A battery

Abstract

The present application relates to the technical field of battery, in particular to a battery. The battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator, the separator comprises a carrier layer and a polymer coating layer, the polymer coating layer corresponding to the positive electrode sheet is a first polymer coating layer, and the polymer coating layer corresponding to the negative electrode sheet is a second polymer coating layer, the first polymer coating layer comprises first particles, and the second polymer coating layer comprises second particles; the surface of the negative electrode sheet is provided with a recess; the battery satisfies the following relationship: F 1 <F 2 , 0.1≤M 1 / F 3 ≤1.2, F 3 =F 2 ‑F 1 . The battery of the present application can reduce the risk of dislocation between the separator and the positive and negative electrode sheets, deformation of the electrode assembly and fragmentation of active particles in high-temperature cycles caused by the cycle expansion of the negative electrode sheet during the cycle process, and can also balance the adhesion between the separator and the negative electrode sheet and the interface heat dissipation performance, so that the battery has high long-cycle stability, high-temperature cycle performance and furnace temperature safety performance.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a battery. Background Technology

[0002] With the increasing demand for high energy density in lithium-ion batteries for new energy vehicles and portable electronic devices, silicon-based anode materials have become the most promising next-generation anode materials due to their extremely high theoretical specific capacity. However, silicon materials undergo severe volume expansion and contraction during charging and discharging, an inherent characteristic that severely restricts their commercial application.

[0003] During battery cycling, the repeated and intense expansion and contraction of the silicon-based anode can disrupt the stability of the electrode structure. On the one hand, the expansion stress causes relative displacement between the separator and the positive and negative electrode sheets, resulting in poor interfacial contact and obstructed ion transport paths, leading to a decrease in the battery's long-cycle performance, especially affecting its high-temperature cycle performance. On the other hand, continuous volume deformation causes overall deformation or even cracking of the electrode assembly, leading to the breakage or even detachment of active particles. These broken and detached active particles can easily puncture the separator, causing micro-short circuits and increasing the battery's K-value. Moreover, the macroscopic thickness changes of the electrode sheets will intensify, generating continuous mechanical stress on the separator, which can easily lead to separator stretching, perforation, or detachment from the electrode, thereby causing internal short circuits and posing serious safety hazards.

[0004] Existing technologies such as nanostructuring, porous structures, carbon composites, and surface coatings have alleviated volume expansion to some extent, but none have fundamentally solved the problems of overall electrode structural stability and electrode-separator interface compatibility during cycling. Therefore, it is crucial to invent a battery that can effectively improve the poor electrolytic structural stability caused by volume changes in silicon-based materials and enhance electrode structural stability. Summary of the Invention

[0005] To address the problems in existing technologies where poor electrode assembly structural stability is caused by volume changes in negative electrode active materials (especially silicon-based materials), leading to reduced long-cycle and high-temperature cycling performance, and the difficulty in simultaneously achieving both long-cycle performance and high-temperature safety, this invention provides a battery. This battery improves the adhesion strength between the separator and the negative electrode while reducing the adhesion strength between the separator and the positive electrode. This reduces the risk of misalignment between the separator and the positive and negative electrodes, electrode assembly deformation, and breakage of active particles during high-temperature cycling due to the cyclic expansion of the negative electrode during battery cycling. This improves the battery's long-cycle stability and high-temperature cycling performance. Simultaneously, it balances the adhesion force between the separator and the negative electrode and the interfacial heat dissipation performance, enhancing the battery's furnace temperature safety performance.

[0006] To achieve the above objectives, the present invention provides a battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive and negative electrode. The separator comprises a carrier layer and polymer coatings on both sides of the carrier layer. In the separator, the polymer coating corresponding to the positive electrode is a first polymer coating, and the polymer coating corresponding to the negative electrode is a second polymer coating. The first polymer coating comprises first particles dispersedly distributed, the first particles being composed of acrylate polymers. The second polymer coating comprises second particles dispersedly distributed, the second particles being composed of acrylate polymers. The surface of the negative electrode is provided with a recess.

[0007] The battery satisfies the following relationship: F 1 <F 2 , 0.1≤M 1 / F 3 ≤1.2, where F 3 =F 2 -F 1 F 1 F represents the coverage of the first particles in any 25μm × 19μm area on the surface of the first polymer coating. 2 M represents the coverage of the second particles in any 25μm × 19μm area on the surface of the second polymer coating. 1 The coverage of the recess on the surface of the negative electrode sheet.

[0008] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0009] In the battery of this invention, the polymer coatings on both sides of the separator contain different coverage rates of acrylate polymer particles. By controlling the coverage rate of the first particles in the first polymer coating corresponding to the positive electrode to be less than the coverage rate of the second particles in the second polymer coating corresponding to the negative electrode, the adhesion strength between the negative electrode and the separator can be made greater than that between the positive electrode and the separator. This improves the adhesion strength between the negative electrode and the separator, allowing the separator and the negative electrode to maintain good adhesion under the volume change stress of the negative electrode. This reduces the risk of negative electrode misalignment and electrode assembly deformation during long-cycle operation at room temperature, thereby improving the battery's long-cycle performance at room temperature. While ensuring adequate adhesion strength between the positive electrode and the separator, reducing the relative adhesion strength between the positive electrode and the separator compared to the negative electrode and the separator provides more buffer space for the positive electrode when subjected to external stress and / or internal expansion stress. It also releases shear stress inside the battery, thereby preventing permanent detachment of the interface between the electrode and the separator due to the continuous accumulation of shear stress. This further reduces the risk of electrode assembly deformation, lowers the battery's room temperature long-cycle impedance, and this stress buffering and release effect can reduce the fragmentation of electrode active particles during high-temperature cycling, improving the battery's high-temperature cycle performance.

[0010] To balance the bonding strength between the negative electrode and the separator, and the interfacial heat dissipation, this invention also controls the battery to satisfy the relationship: 0.1≤M 1 / F 3 ≤1.2, which enables the battery to maintain a high bonding strength between the negative electrode and the separator while providing a heat dissipation channel for the negative electrode, improving the battery's furnace temperature safety performance, and enabling the battery to have both high high temperature cycle performance and high furnace temperature safety performance.

[0011] Other features and advantages of the present invention will be described in detail in the following detailed description section.

[0012] 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

[0013] Figure 1 The diagram shown is one of the structural schematic diagrams of the separator in the battery of the present invention.

[0014] Figure 2 The diagram shown is a second schematic representation of the separator structure in the battery of the present invention.

[0015] Figure 3 The third schematic diagram shows the structure of the separator in the battery of the present invention.

[0016] Figure 4 The image shown is a SEM image of the first polymer coating in the separator of the battery according to the present invention.

[0017] Figure 5 The image shown is a SEM image of the second polymer coating in the separator of the battery according to the present invention. Detailed Implementation

[0018] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the invention. Unless otherwise specified herein, data ranges include endpoints.

[0019] It should be noted that the numerical designations such as "first" and "second" in this invention are only used to distinguish different substances or methods of use, and do not represent a difference in order.

[0020] This invention provides a battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive and negative electrodes. The separator includes a carrier layer and polymer coatings on both sides of the carrier layer. In the separator, the polymer coating corresponding to the positive electrode is a first polymer coating, and the polymer coating corresponding to the negative electrode is a second polymer coating. The first polymer coating includes first particles dispersedly distributed, the first particles being composed of acrylate polymers. The second polymer coating includes second particles dispersedly distributed, the second particles being composed of acrylate polymers. A recess is provided on the surface of the negative electrode.

[0021] The battery satisfies the following relationship: F 1 <F 2 , 0.1≤M 1 / F 3 ≤1.2 (e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, or 1.2), where F 3 =F 2 -F 1 F 1 F represents the coverage of the first particles in any 25μm × 19μm area on the surface of the first polymer coating. 2 M represents the coverage of the second particles in any 25μm × 19μm area on the surface of the second polymer coating. 1 The coverage of the recess on the surface of the negative electrode sheet.

[0022] like Figure 1 , Figure 2 and Figure 3 As shown, the separator 1 includes a carrier layer 11 and polymer coatings located on both sides of the carrier layer 11. In the separator 1, the polymer coating corresponding to the positive electrode is a first polymer coating 121, and the polymer coating corresponding to the negative electrode is a second polymer coating 122.

[0023] In this invention, such as Figure 4 As shown, the first polymer coating includes first particles that are dispersedly distributed, wherein the particles within the red dashed circles are the first particles. It can be understood that dispersed distribution means that the first particles are dispersedly distributed within the first polymer coating, and that in the thickness direction X of the membrane, the first particles comprise only one layer or multiple layers in the first polymer coating, without the formation of large-size agglomerates. Similarly, as... Figure 5 As shown, the second polymer coating includes second particles that are dispersedly distributed. This means that the first particles are dispersedly distributed in the first polymer coating, and in the thickness direction X of the membrane, the second particles are only one layer or multiple layers in the second polymer coating, and no large-size agglomerates appear.

[0024] In this invention, the coverage rate F of the first particles in any 25μm × 19μm area on the surface of the first polymer coating is... 1 "F" refers to the ratio of the sum of the projected areas of the first particles on the carrier layer surface to the area of ​​any 25μm × 19μm area on the surface of the first polymer coating. "F" also refers to the coverage rate F of the second particles in any 25μm × 19μm area on the surface of the second polymer coating. 2 , refers to the ratio of the sum of the orthographic projection areas of the second particles on the surface of the carrier layer to the area of ​​any 25μm×19μm area on the surface of the second polymer coating.

[0025] In this invention, the coverage rate F of the first particles in any 25μm × 19μm area on the surface of the first polymer coating is defined as follows: 1 "and "the coverage F of the second particles in any 25μm × 19μm area on the surface of the second polymer coating" 2 "All of these can be obtained through the following test method, specifically, by measuring the coverage rate F of the first particles in any 25μm × 19μm area on the surface of the first polymer coating." 1For example, using SEM to obtain an image of the surface of the first polymer coating, a 25μm × 19μm area is randomly selected from the image and divided into 50 × 38 uniform squares. If the area covered by the orthographic projection of the first particle in a square exceeds half the area of ​​the square, it means that the square is occupied by the first particle; otherwise, it means that the square is not occupied by the first particle. By counting the number of squares occupied by the first particle, the total number of squares occupied by the first particle is recorded as X. Then, the coverage rate = (X / (50 × 38)) × 100%. Repeat the above operation 5 times, and take the average of the 5 times as the coverage rate of the first particle. It should be noted that the first polymer coating includes coated areas and uncoated areas, and any 25μm × 19μm area is any coated area in the first polymer coating. Similarly, the second polymer coating includes coated areas and uncoated areas, and any 25μm × 19μm area is any coated area in the second polymer coating.

[0026] Research has found that when the interfacial adhesion strength between the separator and the electrodes (including positive and negative electrodes) is too high, the gas permeability of the separator, the electrolyte wettability at the separator-electrode interface, and the heat dissipation of the battery will be affected to some extent. Furthermore, during battery cycling, the volume expansion of the positive electrode is smaller than that of the negative electrode, increasing the risk of misalignment of the negative electrode and deformation of the electrode assembly. Therefore, the increase in the interfacial adhesion strength of the negative electrode needs to be greater than that of the positive electrode. If the increase in the interfacial adhesion strength of the negative electrode is the same as that of the positive electrode, then when the interfacial adhesion strength of the positive electrode is appropriate, the interfacial adhesion strength of the negative electrode will be low, resulting in poor or negligible improvement in mitigating misalignment between the separator and the negative electrode, affecting the battery's long-term cycling performance at room temperature and high-temperature cycling performance. Conversely, when the interfacial adhesion strength of the negative electrode is appropriate, the interfacial adhesion strength of the positive electrode will be excessive, affecting the electrolyte wettability at the positive electrode interface and the heat dissipation of the battery, thus impacting the battery's kinetic performance and high-temperature safety performance. Therefore, in order to improve the air permeability of the positive electrode side separator, the electrolyte wetting at the interface between the separator and the positive electrode, and the heat dissipation of the battery while ensuring adequate adhesion between the positive electrode and the separator, and simultaneously ensuring strong interfacial adhesion between the negative electrode and the separator to reduce the risk of negative electrode misalignment and electrode assembly deformation, the battery of this invention controls the coverage F of the first particles comprising polypropylene ester polymers in the first polymer coating of the separator corresponding to the positive and negative electrodes, respectively. 1 The coverage F of the second particles in the second polymer coating, which includes polyacrylate polymers. 2 Satisfying relation F 1 <F 2Furthermore, a first polymer coating with a lower coverage of first particles is associated with the positive electrode, and a second polymer coating with a higher coverage of second particles is associated with the negative electrode.

[0027] The diaphragm is controlled to satisfy the following relationship: F 1 <F 2 On the one hand, the first polymer coating corresponding to the positive electrode sheet has a low coverage of first particles containing polyacrylate polymers, which can improve the air permeability of the positive electrode side separator, the electrolyte wetting at the interface between the separator and the positive electrode sheet, and the heat dissipation of the battery while ensuring that the positive electrode sheet and the separator maintain appropriate adhesion. On the other hand, the second polymer coating corresponding to the negative electrode sheet has a high coverage of second particles containing polyacrylate polymers, which can make the separator and the negative electrode sheet form a stronger bond strength, ensuring that the interfacial bond strength between the negative electrode sheet and the separator can prevent the separator and the negative electrode sheet from separating under the volume change stress of the negative electrode. This can reduce the risk of misalignment of the negative electrode sheet and deformation of the electrode assembly during long-term cycling at room temperature, thereby reducing the cycle impedance of the battery and improving the long-term cycling performance of the battery at room temperature. On the other hand, when subjected to shear forces generated during battery cycling, the high adhesion between the negative electrode and the separator can maintain the stability of the interface between them. The relatively weaker adhesion between the positive electrode and the separator allows for the release of internal shear stress through local fine-tuning. This prevents permanent detachment of the interface between the electrode and the separator due to the continuous accumulation of shear stress, which would cause deformation of the electrode assembly and reduce the battery's long-cycle impedance at room temperature. Furthermore, it can prevent the current collector from breaking due to the continuous accumulation of shear stress, thus improving the battery's safety performance. This stress buffering and release effect can also reduce the fragmentation of electrode active particles during high-temperature cycling, thereby reducing the battery's high-temperature cycling performance. This allows the battery to have both high long-cycle performance at room temperature and low high-temperature cycling performance.

[0028] Meanwhile, to improve heat dissipation at the interface between the negative electrode and the separator, a recess is provided on the surface of the negative electrode. This recess facilitates heat dissipation on the negative electrode side, improving the battery's furnace temperature safety performance. It also helps increase the electrolyte content at the interface between the negative electrode and the separator. However, the recess affects the adhesion strength between the negative electrode and the separator. To balance the adhesion and heat dissipation between the negative electrode and the separator, this invention simultaneously controls the battery to satisfy the relationship: 0.1 ≤ M 1 / F 3A value ≤1.2 allows for the provision of a heat dissipation channel for the negative electrode without affecting the bonding strength between the negative electrode and the separator. This facilitates the dissipation of internal heat, improves the battery's furnace temperature safety (high-temperature safety performance), and achieves a better balance between the bonding strength between the negative electrode and the separator and the heat dissipation at the interface. Simultaneously, increasing the electrolyte content at the interface between the negative electrode and the separator allows the battery to achieve both high room-temperature long-cycle performance and high-temperature safety performance. When M... 1 / F 3 When M < 0.1, the difference between the coverage of the concave portion on the negative electrode surface and the coverage of polymer particles in the polymer coating is insufficient, which cannot effectively compensate for the heat accumulation caused by excessive adhesion, and is not conducive to improving the furnace temperature safety performance of the battery; when M 1 / F 3 When the value is greater than 1.2, the difference between the coverage of the concave part on the surface of the negative electrode and the coverage of the polymer particles in the polymer coating is too large. The heat dissipation is greater than the heat accumulation caused by excessive adhesion, which is not conducive to the adhesion between the separator and the negative electrode, and is not conducive to reducing the room temperature long cycle impedance of the battery, thus affecting the room temperature long cycle performance of the battery.

[0029] In this invention, by controlling the relationship between the coverage rates of the first and second acrylate polymer particles in the polymer coating on both sides of the separator, and the relationship between the difference between the two and the coverage rate of the concave portion on the surface of the negative electrode sheet, compared with the prior art, it is possible to effectively improve the problem of poor structural stability of the electrode assembly caused by volume changes of the negative electrode active material (especially silicon-based material), and the difficulty in simultaneously achieving long-cycle performance and high-temperature safety performance. This allows the battery to possess both high high-temperature cycle performance and high furnace temperature safety performance. To further improve the effect, one or more of the technical features can be further optimized.

[0030] In some examples, the acrylate polymer includes one or more of the following: polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, acrylate monomer-acrylonitrile copolymer, styrene-acrylate monomer copolymer, acrylate monomer-acrylonitrile-ethylene copolymer, styrene-acrylate monomer-acrylonitrile copolymer, acrylate monomer-ethylene copolymer, ethylhexyl acrylate-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, methyl acrylate-N,N-dimethylacrylamide copolymer, ethyl acrylate-2-(diethylamino)ethyl acrylate copolymer, ethyl acrylate-N,N-diethylacrylamide copolymer, and ethyl acrylate-2-(diethylamino)ethyl acrylate.

[0031] In some instances, the acrylate monomers include one or more of methyl methacrylate, butyl acrylate, n-propyl acrylate, octyl acrylate, ethyl methacrylate, isooctyl acrylate, octadecyl acrylate, ethyl acrylate, cyclohexyl acrylate, and 2-hydroxyethyl acrylate.

[0032] In some instances, the battery satisfies the following relationship: F 1 <F 2 0.3≤M 1 / F 3 ≤0.95 (e.g., 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 0.95).

[0033] In some instances, F 1 The range is 4%-35% (e.g., 4%, 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, or 35%).

[0034] In some instances, F 2 It ranges from 10% to 45% (e.g., 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43%, or 45%).

[0035] In some instances, F 3 The range is 8%-35% (e.g., 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, or 35%).

[0036] In some instances, F 3 It ranges from 10% to 25%.

[0037] In some specific implementations, F 1 It ranges from 4% to 35%, F 2 It ranges from 10% to 45%, F 3 =F 2 -F 1 F 3 It ranges from 8% to 35%.

[0038] In some specific implementations, F 1 It ranges from 4% to 35%, F 2 It ranges from 10% to 45%, F 3 =F 2 -F 1 F 3 It ranges from 10% to 25%.

[0039] In some instances, M 1It ranges from 3% to 17% (e.g., 3%, 5%, 8%, 10%, 13%, 15% or 17%).

[0040] In some instances, M 1 It ranges from 5% to 11%.

[0041] In some specific implementations, F 3 It ranges from 8% to 35%, M 1 It ranges from 3% to 17%, F 1 It ranges from 4% to 35%, F 2 The battery's capacity is 10%-45%, and it satisfies the following relationship: F 1 <F 2 , 0.1≤M 1 / F 3 ≤1.2, where F 3 =F 2 -F 1 .

[0042] In some specific implementations, F 3 It is 10%-25%, M 1 It is 5%-11%, F 1 It ranges from 4% to 35%, F 2 The battery's capacity is 10%-45%, and it satisfies the following relationship: F 1 <F 2 0.3≤M 1 / F 3 ≤0.95, where F 3 =F 2 -F 1 .

[0043] In some instances, the first polymer coating includes a coated area and an uncoated area, with the first particle located in the coated area.

[0044] In some instances, the second polymer coating includes a coated area and an uncoated area, with the second particle located in the coated area.

[0045] In some instances, the coverage of the first polymer coating on the surface of the carrier layer is the same as or different from the coverage of the second polymer coating on the surface of the carrier layer.

[0046] In some instances, the first polymer coating covers 10%-45% of the surface of the carrier layer (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40% or 45%).

[0047] In some instances, the first polymer coating has a coverage of 18%-28% on the surface of the carrier layer.

[0048] In some instances, the second polymer coating covers 10%-45% of the surface of the carrier layer (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40% or 45%).

[0049] In some instances, the second polymer coating has a coverage of 18%-28% on the surface of the carrier layer.

[0050] In this invention, the coverage rate of the first polymer coating on the carrier layer surface refers to the ratio of the area of ​​the orthographic projection of the first polymer coating on the carrier layer surface to the total area of ​​the carrier layer surface; the coverage rate of the second polymer coating on the carrier layer surface refers to the ratio of the area of ​​the orthographic projection of the second polymer coating on the carrier layer surface to the total area of ​​the carrier layer surface. In this invention, the coverage rates of the first and second polymer coatings on the carrier layer surface can be obtained by testing using the following method. Specifically, taking the "coverage rate of the first polymer coating on the carrier layer surface" as an example, a 6cm × 6cm membrane sample is taken, and the membrane is stained and permeated with dye penetrant DPT-5 in a fume hood. After the membrane surface is air-dried, the membrane sample is taken out and observed under a 3D ultra-depth-of-field microscope. The magnification is adjusted to 50X, and the area (particle counting) is automatically measured using system software. This yields the measured value of the coverage rate of the first polymer coating on the carrier layer surface. This operation is repeated 10 times, and the average value of the 10 measurements is the coverage rate of the first polymer coating on the carrier layer surface.

[0051] In some instances, the first particle and the second particle may be the same or different. In this invention, the first particle and the second particle being different means that one or more of the following are completely different: particle composition, particle size, and particle mass swelling degree.

[0052] In some instances, the average particle size of the first particle is 0.5 μm to 1.2 μm (e.g., 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1 μm, 1.05 μm, 1.1 μm, 1.15 μm, 1.2 μm or within any two of the above values).

[0053] In some instances, the average particle size of the first particle is 0.65 μm to 0.95 μm.

[0054] In some instances, the average particle size of the second particle is 0.5 μm to 1.2 μm (e.g., 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1 μm, 1.05 μm, 1.1 μm, 1.15 μm, 1.2 μm or within any two of the above values).

[0055] In some instances, the average particle size of the second particle is 0.65 μm to 0.95 μm.

[0056] In this invention, the average particle size of the first particle and the average particle size of the second particle can be obtained by testing using the following methods. Specifically, taking the average particle size of the first particle as an example, in the SEM image of the surface of the first polymer coating, arbitrarily select a 100μm×100μm area, and measure the particle size of 100 randomly selected first particles using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.). The average particle size of the 100 first particles is the average particle size of the first particle. It is understood that if no 100 first particles are observed in the image, multiple images are taken, and the average of the total particle sizes of the 100 first particles is taken as the average particle size.

[0057] In some instances, the Dv90 of the first particle is 0.65 μm to 4.5 μm (e.g., 0.65 μm, 0.8 μm, 1 μm, 1.3 μm, 1.5 μm, 1.8 μm, 2 μm, 2.3 μm, 2.5 μm, 2.8 μm, 3 μm, 3.3 μm, 3.5 μm, 3.8 μm, 4 μm, 4.3 μm, or 4.5 μm).

[0058] In this invention, the Dv90 of the first particle is the particle size corresponding to 90% of the cumulative particle size distribution in the volumetric particle size distribution of the first particle. In this invention, the volumetric particle size distribution of the first particle can be obtained by arbitrarily selecting a 100μm × 100μm area in the SEM image of the first polymer coating surface, and then measuring and statistically processing it using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.). The Dv90 of the first particle can also be obtained by testing with a laser particle size analyzer; for example, before preparing the diaphragm, the Dv90 of the first particle can be measured using a laser particle size analyzer.

[0059] In some instances, the first particle was soaked in 2,2-difluoroethyl acetic acid for 4 hours at 90°C, and the mass swelling of the first particle was greater than 70%.

[0060] In some instances, the first particles are soaked in 2,2-difluoroethyl acetate for 4 hours at 90°C, and the mass swelling of the first particles is 71%-180% (e.g., 71%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, 125%, 130%, 135%, 140%, 145%, 150%, 155%, 160%, 165%, 170%, 175%, or 180%).

[0061] In some instances, the second particle was soaked in 2,2-difluoroethyl acetic acid for 4 hours at 90°C, and the mass swelling degree of the second particle was greater than 70%.

[0062] In some instances, the second particle is soaked in 2,2-difluoroethyl acetate for 4 hours at 90°C, and the mass swelling of the second particle is 71%-180% (e.g., 71%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, 125%, 130%, 135%, 140%, 145%, 150%, 155%, 160%, 165%, 170%, 175%, or 180%).

[0063] In some instances, the first polymer coating further includes third particles, which are agglomerated particles. For example... Figure 4 As shown, the particle within the blue solid circle is the third particle.

[0064] In some instances, the second polymer coating does not include a third particle.

[0065] According to some specific embodiments, the first polymer coating further includes a third particle, and the second polymer coating does not include the third particle.

[0066] In some instances, the composition of the third particle includes one or more of the following: polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polyhexafluoropropylene, fluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, acrylate monomer-acrylonitrile copolymer, styrene-acrylate monomer copolymer, acrylate monomer-acrylonitrile-ethylene copolymer, acrylate monomer-ethylene copolymer, styrene-acrylate monomer-acrylonitrile copolymer, ethylhexyl acrylate-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, methyl acrylate-N,N-dimethylacrylamide copolymer, ethyl acrylate-2-(diethylamino)ethyl acrylate copolymer, ethyl acrylate-N,N-diethylacrylamide copolymer, and ethyl acrylate-2-(diethylamino)ethyl acrylate.

[0067] In some instances, the acrylate monomers include one or more of methyl methacrylate, butyl acrylate, n-propyl acrylate, octyl acrylate, ethyl methacrylate, isooctyl acrylate, octadecyl acrylate, ethyl acrylate, cyclohexyl acrylate, and 2-hydroxyethyl acrylate.

[0068] In some instances, the third particle comprises secondary particles agglomerated from primary particles. The average particle size of the primary particles is 0.15 μm–0.25 μm (e.g., 0.15 μm, 0.16 μm, 0.17 μm, 0.18 μm, 0.19 μm, 0.2 μm, 0.21 μm, 0.22 μm, 0.23 μm, 0.24 μm, or 0.25 μm).

[0069] In some instances, the average particle size of the secondary particles of the third particle is 2 μm-20 μm (e.g., 2 μm, 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 17 μm or 20 μm).

[0070] In some instances, the average particle size of the secondary particles of the third particle is 3.5 μm-18 μm.

[0071] In this invention, the secondary particles of the third particle are formed by the aggregation of at least 5 primary particles. The average particle size of the secondary particles of the third particle can be determined by the following method: An image of the surface of the first polymer coating is obtained using SEM. On the scanned image, a square or rectangle with the smallest area completely surrounding one secondary particle of the third particle is drawn, i.e., a square or rectangle whose edge of the secondary particle of the third particle meets the four sides of the square or rectangle. The length of one side of the square or the length of the long side of the rectangle is the particle size of the secondary particle of the third particle. An area of ​​100μm × 100μm is arbitrarily selected on the surface of the first polymer coating, and the average particle size of any 50 secondary particles of the third particle is taken as the average particle size. This operation is repeated 5 times, and the average value is taken as the average particle size of the secondary particles of the third particle. It should be noted that if 50 secondary particles of the third particle can be observed in the captured image, the average particle size of any 50 secondary particles of the third particle in the image is taken as the average particle size of the secondary particles of the third particle. If no 50 secondary particles of the third particle are observed in the image, multiple images are captured, and the average particle size of a total of 50 secondary particles of the third particle is taken as the average particle size.

[0072] In some instances, the diaphragm satisfies the following relationship: 1.5 ≤ d 1 / d 2 ≤25 (e.g., 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25), where d 1 The average particle size of the secondary particles of the third particle is expressed in μm and d. 2 The Dv90 of the first particle is given in μm. Controlling the separator to satisfy the above relationship prevents excessive swelling of the first polymer coating at room temperature, improving its mechanical stability and reducing the battery's impedance during long-cycle operation at room temperature. Furthermore, it creates a certain gap at the interface between the positive electrode and the separator, improving electrolyte wettability and electrolyte content, further enhancing heat dissipation at the separator-positive electrode interface, and further improving the battery's high-temperature safety performance.

[0073] In some instances, the diaphragm satisfies the following relationship: 4≤d 1 / d 2 ≤20.

[0074] In some specific implementations, d 1 For 2-20, d 2 The diaphragm has a value between 0.65 and 4.5, and satisfies the following relationship: 1.5 ≤ d 1 / d2 ≤25.

[0075] In some specific implementations, d 1 It is 3.5-18, d 2 The diaphragm has a value between 0.65 and 4.5, and satisfies the following relationship: 4 ≤ d 1 / d 2 ≤20.

[0076] In some instances, the third particle is soaked in 2,2-difluoroethyl acetate at 90°C for 4 hours, and the mass swelling of the third particle is less than 40% (e.g., 39%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 1%, 0.5%, 0.1%, or 0%).

[0077] In this invention, the mass swelling degree can be obtained by testing it using the following method: Taking "the mass swelling degree of the third particle after soaking in 2,2-difluoroethyl acetic acid for 4 hours at 90°C" as an example, the third particle is poured into the mold and dried to form a plastic block; the plastic block of the second particle is weighed and recorded as M. 1 The solution was injected into 2,2-difluoroethyl acetate, ensuring the acetate completely submerged the gel block. The oven temperature was set to 90°C, and the system of the third gel block and 2,2-difluoroethyl acetate was heated for 4 hours to allow the third gel block to fully swell. After the set time, the residual electrolyte on the surface of the third gel block was wiped dry, and the weight was recorded as M. 2 The swelling degree of the third granular adhesive block is calculated using the following formula: S=[(M 2 -M 1 ) / M 1 ]×100%.

[0078] In this invention, the bonding strength between the third particle and the electrode sheet is less than the bonding strength between the first particle and the electrode sheet, and the bonding strength between the third particle and the electrode sheet is less than the bonding strength between the second particle and the electrode sheet. The bonding strength can be determined by the following method: The test coverage rate is F... 1 The adhesion strength Z of the coating containing only the third particle to the electrode sheet. 1 The test coverage rate is F 1 The adhesion strength Z of the coating containing only the first or second particle to the electrode. 2 If Z 2 >Z 1 If the adhesion strength of the third particle to the electrode is less than that of the first particle to the electrode, and the adhesion strength of the third particle to the electrode is less than that of the second particle to the electrode, then the adhesion strength is considered to be less than that of the first particle to the electrode. The adhesion strength can also be determined by the following method: The test coverage is F... 1The adhesion strength Z of the coating containing only the third and first particles to the electrode sheet. 1 The test coverage rate is F 1 The adhesion strength Z of the coating containing only the first particle to the electrode sheet. 2 If Z 2 >Z 1 If the bonding strength between the third particle and the electrode is less than that between the first particle and the electrode, then it is considered that the bonding strength between the third particle and the electrode is less than that between the first particle and the electrode.

[0079] In some instances, the adhesion strength between the first polymer coating and the positive electrode is 6 N / m to 20 N / m.

[0080] In some instances, the adhesion strength between the second polymer coating and the negative electrode sheet is 8 N / m to 30 N / m.

[0081] In this invention, the adhesion strength between the first polymer coating and the positive electrode is less than the adhesion strength between the second polymer coating and the negative electrode.

[0082] In this invention, the adhesive strength can be tested using the following method: A strip of diaphragm and electrode (positive or negative electrode) composite material, 200mm long and 20mm wide, is cut. The cut strip is fixed to a steel plate with double-sided adhesive, ensuring the diaphragm is in contact with the steel plate. It is then rolled once with a 2kg roller. A universal tensile testing machine is used, with the upper clamp holding the electrode and the lower clamp holding the steel plate, to perform a 180° peel test at a speed of 100mm / min and a displacement distance of 100mm. The average peel force (in N) is obtained during the test. The peel strength is the average peel strength (in N / m), where average peel strength = average peel force / tape width.

[0083] In some instances, the carrier layer includes a substrate layer and optionally ("optionally" means that it may not be present) a heat-resistant layer located on one or both sides of the surface of the substrate layer.

[0084] In some instances, the substrate layer comprises one or more of polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalate), poly(m-phenylene isophthalate), or polymer derivatives thereof.

[0085] In some instances, the pore size of the substrate layer is 25nm-50nm (e.g., 25nm, 28nm, 30nm, 33nm, 35nm, 38nm, 40nm, 43nm, 45nm, 48nm or 50nm).

[0086] In some instances, the thickness of the substrate layer is 3 μm to 10 μm (e.g., 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm or 10 μm).

[0087] In some instances, the heat-resistant particles are composed of one or more of the following: boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium dioxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride, 1,3,5-triazine-2,4,6-triamine, melamine thiocyanate, melamine cyanurate, symmetrical triaminotriazine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, 2,4,6-tris(2-pyridyl)triazine, 2-amino-4,6-methoxy-1,3,5-triazine, lithium aluminum titanium phosphate, uracil, cytosine, guanine, 4-amino-2,6-dihydroxypyrimidine, phenolic resin, cellulose, and benzimidazole compounds.

[0088] In some instances, the benzimidazole compound is 2-mercaptobenzimidazole or a 2-mercaptobenzimidazole derivative, wherein the 2-mercaptobenzimidazole derivative includes 2-mercapto-5-methylbenzimidazole, 2-mercapto-5-ethylbenzimidazole, 2-mercapto-5-propylbenzimidazole, 2-mercapto-5-methoxybenzimidazole, 2-mercapto-5-ethoxybenzimidazole, 2-mercapto-5-hydroxybenzimidazole, 2-mercapto-5-aminobenzimidazole, 2-mercapto-5-chlorobenzimidazole, 2-mercapto-5-bromobenzimidazole, and 2... One or more of the following compounds are selected: 2-mercapto-5-sulfonic acid benzimidazole, 2-mercapto-5-carboxybenzimidazole, 2-mercapto-5-nitrobenzimidazole, 2-mercapto-5-fluorobenzimidazole, 2-mercapto-5-fluorobenzimidazole, 2-mercapto-5,6-dichlorobenzimidazole, 2-mercapto-5-cyanobenzimidazole, lithium salt of 2-thiolbenzimidazole, sodium salt of 2-thiolbenzimidazole, potassium salt of 2-thiolbenzimidazole, calcium salt of 2-thiolbenzimidazole, magnesium salt of 2-thiolbenzimidazole, aluminum salt of 2-thiolbenzimidazole, and ammonium salt of 2-thiolbenzimidazole. These benzimidazole compounds contain polar groups such as mercapto (-SH), secondary amino (NH), and pyridine nitrogen atoms (N=). These polar groups give the separator good electrolyte wettability, which can further improve the rate performance of the battery at room temperature.

[0089] In some instances, the Dv50 of the heat-resistant particles is 0.1 μm-1.5 μm (e.g., 0.1 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 1.3 μm, or 1.5 μm). This can improve the density and flexibility of the heat-resistant layer, enhance the adhesion between the separator and the electrode, strengthen the heat resistance of the separator, and allow the heat-resistant layer to have suitable porosity, further improving the high-temperature safety performance of the battery without affecting the overall lithium-ion permeability of the separator.

[0090] In this invention, the Dv50 of the heat-resistant particles is the particle size corresponding to the cumulative particle size distribution reaching 50% in the volumetric particle size distribution of the heat-resistant particles. In this invention, the volumetric particle size distribution of the heat-resistant particles can be obtained by arbitrarily selecting a 100μm × 100μm area in the SEM image of the heat-resistant layer surface, and then measuring and statistically processing it using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.). The Dv50 of the heat-resistant particles can also be obtained by testing with a laser particle size analyzer; for example, before preparing the diaphragm, the Dv50 of the heat-resistant particles can be measured using a laser particle size analyzer.

[0091] In some instances, the thickness of the heat-resistant layer is 0.3 μm to 4.5 μm (e.g., 0.3 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or 4.5 μm).

[0092] In some instances, the heat-resistant layer comprises heat-resistant particles and a first binder.

[0093] In some instances, the first adhesive comprises one or more of the following: polyvinyl alcohol, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinylpyrrolidone, acrylate adhesives, styrene-acrylic latex, polyacrylonitrile, polyvinyl acetate, polyacrylic acid, polyurethane, polyurethane-modified polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, or copolymer systems derived from the above polymers.

[0094] In some examples, the acrylate adhesive includes one or more of the following: polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, acrylate monomer-acrylonitrile copolymer, styrene-acrylate monomer copolymer, acrylate monomer-acrylonitrile-ethylene copolymer, styrene-acrylate monomer-acrylonitrile copolymer, acrylate monomer-ethylene copolymer, ethylhexyl acrylate-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, methyl acrylate-N,N-dimethylacrylamide copolymer, ethyl acrylate-2-(diethylamino)ethyl acrylate copolymer, ethyl acrylate-N,N-diethylacrylamide copolymer, and ethyl acrylate-2-(diethylamino)ethyl acrylate.

[0095] In some instances, the acrylate monomers include one or more of methyl methacrylate, butyl acrylate, n-propyl acrylate, octyl acrylate, ethyl methacrylate, isooctyl acrylate, octadecyl acrylate, ethyl acrylate, cyclohexyl acrylate, and 2-hydroxyethyl acrylate.

[0096] In some instances, the heat-resistant particles account for 90%-99% of the total weight of the heat-resistant layer (e.g., 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%), and the first adhesive accounts for 1%-10% of the total weight of the heat-resistant layer (e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%).

[0097] In some instances, the diaphragm has a heat shrinkage rate of less than 10% when baked at 130°C for 1 hour in the stretching direction (length direction) (e.g., 9.9%, 9.5%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or 0.5%).

[0098] In some instances, the diaphragm has a heat shrinkage rate of less than 10% when baked at 130°C for 1 hour perpendicular to the stretching direction (e.g., 9.9%, 9.5%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or 0.5%).

[0099] In this invention, the thermal shrinkage rate of the separator in the stretching direction and the thermal shrinkage rate of the separator perpendicular to the stretching direction can be obtained by referring to the standard "GB / T-36363-2018 Polyolefin Separator for Lithium-ion Batteries".

[0100] In some instances, the diaphragm has a permeability of 60 s / 100cc to 350 s / 100cc (e.g., 60 s / 100cc, 80 s / 100cc, 100 s / 100cc, 130 s / 100cc, 150 s / 100cc, 180 s / 100cc, 200 s / 100cc, 230 s / 100cc, 250 s / 100cc, 280 s / 100cc, 300 s / 100cc, 330 s / 100cc, or 350 s / 100cc). In this invention, the air permeability value is defined according to the standard GB / T 36363-2018. The air permeability value indicates that, under normal temperature, humidity, and pressure conditions, and with the testing instrument applying a pressure of 1.21 kPa, the area through which 100 mL of air can pass is 6.45 cm². 2 The time required for the diaphragm to rupture. The applied pressure of 1.21 kPa is constant, and the distance traveled is 6.45 cm. 2 The area is a fixed area.

[0101] In some instances, the diaphragm has a puncture strength greater than 120 gf (e.g., 121 gf, 125 gf, 130 gf, 135 gf, 140 gf, 145 gf, 150 gf, 155 gf, 160 gf, 165 gf, 170 gf, 175 gf, 180 gf, 185 gf, 190 gf, 195 gf, or 200 gf).

[0102] In this invention, the puncture strength of the separator can be obtained by testing with reference to the standard GB / T-36363-2018 Polyolefin separator for lithium-ion batteries.

[0103] In some instances, the surface of the negative electrode may include a plurality of recesses. "A plurality of" means one or more, for example, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100.

[0104] In some instances, the morphology of the recess includes one or more of holes, lines, and grooves.

[0105] In some instances, the width of the recess is 55μm-185μm (e.g., 55μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, or 185μm). In this invention, the width of the recess refers to the maximum distance between any two points on the edge line of the recess. When the shape of the recess includes a hole, the width of the recess is the diameter of the hole. When the shape of the recess includes one or more of lines and grooves, the width of the recess refers to the average distance between the two long sides in the orthogonal projection of the line and groove onto the surface of the negative electrode sheet. For example, 10 points are randomly selected on any one of the long sides, the width corresponding to each point is measured, and the average value is taken as the average distance between the two long sides. When the number of recesses is greater than 1, the width of the recess is the average width. For example, when the number of recesses is less than or equal to 20, the width of the recess is the average width of all the recesses; when the number of recesses is greater than 20, the width of the recess is the average width of any 20 recesses.

[0106] In some instances, the depth of the recess is 5μm-35μm (e.g., 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, or 35μm). In this invention, the depth of the recess refers to the maximum vertical distance from any point at the bottom of the recess to the surface of the negative electrode sheet in the thickness direction of the negative electrode sheet. When the number of recesses is greater than 1, the depth of the recess is the average depth; for example, when the number of recesses is less than or equal to 20, the depth of the recess is the average depth of all recesses; when the number of recesses is greater than 20, the depth of the recess is the average depth of any 20 recesses.

[0107] In some instances, the spacing between adjacent recesses is 0.9mm-1.8mm (e.g., 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, or 1.8mm). In this invention, the spacing between adjacent recesses refers to the minimum distance between the edge lines of two adjacent recesses. When the number of recesses is greater than 2, the spacing between adjacent recesses is the average of the spacings between adjacent recesses. For example, when the number of recesses is less than or equal to 20, the spacing between adjacent recesses is the average of the spacings of all adjacent recesses; when the number of recesses is greater than 20, the spacing between adjacent recesses is the average of the spacings of any arbitrarily selected 20 adjacent recesses.

[0108] In this invention, the width of the recess, the depth of the recess, and the spacing between adjacent recesses can all be obtained by 3D profilometer or SEM testing.

[0109] In some instances, the negative electrode includes a negative current collector and a negative active layer located on one or both surfaces of the negative current collector, the negative active layer comprising a silicon-based material.

[0110] In some instances, the silicon-based material includes one or more of elemental silicon particles, silicon-oxygen particles, silicon-carbon particles, silicon-nitrogen particles, and silicon alloy particles.

[0111] In some instances, the average particle size of the silicon-carbon particles is 6 μm-10 μm (e.g., 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm or 10 μm).

[0112] In this invention, the average particle size of the silicon-carbon particles can be obtained by the following method: On the scanning image of the surface of the negative electrode active layer, draw the smallest square or rectangle that completely surrounds one silicon-carbon particle, that is, draw the square or rectangle whose edge of the silicon-carbon particle is connected to the four sides of the square or rectangle. The length of one side of the square or the length of the long side of the rectangle is the particle size of the silicon-carbon particle. The average particle size is the number of particle sizes of any 100 silicon-carbon particles on the surface of the positive electrode active layer. Repeat the above operation 5 times and take the average value as the average particle size of the silicon-carbon particles. It should be noted that when 100 silicon-carbon particles can be observed in the captured image, the average particle size of any 100 silicon-carbon particles in the image is taken as the average particle size of the silicon-carbon particles. When no 100 silicon-carbon particles are observed in the image, take multiple images and take the average particle size of the total 100 silicon-carbon particles as the average particle size. The average particle size of the silicon-carbon particles can also be obtained by testing with a laser particle size analyzer. For example, before preparing the negative electrode, the average particle size of the silicon-carbon particles can be obtained by measuring the silicon-carbon particles with a laser particle size analyzer.

[0113] In some instances, the weight percentage of silicon in the negative electrode active layer is 5%-50% (e.g., 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or within any two of the above values).

[0114] In some instances, the negative electrode active layer further includes a carbon-based material, a negative electrode conductive agent, and a negative electrode binder. The negative electrode conductive agent and the negative electrode binder can be conventional materials in the art.

[0115] In some instances, the carbon-based material includes one or more of artificial graphite and natural graphite.

[0116] In some instances, the electrolyte includes a fluorinated solvent. The fluorinated solvent can participate in the formation of the CEI film, resulting in a higher content of LiF in the CEI film. LiF possesses high mechanical strength and a certain degree of lithium-ion permeability, thereby improving the mechanical strength of the CEI film while maintaining its low impedance. This is beneficial for enhancing the stability of the positive electrode active material at high temperatures and further improving the high-temperature safety of the battery.

[0117] In some instances, the fluorinated solvent includes one or more of the following: fluoroethylene carbonate, difluoroethylene carbonate, 2,2-difluoroethyl acetate, ethyl 2,2-difluoroethyl acetate, ethyl monofluoroethyl acetate, monofluoroethyl acetate, trifluoroethyl acetate, propyl difluoroacetate, and difluoropropyl acetate.

[0118] In some instances, the weight percentage of the fluorinated solvent in the electrolyte is 10%-75% (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or 75%). Controlling the weight percentage of the fluorinated solvent in the electrolyte within the above range ensures low impedance of the CEI film, further enhances the mechanical strength of the CEI film, further improves the stability of the positive electrode active material at high temperatures, and further enhances the high-temperature safety of the battery.

[0119] In some instances, the fluorinated solvent accounts for 25%-60% by weight in the electrolyte.

[0120] In some examples, the fluorinated solvent includes ethyl difluorocarbonate and fluoroethylene carbonate (FEC), wherein the ethyl difluorocarbonate includes at least one of 2,2-difluoroethyl acetate and ethyl 2,2-difluorocarbonate. FEC can preferentially reduce on the surface of the negative electrode (especially silicon-based materials) to form a flexible, dense, and LiF-rich SEI film. This SEI film can effectively adapt to the large volume expansion of silicon-based materials, improving or even preventing repeated rupture and regeneration of the SEI film. This can effectively reduce electrolyte side reactions, thereby reducing the impact of electrolyte side reaction products on the stability of the positive electrode active material, and thus simultaneously improving the high-temperature stability of both the positive and negative electrode active materials. Ethyl difluorocarbonate can participate in the formation of the CEI film, resulting in a higher LiF content in the CEI film. LiF has high mechanical strength and certain lithium-ion permeability, thus improving the mechanical strength of the CEI film while maintaining its low impedance. This is beneficial for improving the stability of the positive electrode active material at high temperatures and can also reduce the viscosity of the electrolyte, improve heat dissipation at the separator-electrode interface, and further improve the high-temperature safety performance of the battery.

[0121] In some examples, the weight ratio of ethyl difluoroacetate to ethylene fluorocarbonate is 1-8.6 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, or 8.6). Controlling the weight ratio of ethyl difluoroacetate to ethylene fluorocarbonate in the electrolyte within this range ensures improved high-temperature stability of both the positive and negative electrode active materials while reducing electrolyte viscosity, improving heat dissipation at the separator-electrode interface, and further enhancing furnace temperature safety of the battery. When the weight ratio of ethyl difluoroacetate to ethylene fluorocarbonate is less than 1, the electrolyte viscosity is too high, which is detrimental to further improving interfacial heat dissipation between the separator and the electrode, and also detrimental to further improving the furnace temperature safety performance of the battery. When the weight ratio of ethyl difluoroacetate to ethylene fluorocarbonate is greater than 8.6, it is detrimental to FEC film formation on the negative electrode, and also detrimental to simultaneously improving the high-temperature stability of both the positive and negative electrode active materials.

[0122] In some instances, the weight ratio of the ethyl difluoroacetate to the weight of the fluoroethylene carbonate is 1.5-5.6.

[0123] In some instances, the ethyl difluoroacetate in the electrolyte comprises 5%-65% by weight (e.g., 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or 65%).

[0124] In some instances, the ethyl difluoroacetate comprises 20%-45% by weight in the electrolyte.

[0125] In some instances, the fluoroethylene carbonate in the electrolyte is 5%-25% by weight (e.g., 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23% or 25%).

[0126] In some instances, the fluoroethylene carbonate accounts for 8%-15% by weight in the electrolyte.

[0127] According to some specific embodiments, the weight percentage of ethyl difluorocarbonate in the electrolyte is 5%-65%, the weight percentage of fluoroethylene carbonate in the electrolyte is 5%-25%, and the weight ratio of ethyl difluorocarbonate to fluoroethylene carbonate is 1-8.6.

[0128] According to some specific embodiments, the weight percentage of ethyl difluorocarbonate in the electrolyte is 20%-45%, the weight percentage of fluoroethylene carbonate in the electrolyte is 8%-15%, and the weight ratio of ethyl difluorocarbonate to fluoroethylene carbonate is 1.5-5.6.

[0129] In some instances, the electrolyte includes lithium salts, organic solvents, and additives.

[0130] In some instances, the lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium difluorooxalate borate, lithium dioxalate borate, and lithium tetrafluorooxalate phosphate.

[0131] In some instances, the organic solvent includes one or more of the following, excluding fluorinated solvents: dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl formate (MF), methyl acetate (MA), methyl butyrate (MB), ethyl propionate (EP), propyl propionate (PP), ethyl butyrate, and propyl acetate.

[0132] In some instances, the additives include one or more of dinitrile compounds, trinitrile compounds, and sulfur-containing oxygen double bond compounds.

[0133] In some instances, based on the total weight of the electrolyte, the lithium salt accounts for 8%-20% by weight (e.g., 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%), the organic solvent accounts for 50%-80% by weight (e.g., 50%, 55%, 60%, 65%, 70%, 75%, or 80%), and the additives account for 0%-30% by weight (e.g., 0%, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, or 30%). When the weight percentage of the additives in the electrolyte is 0%, it indicates that the additives are not present in the electrolyte.

[0134] In this invention, the positive electrode sheet can be a conventional positive electrode sheet in the art. For example, 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 is not particularly limited and can include components such as positive active material, positive conductive agent, and positive binder according to conventional compositions in the art. The positive active material, positive conductive agent, and positive binder can all be conventional substances in the art. For example, the positive 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 conductive agent can be selected from one or more of conductive carbon black, carbon nanotubes, conductive graphite, and graphene; and the positive binder can be selected from one or more of polyvinylidene fluoride (PVDF), acrylic acid-modified PVDF, polyacrylate polymers, acrylic polymers, polytetrafluoroethylene, polyacrylonitrile, polyimide, styrene-butadiene rubber, and styrene-acrylic rubber.

[0135] In some instances, the battery is a lithium-ion rechargeable battery.

[0136] The application of the battery described in this invention is not particularly limited and can be used for a variety of known applications. Examples include: mobile computers, laptops, portable phones, e-book players, fax machines, copiers, printers, headphones, video recorders, LCD TVs, cleaners, calculators, tape recorders, radios, backup power supplies, automobiles, motorcycles, electric boats, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, cameras, large household batteries, energy storage power stations, etc.

[0137] The present invention will be described in detail below through embodiments. The embodiments described herein are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0138] The following examples illustrate the battery of the present invention.

[0139] Example 1

[0140] (1) Diaphragm

[0141] Heat-resistant particles (alumina) and a first binder (polyacrylic acid) are mixed in water and stirred thoroughly to obtain a mixed slurry with a solid content of 25%. The slurry has a 100% solid mass ratio of alumina to polyacrylic acid (by weight) of 96:4. The mixed slurry is coated onto one side of a substrate layer (polyethylene) using a gravure roller and dried in a multi-section oven at 60°C to form a heat-resistant layer with a thickness of 1 μm. The first particle (composed of methyl methacrylate-acrylonitrile copolymer) and the third particle (composed of vinylidene fluoride-hexafluoropropylene copolymer) are dispersed in a solvent water and stirred thoroughly to obtain a first slurry with a solid content of 10%. The first slurry is coated onto the surface of the heat-resistant layer using a gravure roller and dried in a multi-section oven at 60°C to form a first polymer coating. The second particle is dispersed in a solvent water and stirred thoroughly to obtain a second slurry with a solid content of 10%. The second slurry is coated onto the other side of the substrate layer using a gravure roller and dried in a multi-section oven at 60°C to form a second polymer coating.

[0142] (2) Positive electrode plate

[0143] Lithium cobalt oxide, polyvinylidene fluoride (PVDF 500) binder, and conductive material (SuperP: carbon nanotubes = 2:1) were mixed in N-methylpyrrolidone (NMP) solvent at a weight ratio of 96:2:2 and continuously stirred under the action of a stirrer to form a homogeneous and fluid positive electrode slurry. Subsequently, the positive electrode slurry was coated on both sides of an aluminum foil with a thickness of 10 μm and dried in a vacuum oven at 120°C for 6 hours. Then, it was rolled and slit to obtain the positive electrode sheet.

[0144] (3) Negative electrode plate

[0145] Graphite, silicon carbide (Dv50=8μm), conductive material (carbon black: carbon nanotubes=1:4), sodium carboxymethyl cellulose, and binder (styrene-butadiene rubber: polyurethane=1:2) were mixed in an aqueous solvent at a weight ratio of 85:10:1:0.5:3.5 and continuously stirred under the action of a stirrer to form a homogeneous and fluid negative electrode slurry. The slurry was then coated onto both sides of an 8μm thick copper current collector foil and dried in a vacuum oven at 120℃ for 6 hours. After rolling and slitting, the negative electrode sheet was obtained. Then, a high-energy laser scanning process was used to form a concave groove on the surface of the negative electrode sheet. The groove had a width of 96μm and a depth of 15μm.

[0146] (4) Electrolyte

[0147] In an argon-filled glove box (moisture <1 ppm, oxygen <1 ppm), 2,2-difluoroethyl acetate (DFEA), propylene carbonate (PC), propyl propionate (PP), and ethyl propionate (EP) were mixed in a mass ratio of 38:5:20:7 to form a homogeneous solvent. LiPF6, 1,4-dicyano-2-butene, and fluoroethylene carbonate were then slowly added and stirred until homogeneous to obtain the electrolyte. The electrolyte contained 16% LiPF6 by weight, 2% 1,4-dicyano-2-butene by weight, 12% fluoroethylene carbonate by weight, 38% DFEA by weight, and the weight ratio of ethyl difluoroethyl acetate to fluoroethylene carbonate was 3.17.

[0148] (5) Lithium-ion batteries

[0149] The positive electrode sheet obtained in step (2), the separator obtained in step (1), and the negative electrode sheet obtained in step (3) are wound together to form a bare battery cell. Then, the bare battery cell is placed in an aluminum-plastic film, and the electrolyte obtained in step (4) is injected into the dried bare battery cell. After vacuum sealing, room temperature standing, and high temperature formation, a lithium-ion battery is obtained. The positive electrode sheet corresponds to the first polymer coating, and the negative electrode sheet corresponds to the second polymer coating.

[0150] Example 2 group

[0151] This set of examples is used to illustrate when F is changed. 1 F 2 and M 1 Make M 1 / F 3 The impact of changes.

[0152] This embodiment is based on Embodiment 1, except that M is changed. 1 / F 3 See Table 1 for details.

[0153] Table 1

[0154]

[0155] Same 1 means same as Example 1.

[0156] Example 3 Group

[0157] This set of examples is used to illustrate when d is changed. 1 and d 2 Make d 1 / d 2 The effects of changes.

[0158] This embodiment group is carried out with reference to Embodiment 1, except that d is changed. 1 / d 2 See Table 2 for details.

[0159] Table 2

[0160]

[0161] Same 1 means same as Example 1.

[0162] Example 4 group

[0163] This set of examples illustrates the effects of changing the weight ratio of ethyl difluoroacetate to ethylene fluorocarbonate when the specific selection of the fluorinated solvent and the adjustment of at least one of the ratios of ethyl difluoroacetate and ethylene fluorocarbonate are altered.

[0164] This set of examples is based on Example 1, except that at least one of the following is changed: the specific selection of the fluorinated solvent and the weight ratio of ethyl difluoroacetate to ethylene fluorocarbonate. See Table 3 for details. In Example 4h, the weight ratio of ethyl difluoroacetate in the electrolyte is 10%, and in Example 4i, the weight ratio of ethyl difluoroacetate is 10%.

[0165] Table 3

[0166]

[0167] Same 1 means same as Example 1.

[0168] Example 5 group

[0169] This set of examples illustrates the effects that occur when one or more of the components of the first particle, the second particle, and the third particle are changed.

[0170] This embodiment is based on Embodiment 1, except that one or more of the components of the first particle, the second particle, and the third particle are changed, as detailed in Table 4.

[0171] Table 4

[0172]

[0173] Example 6

[0174] The process was carried out in accordance with Example 1, except that no third particle was added to the first polymer coating, and F 1 and F 2 The basic structure remains unchanged. The first polymer coating has a coverage of 6.9% on the carrier layer surface, and the second polymer coating has a coverage of 23% on the carrier layer surface.

[0175] Comparative Example 1

[0176] The procedure was carried out in accordance with Example 1, except that the components of the first particle and the second particle were both replaced with PVDF.

[0177] Comparative Example 2

[0178] The process is carried out in accordance with Example 1, except that the positive electrode corresponds to the second polymer coating and the negative electrode corresponds to the first polymer coating.

[0179] Comparative Example 3

[0180] The procedure is carried out in accordance with Example 1, except that F is changed. 1 F 2 and M 1 Make M 1 / F 3 The changes have been made; please refer to Table 5 for details.

[0181] Comparative Example 4

[0182] The procedure is carried out in accordance with Example 1, except that F is changed. 1 F 2 and M 1 Make M 1 / F 3 The changes have been made; please refer to Table 5 for details.

[0183] Table 5

[0184]

[0185] Same 1 means same as Example 1.

[0186] Comparative Example 5

[0187] The procedure is carried out in accordance with Example 1, except that the surface of the negative electrode does not have a recess.

[0188] Comparative Example 6

[0189] The procedure is carried out in accordance with Example 1, except that F is adjusted. 1 It is 23%, at this time F 2 -F 1 =0.

[0190] Test case

[0191] The batteries prepared in the examples and comparative examples were tested as follows.

[0192] 1. High-temperature cycling performance test

[0193] The lithium-ion battery was placed at 45℃±3℃, then charged at a constant current of 1 C to the upper limit voltage (4.5V), then charged at a constant voltage of 4.5V to 0.05C, and left to stand for 5 minutes; then discharged at a constant current of 0.5C to 3V, and the discharge capacity at this point was recorded as Q. 1 Let it rest for 5 minutes; this completes one charge-discharge cycle. Repeat this charge / discharge cycle 450 times, and record the discharge capacity Q of the lithium-ion battery after 450 cycles. 2 Then the capacity retention rate (%) = (Q 2 / Q 1 )×100%.

[0194] 2. Furnace temperature performance test

[0195] The lithium-ion batteries were heated in a convection air chamber at an initial temperature of (25±3)℃ with a temperature change rate of (5±2)℃ / min, and the temperature was increased to (130±1)℃. The temperature was maintained for 60 minutes before the test was ended. The battery status was recorded. 30 battery samples were tested for each example and comparative example. If the battery did not explode and / or catch fire, it was considered "passed". If it exploded or caught fire, it was considered "failed". 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 passed.

[0196] 3. Test of impedance change rate under ambient temperature cycling

[0197] The lithium-ion battery was transferred to a 25°C environment and allowed to stand for 30 minutes. It was then discharged at a constant current of 0.2C to 3.0V, allowed to stand for 5 minutes, charged at 0.5C to 4.5V, and then charged at a constant voltage to a cutoff current of 0.05C. After standing for 5 minutes, the initial fully charged state impedance value R was measured using an electrochemical workstation. 1 Then, discharge at a constant current of 0.7C to 3.0V, and then cycle 900T according to the following steps: charge at 0.5C to 4.5V, then charge at a constant voltage to the cutoff current of 0.05C, let stand for 5 minutes, and discharge at a constant current of 0.7C to 3.0V. After the cycle is completed, charge at 0.5C to 4.5V, then charge at a constant voltage to the cutoff current of 0.05C, let stand for 5 minutes, and use an electrochemical workstation to test the impedance value R of the fully charged state after the cycle. 2 The method for calculating the rate of change is: [(R 2 -R 1 ) / R 1 ]×100%.

[0198] 4. K-value test

[0199] At 25°C, the open-circuit potential of the lithium-ion batteries after sorting was measured to obtain V. 1 After standing for 24 hours, the open-circuit potential of the battery was measured again to obtain V. 2 , with V 1 Subtract V 2 The difference is then divided by the resting time to obtain the battery's K value.

[0200] The results are recorded in Table 6.

[0201] Table 6

[0202]

[0203] As can be seen from Table 6, by comparing the comparative example and the embodiment, the high-temperature cycle capacity retention rate of the battery in the embodiment is improved, the furnace temperature pass rate is significantly improved, the room temperature cycle impedance change rate is reduced, and the K value is reduced. This indicates that by controlling the relationship between the coverage of the first and second acrylate polymer particles in the polymer coating on both sides of the separator and the relationship between the difference between the two and the coverage of the concave part on the surface of the negative electrode, the battery can have high high-temperature cycle performance, high furnace temperature safety performance, and high long-cycle performance.

[0204] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A battery, characterized in that, The battery includes a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive and negative electrodes. The separator includes a carrier layer and polymer coatings on both sides of the carrier layer. In the separator, the polymer coating corresponding to the positive electrode is a first polymer coating, and the polymer coating corresponding to the negative electrode is a second polymer coating. The first polymer coating includes first particles that are dispersedly distributed and are composed of acrylate polymers. The second polymer coating includes second particles that are dispersedly distributed and are composed of acrylate polymers. The surface of the negative electrode has a recess. The battery satisfies the following relationship: F 1 <F 2 , 0.1≤M 1 / F 3 ≤1.2, where F 3 =F 2 -F 1 F 1 F represents the coverage of the first particles in any 25μm × 19μm area on the surface of the first polymer coating. 2 M represents the coverage of the second particles in any 25μm × 19μm area on the surface of the second polymer coating. 1 The coverage of the recess on the surface of the negative electrode sheet; The electrolyte includes a fluorinated solvent, which includes ethyl difluorocarbonate and ethylene fluorocarbonate. The weight ratio of ethyl difluorocarbonate to ethylene fluorocarbonate is 1-8.6, and the weight percentage of ethylene fluorocarbonate in the electrolyte is 5%-12.5%.

2. The battery according to claim 1, wherein, The battery satisfies the following relationship: 0.3≤M 1 / F 3 ≤0.95; And / or, F 1 The range is 4%-35%; And / or, F 2 It ranges from 10% to 45%; And / or, F 3 It ranges from 8% to 35%; And / or, M 1 It ranges from 3% to 17%; And / or, the acrylate polymers include one or more of the following: polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, acrylate monomer-acrylonitrile copolymer, styrene-acrylate monomer copolymer, acrylate monomer-acrylonitrile-ethylene copolymer, styrene-acrylate monomer-acrylonitrile copolymer, acrylate monomer-ethylene copolymer, ethylhexyl acrylate-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, methyl acrylate-N,N-dimethylacrylamide copolymer, ethyl acrylate-2-(diethylamino)ethyl acrylate copolymer, ethyl acrylate-N,N-diethylacrylamide copolymer, and ethyl acrylate-2-(diethylamino)ethyl acrylate.

3. The battery according to claim 1, wherein, The morphology of the recess includes one or more of holes, lines, and grooves; And / or, the width of the recess is 55μm-185μm; And / or, the depth of the recess is 5μm-35μm; And / or, the spacing between adjacent recesses is 0.9mm-1.8mm; And / or, the negative electrode sheet includes a negative current collector and a negative active layer located on one or both sides of the negative current collector, the negative active layer including a silicon-based material, the silicon-based material including one or more of elemental silicon particles, silicon-oxygen particles, silicon-carbon particles, silicon-nitrogen particles and silicon alloy particles.

4. The battery according to claim 1, wherein, The first polymer coating also includes a third particle, which is an agglomerated particle; And / or, the second polymer coating does not include third particles.

5. The battery according to claim 4, wherein, The diaphragm satisfies the following relationship: 1.5 ≤ d 1 / d 2 ≤25, where d 1 The average particle size of the secondary particles of the third particle is expressed in μm and d. 2 Dv90 of the first particle, in μm; And / or, the average particle size of the secondary particles of the third particle is 2μm-20μm; And / or, the Dv90 of the first particle is 0.65μm-4.5μm; And / or, at 90°C, the third particle is soaked in 2,2-difluoroethyl acetate for 4 hours, and the mass swelling degree of the third particle is less than 40%; And / or, the composition of the third particle includes one or more of the following: polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polyhexafluoropropylene, fluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, acrylate monomer-acrylonitrile copolymer, styrene-acrylate monomer copolymer, acrylate monomer-acrylonitrile-ethylene copolymer, acrylate monomer-ethylene copolymer, styrene-acrylate monomer-acrylonitrile copolymer, ethylhexyl acrylate-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, methyl acrylate-N,N-dimethylacrylamide copolymer, ethyl acrylate-2-(diethylamino)ethyl acrylate copolymer, ethyl acrylate-N,N-diethylacrylamide copolymer, and ethyl acrylate-2-(diethylamino)ethyl acrylate.

6. The battery according to claim 1, wherein, F 3 It ranges from 10% to 25%; And / or, M 1 It ranges from 5% to 11%; And / or, the first particle and the second particle may be the same or different; And / or, the average particle size of the first particle is 0.5 μm-1.2 μm; And / or, the average particle size of the second particle is 0.5 μm-1.2 μm; And / or, at 90°C, the first particles are immersed in 2,2-difluoroethyl acetate for 4 hours, and the mass swelling degree of the first particles is greater than 70%; And / or, at 90°C, the second particle is soaked in 2,2-difluoroethyl acetate for 4 hours, and the mass swelling degree of the second particle is greater than 70%; And / or, the first polymer coating has a coverage of 10%-45% on the surface of the carrier layer; And / or, the second polymer coating has a coverage of 10%-45% on the surface of the carrier layer; And / or, the thermal shrinkage rate of the diaphragm in the stretching direction is less than 10%; And / or, the diaphragm has a thermal shrinkage rate of less than 10% perpendicular to the stretching direction; And / or, the air permeability of the diaphragm is 60 s / 100cc-350 s / 100cc; And / or, the puncture strength of the diaphragm is greater than 120 gf.

7. The battery according to any one of claims 1-6, wherein, The fluorinated solvent in the electrolyte comprises 10%-75% by weight; And / or, the fluorinated solvent further includes one or more of difluoroethylene carbonate, ethyl fluorocarbonate, ethyl fluoroacetate, trifluoroethyl acetate, propyl difluoroacetate, and difluoropropyl acetate.

8. The battery according to claim 1, wherein, The ethyl difluoroacetate includes at least one of 2,2-difluoroethyl acetate and ethyl 2,2-difluoroacetate; And / or, the weight percentage of the ethyl difluoroacetate in the electrolyte is 5%-65%.

9. The battery according to claim 1, wherein, The carrier layer includes a substrate layer and a heat-resistant layer, wherein the heat-resistant layer is located on one or both surfaces of the substrate layer; And / or, the carrier layer includes a substrate layer and a heat-resistant layer, wherein the pore size of the substrate layer is 25nm-50nm; And / or, the carrier layer includes a substrate layer and a heat-resistant layer, wherein the thickness of the substrate layer is 3μm-10μm; And / or, the carrier layer includes a substrate layer and a heat-resistant layer, wherein the substrate layer comprises polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalate), poly(m-phenylene isophthalate), or one or more of the above polymer derivatives.

10. The battery according to claim 9, wherein, The heat-resistant layer comprises heat-resistant particles and a first binder. Based on the total weight of the heat-resistant layer, the heat-resistant particles account for 90%-99% of the weight, and the first binder accounts for 1%-10% of the weight. And / or, the thickness of the heat-resistant layer is 0.3μm-4.5μm; And / or, the heat-resistant layer comprises heat-resistant particles and a first binder, wherein the heat-resistant particles are composed of one or more of the following: boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium dioxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride, 1,3,5-triazine-2,4,6-triamine, melamine thiocyanate, melamine cyanurate, symmetric triaminotriazine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, 2,4,6-tris(2-pyridyl)triazine, 2-amino-4,6-methoxy-1,3,5-triazine, lithium aluminum titanium phosphate, uracil, cytosine, guanine, 4-amino-2,6-dihydroxypyrimidine, phenolic resin, cellulose, and benzimidazole compounds. And / or, the heat-resistant layer comprises heat-resistant particles and a first binder, wherein the heat-resistant particles have a Dv50 of 0.1 μm-1.5 μm; And / or, the heat-resistant layer comprises heat-resistant particles and a first adhesive, wherein the first adhesive comprises one or more of the following: polyvinyl alcohol, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinylpyrrolidone, acrylate adhesives, styrene-acrylic latex, polyacrylonitrile, polyvinyl acetate, polyacrylic acid, polyurethane, polyurethane-modified polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, or copolymer systems derived from the above polymers.

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