Single-walled carbon nanotube composite copper foil current collector, and preparation method and application thereof

Abstract

The application discloses a single-walled carbon nanotube composite copper foil current collector and a preparation method and application thereof, and belongs to the technical field of negative electrode-free lithium metal batteries. The current collector takes copper as a base body, and a composite interface layer containing uniformly dispersed single-walled carbon nanotubes is formed in situ through integrated electrodeposition, and the single-walled carbon nanotubes are metallurgically combined with the copper base body. In the preparation, copper salt, protonic acid, single-walled carbon nanotubes and composite additives are matched into an electrodeposition solution, and after ultrasonic dispersion, a titanium plate is used as a cathode, a phosphor copper plate is used as an anode, and constant-temperature and constant-current electrodeposition is adopted to obtain the current collector. The application can solve the problems of agglomeration of the single-walled carbon nanotubes and weak combination with the copper base body in the electrodeposition process, can significantly reduce a lithium nucleation barrier, can guide uniform deposition of lithium and inhibit dendrite growth, can buffer cyclic volume strain, and can improve the cycle life, safety and coulombic efficiency of the battery. The application has the advantages of simple process, low cost and easy scaling, and is suitable for being used as a negative electrode current collector of a negative electrode-free lithium metal battery.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, specifically relating to a single-walled carbon nanotube composite copper foil current collector, its preparation method, and its application. Background Technology

[0002] Electrodeless lithium metal batteries are considered one of the most promising technological routes for achieving next-generation high-energy-density energy storage systems. Their core design involves lithium ions being directly extracted from the positive electrode material and deposited on the current collector on the negative electrode side during the first charge, forming a lithium metal negative electrode in situ. During discharge, the lithium metal completely dissolves back into the positive electrode. This "negative electrodeless" architecture eliminates traditional negative electrode active materials (such as graphite), thus significantly improving the overall energy density of the battery and reducing cost and manufacturing complexity. However, the implementation of the negative electrodeless structure faces severe challenges, with its core bottleneck stemming directly from the deposition / dissolution behavior of lithium metal on the copper current collector. During repeated cycling, lithium tends to deposit non-uniformly, forming dendritic, moss-like, or dead lithium deposits, leading to a series of problems.

[0003] Studies have shown that the physicochemical properties of the current collector surface are key to regulating lithium nucleation and growth kinetics. The high surface energy barrier of smooth, inert commercial copper foil, coupled with its large lithium nucleation overpotential and random distribution of nucleation sites, is one of the fundamental reasons for uneven lithium deposition. Therefore, pretreating copper current collectors to construct a functional interface layer with lithiophilicity, high specific surface area, and stable structure has become an important strategy for improving the uniformity of lithium metal deposition and suppressing dendrite growth.

[0004] Currently, modification methods for copper current collectors mainly include constructing three-dimensional porous structures, coating with lithiophilic coatings, and surface alloying. Zhao proposed an ultrathin (35nm) artificial interface layer strategy based on polystyrene sulfonic acid (PSS) and montmorillonite (MMT) composite. The strategy promotes lithium-ion desolvation through the selective solvent repulsion effect of the nonpolar components of PSS and the lithiophilic adsorption of MMT, and accelerates lithium-ion transport through the low-barrier ion conduction channel of the PSS-MMT interface. At the same time, it induces the formation of an inorganic SEI rich in LiF / Li3N, thereby significantly improving the cycle stability and energy density of the electrodeless lithium metal battery (Advanced Materials, 2025, 37(41): e05520.). Patent CN114530606A proposes a modification strategy of in-situ growth of a nano-copper hydroxide array on the surface of a copper mesh and further modification by coating a carbon layer with an aldehyde-phenol polymer through pyrolysis. This constructs a copper-based current collector with a three-dimensional lithium-loving carbon interface. Through the synergistic effect of structural design and interface lithium-loving properties, the lithium-ion flow is effectively homogenized and the nucleation overpotential is reduced, thereby achieving uniform lithium deposition and long-term cycling stability. Choi JC et al. proposed a simple one-step electrodeposition method to in-situ construct a Cu2S thin layer on the surface of a copper foil. After lithiation conversion, a migratable Li2S artificial SEI layer is formed. This layer can effectively control the uniform and dense deposition of lithium, significantly improving the long-term cycling stability and commercial application potential of lithium metal batteries (Small, 2025, 21(1): 2408771.). These methods have all achieved certain results, but still have limitations: three-dimensional structures may exacerbate the consumption of electrodeposition solution and reduce volumetric energy density; some lithium-loving coatings have weak adhesion to copper and are easily peeled off under the huge volume changes of lithium deposition / dissolution; many processes are complex and costly, making them difficult to apply on a large scale.

[0005] Single-walled carbon nanotubes (SWCNTs) are widely recognized as ideal materials for modifying current collectors, theoretically offering mechanical reinforcement, conductive network construction, and nucleation sites to directly address the core challenges of lithium dendrite growth and interfacial instability. However, existing technologies (such as coating and hot pressing) cannot solve the problems of uneven dispersion of SWCNTs in electrolytes and weak adhesion to copper substrates, preventing the conversion of their theoretical advantages into stable and efficient battery performance. Electrodeposition, as a simple, controllable, and easily scalable surface engineering technique, provides an ideal way to construct functional interfacial layers on copper current collectors. Shimizu M et al. used a wet jet atomization strategy to achieve effective dispersion of SWCNTs and electrochemical co-deposition with a copper substrate, preparing a multilayer composite copper foil with a tensile strength of 519 MPa, providing a new approach for the structural design of high-performance current collectors. However, in this composite copper foil, the carbon nanotubes are mainly located between two copper foil layers, primarily serving a mechanical reinforcement function, and are unlikely to play a role in regulating lithium deposition on the current collector surface.

[0006] Therefore, developing a composite copper current collector with strong interfacial bonding, uniform lithium deposition, simple process, and suitability for large-scale production is of great significance for promoting the industrial application of electrodeless lithium metal batteries. Summary of the Invention

[0007] To address the core shortcomings of existing technologies, such as uneven lithium deposition due to the surface inertness of commercial copper foil, weak interfacial bonding and complex processes in mainstream coating / hot-pressing modification techniques, and the difficulty in achieving uniform composite nanomaterials through traditional electrodeposition, this invention achieves the following objectives through an integrated innovative design: First, it employs in-situ co-deposition technology to construct a strong and tough composite interface with the copper substrate, achieving metallurgical bonding and resolving the issues of weak interfacial bonding and easy peeling off; second, it utilizes a synergistic dispersion system of hydroxyethyl cellulose and the cationic surfactant octadecyltrimethylammonium chloride to achieve the uniform dispersion of single-walled carbon nanotubes in the plating solution and deposition layer. The method achieves uniform dispersion and robust composite formation. Simultaneously, by utilizing the synergistic effect of additives such as thiazoline and polyvinylpyrrolidone (PVP), ultrafine grains and micro / nano rough surfaces are obtained, providing numerous uniform lithium-affinity nucleation sites. Furthermore, through the synergistic effect of the single-walled carbon nanotube conductive network and ultrafine copper grains, an ideal surface structure is endowed in the current collector to lower the lithium nucleation barrier, guide uniform lithium deposition, and buffer cyclic volumetric strain. Finally, by optimizing the electrodeposition process, an efficient, controllable, and easily scalable preparation method is provided, systematically improving the cycle life, safety, and coulombic efficiency of electrodeless lithium metal batteries.

[0008] To address this issue, this invention utilizes single-walled carbon nanotubes (SHUs) as a functional enhancement phase, combining them in situ with copper during electrodeposition to directly construct a stable and multifunctional novel interface on the current collector substrate. To address the problem of SHUs easily agglomerating in aqueous solutions, this invention modifies their surface with a cationic surfactant, making it positively charged. This allows them to migrate electrophoretically towards the cathode under an electric field and achieve uniform co-deposition with copper. In the resulting composite current collector, the uniformly dispersed conductive network of SHUs and the ultrafine copper grains synergistically provide abundant lithium-affinity nucleation sites, significantly reducing the lithium nucleation overpotential and guiding uniform lithium nucleation growth. Simultaneously, the nanotube network confines and homogenizes the lithium-ion flux, effectively suppressing lithium dendrite formation and significantly improving the cycle stability of electrodeless lithium metal batteries.

[0009] To achieve its objectives, the present invention employs the following technical solution: This invention first discloses a single-walled carbon nanotube composite copper foil current collector. The composite copper foil current collector uses copper as a substrate and forms a composite interface layer with uniformly dispersed single-walled carbon nanotube reinforcing phase on the surface of the copper substrate through an integrated electrodeposition process. The single-walled carbon nanotubes are metallurgically bonded to the copper substrate in a three-dimensional conductive network structure. The interface layer has the functions of reducing the lithium nucleation barrier, guiding uniform lithium deposition, buffering cyclic volumetric strain, and improving the chemical and mechanical stability of the interface.

[0010] This invention further discloses a method for preparing the composite copper foil current collector, including the steps of electrodeposition solution preparation, ultrasonic dispersion, and electrodeposition molding, as detailed below: 1) Preparation of electrodeposition solution: Using deionized water as solvent, add copper salt, protic acid, single-walled carbon nanotubes and composite additives, and stir evenly with ultrasonication to obtain electrodeposition solution; 2) Electrodeposition: The electrodeposition solution is placed in a Hall cell, with a titanium plate as the cathode and a phosphor bronze plate as the anode. The electrodeposition solution is heated to the electrodeposition temperature, and electrodeposition is carried out under a constant current density to obtain a single-walled carbon nanotube composite copper foil current collector.

[0011] Preferably, in step 1), the copper salt is one or more of copper nitrate, copper sulfate, copper acetate, copper chloride, and copper oxalate; the protic acid is one or more of sulfuric acid, nitric acid, acetic acid, benzenesulfonic acid, and citric acid; and the composite additive includes thiazoline, polyvinylpyrrolidone, polyethylene glycol 6000, hydroxyethyl cellulose, octadecyltrimethylammonium chloride, and hydrochloric acid.

[0012] Preferably, in step 1), the concentrations of each component in the electrodeposition solution are as follows: copper salt 10~100 g / L; protic acid 10~200 g / L; single-walled carbon nanotubes 20~200 mg / L; thiazoline 1~10 mg / L; polyvinylpyrrolidone 10~50 mg / L; polyethylene glycol 6000 1~10 mg / L; hydroxyethyl cellulose 1~20 mg / L; octadecyltrimethylammonium chloride 50~200 mg / L; and hydrochloric acid 1~20 mg / L.

[0013] Preferably, in step 2), the electrodeposition temperature is 20~80℃ and the current density is 3~5A / dm³. 2 The electrodeposition time is 1–60 minutes. The optimal electrodeposition temperature is 53°C, and the current density is 4 A / dm³. 2 Electrodeposition time: 10 minutes.

[0014] The single-walled carbon nanotube composite copper foil current collector described in this invention can be applied to electrodeless lithium metal batteries as a negative electrode current collector.

[0015] Compared with the prior art, the beneficial effects of the present invention are reflected in: 1. This invention utilizes cationic surfactants to induce the electrophoretic migration of single-walled carbon nanotubes (SUVs), achieving in-situ co-deposition of SUVs with copper and constructing a composite interface with metallurgical bonding to the substrate. By employing a synergistic dispersion system of hydroxyethyl cellulose and surfactants, the problem of SUV agglomeration in the plating solution and deposition layer is solved, ensuring a uniform distribution of the conductive nanotube network within the copper substrate. In the fabricated composite current collector, the three-dimensional network of SUVs provides abundant lithiophilic nucleation sites, reducing the lithium nucleation overpotential from 59.6 mV in commercial copper foil to 29.2 mV. The flexible nanotube network effectively buffers volumetric strain during battery cycling, inhibiting lithium dendrite growth. The integrated composite structure significantly improves the interfacial mechanical and chemical stability, ensuring long-term cycle reliability of the battery. Electrochemical tests show that the half-cell using this composite current collector can stably cycle for over 200 cycles, with cycle life and coulombic efficiency significantly superior to traditional electrodeposited copper foil and commercial copper foil. This invention systematically solves key problems in electrodeless lithium metal batteries, such as uneven lithium deposition, easy dendrite growth, short cycle life, and poor safety.

[0016] 2. This invention employs a mild electrodeposition process, which is simple, has controllable conditions, low production costs, and is easy to scale up and commercialize. With the current energy structure shifting towards clean and renewable energy, the demand for high-energy-density storage devices continues to grow. Electrodeless lithium metal batteries, with their ultra-high energy density, have become an important development direction for next-generation energy storage and power batteries. The composite current collector of this invention can significantly improve the cycle stability, safety, and coulombic efficiency of electrodeless lithium metal batteries, possessing broad application prospects and significant industrial value in new energy vehicles, large-scale energy storage, and consumer electronics. Attached Figure Description

[0017] Figure 1 The image shows the Raman spectrum of the composite copper foil current collector obtained in Example 1 of this invention. Figure 2 This is a scanning electron microscope (SEM) image of the composite copper foil current collector obtained in Example 1 of the present invention; Figure 3 This is a scanning electron microscope (SEM) image of the composite copper foil current collector obtained in Example 2 of the present invention; Figure 4 This is a scanning electron microscope (SEM) image of the composite copper foil current collector obtained in Example 3 of the present invention; Figure 5 This is a scanning electron microscope (SEM) image of the copper foil current collector obtained in Comparative Example 3 of the present invention; Figure 6 This is a scanning electron microscope (SEM) image of the copper foil current collector obtained in Comparative Example 4 of the present invention; Figure 7 This is a scanning electron microscope (SEM) image of the copper foil current collector obtained in Comparative Example 5 of the present invention; Figure 8 This is a comparison chart of the coulombic efficiency of Embodiment 1, Comparative Example 1, and commercial copper foil of the present invention; Figure 9 This is a comparison diagram of lithium nucleation overpotential in Example 1, Comparative Example 1, and commercial copper foil of the present invention. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments. The embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0019] Example 1 Add 20.0 g of copper sulfate pentahydrate and 13.6 mL of concentrated sulfuric acid to a beaker, followed by a composite additive (37.5 μL of 10 wt% hydrochloric acid, 1.5 mg of thiazoline, 3.75 mg of polyvinylpyrrolidone K30, 1.25 mg of polyethylene glycol 6000, 2.0 mg of hydroxyethyl cellulose, and 24.5 mg of octadecyltrimethylammonium chloride). Finally, add 12.5 mg of single-walled carbon nanotubes and bring the volume to 250 mL with deionized water. Sonicate the mixture to obtain a uniformly dispersed electrodeposition solution.

[0020] Electrodeposition was carried out in a Hall cell, using a titanium plate as the cathode and a phosphor bronze plate as the anode. The system was heated to 53°C and held at a constant temperature, with an efficiency of 4 A / dm³. 2 Constant current electrodeposition was performed at the specified current density for 10 minutes. After deposition, the sample was removed from the titanium plate, rinsed with deionized water, and dried with nitrogen to obtain a single-walled carbon nanotube composite copper foil current collector.

[0021] Raman spectroscopy characterization results are as follows Figure 1 As shown, the intensity ratio (IG) of the G peak of the tangential vibration of single-walled carbon nanotubes to the defect-related D peak is... G / I D The SEM characterization result was 143.64, indicating that the sample contained single-walled carbon nanotubes with good crystallinity; the SEM characterization results are as follows. Figure 2 As shown, single-walled carbon nanotubes are uniformly dispersed in the copper matrix and tightly bonded to the copper matrix.

[0022] Example 2 The same preparation method as in Example 1 was used, except that the amount of single-walled carbon nanotubes added to the electrodeposition solution was 6.25 mg. The SEM image of the obtained sample is shown below. Figure 3 As shown, the deposition amount of single-walled carbon nanotubes decreases accordingly with decreasing concentration.

[0023] Example 3 The same preparation method as in Example 1 was used, except that the amount of single-walled carbon nanotubes added to the electrodeposition solution was 18.75 mg. The SEM image of the obtained sample is shown below. Figure 4As shown, when the concentration of single-walled carbon nanotubes is too high, agglomeration occurs on the surface of the copper substrate.

[0024] Comparative Example 1 The same preparation method as in Example 1 was used, except that no single-walled carbon nanotubes were added to the electrodeposition solution to obtain pure electrodeposited copper foil without a reinforcing phase.

[0025] Comparative Example 2 The same preparation method as in Example 1 was used, except that thiazoline, polyvinylpyrrolidone, and polyethylene glycol 6000 were not added to the electrodeposition solution, and a complete copper foil could not be formed after electrodeposition.

[0026] Comparative Example 3 The same preparation method as in Example 1 was used, except that hydroxyethyl cellulose and octadecyltrimethylammonium chloride were not added to the electrodeposition solution. SEM images of the obtained samples are shown below. Figure 5 As shown, due to the lack of dispersant, single-walled carbon nanotubes exhibit significant agglomeration and low deposition rate.

[0027] Comparative Example 4 The same preparation method as in Example 1 was used, except that the electrodeposition current density was 3 A / dm³. 2 The obtained sample SEM image is as follows. Figure 6 As shown, the deposition amount of single-walled carbon nanotubes is small and the distribution is uneven.

[0028] Comparative Example 5 The same preparation method as in Example 1 was used, except that the electrodeposition current density was 5 A / dm³. 2 The obtained sample SEM image is as follows. Figure 7 As shown, due to the excessively high current density, the copper foil grains are coarse and the deposition of single-walled carbon nanotubes is uneven.

[0029] The copper current collectors obtained in Example 1 and Comparative Example 1, as well as the commercial copper foil, were cut into 14mm diameter discs. CR2032 half-cells were assembled in an argon-atmospheric glove box, using a lithium foil as the counter electrode, Celgard 2400 as the separator, and 1M LiTFSI dissolved in DME:DOL (volume ratio 1:1) with 2wt% LiNO3 added as the electrolyte. The system operated at 1 mA / cm². 2 Current density, 1mAh / cm 2 Constant current charge-discharge tests were conducted under deposition capacity conditions.

[0030] The results are as follows Figure 8As shown, the single-walled carbon nanotube composite copper foil current collector prepared in Example 1 exhibits excellent cycling stability, maintaining high coulombic efficiency for more than 200 cycles. In contrast, the efficiency of Comparative Example 1 (pure electrodeposited copper foil) began to decline sharply after approximately 110 cycles, indicating that copper foil lacking single-walled carbon nanotube reinforcement is difficult to maintain uniform lithium deposition / stripping behavior over a long period. Furthermore, the performance of commercial copper foil degraded most rapidly, with efficiency decreasing rapidly after approximately 70 cycles.

[0031] Depend on Figure 9 The comparison diagram of lithium nucleation overpotentials shows that the lithium nucleation overpotential in Example 1 is 29.2 mV, in Comparative Example 1 it is 52.7 mV, and in commercial copper foil it is 59.6 mV. The single-walled carbon nanotube composite copper foil current collector of the present invention can significantly reduce the lithium nucleation overpotential and promote uniform lithium deposition.

[0032] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. 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 single-walled carbon nanotube composite copper foil current collector, characterized by, The composite copper foil current collector uses copper as the substrate and forms a composite interface layer on the surface of the copper substrate through integrated electrodeposition. In the composite interface layer, single-walled carbon nanotubes are uniformly dispersed as a reinforcing phase and form a metallurgical bond with the copper substrate.

2. The composite copper foil current collector of claim 1, wherein, The single-walled carbon nanotubes are distributed in the composite interface layer in a three-dimensional conductive network structure.

3. A method for producing the single-walled carbon nanotube composite copper foil current collector according to claim 1 or 2, characterized by, Includes the following steps: 1) Preparation of electrodeposition solution: Using deionized water as solvent, add copper salt, protic acid, single-walled carbon nanotubes and composite additives, and stir evenly with ultrasonication to obtain electrodeposition solution; 2) Electrodeposition: The electrodeposition solution is placed in a Hall cell, with a titanium plate as the cathode and a phosphor bronze plate as the anode. The electrodeposition solution is heated to the electrodeposition temperature, and electrodeposition is carried out under a constant current density to obtain a single-walled carbon nanotube composite copper foil current collector.

4. The production method according to claim 3, characterized by, The copper salt is selected from one or more of copper nitrate, copper sulfate, copper acetate, copper chloride, and copper oxalate; the protic acid is selected from one or more of sulfuric acid, nitric acid, acetic acid, benzenesulfonic acid, and citric acid.

5. The preparation method according to claim 3, characterized in that, The composite additives include thiazoline, polyvinylpyrrolidone, polyethylene glycol 6000, hydroxyethyl cellulose, octadecyltrimethylammonium chloride, and hydrochloric acid.

6. The production method according to claim 3 or 5, characterized by, The concentrations of each component in the electrodeposition solution are as follows: Copper salt concentration: 10~100g / L; Protic acid 10~200g / L; Single-walled carbon nanotubes: 20~200 mg / L; Thiazoline 1~10mg / L; Polyvinylpyrrolidone 10~50mg / L; Polyethylene glycol 6000 1~10mg / L; Hydroxyethyl cellulose 1~20 mg / L; Octadecyltrimethylammonium chloride 50~200 mg / L; Hydrochloric acid 1~20mg / L.

7. The preparation method according to claim 3, characterized in that, The electrodeposition temperature is 20~80℃, and the current density is 3~5A / dm³. 2 The electrodeposition time is 1 to 60 minutes.

8. The preparation method according to claim 3, characterized in that, The electrodeposition temperature was 53°C, the current density was 4 A / dm 2 , and the electrodeposition time was 10 minutes.

9. The application of the single-walled carbon nanotube composite copper foil current collector as described in claim 1 or 2 in a negative electrode-free lithium metal battery, characterized in that, Used as a negative electrode current collector.

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