Battery

Abstract

The invention relates to the technical field of batteries, in particular to a battery. The battery comprises a negative plate, a positive plate, electrolyte and a diaphragm located between the positive plate and the negative plate, the negative plate comprises a negative current collector and a negative active layer located on the surface of one side or two sides of the negative current collector, and the negative active layer comprises amino; the diaphragm comprises a carrier layer and an adhesive layer located on the surface of one side or two sides of the carrier layer, the adhesive layer comprises first particles, the first particles are arranged in the adhesive layer in a stacked mode, the first particles are polymers containing ester groups, the first particles comprise primary particles, and the primary particles with the particle size smaller than 0.4 micrometer account for 1%-9% on the surface of the carrier layer; and the negative plate corresponds to one side, with the adhesive layer, of the diaphragm. According to the battery, the adhesion of an interface between the negative plate and the diaphragm can be improved, so that the long cycle performance and the safety performance of the battery are improved.

Description

Technical Field

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

[0002] In lithium-ion batteries, the interfacial adhesion between the negative electrode and the separator is one of the key factors ensuring the battery's long-cycle stability and safety performance. During battery cycle charging and discharging, poor adhesion between the separator and the negative electrode interface can lead to increased interfacial contact resistance, uneven lithium-ion transport, and relative displacement of the interface during cycling (especially when the negative electrode expands / contracts). This can result in lithium plating, capacity decay, increased internal resistance, and even the risk of thermal runaway, ultimately leading to poor long-cycle performance and safety of the battery. Summary of the Invention

[0003] To overcome the problem of poor interfacial adhesion between the negative electrode and the separator, which leads to poor long-cycle performance and safety, this invention provides a battery. The battery of this invention improves the interfacial adhesion between the negative electrode and the separator, thereby enhancing the battery's long-cycle performance and safety.

[0004] This invention provides a battery comprising a negative electrode, a positive electrode, an electrolyte, and a separator located between the positive and negative electrode. The negative electrode comprises a negative current collector and a negative active layer located on one or both surfaces of the negative current collector, the negative active layer comprising amino groups. The separator comprises a carrier layer and a binder layer located on one or both surfaces of the carrier layer. The binder layer comprises first particles arranged in a stacked manner within the binder layer. The first particles are composed of an ester-containing polymer and include primary particles. On the surface of the carrier layer, the proportion of primary particles with a particle size less than 0.4 μm is 1%-9%. The negative electrode corresponds to the side of the separator where the binder layer exists.

[0005] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: In the battery of this invention, an amino-based negative electrode active layer is adjacent to a gel layer comprising small-diameter ester-containing polymer particles. After the small-diameter ester-containing polymer particles swell in the electrolyte, the attractive interaction between the ester groups they contain and the amino groups in the negative electrode enhances the adhesion between the negative electrode and the separator, reduces the interfacial contact impedance between the separator and the negative electrode, and enables uniform lithium ion transport. Simultaneously, it reduces the risk of relative displacement between the separator and the negative electrode due to volume changes of the negative electrode active particles during battery cycling, lowering the risk of severe lithium plating and improving battery safety. Furthermore, the battery of this invention controls the proportion of primary particles with a diameter less than 0.4 μm on the surface of the carrier layer, ensuring both high adhesion and high permeability at the separator-negative electrode interface. This ensures interfacial stability while improving separator permeability, allowing lithium ions to freely transport along the thickness direction of the separator. It also ensures internal heat dissipation at high temperatures, further reducing the risk of thermal runaway.

[0006] Other features and advantages of the present invention will be described in detail in the following detailed description section.

[0007] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Attached Figure Description

[0008] Figure 1 The diagram shown is a schematic representation of the separator in the battery of the present invention. Detailed Implementation

[0009] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the invention. Unless otherwise specified herein, data ranges include endpoints.

[0010] It should be noted that the numerical designations such as "first" and "second" in this invention are only used to distinguish different substances or methods of use, and do not represent a difference in order.

[0011] This invention provides a battery comprising a negative electrode, a positive electrode, an electrolyte, and a separator located between the positive and negative electrode. The negative electrode comprises a negative current collector and a negative active layer located on one or both surfaces of the negative current collector, the negative active layer comprising amino groups. The separator comprises a carrier layer and a binder layer located on one or both surfaces of the carrier layer. The binder layer comprises first particles arranged in a stacked manner within the binder layer. The first particles are composed of an ester-containing polymer and include primary particles. On the surface of the carrier layer, the proportion of primary particles with a particle size less than 0.4 μm is 1%-9% (e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or 9%). The negative electrode corresponds to the side of the separator where the binder layer is present.

[0012] like Figure 1 As shown, the diaphragm 1 includes a carrier layer 11 and an adhesive layer 12 located on one or both surfaces of the carrier layer 11. The adhesive layer 12 includes first particles 121, which are arranged in a stacked manner within the adhesive layer 11. It is understood that a stacked arrangement means that, in the thickness direction of the diaphragm, the first particles are present in only one layer or multiple layers within the adhesive layer, and no large-diameter agglomerates are formed.

[0013] In this invention, a polymer containing ester groups refers to a polymer in which ester groups are present in its molecular structure.

[0014] In this invention, the term "primary particles" with a particle size less than 0.4 μm refers to primary particles whose individual particle size is less than 0.4 μm. The proportion of primary particles with a particle size less than 0.4 μm on the surface of the carrier layer can be determined by the following method: In a SEM image obtained by observing any position on the surface of the carrier layer at 5K magnification, the particle size of all primary particles of the first particle in the SEM image is measured. If there are fewer than 800 primary particles, multiple images are taken until there are 800 or more particles. Then, the total number of primary particles of the first particle in all the captured images is counted. 1 And the number of primary particles with a diameter less than 0.4 μm in all the photographs is X. 2 Then, on the surface of the carrier layer, the proportion of primary particles with a diameter less than 0.4 μm is (X... 2 / X 1The result is calculated as follows: (1) × 100%, repeat the above operation 3 times, and take the average of the 3 times as the test result. The particle size of the primary particle can be measured by the following method: In the SEM image of the carrier surface, draw the smallest square or rectangle that completely surrounds a primary particle, that is, draw the square or rectangle whose edge of the primary particle is connected to the four sides of the square or rectangle. The length of one side of the square or the length of the long side of the rectangle is the particle size of the primary particle.

[0015] In this invention, "the negative electrode sheet corresponds to the side of the separator where the adhesive layer exists" means that when the adhesive layer is located on one side of the carrier layer, the negative electrode sheet corresponds to the side of the separator where the adhesive layer exists, and the positive electrode sheet corresponds to the other side of the separator; when the adhesive layer is located on both sides of the carrier layer, the negative electrode sheet corresponds to one side of the separator where the adhesive layer exists, and the positive electrode sheet corresponds to the other side of the separator where the adhesive layer exists.

[0016] In the battery of the present invention, the negative electrode sheet corresponds to the side of the separator where the adhesive layer exists, that is, the negative electrode active layer is adjacent to the adhesive layer. The negative electrode active layer of the negative electrode sheet includes amino groups, and the adhesive layer of the separator corresponding to the negative electrode sheet includes first particles with small particle size composed of an ester-containing polymer. Under the swelling of the electrolyte, the ester groups in the ester-containing polymer can generate an attractive interaction with the amino groups in the negative electrode active layer. Specifically, the polarization of the carbonyl group and the electron-withdrawing effect of the oxygen atom make the carbon atom in the carbonyl group electron-deficient. The lone pair electrons on the nitrogen atom in the amino group can generate a certain force, thereby causing the ester group in the ester-containing polymer in the adhesive layer to have an attractive interaction with the amino group in the negative electrode active layer. This enhances the interfacial adhesion between the separator and the negative electrode, reduces the internal resistance of the battery, and reduces the risk of relative displacement at the interface. Especially after being immersed in the electrolyte, the separator and the negative electrode still have a high interfacial adhesion under the swelling of the electrolyte. This can improve the stability of the interface between the negative electrode and the separator, reduce the risk of increased internal resistance, and improve the long-cycle performance and thermal safety performance of the battery.

[0017] Controlling the proportion of primary particles with a diameter less than 0.4 μm on the surface of the carrier layer within the aforementioned range enables the interface between the separator and the negative electrode to possess both high adhesion and high permeability. Furthermore, it allows for better heat dissipation within the battery at high temperatures, reducing the risk of thermal runaway and thus resulting in both high long-cycle performance and high safety performance. Conversely, when the proportion of primary particles with a diameter less than 0.4 μm on the surface of the carrier layer is less than 1%, the insufficient number of these particles leads to low interfacial adhesion between the separator and the negative electrode, which is detrimental to improving the interfacial stability between them. When the proportion of primary particles with a particle size of less than 0.4 μm on the surface of the carrier layer is higher than 9%, the excessive number of primary particles with a particle size of less than 0.4 μm leads to excessive swelling of the primary particles, which can easily block the pores of the separator, thereby reducing the permeability of the separator and hindering the permeability of lithium ions in the thickness direction of the separator. At the same time, it can also lead to an excessively small interface gap between the separator and the negative electrode, which is not conducive to heat dissipation inside the battery at high temperatures, thus increasing the risk of thermal runaway in the battery.

[0018] In this invention, by incorporating an ester-containing polymer into the separator's adhesive layer, adding amino groups to the negative electrode active layer, and controlling the proportion of primary particles with a particle size less than 0.4 μm on the surface of the carrier layer, the interfacial stability between the negative electrode and the separator can be improved compared to existing technologies, thereby enhancing the battery's long-cycle performance and safety. To further improve the effect, one or more of these technical features can be further optimized.

[0019] In some instances, the ester-containing polymer exhibits a mass swelling degree greater than or equal to 5% in a standard electrolyte. The standard electrolyte comprises lithium hexafluorophosphate, ethylene carbonate, methyl ethyl carbonate, and dimethyl carbonate, with a lithium hexafluorophosphate concentration of 1 mol / L and a volume ratio of ethylene carbonate, methyl ethyl carbonate, and dimethyl carbonate of 1:1:1.

[0020] In some instances, the ester-containing polymer is an acrylate polymer.

[0021] In some examples, the ester-containing polymers include one or more of polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, acrylate-acrylonitrile copolymer, acrylate-acrylonitrile-ethylene copolymer, styrene-acrylate-acrylonitrile copolymer, ethylhexyl acrylate-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, methyl acrylate-acrylic acid-N,N-dimethylacrylamide copolymer, ethyl acrylate-ethyl acrylate-2-(diethylamino)acrylate copolymer, ethyl acrylate-acrylic acid-N,N-diethylacrylamide copolymer, and ethyl acrylate-2-(diethylamino)acrylate.

[0022] In some instances, the acrylates in acrylate-acrylonitrile copolymers, acrylate-acrylonitrile-ethylene copolymers, and styrene-acrylate-acrylonitrile copolymers include one or more of methyl methacrylate, butyl acrylate, n-propyl acrylate, octyl acrylate, ethyl methacrylate, isooctyl acrylate, octadecyl acrylate, ethyl acrylate, methyl acrylate, isobutyl acrylate, cyclohexyl acrylate, and 2-hydroxyethyl acrylate.

[0023] In some instances, the monomers forming the ester-containing 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.

[0024] In some instances, the ester-containing polymer includes ester groups, and the weight percentage of the ester groups in the ester-containing polymer is 10%-60% (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60%).

[0025] In some instances, the glass transition temperature of the ester-containing polymer is 40°C-75°C (e.g., 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, or 75°C).

[0026] In some instances, the average particle size of the first particle is 0.5 μm-0.95 μm (0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, or 0.95 μm). The average particle size of the first particle can be obtained by observing a SEM scan image of any position on the surface of the carrier layer at 5K magnification, measuring the particle size of all primary particles of the first particle in the SEM image. If there are fewer than 800 primary particles, multiple images are taken until there are 800 particles, and the particle size of all 800 first particles is obtained. The average particle size of the first particle = the sum of the particle sizes of all first particles / 800.

[0027] In some instances, the adhesive layer comprises a first particle and a second particle, wherein the second particle is composed of a fluoropolymer.

[0028] In some instances, the fluoropolymer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, fluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer.

[0029] In some instances, the monomers forming the fluoropolymer include one or more of vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, and hexafluoropropylene.

[0030] In some instances, the adhesive layer comprises polymer particles, wherein the polymer particles in the adhesive layer are first particles.

[0031] In some instances, the adhesive layer comprises polymer particles, wherein the polymer particles in the adhesive layer are first particles and second particles, and the weight ratio of the first particles to the second particles is (5%-50%):(95%-50%). It is understood that the weight percentage of the first particles in the polymer particles can be between 5% and 50% (e.g., 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%), and the weight percentage of the second particles can be between 95% and 50% (e.g., 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, or 50%). However, it should be noted that the sum of the weight percentages of the first particles and the second particles in the polymer particles is 100%.

[0032] In some instances, the thickness of the adhesive layer is 0.5 μm to 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).

[0033] In some instances, the adhesive layer is located on both sides of the carrier layer, and the adhesive layer includes a first adhesive layer and a second adhesive layer, wherein the polymer particles in the first particle are first particles, and the polymer particles in the second adhesive layer are first particles. It is understood that one or more of the following—the thickness of the first adhesive layer and the second adhesive layer, the composition of the first particle, and the particle size of the first particle—may be the same or different.

[0034] In some instances, the adhesive layer is located on both sides of the carrier layer, and the adhesive layer includes a first adhesive layer and a second adhesive layer. The polymer in the first particle consists of both the first particle and the second particle, and the polymer particles in the second adhesive layer consist of both the first particle and the second particle. It is understood that one or more of the following parameters may be the same or different: the thickness of the first adhesive layer and the second adhesive layer, the weight percentage of each component, the composition of the first particle, the particle size of the first particle, the composition of the second particle, and the particle size of the second particle.

[0035] In some examples, the adhesive layer is located on both sides of the carrier layer. The adhesive layer includes a first adhesive layer and a second adhesive layer. The polymer particles in the first adhesive layer are first particles, and the polymer particles in the second adhesive layer are both first particles and second particles. The first adhesive layer corresponds to the positive electrode sheet, and the second adhesive layer corresponds to the negative electrode sheet. It is understood that one or more of the following: the thickness of the first adhesive layer and the second adhesive layer, the composition of the first particles, and the particle size of the first particles may be the same or different.

[0036] In some examples, the adhesive layer is located on both sides of the carrier layer. The adhesive layer includes a first adhesive layer and a second adhesive layer. The polymer particles in the first adhesive layer are first particles, and the polymer particles in the second adhesive layer are both first particles and second particles. The first adhesive layer corresponds to the negative electrode sheet, and the second adhesive layer corresponds to the positive electrode sheet. It is understood that one or more of the following—the thickness of the first adhesive layer and the second adhesive layer, the composition of the first particles, and the particle size of the first particles—may be the same or different.

[0037] In some instances, the carrier layer includes a substrate layer and a coating located on one or both surfaces of the substrate layer, the coating comprising heat-resistant particles.

[0038] In some instances, the Dv50 of the heat-resistant particles is 0.2 μm-2 μm (e.g., 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, or 2 μm). In this invention, the Dv50 of the heat-resistant particles is the particle size corresponding to 50% of the cumulative particle size distribution in the volumetric particle size distribution of the heat-resistant particles. In this invention, the volumetric particle size distribution of the heat-resistant particles can be obtained by testing with a laser particle size analyzer.

[0039] In some instances, the heat-resistant particles include a third particle, the third particle being composed of an amino-containing organic compound. The amino-containing organic compound refers to an organic compound containing an amino group (-NH2) in its structure, or a small molecule containing an amino group (-NH2) that can be tracely dissolved and dissociated in the electrolyte.

[0040] In silicon-based batteries, the dramatic expansion of silicon particles exacerbates poor adhesion at the interface between the negative electrode and the separator during battery cycling. In the battery of this invention, the separator coating includes a third particle composed of an amino-containing organic compound. The amino group acts as a strong hydrogen bond donor, while hydrogen bond acceptors such as carbonyl, hydroxyl, and ether bonds are typically present on the surface of the silicon particles in the negative electrode active layer. The amino-containing organic compound can provide multiple highly active amino sites. These sites combine with the hydrogen bond acceptors on the surface of the silicon-based material in the negative electrode active layer, forming a stable three-dimensional dynamic hydrogen bond cross-linking network at the separator-negative electrode interface. This further reduces the risk of relative displacement at the interface between the separator and the negative electrode during cycling (especially during negative electrode expansion / contraction), reduces the risk of severe lithium plating, lowers the battery's capacity, and further improves the battery's long-cycle stability and safety performance. Furthermore, the amino groups in the third particle are similarly miscible with the amino groups in the negative electrode active layer, further reducing the interfacial resistance between the separator and the negative electrode.

[0041] In some instances, the amino-containing organic compound includes one or more of melamine polyphosphate, melamine thiocyanate, melamine cyanurate, piperazine pyrophosphate, 4-amino-2,6-dihydroxypyrimidine, 6-aminopurine, and melamine polyphosphate.

[0042] In some instances, the heat-resistant particles further include a fourth particle, which includes one or more of alumina particles, silica particles, boehmite, magnesium oxide particles, boron nitride particles, and magnesium hydroxide particles.

[0043] In some instances, the heat-resistant particles include a third and a fourth particle.

[0044] In some instances, the weight ratio of the third particle to the fourth particle is (5%-95%):(95%-5%). It is understood that the weight percentage of the third particle in the heat-resistant granules can range from 5% to 95% (e.g., 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%), and the weight percentage of the fourth particle in the heat-resistant granules can range from 95% to 5% (e.g., 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, or 5%). However, it should be noted that the sum of the weight percentages of the third and fourth particles in the heat-resistant granules must satisfy 100%.

[0045] In some instances, the coating further includes a first adhesive comprising one or more of the following: methacrylic acid, sodium polymethyl cellulose, polyvinyl alcohol, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polymethyl methacrylate, polybutyl methacrylate, styrene-acrylic latex, polyacrylonitrile, ethyl polyacrylate, polyvinyl acetate, polyacrylate, polyvinylidene fluoride polyurethane, polyvinylidene fluoride-hexafluoropropylene, or copolymers derived from the above polymers.

[0046] In some instances, the heat-resistant particles in the coating comprise 90%-99% by weight (e.g., 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%), and the first binder comprises 1%-10% by weight (e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%).

[0047] In some instances, the coating thickness is 0.2 μm to 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).

[0048] According to some specific embodiments, the carrier layer includes a substrate layer and a coating located on one side surface of the substrate layer, the coating including heat-resistant particles and a first binder, wherein the heat-resistant particles are third particles.

[0049] According to some specific embodiments, the carrier layer includes a substrate layer and a coating located on one side surface of the substrate layer, the coating including heat-resistant particles and a first binder, the heat-resistant particles being composed of a third particle and a fourth particle.

[0050] According to some specific embodiments, the carrier layer includes a substrate layer and coatings located on both sides of the substrate layer. The coatings include heat-resistant particles and a first binder, wherein the heat-resistant particles are third particles. It is understood that one or more of the following—the thickness of the coatings located on both sides of the substrate layer, the weight percentage of each component, the composition of the third particles, and the particle size of the heat-resistant particles—may be the same or different.

[0051] According to some specific embodiments, the carrier layer includes a substrate layer and coatings located on both sides of the substrate layer. The coatings include heat-resistant particles and a first binder, and the heat-resistant particles are composed of third and fourth particles. It is understood that one or more of the following—the thickness of the coating on both sides of the substrate layer, the weight percentage of each component, the composition of the third particle, the composition of the fourth particle, the weight ratio of the third particle to the fourth particle, and the particle size of the heat-resistant particles—may be the same or different.

[0052] According to some specific embodiments, the carrier layer includes a substrate layer and coatings located on both sides of the substrate layer. The coatings include heat-resistant particles and a first binder. The heat-resistant particles on one side of the substrate layer are third particles, and the heat-resistant particles on the other side of the substrate layer consist of a third particle and a fourth particle. It is understood that one or more of the following—the thickness of the coatings on both sides of the substrate layer, the weight percentage of each component, the composition of the third particle, and the particle size of the heat-resistant particles—may be the same or different.

[0053] In some instances, the substrate layer comprises one or more of the following polymer derivatives: polyolefin, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), or poly(m-phenylene isophthalamide).

[0054] In some instances, the thickness of the substrate layer is 2μm-10μm (e.g., 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm or 10μm).

[0055] In some instances, the porosity of the substrate layer is 25%-70% (e.g., 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%).

[0056] In some instances, the negative electrode active layer includes a negative electrode binder, which comprises an aqueous polyurethane. The aqueous polyurethane includes amino groups, and the amino groups in the negative electrode active layer are derived from the aqueous polyurethane.

[0057] In some instances, the weight percentage A of the aqueous polyurethane in the negative electrode active layer is 0.6%-6% (e.g., 0.6%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, or 6%). The weight percentage of the aqueous polyurethane in the negative electrode active layer refers to the ratio of the weight of the aqueous polyurethane in a single negative electrode active layer to the total weight of the negative electrode active layer. For example, when the negative electrode active layer is a single layer, the weight percentage of the aqueous polyurethane in the negative electrode active layer refers to the proportion of the aqueous polyurethane in that single negative electrode active layer to the total weight of the negative electrode active layer; when the negative electrode active layer is two or more layers (>2), the weight percentage of the aqueous polyurethane in the negative electrode active layer refers to the proportion of the total weight of the aqueous polyurethane in the two or more negative electrode active layers to the total weight of the two or more negative electrode active layers.

[0058] In some instances, the molecular chain of the waterborne polyurethane comprises soft segments and hard segments, the structure of which includes a 1 -OR 1 -Oa 1 R 1 The alkyl group is a chain-like alkyl group, consisting of a main chain and optionally branched chains, wherein the main chain is selected from C3-C200 alkyl groups, and the branched chains are selected from C1-C40 alkyl groups. The structure of the rigid segment includes... R 2 The aliphatic ring is either substituted or unsubstituted, with the number of carbon atoms n ranging from 5 to 20. 1 Selected from , , where a 1 a is the connection site between hard and soft chain segments. 2 For T 1 With R 2 The connection site of the fatty ring.

[0059] Structure a of the soft chain segment 1 -OR 1 -Oa 1 In the middle, oxygen atoms and R 1 In a chain alkyl group, different carbon atoms are linked together, and the number of carbon atoms in the chain alkyl group located between two oxygen atoms is greater than or equal to 3.

[0060] In some instances, the main chain is selected from C3-C20 alkyl groups, such as n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, neopentyl, 2,2-dimethylpropyl, 1-ethylpropyl, 1-methylbutyl, 2-methylbutyl, n-hexyl, isohexyl, 2-hexyl, 3-hexyl, 2-methylpentyl, 3-methylpentyl, 1,1,2-trimethylpropyl, 3,3-dimethylbutyl, n-heptyl, 2-heptyl, 3-heptyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, isoheptyl, n-octyl, nonyl, decyl, undecylyl, dodecylyl, tridecylyl, tetradecylyl, pentadecylyl, hexadecylyl, heptadecanyl, octadecylyl, nonadecanyl, and eicosyl.

[0061] In some instances, the branched chain is selected from C1-C10 alkyl groups, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, neopentyl, 2,2-dimethylpropyl, 1-ethylpropyl, 1-methylbutyl, 2-methylbutyl, n-hexyl, isohexyl, 2-hexyl, 3-hexyl, 2-methylpentyl, 3-methylpentyl, 1,1,2-trimethylpropyl, 3,3-dimethylbutyl, n-heptyl, 2-heptyl, 3-heptyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, isoheptyl, n-octyl, nonyl, decyl.

[0062] R 2 A substituent or unsubstituent aliphatic ring refers to a ring in which one or more hydrogen atoms can be substituted by substituents, or even all hydrogen atoms can be substituted by substituents, or any hydrogen atom in the aliphatic ring can be left unsubstituent. The substituents can be selected from C1-C3 alkyl groups, such as methyl, ethyl, n-propyl, and isopropyl.

[0063] R 2 It can be selected from cyclopentyl, Cyclohexyl, phenyl , , , .

[0064] The structure of the rigid chain segment In, with R 2 The nitrogen atom in the adjacent NH and T 1 middle carbon atoms and The oxygen atoms in all of them are related to R 2 The carbon atoms on the aliphatic ring are connected.

[0065] In some instances, the weight ratio of the flexible chain segment to the weight of the flexible chain segment is (1-6):1 (e.g., 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5 or 1:6).

[0066] In some examples, the waterborne polyurethane is prepared by polymerization of hard-segment monomers and soft-segment monomers. The hard-segment monomers include at least one selected from 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, norbornene diisocyanate, adamantane diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated toluene diisocyanate, hexamethylene diisocyanate, and toluene diisocyanate. The soft-segment monomers include at least one selected from 2-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, dihydroxy-terminated polyethylene, and dihydroxy-terminated hydrogenated polybutadiene. The hard-segment monomers can form hard segments in the waterborne polyurethane, and the soft-segment monomers can form soft segments in the waterborne polyurethane.

[0067] In some instances, the negative electrode active layer comprises a negative electrode active material, which is a silicon-based material. The silicon-based material is granular.

[0068] In some instances, the negative electrode active layer comprises a silicon-based material and an aqueous polyurethane. The silicon-based material expands dramatically during lithium-ionization (charging) and contracts during lithium-delithiation (discharging). This repeated "breathing" action generates significant mechanical stress on the negative electrode structure. The aqueous polyurethane molecular chain comprises soft segments (also known as "soft segments," such as polyether segments and polyester segments) and hard segments (also known as "hard segments," such as urethane groups and urea groups). This unique microphase separation structure endows the aqueous polyurethane with extremely high elasticity and flexibility. When the silicon-based material expands, the flexible segments of the aqueous polyurethane can stretch like a spring, absorbing enormous strain energy. When the silicon-based material contracts, the elastic segments can return to their original shape, thus providing an elastic buffer against the expansion and contraction of the silicon-based material. This "elastic buffer" effectively alleviates the volume change stress of the silicon-based material, reducing the risk of the negative electrode active layer detaching from the negative electrode current collector and / or the risk of overall structural collapse of the negative electrode, thereby further improving the battery's long-cycle performance and safety.

[0069] In some instances, the separator includes a substrate layer, a coating layer, and an adhesive layer, with one side surface of the substrate layer including the coating layer and the adhesive layer, and the negative electrode corresponding to the side of the substrate layer that includes the coating layer and the adhesive layer.

[0070] In some instances, the battery satisfies the following relationship: 0.06 ≤ S × A / E ≤ 24 (e.g., 0.06, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24), where S is the Dv50 of the silicon-based material in μm, A is the weight percentage of the aqueous polyurethane in the negative electrode active layer, and E is the coverage of the adhesive layer on the carrier layer surface on the side corresponding to the negative electrode sheet.

[0071] In batteries containing silicon-based materials, not only does the volume change of the silicon-based material exacerbate the problem of poor interfacial adhesion between the negative electrode and the separator, but the diffusion coefficient of lithium ions in crystalline silicon is generally lower than that in graphite layers; although silicon transforms into amorphous Li during lithiation... x Si (whose ion diffusion coefficient is higher than that of crystalline silicon), but its average diffusion rate is usually not as fast as that in graphite. Therefore, the migration rate of lithium ions inside silicon-based materials is slower, resulting in poor kinetic performance of batteries containing silicon-based materials, which is not conducive to improving the long-cycle performance of batteries containing silicon-based materials.

[0072] The separator of the present invention includes a coating and an adhesive layer. The adhesive layer comprises an ester-containing polymer. The ester groups in the ester-containing polymer can interact attractively with the amino groups (provided by aqueous polyurethane) in the negative electrode active layer, thereby improving the interfacial adhesion between the negative electrode and the separator. Simultaneously, the amino groups in the amino-containing organic compound in the coating, acting as hydrogen bond donors, can form strong hydrogen bond bridges between the separator and the negative electrode with hydrogen bond acceptors such as carbonyl, hydroxyl, and ether bonds present on the surface of the silicon-based material in the negative electrode active layer, further improving the interfacial adhesion between the negative electrode and the separator. However, the adhesive layer is located on the surface of the coating, and the adhesive layer on the side corresponding to the negative electrode is controlled to be on the surface of the carrier layer. The surface coverage E allows the separator surface to simultaneously expose first particles composed of ester-containing polymers and third particles composed of amino-containing organic compounds. Through the attractive interaction between the ester groups in the separator and the amino groups in the negative electrode active layer, and the strong hydrogen bonds formed by the amino groups in the separator and the hydrogen bond acceptors on the silicon-based material surface, the interfacial adhesion between the negative electrode and the separator can be further improved while ensuring separator permeability. Simultaneously, the highly elastic and flexible structure of the aqueous polyurethane in the negative electrode active layer can buffer the volume stress of the silicon-based material during cyclic charging and discharging, reducing the adverse effects of volume changes in the silicon-based material on the interface between the negative electrode and the separator. Furthermore, controlling the Dv50 of the silicon-based material can improve its kinetic performance, which is beneficial for enhancing the long-cycle performance of the battery.

[0073] Therefore, by controlling the battery to satisfy the following relationship: 0.09≤S×A / E≤22, a better matching degree can be formed between the first particles of the ester-containing polymer in the separator, the third particles of the amino-containing organic matter, and the aqueous polyurethane and silicon-based materials in the negative electrode active layer. Through the synergistic cooperation among the first particles, the third particles, the aqueous polyurethane, and the silicon-based materials, the adverse effects of the volume change of the silicon-based materials on the interface between the negative electrode and the separator are reduced, while the stability of the interface between the negative electrode and the separator and the kinetic performance of the silicon-based materials are further improved, thereby further improving the long-cycle performance and safety of the battery.

[0074] When S×A / E is less than 0.09, the adhesive layer on the side corresponding to the negative electrode sheet has a large coverage on the surface of the carrier layer, and the amount of exposed third particles is small. This is not conducive to the formation of more strong hydrogen bonds between the amino-containing organic matter and the hydrogen bond acceptors on the surface of the silicon-based material. It is not conducive to further improving the adhesion between the negative electrode sheet and the separator without affecting the gas permeability of the separator. Alternatively, the weight ratio of the aqueous polyurethane in the negative electrode active layer is too small, and the amount of amino groups in the negative electrode active layer is too small. This is not conducive to the formation of more attractive effects between the ester-containing polymer and the amino groups. At the same time, it is not conducive to the aqueous polyurethane providing sufficient buffer for the volume change of the silicon-based material. This is not conducive to further improving the adhesion between the negative electrode sheet and the separator. Alternatively, the Dv50 of the silicon-based material is too small, and the reactivity of the silicon-based material is too high, which can easily trigger thermal runaway and affect the thermal safety performance of the battery. When S×A / E is higher than 22, the coverage of the adhesive layer on the corresponding side of the negative electrode sheet on the surface of the carrier layer is too small, which is not conducive to the storage of electrolyte and affects the long cycle performance of the battery. Alternatively, the weight ratio of the aqueous polyurethane in the negative electrode active layer is too large, which increases the impedance of the negative electrode active layer and affects the long cycle performance of the battery. Or, the Dv50 of the silicon-based material is too large, and the expansion of the silicon-based material is too large, which is not conducive to further improving the adhesion between the negative electrode sheet and the separator.

[0075] In some instances, the coverage E of the adhesive layer on the surface of the carrier layer on the side corresponding to the negative electrode is 5%-50% (e.g., 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%). In this invention, the coverage of the adhesive layer on the surface of the carrier layer can be tested by obtaining a microscopic image of the carrier layer surface using SEM, and randomly dividing the image into areas with a size of 10000µm. 2 Divide the area (e.g., 100µm × 100µm) into uniform 200×200 squares. If the area covered by the orthographic projection of the coating in a square exceeds half the square's area, then the square is considered to be occupied by the coating; otherwise, the square is not occupied by the coating. Record the total number of squares occupied by the coating as X. 3Then coverage = (X 3 (200×200)×100%, repeat the above operation 5 times, and take the average value of the 5 times as the coverage rate of the coating on the surface of the carrier layer.

[0076] In some examples, the Dv50 of the silicon-based material is 5μm-20μm (e.g., 5μm, 8μm, 10μm, 13μm, 15μm, 18μm, or 20μm). In this invention, Dv50 is the particle size corresponding to 50% of the cumulative particle size distribution in the volumetric particle size distribution of the silicon-based material. In this invention, the volumetric particle size distribution of the silicon-based material can be obtained by measuring and statistically processing the Dv50 in SEM images of the surface of the negative electrode active layer using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.). The Dv50 of the silicon-based material can also be obtained by testing with a laser particle size analyzer; for example, the Dv50 of the silicon-based material can be measured using a laser particle size analyzer before the negative electrode sheet is prepared.

[0077] In some instances, the silicon-based material includes one or more of elemental silicon, silicon nitride materials, silicon alloys, silicon oxide materials, and silicon carbon materials.

[0078] In some instances, the silicon-carbon material comprises porous carbon and silicon particles, the silicon particles being at least partially filled in the pores of the porous carbon.

[0079] According to some specific implementation methods, A is 0.6%-6%, E is 5%-50%, S is 5-20, and the battery satisfies the following relationship: 0.09≤S×A / E≤22.

[0080] In some examples, the surface of the negative electrode active layer away from the negative electrode current collector is a first surface, and the first surface includes a plurality of recesses. Providing recesses on the first surface can increase the lithium-ion transport channels, improve lithium-ion transport efficiency, and enhance the battery's rate performance and long-cycle performance.

[0081] In some instances, the recess includes one or more of a hole, a line, and a groove.

[0082] In some instances, the sum of the areas of the orthographic projections of the recesses onto the first surface constitutes 3%-50% of the total area of ​​the first surface (e.g., 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%). It is understood that when the surfaces of the negative electrode active layers on both sides of the negative electrode current collector include several recesses, the sum of the areas of the orthographic projections of the recesses on both sides onto the first surface may have the same or different proportions. In this invention, the proportion of the sum of the areas of the orthographic projections of the recesses onto the first surface can be measured using SEM combined with image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.).

[0083] By controlling the sum of the areas of the orthogonal projections of the recesses onto the first surface to be within the aforementioned range, the wettability of the electrolyte to the negative electrode sheet and the swelling of the adhesive layer on the side corresponding to the negative electrode sheet in the electrolyte can be improved. This makes it easier for the ester groups in the ester-containing polymer to generate attractive interactions with the amino groups in the negative electrode active layer, further improving the stability of the interface between the separator and the negative electrode sheet. At the same time, it can also improve the lithium-ion transport efficiency of the battery with a small loss of energy density, reduce the risk of severe lithium plating, and enable the battery to have both high rate performance and long cycle performance. When the sum of the areas of the orthogonal projections of the recesses on the first surface accounts for less than 3% of the total area of ​​the first surface, it is not conducive to increasing the swelling of the electrolyte layer, nor to further improving the stability of the interface between the separator and the negative electrode. In addition, the lithium-ion transport kinetics are low, which is not conducive to improving severe lithium plating. When the sum of the areas of the orthogonal projections of the recesses on the first surface accounts for more than 50% of the total area of ​​the first surface, the energy density loss is too large. Furthermore, the adhesion between the separator and the negative electrode that is improved by promoting the swelling of the adhesive layer is insufficient to compensate for the reduced adhesion caused by the reduced contact area between the negative electrode and the separator due to the recesses. This will affect the adhesion between the separator and the negative electrode.

[0084] In some instances, the negative electrode active layer comprises a carbon-based material, a negative electrode conductive agent, and a negative electrode binder.

[0085] In some instances, the carbon-based material includes synthetic graphite and / or natural graphite.

[0086] In some instances, the negative electrode conductive agent includes one or more of acetylene black, carbon black, Super P, Ketjen black, carbon nanotubes, graphene, and carbon fiber.

[0087] In some instances, the negative electrode binder includes one or more of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, polyethylene oxide, and polyvinylidene fluoride.

[0088] In some instances, based on the total weight of the negative electrode active layer, the silicon-based material accounts for 3%-95% of the weight (e.g., 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%), and the carbon-based material accounts for 3%-95% of the weight (e.g., 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%). The negative electrode conductive agent has a weight percentage of 0.05%-3% (e.g., 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5% or 3%), and the negative electrode binder has a weight percentage of 0.5%-10% (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%).

[0089] In some examples, the negative electrode active layer includes a first active layer and a second active layer. The first active layer is located between the negative electrode current collector and the second active layer, and the weight percentage of the aqueous polyurethane in the first active layer is greater than that in the second active layer. Controlling the weight percentage of the aqueous polyurethane in the first active layer to be greater than that in the second active layer can improve the overall kinetic performance of the negative electrode sheet and reduce the risk of severe lithium plating. Specifically, the first active layer is located between the negative electrode current collector and the second active layer. A relatively large weight percentage of aqueous polyurethane in the first active layer can improve the adhesion between the first active layer and the negative electrode current collector, reducing the risk of the negative electrode active layer detaching from the negative electrode current collector. Simultaneously, the high weight percentage of aqueous polyurethane in the first active layer ensures a high adhesion between the first active layer and the negative electrode current collector, thus reducing the risk of the second active layer detaching. Therefore, reducing the weight percentage of aqueous polyurethane in the second active layer, even if it is relatively small, can improve the kinetic performance of the negative electrode sheet, thereby reducing the risk of severe lithium plating.

[0090] In some instances, the waterborne polyurethane in the first active layer comprises 0.5%-10% by weight (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%).

[0091] In some instances, the waterborne polyurethane in the second active layer comprises 0.5%-8% by weight (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7% or 8%).

[0092] According to some specific implementation methods, the weight percentage of the waterborne polyurethane in the first active layer is greater than the weight percentage of the waterborne polyurethane in the second active layer. The weight percentage of the waterborne polyurethane in the first active layer is 0.5%-10%, and the weight percentage of the waterborne polyurethane in the second active layer is 0.5%-8%.

[0093] In some instances, the electrolyte comprises cyclic carbonates, which include ethylene carbonate and / or propylene carbonate.

[0094] In some instances, the weight percentage of the cyclic carbonate in the electrolyte is 3%-50% (e.g., 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%). Controlling the weight percentage of the cyclic carbonate in the electrolyte within this range allows for the swelling of the first particles by the electrolyte, promoting an attractive interaction between the ester groups in the ester-containing polymer and the amino groups in the negative electrode active layer. Simultaneously, it ensures that the swelling of the first particles by the electrolyte is not excessive, avoiding the risk of pore blockage due to excessive swelling of the first particles, which could reduce the permeability of the membrane.

[0095] In some instances, the cyclic carbonate in the electrolyte comprises 5%-25% by weight.

[0096] In some instances, the electrolyte includes lithium salts, organic solvents, and additives.

[0097] In some instances, the lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium difluorooxalate borate, lithium dioxalate borate, and lithium tetrafluorooxalate phosphate.

[0098] In some instances, the organic solvent includes one or more of the following, excluding cyclic carbonates: 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.

[0099] In some instances, the additives include one or more of fluorocyclic carbonates, dinitrile compounds, trinitrile compounds, fluorochain carbonates, and sulfur-containing oxygen double bond compounds.

[0100] In some instances, based on the total weight of the electrolyte, the lithium salt accounts for 8%-20% by weight (e.g., 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%), the organic solvent accounts for 50%-80% by weight (e.g., 50%, 55%, 60%, 65%, 70%, 75%, or 80%), and the additives account for 0%-30% by weight (e.g., 0%, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, or 30%). When the weight percentage of the additives in the electrolyte is 0%, it indicates that the additives are not present in the electrolyte.

[0101] In some examples, the positive electrode sheet includes a positive current collector and a positive active layer located on at least one side of the surface of the positive current collector. The positive active layer is not particularly limited and can include components such as a positive active material, a positive conductive agent, and a positive binder, according to conventional compositions in the art. The positive active material, positive conductive agent, and positive binder can all be conventional materials in the art. For example, the positive active material may include one or more of lithium nickel oxide, lithium titanate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide; the positive conductive agent may include one or more of conductive carbon black, carbon nanotubes, conductive graphite, and graphene; and the positive binder may include one or more of polyvinylidene fluoride (PVDF), acrylic acid-modified PVDF, polyacrylate polymers, acrylic polymers, polytetrafluoroethylene, polyacrylonitrile, polyimide, styrene-butadiene rubber, and styrene-acrylic rubber.

[0102] In some instances, the battery has a charging cutoff voltage greater than or equal to 4.5V (e.g., 4.5V, 4.53V, 4.55V, 4.58V, or 4.6V).

[0103] In some instances, the battery is a lithium-ion rechargeable battery.

[0104] The present invention will be described in detail below through embodiments. The embodiments described herein are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0105] The following examples illustrate the battery of the present invention.

[0106] Example 1 (1) Diaphragm The heat-resistant granules (third granules, melamine cyanurate (MAC), with a Dv50 of 0.3 μm), methacrylic acid, and sodium polymethyl cellulose were added to deionized water and stirred thoroughly to obtain a coating slurry with a solid content of 15%. Based on 100% solids mass of the slurry, the weight ratio of MAC:methacrylic acid:sodium polymethyl cellulose was 92:4:4. The coating slurry was applied to one side of the substrate layer (polyethylene) using a gravure roller and dried in a multi-section oven at 60°C to form a coating. The first granules (PMMA, with an average particle size of 0.6 μm) were then added. A (44% by weight of ester groups in component A) is dispersed in a deionized water solvent and thoroughly stirred to obtain a first adhesive slurry with a solid content of 10%. This slurry is then applied to the surface of the substrate layer using a gravure roller and dried in a multi-section oven at 60°C to form the first adhesive layer. The first particles (PMMA, average particle size 0.6 μm) and the second particles (PVDF) are dispersed in a deionized water solvent and thoroughly stirred to obtain a second adhesive slurry with a solid content of 10%. This second adhesive slurry is then applied to the surface of the coating layer using a gravure roller and dried in a multi-section oven at 60°C to form the second adhesive layer. The weight ratio of the first particles to the second particles is 25%:75%. On the surface of the carrier layer (substrate layer), the proportion of primary particles with a particle size less than 0.4 μm is 5.2%. The coverage of the first adhesive layer on the substrate layer surface is 15%, and the coverage of the second adhesive layer on the coating surface is 15%, i.e., E% is 15%.

[0107] (2) Negative electrode plate Artificial graphite, silicon carbon material (Dv50 of 9 μm, i.e., S = 9), waterborne polyurethane (hard segment monomer is toluene diisocyanate, soft segment monomer is 2-methyl-1,5-pentanediol), binder, carbon nanotubes, and lithium carboxymethyl cellulose were dissolved in deionized water in a weight ratio of 87.03:9.67:2:0.6:0.7 to form a negative electrode slurry. The negative electrode slurry was coated on both sides of a copper foil with a coating weight of 3.5 mg / cm³. 2 After drying, cold pressing, and slitting, the negative electrode sheet is obtained. Both sides of the negative electrode active layer have recesses on their first surfaces, and the sum of the projected areas of these recesses on the first surface accounts for 10.1% of the total area of ​​the first surface.

[0108] (3) Positive electrode plate Lithium cobalt oxide, PVDF, and superconducting carbon black were mixed in N-methylpyrrolidone at a mass ratio of 97:2:1 to prepare a positive electrode slurry. The positive electrode slurry was then coated on both the front and back surfaces of the positive electrode current collector (aluminum foil). After drying and rolling, the positive electrode sheet was obtained.

[0109] (4) Electrolyte In an argon-filled glove box (moisture <1 ppm, oxygen <1 ppm), ethylene carbonate (EC), propylene carbonate (PC), propyl propionate, and ethyl propionate were mixed to form a homogeneous solvent. LiPF6, 1,3,6-hexanetrionitrile, and fluoroethylene carbonate were then slowly added, and the mixture was stirred until homogeneous to obtain the electrolyte. The electrolyte contained 16 wt% LiPF6, 20 wt% fluoroethylene carbonate, and 3 wt% 1,3,6-hexanetrionitrile. The weight ratio of ethylene carbonate (EC), propylene carbonate (PC), propyl propionate, and ethyl propionate was 15:15:50:20. It is understood that the sum of the weight percentages of all the above components in the electrolyte is 100%.

[0110] (5) Lithium-ion batteries The positive electrode sheet prepared in step (3), the negative electrode sheet prepared in step (2), and the separator prepared in step (1) are wound into a core according to a predetermined process. The electrolyte prepared in step (4) is injected, and the lithium-ion battery is prepared through vacuum sealing, settling, formation, sorting, and secondary sealing. The negative electrode sheet corresponds to the first adhesive layer in the separator, and the positive electrode sheet corresponds to the second adhesive layer in the separator. S×A / E=9×2 / 15=1.2.

[0111] Example 2 group This set of examples illustrates the effects of changes in battery structure.

[0112] Example 2a The procedure was carried out in accordance with Example 1, except that the negative electrode plate corresponds to the second adhesive layer side of the separator, and the positive electrode plate corresponds to the first adhesive layer of the separator.

[0113] Example 2b The procedure was carried out in accordance with Example 1, except that the second particles in the second adhesive layer were replaced with the same amount of first particles by weight.

[0114] Example 2c The procedure is carried out in accordance with Example 1, except that the first adhesive layer is located on the surface of the coating and the second adhesive layer is located on the other side of the substrate layer.

[0115] Example 2d The same procedure was followed as in Example 1, except that the coating was located on both sides of the substrate layer.

[0116] Example 3 Group This set of examples illustrates the effects that occur when the composition of the first particle changes.

[0117] Example 3a The procedure was carried out in accordance with Example 1, except that the first particle was composed of polyisooctyl methacrylate, and the weight percentage of the ester group in polyisooctyl methacrylate was 22.2%.

[0118] Example 3b The procedure was carried out in accordance with Example 1, except that the first particle was composed of polyethyl methacrylate, and the weight percentage of ester groups in the polyethyl methacrylate was 38.6%.

[0119] Example 4 group This set of embodiments is used to illustrate the effect when the proportion of primary particles with a particle size of less than 0.4 μm changes on the surface of the carrier layer (substrate layer).

[0120] Example 4a The same procedure was carried out as in Example 1, except that on the surface of the carrier layer (substrate layer), the proportion of the primary particles with a particle size of less than 0.4 μm was 1.1%, and the average particle size of the first particles was 0.85 μm.

[0121] Example 4b The same procedure was carried out as in Example 1, except that on the surface of the carrier layer (substrate layer), the proportion of primary particles with a particle size of less than 0.4 μm was 8.9%, and the average particle size of the first particles was 0.53 μm.

[0122] Example 5 group This set of examples illustrates the effects that occur when the composition of the second particle changes.

[0123] Example 5a The procedure was carried out in accordance with Example 1, except that the second particle was composed of HFP.

[0124] Example 5b The procedure was carried out in accordance with Example 1, except that the composition of the second particle was PVDF-HFP.

[0125] Example 6 group This set of examples illustrates the effects that occur when the composition of the third particle changes.

[0126] Example 6a The procedure was carried out in accordance with Example 1, except that the third particle was composed of melamine polyphosphate.

[0127] Example 6b The procedure was carried out in accordance with Example 1, except that the third particle was composed of piperazine pyrophosphate.

[0128] Example 6c The procedure was carried out in accordance with Example 1, except that the third particle was composed of melamine polyphosphate.

[0129] Example 7 group This set of examples illustrates the effects of changes in the structure of waterborne polyurethane.

[0130] Example 7a The process was carried out in accordance with Example 1, except that the hard segment monomer forming the waterborne polyurethane was diphenylmethane diisocyanate, and the soft segment monomer was dihydroxy-terminated polyethylene.

[0131] Example 7b The process was carried out in accordance with Example 1, except that the hard segment monomer forming the waterborne polyurethane was hexamethylene diisocyanate and the soft segment monomer was 2,2-dimethyl-1,3-propanediol.

[0132] Example 7c The process was carried out in accordance with Example 1, except that the hard segment monomer forming the waterborne polyurethane was isoflurane diisocyanate, and the soft segment monomer was dihydroxy-terminated hydrogenated polybutadiene.

[0133] Example 8 group This set of examples illustrates the effects of changes in S×A / E.

[0134] This embodiment group is based on Embodiment 1, except that S×A / E is changed, as detailed in Table 1.

[0135] Table 1 Example 9 group This set of embodiments is used to illustrate the effect when the sum of the orthographic projections of the concave portion onto the first surface changes as a percentage of the area on the first surface.

[0136] Example 9a The same procedure is followed as in Example 1, except that the sum of the orthographic projections of the recesses on the first surface accounts for 3.2% of the area of ​​the first surface.

[0137] Example 9b The same procedure is followed as in Example 1, except that the sum of the orthographic projections of the recesses on the first surface accounts for 50% of the area of ​​the first surface.

[0138] Example 9c The same procedure is followed as in Example 1, except that the sum of the orthographic projections of the recesses on the first surface accounts for 2.5% of the area of ​​the first surface.

[0139] Example 9d The same procedure is followed as in Example 1, except that the sum of the orthographic projections of the recesses on the first surface accounts for 0% of the area of ​​the first surface, meaning that there are no recesses on the first surfaces of the negative electrode active layers on both sides.

[0140] Example 9e The same procedure is followed as in Example 1, except that the sum of the orthographic projections of the recesses on the first surface accounts for 50.8% of the area of ​​the first surface.

[0141] Example 10 group This set of examples illustrates the effects of changes in the cyclic carbonates in the electrolyte.

[0142] Example 10a The experiment was conducted in accordance with Example 1, except that the mass ratio of the solvents ethylene carbonate (EC), propylene carbonate (PC), propyl propionate, and ethyl propionate in the electrolyte was adjusted so that the weight percentage of cyclic carbonates in the electrolyte was 3%.

[0143] Example 10a The same procedure was followed as in Example 1, except that the mass ratio of the solvents ethylene carbonate (EC), propylene carbonate (PC), propyl propionate, and ethyl propionate in the electrolyte was adjusted so that the weight percentage of cyclic carbonates in the electrolyte was 50%.

[0144] Example 10a The process was carried out in accordance with Example 1, except that the solvents in the electrolyte were replaced with difluoroethyl acetate (DFEA) instead of ethylene carbonate (EC) and propylene carbonate (PC), so that the weight percentage of cyclic carbonates in the electrolyte was 0%.

[0145] Example 10a The experiment was conducted in accordance with Example 1, except that the mass ratio of the solvents ethylene carbonate (EC), propylene carbonate (PC), propyl propionate, and ethyl propionate in the electrolyte was adjusted so that the weight percentage of cyclic carbonates in the electrolyte was 51%.

[0146] Example 11 The process was carried out in accordance with Example 1, except that the heat-resistant particles consisted of a third particle (MCA) and a fourth particle (boehmite), wherein the weight ratio of the third particle to the fourth particle was 50%:50%.

[0147] Example 12 The process is carried out in accordance with Example 1, except that the negative electrode active layer is divided into a first active layer and a second active layer. The first active layer is located between the negative electrode current collector and the second active layer. The weight percentage of waterborne polyurethane in the first active layer is 5.5%, and the weight percentage of waterborne polyurethane in the second active layer is 4%.

[0148] Comparative Example 1 The procedure was carried out in accordance with Example 1, except that the first particles were not present in either the first adhesive layer or the second adhesive layer.

[0149] Comparative Example 2 The same procedure was carried out as in Example 1, except that the average particle size of the first particles was changed so that the proportion of the primary particles with a particle size of less than 0.4 μm on the surface of the carrier layer (substrate layer) was 0.8%.

[0150] Comparative Example 3 The same procedure was carried out as in Example 1, except that the average particle size of the first particles was changed so that the proportion of the primary particles with a particle size of less than 0.4 μm on the surface of the carrier layer (substrate layer) was 9.2%.

[0151] Comparative Example 4 The parameter example 1 was performed, except that there was no waterborne polyurethane in the negative electrode active layer.

[0152] Test case The lithium-ion batteries prepared by the examples and comparative examples were subjected to the following tests.

[0153] 1. Room temperature cycling performance The lithium-ion battery was placed at 25℃±3℃ and charged at a constant current of 1 C to the upper limit voltage (4.53V). Then, it was charged at a constant voltage of 4.53V to 0.05C and allowed to rest for 5 minutes. Next, it was discharged at a constant current of 0.5C to 3V, and the discharge capacity at this point was recorded as Q1. After resting for 5 minutes, this constituted one charge-discharge cycle. After 800 charge / discharge cycles, the discharge capacity Q2 of the lithium-ion battery after 800T cycles was recorded. The capacity retention rate (%) was then calculated as (Q2 / Q1)×100%.

[0154] 2. Lithium plating test The lithium-ion battery was placed at 25℃±3℃ and charged at a constant current of 2C and 3C to the upper limit voltage (4.53V). Then, it was charged at a constant voltage of 4.53V to 0.05C and left to stand for 5 minutes. Next, it was discharged at a constant current of 0.5C to 3V, and the discharge capacity at this point was recorded as Q1. After standing for 5 minutes, this constituted one charge-discharge cycle. This charge / discharge cycle was repeated for 20 cycles. After 20 cycles, the battery was disassembled to check the lithium plating on the negative electrode in the first and third regions. When there was no lithium plating, it was considered no lithium plating. When the lithium plating area accounted for less than 3% of the total negative electrode area, it was considered slight lithium plating. When the lithium plating area accounted for 3%-10% of the total negative electrode area, it was considered lithium plating. When the lithium plating area accounted for more than 10.5% of the total negative electrode area, it was considered severe lithium plating.

[0155] 3. Ratio performance At 25℃±2℃, the battery is discharged to 3V at a constant current of 0.2C, and the initial discharge capacity is recorded as Q0. After standing for 10 minutes, it is fully charged at 0.7C (100% SOC), with a cutoff current of 0.025C. After standing for 10 minutes, it is discharged to 3V at a 3C rate and then stood for 10 minutes. The discharge capacity at this time is recorded as Q1. The rate discharge capacity retention rate is: Q1 / Q0×100%.

[0156] 4. Hot Box Test In an environment of 25℃±3℃, the battery was discharged at 0.2C to the cutoff voltage of 3.0V and left to stand for 10 minutes; then charged at 0.5C constant current and constant voltage to the upper limit voltage (4.53V), with a cutoff current of 0.02C. The fully charged cell (100% SOC) was placed in the test chamber, which was heated at a rate of (5±2)℃ / min. When the temperature inside the chamber reached 130℃±2℃, it was kept at that temperature for 60 minutes. After the test, the cell was observed to see if it caught fire. If it caught fire, it failed; if it did not catch fire, it passed. Each example and comparative example tested 20 battery samples, and the results were expressed as "number of passes / 20". For example, "20PASS / 20" means that all 20 battery samples passed the hot chamber test, and "5PASS / 20" means that only 5 out of 120 battery samples passed the hot chamber test.

[0157] 5. Volumetric energy density loss Energy density test: At 25℃±2℃, the battery is charged to full capacity (100% SOC) using a 0.5C current and then discharged to 3.0V using a 0.2C current. The discharged capacity is recorded as the battery discharge capacity, and the plateau voltage is read from the discharge curve. Energy density = (battery discharge capacity × plateau voltage) / battery volume.

[0158] Taking the energy density loss of Example 1 as an example, the energy density of the battery prepared in Example 9d is T1, and the energy density of the battery prepared in Example 1 is T2. Volumetric energy density loss (%) = [(T1-T2) / T1]×100%.

[0159] The results are recorded in Tables 2 and 3.

[0160] Table 2 Table 3 As can be seen from Tables 2 and 3, by comparing the comparative examples and the embodiments, the battery of the embodiments shows a significant improvement in room temperature cycle capacity retention, a significant improvement in 3C lithium plating, and a significant improvement in hot box passability. This indicates that by setting an ester-containing polymer in the separator's adhesive layer, adding amino groups to the negative electrode active layer, and controlling the proportion of primary particles with a particle size of less than 0.4 μm on the surface of the carrier layer, the interfacial stability between the negative electrode and the separator is improved, the risk of lithium plating is reduced, and the long-cycle performance and safety performance of the battery are enhanced.

[0161] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A battery, characterized by, The battery comprises a negative electrode sheet, a positive electrode sheet, an electrolyte, and a separator between the positive electrode sheet and the negative electrode sheet, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer on one side or both sides of the negative electrode current collector, the negative electrode active layer comprises an amino group; the separator comprises a carrier layer and a glue layer on one side or both sides of the carrier layer, the glue layer comprises first particles, the first particles are arranged in a stacked manner in the glue layer, the composition of the first particles is an ester-containing polymer, the first particles comprise primary particles, and the number ratio of the primary particles with a particle size less than 0.4 mu m to the total number of the primary particles on the surface of the carrier layer is 1%-9%; the negative electrode sheet corresponds to the side of the separator with the glue layer.

2. The battery of claim 1, wherein, The average particle size of the first particles is 0.5 mu m-0.95 mu m; And / or, the glue layer comprises first particles and second particles, the composition of the second particles is a fluorine-containing polymer; Preferably, the fluorine-containing polymer comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyfluoroethylene, polyhexafluoropropylene, fluorovinyl-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer; Preferably, the monomers forming the fluorine-containing polymer comprise one or more of vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, and hexafluoropropylene.

3. The battery of claim 1, wherein, The ester-containing polymer is an acrylate polymer; And / or, the ester-containing polymer comprises an ester-containing structure formed by an ester-containing monomer, and the weight ratio of the ester-containing structure in the ester-containing polymer is 50%-100%; And / or, the ester-containing polymer comprises one or more of polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, acrylate-acrylonitrile copolymer, acrylate-acrylonitrile-ethylene copolymer, styrene-acrylate-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; And / or, the monomers forming the ester-containing polymer comprise 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 glass transition temperature of the ester-containing polymer is 40℃-75℃.

4. The battery of claim 1, wherein, The glue layer is located on the surfaces of both sides of the carrier layer, the glue layer comprises a first glue layer and a second glue layer, the polymer particles in the first glue layer are first particles, the polymer particles in the second glue layer are first particles and second particles, the first glue layer corresponds to the negative electrode sheet, and the second glue layer corresponds to the positive electrode sheet.

5. The battery of any one of claims 1-4, wherein, The carrier layer comprises a substrate layer and a coating layer on one or both sides of the substrate layer, and the coating layer comprises heat-resistant particles; Preferably, the Dv50 of the heat-resistant particles is 0.2-2 μm; Preferably, the heat-resistant particles comprise third particles, and the third particles comprise an amino-containing organic compound; More preferably, the amino-containing organic compound comprises one or more of melamine polyphosphate, melamine trithiocyanate, melamine cyanurate, piperazine pyrophosphate, 4-amino-2,6-dihydroxypyrimidine, 6-aminopurine, and melamine polyphosphate.

6. The battery of any one of claims 1-4, wherein, The negative electrode active layer comprises a negative electrode binder, and the negative electrode binder comprises an aqueous polyurethane; Preferably, the weight percentage of the aqueous polyurethane in the negative electrode active layer is 0.6%-6%; Preferably, the molecular chain of the aqueous polyurethane comprises soft segments and hard segments, the structure of the soft segments comprises a 1 -O-R 1 -O-a 1 , R 1 is a chain alkyl, the chain alkyl is composed of a main chain selected from C3-C200 alkyl and an optional branched chain selected from C1-C40 alkyl, and the structure of the hard segments comprises , R 2 is a substituted or unsubstituted aliphatic ring, the number of carbon atoms n of the aliphatic ring is 5-20, T 1 is selected from 、 , wherein a 1 is a connecting site of the hard segments and the soft segments, a 2 is a connecting site of T 1 and the aliphatic ring of R 2 . Preferably, the weight ratio of the hard segment to the soft segment is (1-6):

1.

7. The battery of claim 6, wherein, The negative electrode active layer comprises a negative electrode active material, and the negative electrode active material comprises a silicon-based material, and the battery satisfies the following relationship: 0.09≤S×A / E≤22, wherein S is the Dv50 of the silicon-based material, in units of μm, A is the weight percentage of the aqueous polyurethane in the negative electrode active layer, and E is the coverage of the adhesive layer on the side corresponding to the negative electrode sheet on the surface of the carrier layer. And / or, the surface of the negative electrode active layer away from the negative electrode current collector is a first surface, and the first surface comprises a plurality of recesses, and the sum of the areas of the orthographic projections of the recesses on the first surface accounts for 3%-50% of the area of the first surface.

8. The battery of claim 7, wherein, The weight percentage of the aqueous polyurethane in the negative electrode active layer is 0.6%-6%; And / or, the coverage E of the adhesive layer on the side corresponding to the negative electrode sheet on the surface of the carrier layer is 5%-50%; And / or, the Dv50 of the silicon-based material is 5-20 μm; And / or, the silicon-based material comprises one or more of elemental silicon, silicon-nitrogen material, silicon alloy, silicon-oxygen material, and silicon-carbon material. Preferably, the silicon-carbon material comprises porous carbon and silicon particles, and the silicon particles are at least partially filled in the pores of the porous carbon.

9. The battery of claim 6, wherein, The negative electrode active layer comprises a first active layer and a second active layer, and the first active layer is located between the negative electrode current collector and the second active layer, and the weight percentage of the aqueous polyurethane in the first active layer is greater than the weight percentage of the aqueous polyurethane in the second active layer; Preferably, the weight percentage of the aqueous polyurethane in the first active layer is 0.5%-10%; Preferably, the weight percentage of the aqueous polyurethane in the second active layer is 0.5%-8%.

10. The battery of claim 1, wherein, The electrolyte comprises a cyclic carbonate, and the weight percentage of the cyclic carbonate in the electrolyte is 3%-50%, and the cyclic carbonate comprises ethylene carbonate and / or propylene carbonate; And / or, the charge cut-off voltage of the battery is greater than or equal to 4.5 V.

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