Battery

Abstract

The invention relates to the technical field of batteries, in particular to a battery. The battery comprises a diaphragm and an electrolyte, the diaphragm comprises a carrier layer and a coating, the coating comprises first particles, the components of the first particles comprise an ester group-containing polymer, and within the area of 100 [mu] m * 100 [mu] m of the surface of the coating, the number of primary particles of the first particles with the particle size smaller than or equal to 0.3 [mu] m accounts for 0.01%-4% of the number of the primary particles of the first particles; the electrolyte comprises cyclic carbonate and fluoroethylene carbonate, the weight ratio of the fluoroethylene carbonate in the electrolyte is 13%-50%, and the weight ratio of the cyclic carbonate to the fluoroethylene carbonate is (0.2-1.5): 1. According to the battery disclosed by the invention, a relatively stable and flexible SEI film is formed on the surface of the negative plate through synergistic cooperation of the diaphragm and the electrolyte, so that the interface stability between the diaphragm and the negative plate is improved, and the high-temperature long-cycle performance of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a battery. Background Art

[0002] Traditional graphite anodes are limited by their inherently low theoretical capacity, making them incapable of meeting the growing demand for high-performance energy storage. Against this backdrop, silicon materials have attracted considerable attention due to their ultra-high theoretical specific capacity and suitable lithium insertion potential. However, silicon exhibits a significant volume effect during the charge-discharge process, with its volume expansion in the lithium-intercalated state reaching 280%-300% compared to its initial volume. This drastic structural deformation directly leads to instability at the electrode-electrolyte interface.

[0003] During cycling, the solid electrolyte interface (SEI) film formed on the surface of silicon-based anodes is subjected to enormous mechanical stress due to the cyclic expansion and contraction of the silicon material during charge and discharge. When the accumulated stress exceeds the fracture toughness of the SEI film, the interfacial protective layer ruptures, exposing a fresh silicon surface. The newly exposed active materials undergo continuous side reactions with the electrolyte, inducing repeated repair and regeneration of the SEI film. This dynamic process not only accelerates the irreversible consumption of active lithium and electrolyte but also causes a cumulative increase in interfacial impedance, ultimately leading to rapid capacity decay and a sharp deterioration in cycling performance.

[0004] Therefore, it is very important to invent a battery with a SEI film structure that is highly stable and flexible. Summary of the Invention

[0005] To address the prior art problem of rapid battery capacity decay and drastically deteriorating cycle performance due to repeated repair and regeneration of the SEI film caused by the volume expansion of silicon materials, the present invention provides a battery. Through the synergistic effect of the separator and electrolyte, the battery of the present invention forms a relatively stable and flexible SEI film on the surface of the negative electrode sheet, thereby reducing the risk of SEI film damage during silicon-based material expansion, improving the interface stability between the separator and the electrode sheet, reducing the battery's high-temperature cycle impedance, and improving the battery's high-temperature, long-cycle performance.

[0006] In order to achieve the above-mentioned object, the present invention provides a battery, which includes a separator, a negative electrode sheet and an electrolyte; the separator includes a carrier layer and a coating located on one side or both sides of the carrier layer, the coating includes first particles, the components of the first particles include a first polymer, the first polymer is an ester-containing polymer, and within an area of ​​100 μm×100 μm on the surface of the coating, the number of primary particles of the first particles with a particle size less than or equal to 0.3 μm accounts for 0.01%-4% of the number of primary particles of the first particles; the electrolyte includes cyclic carbonate and fluoroethylene carbonate, the weight proportion of fluoroethylene carbonate in the electrolyte is 13%-50%, and the weight ratio of the cyclic ethylene carbonate to the fluoroethylene carbonate is (0.2-1.5):1.

[0007] Through the above technical solution, the present invention has at least the following advantages compared with the prior art: The battery of the present invention can ensure that the trace amount of first particles in the diaphragm achieves a high degree of matching with the cyclic carbonate and fluoroethylene carbonate in the electrolyte under the joint action of the cyclic carbonate and fluoroethylene carbonate by simultaneously controlling the proportion of the number of primary particles with a particle size of less than or equal to 0.3 μm in the primary particles of the first particles per unit area of ​​the coating surface, the weight proportion of fluoroethylene carbonate in the electrolyte, and the weight ratio of cyclic carbonate to fluoroethylene carbonate. The small-sized first polymer particles are excessively swollen under the action of the cyclic carbonate. The excessively swollen small-sized first particles can be corroded by the high content of FEC and cause slight dissolution. The small-sized first particles dissolve a trace amount of the first polymer and / or ester-containing groups, which act together with the fluoroethylene carbonate to form a relatively stable and flexible SEI film on the surface of the negative electrode sheet, thereby reducing the risk of SEI film rupture during the expansion of the silicon material and improving the cycle stability of the battery. At the same time, the high-temperature adhesion between the diaphragm and the electrode sheet is improved, the high-temperature cycle impedance of the battery is reduced, and the high-temperature long-cycle performance of the battery is improved.

[0008] Other features and advantages of the present invention will be described in detail in the following detailed description.

[0009] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Shown is one of the surface SEM images of the separator of the present invention.

[0011] Figure 2 Shown is the second surface SEM image of the diaphragm of the present invention. DETAILED DESCRIPTION

[0012] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention. In this article, unless otherwise specified, data ranges include endpoints.

[0013] It should be noted that the numerical expressions such as "first" and "second" in the present invention are only used to distinguish different substances or usage methods, and do not represent a difference in order.

[0014] The present invention provides a battery, comprising a separator, a negative electrode sheet and an electrolyte; the separator comprises a carrier layer and a coating located on one side or both sides of the carrier layer, the coating comprising first particles, the components of the first particles comprising a first polymer, the first polymer being an ester-containing polymer, and within an area of ​​100 μm×100 μm on the surface of the coating, the number of primary particles of the first particles having a particle size less than or equal to 0.3 μm (for example, 0.3 μm, 0.25 μm, 0.2 μm, 0.15 μm, 0.1 μm, 0.05 μm or 0.01 μm) accounts for 0.01%-4% (for example, 0.01%, 0.05%, 0.1 μm or 0.01 μm) of the primary particles of the first particles. %, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5% or 4%); the electrolyte comprises cyclic carbonate and fluoroethylene carbonate, the weight proportion of fluoroethylene carbonate in the electrolyte is 13%-50% (13%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%), and the weight ratio of the cyclic ethylene carbonate to the fluoroethylene carbonate is (0.2-1.5):1 (for example, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1 or 1.5:1).

[0015] In the diaphragm, the coating layer may be located on one side of the carrier layer or on both sides of the carrier layer. When the coating layer is located on both sides of the carrier layer, the coating layers on both sides of the carrier layer may be the same or different.

[0016] In the present invention, the first particles may include primary particles. The ratio of the number of primary particles of the first particles having a particle size of less than or equal to 0.3 μm in the total number of primary particles of the first particles within an area of ​​100 μm × 100 μm on the surface of the coating layer refers to the ratio of the number of single primary particles having a particle size of less than or equal to 0.3 μm in the first particles within an area of ​​100 μm × 100 μm on the surface of the coating layer away from the carrier layer, based on the total number of all primary particles. Specifically, it can be tested by the following method: arbitrarily select 100μm×100μm on the surface away from the carrier layer in the coating. It can be understood that when the coating is discontinuously coated, an area range of 100μm×100μm of the coating area should be selected. On the scanning image of the SEM, combined with graphic analysis software (for example, ImageJ, NanoMeasurer, Matlab, etc.), measurement and statistical processing are performed to obtain the particle size of all first particles, and the total number of primary particles in the first particles in the area is counted as M, wherein the number of single primary particles with a particle size less than or equal to 0.3μm is N. Then, within the area of ​​100μm×100μm on the surface of the coating, the number of primary particles of the first particles with a particle size less than or equal to 0.3μm accounts for (N / M)×100% of the number of primary particles of the first particles. Repeat the above operation 5 times, and take the average value as the final test result.

[0017] Research has found that a small amount of small-sized first particles can excessively swell under the action of cyclic carbonates, and can also be corroded by a high content of fluoroethylene carbonate, causing the small-sized first particles to dissolve a small amount of first polymer or ester-containing groups. The first polymer and / or ester-containing groups can work together with fluoroethylene carbonate to form a more stable and flexible SEI film on the surface of the negative electrode, thereby reducing the risk of SEI film rupture during the expansion of the silicon material, improving the cycle stability of the battery, and at the same time improving the high-temperature adhesion between the diaphragm and the electrode, reducing the high-temperature cycle impedance of the battery, and improving the high-temperature long-cycle performance of the battery.

[0018] In order to ensure that an appropriate amount of the first polymer and / or the ester-containing group can be dissolved from the first particles, and at the same time cooperate with the fluoroethylene carbonate to generate a stable and flexible SEI, and to ensure the overall structural stability of the coating containing the first particles and avoid excessive dissolution of the first polymer, the battery of the present invention simultaneously controls the proportion of primary particles with a particle size of less than or equal to 0.3 μm in the primary particles of the first particles per unit area of ​​the coating surface, the weight proportion of fluoroethylene carbonate in the electrolyte, and the weight ratio of cyclic ethylene carbonate to fluoroethylene carbonate.

[0019] Primary particles with smaller particle sizes are more likely to undergo excessive swelling under the action of cyclic ethylene carbonate. Controlling the ratio of primary particles with a particle size of 0.3 μm or less in the primary particles of the first particles per unit area of ​​the coating surface within the above range can ensure the presence of an appropriate number of primary particles with smaller particle sizes in the coating, facilitating the dissolution of an appropriate amount of the first polymer and / or ester-containing groups under the swelling action of cyclic ethylene carbonate and the corrosive action of fluoroethylene carbonate, thereby synergistically forming a highly stable and flexible SEI film with fluoroethylene carbonate, thereby improving the battery's cycle stability, reducing the battery's high-temperature cycle impedance, and improving the battery's high-temperature long-cycle performance. Furthermore, controlling the ratio of primary particles with a particle size of 0.3 μm or less in the primary particles of the first particles per unit area of ​​the coating surface within the above range can also ensure the presence of a larger number of primary particles with larger particle sizes in the coating. Larger primary particles are less susceptible to swelling by cyclic carbonate and corrosion by fluoroethylene carbonate, thereby ensuring the overall structural stability of the coating containing the first particles and preventing excessive dissolution of the first polymer and / or ester-containing groups. At the same time, controlling the weight ratio of cyclic ethylene carbonate to fluoroethylene carbonate within the above range can enable cyclic ethylene carbonate and fluoroethylene carbonate to exert a synergistic effect. With the cooperation of the two, a trace amount of small-particle first particles can over-swell under the action of cyclic ethylene carbonate. At the same time, the over-swelled small-particle first particles can cause a trace amount of the first polymer and / or ester-containing groups to be dissolved from the first particles under the corrosion of fluoroethylene carbonate, so that the first polymer and / or ester-containing groups can work together with fluoroethylene carbonate to form a more stable and flexible SEI film on the surface of the negative electrode sheet. At the same time, controlling the weight proportion of fluoroethylene carbonate in the electrolyte within the above range can ensure an appropriate amount of fluoroethylene carbonate in the electrolyte, which can avoid excessive fluoroethylene carbonate, which causes excessive corrosion to the first particles and affects the overall structural stability of the first particles, and can also avoid too little fluoroethylene carbonate, which fails to corrode the first particles, resulting in the first polymer and / or ester-containing groups being unable to dissolve or the dissolution amount being too small, and being unable to synergize with fluoroethylene carbonate to form a more stable and flexible SEI film on the surface of the negative electrode sheet.

[0020] When the weight ratio of cyclic ethylene carbonate to fluoroethylene carbonate is lower than 0.2:1, the weight proportion of fluoroethylene carbonate in the electrolyte is too high or the weight proportion of cyclic ethylene carbonate is too low, the mechanical stability of the coating in the separator is poor, resulting in reduced structural mechanical strength of the separator coating and increased interface impedance between the separator and the electrode, which is not conducive to the adhesion of the separator at high temperature and high temperature cycling. When the weight ratio of cyclic ethylene carbonate to fluoroethylene carbonate is higher than 1.5:1, the weight proportion of fluoroethylene carbonate in the electrolyte is too low or the weight proportion of cyclic ethylene carbonate is too high, the swelling degree of the first particles is too large, reducing the lithium ion permeability of the separator and increasing the battery impedance, or the dissolved first polymer and / or ester-containing group cannot synergize with sufficient fluoroethylene carbonate to form a more stable and flexible SEI film on the surface of the negative electrode, thereby failing to effectively improve the rupture of the SEI film, which is not conducive to improving the cycle stability of the battery and reducing the high temperature cycle impedance of the battery.

[0021] It can be understood that, in the present invention, the corrosion of the first particles by fluoroethylene carbonate does not mean that the particle state of all the first particles disappears or all the first particles are completely dissolved, but that the particle state of a single first particle disappears completely or partially. It can also be that some groups in a single first particle are dissolved, and the particle state of the single first particle can still be completely retained.

[0022] In the present invention, the ester groups dissolved from the first particles do not exist in the form of groups, but rather are substances with ester groups, which may be one or more of small molecules, monomers, oligomers and ions.

[0023] In the present invention, by simultaneously controlling the percentage of primary particles with a particle size of 0.3 μm or less within the primary particles of the first particles per unit area of ​​the coating surface, the weight percentage of fluoroethylene carbonate in the electrolyte, and the weight ratio of cyclic ethylene carbonate to fluoroethylene carbonate, the high-temperature cycle impedance of the battery is reduced and the high-temperature, long-cycle performance of the battery is improved compared to the prior art. To further enhance this effect, one or more of these technical features may be further optimized.

[0024] In one example, within an area of ​​100 μm×100 μm on the surface of the coating, the number of primary particles of the first particles having a particle size less than or equal to 0.3 μm accounts for 1%-3.5% of the total number of primary particles of the first particles.

[0025] In one example, the Dv95 of the first particles is 0.5 μm-5 μm (for example, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm). In the present invention, Dv95 is the particle size corresponding to the 95% cumulative particle size distribution in the volume particle size distribution of the first particles. In the present invention, the volume particle size distribution of the first particles can be obtained by arbitrarily selecting 100 μm × 100 μm in the SEM image of the coating surface, and measuring and statistically processing the Dv95 in combination with graphic analysis software (for example, ImageJ, NanoMeasurer, Matlab, etc.). The Dv95 of the first particles can also be obtained by testing with a laser particle size analyzer. For example, before preparing the diaphragm, the Dv95 of the first particles is obtained by measuring the first particles with a laser particle size analyzer.

[0026] In one example, Figure 1 and Figure 2 As shown, the first particles are arranged in a stacked pattern in the coating. The first particles are circled in red. Only some, not all, of the first particles are shown in the figure. It is understood that a stacked pattern means that, in the thickness direction of the separator, the first particles are present in only one layer or multiple layers in the coating, and no large-sized agglomerates are formed.

[0027] In one example, the first particles account for 10%-100% by mass of the coating (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100%).

[0028] In one example, the first polymer is a polymer containing an ester group and no fluorine.

[0029] In one example, the first polymer is an acrylic polymer.

[0030] In one example, the monomers forming the first polymer 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.

[0031] In one example, the first polymer includes one or more of polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, acrylate-acrylonitrile copolymer (e.g., methyl methacrylate-acrylonitrile copolymer), acrylate-ethylene copolymer (e.g., methacrylate-ethylene copolymer), acrylate-acrylonitrile-ethylene copolymer, styrene-acrylic ester monomer-acrylonitrile copolymer, ethylhexyl acrylate-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, methyl acrylate-acrylic acid-N,N-dimethylacrylamide copolymer, ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate copolymer, ethyl acrylate-acrylic acid-N,N-diethylacrylamide copolymer, and ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate.

[0032] In one example, the glass transition temperature of the first polymer is 40°C to 75°C (eg, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, or 75°C).

[0033] In one example, the coating includes an ester group.

[0034] In one example, the coating comprises 20% to 60% (eg, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, or 60%) ester groups by weight.

[0035] In one embodiment, the coating further comprises second particles, wherein the composition of the second particles comprises a fluoropolymer. Figure 1 and Figure 2 As shown, the second particles are agglomerated particles, and the particles in the green circles are second particles. It can be understood that only some of the second particles are marked in the figure, not all of the second particles.

[0036] In one example, the monomers forming the fluorine-containing polymer include one or more of vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, and hexafluoropropylene.

[0037] In one example, the fluorine-containing polymer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polyhexafluoropropylene, ethylene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer.

[0038] In one example, the mass fraction of the second particles in the coating is 0%-90% (e.g., 0, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%). When the mass fraction of the second particles in the coating is 0, it means that no second particles are present in the coating.

[0039] In one embodiment, the second particles include secondary particles. In the present invention, the secondary particles refer to agglomerates formed by agglomeration of four or more primary particles.

[0040] In one example, the average particle size d1 of the secondary particles of the second particles is 2 μm-15 μm (eg, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm).

[0041] In one example, the average particle size d1 of the secondary particles of the second particles is 3 μm-10 μm.

[0042] In the present invention, the average particle size of the secondary particles of the second particles can be measured by the following method: on a scanned image of the sample coating surface obtained by SEM, a square or rectangle with the smallest area that completely surrounds one secondary particle is drawn, that is, a square or rectangle with the edge of the secondary particle connected to the four sides of the square or rectangle is drawn, and 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. In an arbitrarily selected 10μm*10μm area on the coating surface, the particle size of any 100 secondary particles is measured, and the number average is the average particle size; repeat the above operation 5 times, and the average value is the average particle size of the secondary particles. It should be noted that when 100 secondary particles can be observed in the captured image, the number average of the particle sizes of any 100 secondary particles in the image is set as the average particle size of the secondary particles. When 100 secondary particles are not observed in the image, multiple images are captured, and the number average of the particle sizes of the total 100 secondary particles is set as the average particle size. The scanned image can be obtained by observing the surface of the coating layer using a scanning electron microscope (S-3400N manufactured by Hitachi, Ltd.).

[0043] In one embodiment, the battery satisfies the following relationship: 1≤d1 / d2≤25 (e.g., 1, 3, 5, 8, 10, 13, 15, 18, 20, 23, or 25), where d1 is the average particle size of the secondary particles of the second particles, and d2 is the Dv95 of the first particles. Controlling the battery to satisfy this relationship ensures that the coating comprising the first and second particles does not excessively swell at room temperature, thereby improving the mechanical stability of the coating at room temperature, enhancing the interfacial stability between the separator and the electrode at room temperature, reducing the battery's room-temperature cycling impedance, and improving the battery's room-temperature cycling performance.

[0044] In one example, the battery satisfies the following relationship: 1.5≤d1 / d2≤20.

[0045] According to a specific embodiment, d1 is 2 μm-15 μm, d2 is 0.5 μm-5 μm, and the battery satisfies the following relationship: 1≤d1 / d2≤25.

[0046] According to a specific embodiment, d1 is 3 μm-10 μm, d2 is 0.5 μm-5 μm, and the battery satisfies the following relationship: 1.5≤d1 / d2≤20.

[0047] In one example, the coating has a thickness of 0.5 μm to 5 μm (eg, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm).

[0048] In one example, based on the total weight of the coating, the weight of the first particles is 10%-45% (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40% or 45%), and the weight of the second particles is 55%-90% (e.g., 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90%).

[0049] In one embodiment, the coverage of the coating on the surface of the carrier layer is 8%-100% (for example, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100%). In the present invention, the coverage of the coating on the surface of the carrier layer refers to the proportion of the orthographic projection area of ​​the coating on one side on the surface of the carrier layer to the area of ​​the surface of the carrier layer on that side (i.e., the surface of the carrier layer on the coated side). When there are coatings on both sides of the carrier layer, the coverage of the coatings on both sides may be the same or different. The coverage of the coating on the surface of the carrier layer can be tested by the following method: obtain a microscopic image of the coating surface using SEM, and randomly divide an area of ​​100µm in the image. 2 An area (for example, 100µm×100µm) is divided into uniform grids of 100*100. If the coverage area of ​​the orthographic projection of the coating in the grid exceeds half of the grid area, it means that the square is occupied by the coating. Otherwise, it means that the square is not occupied by the coating. The number of squares occupied by the coating is counted, and the total number of squares occupied by the coating is recorded as X. The coverage rate = (X / 100*100)*100%. Repeat the above operation 5 times, and the average value of the 5 times is the coverage rate of the coating on the surface of the carrier layer.

[0050] In one example, the carrier layer includes a substrate layer and a heat-resistant layer located on one side or both sides of the substrate layer.

[0051] In one example, the diaphragm includes a substrate layer, a heat-resistant layer, and a coating layer, wherein the heat-resistant layer is located on one surface of the substrate layer, and the coating layer is located on the other surface of the substrate layer.

[0052] In one example, the diaphragm includes a substrate layer, a heat-resistant layer, and a coating layer. The heat-resistant layer is located on one surface of the substrate layer, and the coating layer is located on the surface of the heat-resistant layer and the other surface of the substrate layer.

[0053] In one example, the diaphragm includes a substrate layer, a heat-resistant layer, and a coating layer. The heat-resistant layer is located on both side surfaces of the substrate layer, and the coating layer is located on the surface of the heat-resistant layer.

[0054] In one example, the heat-resistant layer includes third particles and a binder.

[0055] In one example, the components of the third particles include boehmite, aluminum oxide, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium oxide, 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-bromophenyl)-4,6-dimethyl- ... ,3,5-triazine, 1-(4,6-diamino-1,3,5-triazine-2-yl)guanidine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, cyanuric chloride, 2,4,6-tris(2-pyridyl)triazine, 2,4,6-triphenyl-1,3,5-triazine, tris(tribromophenoxy)triazine, 2-amino-4,6-methoxy-1,3,5-triazine, uracil, cytosine and one or more of lithium aluminum titanium phosphate.

[0056] In one example, the binder includes polyvinyl alcohol, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinyl pyrrolidone, polymethyl methacrylate, polybutyl methacrylate, styrene acrylic latex, polyacrylonitrile, polyethyl acrylate, polyacrylic acid, polyvinyl acetate, polyacrylate, polyurethane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), and one or more copolymer systems derived from the above polymers.

[0057] In one embodiment, the weight ratio of the third particles to the binder is (30%-99%):(70%-1%) (e.g., 30%:70%, 40%:60%, 50%:50%, 60%:40%, 70%:30%, 80%:20%, 90%:10%, 91%:9%, 92%:8%, 93%:7%, 94%:6%, 95%:5%, 96%:4%, 97%:3%, 98%:2%, or 99%:1%). It is understood that the weight proportion of the third particles in the heat-resistant layer can be in the range of 30%-99%, and the weight proportion of the binder in the heat-resistant layer can be in the range of 70%-1%.

[0058] In one embodiment, the binder is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), and copolymers derived from these polymers. The binder accounts for 30% to 70% (e.g., 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%) of the heat-resistant layer by weight.

[0059] In one embodiment, the binder is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), and copolymers derived from the above polymers. The binder accounts for 35% to 50% by weight of the heat-resistant layer.

[0060] In one embodiment, the binder is selected from one or more of polyvinyl alcohol, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinyl pyrrolidone, polymethyl methacrylate, polybutyl methacrylate, styrene-acrylic latex, polyacrylonitrile, polyethyl acrylate, polyacrylic acid, polyvinyl acetate, polyacrylate, polyurethane, and copolymers derived from the foregoing polymers. The binder comprises 1% to 10% (e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%) by weight of the heat-resistant layer.

[0061] In one example, the heat-resistant layer further includes a thickener, and the thickener includes one or more of methyl cellulose (CMC), sodium carboxymethyl cellulose (CMC-Na), and lithium carboxymethyl cellulose (CMC-Li).

[0062] In one embodiment, the weight percentage of the thickener in the heat-resistant layer is 0-1% (e.g., 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%). When the weight percentage of the thickener in the heat-resistant layer is 0, it means that the heat-resistant layer does not contain the thickener.

[0063] In one embodiment, the third particles have a Dv10 of 0.01 μm to 1.5 μm (e.g., 0.01 μm, 0.05 μm, 0.1 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 1.3 μm, or 1.5 μm). Controlling the Dv10 of the third particles within this range can enhance the bonding strength between the heat-resistant layer and the coating, while also improving the flexibility of the heat-resistant layer, the adhesion between the separator and the electrode, and the lithium ion transfer rate, thereby enhancing the battery's room-temperature cycling performance.

[0064] In the present invention, Dv10 is the particle size corresponding to the 10% cumulative particle size distribution in the volume particle size distribution of the third particles. The Dv10 of the third particles can be measured by a laser particle size analyzer.

[0065] In one example, the heat-resistant layer has a thickness of 0.2 μm-5 μm (eg, 0.2 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm).

[0066] In one example, the thickness of the substrate layer is 2 μm-10 μm (eg, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm).

[0067] In one example, the porosity of the substrate layer is 25%-70% (eg, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%).

[0068] In one example, the substrate layer comprises one or more of polyolefin (e.g., PP, PE), polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), and derivatives of the above polymers.

[0069] In one example, after the diaphragm is compressed at a pressure of 2 MPa for 0.5 h at 80° C., the compression rate of the diaphragm is 10%-50% (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%).

[0070] In the present invention, the compressibility of the diaphragm can be tested by the following method: The compressibility of the diaphragm is well known in the art and can be tested using equipment and methods well known in the art, such as testing in accordance with the national standard GB / T1041-2008 for testing the compression properties of plastics. Specifically, the diaphragm may be derived from the diaphragm itself or from a battery cell. When the diaphragm is derived from the diaphragm itself, the compression properties can be tested directly without drying it. When the diaphragm is derived from a battery cell, the diaphragm needs to be dried, and the compression properties tested after drying. The drying process is as follows: disassemble the battery cell, remove the diaphragm, and place the diaphragm in a 60°C oven to dry for 2 hours. The compression properties test process is as follows: spread the diaphragm flat on a flat aluminum foil surface and cover it with a layer of aluminum foil to ensure the diaphragm is flat. Cut 50 sets of diaphragm samples of a fixed area (e.g., 5cm x 5cm). Cover the upper and lower surfaces of each set of diaphragm samples with aluminum foil. Stack all 50 sets of samples together for subsequent compression testing. Cut 100 pieces of aluminum foil of the same size and stack them together to serve as a blank. Tests were performed using a universal tensile machine in compression mode at a speed of 0.5mm / min. The stress-strain curves were recorded to determine the compression ratio of the diaphragm samples.

[0071] According to a specific embodiment, within an area of ​​100 μm×100 μm on the surface of the coating, the number of primary particles of the first particles with a particle size less than or equal to 0.3 μm accounts for 0.01%-4% of the number of primary particles of the first particles; the Dv95 of the first particles is 0.5 μm-5 μm; the first particles are arranged in a stacked manner in the coating; the average particle size d1 of the secondary particles of the second particles is 3 μm-10 μm; the battery satisfies the following relationship: 1.5≤d1 / d2≤20; the thickness of the coating is 0.5 μm-5 μm; the weight proportion of ester groups in the coating is 20%-60%; the first polymer includes polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, acrylate-acrylonitrile copolymer, acrylate-acrylonitrile-ethylene copolymer, styrene-acrylate One or more of a monomer-acrylonitrile copolymer, an ethylhexyl acrylate-methyl methacrylate copolymer, a butyl acrylate-methyl methacrylate copolymer, a methyl acrylate-acrylic acid-N,N-dimethylacrylamide copolymer, an ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate copolymer, an ethyl acrylate-acrylic acid-N,N-diethylacrylamide copolymer, and an ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate; the fluorine-containing polymer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polyhexafluoropropylene, a vinyl fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-hexafluoropropylene copolymer, and a tetrafluoroethylene-hexafluoropropylene copolymer; the diaphragm meeting the above characteristics can be compressed at 80°C and under a pressure of 2MPa for 0.5h, and the compression rate of the diaphragm is 10%-50%.

[0072] In one example, after the membrane is baked at 80° C. for 2 hours, the porosity of the membrane is 30%-60% (e.g., 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58% or 60%).

[0073] In the present invention, the porosity of the diaphragm can be measured by the following method: the diaphragm is balled and placed into a 3.5mL sample cup. The sample cup is then placed in a true density tester. Helium is introduced into the closed test system according to a program. The pressure of the gas in the sample chamber and expansion chamber is measured, and the true volume is calculated according to Bohr's law (PV = nRT), thereby obtaining the porosity of the sample. Porosity = (V1 - V2) / V1 * 100%, where V1 is the apparent volume of the sample and V2 is the true volume of the sample.

[0074] According to a specific embodiment, within an area of ​​100 μm×100 μm on the surface of the coating, the number of primary particles of the first particles with a particle size less than or equal to 0.3 μm accounts for 0.01%-4% of the number of primary particles of the first particles; the Dv95 of the first particles is 0.5 μm-5 μm; the first particles are arranged in a stacked manner in the coating; the average particle size d1 of the secondary particles of the second particles is 3 μm-10 μm; the battery satisfies the following relationship: 1.5≤d1 / d2≤20; the thickness of the coating is 0.5 μm-5 μm; the weight proportion of ester groups in the coating is 20%-60%; the first polymer includes polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, acrylate-acrylonitrile copolymer, acrylate-acrylonitrile-ethylene copolymer, styrene One or more of a copolymer of olefin-acrylic ester monomer-acrylonitrile, a copolymer of ethylhexyl acrylate-methyl methacrylate, a copolymer of butyl acrylate-methyl methacrylate, a copolymer of methyl acrylate-acrylic acid-N,N-dimethylacrylamide, an ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate copolymer, an ethyl acrylate-acrylic acid-N,N-diethylacrylamide copolymer, and an ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate; the fluorine-containing polymer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polyhexafluoropropylene, a vinyl fluoride-hexafluoropropylene copolymer, a vinylidene fluoride-hexafluoropropylene copolymer, and a tetrafluoroethylene-hexafluoropropylene copolymer; the diaphragm meeting the above characteristics can have a porosity of 30%-60% after being baked at 80°C for 2h.

[0075] According to a specific embodiment, within an area of ​​100 μm×100 μm on the surface of the coating, the number of primary particles of the first particles with a particle size less than or equal to 0.3 μm accounts for 0.01%-4% of the number of primary particles of the first particles; the Dv95 of the first particles is 0.5 μm-5 μm; the first particles are arranged in layers in the coating; the average particle size d1 of the secondary particles of the second particles is 3 μm-10 μm; the battery satisfies the following relationship: 1.5≤d1 / d2≤20; the thickness of the coating is 0.5 μm-5 μm; the weight proportion of ester groups in the coating is 20%-60%; the first polymer includes polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, acrylate-acrylonitrile copolymer, acrylate-acrylonitrile-ethylene copolymer, styrene-acrylate monomer-acrylonitrile copolymer, acrylic acid One or more of ethylhexyl ester-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, methyl acrylate-acrylic acid-N,N-dimethylacrylamide copolymer, ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate copolymer, ethyl acrylate-acrylic acid-N,N-diethylacrylamide copolymer, ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate; the fluorine-containing polymer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polyhexafluoropropylene, vinyl fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer and tetrafluoroethylene-hexafluoropropylene copolymer; the diaphragm meeting the above characteristics can be compressed at 80°C under a pressure of 2MPa for 0.5h, and the compression rate of the diaphragm is 10%-50%, and after baking at 80°C for 2h, the porosity of the diaphragm is 30%-60%.

[0076] In one embodiment, the weight proportion of fluoroethylene carbonate in the electrolyte is 15%-35%.

[0077] In one example, the cyclic carbonate includes ethylene carbonate and / or propylene carbonate.

[0078] In one example, the weight percentage of the cyclic carbonate in the electrolyte is 5%-50% (eg, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%).

[0079] In one embodiment, the weight ratio of the cyclic carbonate in the electrolyte is 10%-25%.

[0080] In one embodiment, the weight ratio of the cyclic ethylene carbonate to the fluoroethylene carbonate is (0.6-1.1):1.

[0081] According to a specific embodiment, the weight proportion of fluoroethylene carbonate in the electrolyte is 13%-50%, the weight proportion of the cyclic carbonate in the electrolyte is 5%-50%, and the weight ratio of the cyclic ethylene carbonate to the weight of fluoroethylene carbonate is (0.2-1.5):1.

[0082] According to a specific embodiment, the weight proportion of fluoroethylene carbonate in the electrolyte is 15%-35%, the weight proportion of the cyclic carbonate in the electrolyte is 10%-25%, and the weight ratio of the cyclic ethylene carbonate to the weight of fluoroethylene carbonate is (0.6-1.1):1.

[0083] In one example, the electrolyte includes a lithium salt, an organic solvent, and an additive.

[0084] In one example, the lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide), lithium difluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, and lithium difluorobis(oxalatophosphate).

[0085] In one example, the organic solvent includes one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl formate (MF), methyl acetate (MA), methyl butyrate (MB), ethyl propionate (EP), propyl propionate (PP), ethyl butyrate, propyl acetate, and ethyl difluoroacetate.

[0086] In one embodiment, the additives include negative electrode surface film-forming additives, positive electrode surface film-forming additives, and positive and negative electrode current collector surface film-forming additives. They may also include additives that improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance. The additives may be one or more of dinitrile compounds, trinitrile compounds, and other nitrile compounds, fluorinated chain carbonates, fluorinated carboxylates, and sulfur-containing compounds.

[0087] The dinitrile compounds include, but are not limited to, succinonitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanooctane, 1,9-dicyanononane, 1,10-dicyanodecane, 1,12-dicyanododecane, tetramethylsuccinonitrile, 2-methylglutaronitrile, 2,4-dimethylvaleronitrile, 2,2,4,4-tetramethylglutaronitrile, Nitrile, 1,5-dicyanopentane, 2,6-dicyanoheptane, 2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,5-dioxa-heptanenitrile, 1,4-bis(cyanoethoxy)butane, ethylene glycol bis(2-cyanoethyl) ether, diethylene glycol bis(2-cyanoethyl) ether, tris ... Ethylene glycol bis(2-cyanoethyl) ether, tetraethylene glycol bis(2-cyanoethyl) ether, 3,6,9,12,15,18-hexaoxaeicosanoic acid dinitrile, 1,3-bis(2-cyanoethoxy)propane, 1,4-bis(2-cyanoethoxy)butane, 1,5-bis(2-cyanoethoxy)pentane, ethylene glycol bis(4-cyanobutyl) ether, 1,4-dicyano-2-butene, 1,4 - one or more of dicyano-2-methyl-2-butene, 1,4-dicyano-2-ethyl-2-butene, 1,4-dicyano-2,3-dimethyl-2-butene, 1,4-dicyano-2,3-diethyl-2-butene, 1,6-dicyano-3-hexene, 1,6-dicyano-2-methyl-3-hexene or 1,6-dicyano-2-methyl-5-methyl-3-hexene.

[0088] Trinitrile compounds include, but are not limited to, one or more of 1,3,5-pentanetricarboxylonitrile, 1,2,3-propanetricarboxylonitrile, 1,3,6-hexanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, 1,1,1-tris(cyanoethoxymethylene)ethane, 1,1,1-tris(cyanoethoxymethylene)propane, 3-methyl-1,3,5-tris(cyanoethoxy)pentane, 1,2,7-tris(cyanoethoxy)heptane, 1,2,6-tris(cyanoethoxy)hexane, or 1,2,5-tris(cyanoethoxy)pentane.

[0089] Sulfur-containing compounds include, but are not limited to, one or more of 1,3-propane sultone, vinyl sulfate, vinyl sulfate, cyclic sulfate, chain sulfate, chain sulfonate, cyclic sulfonate, chain sulfite, cyclic sulfite, chain sulfone, and cyclic sulfone.

[0090] The fluorinated chain carbonates include, but are not limited to, one or more of fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, trifluoroethyl methyl carbonate, and bis(trifluoroethyl) carbonate.

[0091] In one example, based on the total weight of the electrolyte, the weight percentage of the lithium salt is 5%-30% (e.g., 5%, 10%, 15%, 20%, 25%, or 30%), the weight percentage of the organic solvent is 0%-60% (e.g., 0, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, or 60%), and the weight percentage of the additive is 0%-30% (e.g., 0, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, or 30%). When the weight percentage of the organic solvent in the electrolyte is 0, it means that no organic solvent is present in the electrolyte. When the weight percentage of the additive in the electrolyte is 0, it means that no additive is present in the electrolyte.

[0092] In one embodiment, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on one or both surfaces of the negative electrode current collector, and the coating corresponds to the negative electrode active layer. It is understood that when the coating is located on one surface of the carrier layer, the negative electrode sheet corresponds to the coated side of the separator, and the positive electrode sheet corresponds to the other side of the separator. When the coating is located on both surfaces of the carrier layer, the negative electrode sheet corresponds to either coated side of the separator, and the positive electrode sheet corresponds to the other side of the separator.

[0093] In one example, the separator includes a carrier layer and coatings located on both sides of the carrier layer, the coating corresponding to the negative electrode active layer is composed of first particles, and the coating corresponding to the positive electrode active layer is composed of first particles and second particles.

[0094] In one example, the negative electrode active layer includes a silicon-based material, and the silicon-based material includes one or more of elemental silicon particles, silicon-oxygen compound particles, silicon-carbon composite particles, silicon-nitrogen composite particles, and silicon alloy particles.

[0095] In one example, the average particle size of the silicon-carbon composite particles is 5 μm-12 μm (eg, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, or 12 μm).

[0096] In the present invention, the average particle size of the silicon-carbon composite particles can be measured by the following method: on a scanned image of the surface of the negative electrode active layer obtained using an SEM, draw the smallest square or rectangle that completely encloses one silicon-carbon composite particle, i.e., draw a square or rectangle where the edge of the silicon-carbon composite particle touches all four sides of the square or rectangle. The length of one side of the square or the length of the longest side of the rectangle is the particle size of the silicon-carbon composite particle. In a randomly selected 10 μm*10 μm area on the surface of the negative electrode active layer, measure the particle sizes of 100 silicon-carbon composite particles, and take the number average of the measured values ​​as the average particle size. Repeat this operation five times, and take the average value as the average particle size of the silicon-carbon composite particles. It should be noted that if 100 silicon-carbon composite particles are observable in the captured image, the number average of the particle sizes of the 100 silicon-carbon composite particles in the image is taken as the average particle size of the silicon-carbon composite particles. If 100 silicon-carbon composite particles are not observable in the image, multiple images are captured, and the number average of the particle sizes of the total 100 silicon-carbon composite particles is taken as the average particle size. The scanned image can be obtained by observing the surface of the coating layer using a scanning electron microscope (S-3400N manufactured by Hitachi, Ltd.).

[0097] In one embodiment, the silicon-carbon composite particles have a degree of graphitization of 0-0.85 (e.g., 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.85). Controlling the degree of graphitization of the silicon-carbon composite particles within this range can balance the electron migration resistance of the silicon-carbon composite particles with the stability of the SEI film. Although a high degree of graphitization may result in high mechanical strength and low electron migration resistance, the silicon-carbon composite particles may have low toughness and may not be able to effectively absorb silicon volume strain.

[0098] In the present invention, the graphitization degree of the silicon-carbon composite particles can be tested by the following method: using the X-ray diffraction (XRD) method, for example, using a Shimadzu XRD-6100 X-ray diffractometer for testing, and the sample weight for the test is 0.5 g / cm 2 The Kα line of Cu was used as the incident X-ray, the operating voltage of the X-ray source was 40 kV, the test power was 2 kW, 2θ was used as the horizontal coordinate and the unit was °, the signal intensity was used as the vertical coordinate, the test range was 10~80°, the scanning rate was 4° / min, the data point interval was 0.02°, and according to the position of the (002) peak of the material in the range of 2θ=22.5°-26.5°, the interlayer spacing d002 of the (002) peak was calculated using the Bragg formula, and then the graphitization degree g value was calculated using the Mering–Maire formula g=(0.3440-d002) / (0.3440-0.3354).

[0099] In one example, the silicon-carbon composite particles have a sphericity of 0.6-1 (eg, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or 1).

[0100] In the present invention, the sphericity of the silicon-carbon composite particles can be tested by the following method: using a scanning electron microscope (SEM) to capture an image of the particles on the surface of the negative electrode active layer, using image processing software to draw a rectangle with the smallest area that completely surrounds one particle on the obtained scanned image, that is, a rectangle in which the edge of the silicon-carbon composite particle is connected to the four sides of the rectangle, measuring the longest side and the shortest side of the rectangle, and calculating the sphericity = shortest side / longest side.

[0101] In one embodiment, the negative electrode active layer includes a negative electrode active material, a negative electrode conductor, and a negative electrode binder, wherein the negative electrode active material includes a silicon-based material and a carbon-based material. The negative electrode active layer includes silicon.

[0102] In one example, the carbon-based material includes graphite.

[0103] In one example, based on the total weight of the negative electrode active material layer, the weight content of the negative electrode active material is 95%-98.5% (eg, 95%, 96%, 97%, 98% or 98.5%).

[0104] In one example, the weight content of silicon is 3%-70% (e.g., 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65% or 70%) based on the total weight of the negative electrode active material layer.

[0105] In one example, based on the total weight of the negative electrode active material layer, the weight content of silicon is 7%-30%.

[0106] In one example, the negative electrode active material layer further includes a negative electrode conductor and a negative electrode binder.

[0107] In one example, the negative electrode conductive agent includes one or more of furnace black, acetylene black, Ketjen black, and carbon nanotubes.

[0108] In one example, the negative electrode binder includes one or more of acrylic acid-acrylonitrile copolymer, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyacrylic acid (PAA), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR).

[0109] In one example, based on the total weight of the negative electrode active material layer, the weight content of the negative electrode conductor is 0.1%-1.5% (for example, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.3% or 1.5%), and the weight content of the negative electrode binder is 0.5%-3.5% (for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3% or 3.5%).

[0110] In one embodiment, the battery includes a positive electrode sheet. The positive electrode sheet can be a conventional positive electrode sheet in the art, for example, the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer located on at least one surface of the positive electrode current collector. The positive electrode active layer can be composed according to conventional compositions in the art.

[0111] In one example, the battery is a lithium-ion secondary battery.

[0112] The present invention will be described in detail below through examples. The examples described in the present invention are only some examples of the present invention, not all examples. All other examples obtained by persons of ordinary skill in the art based on the examples of the present invention without creative work are within the scope of protection of the present invention.

[0113] The following examples illustrate the batteries of the present invention.

[0114] Example 1 (1) Diaphragm The third particles (aluminum oxide) and polyacrylic acid (binder) were mixed and stirred thoroughly to obtain a mixed slurry with a solid content of 25%. The mixed slurry was coated on one surface of the base material (PE) using a gravure roller, with a mass ratio of aluminum oxide to polyacrylic acid (weight ratio) of 96% to 4% based on a 100% solid slurry. The mixed slurry was dried in a multi-section oven at 60°C to form a heat-resistant layer with a thickness of 1 μm. The first particles (methyl methacrylate-acrylonitrile copolymer) and the second particles (PVDF-HFP copolymer) are dispersed in deionized water (wherein the mass proportion of the first particles in the coating is 40% and the mass proportion of the second particles in the coating is 60%), and after sufficient stirring, a first slurry with a solid content of 10% is obtained; the first particles (methyl methacrylate-acrylonitrile copolymer) are dispersed in deionized water, and after sufficient stirring, a second slurry with a solid content of 10% is obtained; the first slurry is coated on the surface of the heat-resistant layer by a gravure roller, and the second slurry is coated on the other side of the substrate layer, and then dried in a multi-section oven at 60°C to form a coating.

[0115] Among them, within the area of ​​100μm×100μm on the surface of the coating, the number of primary particles of the first particles with a particle size less than or equal to 0.3μm accounts for 1.4% of the number of primary particles of the first particles, the Dv95 of the first particles is 0.9μm, the average particle size d1 of the secondary particles in the second particles is 6.2μm, d1 / d2=6.2 / 0.9=6.89, and the coverage rate of the coating on the surface of the carrier layer is 20%.

[0116] (2) Electrolyte In an argon-filled glove box (moisture <1ppm, oxygen <1ppm), ethylene carbonate, propylene carbonate, propyl propionate, and ethyl propionate solvents were mixed to form a uniform solvent. LiPF6, 1,3,6-hexanetrinitrile, and fluoroethylene carbonate were slowly added. After stirring, an electrolyte was obtained. The weight proportion of LiPF6 in the electrolyte was 16%, the weight proportion of 1,3,6-hexanetrinitrile was 3%, the weight proportion of fluoroethylene carbonate was 21.1%, the weight proportion of cyclic ethylene carbonate was 18.4% (the weight ratio of ethylene carbonate to propylene carbonate was 0.5:1), and the weight ratio of propyl propionate to ethyl propionate was 5:2.

[0117] (3) Negative electrode The carbon-based material (graphite), silicon-based material (silicon-carbon composite particles with an average particle size of 8μm, a degree of graphitization of 0.1, and a sphericity of 0.8), negative electrode conductive agent (carbon black: carbon nanotubes (weight ratio) = 1:1), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber were mixed in an aqueous solvent at a weight ratio of 86:12:1:0.5:0.5. The mixture was continuously stirred in a blender to form a uniform, fluid negative electrode slurry. Subsequently, the slurry was coated on both sides of a 10μm thick current collector copper foil to form a negative electrode active layer. The negative electrode was then dried in a 120°C vacuum oven for 6 hours. The negative electrode sheets were then rolled and slit.

[0118] (4) Positive electrode Lithium cobalt oxide, binder polyvinylidene fluoride (PVDF 500), and conductive material (SuperP: carbon nanotubes = 2:1) were mixed in N-methylpyrrolidone (NMP) solvent at a weight ratio of 98:2:2. The mixture was stirred continuously in a blender to form a uniform, fluid cathode slurry. The cathode slurry was then coated onto 10μm-thick aluminum foil and dried in a 120°C vacuum oven for 6 hours. The resulting cathode sheets were then rolled and slit.

[0119] (5) Lithium-ion batteries The positive electrode sheet prepared in step (4), the separator prepared in step (1), and the negative electrode sheet prepared in step (34) are wound to prepare a bare cell; the bare cell is then placed in an aluminum-plastic film, and the electrolyte prepared in step (2) is injected into the dried bare cell. After vacuum packaging, room temperature standing, high-temperature formation and other processes, the desired lithium-ion battery is obtained.

[0120] Example 2 group This set of embodiments is used to illustrate the impact when the proportion of the number of primary particles of first particles with a particle size less than or equal to 0.3 μm in the number of primary particles of the first particles changes within an area of ​​100 μm×100 μm on the surface of the coating.

[0121] Example 2a The method is carried out in accordance with Example 1, except that, within an area of ​​100 μm×100 μm on the surface of the coating, the number of primary particles of the first particles having a particle size less than or equal to 0.3 μm accounts for 0.016% of the number of primary particles of the first particles.

[0122] Example 2b The method is carried out in accordance with Example 1, except that, within an area of ​​100 μm×100 μm on the surface of the coating, the number of primary particles of the first particles having a particle size less than or equal to 0.3 μm accounts for 0.57% of the number of primary particles of the first particles.

[0123] Example 2c The method is carried out in accordance with Example 1, except that, within an area of ​​100 μm×100 μm on the surface of the coating, the number of primary particles of the first particles having a particle size less than or equal to 0.3 μm accounts for 2.33% of the number of primary particles of the first particles.

[0124] Example 2d The method is carried out in accordance with Example 1, except that, within an area of ​​100 μm×100 μm on the surface of the coating, the number of primary particles of the first particles having a particle size less than or equal to 0.3 μm accounts for 3.96% of the number of primary particles of the first particles.

[0125] Example 3 group This set of examples is used to illustrate the effects of changing the weight ratio of fluoroethylene carbonate in the electrolyte.

[0126] Example 3a The process was carried out in accordance with Example 1, except that the weight proportion of fluoroethylene carbonate in the electrolyte was 13%, and the ratio of the weight of cyclic ethylene carbonate to the weight of fluoroethylene carbonate was 1.42.

[0127] Example 3b The process was carried out in accordance with Example 1, except that the weight proportion of fluoroethylene carbonate in the electrolyte was 15%, and the ratio of the weight of cyclic ethylene carbonate to the weight of fluoroethylene carbonate was 1.23.

[0128] Example 3c The process was carried out in accordance with Example 1, except that the weight proportion of fluoroethylene carbonate in the electrolyte was 35%, and the ratio of the weight of cyclic ethylene carbonate to the weight of fluoroethylene carbonate was 0.53.

[0129] Example 3d The process was carried out with reference to Example 1, except that the weight proportion of fluoroethylene carbonate in the electrolyte was 50%, and the ratio of the weight of cyclic ethylene carbonate to the weight of fluoroethylene carbonate was 0.37.

[0130] Example 4 Group This set of examples is used to illustrate the effects of changing the weight ratio of cyclic ethylene carbonate to fluoroethylene carbonate.

[0131] Example 4a The process was carried out with reference to Example 1, except that the weight proportion of fluoroethylene carbonate in the electrolyte was 24.5%, the weight proportion of cyclic ethylene carbonate in the electrolyte was 5%, and the ratio of the weight of cyclic ethylene carbonate to the weight of fluoroethylene carbonate was 0.2.

[0132] Example 4b The process was carried out with reference to Example 1, except that the weight proportion of cyclic ethylene carbonate in the electrolyte was 10%, and the weight ratio of cyclic ethylene carbonate to fluoroethylene carbonate was 0.47.

[0133] Example 4c The process was carried out with reference to Example 1, except that the weight proportion of cyclic ethylene carbonate in the electrolyte was 25%, and the weight ratio of cyclic ethylene carbonate to fluoroethylene carbonate was 1.18.

[0134] Example 4d The method is carried out with reference to Example 1, except that the weight proportion of fluoroethylene carbonate in the electrolyte is 33.6%, the weight proportion of cyclic ethylene carbonate in the electrolyte is 50%, the ratio of the weight of cyclic ethylene carbonate to the weight of fluoroethylene carbonate is 1.49, the weight proportion of LiPF6 in the electrolyte is 15%, the weight proportion of 1,3,6-hexanetrinitrile is 1.4%, and propyl propionate and ethyl propionate are not present in the electrolyte.

[0135] Example 5 group This set of embodiments is used to illustrate the impact produced when d1 / d2 changes.

[0136] Example 5a The process is carried out in accordance with Example 1, except that d1 is 9.7 μm, d2 is 0.5 μm, and d1 / d2=9.7 / 0.5=19.4.

[0137] Example 5b The process is carried out in accordance with Example 1, except that d1 is 5.2 μm, d2 is 4.9 μm, and d1 / d2=5.2 / 4.9=1.06.

[0138] Example 5c The process is carried out in accordance with Example 1, except that d1 is 14.8 μm, d2 is 0.6 μm, and d1 / d2=14.8 / 0.6=24.67.

[0139] Example 5d The process is carried out in accordance with Example 1, except that d1 is 3.1 μm, d2 is 2 μm, and d1 / d2=3.1 / 2=1.55.

[0140] Example 5e The process is carried out in accordance with Example 1, except that d1 is 2.3 μm, d2 is 1.3 μm, and d1 / d2=2.3 / 1.3=1.77.

[0141] Example 5f The process is carried out in accordance with Example 1, except that d1 is 2.3 μm, d2 is 2.7 μm, and d1 / d2=2.3 / 2.7=0.85.

[0142] Example 5g The process is carried out in accordance with Example 1, except that d1 is 14.8 μm, d2 is 0.5 μm, and d1 / d2=14.8 / 0.5=29.6.

[0143] Example 5h The process is carried out in accordance with Example 1, except that d1 is 16.6 μm, d2 is 5.3 μm, and d1 / d2=16.6 / 5.3=3.13.

[0144] Example 5i The process is carried out in accordance with Example 1, except that d1 is 1.8 μm, d2 is 0.4 μm, and d1 / d2=1.8 / 0.4=4.5.

[0145] Example 6 This set of examples is used to illustrate the effects produced when the composition of the first particles is changed.

[0146] Example 6a The same process as in Example 1 was carried out, except that the first particles were made of methacrylate-ethylene copolymer.

[0147] Example 6b The same process is carried out as in Example 1, except that the first particles are made of acrylate-acrylonitrile-ethylene copolymer.

[0148] Example 7 Group This set of examples is used to illustrate the effects produced when the composition of the second particles is changed.

[0149] Example 7a The process is carried out in accordance with Example 1, except that the second particles are made of PVDF.

[0150] Example 7b The same process is carried out as in Example 1, except that the second particles are made of vinyl chloride-hexafluoroolefin copolymer.

[0151] Example 8 Group This set of examples is used to illustrate the effects of changing the specific selection of cyclic ethylene carbonate.

[0152] Example 8a The same process is carried out as in Example 1, except that all the cyclic ethylene carbonates are EC.

[0153] Example 8b The same process is carried out as in Example 1, except that the cyclic ethylene carbonate is all PC.

[0154] Example 9 Group Example 9a The method was carried out in accordance with Example 1, except that the coverage of the coating on the surface of the carrier layer was 8%, the average particle size of the silicon-carbon composite particles was 5.1 μm, the degree of graphitization of the silicon-carbon composite particles was 0.82, and the sphericity of the silicon-carbon composite particles was 0.95.

[0155] Example 9b The method is carried out in accordance with Example 1, except that the coverage of the coating on the surface of the carrier layer is 70%, the average particle size of the silicon-carbon composite particles is 11.7 μm, the degree of graphitization of the silicon-carbon composite particles is 0.46, and the sphericity of the silicon-carbon composite particles is 0.62.

[0156] Example 9c The process is carried out in accordance with Example 1, except that the silicon-based material is silicon oxide compound particles, and the average particle size of the silicon oxide compound particles is 9 μm.

[0157] Example 10 Group This set of examples is used to illustrate the effects produced when the composition of the third particles is changed.

[0158] Example 10a The process is carried out in accordance with Example 1, except that the third particle contains uracil.

[0159] Example 10b The process is carried out in accordance with Example 1, except that the component of the third particle is cytosine.

[0160] Example 10c The process is carried out in accordance with Example 1, except that the third particle is composed of melamine cyanurate.

[0161] Example 11 The process is carried out with reference to Example 1, except that the second slurry is not used, and the first slurry is coated on the surface of the heat-resistant layer and the other surface of the substrate layer, that is, the coating on the surface of the heat-resistant layer is the same as the coating on the other surface of the substrate layer.

[0162] Comparative Example 1 The method is carried out in accordance with Example 1, except that, within an area of ​​100 μm×100 μm on the surface of the coating, the number of primary particles of the first particles having a particle size less than or equal to 0.3 μm accounts for 0 in the number of primary particles of the first particles.

[0163] Comparative Example 2 The method is carried out in accordance with Example 1, except that, within an area of ​​100 μm×100 μm on the surface of the coating, the number of primary particles of the first particles having a particle size less than or equal to 0.3 μm accounts for 4.2% of the number of primary particles of the first particles.

[0164] Comparative Example 3 The process was carried out with reference to Example 1, except that the weight proportion of fluoroethylene carbonate in the electrolyte was 12.5%, the weight proportion of cyclic ethylene carbonate in the electrolyte was 5%, and the ratio of the weight of cyclic ethylene carbonate to the weight of fluoroethylene carbonate was 0.4.

[0165] Comparative Example 4 The process was carried out with reference to Example 1, except that the weight proportion of fluoroethylene carbonate in the electrolyte was 51%, and the ratio of the weight of cyclic ethylene carbonate to the weight of fluoroethylene carbonate was 0.36.

[0166] Comparative Example 5 The same procedure was followed as in Example 1, except that the weight proportion of fluoroethylene carbonate in the electrolyte was 33.6%, the weight proportion of cyclic ethylene carbonate in the electrolyte was 6.2%, and the ratio of the weight of cyclic ethylene carbonate to the weight of fluoroethylene carbonate was 0.18.

[0167] Comparative Example 6 The process was carried out with reference to Example 1, except that the weight proportion of fluoroethylene carbonate in the electrolyte was 31.2%, the weight proportion of cyclic ethylene carbonate in the electrolyte was 50%, and the ratio of the weight of cyclic ethylene carbonate to the weight of fluoroethylene carbonate was 1.6.

[0168] Comparative Example 7 The same procedure as in Example 1 was followed, except that no first particles were present in the coating.

[0169] Test Case The lithium ion batteries prepared in the examples and comparative examples were subjected to the following tests: 1. High temperature (60°C) cycle impedance change rate test The lithium-ion battery was transferred to a 60°C environment, allowed to stand for 30 minutes, discharged at a constant current of 0.2C to 3.0V, allowed to stand for 5 minutes, then charged at 0.5C to 4.53V, then charged at a constant voltage to a cutoff current of 0.05C, allowed to stand for 5 minutes, and the initial fully charged state impedance value R1 was measured using an electrochemical workstation. It was then discharged at a constant current of 0.7C to 3.0V, and then cycled for 30T according to the following steps: charging at 0.5C to 4.53V, then charging at a constant voltage to a cutoff current of 0.05C, allowed to stand for 5 minutes, and discharging at a constant current of 0.7C to 3.0V. After the cycle was completed, it was charged at 0.5C to 4.53V, then charged at a constant voltage to a cutoff current of 0.05C, allowed to stand for 5 minutes, and the full-charge state impedance value R2 after the cycle was measured using an electrochemical workstation. The impedance change rate was calculated as: [(R2-R1) / R1]×100%.

[0170] 2. Room temperature long cycle impedance change rate test The lithium-ion battery was transferred to a 25°C environment, allowed to stand for 30 minutes, discharged at a constant current of 0.2C to 3.0V, allowed to stand for 5 minutes, then charged at 0.5C to 4.53V, then charged at a constant voltage to a cutoff current of 0.05C, allowed to stand for 5 minutes, and the initial fully charged state impedance value R1 was measured using an electrochemical workstation. It was then discharged at a constant current of 0.7C to 3.0V, and then cycled 1000T according to the following steps: charging at 0.5C to 4.53V, then charging at a constant voltage to a cutoff current of 0.05C, allowed to stand for 5 minutes, and discharging at a constant current of 0.7C to 3.0V. After the cycle is completed, it is charged at 0.5C to 4.53V, then charged at a constant voltage to a cutoff current of 0.05C, allowed to stand for 5 minutes, and the full-charge state impedance value R2 after the cycle is measured using an electrochemical workstation. The impedance change rate is calculated as: [(R2-R1) / R1]×100%.

[0171] 3. Room temperature long cycle capacity retention test: At 25°C ± 2°C, charge the battery at 0.7C constant current and constant voltage to an upper voltage of 4.53V, cut off at 0.05C, and record the initial thickness P0. Then discharge the battery at 0.2C constant current to a lower voltage of 3.0V, with the initial discharge capacity recorded as C0. After resting for 10 minutes, the battery was cycled as follows: charge the battery at 3C constant current and constant voltage to 4.25V, cut off at 2C, switch to 2C constant current and constant voltage to 4.48V, cut off at 1.5C, switch to 1.5C constant current and constant voltage to an upper voltage of 4.53V, cut off at 0.18C, and rest for 5 minutes. Discharge the battery at 0.7C to a lower voltage of 3.0V. After 1000 cycles, charge the battery at 0.7C constant current and constant voltage to an upper voltage of 4.53V, cut off at 0.05C, and record the final thickness P1. Then discharge the battery at 0.2C constant current to a lower voltage of 4.53V, with the final discharge capacity recorded as C1. Capacity retention: C = C1 / C0*100%.

[0172] 4. High temperature cycle capacity retention test: At 45°C, charge at 0.7C constant current and constant voltage to an upper limit voltage of 4.53V, cut off at 0.05C, record the initial thickness P0, then discharge at 0.2C constant current to a lower limit voltage of 3.0V, record the initial discharge capacity as C0, and rest for 10 minutes. The cycle format is: charge at 3C constant current and constant voltage to 4.25V, cut off at 2C, switch to 2C constant current and constant voltage to 4.48V, cut off at 1.5C, switch to 1.5C constant current and constant voltage to an upper limit voltage of 4.53V, cut off at 0.18C, rest for 5 minutes, and discharge at 0.7C to a lower limit voltage of 3.0V. After 300T cycles, charge at 0.7C constant current and constant voltage to an upper limit voltage of 4.53V, cut off at 0.05C, record the final thickness P1, then discharge at 0.2C constant current to a lower limit voltage of 4.53V, and record the final discharge capacity as C1. Capacity retention rate: C=C1 / C0*100%.

[0173] The obtained results are recorded in Table 1.

[0174] Table 1 It can be seen from Table 1 that, by comparing the comparative example and the embodiment, the high-temperature impedance change rate of the battery in the embodiment is significantly reduced, and the high-temperature cycle capacity retention rate is significantly improved, indicating that by simultaneously controlling the proportion of the number of primary particles with a particle size of less than or equal to 0.3 μm in the primary particles of the first particles per unit area on the coating surface, the weight proportion of fluoroethylene carbonate in the electrolyte, and the weight ratio of cyclic ethylene carbonate to fluoroethylene carbonate, the high-temperature cycle impedance of the battery is reduced and the high-temperature long-cycle performance of the battery is improved.

[0175] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A battery, characterized in that: The battery includes a diaphragm, a negative electrode sheet and an electrolyte; the diaphragm includes a carrier layer and a coating located on one side or both sides of the carrier layer, the coating includes first particles, the components of the first particles include a first polymer, the first polymer is an ester-containing polymer, and within an area of ​​100 μm×100 μm on the surface of the coating, the number of primary particles of the first particles with a particle size less than or equal to 0.3 μm accounts for 0.01%-4% of the number of primary particles of the first particles; the electrolyte includes cyclic carbonate and fluoroethylene carbonate, the weight proportion of fluoroethylene carbonate in the electrolyte is 13%-50%, and the weight ratio of the cyclic carbonate to the fluoroethylene carbonate is (0.2-1.5):

1.

2. The battery according to claim 1, wherein The coating further includes second particles, the components of the second particles include a fluorine-containing polymer, and the battery satisfies the following relationship: 1≤d1 / d2≤25, wherein d1 is the average particle size of the secondary particles of the second particles, and d2 is the Dv95 of the first particles; And / or, the coating further comprises second particles, wherein the average particle size d1 of the secondary particles of the second particles is 2 μm-15 μm; And / or, the coating further comprises second particles, and the mass proportion of the second particles in the coating is 0%-90%; And / or, the mass proportion of the first particles in the coating is 10%-100%; And / or, the Dv95 of the first particles is 0.5 μm-5 μm.

3. The battery according to claim 2, wherein The monomers forming the fluorine-containing polymer include one or more of vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene and hexafluoropropylene; And / or, the fluorine-containing polymer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polyhexafluoropropylene, ethylene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer and tetrafluoroethylene-hexafluoropropylene copolymer.

4. The battery according to claim 1, wherein The thickness of the coating is 0.5 μm-5 μm; and / or, the coverage of the coating on the surface of the carrier layer is 8%-100%; and / or, the first particles are arranged in layers in the coating; And / or, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on one side or both sides of the negative electrode current collector, the coating corresponds to the negative electrode active layer, and the negative electrode active layer includes a silicon-based material, and the silicon-based material includes one or more of elemental silicon particles, silicon oxide particles, silicon-carbon composite particles, silicon-nitrogen composite particles and silicon alloy particles.

5. The battery according to claim 1, wherein The first polymer is an acrylic polymer, and the glass transition temperature of the first polymer is 40° C.-75° C.; and / or, the weight proportion of ester groups in the coating is 20%-60%; and / or, the monomers forming the first polymer 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; And / or, the first polymer includes one or more of polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, acrylate-acrylonitrile copolymer, acrylate-ethylene copolymer, acrylate-acrylonitrile-ethylene copolymer, styrene-acrylate monomer-acrylonitrile copolymer, ethylhexyl acrylate-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, methyl acrylate-acrylic acid-N,N-dimethylacrylamide copolymer, ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate copolymer, ethyl acrylate-acrylic acid-N,N-diethylacrylamide copolymer, and ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate.

6. The battery according to any one of claims 1 to 5, wherein At 80° C., after the diaphragm is compressed at a pressure of 2 MPa for 0.5 h, the compression rate of the diaphragm is 10%-50%; And / or, after the diaphragm is baked at 80° C. for 2 hours, the porosity of the diaphragm is 30%-60%.

7. The battery according to any one of claims 1 to 5, wherein The cyclic carbonate includes ethylene carbonate and / or propylene carbonate; And / or, the weight proportion of the cyclic carbonate in the electrolyte is 5%-50%; And / or, the carrier layer includes a substrate layer and a heat-resistant layer located on one side or both sides of the substrate layer, the heat-resistant layer includes third particles and a binder, and the ratio of the weight of the third particles to the weight of the binder is (30%-99%): (70%-1%).

8. The battery according to claim 4, wherein The average particle size of the silicon-carbon composite particles is 5 μm-12 μm; and / or, the degree of graphitization of the silicon-carbon composite particles is 0-0.85; And / or, the sphericity of the silicon-carbon composite particles is 0.6-1.

9. The battery according to claim 7, wherein The Dv10 of the third particles is 0.01 μm-1.5 μm; And / or, the thickness of the heat-resistant layer is 0.2 μm-5 μm; and / or, the thickness of the substrate layer is 2 μm-10 μm; And / or, the porosity of the substrate layer is 25%-70%.

10. The battery according to claim 7, wherein The components of the third particles include boehmite, aluminum oxide, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium oxide, 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-bromophenyl)-4,6-dimethyl-1,3, One or more of 5-triazine, 1-(4,6-diamino-1,3,5-triazine-2-yl)guanidine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, cyanuric chloride, 2,4,6-tris(2-pyridyl)triazine, 2,4,6-triphenyl-1,3,5-triazine, tris(tribromophenoxy)triazine, 2-amino-4,6-methoxy-1,3,5-triazine, uracil, cytosine, and lithium aluminum titanium phosphate; and / or, the binder comprises one or more of polyvinyl alcohol, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinyl pyrrolidone, polymethyl methacrylate, polybutyl methacrylate, styrene acrylic latex, polyacrylonitrile, polyethyl acrylate, polyacrylic acid, polyvinyl acetate, polyacrylate, polyurethane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), and copolymer systems derived from the above polymers; And / or, the components of the substrate layer include one or more of polyolefin, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide) and derivatives of the above polymers.

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