Composite current collector and vertical graphite directional deposition method and application of copper foil surface thereof

Abstract

The application discloses a composite current collector and a vertical graphite directional deposition method and application of a copper foil surface of the composite current collector. The method comprises the following steps: preparing a (111) single crystal copper foil, evaporating an island-shaped nano copper transition layer, and adopting a two-stage PECVD process to form a planar buffer layer at low power and then to excite vertical growth at high power, and combining pulse gas supply and spectrum monitoring to realize accurate thickness control. The prepared composite current collector has a structure of "single crystal copper foil / planar graphene buffer layer / vertical graphene", the interface resistance is less than 60 Ω, and the contact angle is greater than 125°, and the composite current collector is suitable for fields of lithium ion battery current collectors, heat-conducting interface materials and field emission devices.

Description

Technical Field

[0001] This invention relates to the fields of new energy materials and nano-manufacturing technology, specifically to a method for vertical graphite directional deposition on copper foil surface based on lattice matching induction and plasma control, a composite current collector prepared by this method, and its applications. Background Technology

[0002] Graphene, as a single-layer hexagonal carbon lattice material, possesses excellent electrical, thermal, and mechanical properties. Traditional graphene preparation methods (such as mechanical exfoliation and chemical vapor deposition, CVD) are mostly planar growth methods, which easily lead to stacking between layers, resulting in low specific surface area utilization and insufficient surface active sites, limiting its applications in energy storage, catalysis, and other fields. Vertically structured graphene (such as graphene nanowalls and nanosheets), due to its three-dimensional open structure, high specific surface area, and abundant edge active sites, has become key to solving the above problems.

[0003] However, existing technologies, such as CN110190286A, disclose a vertical graphene-copper foil composite current collector based on in-situ growth and its preparation method, which uses single-stage constant power PECVD to grow vertical graphene on ordinary copper foil, but still have the following shortcomings: Uncontrollable vertical orientation: Due to the lack of lattice-matched substrate induction, the growth orientation of graphene is random, which easily leads to mixed orientation structures, resulting in poor vertical array consistency; Thickness is difficult to control precisely: relying solely on reaction time to control thickness cannot provide real-time feedback on the growth process, resulting in large batch-to-batch thickness fluctuations (errors can reach ±20μm or more), affecting product consistency. Lack of gradient energy field regulation: Single-stage constant power cannot form a buffer layer before vertical growth is excited, resulting in insufficient bonding force between graphene and the substrate, and limited long-term cycling stability.

[0004] Therefore, the present invention aims to provide a method for vertical graphite orientation deposition on copper foil surface based on lattice matching induction and plasma control, so as to achieve large-scale preparation of composite current collectors with controllable vertical orientation, precise thickness and uniform structure. Summary of the Invention

[0005] This invention addresses the problems of poor adhesion of graphite layers on copper foil surfaces, insufficient electrical and thermal conductivity in the vertical direction, and difficulty in thickness control in existing technologies. It proposes a method for vertically oriented graphite deposition on copper foil surfaces based on lattice matching induction and plasma regulation, a composite current collector prepared by this method, and its applications.

[0006] In a first aspect, to achieve the above objectives, the present invention adopts the following technical solution: a method for vertical graphite orientation deposition on a copper foil surface based on lattice matching induction and plasma modulation, comprising the following steps: S1: Prepare a (111) crystal plane single-crystal copper foil substrate and deposit an island-shaped nano-copper transition layer on its surface; S2: Vertical graphene directional deposition is carried out using a two-stage variable power PECVD process. First, a planar graphene buffer layer is deposited with a low power of 150W±10%, and then vertical graphene growth is excited with a high power of 400W±10%. S3: The thickness of the vertical graphite layer is controlled at 50~80μm through pulsed gas supply and real-time monitoring of plasma spectrum.

[0007] Preferably, as an improvement, in S1, the preparation method of the (111) crystal plane single-crystal copper foil is as follows: annealing the polycrystalline copper foil at 1040~1060℃ in an H2 / Ar atmosphere for 30~40 min to obtain a crystal domain size >10cm. 2 (111) single crystal copper foil.

[0008] Preferably, as an improvement, the preparation parameters of the island-shaped nano-copper transition layer in S1 are: vacuum evaporation of 85±10nm island-shaped nano-copper with a particle size of 380±10nm, and repeated evaporation 4~6 times to form a layered structure.

[0009] Preferably, as an improvement, in S2, the two-stage PECVD process specifically refers to: Planar layer stage: power 150±20W, CH4:Ar=1:5~8, pressure 20±10Pa, time 20~35s, forming 8~12 planar graphene buffer layers; Vertical layer stage: power increased to 400±20W, CH4:Ar=1:4~6, pressure 500±100Pa, time 50~70min.

[0010] Preferably, as an improvement, in S3, the on / off ratio of the pulsed gas supply is 1:2 to 1:3. By real-time monitoring of the intensity of the characteristic peak of carbon atoms in the plasma emission spectrum, growth is stopped when a set threshold is reached, thereby controlling the thickness of the vertical graphite layer to 50 to 80 μm.

[0011] Secondly, the present invention provides a composite current collector prepared by the above method, characterized in that the composite current collector has a sandwich structure of "single crystal copper foil (111) / planar graphene buffer layer / vertical graphene", wherein the orientation deviation angle of the vertical graphene is <5° and the thickness error is ±5μm.

[0012] Preferably, as an improvement, the composite current collector has an interfacial resistance of <60Ω and an electrolyte contact angle of >125°.

[0013] Thirdly, the composite current collector is used in lithium-ion battery current collectors, thermally conductive interface materials, or field emission devices. It is particularly suitable for scenarios with strict requirements on the orientation consistency and thickness uniformity of vertical graphene arrays: Ultra-thin composite current collectors in high-energy-density lithium-ion batteries (thickness error must be <5μm); Field emission cathode array (vertical orientation deviation must be <5° to ensure emission uniformity); Chip-level thermal management materials (vertical graphene as a thermal conduction pathway, with precise thickness control to avoid short-circuit risks). This invention achieves the directional growth of vertical graphene based on a synergistic mechanism of "lattice matching induction + gradient energy field regulation". Its core working principle is as follows: By preparing (111) crystal plane single-crystal copper foil, whose hexagonal lattice mismatch rate with graphene is <5%, an ideal template-based nucleation interface is provided for graphene. Based on this, an island-shaped nano-copper transition layer is vapor-deposited to form high-density nanoscale active sites, significantly reducing the energy barrier for vertical graphene nucleation and inducing the preferential growth of graphene nuclei along a direction perpendicular to the substrate.

[0014] In the PECVD process, plasma power, gas pressure, and carbon source concentration jointly determine the growth mode of graphene. This invention employs a two-stage variable power strategy: Low power (150W) stage: With lower plasma energy, carbon radicals diffuse primarily at the surface, preferentially forming a continuous and dense planar graphene buffer layer, providing the structural basis for subsequent vertical growth. High power (400W) stage: The plasma energy is significantly increased, generating high-density ion bombardment and a strong electric field effect, forcing the graphene sheets to grow vertically from a planar orientation, forming a three-dimensional open structure.

[0015] Dynamic thickness control: The pulse gas supply mode (on / off ratio 1:3) is adopted to effectively suppress the lateral diffusion of carbon source during the gas cut-off stage and avoid over-growth; at the same time, the intensity of carbon atom characteristic peaks is monitored in real time by plasma emission spectroscopy, and the growth is automatically terminated when the preset threshold is reached, so as to achieve precise thickness control (50-80μm, error ±5μm).

[0016] Compared with the prior art, the present invention has the following beneficial effects: Nucleation orientation is controllable: Vertical orientation nucleation of graphene is achieved by lattice matching induction between (111) single-crystal copper foil and island-shaped nano-copper, with a vertical orientation deviation angle of <5°, avoiding disordered or mixed orientation structures.

[0017] High structural uniformity: The two-stage PECVD process combined with pulsed gas supply can obtain highly consistent vertical graphene arrays over a large area, with thickness error controlled within ±5μm.

[0018] The composite current collector (single-crystal copper foil / planar buffer layer / vertical graphene) prepared in this invention exhibits excellent interfacial properties: The interface resistance is <60Ω and the electrolyte contact angle is >125°, indicating good wettability.

[0019] Improved electrochemical performance: The half-cell coin cells using the composite current collector of this invention exhibit excellent rate performance and cycle stability (0.2C cycle data).

[0020] Strong process compatibility: The method of this invention is based on mature PECVD equipment, which is easy to scale up for production and is applicable to fields such as lithium-ion battery current collectors, thermal interface materials and field emission devices. Attached Figure Description

[0021] Figure 1 SEM comparison images of lithium deposition on the surfaces of polycrystalline copper foil and monocrystalline copper foil (111); Figure 2 XRD pattern of single-crystal copper foil (111); Figure 3 The Raman spectra of graphene with defects and graphene without defects are shown in comparison. Figure 4 This is a test diagram of the electrolyte contact angle on the surface of the composite current collector of the present invention; Figure 5 This is the electrochemical impedance spectroscopy (EIS) spectrum of the composite current collector of the present invention; Figure 6 The graph shows the coin rate performance test results of the half-cell using the composite current collector of this invention. Figure 7 The graph shows the 0.2C cycle performance test results of a half-cell using the composite current collector of this invention. Detailed Implementation

[0022] The following detailed description illustrates the specific implementation method: Example 1: Step 1: Preparation of single-crystal copper foil substrate A 25 μm thick polycrystalline copper foil was placed in a tube furnace and annealed at 1040 °C in an H2 / Ar (volume ratio 1:9) atmosphere for 30 min. After natural cooling, a (111) crystal plane single-crystal copper foil with a crystal domain size of approximately 12 cm was obtained. 2 Vacuum evaporation equipment was used to deposit 85nm island-shaped copper nanoparticles (particle size approximately 380nm) onto the surface of single-crystal copper foil. The deposition was repeated four times to form a multilayer copper nanoparticle transition layer.

[0023] Step 2: Vertical Graphite Oriented Deposition The copper foil was placed in the PECVD reaction chamber, and the vacuum was evacuated to 1×10⁻⁶. -3The pressure was increased to 650℃. A mixture of CH4 and Ar gas was introduced, and planar layer deposition was performed first: power 150W, CH4:Ar=1:5, pressure 20Pa, time 30s. Then, vertical layer deposition was performed: power 400W, CH4:Ar=1:4, pressure 500Pa, time 60min.

[0024] Step 3: Thickness Control A pulsed gas supply mode with an on / off ratio of 1:3 was used during deposition. The intensity of the C2 (516 nm) characteristic peak in the plasma emission spectrum was monitored in real time, and growth was automatically stopped when the intensity reached a preset threshold. The measured thickness of the vertical graphite layer was 65 μm, with a thickness error of ±4 μm.

[0025] Performance testing The composite current collector prepared in Example 1 was used as the negative electrode current collector to assemble a half-cell (a coin cell in a 2016 battery case, with a lithium sheet as the counter electrode), and the following tests were performed: Interface resistance: tested using EIS, the result is 55Ω (see...) Figure 5 ); Contact angle: Using a contact angle measuring instrument, the electrolyte contact angle is 128° (see...). Figure 4 ); Rate performance: Capacity retention at 0.2C, 0.5C, 1C, and 2C rates is shown in [reference needed]. Figure 6 ; Cyclic performance: After 100 cycles at 0.2C, the capacity retention was 96.2% (see...). Figure 7 ).

[0026] Comparative Example Using a commercially available carbon-coated copper foil current collector as the substrate, island-shaped copper nanoparticles were deposited without vapor deposition using single-stage PECVD (constant 400W) for 60 min, with other conditions the same as in Example 1. The resulting product exhibited disordered vertical graphene orientation, uneven thickness (20~120μm), an interfacial resistance of 120Ω, and a contact angle of 95°.

[0027] in conclusion Compared with the comparative example, the composite current collector of the present invention has significant advantages in terms of vertical graphene orientation consistency, thickness uniformity, interface resistance and wettability, verifying the effectiveness of the synergistic mechanism of "lattice matching induction + gradient energy field regulation".

[0028] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for vertically oriented graphite deposition on the surface of a copper foil composite current collector, characterized in that, Includes the following steps: S1: Prepare a (111) crystal plane single-crystal copper foil substrate and deposit an island-shaped nano-copper transition layer on its surface; S2: Vertical graphene directional deposition is carried out using a two-stage variable power PECVD process. First, a planar graphene buffer layer is deposited with a low power of 150W±10%, and then vertical graphene growth is excited with a high power of 400W±10%. S3: The thickness of the vertical graphite layer is controlled at 50~80μm through pulsed gas supply and real-time monitoring of plasma spectrum.

2. The method according to claim 1, characterized in that, In S1, the preparation method of (111) crystal plane single crystal copper foil is as follows: annealing polycrystalline copper foil at 1040~1060℃ in H2 / Ar atmosphere for 30~40min to obtain a crystal domain size >10cm. 2 (111) single crystal copper foil.

3. The method according to claim 1, characterized in that, In S1, the preparation parameters for the island-shaped nano-copper transition layer are: vacuum evaporation of 85±10nm island-shaped nano-copper with a particle size of 380±10nm, and repeated evaporation 4~6 times to form a layered structure.

4. The method according to claim 1, characterized in that, In S2, the two-stage PECVD process specifically refers to: Planar layer stage: power 150±20W, CH4:Ar=1:5~8, pressure 20±10Pa, time 20~35s, forming 8~12 planar graphene buffer layers; Vertical layer stage: power increased to 400±20W, CH4:Ar=1:4~6, pressure 500±100Pa, time 50~70min.

5. The method according to claim 1, characterized in that, In S3, the on / off ratio of pulsed gas supply is 1:2 to 1:

3. By real-time monitoring of the intensity of the characteristic peak of carbon atoms in the plasma emission spectrum, growth is stopped when a set threshold is reached, thus controlling the thickness of the vertical graphite layer to 50 to 80 μm.

6. A composite current collector prepared by the method according to any one of claims 1 to 5, characterized in that, The composite current collector has a sandwich structure of "single crystal copper foil (111) / planar graphene buffer layer / vertical graphene", wherein the orientation deviation angle of the vertical graphene is <5° and the thickness error is ±5μm.

7. The composite current collector according to claim 6, characterized in that, The composite current collector has an interfacial resistance of <60Ω and an electrolyte contact angle of >125°.

8. The application of the composite current collector as described in claim 7 in lithium-ion battery current collectors, thermally conductive interface materials, or field emission devices.

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