Battery electrode with high-gradient thin coating, battery and electric device

Abstract

The invention discloses a battery electrode with a high-gradient thin coating, a battery and an electric device, and belongs to the technical field of battery materials. The battery electrode comprises a high-gradient thin coating as well as a first active material layer and a second active material layer which are positioned on two sides of the high-gradient thin coating, the high-gradient thin coating contains the following components in percentage by mass: 25%-67% of a conductive agent, 20%-50% of an adhesive and 0%-25% of a large-particle filler; wherein the large-particle filler is used for improving the interface roughness and the compound force and enhancing the machining performance of the pole piece. The high-gradient thin coating in the battery electrode can restrain pole piece cracking and impedance increase after charging and discharging circulation, and therefore the high-temperature storage performance and the rate performance of the battery can be improved.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to a battery electrode with a high gradient thin coating, as well as a battery and an electrical device. Background Technology

[0002] Battery electrode cracking not only affects production line yield and stable shipments, but also seriously impacts battery performance and safety, leading to issues such as capacity decay, increased internal resistance, and internal short-circuit failure. Currently, battery manufacturers often employ thin or thick coating solutions to meet performance requirements in pursuit of high charge / discharge rates or to increase energy density and reduce costs. However, their internal structure is insufficient to support such demanding electrical performance outputs. Under repeated charge / discharge cycles or high / low temperature shocks, batteries are highly susceptible to developing micro-cracks in their electrode structure. These cracks grow and expand, leading to electrical performance degradation or safety issues.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a battery electrode with a high-gradient thin coating, as well as a battery and an electrical device. The high-gradient thin coating of the battery electrode contains a high concentration of binder, which allows it to penetrate the electrode like a mesh, absorbing internal stress and preventing the expansion of local cracks. The high-gradient thin coating also contains a high concentration of conductive agent, which allows it to efficiently collect microcurrents like a composite current collector, carrying away local heat and improving rate performance. At the same time, the optional large-particle filler in the high-gradient thin coating allows its edges to be embedded and anchored into the active material layers on both sides like serrations, which can significantly improve electrode processing problems such as electrode cracking, debonding, and powder shedding.

[0005] This invention can be implemented as follows: In a first aspect, the present invention provides a battery electrode with a high gradient thin coating, the battery electrode comprising a high gradient thin coating and a first active material layer and a second active material layer located on both sides of the high gradient thin coating. By mass percentage, the high gradient thin coating contains 25% to 67% conductive agent, 20% to 50% binder, and 0% to 25% large particle filler; among which, the large particle filler is used to improve the overall mechanical strength and electrical performance of the electrode.

[0006] In an optional embodiment, the high gradient thin coating layer is embedded and interlocked with the first active material layer and the second active material layer at the interface.

[0007] In an optional implementation, when large particle fillers are not used, the thickness of the high gradient thin coating is 10 nm to 1800 nm. Alternatively, the thickness of both the first active material layer and the second active material layer shall not be less than 10 nm.

[0008] In an optional implementation, the high-gradient thin coating is no more than 1000 nm away from the overall golden ratio point of the battery electrode.

[0009] In an optional embodiment, the adhesive is selected from at least one of PVDF, PTFE, cellulose derivatives, alginate compounds, and PAA compounds.

[0010] In an optional embodiment, the conductive agent is selected from at least one of carbon black, Ketjen black, acetylene black, VGCF, carbon nanotubes, carbon fibers, graphene, natural graphite, artificial graphite, aluminum, and copper. In an optional embodiment, the conductive agent contains carbon nanotubes.

[0011] In an optional embodiment, the D of the large particle packing 50 The wavelength range is 300nm to 20μm. And / or, large particle fillers include at least one of active materials, lithium supplements, and inactive materials.

[0012] In an optional embodiment, the high gradient thin coating also contains 0% to 3% of a dispersant.

[0013] In an optional embodiment, the dispersant includes at least one of maleic acid with C12-22 alpha-olefin copolymer and maleic anhydride-styrene copolymer grafted with ethylene oxide-polyoxypropylene (EO-PO) block copolymer.

[0014] In an optional implementation, the dispersant accounts for no more than 0.3% of the mass of the high gradient thin coating.

[0015] In a second aspect, the present invention provides a method for preparing a battery electrode as described in any of the foregoing embodiments, comprising the following steps: preparing a first active material layer on the surface of the electrode; coating a slurry for preparing a high gradient thin coating onto the surface of the first active material layer and drying it to obtain an electrode with a high gradient thin coating; and then preparing a second active material layer on the other side of the high gradient thin coating.

[0016] Thirdly, the present invention provides a battery comprising the battery electrodes of any of the foregoing embodiments.

[0017] Fourthly, the present invention provides an electrical device comprising the battery of the aforementioned embodiments.

[0018] The beneficial effects of this invention include: This invention achieves the same or better performance by implementing an ultra-thin, high-gradient thin coating on the electrode, without increasing the overall amount of active material, conductive agent, and binder used in the electrode. This means that the actual material expenditure can even be reduced, as the invention implements a concentration gradient rather than adding additional coating material. Furthermore, by implementing a high-gradient thin coating containing large-particle fillers on the electrode, its stable basic structure effectively supports higher coating weight, resulting in higher electrode thickness and battery energy density, thus achieving product upgrades. Finally, by implementing a high-gradient thin coating with localized high concentrations of high-performance carbon nanotubes or graphene on the electrode, it acts as a conductive framework, effectively supporting higher charge-discharge rates and suppressing electrode cracking and fissure growth, providing higher factory yield, better safety, and better cycle performance.

[0019] The electrical device provided by this invention, which has electrodes with a high gradient thin coating, does not require additional semiconductor or vacuum equipment investment and can be stably produced even in high dew point environments. With reasonable configuration, it can achieve the practical effect of optimization and upgrading of old production lines in battery factories. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a physical image of the positive electrode sheet in Embodiment 1 of the present invention; Figure 2 This is a surface SEM image of the high gradient thin coating of the positive electrode in Embodiment 2 of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0023] The following is a detailed description of the battery electrode with a high gradient thin coating, the battery, and the power-consuming device provided by the present invention.

[0024] The present invention provides a battery electrode with a high gradient thin coating, the battery electrode comprising a high gradient thin coating and a first active material layer and a second active material layer located on both sides of the high gradient thin coating.

[0025] By mass percentage, the high-gradient thin coating contains 25%–67% conductive agent, 20%–50% binder, and 0%–25% large-particle filler. That is, compared to ordinary electrodes without a high-gradient thin coating, the electrode sheet containing the high-gradient thin coating in this invention contains a high concentration gradient of conductive agent and binder. It can also be understood that, compared to the first active material layer and the second active material layer, the high-gradient thin coating contains a higher content of conductive agent and binder.

[0026] The high-concentration binder contained in the high-gradient thin coating of the battery electrode makes it permeate the electrode like a mesh, which can absorb internal stress and prevent local cracks from expanding; the high-concentration conductive agent contained in the high-gradient thin coating makes it collect microcurrents efficiently like a composite current collector, which can carry away local heat and improve rate performance.

[0027] The amount of conductive agent contained in the high gradient thin coating can be 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 67%, or other values ​​within the range of 25% to 67%. If the content of conductive agent in the high gradient thin coating is less than 25%, it is difficult to effectively collect microcurrents; if the content of conductive agent in the high gradient thin coating is greater than 67%, it is easy to cause the slurry viscosity to be too high, and the coating process cannot be implemented smoothly.

[0028] The adhesives mentioned above may be selected from at least one of PVDF, PTFE, cellulose derivatives, alginate compounds and PAA compounds.

[0029] The amount of binder in a high-gradient thin coating can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, or other values ​​within the range of 20% to 50%. If the binder content in the high-gradient thin coating is less than 20%, it is difficult to effectively resist the internal stress of the electrode; if the binder content in the high-gradient thin coating is more than 50%, because the binder is non-conductive, it can easily lead to a decrease in the overall conductivity of the electrode, affecting the performance of the battery.

[0030] The conductive agent described above may be selected from at least one of carbon black, Ketjen black, acetylene black, VGCF, carbon nanotubes, carbon fibers, graphene, natural graphite, artificial graphite, aluminum, and copper; preferably, it contains at least carbon nanotubes.

[0031] The large-particle filler in the high-gradient thin coating of this invention is used to improve the overall mechanical strength and electrical properties of the electrode, and can significantly increase the thickness and interface roughness of the high-gradient thin coating. The content of large-particle filler in the high-gradient thin coating can be 0%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, or 25%, or other values ​​within the range of 0% to 25%. That is, the high-gradient thin coating may or may not contain large-particle filler.

[0032] The presence of large-particle fillers in high-gradient thin coatings allows their edges to embed and anchor the active material layers on both sides, significantly improving electrode processing issues such as cracking, debonding, and powdering. However, if the content of large-particle fillers in a high-gradient thin coating exceeds 25%, it can easily lead to an excessively thick coating, loose interface, and poor bonding, affecting resistance and overall stability.

[0033] In some alternative embodiments, the high-gradient thin coating contains large-particle fillers with a narrow uniform particle size distribution, whose D 50 The particle size ranges from 300nm to 20μm, and can be 300nm, 500nm, 1μm, 5μm, 10μm, 15μm, or 20μm, etc. If the D of the large particle filler... 50 For particles smaller than 300nm, the improvement in surface roughness is limited, the bonding area with the active material layer decreases, and the bonding force weakens; if the D of large particle fillers... 50 For particles larger than 20 μm, the total number of particles decreases due to the limited amount added, thus limiting the improvement on the overall interface roughness.

[0034] In some alternative embodiments, the large particle filler may include at least one of an active material, a lithium supplement, and an inactive material. The active material used in the large particle filler (if any) may be the same as or different from the active material used in the electrode in which it is located.

[0035] In some optional embodiments, the high gradient thin coating may also contain 0% to 3% (e.g., 0%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, or 3%) of dispersant. That is, the high gradient thin coating may or may not contain a dispersant. In some preferred embodiments, the mass percentage of the dispersant in the high gradient thin coating does not exceed 0.3%.

[0036] The dispersant described above may include at least one of maleic acid-C12-22 alpha-olefin copolymer and maleic anhydride-styrene copolymer grafted onto ethylene oxide-polyoxypropylene (EO-PO) block copolymer. In the maleic acid-C12-22 alpha-olefin copolymer, the hydrophobic long chain is the backbone, and the maleic acid carboxyl groups are serrated. The maleic anhydride-styrene copolymer grafted onto ethylene oxide-polyoxypropylene (EO-PO) block copolymer also has a typical comb-like topology, making it a highly efficient active ingredient designed for complex dispersion systems. In some preferred embodiments, the dispersant includes at least maleic acid-C12-22 alpha-olefin copolymer.

[0037] In some alternative embodiments, the high-gradient thin coating layer is embedded and interlocked with the first active material layer and the second active material layer at the interface.

[0038] In some preferred embodiments, the high gradient thin coating is located at or near the overall golden section point of the battery electrode, such as within ±1 μm of the overall golden section point of the battery electrode.

[0039] In some alternative implementations, when large particle fillers are not used, the thickness of the high gradient thin coating can be 10 nm to 1800 nm, such as 10 nm, 100 nm, 200 nm, 500 nm, 800 nm, 1000 nm, 1200 nm, 1500 nm or 1800 nm, or other values ​​in the range of 10 nm to 1800 nm.

[0040] If large particle fillers are not used, the thickness of the high gradient thin coating is less than 10nm, which can easily lead to unevenness of the conductive agent and binder; if large particle fillers are not used, the thickness of the high gradient thin coating exceeds 1800nm, which results in a thicker coating, wasting materials and hindering cost reduction.

[0041] The thickness of both the first and second active material layers is not less than 10 nm, such as 10 nm, 20 nm, 1 μm, 10 μm or 50 μm.

[0042] In some alternative implementations, the high-energy-density thick-coated electrode can be a multilayered composite similar to plywood, with active material layers on both sides of the high-gradient thin coating layer, and n high-gradient thin coating layers separated by n+1 active material layers.

[0043] Accordingly, the present invention also provides a method for preparing the above-mentioned battery electrode, comprising the following steps: preparing a first active material layer on the surface of the electrode; coating a slurry for preparing a high gradient thin coating onto the surface of the first active material layer and drying it to obtain an electrode with a high gradient thin coating; and then preparing a second active material layer on the other side of the high gradient thin coating.

[0044] For example, firstly, a first active material layer is coated on the electrode; then, a dispersant, a conductive agent, and a binder are mixed with a solvent in a certain proportion, and the mixture is ground and dispersed using a high-pressure homogenizer or a sand mill to obtain a slurry; large particle fillers are added to the slurry and stirred evenly to obtain a high-gradient thin-coating slurry; the high-gradient thin-coating slurry is coated on the outside of the first active material layer and dried to obtain an electrode with a high-gradient thin-coating; then, a second active material coating is applied to obtain an electrode containing a first active material layer, a high-gradient thin-coating, and a second active material layer.

[0045] The coating method for the aforementioned high gradient thin-coating paste can be gravure printing, extrusion coating, or transfer coating, etc. The solvent in the high gradient thin-coating paste can be deionized water, NMP, or commonly used mixed solvents, etc., without any special restrictions.

[0046] In some alternative embodiments, the first active material layer, the high gradient thin coating layer, and the second active material layer may use the same type of active material, and the large particle filler in the high gradient thin coating layer may also be the same type of active material, such as lithium iron phosphate or high nickel ternary materials, etc., without any special restrictions.

[0047] In addition, the present invention also provides a battery including the above-described battery electrodes, which can have superior discharge rate, cycle life and safety performance.

[0048] The battery electrodes described above can be positive electrodes, negative electrodes, or both positive and negative electrodes.

[0049] The batteries mentioned above can be lithium-ion batteries, sodium-ion batteries, or solid-state batteries, and no special restrictions are imposed here.

[0050] In addition, the present invention also provides an electrical device comprising the aforementioned battery.

[0051] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0052] Example 1 This embodiment provides a battery, the preparation method of which includes: (1) Preparation of positive electrode sheet S1: First coating of positive electrode active material slurry.

[0053] Lithium iron phosphate material (D) 50Particle size of 0.9 μm, conductive agent Super-P, binder PVDF are mixed with solvent N-methylpyrrolidone in a weight ratio of 97:1:2 to obtain a positive electrode active material slurry with a solid content of 68%. The positive electrode active material slurry is uniformly coated on the front and back surfaces of an aluminum foil (positive electrode current collector) with a thickness of 12 μm. The first positive electrode active material layer is obtained by drying. The thickness of the first positive electrode active material layer on both sides is 180 μm.

[0054] S2: Prepare and apply a high gradient thin coating slurry for the positive electrode.

[0055] Single-walled carbon nanotubes, multi-walled carbon nanotubes, VGCF, maleic acid, C12-22 alpha-olefin copolymer, and PAA were mixed in a mass ratio of 1:1:1:0.1:1.5. Deionized water was added as a solvent, and the mixture was stirred until homogeneous to obtain a mixture with a solid content of 2 wt%. The mixture was then milled in a sand mill with 1 μm zirconium beads for 10 h to obtain a high gradient thin coating slurry for the positive electrode. The high gradient thin coating slurry was coated on the surface of two first positive electrode active material layers and baked to obtain a high gradient thin coating for the positive electrode. The thinnest part of the two high gradient thin coatings was 30 nm, and the thickest part was 120 nm.

[0056] S3: Recoating of the positive electrode active material slurry.

[0057] The same positive electrode active material slurry as S1 was uniformly coated on the surface of two positive electrode high gradient thin coatings, and the second positive electrode active material layer was obtained by drying. The thickness of the second positive electrode active material layer on both sides was 180μm.

[0058] That is, the structure of the positive electrode is: second positive electrode active material layer - positive electrode high gradient thin coating layer - first positive electrode active material layer - aluminum foil - first positive electrode active material layer - positive electrode high gradient thin coating layer - second positive electrode active material layer.

[0059] The actual image of the positive electrode is as follows: Figure 1 As shown, by Figure 1 It can be seen that the surface of the positive electrode is flat and the coating is free of cracks.

[0060] (2) Preparation of negative electrode sheet S4: First coating of negative electrode active material slurry.

[0061] Artificial graphite, styrene-butadiene rubber (SBR) binder, and sodium carboxymethyl cellulose (CMC-Na) thickener were dissolved in deionized water at a weight ratio of 97:2:1 and mixed evenly to prepare a negative electrode active material slurry. The negative electrode active material slurry was uniformly coated on the front and back surfaces of a copper foil (negative electrode current collector) with a thickness of 8 μm. The first negative electrode active material layer was obtained by drying, and the thickness of the first negative electrode active material layer on both sides was 120 μm.

[0062] S5: Prepare and apply a high gradient thin coating slurry for the negative electrode.

[0063] Single-walled carbon nanotubes, multi-walled carbon nanotubes, VGCF, maleic acid, C12-22 alpha-olefin copolymer, and PAA were mixed in a mass ratio of 1:1:1:0.1:1.5. Deionized water was added as a solvent, and the mixture was stirred until homogeneous to obtain a mixture with a solid content of 1.5 wt%. The mixture was then milled in a sand mill with 1 μm zirconium beads for 10 h to obtain a high gradient thin coating slurry for the negative electrode. The high gradient thin coating slurry was coated on the surface of two first negative electrode active material layers and baked to obtain a high gradient thin coating for the negative electrode. The thinnest part of the two high gradient thin coatings was 20 nm, and the thickest part was 80 nm.

[0064] S6: The negative electrode active material slurry is coated again.

[0065] The same negative electrode active material slurry as S4 was uniformly coated on the surface of two negative electrode high gradient thin coatings, and the second negative electrode active material layer was obtained by drying. The thickness of the second negative electrode active material layer on both sides was 120 μm.

[0066] That is, the structure of the negative electrode sheet is: second negative electrode active material layer - negative electrode high gradient thin coating layer - first negative electrode active material layer - copper foil - first negative electrode active material layer - negative electrode high gradient thin coating layer - second negative electrode active material layer.

[0067] (3) Battery preparation The above-mentioned positive electrode, separator, and negative electrode are used to prepare a pouch cell.

[0068] Example 2 The difference between this embodiment and embodiment 1 is that in S2, the solvent used is NMP, the adhesive is adjusted to PVDF, and the thickness of the high gradient thin coating on one side is about 150nm (the thinnest part is about 100nm and the thickest part is about 240nm).

[0069] The SEM image of the high gradient thin coating of the positive electrode in this embodiment is as follows: Figure 2 As shown, by Figure 2 It can be seen that in this high gradient thin coating of the positive electrode, the interfacial carbon nanotubes are networked and the PVDF binder is agglomerated, thus providing a large contact surface and bonding force.

[0070] Example 3 The difference between this embodiment and Embodiment 1 is that in S2, after grinding with a sand mill, D is added to the slurry. 50 Lithium iron phosphate material with a particle size of 1.4 μm was mixed evenly to obtain a high gradient thin coating slurry with a solid content of 2.3 wt%. The high gradient thin coating slurry was coated on the surface of two first positive electrode active material layers and baked to obtain a high gradient thin coating. The thinnest part of the two high gradient thin coatings is about 65 nm.

[0071] That is, in this embodiment, the mass of the large particle filler contained in the high gradient thin coating of the positive electrode is 13.0%.

[0072] Example 4 The difference between this embodiment and embodiment 3 is that in S5, after sand milling, D is added to the slurry. 50 Natural graphite with a particle size of 10 μm was mixed evenly to obtain a negative electrode high gradient thin coating slurry with a solid content of 1.8 wt%. The negative electrode high gradient thin coating slurry was coated on the surface of two first negative electrode active material layers and baked to obtain a negative electrode high gradient thin coating. The thinnest part of the two negative electrode high gradient thin coatings is about 55 nm.

[0073] That is, in this embodiment, the mass of large particle filler contained in the high gradient thin coating of the negative electrode is 16.7%.

[0074] Example 5 The difference between this embodiment and Embodiment 1 is that in S5, after sand milling, D is added to the slurry. 50 Natural graphite with a particle size of 10 μm was mixed evenly to obtain a negative electrode high gradient thin coating slurry with a solid content of 1.8 wt%. The negative electrode high gradient thin coating slurry was coated on the surface of two first negative electrode active material layers and baked to obtain a negative electrode high gradient thin coating. The thinnest part of the two negative electrode high gradient thin coatings is about 55 nm.

[0075] That is, in this embodiment, the mass of large particle filler contained in the high gradient thin coating of the negative electrode is 16.7%.

[0076] Example 6 The difference between this embodiment and Embodiment 1 is that in S2, single-walled carbon nanotubes, multi-walled carbon nanotubes, maleic anhydride-styrene copolymer grafted polyoxyethylene-polyoxypropylene (EO-PO) block copolymer and PAA are mixed in a mass ratio of 1.5:1.5:0.1:1.5.

[0077] Example 7 The difference between this embodiment and Embodiment 1 is that in S2, after grinding with a sand mill, D is added to the slurry. 50 Lithium iron phosphate material with a particle size of 1.4 μm was mixed evenly to obtain a high gradient thin coating slurry with a solid content of 2.1 wt%. The high gradient thin coating slurry was coated on the surface of two first positive electrode active material layers and baked to obtain a high gradient thin coating. The thinnest part of the two high gradient thin coatings is about 35 nm.

[0078] That is, in this embodiment, the mass of the large particle filler contained in the high gradient thin coating of the positive electrode is 4.8%.

[0079] Example 8 The difference between this embodiment and Embodiment 1 is that in S2, after grinding with a sand mill, D is added to the slurry. 50 Lithium iron phosphate material with a particle size of 0.7 μm was mixed evenly to obtain a high gradient thin coating slurry with a solid content of 2.5 wt%. The high gradient thin coating slurry was coated on the surface of two first positive electrode active material layers and baked to obtain a high gradient thin coating. The thinnest part of the two high gradient thin coatings is about 85 nm.

[0080] That is, in this embodiment, the mass of the large particle filler contained in the high gradient thin coating of the positive electrode is 20.0%.

[0081] Example 9 The difference between this embodiment and Embodiment 1 is that in S5, after grinding with a sand mill, D is added to the slurry. 50 Natural graphite with a particle size of 18 μm was mixed evenly to obtain a negative electrode high gradient thin coating slurry with a solid content of 2 wt%. The negative electrode high gradient thin coating slurry was coated on the surface of two first negative electrode active material layers and baked to obtain a negative electrode high gradient thin coating. The thinnest part of the two negative electrode high gradient thin coatings is about 60 nm.

[0082] That is, in this embodiment, the mass of large particle filler contained in the high gradient thin coating of the negative electrode is 25.0%.

[0083] Example 10 The difference between this embodiment and Embodiment 1 is that in S5, after grinding with a sand mill, D is added to the slurry. 50 Natural graphite with a particle size of 10 μm was mixed evenly to obtain a negative electrode high gradient thin coating slurry with a solid content of 2 wt%. The negative electrode high gradient thin coating slurry was coated on the surface of two first negative electrode active material layers and baked to obtain a negative electrode high gradient thin coating. The thinnest part of the two negative electrode high gradient thin coatings is about 60 nm.

[0084] That is, in this embodiment, the mass of large particle filler contained in the high gradient thin coating of the negative electrode is 25.0%.

[0085] Example 11 The difference between this embodiment and Embodiment 1 is that in S1, the thickness of both first positive electrode active material layers is 280 μm. In S3, the thickness of both second positive electrode active material layers is 80 μm.

[0086] Example 12 The difference between this embodiment and Embodiment 1 is that in S1, the thickness of both first positive electrode active material layers is 80 μm. In S3, the thickness of both second positive electrode active material layers is 280 μm.

[0087] Example 13 The difference between this embodiment and Embodiment 1 is that in S4, the thickness of both first negative electrode active material layers is 180 μm. In S6, the thickness of both second negative electrode active material layers is 60 μm.

[0088] Example 14 The difference between this embodiment and Embodiment 1 is that in S4, the thickness of both first negative electrode active material layers is 60 μm. In S6, the thickness of both second negative electrode active material layers is 180 μm.

[0089] Example 15 The difference between this embodiment and Embodiment 1 is that the positive electrode has no high gradient thin coating, while the negative electrode has a high gradient thin coating, that is, there is no S2.

[0090] Example 16 The difference between this embodiment and Embodiment 1 is that the positive electrode has a high gradient thin coating, while the negative electrode does not have a high gradient thin coating, that is, it does not have S5.

[0091] Comparative Example 1 The difference between this comparative example and Example 1 is that neither the positive nor negative electrode has a high gradient thin coating, that is, neither S2 nor S5.

[0092] Comparative Example 2 The difference between this comparative example and Example 1 is that S2 is present but S5 is absent; and in S2, the amount of conductive agent (single-walled carbon nanotubes, multi-walled carbon nanotubes, VGCF) is reduced to 1 / 4 of the original amount.

[0093] Comparative Example 3 The difference between this comparative example and Example 1 is that S2 is present but S5 is absent; and in S2, the amount of adhesive (PAA) is reduced to 1 / 4 of the original amount.

[0094] Comparative Example 4 The difference between this comparative example and Example 1 is that S5 is present but S2 is absent; and in S5, the amount of conductive agent (single-walled carbon nanotubes, multi-walled carbon nanotubes, VGCF) is reduced to 1 / 4 of the original amount.

[0095] Comparative Example 5 The difference between this comparative example and Example 1 is that S5 is present but S2 is absent; and in S5, the amount of adhesive (PAA) is reduced to 1 / 4 of the original amount.

[0096] Comparative Example 6 The difference between this comparative example and Example 1 is that in S2 and S5, the amount of adhesive (PAA) and conductive agent is reduced to 1 / 4 of the original amount.

[0097] Test case The pouch cells prepared in Examples 1-16 and Comparative Examples 1-6 were charged to 4.0V at a constant temperature of 45°C with a 0.2C constant current. The capacity retention of the pouch cells corresponding to the examples and comparative examples after 60 days of storage at 45°C and after 500 cycles of 1C charge-discharge at 45°C were tested using the test channel.

[0098] Table 1 Battery High Temperature Performance

[0099] As can be seen from Table 1, the batteries provided in Examples 1-7, 9, and 11-15 of the present invention have more stable electrical performance output, higher cycle life, and better storage capacity retention than the batteries provided in Comparative Examples 1-6.

[0100] As can be seen from Examples 1-2 and Comparative Examples 2-6, a high concentration gradient of binder and conductive agent is beneficial to stabilizing the overall structure, making the battery electrode more stable under high temperature conditions, and better suppressing stress release and microcrack expansion on the electrode.

[0101] As can be seen from Examples 1 and 3-5, an appropriate amount of large-particle filler is more conducive to stabilizing the interface, resulting in stronger internal bonding of the electrode and slower degradation of electrical performance. As can be seen from Examples 1 and 8-10, adding excessive amounts of large-particle filler and reducing the proportion of binder and carbon black has limited improvement effect.

[0102] Overall, the addition of large-particle fillers results in a coating process with very high requirements because the slurry contains both large and small particles, which can easily lead to fluctuations in battery quality. In contrast, the simple high-gradient thin coating without large-particle fillers does not have this problem. Compared with Comparative Examples 1 to 6, the electrical performance of Examples 1 to 2, Example 6, and Examples 11 to 16 with high-gradient thin coatings without large-particle fillers is generally steadily improved and has high repeatability.

[0103] In summary, the battery provided by this invention has a robust and stable structure, enabling it to function effectively for a long time. The high-gradient thin coating significantly improves the battery's cycle and rate performance.

[0104] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A battery electrode having a high gradient thin coating, characterized by, The battery electrode comprises a high-gradient thin coating layer and a first active material layer and a second active material layer on both sides of the high-gradient thin coating layer. The high-gradient thin coating layer contains 25% to 67% of a conductive agent, 20% to 50% of a binder and 0% to 25% of a large-particle filler in terms of mass percentage; wherein the large-particle filler is used to improve the overall mechanical strength and electrical performance of the electrode tab.

2. The battery electrode of claim 1, wherein, The high-gradient thin coating layer is embedded in occlusion at the joint with the first active material layer and the second active material layer.

3. The battery electrode according to claim 1 or 2, characterized in that, When the large-particle filler is not added, the thickness of the high-gradient thin coating layer is 10 nm to 1800 nm; Or, the thickness of the first active material layer and the second active material layer is not less than 10 nm; Preferably, the distance between the high-gradient thin coating layer and the overall golden section point of the battery electrode is not more than 1000 nm.

4. The battery electrode of claim 1, wherein, The binder is selected from at least one of PVDF, PTFE, cellulose derivatives, alginic acid compounds and PAA compounds.

5. The battery electrode of claim 1, wherein, The conductive agent is selected from at least one of carbon black, ketjen black, acetylene black, VGCF, carbon nanotubes, carbon fibers, graphene, natural graphite, artificial graphite, aluminum and copper; Preferably, the conductive agent contains carbon nanotubes.

6. The battery electrode of claim 1, wherein, D50 of the large particle filler is from 300 nm to 20 μm. 50 from 300 nm to 20 μm. And / or, the large-particle filler comprises at least one of active materials, lithium supplement agents and non-active materials.

7. The battery electrode of claim 1, wherein, The high-gradient thin coating layer further contains 0% to 3% of a dispersant; Preferably, the dispersant comprises at least one of maleic acid and C12-22 alpha-olefin copolymer and maleic anhydride-styrene copolymer grafted polyoxyethylene-polyoxypropylene (EO-PO) block copolymer; Preferably, the mass percentage of the dispersant in the high-gradient thin coating layer is not more than 0.3%.

8. A method of producing a battery electrode as claimed in any one of claims 1 to 7, characterized in that The method comprises the following steps: Preparation of the first active material layer on the surface of the electrode tab; Coating of the slurry for preparation of the high-gradient thin coating layer on the surface of the first active material layer, drying, to obtain an electrode tab with a high-gradient thin coating layer; Preparation of the second active material layer on the other side surface of the high-gradient thin coating layer.

9. A battery, characterized by The battery comprises the battery electrode according to any one of claims 1 to 7.

10. An electrical device, characterized by The electric device comprises the battery according to claim 9.

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