Current collector with anti-dendritic carbon coating, preparation method of current collector, pole piece and sodium ion battery

Abstract

The invention discloses a current collector with an anti-dendritic carbon coating, a preparation method of the current collector, a pole piece and a sodium ion battery. The current collector comprises a copper foil substrate and a gradient carbon coating on the surface of the copper foil substrate, the carbon coating comprises a first carbon coating close to the copper foil substrate and a second carbon coating far away from the copper foil substrate. According to the gradient carbon coating scheme, the double-layer structure design is adopted, and the performance of the current collector of the sodium-ion battery is remarkably improved. The first carbon layer is mainly composed of graphene and carbon nanotubes, a low-porosity conductive layer is formed, uniform conduction of electrons is ensured, and dendritic crystal growth is avoided. The second carbon layer is mainly made of hard carbon and added with Sn or Bi nano-particles, a high-porosity sodium-philic layer is formed, the sodium deposition / removal overpotential is reduced, and the ion transmission path is optimized. According to the scheme, through material and process optimization, dendritic crystals can be effectively inhibited, the chemical stability is improved, the method has more advantages in cycling stability and safety, and a guarantee is provided for long-term reliability of the sodium-ion battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a current collector with an anti-dendritic carbon coating, its preparation method, an electrode, and a sodium-ion battery. Background Technology

[0002] The core challenge facing sodium-ion batteries during cycling stems from the physical characteristic that sodium ions have a significantly larger radius than lithium ions. This difference makes it easier for sodium ions to form disordered dendrites when deposited on the electrode surface. When sodium dendrites continue to grow and penetrate the separator, they will cause an internal short circuit in the battery, seriously threatening the battery's safety and cycle life. Existing technologies suffer from two major drawbacks: First, the sodium dendrite problem is essentially a direct consequence of uneven sodium deposition. Due to the high nucleation barrier of sodium ions on the electrode surface, their deposition process often exhibits localized concentration, thus inducing dendrite growth. Second, the interfacial characteristics of copper foil as a current collector are significantly insufficient. Specifically, the wettability of the bare copper foil surface with sodium (contact angle greater than 90°) leads to a significant increase in the initial nucleation overpotential of sodium ions on the copper foil surface, further exacerbating the unevenness of sodium deposition. In addition, the pore structure design of traditional carbon coating materials (such as acetylene black) has limitations. Its single pores cannot effectively guide the uniform distribution of sodium ions on the electrode surface, so that sodium ions still tend to accumulate locally during transport, thus failing to fundamentally suppress dendrite formation. Summary of the Invention

[0003] The purpose of this invention is to provide a current collector and its preparation method, an electrode, and a sodium-ion battery, which employs an anti-dendritic carbon coating to solve the aforementioned problems of sodium-ion batteries during cycling.

[0004] To achieve the above objectives, the technical solution provided by the present invention is as follows: The first aspect of this application provides a current collector with an anti-dendritic carbon coating, comprising a copper foil substrate and a gradient carbon coating on the surface of the copper foil substrate; The carbon coating comprises a first carbon coating close to the copper foil substrate and a second carbon coating away from the copper foil substrate; The first carbon coating is a low-porosity conductive layer mainly composed of graphene and carbon nanotubes; the second carbon coating is a high-porosity sodium-loving layer mainly composed of hard carbon and containing nanoparticles, wherein the nanoparticles are at least one of Sn and Bi.

[0005] The thickness of the copper foil substrate is 6~12μm; the thickness of the first carbon coating is 1.5~3μm; and the thickness of the second carbon coating is 4~6μm.

[0006] The first carbon coating has a porosity of 10-20%, and the second carbon coating has a porosity of 40-60%.

[0007] A second aspect of this application provides a method for preparing a current collector with an anti-dendritic carbon coating, comprising the following steps: S1: Cleaning, activation, and drying of the copper foil substrate; S2: Prepare and sequentially coat the surface of a copper foil substrate with a first carbon coating slurry containing graphene and carbon nanotubes, and a second carbon coating slurry containing hard carbon and nanoparticles, wherein the nanoparticles are at least one of Sn and Bi; S3: Dry the coated current collector; S4: Roll the dried current collector.

[0008] To optimize the above technical solution, the specific measures also include: In step S1, the cleaning is performed by acid washing, and the activation is performed by plasma activation.

[0009] In the first carbon coating slurry, excluding the solvent, the total mass percentage of graphene and carbon nanotubes is 65-75%, and the mass ratio of graphene to carbon nanotubes is 2.0:3.5-6.0; in the second carbon coating slurry, excluding the solvent, the mass percentage of hard carbon is 77-83%, and the mass percentage of nanoparticles is 4-6%.

[0010] Further, in step S2, the solid content of the first carbon coating slurry is 8.8~9.4%, and the viscosity is 300~330 mPa·s; the solid content of the first carbon coating slurry is 23~27%, and the viscosity is 410~460 mPa·s; the binder in both the first carbon coating and the second carbon coating is polyimide.

[0011] Furthermore, in step S3, the drying is a stepped drying process, which includes the following stages: First drying stage: Preheat at 75~85℃ for 4~6 minutes; Second drying stage: Heat at 115~125℃ for 25~35 minutes to cure.

[0012] A third aspect of this application provides an electrode comprising the aforementioned current collector with an anti-dendritic carbon coating.

[0013] A fourth aspect of this application provides a battery comprising the aforementioned electrode.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention significantly improves the cycle stability and safety of sodium-ion battery current collectors through an improved gradient carbon coating. The carbon coating employs a dual-layer structure. The first carbon coating, closer to the copper foil substrate, is primarily composed of graphene and carbon nanotubes, forming a low-porosity conductive layer that provides a uniform electron conduction path for sodium ions, effectively avoiding the risk of dendrite growth caused by localized current concentration. The second carbon coating, further away from the substrate, is mainly composed of hard carbon with added Sn or Bi nanoparticles, forming a high-porosity sodium-loving layer. The sodium-loving properties of the nanoparticles reduce the overpotential for sodium deposition / removal, making the sodium deposition process gentler. Simultaneously, the porous structure provides more channels for sodium ion transport, further optimizing the ion transport path. Furthermore, the use of polyimide binder and a stepped drying process ensures the chemical stability of the carbon coating at low potentials, enabling it to resist sodium corrosion and thus extending the current collector's lifespan.

[0015] Experiments show that the current collector using this scheme has significantly better capacity retention and stable cycle time than existing technologies. The effect of this technology is due to the synergistic effect of gradient pore design, sodium-affinity modification and corrosion-resistant binder. The dense carbon layer at the bottom ensures efficient electron conduction, the porous structure on the surface promotes uniform diffusion of sodium ions, Sn or Bi nanoparticles reduce the sodium nucleation barrier, and the polyimide binder enhances the structural integrity and durability of the coating.

[0016] Overall, this solution achieves the invention objectives of suppressing dendrites, improving chemical stability, and optimizing ion transport through material combination and process optimization, providing a reliable guarantee for the long-term cycle stability and safety of sodium-ion batteries. Detailed Implementation The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0017] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the reagents, methods and equipment used are conventional reagents, methods and equipment in this technical field.

[0018] The present invention provides a current collector with an anti-dendritic carbon coating, comprising a copper foil substrate and a gradient carbon coating on the surface of the copper foil substrate; The carbon coating comprises a first carbon coating close to the copper foil substrate and a second carbon coating away from the copper foil substrate; The first carbon coating is a low-porosity conductive layer mainly composed of graphene and carbon nanotubes; the second carbon coating is a high-porosity sodium-loving layer mainly composed of hard carbon and containing nanoparticles, wherein the nanoparticles are at least one of Sn and Bi.

[0019] The technical solution of this invention effectively achieves the objectives of suppressing dendrites, improving chemical stability, and optimizing ion transport pathways through the structural design and material combination of gradient carbon coating.

[0020] Specifically, the first carbon coating, which is close to the copper foil substrate, is mainly composed of graphene and carbon nanotubes to form a low-porosity conductive layer, providing a uniform electronic conduction path for sodium ions, which helps to reduce local current concentration and thus reduce the risk of dendrite formation; while the second carbon coating, which is far away from the copper foil substrate (close to the electrolyte and active material), is mainly composed of hard carbon and has Sn or Bi nanoparticles added to form a high-porosity sodium-loving layer.

[0021] On the one hand, this invention reduces the overpotential for sodium deposition and extraction by utilizing the sodium-affinity properties of hard carbon and Sn or Bi nanoparticles, resulting in more uniform sodium deposition. On the other hand, the higher porosity provides more channels for sodium ion transport, optimizes the ion transport path, and further suppresses dendrite formation.

[0022] Furthermore, the use of polyimide binder and the step drying process ensure the chemical stability of the carbon coating at low potentials, enabling it to resist sodium corrosion; the entire gradient coating structure transitions from conductivity to sodium affinity, and the synergistic effect effectively suppresses sodium dendrites, while improving the overall performance and cycle stability of the current collector.

[0023] In some embodiments, the thickness of the copper foil substrate is 6-12 μm, preferably 8 μm; the thickness of the first carbon coating is 1.5-3 μm; and the thickness of the second carbon coating is 4-6 μm.

[0024] In some embodiments, the porosity of the first carbon coating is 10-20%, and the porosity of the second carbon coating is 40-60%.

[0025] It should be noted that the porosity control of the carbon coating of the present invention can be achieved by adjusting the solid content and rolling parameters of each carbon coating slurry.

[0026] When the porosity of the first carbon coating is too high (exceeding 20%), its conductivity is reduced, leading to uneven electron conduction paths, increasing the risk of localized current concentration, and thus promoting dendrite formation. Simultaneously, excessive porosity weakens the physical shielding effect of the coating, making it easier for corrosive media to penetrate the copper foil substrate surface. When the porosity of the first carbon coating is too low (below 10%), although conductivity is guaranteed, it restricts the transport channels for sodium ions, increasing ion transport resistance and affecting the battery's rate performance.

[0027] Excessive porosity (over 60%) in the second carbon coating significantly reduces the loading stability of hard carbon, leading to easy aggregation of Sn or Bi nanoparticles and making it difficult to effectively suppress silicon particle aggregation. Simultaneously, excessive porosity weakens the coating structure strength, affecting long-term cycling stability. When the porosity of the second carbon coating is too low (below 40%), it cannot provide sufficient buffer space for silicon volume expansion, easily causing electrode structure collapse during charge and discharge. Furthermore, insufficient porosity restricts sodium ion transport channels, increases electrolyte wetting resistance, and reduces battery performance.

[0028] The present invention also provides a method for preparing a current collector with an anti-dendritic carbon coating, comprising the following steps: S1: Cleaning, activation, and drying of the copper foil substrate; S2: Prepare and sequentially coat the first carbon coating paste and the second carbon coating paste onto the surface of the copper foil substrate; S3: Dry the coated current collector; S4: Roll the dried current collector.

[0029] In step S1, cleaning is performed by acid washing and activation is performed by plasma activation to improve adhesion.

[0030] In some embodiments, pickling can be performed using H2SO4 + H2O2. H2SO4 removes oxides from the surface of the copper foil, while H2O2 acts as an oxidant to generate a micron-level roughness of 0.2~0.5μm, thereby increasing the specific surface area.

[0031] In some implementations, plasma activation can be performed using an Ar atmosphere (purity > 99.99%) to prevent copper oxidation while bombarding the surface to form active sites.

[0032] In some embodiments, in the first carbon coating slurry, excluding the solvent, the total mass percentage of graphene and carbon nanotubes is 65-75%, and the mass ratio of graphene to carbon nanotubes is 2.0:3.5-6.0; in the second carbon coating slurry, excluding the solvent, the mass percentage of hard carbon is 77-83%, and the mass percentage of nanoparticles is 4-6%.

[0033] The first carbon coating slurry contains, in addition to the solvent, 25-40% by mass of a high-molecular polymer material; the second carbon coating slurry contains, in addition to the solvent, 10-20% by mass of a high-molecular polymer material. Preferably, the high-molecular polymer material can be polyimide (PI) or other equivalent alternative materials; the corrosion-resistant binder polyimide (PI) exhibits stronger chemical stability at low potentials than traditional PVDF, and can withstand the reduction reaction of sodium ions, ensuring the structural integrity and durability of the carbon coating during long-term cycling.

[0034] It should be noted that other components in the first carbon coating slurry and the second carbon coating slurry may be conventional additives in the art.

[0035] In step S2, the solid content of the first carbon coating slurry is 8.8~9.4%, and the viscosity is 300~330 mPa.s; the solid content of the second carbon coating slurry is 23~27%, and the viscosity is 410~460 mPa.s; the binder in both the first carbon coating and the second carbon coating is polyimide.

[0036] In some embodiments, in step S3, the drying is a stepped drying process, including the following stages: First drying stage: Preheat at 75~85℃ for 4~6 minutes; Second drying stage: Heat at 115~125℃ for 25~35 minutes to cure.

[0037] In the present invention, stepped drying effectively avoids stress concentration, ensures binder curing and pore structure optimization by controlling the temperature in stages, and is an essential process for preparing high-performance anti-dendritic carbon coatings: Stepped drying allows the solvent to evaporate slowly in the preheating stage (75~85℃) to avoid stress concentration; the second stage of stepped drying (115~125℃) aims to cure the polyimide (PI) binder to ensure the stability of the coating structure.

[0038] If direct high-temperature heating is used, the solvent on the coating surface will evaporate rapidly, and the internal solvent will vaporize due to heat, forming a huge vapor pressure. This can easily crack the coating and prevent the PI from fully cross-linking, resulting in insufficient coating adhesion. In subsequent rolling or battery cycling, the coating is prone to peeling. Therefore, although direct heating simplifies the process, it brings risks such as cracking, structural instability and performance degradation.

[0039] The present invention also provides an electrode comprising the above-described current collector having an anti-dendritic carbon coating.

[0040] The present invention also provides a battery comprising the above-described electrode.

[0041] This invention significantly improves the performance of current collectors through the synergistic effect of gradient pore design, sodium-affinity modification, and corrosion-resistant binder. The gradient pore design ensures efficient electron conduction in the dense carbon layer at the bottom, avoiding current concentration, while the porous structure on the surface promotes uniform diffusion of sodium ions and effectively inhibits dendrite growth. Sodium-affinity modification reduces the sodium nucleation barrier through Sn or Bi nanoparticles, making the sodium deposition process gentler and further reducing the risk of dendrite formation. This invention also ensures the structural integrity and durability of the carbon coating during long-term cycling through the chemical stability of the corrosion-resistant binder polyimide (PI). These features together optimize the sodium ion transport path, enhance the current collector's anti-dendrite ability and cycling stability, thereby achieving the goals of reducing sodium deposition / extraction overpotential, inhibiting dendrite formation, and improving chemical stability.

[0042] The technical solution of the present invention will be further described in detail below with reference to specific embodiments: Example 1 (1) Treatment of copper foil substrate: An 8μm copper foil substrate was used. The substrate was acid-washed using H2SO4 and 30% H2O2 at a volume ratio of 3:1 for 40 seconds at 25±5℃. The copper foil substrate was then plasma-activated in an Ar atmosphere (purity > 99.99%) at a power of 100W for 2 minutes. Finally, it was dried. (2) Prepare and apply the first carbon coating paste and the second carbon coating paste: The solids in the first carbon coating slurry comprise the following components by mass percentage: polyimide (PI) 30%; carbon nanotubes 46%; graphene 20%; additives 2.7%; wetting agent 1.3%. The solvent used was NMP. The first carbon coating slurry was prepared according to the above formula: slurry solid content: 9.17%, D50 < 177 nm, viscosity 313 mPa·s, single-sided surface density 1 mg / cm³. 2 The coating is applied to the surface of the treated copper foil substrate using gravure coating. The solids in the second carbon coating slurry include the following components by mass fraction: 80% hard carbon with a particle size of 1 μm, 5% Sn nanoparticles with a particle size of 20-30 nm, and 15% polyimide (PI); The solvent used is NMP. The second carbon coating slurry was prepared according to the above formula: the slurry has a solid content of 25% and a viscosity of 443 mPa·s. It was first dispersed and then sprayed: the dispersion process was as follows: zirconia balls were ball-milled at 300 rpm for 2 hours, and then ultrasonically treated at 40 kHz for 30 minutes to ensure that the Sn or Bi particles did not agglomerate; the spraying process was as follows: the slurry was atomized with a high-pressure airless electrostatic spray gun at a DC voltage of 50 kV and an air pressure of 0.3 MPa to control the droplet size. The spraying distance was 10 cm and the delivery rate was 1 mL / min.

[0043] (3) Drying Step drying is employed: The first stage involves preheating at 80℃ for 5 minutes to evaporate the solvent; The second stage involves curing at 120°C for 30 minutes to form cross-links and improve mechanical strength.

[0044] (4) Roller pressing: The carbon-coated copper foil current collector was obtained by cold pressing under a pressure of 5 MPa. The first carbon coating has a thickness of 2 μm and a porosity of 16%, while the second carbon coating has a thickness of 5 μm and a porosity of 49%.

[0045] (5) Battery fabrication: NaFeO2 (iron-based) was used as the positive electrode material, hard carbon was used as the negative electrode material, and a 24 μm polypropylene (PP) membrane and carbonate-based NaPF6 electrolyte were used. Polyvinylidene fluoride (PVDF) was used as the positive electrode binder, styrene-butadiene rubber (SBR) as the negative electrode binder, NMP as the positive electrode solvent, deionized water as the negative electrode solvent, carbon nanotubes and polystyrene (SP) as the positive electrode conductive agents, and carbon black (Super-P) as the negative electrode conductive agent. These were mixed in a certain proportion to form positive and negative electrode slurries. The positive electrode composition was: NaFeO2 95%, CNT 1.1%, SP 1.3%, PVDF (KF#9700) 2.6%; the negative electrode composition was: hard carbon 94.6%, SP 1.8%, CMC 1.5%, SBR 2.1%. These were uniformly coated on the surfaces of aluminum foil and carbon-coated copper foil current collectors, respectively. After drying, rolling, cutting, and drying, the electrode sheets required for the experiment were made. The electrode sheets were then stacked, assembled, baked, injected with electrolyte, and packaged to produce a 10 Ah soft-pack stacked sodium-ion battery.

[0046] Example 2 The scheme of this embodiment is basically the same as that of embodiment 1, except that in step (2), 5% of Sn nanoparticles with a particle size of 20~30nm are replaced with 5% of Bi nanoparticles with a particle size of 10~15nm in the second carbon coating slurry.

[0047] Example 3 The scheme of this embodiment is basically the same as that of embodiment 1, except that: in step (2) the 5% Sn nanoparticles with a particle size of 20~30nm in the second carbon coating slurry are replaced with: 3% Sn nanoparticles with a particle size of 20~30nm and 2.5% Bi nanoparticles with a particle size of 10~15nm.

[0048] Example 4 The scheme in this embodiment is basically the same as that in embodiment 1, except that: the thickness of the first carbon coating is 2.5 μm and the porosity is 25%; the thickness of the second carbon coating is 6 μm and the porosity is 54%.

[0049] Example 5 The scheme in this embodiment is basically the same as that in embodiment 1, except that: the thickness of the first carbon coating is 1.8 μm and the porosity is 8%; the thickness of the second carbon coating is 4 μm and the porosity is 35%.

[0050] Example 6 The scheme in this embodiment is basically the same as that in embodiment 1, except that: the thickness of the first carbon coating is 2.1 μm and the porosity is 20%; the thickness of the second carbon coating is 7 μm and the porosity is 68%.

[0051] Example 7 The scheme of this embodiment is basically the same as that of embodiment 1, except that the drying in step (3) is not done by step drying, but by direct heating: heating at 110°C for 40 minutes.

[0052] Comparative Example 1 In this comparative example, step (2) did not include Sn nanoparticles in the second carbon coating slurry, but otherwise it was the same as in Example 1.

[0053] Comparative Example 2 In this comparative example, the carbon-coated copper foil current collector of Example 1 was replaced with a conventional 8μm uncoated copper foil.

[0054] Comparative Example 3 In this comparative example, the carbon-coated copper foil current collector of Example 1 was replaced with a conventional 8μm carbon-coated copper foil; Carbon coating preparation process: Weigh the materials according to the process formula, stir, and then uniformly coat the surface of the current collector with the stirred slurry using a gravure coating machine; the formula is as follows: Table 1. Formulation of Comparative Example 3

[0055] Slurry solids content: 5.17%, D50 < 177 nm, viscosity 213 mPa·s, single-sided surface density 0.5 mg / cm³ 2 The carbon coating is applied to the surface of the stretched copper foil using gravure coating. After drying, the thickness of the single-sided carbon coating layer is about 1 μm, and the porosity is 30%.

[0056] The results of the experiments conducted on each embodiment and comparative example are shown in Table 2. Table 2 Comparison of test results between each embodiment and the comparative example

[0057] As can be seen from the test results in Table 1, the current collector with anti-dendritic carbon coating provided by the present invention exhibits excellent cycle stability and long-term cycle capability in sodium-ion batteries.

[0058] Examples 1-3 all achieved a capacity retention rate of over 85% after 300 cycles at 0.5C, at 1 mA / cm². 2 The stable cycling time at current density exceeded 1000 hours, significantly better than Comparative Examples 1, 2, and 3. This fully demonstrates the significant effects of the gradient carbon coating structure design and the added nanoparticle material combination on suppressing dendrite growth, improving chemical stability, and optimizing ion transport pathways.

[0059] Compared to Comparative Example 1, Examples 1-3 showed significant improvements in capacity retention and stable cycling time, indicating that the addition of Sn or Bi nanoparticles plays a crucial role in reducing sodium deposition and overpotential, and promoting uniform sodium deposition. However, Comparative Example 2 (conventional uncoated copper foil) and Comparative Example 3 (conventional coated copper foil, porosity 30%) exhibited significantly lower performance than the examples, further validating the criticality of gradient carbon coating design and porosity control in improving the current collector's anti-dendrite ability and cycling stability.

[0060] The performance of Examples 4-6 was slightly lower than that of Examples 1-3, but still significantly better than the comparative examples, which may be related to the change in porosity. In Example 4, the second carbon coating had a higher porosity, which, although beneficial for ion transport, may have slightly affected the stability of the coating structure. In Example 5, the first carbon coating had a lower porosity, which limited the transport channels for sodium ions, resulting in a slight decrease in performance. In Example 6, due to the excessively high porosity of the second carbon coating, the stability of the hard carbon support decreased, and Sn nanoparticles were prone to agglomeration, leading to a reduction in the utilization rate of the active material. At the same time, the excessively high porosity weakened the mechanical strength of the coating, making the electrode structure more prone to collapse during cycling and prone to microcrack propagation during long-term cycling.

[0061] In Example 7, direct heating caused the solvent on the coating surface to evaporate rapidly, and the internal vapor pressure cracked the coating, forming microcracks. The polyimide (PI) binder could not be fully cross-linked, resulting in insufficient adhesion. The high-temperature stress concentration caused by direct heating made the coating structure prone to microcrack propagation during cycling, resulting in a significant decrease in cycling stability, which was significantly lower than in other examples.

[0062] Overall, this invention achieves optimal performance by comprehensively considering conductivity, sodium affinity, and structural stability through the design of gradient carbon coatings, such as porosity, thickness, and material combination, as well as gradient drying processes, thus ensuring the long-term reliability of sodium-ion batteries. The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A current collector having an anti-dendrite carbon coating, characterized by: A gradient carbon coating including a copper foil substrate and a surface of the copper foil substrate; The carbon coating includes a first carbon coating close to the copper foil substrate and a second carbon coating away from the copper foil substrate; The first carbon coating is a low porosity conductive layer mainly including graphene and carbon nanotubes; the second carbon coating is a high porosity sodium-philic layer mainly including hard carbon and containing nanoparticles, the nanoparticles being at least one of Sn and Bi.

2. The current collector with anti-dendrite carbon coating of claim 1, wherein: The copper foil substrate has a thickness of 6-12 μm; the first carbon coating has a thickness of 1.5-3 μm; and the second carbon coating has a thickness of 4-6 μm.

3. The current collector with anti-dendrite carbon coating of claim 1, wherein: The first carbon coating has a porosity of 10-20%, and the second carbon coating has a porosity of 40-60%.

4. The method of producing a current collector having an anti-dendrite carbon coating according to any one of claims 1 to 3, characterized in that, The method includes the following steps: S1: cleaning, activation and drying of the copper foil substrate; S2: preparing and sequentially coating on the surface of the copper foil substrate a first carbon coating slurry containing graphene and carbon nanotubes, and a second carbon coating slurry containing hard carbon and nanoparticles, the nanoparticles being at least one of Sn and Bi; S3: drying the coated current collector; S4: rolling the dried current collector.

5. The method of claim 5, wherein: In step S1, the cleaning is performed by acid pickling, and the activation is performed by plasma activation.

6. The method of claim 5, wherein: In the first carbon coating slurry, the total mass percentage of graphene and carbon nanotubes, excluding the solvent, is 65-75%, and the mass ratio of graphene to carbon nanotubes is 2.0:3.5-6.0; in the second carbon coating slurry, the mass percentage of hard carbon, excluding the solvent, is 77-83%, and the mass percentage of nanoparticles is 4-6%.

7. The method of making a current collector with an anti-dendrite carbon coating of claim 5, wherein: In step S2, the solid content of the first carbon coating slurry is 8.8-9.4%, and the viscosity is 300-330 mPa.s; the solid content of the second carbon coating slurry is 23-27%, and the viscosity is 410-460 mPa.s; and the binder in the first carbon coating and the second carbon coating is polyimide.

8. The method of making a current collector with an anti-dendrite carbon coating of claim 5, wherein: In step S3, the drying is performed by step drying, including the following stages: First drying stage: preheating at 75-85 ℃ for 4-6 minutes; Second drying stage: heating and curing at 115-125 ℃ for 25-35 minutes.

9. A pole piece characterized by: A current collector having an anti-dendrite carbon coating as claimed in any one of claims 1-4 or prepared by the method as claimed in any one of claims 5-8.

10. A battery, characterized by: An electrode tab as claimed in claim 9.

Images