A battery

Abstract

The application 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 layer, the coating layer comprises first particles, the composition of the first particles comprises an ester group-containing polymer, and the number ratio of the primary particles of the first particles with a particle size less than or equal to 0.3 mu m in the area of 100 mu m*100 mu m on the surface of the coating layer to the primary particles of the first particles is 0.01%-4%; the electrolyte comprises a 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. The battery of the application forms a relatively stable and flexible SEI film on the surface of the negative electrode sheet through the synergistic cooperation of the diaphragm and the electrolyte, improves the interface stability between the diaphragm and the electrode sheet, and improves the high-temperature long-cycle performance of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery. BACKGROUND

[0002] The traditional graphite negative electrode is limited by its inherent low theoretical capacity, and it is difficult to meet the growing demand for high-performance energy storage. In this context, silicon materials have attracted much attention due to their ultra-high theoretical specific capacity and suitable lithium intercalation potential. However, silicon materials have a significant volume effect during the charge and discharge process, with a volume expansion rate of 280%-300% compared to the initial volume. This dramatic structural change directly leads to the instability of the electrode-electrolyte interface.

[0003] During the cycle process, the solid-state electrolyte interface (SEI) film formed on the surface of the silicon-based negative electrode will bear a huge mechanical stress due to the periodic expansion / contraction of the silicon material during the charge and discharge process. When the stress accumulation exceeds the fracture toughness of the SEI film, the interface protection layer will break, exposing the fresh silicon surface. The newly exposed active material will continuously react with the electrolyte, inducing the 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 the cumulative rise of the interface impedance, ultimately leading to rapid capacity decay and rapid deterioration of cycle performance.

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

[0005] To solve the problem in the prior art that the repeated repair and regeneration of the SEI film caused by the volume expansion of the silicon material leads to rapid capacity decay and rapid deterioration of cycle performance, the present application provides a battery. The battery of the present application can form a relatively stable and flexible SEI film on the surface of the negative electrode sheet through the synergistic cooperation of the separator and the electrolyte, thereby reducing the risk of SEI film damage during the expansion of the silicon-based material, improving the interface stability between the separator and the electrode sheet, reducing the high-temperature cycle impedance of the battery, and improving the high-temperature long cycle performance of the battery.

[0006] To achieve the above object, the present application provides a battery, which comprises a separator, a negative electrode sheet and an electrolyte; the separator comprises a carrier layer and a coating layer on one side or both sides of the carrier layer, the coating layer comprises first particles, and the composition of the first particles comprises a first polymer, which is an ester group-containing polymer; in an area of 100 mu m x 100 mu m on the surface of the coating layer, the number ratio of primary particles with a particle size less than or equal to 0.3 mu m in the primary particles of the first particles is 0.01%-4%; the electrolyte comprises a 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.

[0007] Compared with the prior art, the present application has at least the following advantages:

[0008] The battery of the present application can ensure that the trace amount of first particles in the separator, under the joint action of the cyclic carbonate and the fluoroethylene carbonate, can realize a high matching degree between the first particles and the cyclic carbonate and the fluoroethylene carbonate in the electrolyte, so that the small-particle-size first polymer particles can be excessively swollen under the action of the cyclic carbonate, the small-particle-size first particles after excessive swelling can be slightly dissolved due to corrosion by high content FEC, the small-particle-size first particles can dissolve a trace amount of first polymer and / or ester group-containing groups, and the small-particle-size first particles, the fluoroethylene carbonate and the small-particle-size first polymer and / or ester group-containing groups can jointly form a stable and flexible SEI film on the surface of the negative electrode sheet, thereby reducing the risk of rupture of the SEI film in the expansion process of the silicon material, improving the cycle stability of the battery, improving the high-temperature adhesion between the separator and the electrode sheet, reducing the high-temperature cycle impedance of the battery, and improving the high-temperature long cycle performance of the battery.

[0009] Other features and advantages of the present application will be described in detail in the following specific embodiments.

[0010] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as exactly that endpoint. Any values that fall within common BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1One of the surface SEM images of the separator of the present application is shown.

[0012] Figure 2 One of the surface SEM images of the separator of the present application is shown. DETAILED DESCRIPTION

[0013] The detailed description of the present application is described below. It should be understood that the detailed description described herein is only for illustration and explanation of the present application, and is not intended to limit the present application. In this paper, the data range includes the end point without special explanation.

[0014] It should be noted that the "first", "second" and other numerical representation in the present application are only used to distinguish different substances or use methods, and do not represent the difference in order.

[0015] The present application provides a battery, the battery comprising a separator, a negative electrode sheet and an electrolyte; the separator comprises a carrier layer and a coating layer located on one side or both sides of the surface of the carrier layer, the coating layer comprises first particles, the composition of the first particles comprises a first polymer, the first polymer is an ester-containing polymer, and the number of primary particles of the first particles with 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) in an area of 100 μm x 100 μm on the surface of the coating layer accounts for 0.01%-4% (for example, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5% or 4%) of the number of primary particles of the first particles; the electrolyte comprises a cyclic carbonate and a fluoroethylene carbonate, the weight percentage of the fluoroethylene carbonate in the electrolyte is 13%-50% (13%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%), and the ratio of the weight of the cyclic carbonate to the weight of 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).

[0016] In the separator, the coating layer can be located on one side surface of the carrier layer, or on both side surfaces of the carrier layer. When the coating layer is located on both side surfaces of the carrier layer, the coating layers located on both side surfaces of the carrier layer can be the same or different.

[0017] In the present application, the first particles can include primary particles. The number ratio of the primary particles of the first particles with a particle size of 0.3 μm or less in the primary particles of the first particles in a 100 μm x 100 μm area on the surface of the coating refers to the number ratio of the primary particles of the first particles with a particle size of 0.3 μm or less in the total number of the primary particles in the first particles in a 100 μm x 100 μm area on the surface of the coating away from the carrier layer. Specifically, the number ratio can be tested by the following method: on the surface of the coating away from the carrier layer, 100 μm x 100 μm is randomly selected, it can be understood that when the coating is discontinuously coated, 100 μm x 100 μm of the coated area should be selected, and the particle size of all the first particles is measured and statistically processed on the scanning image of the SEM combined with a graphic analysis software (for example, ImageJ, NanoMeasurer, Matlab, etc.), the total number of the primary particles of the first particles in the area is counted as M, wherein the number of the primary particles with a particle size of 0.3 μm or less is N, and then the number ratio of the primary particles of the first particles with a particle size of 0.3 μm or less in the primary particles of the first particles in a 100 μm x 100 μm area on the surface of the coating is (N / M) x 100%, and the above operation is repeated 5 times, and the average value is taken as the final test result.

[0018] It is found through research that a small amount of first particles with a small particle size can be excessively swollen under the action of cyclic carbonate and can be eroded by a high content of fluoroethylene carbonate, so that the first polymer or ester group-containing group is dissolved and eluted from the small particle size first particles, the first polymer and / or ester group-containing group can jointly act with the fluoroethylene carbonate on the surface of the negative electrode sheet to form a stable and flexible SEI film, 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 separator and the electrode sheet, reducing the high-temperature cycle impedance of the battery, and improving the high-temperature long cycle performance of the battery.

[0019] In order to ensure that an appropriate amount of first polymer and / or ester group-containing group can be eluted from the first particles, and at the same time cooperate with the fluoroethylene carbonate to generate a stable and flexible SEI, and ensure the overall structural stability of the coating containing the first particles and avoid excessive elution of the first polymer, the present application controls the number ratio of the primary particles with a particle size of 0.3 μm or less in the primary particles of the first particles in a unit area on the surface of the coating, the weight ratio of the fluoroethylene carbonate in the electrolyte, and the weight ratio of the cyclic ethylene carbonate and the fluoroethylene carbonate.

[0020] The primary particles with smaller particle sizes are more prone to excessive swelling under the action of cyclic ethylene carbonate. Controlling the proportion of the primary particles with particle sizes less than or equal to 0.3 μm in the primary particles of the first particles in a unit area of the coating surface within the above range can ensure that there are appropriate primary particles with smaller particle sizes in the coating, so that appropriate first polymers and / or ester group-containing groups are dissolved under the swelling action of cyclic ethylene carbonate and the corrosion action of fluoroethylene carbonate, thereby enabling the fluoroethylene carbonate to synergistically generate an SEI film with higher stability and better flexibility, thereby improving the cycle stability of the battery, reducing the high-temperature cycle impedance of the battery, and improving the high-temperature long-cycle performance of the battery. Moreover, controlling the proportion of the primary particles with particle sizes less than or equal to 0.3 μm in the primary particles of the first particles in a unit area of the coating surface within the above range can also ensure that there are more primary particles with larger particle sizes in the coating. The primary particles with larger particle sizes are not prone to swelling under the action of cyclic carbonate or corrosion under the action of fluoroethylene carbonate, which can ensure the overall structural stability of the coating containing the first particles and avoid excessive dissolution of the first polymers and / or ester group-containing groups. Meanwhile, controlling the weight ratio of cyclic ethylene carbonate to fluoroethylene carbonate within the above range can enable the cyclic ethylene carbonate and the fluoroethylene carbonate to synergistically act. Under the cooperation of the two, trace amounts of small-particle-size first particles can be excessively swollen under the action of cyclic ethylene carbonate, and the small-particle-size first particles that are excessively swollen can cause trace amounts of first polymers and / or ester group-containing groups to be dissolved from the first particles under the corrosion of fluoroethylene carbonate, so that the first polymers and / or ester group-containing groups can synergistically act with the fluoroethylene carbonate to form a relatively stable and flexible SEI film on the surface of the negative electrode sheet. Meanwhile, controlling the weight proportion of fluoroethylene carbonate in the electrolyte within the above range can ensure that there is an appropriate amount of fluoroethylene carbonate in the electrolyte, which can avoid excessive corrosion of the first particles by the fluoroethylene carbonate, which affects the overall structural stability of the first particles, and can also avoid insufficient corrosion of the first particles by the fluoroethylene carbonate, which cannot cause the first polymers and / or ester group-containing groups to be dissolved or dissolved in an excessively small amount, and cannot synergistically act with the fluoroethylene carbonate to form a relatively stable and flexible SEI film on the surface of the negative electrode sheet.

[0021] When the weight ratio of cyclic carbonate to fluoroethylene carbonate is less than 0.2:1, the weight percentage of fluoroethylene carbonate in the electrolyte is too high or the weight percentage of cyclic carbonate is too low, the mechanical stability of the coating in the separator is poor, which leads to a decrease in the structural mechanical strength of the coating of the separator, an increase in the interface impedance between the separator and the pole piece, and is not conducive to the adhesion of the separator at high temperature and high temperature cycle. When the weight ratio of cyclic carbonate to fluoroethylene carbonate is greater than 1.5:1, the weight percentage of fluoroethylene carbonate in the electrolyte is too low or the weight percentage of cyclic carbonate is too high, the swelling degree of the first particles is too large, which reduces the lithium ion permeability of the separator, increases the battery impedance, or the dissolved first polymer and / or ester group-containing group cannot cooperate with enough fluoroethylene carbonate to form a stable and flexible SEI film on the negative pole piece surface, thereby unable to effectively improve the rupture of the SEI film, not conducive to improving the cycle stability of the battery and reducing the high temperature cycle impedance of the battery.

[0022] It can be understood that in the present application, the corrosion of fluoroethylene carbonate on the first particles 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, and part of the group in a single first particle can also be dissolved. The particle state of a single first particle can also be completely retained.

[0023] In the present application, the ester group dissolved from the first particles is not in the form of a group, but a substance with an ester group, which can be one or more of small molecules, monomers, oligomers and ions.

[0024] In the present application, by simultaneously controlling the number percentage of primary particles of the first particles with a particle size less than or equal to 0.3 μm in the unit area of the coating surface, the weight percentage of fluoroethylene carbonate in the electrolyte, and the weight ratio of cyclic carbonate to fluoroethylene carbonate, compared with the prior art, the high temperature cycle impedance of the battery can be reduced and the high temperature long cycle performance of the battery can be improved. To further improve the effect, one or more of the technical features can be further optimized.

[0025] In an example, the number percentage of the number of primary particles of the first particles with a particle size less than or equal to 0.3 μm in the area of 100 μm x 100 μm of the surface of the coating is 1%-3.5% in the number of primary particles of the first particles.

[0026] In an example, the Dv95 of the first particles is 0.5 pm-5 pm (e.g., 0.5 pm, 1 pm, 1.5 pm, 2 pm, 2.5 pm, 3 pm, 3.5 pm, 4 pm, 4.5 pm, or 5 pm). In the present application, the Dv95 is the particle size corresponding to the cumulative particle size distribution reaching 95% in the volume particle size distribution of the first particles. In the present application, the volume particle size distribution of the first particles can be measured and statistically processed to obtain the Dv95 by randomly selecting 100 pm x 100 pm in the SEM image of the coating surface, combined with graphic analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.). The Dv95 of the first particles can also be obtained by laser particle size analyzer test, for example, before preparing the separator, the first particles are measured by laser particle size analyzer to obtain the Dv95 of the first particles.

[0027] In an example, as shown in FIGS. 1A and 1B, the first particles are arranged in a stacked manner in the coating. The red circles in the figures represent the first particles, and only part of the first particles are marked in the figures, not all of the first particles. It can be understood that the stacked arrangement means that the first particles in the coating have only one layer or multiple layers stacked in the thickness direction of the separator, and there are no large-particle-size agglomerates. Figure 1 Figure 2 As shown in FIGS. 1A and 1B, the first particles are arranged in a stacked manner in the coating. The red circles in the figures represent the first particles, and only part of the first particles are marked in the figures, not all of the first particles. It can be understood that the stacked arrangement means that the first particles in the coating have only one layer or multiple layers stacked in the thickness direction of the separator, and there are no large-particle-size agglomerates.

[0028] In an example, the mass percentage of the first particles in the coating is 10%-100% (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%).

[0029] In an example, the first polymer is an ester-containing and fluorine-free polymer.

[0030] In an example, the first polymer is an acrylate polymer.

[0031] In an 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, stearyl acrylate, ethyl acrylate, cyclohexyl acrylate, and 2-hydroxyethyl acrylate.

[0032] ​In an example, the first polymer comprises one or more of polymethyl methacrylate, poly(ethylhexyl acrylate), poly(butyl acrylate), acrylate-acrylonitrile copolymer (e.g., methyl methacrylate-acrylonitrile copolymer), acrylate-ethylene copolymer (e.g., methacrylate-ethylene copolymer), acrylate-acrylonitrile-ethylene copolymer, copolymer of styrene-acrylate monomers-acrylonitrile, copolymer of ethylhexyl acrylate-methyl methacrylate, copolymer of butyl acrylate-methyl methacrylate, methyl acrylate-N,N-dimethyl acrylamide copolymer, ethyl acrylate-acrylic acid-ethyl 2-(diethylamino)acrylate copolymer, ethyl acrylate-acrylic acid-N,N-diethyl acrylamide copolymer, ethyl acrylate-acrylic acid-ethyl 2-(diethylamino)acrylate.

[0033] In an example, the first polymer has a glass transition temperature of 40°C to 75°C (e.g., 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, or 75°C).

[0034] In an example, the coating comprises ester groups.

[0035] In an example, the coating comprises ester groups.

[0036] In an example, the coating further comprises second particles, the second particles comprising a fluoropolymer. As shown in Figure 1 and Figure 2 The second particles are agglomerated particles, and the green circles represent the second particles. It is understood that only some of the second particles are shown in the figure, not all of the second particles.

[0037] In an example, the monomers that form the fluoropolymer comprise one or more of vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, and hexafluoropropylene.

[0038] In an example, the fluoropolymer comprises one or more of poly(vinylidene fluoride), poly(tetrafluoroethylene), poly(vinyl fluoride), poly(hexafluoropropylene), fluorovinyl-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer.

[0039] In one example, the second particles have a mass percentage in the coating layer of 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 percentage of the second particles in the coating layer is 0, it means that there are no second particles in the coating layer.

[0040] In one example, the second particles include secondary particles. In the present application, the secondary particles refer to agglomerates formed by agglomeration of more than 4 primary particles.

[0041] In one example, the average particle size dl of the secondary particles of the second particles is 2-15 μm (e.g., 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).

[0042] In one example, the average particle size dl of the secondary particles of the second particles is 3-10 μm.

[0043] In the present application, the average particle size of the secondary particles of the second particles can be tested by the following method: on the scanning image of the sample coating layer surface obtained by SEM, a square or rectangle with the smallest area completely surrounding one secondary particle is drawn, i.e., a square or rectangle with the edges of the secondary particle and the four edges of the square or rectangle being in contact is drawn, 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, the particle sizes of any 100 secondary particles in a 10 μm*10 μm area randomly selected on the coating surface are measured, and the number average is the average particle size; the above operation is repeated 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 image, the number average of the particle sizes of any 100 secondary particles in the image is taken as the average particle size of the secondary particles, and when 100 secondary particles cannot be observed in the image, multiple images are taken, the number average of the particle sizes of the total 100 secondary particles is taken as the average particle size. The surface of the coating layer can be observed using a scanning electron microscope (S-3400N manufactured by Hitachi, Ltd.).

[0044] In an example, 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 the above relationship can ensure that the coating layer including the first particles and the second particles is not excessively swollen at room temperature, thereby improving the mechanical stability of the coating layer at room temperature, improving the interface stability between the separator and the pole piece at room temperature, reducing the room temperature cycle impedance of the battery, and improving the room temperature cycle performance of the battery.

[0045] In an example, the battery satisfies the following relationship: 1.5≤d1 / d2≤20.

[0046] According to a specific embodiment of the battery, d1 is 2 μm-15 μm, d2 is 0.5 μm-5 μm, and the battery satisfies the following relationship: 1≤d1 / d2≤25.

[0047] According to a specific embodiment of the battery, 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.

[0048] In an example, the thickness of the coating layer is 0.5 μm-5 μm (e.g., 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).

[0049] In an example, the weight percentage of the first particles is 10%-45% (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, or 45%) and the weight percentage of the second particles is 55%-90% (e.g., 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%) based on the total weight of the coating layer.

[0050] In an example, the coverage of the coating layer on the surface of the carrier layer is 8-100% (e.g., 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%). In the present disclosure, the coverage of the coating layer on the surface of the carrier layer refers to the ratio of the area of the orthographic projection of the coating layer on one side of the carrier layer on the surface of the carrier layer on the same side (i.e., the surface of the carrier layer on the side with the coating layer). When the coating layer is on both sides of the carrier layer, the coverage of the coating layer on the two sides can be the same or different. The coverage of the coating layer on the surface of the carrier layer can be tested by the following method: obtaining a micrograph of the surface of the coating layer using SEM, randomly dividing an area of 100 pm x 100 pm in the image (e.g., 100 pm x 100 pm), dividing the area into 100 x 100 uniform squares, and counting the number of squares occupied by the coating layer. If the coverage area of the orthographic projection of the coating layer in a square exceeds half of the area of the square, the square is occupied by the coating layer; otherwise, the square is not occupied by the coating layer. The total number of squares occupied by the coating layer is recorded as X, and the coverage is (X / 100*100)*100%. The above operation is repeated 5 times, and the average value of the 5 times is the coverage of the coating layer on the surface of the carrier layer. 2

[0051] In an example, the carrier layer comprises a substrate layer and a heat-resistant layer on one or both sides of the substrate layer.

[0052] In an example, the diaphragm comprises a substrate layer, a heat-resistant layer, and a coating layer, the heat-resistant layer is on one side of the substrate layer, and the coating layer is on the other side of the substrate layer.

[0053] In an example, the diaphragm comprises a substrate layer, a heat-resistant layer, and a coating layer, the heat-resistant layer is on one side of the substrate layer, and the coating layer is on the surface of the heat-resistant layer and the other side of the substrate layer.

[0054] In an example, the diaphragm comprises a substrate layer, a heat-resistant layer, and a coating layer, the heat-resistant layer is on both sides of the substrate layer, and the coating layer is on the surface of the heat-resistant layer.

[0055] In an example, the heat-resistant layer comprises third particles and a binder.

[0056] ​In one example, the components of the third particles include one or more of 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 trithiocyanate, melamine cyanurate, sym-trisamino triazine, 2-(4-bromophenyl)-4,6-dimethyl-1,3,5-triazine, 1-(4,6-diamino-1,3,5-triazin-2-yl)guanidine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, trichloro cyanuric acid, 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.

[0057] In one example, the binder includes 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 terephthalamide, and a copolymer system derived from the above polymers.

[0058] In one example, the ratio of the weight of the third particles to the weight of 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 can be appreciated that the weight percentage of the third particles in the heat-resistant layer can range from 30% to 99%, and the weight percentage of the binder in the heat-resistant layer can range from 70% to 1%.

[0059] In one example, the binder is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, poly-p-phenylene terephthalamide, poly-m-phenylene terephthalamide, and a copolymer system derived from the above polymers. The mass percentage of the binder in the heat-resistant layer is 30%-70% (e.g., 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%).

[0060] In an example, 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 mass percentage of the binder in the heat-resistant layer is 35-50%.

[0061] In an example, the binder is selected from one or more of polyvinyl alcohol, styrene butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polymethyl methacrylate, polybutyl methacrylate, styrene-acrylic latex, polyacrylonitrile, polyethyl acrylate, polyacrylic acid, polyvinyl acetate, polyacrylate, polyurethane, and copolymers derived from the above polymers. The mass percentage of the binder in the heat-resistant layer is 1-10% (e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%).

[0062] In an example, the heat-resistant layer further comprises a thickening agent, which comprises one or more of methyl cellulose (CMC), sodium carboxymethyl cellulose (CMC-Na), and lithium carboxymethyl cellulose (CMC-Li).

[0063] In an example, the weight percentage of the thickening agent 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 thickening agent in the heat-resistant layer is 0, it means that there is no thickening agent in the heat-resistant layer.

[0064] In an example, the Dv10 of the third particles is 0.01 μm-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 in the above range can improve the adhesion strength between the heat-resistant layer and the coating layer, while improving the softness of the heat-resistant layer, improving the fit between the separator and the pole piece, improving the lithium ion transmission rate, and improving the room temperature cycle performance of the battery.

[0065] In the present application, Dv10 is the particle size corresponding to the cumulative particle size distribution reaching 10% in the volume particle size distribution of the third particles. The Dv10 of the third particles can be obtained by laser particle size analyzer test.

[0066] In an example, the thickness of the heat-resistant layer is 0.2 μm-5 μm (e.g., 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).

[0067] 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).

[0068] In one example, the porosity of the substrate layer is 25%-70% (eg, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%).

[0069] 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.

[0070] 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%).

[0071] 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.

[0072] According to a specific embodiment, 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 total number of primary particles of the first particles in an area of 100 μm x 100 μm on the surface of the coating; 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 percentage of ester groups in the coating is 20%-60%; the first polymer comprises one or more of polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, acrylate-acrylonitrile copolymer, acrylate-acrylonitrile-ethylene copolymer, styrene-acrylate monomer-acrylonitrile copolymer, ethylhexyl acrylate-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, methyl acrylate-N,N-dimethyl acrylamide copolymer, ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate copolymer, ethyl acrylate-N,N-diethyl acrylamide copolymer, and ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate copolymer; the fluorine-containing polymer comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyfluoroethylene, polyhexafluoropropylene, vinyl fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer; and the separator satisfying the above characteristics can have a compression rate of 10%-50% after being compressed at a pressure of 2 MPa for 0.5 h at 80℃.

[0073] In an example, the porosity of the separator is 30%-60% (e.g., 30%, 33%, 35%, 38%, 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58%, or 60%) after the separator is baked at 80℃ for 2 h.

[0074] In the present application, the porosity of the separator can be tested by the following method: the separator is kneaded into a ball and inserted into a 3.5 mL sample cup, the sample cup containing the sample is placed in a true density tester, a closed test system, and helium is introduced according to the program, and the porosity of the sample to be tested is calculated according to the Boyle law (PV=nRT) by detecting the pressure of the gas in the sample chamber and the expansion chamber. Porosity=(V1-V2) / V1*100%, V1: apparent volume of the sample, V2: true volume of the sample.

[0075] According to a specific embodiment, in an area of 100 μm x 100 μm of 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 total 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 percentage of ester groups in the coating is 20%-60%; the first polymer comprises one or more of polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, acrylate-acrylonitrile copolymer, acrylate-acrylonitrile-ethylene copolymer, copolymer of styrene-acrylate monomer-acrylonitrile, copolymer of ethylhexyl acrylate-methyl methacrylate, copolymer of butyl acrylate-methyl methacrylate, methyl acrylate-acrylic acid-N,N-dimethyl acrylamide copolymer, ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate copolymer, ethyl acrylate-acrylic acid-N,N-diethyl acrylamide copolymer, and ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate; the fluorine-containing polymer comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyfluoroethylene, polyhexafluoropropylene, vinyl fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer; the separator satisfying the above characteristics can have a porosity of 30%-60% after being baked at 80℃ for 2 h.

[0076] According to a specific embodiment, 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 total number of primary particles of the first particles in an area of 100 μm x 100 μm on the surface of the coating; 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 percentage of ester groups in the coating is 20%-60%; the first polymer comprises one or more of polymethyl methacrylate, poly (ethylhexyl acrylate), poly (butyl acrylate), acrylate-acrylonitrile copolymer, acrylate-acrylonitrile-ethylene copolymer, styrene-acrylate monomer-acrylonitrile copolymer, copolymer of ethylhexyl acrylate-methyl methacrylate, copolymer of butyl acrylate-methyl methacrylate, methyl methacrylate-acrylic acid-N,N-dimethyl acrylamide copolymer, ethyl acrylate-acrylic acid-2-(diethylamino) ethyl acrylate copolymer, ethyl acrylate-acrylic acid-N,N-diethyl acrylamide copolymer, and ethyl acrylate-acrylic acid-2-(diethylamino) ethyl acrylate; the fluorine-containing polymer comprises one or more of poly (vinylidene fluoride), poly (tetrafluoroethylene), poly (fluoroethylene), poly (hexafluoropropylene), vinyl fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer; the separator satisfying the above characteristics can have a compression rate of 10%-50% after being compressed at a pressure of 2 MPa for 0.5 h at 80℃, and a porosity of 30%-60% after being baked at 80℃ for 2 h.

[0077] In an example, the weight percentage of fluoroethylene carbonate in the electrolyte is 15%-35%.

[0078] In an example, the cyclic carbonate comprises ethylene carbonate and / or propylene carbonate.

[0079] In an example, the weight percentage of the cyclic carbonate in the electrolyte is 5%-50% (e.g., 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%).

[0080] In an example, the weight percentage of the cyclic carbonate in the electrolyte is 10%-25%.

[0081] In an example, the ratio of the weight of the cyclic ethylene carbonate to the weight of the fluoroethylene carbonate is (0.6-1.1):1.

[0082] According to a specific embodiment, the weight percentage of fluoroethylene carbonate in the electrolyte is 13%-50%, the weight percentage of the cyclic carbonate in the electrolyte is 5%-50%, and the ratio of the weight of the cyclic carbonate to the weight of the fluoroethylene carbonate is (0.2-1.5):1.

[0083] According to a specific embodiment, the weight percentage of fluoroethylene carbonate in the electrolyte is 15%-35%, the weight percentage of the cyclic carbonate in the electrolyte is 10%-25%, and the ratio of the weight of the cyclic carbonate to the weight of the fluoroethylene carbonate is (0.6-1.1):1.

[0084] In an example, the electrolyte includes a lithium salt, an organic solvent, and an additive.

[0085] In an example, the lithium salt includes one or more of lithium hexafluorophosphate, lithium bis-trifluoromethanesulfonimide, lithium bisfluorosulfonimide, lithium difluorophosphate, lithium tetrafluoroborate, lithium bisoxalate borate, lithium difluoro oxalate borate, lithium difluoro bisoxalate phosphate.

[0086] In an 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), and ethyl propionate (EP), propyl propionate (PP), ethyl butyrate, propyl acetate, ethyl difluoroacetate.

[0087] In an example, the additive includes a negative electrode surface film-forming additive, a positive electrode surface film-forming additive, a positive and negative electrode current collector surface film-forming additive; and can also include an additive capable of improving certain performance of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc. The additive can be one or more of a dinitrile compound, a trinitrile compound, etc. nitrile compound, fluoro chain carbonate, fluoro carboxylic acid ester, sulfur-containing compound.

[0088] Dinitrile compounds include, but are not limited to, one or more of butanedinitrile, pentanedinitrile, hexanedinitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanoctane, 1,9-dicyanononane, 1,10-dicyanodecane, 1,12-dicyanododecane, tetramethyl butanedinitrile, 2-methyl pentanedinitrile, 2,4-dimethyl pentanenitrile, 2,2,4,4-tetramethyl pentanedinitrile, 1,5-dicyanopentane, 2,6-dicyanoheptane, 2,7-dicyanoctane, 2,8-dicyanononane, 1,6-dicyanodecane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, 3,5-dioxa-heptanedinitrile, 1,4-bis(cyanoethoxy)butane, ethylene glycol bis(2-cyanoethyl) ether, diethylene glycol bis(2-cyanoethyl) ether, triethylene glycol bis(2-cyanoethyl) ether, tetraethylene glycol bis(2-cyanoethyl) ether, 3,6,9,12,15,18-hexaoxaicosanedinitrile, 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-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.

[0089] Trinitrile compounds include, but are not limited to, one or more of 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 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.

[0090] Sulfur-containing compounds include, but are not limited to, one or more of 1,3-propane sulfone, ethylene sulfate, ethylene sulfate, cyclic sulfate, chain sulfate, chain sulfonate, cyclic sulfonate, chain sulfite, cyclic sulfite, chain sulfone, cyclic sulfone.

[0091] 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, or bis(trifluoroethyl) carbonate.

[0092] In one example, the weight percentage of the lithium salt is 5-30% (e.g., 5%, 10%, 15%, 20%, 25%, or 30%) based on the total weight of the electrolyte, 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%) based on the total weight of the electrolyte, 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%) based on the total weight of the electrolyte. When the weight percentage of the organic solvent in the electrolyte is 0, it means that there is no organic solvent in the electrolyte. When the weight percentage of the additive in the electrolyte is 0, it means that there is no additive in the electrolyte.

[0093] In one example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer on one side or both sides of the negative electrode current collector, and the coating layer corresponds to the negative electrode active layer. It can be understood that when the coating layer is on one side of the carrier layer, the negative electrode sheet corresponds to the side of the separator with the coating layer, and the positive electrode sheet corresponds to the other side of the separator; when the coating layer is on both sides of the carrier layer, the negative electrode sheet corresponds to any side of the separator with the coating layer, and the positive electrode sheet corresponds to the other side of the separator.

[0094] In one example, the separator includes a carrier layer and a coating layer on both sides of the carrier layer, the coating layer corresponding to the negative electrode active layer is composed of first particles, and the coating layer corresponding to the positive electrode active layer is composed of first particles and second particles.

[0095] 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 oxide particles, silicon-carbon composite particles, silicon-nitrogen composite particles, and silicon alloy particles.

[0096] In one example, the average particle size of the silicon-carbon composite particles is 5-12 μm (e.g., 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, or 12 μm).

[0097] 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.).

[0098] 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.

[0099] 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).

[0100] In an example, the silicon-carbon composite particles have a sphericity of 0.6-1 (e.g., 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, or 1).

[0101] In the present disclosure, the sphericity of the silicon-carbon composite particles can be tested by taking a particle image on the surface of the negative electrode active layer by a scanning electron microscope (SEM), drawing the smallest rectangle that completely surrounds one particle on the obtained scanning image using image processing software, i.e., drawing a rectangle whose four edges are connected to the edges of the silicon-carbon composite particle, measuring the longest side and the shortest side of the rectangle, and calculating the sphericity = shortest side / longest side.

[0102] In an example, the negative electrode active layer includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder, and the negative electrode active material includes a silicon-based material and a carbon-based material. The negative electrode active layer includes silicon elements.

[0103] In an example, the carbon-based material includes graphite.

[0104] In an example, the weight content of the negative electrode active material is 95%-98.5% (e.g., 95%, 96%, 97%, 98%, or 98.5%) based on the total weight of the negative electrode active material layer.

[0105] In an example, the weight content of silicon elements 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.

[0106] In an example, the weight content of silicon elements is 7%-30% based on the total weight of the negative electrode active material layer.

[0107] In an example, the negative electrode active material layer further includes a negative electrode conductive agent and a negative electrode binder.

[0108] In an example, the negative electrode conductive agent includes one or more of furnace black, acetylene black, ketjen black, and carbon nanotube.

[0109] In an example, the negative electrode binder includes one or more of acrylic-acrylonitrile copolymer, polyvinylidene fluoride, vinylidene-hexafluoropropylene copolymer, polyacrylic acid (PAA), carboxymethyl cellulose (CMC), and styrene butadiene rubber (SBR).

[0110] In one example, the weight content of the negative electrode conductive agent is 0.1-1.5% (e.g., 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% (e.g., 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, or 3.5%) based on the total weight of the negative electrode active material layer.

[0111] In one example, 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 on at least one surface of the positive electrode current collector. The positive electrode active layer can be composed according to the convention in the art.

[0112] In one example, the battery is a lithium ion secondary battery.

[0113] The present application will be described in detail below by way of examples. The examples described in the present application are only a part of the examples of the present application, rather than all the examples. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present application.

[0114] The following examples are used to illustrate the battery of the present application.

[0115] Example 1

[0116] (1) Separator

[0117] The third particles (aluminum oxide) and polyacrylic acid (binder) were mixed, and after sufficient stirring, a mixed slurry with a solid content of 25% was obtained. The mixed slurry was coated on one side surface of the base material (PE) by gravure roll, and after passing through a 60°C multi-section oven, a heat-resistant layer was dried to form a heat-resistant layer with a thickness of 1 μm. The weight ratio of aluminum oxide to polyacrylic acid in the mixed slurry was 96:4%.

[0118] The first particles (methyl methacrylate-acrylonitrile copolymer) and the second particles (PVDF-HFP copolymer) were dispersed in deionized water (wherein the mass ratio of the first particles in the coating layer was 40%, and the mass ratio of the second particles in the coating layer was 60%), and after sufficient stirring, a first slurry with a solid content of 10% was obtained. The first particles (methyl methacrylate-acrylonitrile copolymer) were dispersed in deionized water, and after sufficient stirring, a second slurry with a solid content of 10% was obtained. The first slurry was coated on the surface of the heat-resistant layer by gravure roll, and the second slurry was coated on the other side surface of the base material layer, and after passing through a 60°C multi-section oven, a coating layer was dried to form a coating layer.

[0119] Wherein, in the area of 100 μm x 100 μm of 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 1.4% of the number of primary particles of the first particles, the Dv95 of the first particles is 0.9 μm, the average particle size d1 of the secondary particles in the second particles is 6.2 μm, d1 / d2=6.2 / 0.9=6.89, and the coverage of the coating on the surface of the carrier layer is 20%.

[0120] (2) Electrolyte

[0121] In an argon-filled glove box (moisture <1 ppm, oxygen <1 ppm), ethylene carbonate, propylene carbonate, propyl propionate, ethyl propionate solvents were mixed into a uniform solvent, and LiPF6, 1,3,6-hexane trinitrile, fluoroethylene carbonate were slowly added. After stirring uniformly, the electrolyte was obtained, wherein the weight percentage of LiPF6 in the electrolyte was 16%, the weight percentage of 1,3,6-hexane trinitrile was 3%, the weight percentage of fluoroethylene carbonate was 21.1%, the weight percentage 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.

[0122] (3) Anode sheet

[0123] The carbon-based material (graphite), silicon-based material (silicon-carbon composite particles, and the average particle size of the silicon-carbon composite particles was 8 μm, the graphitization degree was 0.1, and the sphericity was 0.8), negative electrode conductive agent (carbon black: carbon nanotube (weight ratio)=1:1), carboxymethyl cellulose sodium (CMC), and butadiene rubber were mixed in the water solvent in a weight ratio of 86:12:1:0.5:0.5, and continuously stirred into a uniform and flowing negative electrode slurry under the action of a stirrer. Subsequently, the slurry was coated on both sides of the current collector copper foil with a thickness of 10 μm to form a negative electrode active layer, and then sent into a 120°C vacuum oven for drying for 6 h, followed by rolling, slitting, to obtain the negative electrode sheet.

[0124] (4) Positive electrode sheet

[0125] The lithium cobaltate, binder polyvinylidene fluoride (PVDF 500), and conductive material (SuperP: carbon nanotube=2:1) were mixed in N-methyl pyrrolidone (NMP) solvent in a weight ratio of 98:2:2, and continuously stirred into a uniform and flowing positive electrode slurry under the action of a stirrer. Subsequently, the positive electrode slurry was coated on an aluminum foil with a thickness of 10 μm, and then sent into a 120°C vacuum oven for drying for 6 h, followed by rolling, slitting, to obtain the required positive electrode sheet.

[0126] (5) Lithium ion battery

[0127] 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.

[0128] Example 2 group

[0129] 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.

[0130] Example 2a

[0131] 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.

[0132] Example 2b

[0133] 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.

[0134] Example 2c

[0135] 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.

[0136] Example 2d

[0137] 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.

[0138] Example 3 group

[0139] This set of examples is used to illustrate the effects of changing the weight ratio of fluoroethylene carbonate in the electrolyte.

[0140] Example 3a

[0141] 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.

[0142] Example 3b

[0143] 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.

[0144] Example 3c

[0145] 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.

[0146] Example 3d

[0147] 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.

[0148] Example 4 Group

[0149] This set of examples is used to illustrate the effects of changing the weight ratio of cyclic ethylene carbonate to fluoroethylene carbonate.

[0150] Example 4a

[0151] 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.

[0152] Example 4b

[0153] 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.

[0154] Example 4c

[0155] 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.

[0156] Example 4d

[0157] Example 1 was followed except that the weight percentage of fluoroethylene carbonate in the electrolyte was 33.6%, the weight percentage of cyclic ethylene carbonate in the electrolyte was 50%, the ratio of the weight of cyclic ethylene carbonate to the weight of fluoroethylene carbonate was 1.49, the weight percentage of LiPF6 in the electrolyte was 15%, the weight percentage of 1,3,6-hexanetricarbonitrile was 1.4%, and the electrolyte was free of propyl propionate and ethyl propionate.

[0158] Example 5 group

[0159] This group of examples is used to illustrate the effects that occur when d1 / d2 is changed.

[0160] Example 5a

[0161] Example 1 was followed except that d1 was 9.7 μm, d2 was 0.5 μm, and d1 / d2 = 9.7 / 0.5 = 19.4.

[0162] Example 5b

[0163] Example 1 was followed except that d1 was 5.2 μm, d2 was 4.9 μm, and d1 / d2 = 5.2 / 4.9 = 1.06.

[0164] Example 5c

[0165] Example 1 was followed except that d1 was 14.8 μm, d2 was 0.6 μm, and d1 / d2 = 14.8 / 0.6 = 24.67.

[0166] Example 5d

[0167] Example 1 was followed except that d1 was 3.1 μm, d2 was 2 μm, and d1 / d2 = 3.1 / 2 = 1.55.

[0168] Example 5e

[0169] Example 1 was followed except that d1 was 2.3 μm, d2 was 1.3 μm, and d1 / d2 = 2.3 / 1.3 = 1.77.

[0170] Example 5f

[0171] Example 1 was followed except that d1 was 2.3 μm, d2 was 2.7 μm, and d1 / d2 = 2.3 / 2.7 = 0.85.

[0172] Example 5g

[0173] Example 1 was followed except that d1 was 14.8 μm, d2 was 0.5 μm, and d1 / d2 = 14.8 / 0.5 = 29.6.

[0174] Example 5h

[0175] Example 5h was conducted as in Example 1 except that dl was 16.6 μm, d2 was 5.3 μm, and dl / d2 = 16.6 / 5.3 = 3.13.

[0176] Example 5i

[0177] Example 5i was conducted as in Example 1 except that dl was 1.8 μm, d2 was 0.4 μm, and dl / d2 = 1.8 / 0.4 = 4.5.

[0178] Example 6 Group

[0179] This group of examples is used to illustrate the effect when the composition of the first particles is changed.

[0180] Example 6a

[0181] Example 6a was conducted as in Example 1 except that the composition of the first particles was methyl methacrylate-ethylene copolymer.

[0182] Example 6b

[0183] Example 6b was conducted as in Example 1 except that the composition of the first particles was acrylate-acrylonitrile-ethylene copolymer.

[0184] Example 7 Group

[0185] This group of examples is used to illustrate the effect when the composition of the second particles is changed.

[0186] Example 7a

[0187] Example 7a was conducted as in Example 1 except that the composition of the second particles was PVDF.

[0188] Example 7b

[0189] Example 7b was conducted as in Example 1 except that the composition of the second particles was vinyl chloride-hexafluoroisobutene copolymer.

[0190] Example 8 Group

[0191] This group of examples is used to illustrate the effect when the specific selection of cyclic ethylene carbonate is changed.

[0192] Example 8a

[0193] Example 8a was conducted as in Example 1 except that the cyclic ethylene carbonate was all EC.

[0194] Example 8b

[0195] Example 1 was followed except that the cyclic carbonate was PC.

[0196] Example 9 group

[0197] Example 9a

[0198] Example 1 was followed except that the coverage of the coating on the surface of the support layer was 8%, the average particle diameter of the silicon-carbon composite particles was 5.1 μm, the graphitization degree of the silicon-carbon composite particles was 0.82, and the sphericity of the silicon-carbon composite particles was 0.95.

[0199] Example 9b

[0200] Example 1 was followed except that the coverage of the coating on the surface of the support layer was 70%, the average particle diameter of the silicon-carbon composite particles was 11.7 μm, the graphitization degree of the silicon-carbon composite particles was 0.46, and the sphericity of the silicon-carbon composite particles was 0.62.

[0201] Example 9c

[0202] Example 1 was followed except that the silicon-based material was silicon oxide particles, and the average particle diameter of the silicon oxide particles was 9 μm.

[0203] Example 10 group

[0204] This group of examples was used to show the effects when the composition of the third particles was changed.

[0205] Example 10a

[0206] Example 1 was followed except that the composition of the third particles was uracil.

[0207] Example 10b

[0208] Example 1 was followed except that the composition of the third particles was cytosine.

[0209] Example 10c

[0210] Example 1 was followed except that the composition of the third particles was melamine cyanurate.

[0211] Example 11

[0212] Example 1 was followed except that the second slurry was not used, and the first slurry was applied to the surface of the heat-resistant layer and the other surface of the base material layer, i.e., the coating on the surface of the heat-resistant layer was the same as the coating on the other surface of the base material layer.

[0213] Comparative Example 1

[0214] Example 1 was followed, except that the number of primary particles of the first particles having a particle size of less than or equal to 0.3 μm accounted for 0% of the number of primary particles of the first particles within an area of 100 μm x 100 μm of the surface of the coating.

[0215] Comparative Example 2

[0216] Example 1 was followed, except that the number of primary particles of the first particles having a particle size of less than or equal to 0.3 μm accounted for 4.2% of the number of primary particles of the first particles within an area of 100 μm x 100 μm of the surface of the coating.

[0217] Comparative Example 3

[0218] Example 1 was followed, except that the weight ratio of the cyclic carbonate ethylene carbonate to the fluorinated carbonate ethylene carbonate in the electrolyte was 0.4.

[0219] Comparative Example 4

[0220] Example 1 was followed, except that the weight ratio of the cyclic carbonate ethylene carbonate to the fluorinated carbonate ethylene carbonate in the electrolyte was 0.36.

[0221] Comparative Example 5

[0222] Example 1 was followed, except that the weight ratio of the cyclic carbonate ethylene carbonate to the fluorinated carbonate ethylene carbonate in the electrolyte was 0.18.

[0223] Comparative Example 6

[0224] Example 1 was followed, except that the weight ratio of the cyclic carbonate ethylene carbonate to the fluorinated carbonate ethylene carbonate in the electrolyte was 1.6.

[0225] Comparative Example 7

[0226] Example 1 was followed, except that the first particles were not present in the coating.

[0227] Test Example

[0228] The lithium ion batteries prepared from the examples and comparative examples were respectively subjected to the following tests:

[0229] 1. High temperature (60°C) cycle impedance change rate test

[0230] The lithium ion battery was transferred to a 60°C environment, and rested for 30 min. It was discharged at 0.2C constant current to 3.0V, rested for 5 min, then charged to 4.53V at 0.5C, and then charged to the cutoff current 0.05C at constant voltage, rested for 5 min, and the initial full-state impedance value R1 was tested using an electrochemical workstation. Then it was discharged at 0.7C constant current to 3.0V, and then cycled for 30T according to the following steps: 0.5C charging to 4.53V, then charging to the cutoff current 0.05C at constant voltage, resting for 5 min, and discharging at 0.7C constant current to 3.0V. After the cycle, 0.5C charging to 4.53V, then charging to the cutoff current 0.05C at constant voltage, resting for 5 min, and the post-cycle full-state impedance value R2 was tested using an electrochemical workstation. The impedance change rate was calculated as follows: [(R2-R1) / R1]x100%.

[0231] 2. Impedance change rate test at room temperature for long cycle

[0232] The lithium ion battery was transferred to a 25°C environment, and rested for 30 min. It was discharged at 0.2C constant current to 3.0V, rested for 5 min, then charged to 4.53V at 0.5C, and then charged to the cutoff current 0.05C at constant voltage, rested for 5 min, and the initial full-state impedance value R1 was tested using an electrochemical workstation. Then it was discharged at 0.7C constant current to 3.0V, and then cycled for 1000T according to the following steps: 0.5C charging to 4.53V, then charging to the cutoff current 0.05C at constant voltage, resting for 5 min, and discharging at 0.7C constant current to 3.0V. After the cycle, 0.5C charging to 4.53V, then charging to the cutoff current 0.05C at constant voltage, resting for 5 min, and the post-cycle full-state impedance value R2 was tested using an electrochemical workstation. The impedance change rate was calculated as follows: [(R2-R1) / R1]x100%.

[0233] 3. Capacity retention rate test at room temperature for long cycle

[0234] At 25°C±2°C, 0.7C constant current and constant voltage charging to the upper limit voltage 4.53V, with a cutoff of 0.05C, the initial thickness P0 was recorded, then 0.2C constant current discharging to the lower limit voltage 3.0V, and the initial discharge capacity was recorded as C0, and it was rested for 10 min. The cycle mode was as follows: 3C constant current and constant voltage charging to 4.25V, with a cutoff of 2C, then 2C constant current and constant voltage charging to 4.48V, with a cutoff of 1.5C, then 1.5C constant current and constant voltage charging to the upper limit voltage 4.53V, with a cutoff of 0.18C, and it was rested for 5 min, and then 0.7C discharging to the lower limit voltage 3.0V. After 1000T cycles, 0.7C constant current and constant voltage charging to the upper limit voltage 4.53V, with a cutoff of 0.05C, the final thickness P1 was recorded, and then 0.2C constant current discharging to the lower limit voltage 4.53V, and the final discharge capacity was recorded as C1. The capacity retention rate was C=C1 / C0*100%.

[0235] 4. High temperature cycle capacity retention test:

[0236] At 45℃, 0.7C constant current and constant voltage charging to the upper limit voltage 4.53V, cut-off 0.05C, record the initial thickness P0, then 0.2C constant current discharging to the lower limit voltage 3.0V, the initial discharge capacity is recorded as C0, static 10min, cycle mode: 3C constant current and constant voltage charging to 4.25V, cut-off 2C, turn 2C constant current and constant voltage charging to 4.48V, cut-off 1.5C, turn 1.5C constant current and constant voltage charging to the upper limit voltage 4.53V, cut-off 0.18C, static 5min, 0.7C discharging to the lower limit voltage 3.0V. After 300T cycles, 0.7C constant current and constant voltage charging to the upper limit voltage 4.53V, cut-off 0.05C, record the final thickness P1, then 0.2C constant current discharging to the lower limit voltage 4.53V, the final discharge capacity is recorded as C1. Capacity retention rate: C = C1 / C0*100%.

[0237] The results obtained are recorded in Table 1.

[0238] Table 1

[0239]

[0240]

[0241] As can be seen from Table 1, by comparing the comparative examples and the examples, the high temperature impedance change rate of the battery of the examples is significantly reduced, and the high temperature cycle capacity retention rate is significantly improved, which shows that by simultaneously controlling the weight ratio of the number of primary particles with a particle size less than or equal to 0.3μm in the first particles in the unit area of the coating surface, the weight ratio of the fluorinated ethylene carbonate in the electrolyte, and the weight ratio of the cyclic ethylene carbonate and the fluorinated ethylene carbonate, the high temperature cycle impedance of the battery is reduced, and the high temperature long cycle performance of the battery is improved.

[0242] The above describes the preferred embodiments of the present application in detail, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all fall within the protection scope of the present application.

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, 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; the first polymer is an acrylic polymer, and the cyclic carbonate includes ethylene carbonate and / or propylene carbonate.

2. The battery according to claim 1, wherein The coating further includes second particles, the components of the second particles include fluorine-containing polymers, 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.

3. The battery according to claim 2, wherein The coating further includes 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 includes second particles, and the mass proportion of the second particles in the coating is 20%-85%; And / or, the mass proportion of the first particles in the coating is 15%-80%; And / or, the Dv95 of the first particles is 0.5 μm-5 μm.

4. The battery according to claim 1, wherein The coating further comprises second particles, the components of the second particles include a fluorine-containing polymer, and the average particle size d1 of the secondary particles of the second particles is 2 μm-15 μm; And / or, the coating further includes second particles, the components of the second particles include fluorine-containing polymers, and the mass proportion of the second particles in the coating is 0%-90%.

5. The battery according to claim 1, wherein 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.

6. 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.

7. The battery according to claim 4, 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.

8. 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.

9. The battery according to claim 1, wherein 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. 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.

10. The battery according to claim 1, wherein: 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.

11. The battery according to any one of claims 1 to 10, 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%.

12. The battery according to any one of claims 1 to 10, wherein The weight proportion of the cyclic carbonate in the electrolyte is 5%-50%.

13. The battery according to any one of claims 1 to 10, wherein 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%).

14. The battery according to claim 9, 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.

15. The battery according to claim 13, 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%.

16. The battery according to claim 13, 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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