Negative plate and battery

Abstract

The invention provides a negative plate which comprises a negative current collector and a negative active layer located on at least one side surface of the negative current collector, the negative active layer comprises spherical silicon-based material particles and a composite conductive adhesive, the composite conductive adhesive comprises polyurethane and a conductive agent, the spherical silicon-based material particles are composed of first particles and second particles, the particle size of the first particles is larger than that of the second particles, the Dv50 of the first particles is 7-12 [mu] m, and the Dv50 of the second particles is 3-6.8 [mu] m; in the optional 25 [mu] m * 20 [mu] m area of the surface of the negative plate, the negative plate meets the following relational expression: 0.05 < = M / N < = 1, N is the number of the first particles, and M is the number of the second particles, the negative plate has good bonding network and conductive network stability, can relieve volume expansion in the charging and discharging process, and has good application prospects. And the volume energy density, the cycle performance and the rate capability of the battery are improved.

Description

Technical Field

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

[0002] With the rapid development of new energy vehicles and the large-scale energy storage market, higher requirements have been placed on the energy density of lithium-ion batteries. Silicon-based materials are considered an important direction for upgrading lithium-ion battery anode materials because their theoretical specific capacity is much higher than that of graphite.

[0003] However, silicon-based materials undergo significant volume changes during charging and discharging. Repeated expansion and contraction can cause active material particles to break and pulverize, resulting in the negative electrode active layer detaching from the negative electrode current collector and causing rapid capacity decay. Furthermore, when the negative electrode sheet undergoes volume changes under high silicon load, traditional binders have weak adhesion and cannot guarantee the stability of the bonding network. The reduced stability of the bonding network will further damage the conductive network, exacerbate the damage to the overall electrode structure, disrupt electron and lithium-ion transport paths, and ultimately lead to a sharp deterioration in kinetic performance.

[0004] Therefore, it is very important to alleviate the volume expansion of the negative electrode and improve its bonding stability and kinetic performance. Summary of the Invention

[0005] Studies have shown that silicon-based particles of a single size cannot simultaneously possess both kinetic performance and mechanical stability. For example, larger-sized silicon-based particles form a better bonding network with binders, but their lithium-ion transport performance is poor, resulting in poor kinetics of the negative electrode. Smaller-sized silicon-based particles have better lithium-ion transport performance, but their bonding network with binders is relatively poor, leading to significant powder shedding when the silicon particles expand in volume. Mixing silicon-based particles with larger and smaller sizes can improve the kinetic performance of the silicon particles and the adhesion of the bonding network formed by the silicon particles and binders. However, conventional binders (e.g., sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and styrene-butadiene rubber (SBR)) struggle to ensure the stability of the conductive and bonding networks under high silicon content loads.

[0006] To overcome the challenge of balancing kinetic performance and mechanical stability under high silicon content loads, this invention provides a negative electrode and a battery incorporating the negative electrode. The negative electrode of this invention can alleviate the volume expansion of silicon-based materials while improving the stability of the conductive and bonding networks, increasing the transport rates of lithium ions and electrons, and enhancing the kinetic performance and structural stability of the negative electrode. This, in turn, reduces the battery's expansion rate and improves its rate performance and cycle stability.

[0007] To achieve the above objectives, the first aspect of the present invention provides a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active layer located on at least one side surface of the negative electrode current collector, the negative electrode active layer comprising spherical silicon-based material particles and a composite conductive adhesive, the composite conductive adhesive comprising polyurethane and a conductive agent, the spherical silicon-based material particles being composed of a first particle and a second particle, wherein the particle size of the first particle is larger than the particle size of the second particle, the Dv50 of the first particle is 7μm-12μm, and the Dv50 of the second particle is 3μm-6.8μm; Within an area of ​​25μm × 20μm on the surface of the negative electrode, the negative electrode satisfies the following relationship: 0.05 ≤ M / N ≤ 1, where N is the number of the first particles and M is the number of the second particles.

[0008] A second aspect of the present invention provides a battery comprising the negative electrode sheet described in the first aspect of the present invention.

[0009] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: The negative electrode sheet of this invention comprises a composite conductive adhesive and spherical silicon-based material particles. The composite conductive adhesive includes polyurethane and a conductive agent. Polyurethane possesses both high flexibility and high adhesion, while the conductive agent ensures electron transport. The composite conductive adhesive, including both polyurethane and a conductive agent, combines high flexibility, adhesion, and conductivity. Therefore, the conductive bonding network formed by the composite conductive adhesive possesses high flexibility, high adhesion, and high conductivity. The spherical silicon-based material particles consist of first particles and second particles, with the first particles having a larger particle size than the second particles. That is, the spherical silicon-based material particles are composed of particles of different sizes. The first particles with larger particle sizes can form a strong bonding network through the composite conductive adhesive, thereby constructing a bonding network framework. The second particles with smaller particle sizes... The particles can fill the gaps between the larger-diameter first particles, which not only improves the compaction density of the negative electrode and the volumetric energy density of the battery, but also significantly shortens the transport path of lithium ions and electrons, compensating for the poor kinetic performance of larger-diameter spherical silicon-based material particles. Moreover, the three-dimensional flexible network formed by the composite conductive adhesive can tightly wrap the first and second particles, providing a buffer when the silicon-based material particles deform through its own flexibility, thereby reducing the expansion rate of the negative electrode and improving the structural stability of the negative electrode. At the same time, the three-dimensional flexible network formed by the composite conductive adhesive, which includes polyurethane and conductive agents, is also conductive, ensuring efficient electron transport even when the volume of the silicon-based material particles changes, further improving the kinetic performance of the negative electrode. Therefore, the three-dimensional flexible network formed by the composite conductive adhesive in the negative electrode sheet of the present invention has high flexibility, high adhesion and high conductivity. It can not only tightly wrap the first particle with a larger particle size and the second particle with a smaller particle size, improving the dynamic performance of silicon-based particles and the adhesion between silicon-based particles and the bonding network, but also maintain the structural stability of the conductive three-dimensional flexible network through the dense and stable physical structure when the silicon-based material particles undergo volume changes. At the same time, it maintains the integrity and conductivity of the negative electrode sheet by chemical bonding, thereby improving the stability of the conductive network and the bonding network, thereby reducing the expansion rate of the battery and improving the rate performance and cycle stability of the battery.

[0010] In addition, by controlling the ratio of the number of first particles to the number of second particles in a region of 25μm×20μm on the surface of the negative electrode sheet, the present invention can, on the one hand, improve the matching of the first particles and the second particles, further improving the volumetric energy density of the battery; on the other hand, it can minimize the expansion of the contact interface between the negative electrode and the separator and minimize the interface resistance, thereby enabling the battery to have a low expansion rate, high rate performance, high cycle performance and high energy density.

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

[0012] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Attached Figure Description

[0013] Figure 1 The image shown is one of the cross-sectional views of the negative electrode sheet in the battery of the present invention.

[0014] Figure 2 The image shown is a second cross-sectional view of the negative electrode in the battery of the present invention. Detailed Implementation

[0015] 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.

[0016] 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.

[0017] The first aspect of the present invention provides a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active layer located on at least one side surface of the negative electrode current collector, the negative electrode active layer comprising spherical silicon-based material particles and a composite conductive adhesive, the composite conductive adhesive comprising polyurethane and a conductive agent, the spherical silicon-based material particles being composed of first particles and second particles, wherein the particle size of the first particles is larger than the particle size of the second particles, the Dv50 of the first particles is 7μm-12μm (e.g., 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm), and the Dv50 of the second particles is 3μm-6.8μm (e.g., 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.8μm); Within an area of ​​25μm × 20μm on the surface of the negative electrode, the negative electrode satisfies the following relationship: 0.05 ≤ M / N ≤ 1 (for example, 0.05, 0.15, 0.25, 0.35, 0.45, 0.55, 0.65, 0.75, 0.85, 0.95, 1), where N is the number of the first particles and M is the number of the second particles.

[0018] In this invention, the particle size of the first particle being larger than that of the second particle means that the Dv50 of the first particle is greater than that of the second particle. Specifically, by arbitrarily selecting a 20μm×20μm region on the surface of the negative electrode active layer, if two spherical silicon-based material particles with significant differences in particle size can be observed on a single SEM scan image, it indicates that a first particle and a second particle exist in the negative electrode, and the particle size of the first particle is larger than that of the second particle. If the particle size difference of the spherical silicon-based material particles observed in the arbitrarily selected 20μm×20μm region is not significant, it indicates that the first particle and the second particle in the negative electrode do not satisfy the condition that the particle size of the first particle is larger than that of the second particle.

[0019] The negative electrode active layer of the present invention comprises two spherical silicon-based material particles of different sizes and a composite conductive adhesive. The composite conductive adhesive comprises polyurethane and a conductive agent. The polyurethane in the composite conductive adhesive has flexibility and adhesion, and can form a strong three-dimensional flexible bonding network to tightly wrap the spherical silicon-based material particles. On the one hand, its excellent flexibility allows it to buffer the volume change stress of the spherical silicon-based material during charging and discharging through its own deformation. On the other hand, its good bonding performance improves the bonding stability of the spherical silicon-based material particles, preventing the spherical silicon-based material particles from cracking, pulverizing and falling off. It can also improve the adhesion between the negative electrode active layer and the negative electrode current collector, thereby maintaining the integrity of the negative electrode structure and improving the cycle stability of the battery. Furthermore, the conductive agent in the composite conductive adhesive enables the three-dimensional flexible bonding network formed by the polyurethane to have high conductivity, ensuring that electrons can still be transported efficiently during the volume change of the spherical silicon-based material. This simultaneously improves the stability of the conductive network and the bonding network of the negative electrode, and enhances the dynamic performance of the negative electrode.

[0020] Meanwhile, the Dv50 of the first particle is 7μm-12μm, and the Dv50 of the second particle is 3μm-6.8μm. The particle size of the first particle is larger than that of the second particle. In a randomly selected 25μm×20μm area on the surface of the negative electrode sheet, the number of the first and second particles satisfies the relationship: 0.05≤M / N≤1. This allows the first particles in the negative electrode sheet to be bonded together by the composite conductive adhesive to form a strong structural skeleton, suppressing the overall macroscopic expansion of the negative electrode sheet. The second particles effectively fill the gaps formed between the first particles, which not only improves the compaction density of the negative electrode sheet and the volumetric energy density of the battery, but also significantly shortens the lithium-ion diffusion path, improves the lithium-ion transport efficiency in the negative electrode sheet, and further improves the kinetic performance, thereby reducing the expansion rate of the battery and improving the rate performance, cycle stability and volumetric energy density of the battery.

[0021] Therefore, the negative electrode sheet of the present invention, through the construction of a flexible three-dimensional network with both adhesive and conductive properties using composite conductive adhesive, and the mixing of two first and second particles of different sizes, improves the compaction density of the negative electrode sheet and the volumetric energy density of the battery, and significantly shortens the lithium-ion diffusion path, thereby improving the lithium-ion transport efficiency in the negative electrode sheet. On the other hand, when the negative electrode sheet is subjected to volume changes of silicon-based materials, it can not only provide a buffer for the expansion of silicon-based particles, reducing the volume expansion of the negative electrode sheet, but also enhance the stability of the bonding network, maintain the complete structural morphology of the negative electrode sheet, and at the same time have excellent conductivity and lithium-ion transport capability, thereby improving the volumetric energy density, cycle stability, cycle life and rate performance of the battery.

[0022] In this invention, the Dv50 of the first particle refers to the particle size at which the cumulative volumetric particle size distribution percentage of the first particles reaches 50%, arranged in ascending order of particle size. In this invention, the volumetric particle size distribution of the first particle can be obtained by measuring and statistically processing any 100μm × 100μm area in an SEM image of the negative electrode surface using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, ParticleMetric, etc.). The Dv50 of the first particle can also be obtained by testing with a laser particle size analyzer. Preferably, the Dv50 of the first particle is obtained by testing with a laser particle size analyzer.

[0023] In this invention, the Dv50 of the second particle refers to the particle size at which the cumulative volumetric particle size distribution percentage of the second particles reaches 50%, arranged in ascending order of particle size. In this invention, the volumetric particle size distribution of the second particle can be obtained by measuring and statistically processing any 100μm × 100μm area in an SEM image of the negative electrode surface using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, ParticleMetric, etc.). The Dv50 of the second particle can also be obtained by testing with a laser particle size analyzer. Preferably, the Dv50 of the second particle is obtained by testing with a laser particle size analyzer.

[0024] In this invention, the number N of the first particles and the number M of the second particles are measured in a randomly selected 25μm×20μm area on the surface of the negative electrode sheet by the following method: the surface of the negative electrode sheet is observed by scanning electron microscopy (SEM) at a magnification of 5K. A 25μm×20μm area containing the first and second particles is randomly selected. On the SEM scan image, combined with image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, ParticleMetric, etc.), measurement and statistical processing are performed to obtain the particle size of all the first and second particles. The total number of first particles in this area is N, and the number of second particles is M. M / N is calculated. The above operation is repeated 5 times, and the average value is taken as the final test result.

[0025] In this invention, by introducing a composite conductive adhesive and two types of spherical silicon-based material particles of different sizes into the negative electrode active layer, the volume expansion of the negative electrode sheet can be reduced compared to existing technologies. Furthermore, when the silicon-based material particles undergo volume changes, the stability of the bonding and conductive networks of the negative electrode sheet is improved, thereby reducing the battery's expansion rate and improving its rate performance, cycle stability, and volumetric energy density. To further enhance the effect, one or more of the technical features can be further optimized.

[0026] In some embodiments, in the spherical silicon-based material particles, the weight ratio of the first particle to the second particle is (1-19):1 (e.g., 1:1, 2:1, 2.5:1, 3:1, 4:1, 5:1, 8:1, 10:1, 13:1, 15:1, 19:1). It is understood that in the spherical silicon-based material particles, the weight percentage of the first particle can be in the range of 50%-95% (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%), and the weight percentage of the second particle can be in the range of 50%-5% (e.g., 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, or 5%), but the sum of the weight percentages of the first particle and the second particle must be 100%.

[0027] In some embodiments, in the spherical silicon-based material particles, the weight percentage of the first particle can be 50%-95% (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95%), and the weight percentage of the second particle is 50%-5% (e.g., 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10% or 5%).

[0028] In some embodiments, the spherical silicon-based material particles include one or more of silicon-carbon particles, silicon-oxygen particles, elemental silicon particles, silicon-oxygen compound particles, silicon-nitrogen composite particles, and silicon alloy particles.

[0029] In some embodiments, the spherical silicon-based material particles include silicon-carbon particles and / or silicon-oxygen particles.

[0030] In one specific embodiment, the spherical silicon-based material particles are spherical silicon-carbon particles.

[0031] In some embodiments, the areal density of the negative electrode active layer is less than or equal to 10 mg / cm³. 2 (For example, 0.5 mg / cm) 2 1mg / cm 2 2mg / cm 2 3mg / cm 2 4mg / cm 2 5mg / cm 2 6mg / cm 2 7mg / cm 2 8mg / cm 2 9mg / cm 2 Or 10mg / cm 2 ).

[0032] In this invention, the areal density of the negative electrode active layer represents the areal density of a single-sided negative electrode active layer. When there is a negative electrode active layer on one side of the negative electrode current collector, the areal density of the negative electrode active layer is the areal density of that side. When there are negative electrode active layers on both sides of the negative electrode current collector, the areal densities of the negative electrode active layers on both sides are the same, and the areal density of the negative electrode active layer is the areal density of either side.

[0033] In some embodiments, the weight percentage of silicon in the negative electrode active layer is 2%-50% (e.g., 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%).

[0034] In this invention, the weight percentage of silicon in the negative electrode active layer can be measured by the following method: for example, after discharging the battery to 0% SOC, the negative electrode sheet is disassembled and removed. It is then soaked in dimethyl carbonate (DMC) solvent for 12 hours, followed by rinsing with DMC solvent to remove lithium salts adhering to the negative electrode sheet. After drying, the negative electrode sheet is subjected to high-temperature treatment at 400°C in an inert atmosphere for 2 hours (e.g., in a tube furnace under nitrogen or argon atmosphere). The negative electrode active layer can then be peeled off from the negative electrode current collector, and the negative electrode active layer is collected as a test sample. Using a thermogravimetric analyzer (e.g., a TGA 550 thermogravimetric analyzer), the sample amount is 5mg-15mg. Under an air or oxygen atmosphere, the temperature is increased from room temperature (25°C) to 900°C at a rate of 10°C / min, and held at 900°C for 40 minutes. This allows the non-silicon components in the negative electrode active layer to volatilize while silicon is fully oxidized to silicon dioxide. The remaining substance is the ash of the negative electrode active layer. The weight ratio of silicon in the negative electrode active layer can be calculated based on the weight of the ash. The calculation formula is as follows: weight ratio of silicon in the negative electrode active layer = 7 × weight of ash / (15 × weight of test sample).

[0035] In some embodiments, the sphericity of the spherical silicon-based material particles is 0.8-1 (e.g., 0.8, 0.85, 0.9, 0.95 or 1).

[0036] In this invention, the sphericity of the spherical silicon-based material particles is measured using the following method: A scanning electron microscope (SEM) is used to capture images of the particles on the surface of the negative electrode active layer. Within an arbitrarily selected 100μm × 100μm area in the image, spherical silicon-based material particles are identified using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, ParticleMetric, etc.). The radius r1 of the equivalent circle representing the projected circumference of a single spherical silicon-based material particle and the radius r2 of the equivalent circle representing the projected area of ​​the spherical silicon-based material particle are calculated. The sphericity of a single spherical silicon-based material particle is calculated as r2 / r1. The sphericity of 100 spherical silicon-based material particles is averaged. This process is repeated five times, and the average value is the final test result. The scanned images can be obtained by observing the surface of the negative electrode using a scanning electron microscope (S-3400N manufactured by Hitachi, Ltd.).

[0037] In some embodiments, the composite conductive adhesive is formed by premixing polyurethane and a conductive agent.

[0038] In some embodiments, the polyurethane includes a hard segment structure and a soft segment structure. The polymer monomer forming the hard segment structure is a hard segment molecule, which includes the structure shown in Formula I. The polymer monomer forming the soft segment structure includes a soft segment molecule, which includes the structure shown in Formula II. OCN-R n1 -NCO (Formula I) Where n1≥1 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10), and R is selected from M. 1 Metacarbocyclic structure, M 1 ≥5 (e.g., 5, 6, 7, 8, 9, or 10); (Formula II) Wherein, n3 = 5-200 (e.g., 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190 or 200), n4 = 0-40 (e.g., 0, 5, 10, 15, 20, 25, 30, 35 or 40), and the side chain end group b is selected from at least one of hydrogen atom, methyl, cyano, and amide.

[0039] In this invention, when the polyurethane comprises a hard segment structure and a soft segment structure, the hard segment structure contains polarized hydrogen, which can form abundant hydrogen bonds, providing a stable rigid structure for the negative electrode sheet and helping to maintain the original shape of the negative electrode sheet. The soft segment structure has high elasticity and flexibility, which can quickly release the expansion stress of the spherical silicon-based material and adapt to the expansion and contraction of the spherical silicon-based material particles, thereby maintaining the stability of the negative electrode sheet bonding network and conductive network, ensuring the structural stability of the negative electrode sheet, further avoiding the capacity decay of the negative electrode sheet, improving the dynamic performance, and enhancing the cycle stability of the battery.

[0040] In some embodiments, the hard segment structure and the soft segment structure can be connected by a urethane bond -NH-(C=O)-O-.

[0041] In some embodiments, the hard segment molecule includes at least one selected from 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, norbornene diisocyanate, adamantane diisocyanate, and hydrogenated toluene diisocyanate, and the soft segment molecule includes at least one selected from 2-methyl-1,5-pentanediol, dihydroxy-terminated polyethylene, and dihydroxy-terminated hydrogenated polybutadiene.

[0042] In some embodiments, the weight percentage of the hard segment structure in the polyurethane is 20%-85% (e.g., 20%, 30%, 40%, 50%, 60%, 70%, 80% or 85%), and the weight percentage of the soft segment structure is 5%-50% (e.g., 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%).

[0043] In some embodiments, the hard segment molecule includes at least one of 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, norbornene diisocyanate, adamantane diisocyanate, and hydrogenated toluene diisocyanate.

[0044] In some embodiments, the soft segment molecule includes at least one of 2-methyl-1,5-pentanediol, dihydroxy-terminated polyethylene, and dihydroxy-terminated hydrogenated polybutadiene.

[0045] In some embodiments, the polyurethane is synthesized from hard segment molecules, soft segment molecules, crosslinking agent molecules, hydrophilic chain extender molecules, catalyst molecules, chain extender molecules, and salification neutralizer molecules. Based on the total weight of the hard segment molecules, soft segment molecules, crosslinking agent molecules, hydrophilic chain extender molecules, catalyst molecules, chain extender molecules, and salification neutralizer molecules, the weight percentage of the crosslinking agent molecules is 20%-85% (e.g., 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or 85%), and the weight ratio of the salification neutralizer molecules to the hydrophilic chain extender molecules is 20%-90% (e.g., 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%).

[0046] In some embodiments, the crosslinking agent molecule includes at least one of trimethylolpropane, glycerol, pentaerythritol, and tris(2-hydroxyethyl)isocyanurate.

[0047] In some embodiments, the hydrophilic chain extender molecule includes at least one of 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvalerate, dihydroxymaleic acid, 2,6-dihydroxybenzoic acid, and 3,4-diaminobenzoic acid.

[0048] In some embodiments, the catalyst molecule includes at least one of dibutyltin dilaurate, stannous octanoate, dibutyltin diacetate, dibutyltin thiolate, bismuth isooctanoate, and bismuth neodecanoate.

[0049] In some embodiments, the chain extender molecule includes at least one selected from ethylenediamine, isophorone diamine, diethyltoluene diamine, di-n-butylamine, diethylenetriamine, and triethylamine.

[0050] In some embodiments, the salting neutralizer molecule includes at least one of triethylamine, lithium hydroxide, sodium hydroxide, lithium carbonate, and sodium carbonate.

[0051] In some embodiments, the conductive agent includes at least one of carbon nanotubes, carbon black, and graphene, wherein the aspect ratio of the carbon nanotubes in the conductive agent is greater than 1500 (e.g., 1501, 1600, 1700, 1800, 1900, 2000, or 3000).

[0052] The conductive agent includes carbon nanotubes, and the aspect ratio of the carbon nanotubes in the conductive agent is controlled to be greater than 1500. This can effectively improve the conductivity of the composite conductive adhesive in the negative electrode active layer, which is conducive to building a stable conductive network in the negative electrode active layer, further improving the dynamic performance of the negative electrode sheet, and improving the cycle stability and cycle life of the battery.

[0053] In this invention, the aspect ratio of the carbon nanotube refers to the average ratio of the length to the diameter of the carbon nanotube. The aspect ratio is measured using a transmission electron microscope (TEM). Twenty carbon nanotubes are randomly selected within a field of view, and the diameter and length of each nanotube are measured. The ratio of the length to the diameter of these 20 nanotubes is calculated, and the arithmetic mean is taken as the aspect ratio. It is understood that when a carbon nanotube has an outer diameter and an inner diameter, the outer diameter is used.

[0054] In some embodiments, the polyurethane in the composite conductive adhesive has a weight percentage of 94%-99.5% (e.g., 94%, 95%, 96%, 97%, 98%, 99%, or 99.5%), and the conductive agent has a weight percentage of 0.5%-6% (e.g., 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, or 6%).

[0055] In some embodiments, the composite conductive adhesive accounts for 1%-12% of the weight of the negative electrode active layer (e.g., 1%, 2%, 4%, 5%, 7%, 9%, 10%, 11% or 12%).

[0056] In this invention, when the negative electrode active layer is a single layer, the proportion of composite conductive adhesive refers to the ratio of the weight of the composite conductive adhesive in the 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, the proportion of composite conductive adhesive refers to the ratio of the sum of the weights of the composite conductive adhesives in all active layers to the total weight of all negative electrode active layers.

[0057] In some embodiments, the negative electrode active layer further includes a third conductive agent, a dispersant, and an additive. The third conductive agent includes single-walled carbon nanotubes. The dispersant includes at least one of lithium carboxymethyl cellulose, modified lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, and modified sodium carboxymethyl cellulose. The additive includes at least one of lithium polyacrylate, modified lithium polyacrylate, sodium polyacrylate, modified sodium polyacrylate, styrene-butadiene rubber, and modified styrene-butadiene rubber.

[0058] In some embodiments, the negative electrode sheet satisfies the following relationship: 45%≤[I / (I+J+K+L)]×100%≤90% (for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%), where I is the weight percentage of the composite conductive adhesive in the negative electrode active layer, in %, J is the weight percentage of the dispersant in the negative electrode active layer, in %, K is the weight percentage of the third conductive agent in the negative electrode active layer, in %, and L is the weight percentage of the additives in the negative electrode active layer, in %.

[0059] In this invention, when the negative electrode sheet satisfies the above-mentioned relationship, the composite conductive adhesive, dispersant, third conductive agent, and additives can jointly construct a flexible bonding network and a stable rigid structure, alleviate the volume expansion of the negative electrode sheet, prevent the spherical silicon-based material particles from breaking and the negative electrode active material layer from falling off, ensure the structural integrity of the negative electrode sheet, further avoid capacity decay, ensure that the battery has a high volumetric energy density, and at the same time construct a conductive network, enabling electrons to be transported stably and quickly in the negative electrode sheet, improving dynamic performance, and further improving the cycle stability of the battery.

[0060] According to one specific implementation, I is 1%-12%, and the negative electrode sheet satisfies the following relationship: 45%≤[I / (I+J+K+L)]×100%≤90%.

[0061] In some embodiments, the third conductive agent comprises single-walled carbon nanotubes having an aspect ratio greater than 1500 (e.g., 1510, 1600, 1650, 1700, 1750, 1800, 1850 or 2000).

[0062] The third conductive agent includes single-walled carbon nanotubes, and the aspect ratio of the single-walled carbon nanotubes is controlled within the above range. The single-walled carbon nanotubes and the composite conductive adhesive can jointly construct a stable conductive network, providing a stable and fast transport path for electrons, effectively improving the dynamic performance of the negative electrode, and further consolidating and improving the long-term cycle life and stability of the battery.

[0063] In this invention, the aspect ratio of the single-walled carbon nanotube refers to the average ratio of the length to the diameter of the single-walled carbon nanotube. The aspect ratio is measured using the following method: Twenty single-walled carbon nanotubes are randomly selected within a field of view using a transmission electron microscope (TEM). The diameter and length of each single-walled carbon nanotube are measured, and the ratio of the length to the diameter of these 20 single-walled carbon nanotubes is calculated. The arithmetic mean of these ratios is the aspect ratio of the single-walled carbon nanotube. It is understood that when a single-walled carbon nanotube has an outer diameter and an inner diameter, the outer diameter is used.

[0064] In some embodiments, the negative electrode sheet includes a base coating layer located between the negative electrode current collector and the negative electrode active layer. The base coating layer includes styrene-butadiene rubber and a fourth conductive agent, wherein the fourth conductive agent includes carbon nanotubes and / or carbon black.

[0065] Styrene-butadiene rubber (SBR) possesses excellent adhesion and good compatibility with polyurethane in the composite conductive adhesive, thus forming a strong chemical bond with both the negative electrode current collector and the negative electrode active layer, including the composite conductive adhesive. Simultaneously, the electrolyte provides excellent physical wetting. Furthermore, SBR's high elasticity effectively buffers the significant expansion stress of the negative electrode sheet during cycling, preventing brittle delamination at the interface between the negative electrode active layer and the negative electrode current collector. The fourth conductive agent possesses mechanical strength and good conductivity, forming a stable three-dimensional conductive network within the SBR, constructing a highly efficient electron transport channel directly to the current collector, and improving the interfacial conductivity between the negative electrode current collector and the negative electrode active layer. The undercoat layer, comprising SBR and the fourth conductive agent, constructs a flexible interconnect layer with strong adhesion, high wettability, high elasticity, and high conductivity between the negative electrode active layer and the negative electrode current collector. This ensures the bonding stability of the negative electrode active layer and the negative electrode current collector, avoiding the risk of delamination, while also improving kinetic performance, thereby further enhancing the battery's cycle stability and cycle life.

[0066] In some embodiments, the styrene-butadiene rubber accounts for more than 60% by weight in the base coating (e.g., 61%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%). In some embodiments, the fourth conductive agent in the base coating layer accounts for 10%-30% by weight (e.g., 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, or 30%).

[0067] In some embodiments, the base coating layer further includes a base coating dispersant, wherein the base coating dispersant is at least one of lithium carboxymethyl cellulose, modified lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, and modified sodium carboxymethyl cellulose.

[0068] In some embodiments, the weight percentage of the dispersant in the base coating is less than 10% (e.g., 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1%).

[0069] In some embodiments, the negative electrode active layer is layered (e.g.) Figure 1 ) or not layered (e.g.) Figure 2 ).

[0070] In some embodiments, such as Figure 2 As shown, the negative electrode active layer includes a negative electrode active layer 14.

[0071] In some embodiments, such as Figure 1 As shown, the negative electrode active layer includes a first negative electrode coating 12 and a second negative electrode coating 13. The second negative electrode coating 13 is located between the negative electrode current collector 11 and the first negative electrode coating 12. The first negative electrode coating includes a first spherical silicon-based material particle and a first composite conductive adhesive. The second negative electrode coating includes a second spherical silicon-based material particle and a second composite conductive adhesive.

[0072] In this invention, the negative electrode active layer includes a first negative electrode coating and a second negative electrode coating located between the negative electrode current collector and the first negative electrode coating. The first negative electrode coating includes a first composite conductive adhesive, and the second negative electrode coating includes a second composite conductive adhesive. The first composite conductive adhesive includes polyurethane and a first conductive agent, and the second composite conductive adhesive includes polyurethane and a second conductive agent. It can be understood that the negative electrode sheet includes two negative electrode active layers, namely a first negative electrode coating located on the surface and a second negative electrode coating located on the bottom layer. Both negative electrode active layers include a composite conductive adhesive containing polyurethane and a conductive agent.

[0073] In some embodiments, the weight percentage of the first spherical silicon-based material particles in the first negative electrode coating is greater than the weight percentage of the second spherical silicon-based material particles in the second negative electrode coating.

[0074] In some embodiments, the negative electrode sheet satisfies the following relationship: ac ≥ 1% (e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%), where a is the weight percentage of the first spherical silicon-based material particles in the first negative electrode coating, and c is the weight percentage of the second spherical silicon-based material particles in the second negative electrode coating.

[0075] In this invention, the weight ratio of the first spherical silicon-based material particles in the first negative electrode coating and the weight ratio of the second spherical silicon-based material particles in the second negative electrode coating are controlled. When the negative electrode sheet satisfies the above relationship, the weight ratio of spherical silicon-based material particles in the surface first negative electrode coating is higher. During charging, the expansion rate of the surface first negative electrode coating is greater. The stress release during the expansion of the spherical silicon-based material particles will change their position, increasing the porosity of the surface first negative electrode coating, thereby improving the wettability of the electrolyte, improving the transport capacity of lithium ions in the first negative electrode coating, further improving the dynamic performance of the negative electrode sheet, and improving the rate performance and cycle stability of the battery.

[0076] In some embodiments, the weight percentage of the first spherical silicon-based material particles in the first negative electrode coating is 8%-97%, and the weight percentage of the second spherical silicon-based material particles in the second negative electrode coating is 8%-96%.

[0077] In some embodiments, the weight percentage of the first spherical silicon-based material particles in the first negative electrode coating is 86%-97%, and the weight percentage of the second spherical silicon-based material particles in the second negative electrode coating is 85%-96%.

[0078] In this invention, the negative electrode active layer includes spherical silicon-based material particles, which include a first particle and a second particle. It is understood that when the negative electrode active layer includes a first negative electrode coating and a second negative electrode coating, the spherical silicon-based material particles in the first negative electrode coating are first spherical silicon-based materials, and the spherical silicon-based material particles in the second negative electrode coating are second spherical silicon-based materials. The first spherical silicon-based material includes the first particle and the second particle. In the first spherical silicon-based material, the weight ratio of the first particle to the second particle is (50%-95%):(50%-5%). The second spherical silicon-based material includes the first particle and the second particle. In the second spherical silicon-based material, the weight ratio of the first particle to the second particle is (50%-95%):(50%-5%).

[0079] In some embodiments, the areal density of the first negative electrode coating is 1 mg / cm³. 2 -5mg / cm 2 (For example, 1 mg / cm) 2 1.5 mg / cm 2 mg / cm 2 2.5 mg / cm 2 3mg / cm 2 3.5 mg / cm 2 4mg / cm 2 4.5 mg / cm 2 Or 5mg / cm 2 ).

[0080] In some embodiments, the areal density of the second negative electrode coating is 2 mg / cm³. 2 -5mg / cm 2 (For example, 2mg / cm) 2 2.5 mg / cm 2 3mg / cm 2 3.5 mg / cm 2 4mg / cm 2 4.5 mg / cm 2 Or 5mg / cm 2 ).

[0081] In some embodiments, the weight percentage of the first composite conductive adhesive in the first negative electrode coating is less than the weight percentage of the second composite conductive adhesive in the second negative electrode coating.

[0082] In this invention, the weight percentage of the first composite conductive adhesive in the first negative electrode coating is controlled to be less than that of the second composite conductive adhesive in the second negative electrode coating. The first negative electrode coating on the surface has a relatively small weight percentage of composite conductive adhesive, resulting in lower adhesion of the silicon-based material particles. When the first negative electrode coating on the surface expands, the position of the spherical silicon-based material particles changes further under the expansion stress, further increasing the porosity of the first negative electrode coating on the surface, thereby improving lithium-ion transport capacity, enhancing the kinetic performance of the negative electrode sheet, and improving the rate performance and cycle stability of the battery. Conversely, the second negative electrode coating on the bottom layer has a relatively large weight percentage of composite conductive adhesive, tightly wrapping the spherical silicon-based material particles, mitigating their expansion, and improving their adhesion stability. At the same time, the bottom second negative electrode coating is in direct contact with the negative electrode current collector, further enhancing the adhesion between the negative electrode active layer and the negative electrode current collector, thereby maintaining the structural integrity of the negative electrode sheet, improving the stability of the negative electrode sheet bonding network and conductive network, and further improving the cycle stability and kinetic performance of the battery.

[0083] In some embodiments, the weight percentage of the first composite conductive adhesive in the first negative electrode coating is 1%-6% (e.g., 1%, 2%, 3%, 4%, 5% or 6%).

[0084] In some embodiments, the weight percentage of the second composite conductive adhesive in the second negative electrode coating is 2%-12% (e.g., 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11% or 12%).

[0085] In some embodiments, the first composite conductive adhesive includes a first polyurethane and a first conductive agent, and the second composite conductive adhesive includes a second polyurethane and a second conductive agent, wherein the first conductive agent and the second conductive agent each independently include at least one of carbon nanotubes, carbon black, and graphene.

[0086] In some embodiments, in the first composite conductive adhesive, the weight percentage of the first polyurethane is 94%-99.5% (e.g., 94%, 95%, 96%, 97%, 98%, 99%, or 99.5%), and the weight percentage of the first conductive agent is 0.5%-6% (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, or 6%).

[0087] In some embodiments, in the second composite conductive adhesive, the weight percentage of the second polyurethane is 94%-99.5% (e.g., 94%, 95%, 96%, 97%, 98%, 99%, or 99.5%), and the weight percentage of the second conductive agent is 0.5%-6% (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, or 6%).

[0088] A second aspect of the present invention provides a battery comprising the aforementioned negative electrode.

[0089] In some embodiments, the battery further includes a positive electrode and an electrolyte.

[0090] In some embodiments, the positive electrode sheet can be a conventional positive electrode sheet in the art. For example, the positive electrode sheet includes a positive current collector and a positive active layer located on at least one side of the positive current collector. The positive active layer includes a positive active material, such as lithium nickel oxide, lithium titanate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, or lithium manganese oxide.

[0091] In some embodiments, the electrolyte may be a conventional electrolyte in the art, for example, the electrolyte may include lithium salts, organic solvents and additives.

[0092] In some embodiments, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0093] In some embodiments, the organic solvent in the electrolyte includes at least one of propylene carbonate, ethylene carbonate, 2,2-difluoroethyl acetate, ethyl 2,2-difluoroethyl acetate, methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), and ethyl butyrate (EB).

[0094] In some embodiments, the additive includes at least one of nitrile compounds, fluorinated chain carbonates, fluoroethylene carbonates, and sulfur-containing compounds.

[0095] 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.

[0096] Example I-1 (1) Selection of diaphragm: A diaphragm with a single-sided ceramic layer and a double-sided oil-based adhesive layer is selected. The substrate of the diaphragm is a polyethylene film with a thickness of 5μm. A ceramic layer with a thickness of 1.5μm is disposed on the surface of the substrate. An oil-based adhesive layer with a thickness of 2μm, composed of polyvinylidene fluoride, is disposed on both the surface of the substrate and the surface of the ceramic layer.

[0097] (2) Preparation of the positive electrode: Lithium cobalt oxide, PVDF, and carbon black were mixed in N-methylpyrrolidone at a mass ratio of 97:2:1 to prepare a positive electrode slurry. This positive electrode slurry was then coated onto both the front and back surfaces of a positive electrode current collector (aluminum foil). After drying and rolling, a positive electrode sheet was obtained.

[0098] (3) Preparation of electrolyte: In an argon-filled glove box (moisture content <1 ppm, oxygen content <1 ppm), ethyl propionate, propyl propionate, ethylene carbonate, and propylene carbonate solvents were mixed in a weight ratio of 40:20:20:20 to form a homogeneous solvent. Subsequently, 15% LiPF6, 1.8% 1,3,6-hexanetrionitrile, 2% butadionitrile, and 13% fluoroethylene carbonate were added based on the total weight of the electrolyte to obtain the electrolyte.

[0099] (4) Preparation of negative electrode: Polyurethane and conductive agent (carbon nanotubes and carbon black, with an aspect ratio of 2000) are premixed at a weight ratio of 95:5 to obtain a composite conductive adhesive. The polymer monomer that forms the soft segment structure of polyurethane is 2-methyl-1,5-pentanediol (soft segment molecule), and the polymer monomer that forms the hard segment structure of polyurethane is 1,3-cyclopentane diisocyanate (hard segment molecule). Subsequently, styrene-butadiene rubber, carbon nanotubes (fourth conductive agent), and sodium carboxymethyl cellulose (base coat dispersant) were mixed in an aqueous solvent at a weight ratio of 75:20:5. The mixture was continuously stirred under the action of a stirrer to form a uniform and flowing base coat slurry. The base coat slurry was then coated on both sides of the copper foil and pre-dried to obtain the base coat. Subsequently, graphite, silicon carbon particles (spherical silicon-based material particles), composite conductive adhesive, single-walled carbon nanotubes (third conductive agent, aspect ratio of 2000), sodium carboxymethyl cellulose (dispersant), and lithium polyacrylate (auxiliary agent) were mixed in an aqueous solvent at a weight ratio of 8.1:85:5:0.4:1:0.5. The mixture was continuously stirred under the action of a stirrer to form a uniform, flowing negative electrode slurry. The negative electrode slurry was then coated onto the surface of the base layer and preliminarily dried to obtain the negative electrode active layer. The spherical silicon-based material particles included a first particle with a Dv50 of 10 μm and a second particle with a Dv50 of 4 μm. The particle size of the first particle was smaller than that of the second particle. The particle size of the two particles is as follows: In the spherical silicon-based material particles, the first particle accounts for 80% of the weight, the second particle accounts for 20% of the weight, the weight ratio of the first particle to the second particle is 4:1, and the sphericity of the spherical silicon-based material particles is 0.9. In the negative electrode active layer, the composite conductive adhesive accounts for 5% of the weight (I is 5), the third conductive agent accounts for 0.4% of the weight (K is 0.4), the dispersant accounts for 1% of the weight (J is 1), and the additive accounts for 0.5% of the weight (L is 0.5). [I / (I+J+K+L)]×100%=5 / (5+0.4+1+0.5)×100%=72.5%; Finally, the above-mentioned electrode sheet is thoroughly dried, rolled, and slit to obtain a negative electrode sheet. In a region of 25μm×20μm on the surface of the negative electrode sheet, the number of first particles is 9 (N is 9), the number of second particles is 7 (M is 7), and M / N=7 / 9=0.78.

[0100] Example 1-2 group This set of examples illustrates the effects of changes in the M / N ratio.

[0101] Example I-2a The experiment was carried out in accordance with Example I-1, except that the Dv50 of the first particle was 8 μm and the Dv50 of the second particle was 6.8 μm. In a region of 25 μm × 20 μm on the surface of the negative electrode, the number of the first particle was 17 (N = 17) and the number of the second particle was 1 (M = 1), M / N = 1 / 17 = 0.06, and the sphericity of the spherical silicon-based material particles was 0.8.

[0102] Example I-2b The process is carried out with reference to Example I-1, except that the Dv50 of the first particle is 11 μm and the Dv50 of the second particle is 3 μm. In a region of 25 μm × 20 μm on the surface of the negative electrode, the number of the first particle is 8 (N is 8) and the number of the second particle is 8 (M is 8), M / N = 8 / 8 = 1, and the sphericity of the spherical silicon-based material particles is 1.

[0103] Example 1-3 group This set of examples illustrates the effects of changing the weight ratio of the first and second particles in a spherical silicon-based material particle.

[0104] Example I-3a The experiment was conducted in accordance with Example I-1, except that the Dv50 of the first particle was 8 μm and the Dv50 of the second particle was 5 μm. In the spherical silicon-based material particles, the weight ratio of the first particle was 50% and the weight ratio of the second particle was 50%, and the weight ratio of the first particle to the second particle was 1:1. In the negative electrode active layer, the weight ratio of silicon-carbon particles was 65% and the weight ratio of graphite was 28.1%.

[0105] Example I-3b The experiment was conducted in accordance with Example I-1, except that the Dv50 of the first particle was 10 μm and the Dv50 of the second particle was 3.5 μm. In the spherical silicon-based material particles, the weight percentage of the first particle was 95% and the weight percentage of the second particle was 5%. The weight ratio of the first particle to the second particle was 19:1. In the negative electrode active layer, the weight percentage of silicon-carbon particles was 65% and the weight percentage of graphite was 28.1%.

[0106] Example I-3c The experiment was conducted in accordance with Example I-1, except that the Dv50 of the first particle was 7 μm and the Dv50 of the second particle was 6.8 μm. In the spherical silicon-based material particles, the weight percentage of the first particle was 30% and the weight percentage of the second particle was 70%, and the weight ratio of the first particle to the second particle was 3:7. In the negative electrode active layer, the weight percentage of silicon-carbon particles was 65% and the weight percentage of graphite was 28.1%.

[0107] Example I-3d The experiment was conducted in accordance with Example I-1, except that the Dv50 of the first particle was 12 μm and the Dv50 of the second particle was 3 μm. In the spherical silicon-based material particles, the weight percentage of the first particle was 98% and the weight percentage of the second particle was 2%, with a weight ratio of 49:1. In the negative electrode active layer, the weight percentage of silicon-carbon particles was 65% and the weight percentage of graphite was 28.1%.

[0108] Example 1-4 group This set of examples illustrates the effects of changes in the structure of polyurethane.

[0109] Example I-4a The process was carried out in accordance with Example I-1, except that the polymer monomer forming the polyurethane soft segment structure was 2-methyl-1,5-pentanediol (soft segment molecule), and the polymer monomer forming the polyurethane hard segment structure was hydrogenated toluene diisocyanate (hard segment molecule).

[0110] Example I-4b The process was carried out in accordance with Example I-1, except that the polymer monomer forming the polyurethane soft segment structure was dihydroxy-terminated polyethylene (soft segment molecule), and the polymer monomer forming the polyurethane hard segment structure was hydrogenated toluene diisocyanate (hard segment molecule).

[0111] Example 1-5 group This set of examples illustrates the effects of changes in the aspect ratio of single-walled carbon nanotubes (the third conductive agent).

[0112] Example I-5a The procedure was carried out in accordance with Example I-1, except that the aspect ratio of the single-walled carbon nanotubes (third conductive agent) was 1510.

[0113] Example I-5b The procedure was carried out in accordance with Example I-1, except that the aspect ratio of the single-walled carbon nanotubes (third conductive agent) was 1000.

[0114] Example 1-6 group This set of examples illustrates the effects of changing [I / (I+J+K+L)]×100%.

[0115] Example I-6a The experiment was conducted in accordance with Example I-1, except that the weight percentage of graphite in the negative electrode active layer was changed so that the weight percentage of the composite conductive adhesive in the negative electrode active layer was 1.2% (I = 1.2), the weight percentage of the third conductive agent was 0.4% (K = 0.4), the weight percentage of the dispersant was 0.8% (J = 0.8), and the weight percentage of the additive was 0.2% (L = 0.2). The weight percentage of the additive was calculated as [I / (I+J+K+L)]×100%=1.2 / (1.2+0.4+0.8+0.2)×100%=46%.

[0116] Example I-6b The experiment was carried out in accordance with Example I-1, except that the weight percentage of graphite in the negative electrode active layer was changed so that the weight percentage of the composite conductive adhesive in the negative electrode active layer was 12% (I is 12), the weight percentage of the third conductive agent was 0.4% (K is 0.4), the weight percentage of the dispersant was 0.8% (J is 0.8), and the weight percentage of the additive was 0.2% (L is 0.2). [I / (I+J+K+L)]×100%=12 / (12+0.4+0.8+0.2)×100%=90%.

[0117] Example I-6c The experiment was conducted in accordance with Example I-1, except that the weight percentage of graphite in the negative electrode active layer was changed so that the weight percentage of the composite conductive adhesive in the negative electrode active layer was 0.8% (I is 0.8), the weight percentage of the third conductive agent was 0.4% (K is 0.4), the weight percentage of the dispersant was 0.3% (J is 0.3), and the weight percentage of the additive was 0.2% (L is 0.2). [I / (I+J+K+L)]×100%=0.8 / (0.8+0.4+0.3+0.2)×100%=47%.

[0118] Example I-6d The experiment was conducted in accordance with Example I-1, except that the weight percentage of graphite in the negative electrode active layer was changed so that the weight percentage of the composite conductive adhesive in the negative electrode active layer was 13% (I = 13), the weight percentage of the third conductive agent was 0.4% (K = 0.4), the weight percentage of the dispersant was 1% (J = 1), and the weight percentage of the additive was 0.2% (L = 0.2). Therefore, [I / (I+J+K+L)]×100%=13 / (13+0.4+1+0.2)×100%=89%.

[0119] Example I-6e The experiment was conducted in accordance with Example I-1, except that the weight percentage of graphite in the negative electrode active layer was changed so that the weight percentage of the composite conductive adhesive in the negative electrode active layer was 1% (I = 1), the weight percentage of the third conductive agent was 0.4% (K = 0.4), the weight percentage of the dispersant was 0.8% (J = 0.8), and the weight percentage of the additive was 0.2% (L = 0.2). The weight percentage of the additive was calculated as [I / (I+J+K+L)]×100%=1 / (1+0.4+0.8+0.2)×100%=42%.

[0120] Example I-6f The experiment was conducted in accordance with Example I-1, except that the weight percentage of graphite in the negative electrode active layer was changed so that the weight percentage of the composite conductive adhesive in the negative electrode active layer was 12% (I = 12), the weight percentage of the third conductive agent was 0.4% (K = 0.4), the weight percentage of the dispersant was 0.5% (J = 0.5), and the weight percentage of the additive was 0.2% (L = 0.2). Therefore, [I / (I+J+K+L)]×100%=12 / (12+0.4+0.5+0.2)×100%=92%.

[0121] Example 1-7 group This set of examples illustrates the effects of changes in the weight percentage of styrene-butadiene rubber and / or the weight percentage of the fourth conductive agent in the base coating.

[0122] Example I-7a The process was carried out in accordance with Example I-1, except that the weight percentage of styrene-butadiene rubber in the base coating was 85%, and the weight percentage of the fourth conductive agent was 10%.

[0123] Example I-7b The process was carried out in accordance with Example I-1, except that the weight percentage of styrene-butadiene rubber in the base coating was 65%, and the weight percentage of the fourth conductive agent was 30%.

[0124] Example I-7c The process was carried out in accordance with Example I-1, except that the weight percentage of styrene-butadiene rubber in the base coating was 90%, and the weight percentage of the fourth conductive agent was 5%.

[0125] Example I-7d The process was carried out in accordance with Example I-1, except that the weight percentage of styrene-butadiene rubber in the base coating was 50%, and the weight percentage of the fourth conductive agent was 45%.

[0126] Example 1-8 group This set of examples illustrates the effects of changes in the conductive agent in the composite conductive adhesive.

[0127] Example I-8a The procedure was carried out in accordance with Example I-1, except that the conductive agent in the composite conductive adhesive was carbon nanotubes with an aspect ratio of 2000.

[0128] Example I-8b The procedure was carried out in accordance with Example I-1, except that the conductive agent in the composite conductive adhesive was carbon nanotubes and carbon black, and the aspect ratio of the carbon nanotubes was 1510.

[0129] Example I-8c The procedure was carried out in accordance with Example I-1, except that the conductive agent in the composite conductive adhesive was carbon nanotubes and carbon black, and the aspect ratio of the carbon nanotubes was 1000.

[0130] Example 1-9 This set of examples illustrates the effects of changes in the weight percentage of polyurethane in the composite conductive adhesive and / or the weight percentage of the conductive agent in the composite conductive adhesive.

[0131] Example I-9a The process was carried out in accordance with Example I-1, except that in the composite conductive adhesive, the weight percentage of polyurethane was 94% and the weight percentage of conductive agent was 6%.

[0132] Example I-9b The process was carried out in accordance with Example I-1, except that in the composite conductive adhesive, the weight percentage of polyurethane was 99.5% and the weight percentage of conductive agent was 0.5%.

[0133] Example I-9c The process was carried out in accordance with Example I-1, except that in the composite conductive adhesive, the weight percentage of polyurethane was 90% and the weight percentage of conductive agent was 10%.

[0134] Example I-9d The process was carried out in accordance with Example I-1, except that in the composite conductive adhesive, the weight percentage of polyurethane was 99.7% and the weight percentage of conductive agent was 0.3%.

[0135] Comparative Example 1 The procedure was carried out in accordance with Example I-1, except that styrene-butadiene rubber was used instead of the composite conductive adhesive.

[0136] Comparative Example 2 The procedure was carried out in accordance with Example I-1, except that a single large-diameter silicon carbide particle with a Dv50 of 10 μm was used.

[0137] Comparative Example 3 The procedure was carried out in accordance with Example I-1, except that a single small-diameter silicon carbide particle was used, with a Dv50 of 4 μm.

[0138] Comparative Example 4 The process is carried out in accordance with Example I-1, except that the Dv50 of the first particle is 5μm and the Dv50 of the second particle is 4μm. In a region of 25μm×20μm arbitrarily selected on the surface of the negative electrode, the number of the first particle is 20 (N is 20) and the number of the second particle is 2 (M is 2), M / N=2 / 20=0.1.

[0139] Comparative Example 5 The same procedure was performed as in Example I-1, except that the Dv50 of the first particle was 15 μm and the Dv50 of the second particle was 5 μm. In a region of 25 μm × 20 μm that is optionally selected on the surface of the negative electrode, the number of the first particles was 6 (N was 6) and the number of the second particles was 5 (M was 5), with M / N = 5 / 6 = 0.83.

[0140] Comparative Example 6 The same procedure is followed as in Example I-1, except that the Dv50 of the first particle is 10 μm and the Dv50 of the second particle is 2 μm. In a region of 25 μm × 20 μm that is optionally selected on the surface of the negative electrode, the number of the first particle is 9 (N is 9) and the number of the second particle is 9 (M is 9), with M / N = 9 / 9 = 1.

[0141] Comparative Example 7 The same procedure was carried out as in Example I-1, except that the Dv50 of the first particle was 10 μm and the Dv50 of the second particle was 7.2 μm. In a region of 25 μm × 20 μm that is optionally selected on the surface of the negative electrode, the number of the first particle was 9 (N was 9) and the number of the second particle was 1 (M was 1), with M / N = 1 / 9 = 0.11.

[0142] Comparative Example 8 The same procedure was carried out as in Example I-1, except that the Dv50 of the first particle was 4 μm and the Dv50 of the second particle was 6.8 μm. In a region of 25 μm × 20 μm arbitrarily selected on the surface of the negative electrode, the number of the first particles was 23 (N = 23) and the number of the second particles was 1 (M = 1), with M / N = 1 / 23 = 0.04.

[0143] Comparative Example 9 The same procedure was carried out as in Example I-1, except that the Dv50 of the first particle was 12 μm and the Dv50 of the second particle was 3 μm. In a region of 25 μm × 20 μm arbitrarily selected on the surface of the negative electrode, the number of the first particles was 7 (N was 7) and the number of the second particles was 8 (M was 8), with M / N = 8 / 7 = 1.14.

[0144] Example II-1 The process is carried out in accordance with Example I-1, except that the negative electrode active layer in the negative electrode sheet is a double-layer coating. In step (4) of the preparation of the negative electrode sheet: Silicon carbon particles (second spherical silicon-based material particles, including first particles with a Dv50 of 10 μm and second particles with a Dv50 of 4 μm), second composite conductive adhesive, single-walled carbon nanotubes (third conductive agent with an aspect ratio of 2000), sodium carboxymethyl cellulose (dispersant), and lithium polyacrylate (additive) were mixed in an aqueous solvent at a weight ratio of 87.1:11:0.4:1:0.5. The mixture was continuously stirred in a stirrer to form a uniform and flowing negative electrode slurry. Subsequently, the negative electrode slurry was coated on the surface of the bottom coating on both sides and preliminarily dried to obtain the second negative electrode coating. Subsequently, silicon-carbon particles (first spherical silicon-based material particles, including first particles with a Dv50 of 10 μm and second particles with a Dv50 of 4 μm), first composite conductive adhesive, single-walled carbon nanotubes (third conductive agent with an aspect ratio of 2000), sodium carboxymethyl cellulose (dispersant), and lithium polyacrylate (auxiliary agent) were mixed in an aqueous solvent at a weight ratio of 95.1:3:0.4:1:0.5. The mixture was continuously stirred under the action of a stirrer to form a uniform and flowing negative electrode slurry. Then, the negative electrode slurry was coated on the surface of the second negative electrode coating on both sides and preliminarily dried to obtain the first negative electrode coating. Finally, the double-coated electrode sheets are thoroughly dried, rolled, and slit to obtain the negative electrode sheets. In the first negative electrode coating, the weight percentage of the first spherical silicon-based material particles is 95.1% (a is 95.1%), and in the second negative electrode coating, the weight percentage of the second spherical silicon-based material is 87.1% (c is 87.1%). The weight percentage of the first spherical silicon-based material particles in the first negative electrode coating is greater than that of the second spherical silicon-based material particles in the second negative electrode coating, ac = 95.1% - 87.1% = 8%. The weight percentage of the first composite conductive adhesive in the first negative electrode coating is less than that of the second composite conductive adhesive in the second negative electrode coating.

[0145] Example II-2 group This set of examples illustrates the effects that occur when ac changes.

[0146] Example II-2a The process is carried out with reference to Example II-1, except that the weight percentage of the first spherical silicon-based material particles in the first negative electrode coating is 96.9% (a is 96.9%), the weight percentage of the first composite conductive adhesive in the first negative electrode coating is 1.2%, the weight percentage of the first spherical silicon-based material particles in the second negative electrode coating is 95.9% (c is 95.9%), the weight percentage of the second composite conductive adhesive in the second negative electrode coating is 2.2%, and ac = 96.9% - 95.9% = 1%.

[0147] Example II-2b The process was carried out with reference to Example II-1, except that the weight percentage of the first spherical silicon-based material particles in the first negative electrode coating was 96% (a = 96%), the weight percentage of the first composite conductive adhesive in the first negative electrode coating was 2.1%, the weight percentage of the first spherical silicon-based material particles in the second negative electrode coating was 86.1% (c = 86.1%), and the weight percentage of the second composite conductive adhesive in the second negative electrode coating was 12%, ac = 96% - 86.1% = 9.9%.

[0148] Example II-2c The process is carried out with reference to Example II-1, except that the weight percentage of the first spherical silicon-based material particles in the first negative electrode coating is 96.5% (a is 96.5%), the weight percentage of the first composite conductive adhesive in the first negative electrode coating is 1.6%, the weight percentage of the first spherical silicon-based material particles in the second negative electrode coating is 96% (c is 96%), the weight percentage of the second composite conductive adhesive in the second negative electrode coating is 2.1%, and ac = 96.5% - 96% = 0.5%.

[0149] Example II-2d The process was carried out with reference to Example II-1, except that the weight percentage of the first spherical silicon-based material particles in the first negative electrode coating was 86% (a is 86%), the weight percentage of the first composite conductive adhesive in the first negative electrode coating was 6%, the weight percentage of the dispersant in the first negative electrode coating was 7.1%, the weight percentage of the first spherical silicon-based material particles in the second negative electrode coating was 87.1% (c is 87.1%), the weight percentage of the second composite conductive adhesive in the second negative electrode coating was 11%, and the weight percentage of the first spherical silicon-based material particles in the first negative electrode coating was less than the weight percentage of the second spherical silicon-based material particles in the second negative electrode coating.

[0150] Example II-3 group This set of embodiments is used to illustrate the effects of changes in the weight ratio of the first composite conductive adhesive in the first negative electrode coating and / or the weight ratio of the second composite conductive adhesive in the second negative electrode coating.

[0151] Example II-3a The process is carried out with reference to Example II-1, except that the weight percentage of the first spherical silicon-based material particles in the first negative electrode coating is 92.1% (a is 92.1%), the weight percentage of the first composite conductive adhesive in the first negative electrode coating is 6%, the weight percentage of the first spherical silicon-based material particles in the second negative electrode coating is 86.1% (c is 86.1%), the weight percentage of the second composite conductive adhesive in the second negative electrode coating is 12%, and ac = 92.1% - 86.1% = 6%.

[0152] Example II-3b The process is carried out with reference to Example II-1, except that the weight percentage of the first spherical silicon-based material particles in the first negative electrode coating is 97% (a is 97%), the weight percentage of the first composite conductive adhesive in the first negative electrode coating is 0.5%, the weight percentage of the dispersant in the first negative electrode coating is 1.6%, the weight percentage of the first spherical silicon-based material particles in the second negative electrode coating is 96% (c is 96%), the weight percentage of the second composite conductive adhesive in the second negative electrode coating is 1.5%, the weight percentage of the dispersant in the second negative electrode coating is 1.6%, and ac = 97% - 96% = 1%.

[0153] Example II-3c The process is carried out with reference to Example II-1, except that the weight percentage of the first spherical silicon-based material particles in the first negative electrode coating is 90.1% (a is 90.1%), the weight percentage of the first composite conductive adhesive in the first negative electrode coating is 8%, the weight percentage of the first spherical silicon-based material particles in the second negative electrode coating is 85.1% (c is 85.1%), the weight percentage of the second composite conductive adhesive in the second negative electrode coating is 13%, and ac = 90.1% - 85.1% = 5%.

[0154] Example II-3d The process was carried out with reference to Example II-1, except that the weight percentage of the first spherical silicon-based material particles in the first negative electrode coating was 95.1% (a is 95.1%), the weight percentage of the first composite conductive adhesive in the first negative electrode coating was 3%, the weight percentage of the first spherical silicon-based material particles in the second negative electrode coating was 94% (c is 94%), the weight percentage of the second composite conductive adhesive in the second negative electrode coating was 2%, the weight percentage of the dispersant in the second negative electrode coating was 3.1%, and ac = 95.1% - 94% = 1.1%. The weight percentage of the first composite conductive adhesive in the first negative electrode coating was greater than the weight percentage of the second composite conductive adhesive in the second negative electrode coating.

[0155] Test case The batteries prepared in the examples and comparative examples were subjected to the following performance tests, and the test results are shown in Table 1: (1) Capacity retention and thickness expansion rate during 25℃ cycling: At 25℃±2℃, the battery was charged at a constant current of 1C to the upper limit voltage of 4.5V, then charged at a constant voltage to 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.7C to 3V, left to stand for 5 minutes. The initial discharge capacity was recorded as C0, and the battery thickness was measured as h0. The cycle was as follows: charged at a constant current of 1C to the upper limit voltage of 4.5V, then charged at a constant voltage to 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.7C to 3V. After 500 cycles, the discharge capacity was recorded as C1, and the battery thickness was measured as h1. The capacity retention rate was (C1 / C0)×100%, and the thickness expansion rate was (h1-h0) / h0×100%. The results are recorded in Table 1.

[0156] (2) Ratio performance: The lithium-ion battery was left to stand at 25±2℃ for 60 minutes, discharged at 0.5C to 2.0V, left to stand for 5 minutes, charged at 4C constant current to the upper limit voltage of 4.5V, with a cutoff current of 0.05C, left to stand for 5 minutes, discharged at 2.5C constant current to 2.0V, and left to stand for 10 minutes. This discharge capacity is recorded as Q0. Then, it was charged at 4C constant current to the upper limit voltage of 4.5V, with a cutoff current of 0.05C, left to stand for 5 minutes, and then discharged at 2.5C constant current to 2.0V; left to stand for 10 minutes. This discharge capacity is recorded as Q1. Rate performance = (Q1 / Q0) × 100%.

[0157] (3) Volumetric energy density: The battery was left to stand for 1 hour at (25±2)℃. It was then charged at a constant current of 0.5C to 4.5V, followed by constant voltage charging at 4.5V to a current of 0.05C, and left to stand for 10 minutes. Next, it was discharged at a constant current of 0.2C to 3.0V and left to stand for 10 minutes. The discharge capacity was recorded as C, the average discharge plateau voltage as V, and the thickness, length, and width of the lithium-ion battery were measured as X, Y, and Z, respectively. The volumetric energy density was calculated as (C×V) / (X×Y×Z).

[0158] Table 1 As can be seen from Table 1, by comparing the comparative example and the embodiment, the embodiment shows improved room temperature cycling capacity retention, improved rate performance, reduced thickness expansion rate, and improved volumetric energy density. This indicates that by introducing composite conductive adhesive and two types of spherical silicon-based material particles with different particle sizes into the negative electrode active layer, and controlling the ratio of the number of the first particles to the number of the second particles in a region of 25μm×20μm on the surface of the negative electrode sheet, the stability of the bonding network and conductive network of the negative electrode sheet is improved, thereby reducing the battery expansion rate and improving the battery rate performance, cycle stability, and volumetric energy density.

[0159] 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 negative electrode sheet, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on at least one side of the negative electrode current collector. The negative electrode active layer includes spherical silicon-based material particles and a composite conductive adhesive. The composite conductive adhesive includes polyurethane and a conductive agent. The spherical silicon-based material particles include a first particle and a second particle, wherein the particle size of the first particle is larger than that of the second particle, the Dv50 of the first particle is 7μm-12μm, and the Dv50 of the second particle is 3μm-6.8μm. Within an area of ​​25μm × 20μm on the surface of the negative electrode, the negative electrode satisfies the following relationship: 0.05 ≤ M / N ≤ 1, where N is the number of the first particles and M is the number of the second particles.

2. The negative electrode sheet according to claim 1, wherein, In the spherical silicon-based material particles, the weight percentage of the first particle is 50%-95%; And / or, in the spherical silicon-based material particles, the weight percentage of the second particle is 50%-5%; And / or, the areal density of the negative electrode active layer is less than or equal to 10 mg / cm³. 2 ; And / or, the weight percentage of silicon in the negative electrode active layer is 2%-50%; And / or, the sphericity of the spherical silicon-based material particles is 0.8-1.

3. The negative electrode sheet according to claim 1, wherein, The polyurethane comprises a hard segment structure and a soft segment structure. The polymer monomers forming the hard segment structure are hard segment molecules, and the hard segment molecules include the structure shown in Formula I. The polymer monomers forming the soft segment structure are soft segment molecules, and the soft segment molecules include the structure shown in Formula II. OCN-R n1 -NCO (Formula I), Where n1≥1, R is selected from M 1 Metacarbocyclic structure, M 1 ≥5; (Formula II) Wherein, n3 = 5-200, n4 = 0-40, and the side chain end group b is selected from at least one of hydrogen atom, methyl, cyano, and amide; Preferably, in the polyurethane, the weight percentage of the hard segment structure is 20%-85%, and the weight percentage of the soft segment structure is 5%-50%. Preferably, the hard segment molecule includes at least one of 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, norbornene diisocyanate, adamantane diisocyanate, and hydrogenated toluene diisocyanate, and the soft segment molecule includes at least one of 2-methyl-1,5-pentanediol, dihydroxy-terminated polyethylene, and dihydroxy-terminated hydrogenated polybutadiene.

4. The negative electrode sheet according to claim 1, wherein, In the spherical silicon-based material particles, the weight ratio of the first particle to the second particle is (1-19):1; And / or, the conductive agent includes at least one of carbon nanotubes, carbon black, and graphene, preferably, the aspect ratio of the carbon nanotubes in the conductive agent is greater than 1500; And / or, in the composite conductive adhesive, the polyurethane accounts for 94%-99.5% by weight, and the conductive agent accounts for 0.5%-6% by weight; And / or, the composite conductive adhesive is formed by premixing polyurethane and a conductive agent; And / or, in the negative electrode active layer, the weight percentage of the composite conductive adhesive is 1%-12%.

5. The negative electrode sheet according to claim 1, wherein, The negative electrode active layer further includes a third conductive agent, a dispersant, and an additive. The third conductive agent includes single-walled carbon nanotubes. The dispersant includes at least one of lithium carboxymethyl cellulose, modified lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, and modified sodium carboxymethyl cellulose. The additive includes at least one of lithium polyacrylate, modified lithium polyacrylate, sodium polyacrylate, modified sodium polyacrylate, styrene-butadiene rubber, and modified styrene-butadiene rubber. Preferably, the negative electrode sheet satisfies the following relationship: 45%≤[I / (I+J+K+L)]×100%≤90%, where I is the weight percentage of the composite conductive adhesive in the negative electrode active layer (%), J is the weight percentage of the dispersant in the negative electrode active layer (%), K is the weight percentage of the third conductive agent in the negative electrode active layer (%), and L is the weight percentage of the additives in the negative electrode active layer (%). Preferably, the aspect ratio of the single-walled carbon nanotube is greater than 1500.

6. The negative electrode sheet according to claim 1, wherein, The negative electrode sheet includes a base coating layer located between the negative electrode current collector and the negative electrode active layer. The base coating layer includes styrene-butadiene rubber and a fourth conductive agent, wherein the fourth conductive agent includes at least one of carbon nanotubes and carbon black. Preferably, in the base coating, the styrene-butadiene rubber accounts for more than 60% by weight; Preferably, the fourth conductive agent accounts for 10%-30% of the weight of the base coating.

7. The negative electrode sheet according to any one of claims 1-6, wherein, The negative electrode active layer includes a first negative electrode coating and a second negative electrode coating. The second negative electrode coating is located between the negative electrode current collector and the first negative electrode coating. The first negative electrode coating includes a first spherical silicon-based material particle and a first composite conductive adhesive. The second negative electrode coating includes a second spherical silicon-based material particle and a second composite conductive adhesive. Preferably, the weight percentage of the first spherical silicon-based material particles in the first negative electrode coating is greater than the weight percentage of the second spherical silicon-based material particles in the second negative electrode coating; More preferably, the negative electrode sheet satisfies the following relationship: ac≥1%, where a is the weight percentage of the first spherical silicon-based material particles in the first negative electrode coating, and c is the weight percentage of the second spherical silicon-based material particles in the second negative electrode coating.

8. The negative electrode sheet according to claim 7, wherein, The areal density of the first negative electrode coating is 1 mg / cm³. 2 -5mg / cm 2 ; And / or, the areal density of the second negative electrode coating is 2 mg / cm³. 2 -5mg / cm 2 ; And / or, the weight percentage of the first composite conductive adhesive in the first negative electrode coating is less than the weight percentage of the second composite conductive adhesive in the second negative electrode coating; And / or, in the first negative electrode coating, the weight percentage of the first composite conductive adhesive is 1%-6%; And / or, in the second negative electrode coating, the weight percentage of the second composite conductive adhesive is 2%-12%.

9. The negative electrode sheet according to claim 7, wherein, The first composite conductive adhesive includes a first polyurethane and a first conductive agent, and the second composite conductive adhesive includes a second polyurethane and a second conductive agent. The first conductive agent and the second conductive agent each independently include at least one of carbon nanotubes, carbon black, and graphene. Preferably, in the first composite conductive adhesive, the weight percentage of the first polyurethane is 94%-99.5%, and the weight percentage of the first conductive agent is 0.5%-6%. Preferably, in the second composite conductive adhesive, the weight percentage of the second polyurethane is 94%-99.5%, and the weight percentage of the second conductive agent is 0.5%-6%.

10. A battery, characterized in that, The battery includes the negative electrode sheet according to any one of claims 1-9.

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