temperature gradients (95℃±5℃, 100℃±5℃, 103℃±5℃, 100℃±5℃, 95℃±5℃), and then dried in an oven at 120℃ for 8 hours. Finally, the aluminum foil was rolled and slit to obtain the desired positive electrode sheet.

[0261] (2) Preparation of negative electrode

[0262] The negative electrode active material (artificial graphite), negative electrode conductive agent (including 0.2 parts by weight of single-walled carbon nanotubes (SWCNT) and 1 part by weight of conductive carbon black (SP), and negative electrode binder (including 1 part by weight of sodium carboxymethyl cellulose (CMC-Na) and 2.5 parts by weight of styrene-butadiene rubber (SBR)) are mixed in a weight ratio of 95.3:1.2:3.5. The mixture is prepared by a wet process (water is added to the above mixture and stirred under vacuum until the mixture becomes a homogeneous and fluid negative electrode slurry). The slurry is coated on both sides of the negative electrode current collector (copper foil), and then dried (temperature: 85℃, time: 5h), rolled and die-cut to obtain the negative electrode sheet.

[0263] (3) Preparation of electrolyte

[0264] In an argon-filled glove box (moisture content <10 ppm, oxygen content <1 ppm), 36 parts by weight of ethyl methyl carbonate (EMC), 27 parts by weight of ethyl acetate (EA), and 13.5 parts by weight of ethylene carbonate (EC) were mixed evenly to obtain mixed solution 1. 4.5 parts by weight of vitamin C were added to mixed solution 1 to obtain mixed solution 2. 6.5 parts by weight of LiFSi and 12.5 parts by weight of lithium hexafluorophosphate were slowly added to mixed solution 2, and the mixture was stirred evenly to obtain a non-aqueous electrolyte.

[0265] (4) Preparation of lithium-ion batteries

[0266] The positive electrode sheet from step (1), the separators from each embodiment and comparative example, and the negative electrode sheet from step (2) are wound together to obtain bare batteries without electrolyte injection. The bare batteries are placed in outer packaging foil, and the electrolyte from step (3) is injected into the dried bare batteries. After vacuum sealing, standing, formation, shaping, sorting and other processes, the desired lithium-ion batteries are obtained.

[0267] Test cases I-2 to I-4

[0268] The membrane test in Example 1 was conducted using the same method as in Example I-1, except that the positive electrode active material Dv50 of the positive electrode sheet changed as shown in Table I-2.

[0269] Test Case I

[0270] Test the following performance characteristics of the above batteries:

[0271] (1) -20℃ Cyclic Test

[0272] Place the lithium-ion battery in an environment of (-20±2)℃ and let it stand for 2-3 hours. When the battery body reaches (25±2)℃, charge the battery at a constant current of 1C with a cutoff current of 0.05C. After the battery is fully charged, let it rest for 5 minutes, and then discharge it at a constant current of 1C to the cutoff voltage of 3.0V. Record the highest discharge capacity of the first 3 cycles as the initial capacity Q. When the cycle reaches 10 times, record the discharge capacity Q1 of the last cycle. The capacity retention rate (%) = Q1 / Q × 100%. Record the results in Table I-2.

[0273] (2) 25℃ Cyclic Test

[0274] Place the lithium-ion battery in an environment of (25±2)℃ and let it stand for 2-3 hours. When the battery body reaches (25±2)℃, charge the battery at 3C constant current with a cutoff current of 0.05C. After the battery is fully charged, let it rest for 5 minutes, and then discharge it at 3C constant current to the cutoff voltage of 3.0V. Record the highest discharge capacity of the first 3 cycles as the initial capacity Q. When the cycle reaches 1000 times, record the discharge capacity Q1 of the last cycle. The capacity retention rate (%) = Q1 / Q × 100%. Record the results in Table I-2.

[0275] (3) Thermal shock test at 130℃

[0276] The lithium-ion battery was heated in a convection air chamber at an initial temperature of (25±3)℃ with a temperature change rate of (5±2)℃ / min. The temperature was increased to (130±2)℃ and held for 60 min before the test was ended. The battery status was recorded and the results were recorded in Table I-2.

[0277] Ratio Performance Test

[0278] The lithium-ion battery was placed in an environment of (25±2)℃ and left to stand for 2-3 hours. When the battery body reached (25±2)℃, the battery was charged at a constant current of 0.5C with a cutoff current of 0.05C. After the battery was fully charged, it was left to stand for 5 minutes to obtain the battery capacity Q. Then, it was discharged at a constant current of 1C to the cutoff voltage of 3.0V. Then, the battery was charged at a constant current of 5C with a cutoff current of 0.05C to obtain the capacity Q1. The charging capacity retention rate (%) = Q1 / Q × 100%. The results are recorded in Table I-2.

[0279] Self-discharge test:

[0280] Place the lithium-ion battery in an environment of (25±2)℃ and let it stand for 2-3 hours. When the battery body reaches (25±2)℃, charge the battery at a constant current of 0.5C with a cutoff current of 0.05C. Place the fully charged battery in an environment of (25±2)℃ for 48 hours to test the voltage V, and after 72 hours, test the voltage V1. The self-discharge K value is (V-V1) / 72. Record the results in Table I-2.

[0281] Table I-2:

[0282] As shown in Table I-2, compared with the comparative example, the separator provided in the embodiment improves the battery's rate capability, low-temperature discharge capability, and long-cycle performance without affecting the battery's self-discharge and safety performance.

[0283] Example II Group

[0284] Example II-1

[0285] (1) Preparation of the diaphragm

[0286] Composition preparation: Substrate: Polyethylene, thickness 9μm;

[0287] Ceramic layer: Inorganic particles: Alumina; Thickener: Sodium carboxymethyl cellulose; Diaphragm binder: Poly(meth)acrylic acid; Initial first polymer: Polymethyl methacrylate; Second polymer: Polymethyl methacrylate; wherein the weight ratio of the inorganic particles, the thickener, and the diaphragm binder is 92%:3%:5%; the weight ratio of the initial first polymer, the second polymer, and the inorganic particles is 7%:7%:86%.

[0288] An aqueous slurry (with a solid content of 28%) is prepared by mixing inorganic particles, water, thickener and membrane binder. A first polymer and a second polymer are added to the aqueous slurry to prepare a ceramic slurry. The ceramic slurry is coated on both sides of a substrate to obtain an initial diaphragm.

[0289] (2) Preparation of electrolyte

[0290] Ingredient preparation: Lithium salt: Lithium hexafluorophosphate, 12.5 parts by weight;

[0291] Organic solvent: 76.5 parts by weight, wherein the weight ratio of ethyl methyl carbonate (EMC), ethyl acetate (EA) and ethylene carbonate (EC) is 35%:35%:30%;

[0292] LiFSi, 6.5 parts by weight;

[0293] Additive: Ethylene carbonate (VC), 4.5 parts by weight;

[0294] In an argon-filled glove box (moisture content <10ppm, oxygen content <1ppm), organic solvents are mixed evenly to obtain mixed solution 1. Additives are added to mixed solution 1 to obtain mixed solution 2. LiFSi and lithium salt are slowly added to mixed solution 2 and stirred evenly to obtain a non-aqueous electrolyte.

[0295] (3) Preparation of positive electrode

[0296] The positive electrode active material (lithium iron phosphate (LFP) doped with titanium and vanadium), positive electrode binder (polyvinylidene fluoride (PVDF)), and positive electrode conductive agent (acetylene black) were mixed in a weight ratio of 96.5:1.5:2.0. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until a uniform and fluid positive electrode slurry was formed. The positive electrode slurry was uniformly coated on both sides of an aluminum foil with a thickness of 10 μm. The coated aluminum foil was baked in an oven with five different temperature gradients (95℃±5℃, 100℃±5℃, 103℃±5℃, 100℃±5℃, 95℃±5℃), and then dried in an oven at 120℃ for 8 hours. Finally, the aluminum foil was rolled and slit to obtain the desired positive electrode sheet.

[0297] (4) Preparation of negative electrode

[0298] The negative electrode active material (artificial graphite), negative electrode conductive agent (including 0.2 parts by weight of single-walled carbon nanotubes (SWCNT) and 1 part by weight of conductive carbon black (SP), and negative electrode binder (including 1 part by weight of sodium carboxymethyl cellulose (CMC-Na) and 2.5 parts by weight of styrene-butadiene rubber (SBR)) are mixed in a weight ratio of 95.3:1.2:3.5. The mixture is prepared by a wet process (water is added to the above mixture and stirred under vacuum until the mixture becomes a homogeneous and fluid negative electrode slurry). The slurry is coated on both sides of the negative electrode current collector (copper foil), and then dried (temperature: 85℃, time: 5h), rolled and die-cut to obtain the negative electrode sheet.

[0299] (5) Preparation of lithium-ion secondary batteries

[0300] The positive electrode sheet from step (3), the separator from step (1), and the negative electrode sheet from step (4) are wound together to obtain a bare battery without electrolyte filling. A pressure of 5 MPa is applied to the wound core for 10 minutes. The bare battery is placed in an outer packaging foil, and the electrolyte from step (2) is injected into the dried bare battery. After vacuum sealing, standing, hot pressing (wherein the hot pressing temperature is 80°C, the hot pressing pressure is 1 MPa, and the hot pressing time is 40 minutes; after hot pressing, the first polymer in the initial separator partially dissolves, and the second polymer is completely dissolved; the partially dissolved first polymer and the completely dissolved second polymer form numerous pores in the middle and surface of the ceramic layer of the separator to obtain the separator described in this disclosure), shaping, and sorting processes, the desired lithium-ion secondary battery is obtained. The separator after hot pressing, based on the total weight of the ceramic layer, contains 85.6% inorganic particles, 6.9% of the first polymer, 4.7% of the separator binder, and 2.8% of the thickener.

[0301] Example II-2

[0302] The procedure was carried out in accordance with Example II-1, except that the weight proportions of the organic solvent remained unchanged, and the organic solvent was adjusted to consist of a first organic solvent (EMC) and a second organic solvent (EC), wherein the weight ratio of the first organic solvent to the second organic solvent was 1:1.

[0303] Example II-3 group

[0304] This set of embodiments is used to illustrate that different combinations of parameter values ​​can still achieve the effects of this disclosure.

[0305] This embodiment group is carried out with reference to Embodiment II-1, and see Tables 1-1 and 1-2 for details.

[0306] Example II-4

[0307] This embodiment is used to illustrate that different combinations of parameter values ​​can still achieve the effects of this disclosure.

[0308] The procedure was carried out in accordance with Example II-2, as detailed in Tables 1-1 and 1-2.

[0309] Example II-5 group

[0310] This set of examples illustrates the effects of changes in D1 / D2.

[0311] This embodiment group is carried out with reference to Embodiment II-1, except that D1 / D2 is changed, as detailed in Tables 1-1 and 1-2.

[0312] Example II-6 group

[0313] This set of examples illustrates the effects of changes in D4 / H1.

[0314] This embodiment group is carried out with reference to Embodiment II-1, except that D4 / H1 is changed, as detailed in Tables 1-1 and 1-2.

[0315] Example II-7 group

[0316] This set of examples illustrates the effects of changing the specific choice of the first polymer.

[0317] This embodiment group is based on Example II-1, except that the first polymer is changed, as detailed in Tables 1-1 and 1-2.

[0318] Example II-8 group

[0319] This set of examples illustrates the effects of changing the specific choice of the second polymer.

[0320] This embodiment group is based on Example II-1, except that the second polymer is changed, as detailed in Tables 1-1 and 1-2.

[0321] Example II-9 group

[0322] This set of examples illustrates the effects of changes in the weight ratio of EMC / EA / EC.

[0323] This embodiment group is based on Embodiment II-1, except that the weight ratio of EMC / EA / EC is changed, as detailed in Tables 1-1 and 1-2.

[0324] Example II-10 group

[0325] This set of examples illustrates the effects of a change in the weight ratio of the first organic solvent to the second organic solvent.

[0326] This embodiment group is carried out with reference to Embodiment II-2, except that the weight ratio of the first organic solvent to the second organic solvent is changed, as detailed in Tables 1-1 and 1-2.

[0327] Example II-11 group

[0328] This set of examples illustrates the effects of changes in the coverage of the first polymer on the surface of the ceramic layer.

[0329] This embodiment is based on Embodiment II-1, except that the coverage of the first polymer on the ceramic layer surface is changed by adjusting the ratio of the initial weight of the first polymer, the weight of the second polymer, and the weight of the inorganic particles. See Tables 1-1 and 1-2 for details.

[0330] Example II-12 group

[0331] This set of examples illustrates the effects of changes in the volume percentage of pores with a diameter ≥ 0.5 μm in the ceramic layer.

[0332] This embodiment group is based on Embodiment II-1, except that the volume ratio of pores with a diameter ≥0.5μm in the ceramic layer is changed by adjusting the weight ratio of the initial first polymer, the second polymer and the inorganic particles. See Tables 1-1 and 1-2 for details.

[0333] Comparative Example II-1

[0334] Composition preparation: Substrate: Polyethylene, thickness 9μm;

[0335] Ceramic layer: Inorganic particles: Alumina; Thickener: Sodium carboxymethyl cellulose; Diaphragm binder: Poly(meth)acrylic acid; wherein the weight ratio of the inorganic particles, the thickener, and the diaphragm binder is 92%:3%:5%.

[0336] An aqueous slurry (with a solid content of 28%) is prepared by mixing inorganic particles, water, thickener and membrane binder, and the aqueous slurry is coated on both sides of the substrate.

[0337] Comparative Example II-2

[0338] The procedure is carried out in accordance with Example II-1, except that D1 / D2 < 1, as detailed in Tables 1-1 and 1-2.

[0339] Comparative Example II-3

[0340] The procedure was carried out in accordance with Example II-1, except that D1 / D2 > 20, as detailed in Tables 1-1 and 1-2.

[0341] Table 1-1

[0342] * indicates the same as in Example II-1.

[0343] Table 1-2

[0344] * indicates the same as in Example II-1.

[0345] Test Case II

[0346] The separators and lithium-ion secondary batteries obtained in the examples and comparative examples were subjected to the following tests:

[0347] (1) Diaphragm shrinkage rate test

[0348] Take a diaphragm sample with a length of 15cm*15cm, and punch two holes with a diameter of 0.5mm at 10cm intervals along the length of the diaphragm. Place the sample in an oven at 150±2℃ and bake for 1 hour. The distance between the two holes before baking is L1, and the distance between the two holes after baking is L2. Heat shrinkage = (L1-L2) / L1*100%.

[0349] (2) Furnace temperature test at 150℃

[0350] The lithium-ion secondary batteries were heated in a convection air chamber at an initial temperature of (25±3)℃ with a temperature change rate of (5±2)℃ / min. The temperature was increased to (150±2)℃ and held for 60 minutes before the test was ended. The battery status was recorded. Each sample consisted of 30 batteries. If no explosion and / or fire occurred, it was considered a "pass". If an explosion or fire occurred, it was considered a "fail". The result was expressed as "number of passes / 30". For example, "30 / 30" means all passed, and "10 / 30" means 10 out of 30 batteries failed.

[0351] (3) Long-term cycle test

[0352] Place the lithium-ion secondary battery in an environment of (25±2)℃ and let it stand for 2-3 hours. When the battery body reaches (25±2)℃, charge the battery at 3C constant current with a cutoff current of 0.05C. After the battery is fully charged (100% SOC), let it rest for 5 minutes, and then discharge it at 3C constant current to the cutoff voltage of 2.2V. Record the highest discharge capacity of the first 3 cycles as the initial capacity Q. When the cycle reaches 2000 times, record the discharge capacity Q1 of the last cycle. The capacity retention rate (%) = Q1 / Q × 100%.

[0353] (4) Fast charging performance test

[0354] The lithium-ion secondary battery was left to stand at 25℃±2℃ for 4 hours, then discharged at 0.5C to 2.2V, and charged at 0.5C to the upper limit voltage (3.65V). The cell capacity Q2 was recorded. The fully charged cell was then discharged at 1C constant current to 2.2V at 25℃±2℃, left to stand at 25℃ for 4 hours, and charged at 5C constant current to the upper limit voltage (3.65V). It was then left to stand at room temperature for 2 hours. The cell capacity Q3 was recorded. Capacity retention rate = Q3 / Q2*100%

[0355] (5) K-value test

[0356] The lithium-ion secondary battery was left to stand at 25℃±2℃ for 4 hours, discharged at 0.5C to 2.2V, charged at 0.5C to 3.65V, left to stand at 45℃±2℃ for 48 hours, and the voltage V1 was recorded. Then it was left to stand at 25℃±2℃ for 72 hours and the voltage V2 was recorded. The K value is (V1-V2) / 72, and the unit is mV / h.

[0357] The results are recorded in Table II-2.

[0358] Table II-2

[0359] As can be seen from Table II-2, and from the comparative examples and embodiments, the separator of the embodiments has a lower thermal shrinkage rate. The furnace temperature test results of the battery made from the separator of the embodiments are better, the cycle capacity retention rate is significantly improved, the 5C discharge capacity retention rate is significantly improved, and the K value remains basically unchanged. This indicates that the separator of this disclosure and the battery including the separator, by controlling the number of pores with a diameter ≥0.5μm, the number of first polymers, and the ratio of the average diameter (D1) of the pores with a diameter ≥0.5μm in the ceramic layer to the average particle size (D2) of the inorganic particles, improve the long cycle performance and fast charging performance of the battery without affecting the battery's self-discharge and safety performance.

[0360] Example III Group

[0361] Example III illustrates that the ceramic layer in the diaphragm of this disclosure does not include the first polymer.

[0362] Example III-1

[0363] (1) Preparation of the diaphragm

[0364] Composition preparation: Substrate: Polyethylene, thickness 9μm;

[0365] Ceramic layer: Inorganic particles: Alumina; Thickener: Sodium carboxymethyl cellulose; Diaphragm binder: Poly(meth)acrylic acid; Second polymer: Methyl acrylate-acrylic acid copolymer; wherein, the weight ratio of the inorganic particles, the thickener, and the diaphragm binder is 92%:3%:5%; the weight ratio of the second polymer to the inorganic particles is 7%:93%.

[0366] An aqueous slurry (with a solid content of 28%) is prepared by mixing inorganic particles, water, thickener and membrane binder. A second polymer is added to the aqueous slurry to prepare a ceramic slurry. The ceramic slurry is coated on both sides of the substrate to obtain an initial membrane.

[0367] (2) Preparation of electrolyte

[0368] Ingredient preparation: Lithium salt: Lithium hexafluorophosphate, 12.5 parts by weight;

[0369] Organic solvent: 76.5 parts by weight, wherein the weight ratio of ethyl methyl carbonate (EMC), ethyl acetate (EA) and ethylene carbonate (EC) is 35%:35%:30%;

[0370] LiFSi, 6.5 parts by weight;

[0371] Additive: Ethylene carbonate (VC), 4.5 parts by weight;

[0372] In an argon-filled glove box (moisture content <10ppm, oxygen content <1ppm), organic solvents are mixed evenly to obtain mixed solution 1. Additives are added to mixed solution 1 to obtain mixed solution 2. LiFSi and lithium salt are slowly added to mixed solution 2 and stirred evenly to obtain a non-aqueous electrolyte.

[0373] (3) Preparation of positive electrode

[0374] The positive electrode active material (NCM), positive electrode binder (polyvinylidene fluoride (PVDF)), and positive electrode conductive agent (acetylene black) were mixed in a weight ratio of 96.5:1.5:2.0. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until a homogeneous and fluid positive electrode slurry was formed. The positive electrode slurry was uniformly coated on both sides of an aluminum foil with a thickness of 10 μm. The coated aluminum foil was baked in an oven with five different temperature gradients (95℃±5℃, 100℃±5℃, 103℃±5℃, 100℃±5℃, 95℃±5℃), and then dried in an oven at 120℃ for 8 hours. Finally, the aluminum foil was rolled and slit to obtain the desired positive electrode sheet.

[0375] (4) Preparation of negative electrode

[0376] The negative electrode active material (graphite and silicon oxide in a weight ratio of 60:40, i.e., W3 is 40%), negative electrode conductive agent (0.2 parts by weight of single-walled carbon nanotubes (SWCNT) and 1 part by weight of conductive carbon black (SP), and negative electrode binder (1 part by weight of sodium carboxymethyl cellulose (CMC-Na) and 2.5 parts by weight of styrene-butadiene rubber (SBR)) are mixed in a weight ratio of 95.3:1.2:3.5. The mixture is prepared by a wet process (water is added to the above mixture and stirred under vacuum until the mixture becomes a homogeneous and fluid negative electrode slurry). The slurry is coated on both sides of the negative electrode current collector (copper foil), dried (temperature: 85℃, time: 5h), rolled and die-cut to obtain the negative electrode sheet.

[0377] (5) Preparation of lithium-ion secondary batteries

[0378] The positive electrode sheet from step (3), the separator from step (1), and the negative electrode sheet from step (4) are wound together to obtain a bare battery without electrolyte filling. A pressure of 5 MPa is applied to the wound core for 10 minutes. The bare battery is placed in an outer packaging foil, and the electrolyte from step (2) is injected into the dried bare battery. After vacuum sealing, standing, hot pressing (wherein the hot pressing temperature is 80°C, the hot pressing pressure is 1 MPa, and the hot pressing time is 40 minutes; after hot pressing, the first polymer in the initial separator partially dissolves, and the second polymer is completely dissolved; the partially dissolved first polymer and the completely dissolved second polymer form numerous pores in the middle and surface of the ceramic layer of the separator, thus obtaining the separator described in this disclosure), shaping, and sorting processes, the desired lithium-ion secondary battery is obtained. Specifically, the separator after hot pressing, based on the total weight of the ceramic layer, contains 85.6% inorganic particles, 6.9% of the first polymer, 4.7% of the separator binder, and 2.8% of the thickener. See Table III-1 for details.

[0379] Example III-2 group

[0380] This set of examples illustrates the effects that occur when D5 changes.

[0381] This embodiment group is carried out with reference to Embodiment III-1, except that D5 / D1 is changed by adjusting D5, as detailed in Table III-1.

[0382] Example III-3 group

[0383] This set of examples illustrates the effects that occur when D2 changes.

[0384] This embodiment group is carried out with reference to embodiment III-1, except that D1 / D2 is changed by adjusting D2, as detailed in Table III-1.

[0385] Example III-4 group

[0386] This set of examples illustrates the effects that occur when D5 / D1 and D1 / D2 change.

[0387] This embodiment group is carried out with reference to Embodiment III-1, except that D5 / D1 and D1 / D2 are changed, as detailed in Table III-1.

[0388] Example III-5 group

[0389] This set of examples illustrates the effects of changes in EMC:EA:EC.

[0390] This embodiment group is carried out with reference to Embodiment III-1, except that EMC:EA:EC is changed, as detailed in Table III-1.

[0391] Example III-6

[0392] This set of examples illustrates the effects of a change in the weight ratio of the first organic solvent to the second organic solvent.

[0393] This embodiment group is carried out with reference to Embodiment III-1, except that the weight ratio of the first organic solvent to the second organic solvent is changed, as detailed in Table III-1.

[0394] Comparative Example III-1

[0395] The procedure was carried out in accordance with Example III-1, except that D5 / D1 < 0.5, as detailed in Table III-1.

[0396] Comparative Example III-2

[0397] The procedure is carried out in accordance with Example III-1, except that D5 / D1 > 5, as detailed in Table III-1.

[0398] Comparative Example III-3

[0399] The procedure was carried out in accordance with Example III-1, except that D5 was 12 μm, as detailed in Table III-1.

[0400] Comparative Example III-4

[0401] Composition preparation: Substrate: Polyethylene, thickness 9μm;

[0402] Ceramic layer: Inorganic particles: Alumina (1μm); Thickener: Sodium carboxymethyl cellulose; Diaphragm binder: Poly(meth)acrylic acid; wherein the weight ratio of the inorganic particles, the thickener, and the diaphragm binder is 92%:3%:5%.

[0403] An aqueous slurry (with a solid content of 28%) is prepared by mixing inorganic particles, water, thickener and membrane binder, and the aqueous slurry is coated on both sides of the substrate.

[0404] Table I-1

[0405] * indicates the same as in Example III-1.

[0406] Example IV illustrates that the ceramic layer in the diaphragm of this disclosure comprises a first polymer.

[0407] Example IV-1

[0408] The procedure was carried out in accordance with Example III-1, except that the diaphragm was changed, as detailed below:

[0409] (1) Preparation of the diaphragm

[0410] Composition preparation: Substrate: Polyethylene, thickness 9μm;

[0411] Ceramic layer: Inorganic particles: Alumina; Thickener: Sodium carboxymethyl cellulose; Diaphragm binder: Poly(meth)acrylic acid; Initial first polymer: Methyl methacrylate-diethylacrylamide-butadiene copolymer; Second polymer: Methyl acrylate-acrylic acid copolymer; wherein, the weight ratio of the inorganic particles, the thickener, and the diaphragm binder is 92%:3%:5%; the weight ratio of the initial first polymer, the second polymer, and the inorganic particles is 7%:7%:86%.

[0412] An aqueous slurry (with a solid content of 28%) is prepared by mixing inorganic particles, water, thickener and membrane binder. A first polymer and a second polymer are added to the aqueous slurry to prepare a ceramic slurry. The ceramic slurry is coated on both sides of a substrate to obtain an initial diaphragm.

[0413] Example IV-2

[0414] The procedure was carried out in accordance with Example IV-1, except that the weight proportions of the organic solvent remained unchanged, and the organic solvent was adjusted to consist of a first organic solvent (EMC) and a second organic solvent (EA), wherein the weight ratio of the first organic solvent to the second organic solvent was 1:1, as detailed in Tables IV-1 and IV-2.

[0415] Example IV-3

[0416] This embodiment is used to illustrate that different combinations of parameter values ​​can still achieve the effects of this disclosure.

[0417] This embodiment is based on embodiment IV-1, and see Tables IV-1 and IV-2 for details.

[0418] Example IV-4

[0419] This embodiment is used to illustrate that different combinations of parameter values ​​can still achieve the effects of this disclosure.

[0420] The procedure was carried out in accordance with Example IV-2, and specific details can be found in Tables IV-1 and IV-2.

[0421] Example IV-5 group

[0422] This set of examples illustrates the effects of changes in D5 / D1.

[0423] This embodiment group is carried out with reference to Embodiment II-1, except that D5 / D1 is changed, as detailed in Tables IV-1 and IV-2.

[0424] Example IV-6 group

[0425] This set of examples illustrates the effects of changes in D1 / D2.

[0426] This embodiment group is based on embodiment IV-1, except that D1 / D2 is changed, as detailed in Tables IV-1 and IV-2.

[0427] Example IV-7 group

[0428] This set of examples illustrates the effects of changes in D4 / H1.

[0429] This embodiment group is carried out with reference to embodiment IV-1, except that D4 / H1 is changed, as detailed in Tables IV-1 and IV-2.

[0430] Example IV-8 group

[0431] This set of examples illustrates the effects of changing the specific choice of the first polymer.

[0432] This set of examples is based on Example IV-1, except that the specific selection of the first polymer is changed, as detailed in Tables IV-1 and IV-2.

[0433] Example IV-9 group

[0434] This set of examples illustrates the effects of changing the specific choice of the second polymer.

[0435] This set of examples is based on Example II-1, except that the specific selection of the second polymer is changed, as detailed in Tables IV-1 and IV-2.

[0436] Example IV-10 group

[0437] This set of examples illustrates the effects of changes in EMC:EA:EC.

[0438] This embodiment group is carried out with reference to embodiment IV-1, except that EMC:EA:EC is changed, see Table IV-1 and Table IV-2 for details.

[0439] Example IV-11 group

[0440] This set of examples illustrates the effects of a change in the weight ratio of the first organic solvent and the second organic solvent.

[0441] This set of examples is based on Example IV-2, except that the weight ratio of the first organic solvent and the second organic solvent is changed, as detailed in Tables IV-1 and IV-2.

[0442] Example IV-12 group

[0443] This set of examples illustrates the effects of changes in W3 / N1.

[0444] This embodiment group is carried out with reference to embodiment IV-1, except that W3 / N1 is changed, as detailed in Tables IV-1 and IV-2.

[0445] Example IV-13 group

[0446] This set of examples illustrates the effects of changes in the volume percentage of pores with a diameter ≥ 0.5 μm in the ceramic layer.

[0447] This embodiment group is based on Embodiment IV-1, except that the volume ratio of pores with a diameter ≥0.5μm in the ceramic layer is changed. See Table IV-1 and Table IV-2 for details.

[0448] Comparative Example IV-1

[0449] The procedure was carried out in accordance with Example IV-1, except that D5 / D1 < 0.5, as detailed in Tables IV-1 and IV-2.

[0450] Comparative Example IV-2

[0451] The procedure was carried out in accordance with Example IV-1, except that D5 / D1 > 5, as detailed in Tables IV-1 and IV-2.

[0452] Comparative Example IV-3

[0453] The procedure was carried out in accordance with Example IV-1, except that D5 was 12 μm, as detailed in Tables IV-1 and IV-2.

[0454] Table IV-1

[0455] * indicates the same as in Example II-1.

[0456] Table II-2

[0457] * indicates the same as in Example IV-1.

[0458] Test Case IV

[0459] The separators and lithium-ion secondary batteries obtained in the examples and comparative examples were subjected to the following tests:

[0460] (1) Diaphragm shrinkage rate test

[0461] Take a diaphragm sample with a length of 15cm*15cm, and punch two holes with a diameter of 0.5mm at 10cm intervals along the length of the diaphragm. Place the sample in an oven at 150±2℃ and bake for 1 hour. The distance between the two holes before baking is L1, and the distance between the two holes after baking is L2. Heat shrinkage = (L1-L2) / L1*100%.

[0462] (2) Furnace temperature tests at 130℃ and 150℃

[0463] The lithium-ion secondary batteries were heated in a convection air chamber at an initial temperature of (25±3)℃, with a temperature change rate of (5±2)℃ / min, to (130±2)℃ and (150±2)℃ respectively. The temperature was maintained for 60 minutes before the test ended. The battery status at (130±2)℃ and (150±2)℃ was recorded. Each sample consisted of 30 batteries. A battery that did not explode and / or catch fire was considered a "pass," while an explosion or fire was considered a "fail." The result was expressed as "number of passes / 30," for example, "30 / 30" means all passed, and "10 / 30" means 10 out of 30 batteries failed. It should be noted that a furnace temperature test result of "30 / 30" at 130℃ indicates that the safety performance of the lithium-ion secondary batteries was not affected.

[0464] (3) Fast charging cycle test

[0465] The lithium-ion secondary battery was placed in an environment of (25±2)℃ and left to stand for 2-3 hours. When the battery body reached (25±2)℃, the thickness of the battery was recorded as T1. The battery was charged at 3C constant current with a cutoff current of 0.05C. After the battery was fully charged (100% SOC), it was left to stand for 5 minutes, and then discharged at 3C constant current to the cutoff voltage of 3.0V. The highest discharge capacity of the first 3 cycles was recorded as the initial capacity Q. When the cycle reached 800 times, the thickness of the battery was tested as T2 and the discharge capacity of the last cycle Q1 was recorded. The capacity retention rate (%) = Q1 / Q×100%, and the thickness expansion rate (%) = [(T2-T1) / T1]×100%.

[0466] (4) Ratio Performance Test

[0467] The lithium-ion secondary battery was left to stand at 25℃±2℃ for 4 hours, discharged at 0.5C to 2.2V, and charged at 0.5C to the upper limit voltage (4.25V). The cell capacity Q2 was recorded. The fully charged cell was discharged at 10C constant current to 2.5V at 25℃±2℃. The cell capacity Q3 was recorded. The capacity retention rate = Q3 / Q2*100%.

[0468] (5) Energy density WED test

[0469] The finished battery was weighed at 25℃ to obtain the battery weight;

[0470] The prepared battery was charged to full capacity (100% SOC) at constant current and constant voltage at 25℃. The charging current was 0.5C, the battery was charged to 4.25V, the cut-off current was 0.05C, and then the battery was discharged to 2.5V at 0.5C. The capacity discharged was recorded as the battery capacity.

[0471] Calculate the gravimetric energy density (Wh / Kg) = (battery capacity * platform voltage) / battery weight.

[0472] (6) K-value test

[0473] The lithium-ion secondary battery was left to stand at 25℃±2℃ for 4 hours, discharged at 0.5C to 2.5V, charged at 0.5C to 4.25V, left to stand at 45℃±2℃ for 48 hours, and the voltage V1 was recorded. Then it was left to stand at 25℃±2℃ for 72 hours and the voltage V2 was recorded. The K value is (V1-V2) / 72, and the unit is mV / h.

[0474] The results are recorded in Table 3.

[0475] Table 3

[0476] As can be seen from Table 3, and through the comparative examples and embodiments, the separator in the embodiments has a lower thermal shrinkage rate, the battery passed the 130°C furnace temperature test, the 150°C furnace temperature test results were better, the cycle capacity retention rate was higher, the thickness expansion rate was lower, the 10C rate discharge capacity retention rate was higher, and the K value remained basically unchanged. This indicates that the battery of this disclosure reduces the battery expansion rate and improves the battery rate performance and fast charge cycle performance by controlling the coverage of pores with a diameter ≥0.5μm in the porous structure, the average particle size of the silicon material, and the ratio of the average particle size of the silicon material to the average diameter of the pores with a diameter ≥0.5μm in the ceramic layer.

[0477] The embodiments of this disclosure have been described above. However, this disclosure is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A diaphragm, characterized in that, The diaphragm includes a substrate and a ceramic layer located on one or both surfaces of the substrate. The ceramic layer comprises inorganic particles and has a porous structure. The porous structure includes a first pore with a diameter greater than or equal to 0.5 μm. Within an arbitrarily selected range of 100 μm × 100 μm on the surface of the ceramic layer, the number of the first pores is 10 to 800. The diaphragm satisfies the following relationship: 1 < D1 / D2 < 20, or 1 < D1 / D3 < 20, where D1 is the average diameter of the first pore in the ceramic layer in μm; D2 is the average particle size of the inorganic particles in μm; and D3 is the Dv50 of the inorganic particles in μm.

2. The diaphragm according to claim 1, characterized in that, The average diameter D1 of the first hole is 0.5μm-10μm, preferably 1μm-8μm; And / or, the average particle size D2 of the inorganic particles is 0.1 μm-3 μm; And / or, the substrate comprises one or more of polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, poly(p-phenylene), polynaphthalene, polyimide, polyamide, aramid, poly(p-phenylene)benzodithiazole, and other materials neutralized together.

3. The diaphragm according to claim 1, characterized in that, The Dv50 of the inorganic particles is 0.1μm-3μm; And / or, the substrate is a porous membrane layer, including at least one of woven membrane, nonwoven membrane, polyolefin membrane, and separator paper, wherein the material of the polyolefin membrane includes one or more of polyethylene, polypropylene, a composite material of polyethylene and polypropylene, and aramid.

4. The diaphragm according to any one of claims 1-3, characterized in that, Based on the total volume of the pores in the ceramic layer, the volume ratio of the first pore is 20%-70%; And / or, the ceramic layer has a coverage of 50%-100% on the surface of the substrate, preferably 60%-90%; And / or, the coverage of the first pore on the surface of the ceramic layer is 10%-50%, preferably 20%-40%; And / or, the ceramic layer further includes a second pore with a diameter of less than 0.5 μm.

5. The diaphragm according to any one of claims 1-4, characterized in that; The thickness of the ceramic layer is 1μm-5μm; And / or, the areal density of the ceramic layer on one side is 1 g / m³. 2 -10g / m 2 ; And / or, the inorganic particles include one or more of alumina, boehmite, magnesium oxide, magnesium hydroxide, barium sulfate, barium titanate, zinc oxide, calcium oxide, silicon dioxide, silicon carbide, and boron nitride.

6. The diaphragm according to any one of claims 1-5, characterized in that, The ceramic layer further includes first polymer particles, and the number of the first polymer particles is 10 to 600 within an arbitrarily selected 100μm×100μm range on the surface of the ceramic layer. Preferably, the first polymer particles are composed of a first polymer, which includes a first monomer, a second monomer, and optionally a third monomer. The first monomer includes one or more of acrylonitrile monomers, styrene monomers, and acrylate monomers. The second monomer includes one or more of dimethacrylamide, diethylacrylamide, divinylbenzene, trimethylolpropane triacrylate, ethylene glycol dimethacrylate, ethylene glycol diacrylate, triethylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate. The third monomer includes one or more of acrylic acid, butadiene, methacrylic acid, acrylamide, hydroxymethylacrylamide, hydroxyethylacrylamide, isopropylacrylamide, glycidyl (meth)acrylate, and allyl glycidyl ester.

7. The diaphragm according to claim 6, characterized in that, Acrylate monomers include one or more of methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, lauryl acrylate, and octadecyl acrylate. And / or, the styrene monomers include one or more of styrene, methylstyrene, tristyrene, and 4-methylstyrene; And / or, the acrylonitrile monomers include one or more of acrylonitrile, triphenylacrylonitrile, 3-cyclopentylacrylonitrile, and 3,3-(diphenyl)acrylonitrile.

8. The diaphragm according to claim 6 or 7, characterized in that, The coverage of the first polymer on the surface of the ceramic layer is 5%-50%, preferably 10%-40%; And / or, based on the total weight of the ceramic layer, the inorganic particles have a weight content of 75%-98%, and the first polymer has a weight content of 1%-18%. And / or, the diaphragm satisfies the following relationship: 2≤D4 / H1≤5, where D4 is the average particle size of the first polymer particles in the ceramic layer, in μm; and H1 is the thickness of the ceramic layer, in μm. And / or, the average particle size D4 of the first polymer particles in the ceramic layer is 2μm-10μm.

9. A battery, characterized in that, The battery includes a positive electrode, a negative electrode, an electrolyte, and a separator according to any one of claims 1-8, wherein the separator is located between the positive electrode and the negative electrode.

10. The battery according to claim 9, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, which includes silicon material. The average particle size D5 of the silicon material is 1μm-10μm, preferably 2μm-8μm. The battery satisfies the following relationship: 0.5≤D5 / D1≤5, preferably 1≤D5 / D1≤4, where D1 is the average diameter of the first pore of the ceramic layer, in μm. Preferably, the silicon material includes at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy; Preferably, the negative electrode active material further includes graphite and / or hard carbon.

11. The battery according to claim 10, characterized in that, The battery satisfies the following relationship: 0.5≤W3 / N1≤10, preferably 1≤W3 / N1≤8, where W3 is the weight content of the silicon material based on the total weight of the negative electrode active material, in %; N1 is the coverage of the first polymer in the ceramic layer on the surface of the ceramic layer, in %; Preferably, W3 is 1%-100%, more preferably 5%-50%; Preferably, N1 is 5%-25%, more preferably 10%-20%.

12. The battery according to any one of claims 9-11, characterized in that, The positive electrode sheet includes a positive current collector and a positive active layer located on at least one surface of the positive current collector. The positive active layer contains a positive active material, and the positive active material satisfies the following formula 1: 0.1 < D1 / (10×D6) < 1 (Formula 1); Wherein, D6 is the Dv50 of the positive electrode active material; Preferably, D6 satisfies: 0.3μm≤D4≤2μm, and / or, the peeling force between the positive electrode active materials is greater than 1N / m.

13. The battery according to any one of claims 9-12, characterized in that, The electrolyte includes an organic solvent, which includes at least two of dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, ethylene carbonate, diethyl carbonate, propyl propionate, ethyl propionate, and ethyl acetate. Based on the total weight of the electrolyte, the weight content of the organic solvent is 64%-86%, preferably 70%-82%. And / or, at 60°C-90°C, the first polymer is immersed in a solvent for 2 min-10 min, and the solubility of the first polymer is less than or equal to 50%, preferably 1%-20%. And / or, the electrolyte further includes LiFSI and optionally additives, said additives including one or more of fluoroethylene carbonate, 1,3-propanesulfonate lactone, vinylene carbonate, lithium difluorophosphate, lithium bis(oxalato)borate, lithium difluorooxalatoborate, lithium difluorooxalatophosphate, lithium tetrafluoroborate, and lithium tetrafluorooxalatophosphate, wherein the weight content of LiFSI is 2%-20% and the weight content of said additives is 0%-9% based on the total weight of said electrolyte.

14. The battery according to claim 13, characterized in that, The organic solvent includes a first organic solvent and a second organic solvent. The first organic solvent includes one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, propyl propionate, ethyl propionate, and ethyl acetate. The second organic solvent includes propylene carbonate and / or ethylene carbonate. Preferably, the weight ratio of the first organic solvent to the second organic solvent is (0.05-20):1, more preferably (0.1-10):

1.

15. The battery according to claim 13, characterized in that, The organic solvents include ethyl methyl carbonate, ethyl acetate, and ethylene carbonate; Preferably, the weight ratio of methyl ethyl carbonate, ethyl acetate and ethylene carbonate in the organic solvent is (10%-70%):(10%-70%):(15%-40%).

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