Graphene oxide and polyacrylonitrile synergistically modified copper current collector for negative-electrode-free lithium metal battery and preparation method of graphene oxide and polyacrylonitrile synergistically modified copper current collector

Abstract

The invention discloses a graphene oxide and polyacrylonitrile synergistically modified copper current collector for a negative-electrode-free lithium metal battery and a preparation method of the graphene oxide and polyacrylonitrile synergistically modified copper current collector. According to the method, graphene oxide and polyacrylonitrile are dispersed in a solvent to form stable and uniform composite slurry, and the composite slurry is coated on a copper current collector. In the method for optimizing the performance of the lithium metal without the negative electrode, graphene oxide and polyacrylonitrile construct a uniform, porous and tough lithium-loving three-dimensional network through hydrogen-bond interaction, so that uniform nucleation sites are provided to promote uniform nucleation and plane growth of lithium, and lithium dendrite puncture is inhibited; the obtained composite modified current collector enables the battery to have high safety and long cycle life, and the preparation process is simple, environment-friendly and easy for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of negative electrode-free lithium metal battery technology, specifically relating to a copper current collector co-modified with graphene oxide and polyacrylonitrile for negative electrode-free lithium metal batteries and its preparation method. Background Technology

[0002] Lithium metal possesses extremely high theoretical specific capacity and low reduction potential. With increasing focus on high-energy-density batteries, research on lithium metal anodes remains a hot topic in the industry. However, the practical application of lithium metal batteries is consistently limited by key issues such as low reversibility, large volume changes, and significant safety hazards. The core reason lies in the high chemical reactivity between lithium metal and the electrolyte: on the one hand, it leads to irreversible lithium consumption, lithium dendrite growth, and the formation of dead lithium; on the other hand, it causes excessive electrolyte decomposition, forming an unstable solid electrolyte interface (SEI). Ultimately, this results in lower coulombic efficiency and poor cycle life, severely hindering the practical application of lithium metal batteries.

[0003] Electrodeless lithium metal batteries are considered a superior solution to the aforementioned problems. These batteries use copper as the negative electrode current collector, and because the initial electrode does not contain lithium metal, they possess excellent chemical stability, high safety, and low cost advantages. Copper foil, as the core substrate for lithium metal deposition in electrodeless lithium metal batteries, has a crucial influence on lithium deposition behavior and the formation of the solid electrolyte interface. The naturally occurring micro-roughness of the copper current collector surface induces preferential adsorption of lithium ions, forming uneven nucleation sites, which in turn leads to uneven lithium deposition, ultimately resulting in lithium dendrites. Lithium dendrites can pierce the separator, causing internal short circuits and becoming a core issue threatening the safety and lifespan of electrodeless lithium metal batteries. Therefore, modifying the surface of copper foil to regulate lithium deposition behavior is a key breakthrough for achieving high-performance electrodeless lithium metal batteries.

[0004] Currently, two types of coating materials have been used to modify copper current collectors: one type involves coating a copper substrate with lithiophilic materials (such as graphene, carbon nanotubes, and some metals that can form alloys with lithium) as nucleation seeds, leveraging their excellent electronic conductivity and lithiophilicity to guide uniform and dense lithium nucleation; the other type involves constructing a robust physical layer or artificial solid electrolyte interface film (such as polyethylene oxide film, polyvinylidene garnet composite film, etc.) on a copper substrate to stabilize the lithium deposition and stripping process through physical barriers. However, inherent solid electrolyte interface films are difficult to achieve smooth and uniform lithium deposition, and both existing modification schemes have limitations: a single lithiophilic material coating lacks sufficient mechanical strength to withstand volume changes during lithium deposition, making it prone to cracking and peeling; a single artificial interface film cannot simultaneously address both lithium-ion transport efficiency and nucleation guidance capabilities, failing to solve the dual problems of "uniform nucleation" and "dendritic suppression." Therefore, developing a negative electrode current collector for lithium metal batteries that combines high lithium affinity, high mechanical strength, structural stability, and simple preparation method has become a key technical problem that the industry urgently needs to solve. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing copper current collector modification technologies for electrodeless lithium metal batteries, and to provide a method for preparing a copper current collector synergistically modified with graphene oxide and polyacrylonitrile for electrodeless lithium metal batteries. Through the synergistic effect of graphene oxide and polyacrylonitrile, the following objectives are achieved: First, the lithium-affinity properties of graphene oxide guide the uniform and dense nucleation of lithium metal on the surface of the copper current collector; second, the excellent mechanical strength and toughness of polyacrylonitrile enhance the structural stability of the electrode coating, preventing cracking and peeling during drying and battery cycling, thus ensuring the integrity of the electrode structure; third, the synergistic effect of the two optimizes lithium deposition behavior, effectively suppressing lithium dendrite growth and improving the stability of the solid electrolyte interface (SEI), ultimately enabling the assembled electrodeless lithium metal battery to possess high electrochemical stability, high initial coulombic efficiency, and excellent cycle performance, comprehensively improving the overall electrochemical performance of the battery.

[0006] To achieve its objectives, the present invention employs the following technical solution: A method for preparing a copper current collector co-modified with graphene oxide and polyacrylonitrile for use in negative electrode-free lithium metal batteries comprises the following steps: Step 1: Select graphene oxide as the functional component, disperse it in a solvent, and use a circulating dispersion method combining ice bath ultrasonication and magnetic stirring to obtain a uniform and stable graphene oxide dispersion. Wherein: The graphene oxide is at least one of single-layer graphene oxide, few-layer graphene oxide, and multilayer graphene oxide. The surface of the graphene oxide is rich in oxygen-containing functional groups such as hydroxyl and carboxyl groups, which can achieve uniform distribution of lithium ions on the electrode surface through strong interaction with lithium ions, laying the foundation for uniform and dendrite-free lithium deposition.

[0007] The specific cyclic dispersion method is as follows: ultrasonic treatment for 30 minutes under ice bath conditions, followed by magnetic stirring for 30 minutes. This operation is considered as one cycle and is performed three times in total.

[0008] The solvent is at least one of water, ethanol, methanol, N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), ethylene glycol, aqueous acetone solution, aqueous ethanol solution, and aqueous methanol solution.

[0009] Step 2: Add polyacrylonitrile to the graphene oxide dispersion prepared in Step 1 according to a preset mass ratio, and continue stirring at room temperature until the polyacrylonitrile is completely dissolved to obtain a uniform and stable graphene oxide-polyacrylonitrile composite slurry. Wherein: The mass ratio of polyacrylonitrile to graphene oxide is 5-30:1; The stirring time is 10-12 h to ensure that the polyacrylonitrile is fully dissolved and forms a synergistic system with the graphene oxide molecules.

[0010] Step 3: Cut the copper foil to the preset size suitable for battery assembly. Wipe the surface of the copper foil repeatedly with anhydrous ethanol to remove oil, oxides, and impurities. Then allow it to air dry or blow dry to obtain a clean copper current collector substrate. The thickness of the copper foil is 6-20 µm.

[0011] Step 4: Uniformly coat the composite slurry obtained in Step 2 onto the surface of the pretreated copper current collector in Step 3, controlling the coating thickness; then place the coated copper current collector in an oven and dry it at a preset temperature to remove the solvent and cure the coating, thus obtaining the copper current collector synergistically modified with graphene oxide and polyacrylonitrile. Wherein: The coating thickness is 50-100 μm; The drying temperature is 80-100℃, and the drying time is 8-10 h.

[0012] Compared with existing technologies, the beneficial effects of this invention are reflected in: 1. This invention achieves a three-in-one functional optimization of "nucleation guidance, dendrite blocking, and ion transport" through the synergistic modification of graphene oxide and polyacrylonitrile. The surface of graphene oxide is rich in oxygen-containing functional groups such as hydroxyl and carboxyl groups, which form a strong interaction with lithium ions. This not only uniformly disperses lithium ions but also provides abundant and uniform nucleation sites, guiding the uniform and dense nucleation of lithium metal and preventing the irregular growth of lithium dendrites from the source. The dense film formed by the polyacrylonitrile polymer chains has excellent mechanical strength, which can physically block lithium dendrites from penetrating. At the same time, its nitrile groups can specifically coordinate with lithium ions to construct a rapid lithium ion transport channel, further promoting the uniform distribution and deposition of lithium ions, and ultimately achieving dendrite-free lithium deposition, completely solving the short-circuit safety hazard of negative electrode-less lithium metal batteries.

[0013] 2. In the copper current collector synergistically modified with graphene oxide and polyacrylonitrile of the present invention, polyacrylonitrile has both good adhesion and mechanical toughness. After being combined with graphene oxide, it can form a structurally stable coating, which effectively avoids the cracking and peeling problems caused by volume changes during drying or battery cycling of traditional single coatings, and ensures the integrity of the electrode structure. At the same time, the synergistic modification layer can induce the formation of a solid electrolyte interface (SEI) film with uniform composition and dense structure, reduce electrolyte decomposition and active lithium loss, and enable the negative electrode-free lithium metal battery to have higher cycle stability and longer service life.

[0014] 3. In the copper current collector synergistically modified with graphene oxide and polyacrylonitrile of the present invention, graphene oxide is an ultralight two-dimensional nanomaterial. The extremely thin coating formed by it hardly increases the overall weight and volume of the copper current collector. Compared with traditional metal-based or thick-film polymer modification layers, the current collector modified by the present invention can retain the energy density of the battery to the maximum extent, perfectly meeting the application requirements of new energy vehicles, energy storage power stations and other applications that require high range and high energy density.

[0015] 4. The preparation method of the present invention involves only simple processes such as dispersion, stirring, coating and drying. It does not require high-temperature sintering, complex equipment or harsh reaction conditions. The process is short, easy to operate and cost controllable. Moreover, the solvent used can be recycled and no harmful pollutants are generated. It is environmentally friendly and can achieve large-scale continuous production, significantly reducing the threshold for industrial application and having broad prospects for industrial transformation. Attached Figure Description

[0016] Figure 1 For a current density of 1 mA cm -2 The lithium plating amount is 0.5 mAh cm⁻¹ -2 At that time, the coulombic efficiency diagram of the half-cell assembled with copper current collectors obtained in each embodiment is shown as lithium plating / stripping. Detailed Implementation

[0017] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following content is merely illustrative and explanatory of the concept of the present invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the inventive concept or exceed the scope defined by the claims, all of which should fall within the protection scope of the present invention.

[0018] Example 1: Preparation of pure graphene oxide-modified copper current collector Step 1: Select 0.0025 g of monolayer graphene oxide as the functional component and add it to 1 mL of N,N-dimethylformamide (DMF) solvent; use a combined dispersion method of "30 min of sonication in an ice bath + 30 min of magnetic stirring" as one cycle, and perform three cycles in total to obtain a uniform and stable graphene oxide dispersion.

[0019] Step 2: Select a copper foil with a thickness of 10 µm and cut it into a suitable size of 14 mm × 14 mm; wipe the surface of the copper foil repeatedly with anhydrous ethanol 3 times to remove surface oil, oxides and impurities, and air dry to obtain a clean copper current collector substrate.

[0020] Step 3: Using a scraper with a 50 μm gap, uniformly coat the above graphene oxide dispersion onto the surface of the pretreated copper current collector, controlling the coating thickness to be 50 μm; then place the coated copper current collector in an oven and dry it at 80℃ for 10 h to remove the solvent and cure the coating, thus obtaining pure graphene oxide modified copper current collector.

[0021] Example 2: Preparation of pure polyacrylonitrile-modified copper current collector Step 1: Add 0.0250 g of polyacrylonitrile to 1 mL of DMF solvent and stir continuously at room temperature for 12 h until the polyacrylonitrile is completely dissolved to obtain a uniform and stable polyacrylonitrile dispersion.

[0022] Step 2: Select a copper foil with a thickness of 10 µm and cut it into a suitable size of 14 mm × 14 mm; wipe the surface of the copper foil repeatedly with anhydrous ethanol 3 times to remove surface oil, oxides and impurities, and air dry to obtain a clean copper current collector substrate.

[0023] Step 3: Using a scraper with a 50 μm gap, uniformly coat the polyacrylonitrile dispersion onto the surface of the pretreated copper current collector, controlling the coating thickness to be 50 μm; then place the coated copper current collector in an oven and dry it at 80℃ for 10 h to remove the solvent and cure the coating, thus obtaining the pure polyacrylonitrile modified copper current collector.

[0024] Example 3: Preparation of a composite modified copper current collector with a polyacrylonitrile / graphene oxide mass ratio of 10:1 Step 1: Select 0.0025 g of monolayer graphene oxide as the functional component and add it to 1 mL of N,N-dimethylformamide (DMF) solvent; use a combined dispersion method of "30 min of sonication in an ice bath + 30 min of magnetic stirring" as one cycle, and perform three cycles in total to obtain a uniform and stable graphene oxide dispersion.

[0025] Step 2: Add 0.0250 g of polyacrylonitrile to the graphene oxide dispersion and stir continuously at room temperature for 12 h until the polyacrylonitrile is completely dissolved to obtain a uniform and stable graphene oxide-polyacrylonitrile composite slurry dispersion.

[0026] Step 3: Select a copper foil with a thickness of 10 µm and cut it into a suitable size of 14 mm × 14 mm; wipe the surface of the copper foil repeatedly with anhydrous ethanol 3 times to remove surface oil, oxides and impurities, and air dry to obtain a clean copper current collector substrate.

[0027] Step 4: Using a scraper with a 50 μm gap, the above composite slurry is uniformly coated onto the surface of the pretreated copper current collector, and the coating thickness is controlled to be 50 μm. Then, the coated copper current collector is placed in an oven and dried at 80℃ for 10 hours to remove the solvent and cure the coating, thus obtaining the copper current collector synergistically modified with graphene oxide and polyacrylonitrile (the mass ratio of polyacrylonitrile to graphene oxide is 10:1).

[0028] Example 4: Preparation of a composite modified copper current collector with a polyacrylonitrile / graphene oxide mass ratio of 20:1 Step 1: Select 0.0025g of monolayer graphene oxide as the functional component and add it to 1 mL of N,N-dimethylformamide (DMF) solvent; use a combined dispersion method of "30 min of sonication in an ice bath + 30 min of magnetic stirring" as one cycle, and perform three cycles in total to obtain a uniform and stable graphene oxide dispersion.

[0029] Step 2: Add 0.0500 g of polyacrylonitrile to the graphene oxide dispersion and stir continuously at room temperature for 12 h until the polyacrylonitrile is completely dissolved to obtain a uniform and stable graphene oxide-polyacrylonitrile composite slurry dispersion.

[0030] Step 3: Select a copper foil with a thickness of 10 µm and cut it into a suitable size of 14 mm × 14 mm; wipe the surface of the copper foil repeatedly with anhydrous ethanol 3 times to remove surface oil, oxides and impurities, and air dry to obtain a clean copper current collector substrate.

[0031] Step 4: Using a scraper with a 50 μm gap, the above composite slurry is uniformly coated onto the surface of the pretreated copper current collector, and the coating thickness is controlled to be 50 μm. Then, the coated copper current collector is placed in an oven and dried at 80℃ for 10 hours to remove the solvent and cure the coating, thus obtaining the copper current collector synergistically modified with graphene oxide and polyacrylonitrile (the mass ratio of polyacrylonitrile to graphene oxide is 20:1).

[0032] Battery Assembly and Performance Testing: CR2032 half-cells were assembled in an argon (Ar)-filled glove box in the following order: negative electrode shell → lithium sheet → electrolyte → separator → modified copper current collector → positive electrode shell. The separator was a Celgard 2400 polypropylene membrane, and the electrolyte was 1 M lithium bis(trifluoromethanesulfonyl)imide dissolved in 1,3-dioxolane / ethylene glycol dimethyl ether (volume ratio 1:1) with 2 wt% lithium nitrate as an additive.

[0033] The lithium deposition / stripping cycle performance of the battery was tested using the Blue Battery Testing System. The test conditions were: current density of 1 mA cm⁻¹. -2 The lithium plating amount is 0.5 mAh cm⁻¹ -2 At that time. The test results showed: The half-cell assembled with the blank control group (pure copper foil) had an initial coulombic efficiency of only 80.72% and extremely poor cycle stability. After 50 cycles, the coulombic efficiency (CE) fluctuated drastically. The main reason was that the micro-roughness of the copper foil surface caused disordered growth of lithium dendrites, which led to the loss of active lithium and continuous damage to the SEI film. The half-cell of Example 1 (pure graphene oxide modified) showed fluctuations in CE after 25 cycles, indicating that the mechanical strength of the single graphene oxide coating was insufficient during cycling, the coating was prone to cracking, and it could not suppress lithium dendrite piercing for a long time. The half-cell of Example 2 (pure polyacrylonitrile modification) had an initial coulombic efficiency of 93.88%, which was better than that of pure copper foil. However, its cycle stability was lower than that of the composite modification group. This is because although the polyacrylonitrile film can provide mechanical barriers, it lacks sufficient lithiophilic nucleation sites, resulting in low lithium-ion transport efficiency and insufficient uniformity of lithium deposition. The composite modified copper current collector of Example 3 (polyacrylonitrile / graphene oxide mass ratio 10:1) exhibited the best electrochemical performance: the initial coulombic efficiency reached 85.13%, which was significantly higher than that of pure copper foil and single-component modified group; and the cycle stability was excellent, with the coulombic efficiency remaining stable at 98.06% (average CE=97.5%) after 150 cycles. Example 4 (polyacrylonitrile / graphene oxide mass ratio 20:1) composite modified copper current collector had an initial coulombic efficiency of 92.22%, which was better than that of pure copper foil. However, the cycle stability was poor, and the CE fluctuated drastically after 27 cycles. It is speculated that this was because the proportion of polyacrylonitrile was too high. Although the mechanical strength was further improved, the lithiophilic sites of graphene oxide were partially covered, and the lithium-ion transport efficiency decreased slightly.

[0034] The above results demonstrate that the synergistic modification effect of graphene oxide and polyacrylonitrile (PAI) can provide uniform nucleation sites and optimize lithium-ion distribution through the lithium-philic functional groups of graphene oxide, while the excellent mechanical strength of PAI can suppress lithium dendrite penetration. Furthermore, the two work synergistically to induce the formation of a dense and stable SEI film, significantly reducing active lithium loss and electrolyte decomposition. In contrast, single-component modification can only address some of the problems and cannot simultaneously achieve both high initial CE and long-term cycle stability. The synergistic effect is optimal when the mass ratio of PAI to graphene oxide is 10:1, resulting in a significant improvement in the overall electrochemical performance of the battery.

[0035] The above description is merely a preferred embodiment of the present invention, and while it is quite specific and detailed, it should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and equivalent substitutions without departing from the principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a copper current collector co-modified with graphene oxide and polyacrylonitrile for use in a cathodeless lithium metal battery, characterized in that, Follow these steps: Step 1: Disperse graphene oxide in a solvent to obtain a graphene oxide dispersion; Step 2: Add polyacrylonitrile to the graphene oxide dispersion from Step 1, and stir continuously at room temperature until the polyacrylonitrile is completely dissolved to obtain graphene oxide-polyacrylonitrile composite slurry. Step 3: Use copper foil as a current collector, wipe the surface with anhydrous ethanol to remove impurities, and then let it air dry; Step 4: The graphene oxide-polyacrylonitrile composite slurry from Step 2 is uniformly coated onto the surface of the pretreated copper current collector. After drying, a copper current collector synergistically modified with graphene oxide and polyacrylonitrile is obtained.

2. The preparation method according to claim 1, characterized in that: In step 1, graphene oxide is treated using a circulating dispersion method that combines ice bath ultrasonic and magnetic stirring.

3. The preparation method according to claim 1, characterized in that: In step 1, the solvent is at least one of water, ethanol, methanol, N,N-dimethylformamide, N-methylpyrrolidone, ethylene glycol, aqueous acetone solution, aqueous ethanol solution, and aqueous methanol solution.

4. The preparation method according to claim 1, characterized in that: In step 2, the mass ratio of polyacrylonitrile to graphene oxide is 5-30:

1.

5. The preparation method according to claim 1, characterized in that: In step 2, the stirring time is 10-12 h.

6. The preparation method according to claim 1, characterized in that: In step 3, the thickness of the copper foil is 6-20 µm.

7. The preparation method according to claim 1, characterized in that: In step 4, the coating thickness is 50-100 μm.

8. The preparation method according to claim 1, characterized in that: In step 4, the drying temperature is 80-100℃ and the drying time is 8-10 h.

9. A copper current collector synergistically modified with graphene oxide and polyacrylonitrile prepared by any one of claims 1 to 8.

10. A cathodeless lithium metal battery using a copper current collector co-modified with graphene oxide and polyacrylonitrile as described in claim 9 as the cathode.

Images