A black phosphorus coating modified magnesium metal negative electrode and a preparation method and application thereof

Abstract

The application provides a magnesium metal negative electrode modified by a black phosphorus coating, which comprises: metal magnesium; and a coating arranged on the surface of the metal magnesium. 2+ The application utilizes the magnesium affinity and excellent magnesium ion conduction characteristics of the black phosphorus coating to construct uniform nucleation sites and fast Mg conduction layers, thereby realizing uniform nucleation and growth process, and further greatly reducing the metal magnesium deposition overpotential, and effectively improving the cycle life of the metal magnesium negative electrode. The black phosphorus coating in the application can reduce the production process cost of the metal magnesium battery, and is suitable for large-scale commercial production and use. The black phosphorus coating in the application can be compatible with the existing magnesium ion battery electrolyte, such as APC electrolyte, and has a good induction deposition effect on the metal magnesium negative electrode.

Description

Technical Field

[0001] This invention belongs to the field of magnesium metal battery technology, and particularly relates to a magnesium metal anode modified with black phosphorus coating, its preparation method and application. Background Technology

[0002] Magnesium metal (redox potential 2.37V vs. standard hydrogen electrode) has a high capacity of 3833 mAh cm⁻¹. -3 With its high specific capacity and abundant reserves of up to 2.7% in the Earth's crust, magnesium anodes offer advantages such as low cost and environmental friendliness, making them an ideal high-energy-density anode material for next-generation batteries. However, the biggest problem with magnesium anodes in practical applications is that, on the one hand, the surface of magnesium anodes readily reacts with organic electrolytes to form a passivation film, hindering the formation of Mg... 2+ Reversible deposition. On the other hand, Mg 2+ Due to its high charge density and polarity, magnesium deposition typically involves a large deposition overpotential and relatively slow reaction kinetics. Furthermore, the magnesium deposits on the original magnesium anode surface usually exhibit spherical or island-like nucleation formations. As the deposition capacity accumulates, the deposited magnesium develops a loose structure, exacerbating side reactions and leading to problems such as electrode pulverization, low coulombic efficiency, and poor cycle life.

[0003] To address the above issues, existing solutions mostly involve modification and the development of new electrolyte systems. These often involve stringent preparation conditions and expensive organic solvents and additives, and typically fail to effectively improve the nucleation and growth mechanisms of magnesium metal. Therefore, current rudimentary magnesium metal anodes and corresponding modification strategies cannot meet the technical and economic requirements of practical magnesium metal battery applications. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a magnesium metal anode modified with black phosphorus coating, its preparation method and application. The magnesium metal anode modified with black phosphorus coating provided by the present invention has good performance.

[0005] This invention provides a magnesium metal anode modified with a black phosphorus coating, comprising:

[0006] Magnesium metal;

[0007] A coating disposed on the surface of the magnesium metal;

[0008] The coating contains black phosphorus nanosheets.

[0009] Preferably, the thickness of the magnesium metal is 5 to 1000 μm.

[0010] Preferably, the thickness of the black phosphorus nanosheets is 1 to 100 nm.

[0011] Preferably, the thickness of the coating is 10 nm to 50 μm.

[0012] This invention provides a method for preparing a magnesium metal anode modified with a black phosphorus coating as described in the above-mentioned technical solution, comprising:

[0013] The slurry is coated onto the surface of metallic magnesium;

[0014] The slurry comprises: black phosphorus nanosheets, binder, and solvent.

[0015] Preferably, the method for preparing the black phosphorus nanosheets includes:

[0016] The bulk black phosphorus is mixed with a solvent and then peeled off under ultrasonic waves.

[0017] Preferably, the solvent is selected from one or more of N-methylpyrrolidone, N,N-dimethylformamide, methanol, and ethanol.

[0018] The mass ratio of the bulk black phosphorus to the solvent is 1:(0.5~1.5).

[0019] Preferably, the power of the ultrasonic wave is 250-350W; the ablation time is 10-15 hours; the ablation is performed under an argon atmosphere; and the ablation temperature is below 15°C.

[0020] Preferably, the adhesive is polyvinylidene fluoride; the solvent is N-methylpyrrolidone.

[0021] The present invention provides a battery comprising: a magnesium metal negative electrode modified with a black phosphorus coating as described in the above technical solution.

[0022] This invention utilizes the magnesium affinity and excellent magnesium ion conductivity of black phosphorus coating to construct uniform nucleation sites and rapid Mg formation on the surface of metallic magnesium anodes. 2+ The conductive layer enables uniform nucleation and growth, significantly reducing the overpotential of magnesium deposition and effectively improving the cycle life of the magnesium anode. The black phosphorus coating of this invention utilizes simple processes and implementation conditions, reducing the production cost of magnesium batteries and making it suitable for large-scale commercial production and use. The black phosphorus coating of this invention is compatible with existing magnesium-ion battery electrolytes, such as APC, and effectively induces deposition on the magnesium anode. Attached Figure Description

[0023] Figure 1 The microstructure of the black phosphorus surface coating layer of the black phosphorus@magnesium metal anode prepared in Example 1 of this invention;

[0024] Figure 2 The microstructure of the black phosphorus cross section of the black phosphorus@magnesium metal anode prepared in Example 1 of this invention;

[0025] Figure 3 This is a comparison of the cycle performance of the black phosphorus@magnesium metal anode symmetric battery prepared in Example 1 of the present invention and the original magnesium metal symmetric battery;

[0026] Figure 4 This is a comparison chart of the rate performance of the black phosphorus@magnesium metal anode symmetric battery prepared in Example 1 of the present invention and the original magnesium metal symmetric battery;

[0027] Figure 5 This is a microscopic morphology diagram of the magnesium deposition on the surface of the original magnesium anode in Example 2 of the present invention;

[0028] Figure 6 This is a microscopic morphology image of magnesium deposition on the surface of the black phosphorus@magnesium anode prepared in Example 2 of the present invention. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] This invention provides a magnesium metal anode modified with a black phosphorus coating, comprising:

[0031] Magnesium metal;

[0032] A coating applied to the surface of the magnesium metal.

[0033] In this invention, the thickness of the magnesium metal is preferably 5-1000 μm, more preferably 10-800 μm, more preferably 10-600 μm, more preferably 10-400 μm, more preferably 10-200 μm, and most preferably 10-100 μm.

[0034] In this invention, the coating preferably comprises: black phosphorus nanosheets.

[0035] In this invention, the thickness of the black phosphorus nanosheets is preferably 1-100 nm, more preferably 5-80 nm, even more preferably 5-60 nm, even more preferably 5-40 nm, and most preferably 5-20 nm.

[0036] In this invention, the thickness of the coating is preferably 10nm to 50μm, more preferably 50nm to 40μm, even more preferably 100nm to 30μm, even more preferably 500nm to 20μm, even more preferably 0.5 to 10μm, and most preferably 0.5 to 5μm.

[0037] This invention provides a method for preparing a magnesium metal anode modified with a black phosphorus coating, comprising:

[0038] The slurry is coated onto the surface of metallic magnesium;

[0039] The slurry comprises: black phosphorus nanosheets, binder, and solvent (first solvent).

[0040] In this invention, the thickness of the black phosphorus nanosheets is preferably 1-100 nm, more preferably 5-80 nm, even more preferably 5-60 nm, even more preferably 5-40 nm, and most preferably 5-20 nm.

[0041] In this invention, the preferred method for preparing the black phosphorus nanosheets includes:

[0042] Solvent-assisted stripping technology was used to strip bulk black phosphorus into two-dimensional black phosphorus sheets.

[0043] In this invention, the method for preparing the black phosphorus nanosheets more preferably includes:

[0044] The bulk black phosphorus is mixed with a solvent (second solvent) and then peeled off under the action of ultrasound.

[0045] In this invention, the solvent (second solvent) is preferably selected from one or a mixture of several solvents such as N-methylpyrrolidone, N,N-dimethylformamide, methanol, and ethanol.

[0046] In this invention, the mass ratio of the bulk black phosphorus to the solvent (second solvent) is preferably 1:(0.5-1.5), more preferably 1:(0.8-1.2), and most preferably 1:1.

[0047] In this invention, the power of the ultrasonic wave is preferably 250-350W, more preferably 280-320W, and most preferably 300W; the peeling time is preferably 10-15h, more preferably 12h; the peeling is preferably carried out under an argon atmosphere; the peeling temperature is preferably below 15℃, more preferably 5-10℃, and most preferably 10℃.

[0048] In this invention, the process after the stripping is completed preferably further includes:

[0049] The obtained exfoliated product was centrifuged, washed, and dried to obtain black phosphorus nanosheets.

[0050] In this invention, the centrifugation speed is preferably 6000-8000 rpm, more preferably 6500-7500 rpm, and most preferably 7000 rpm; the centrifugation preferably results in a dispersion. In this invention, the washing solvent is preferably selected from acetone or ethanol; the number of washings is preferably 3-5 times, more preferably 4 times. In this invention, the drying is preferably vacuum drying, preferably drying in a vacuum oven; the drying time is preferably 10-15 hours, more preferably 12 hours.

[0051] In this invention, the binder is preferably polyvinylidene fluoride. In this invention, the first solvent is preferably N-methylpyrrolidone. In this invention, the mass ratio of the black phosphorus nanosheets to the binder is preferably (8-10):1, more preferably 9:1; the mass ratio of the black phosphorus nanosheets to the first solvent is preferably (90-10):(5-1), more preferably (20-80):(2-4), and even more preferably (30-60):3.

[0052] In this invention, the coating method is preferably blade coating; the coating thickness is preferably 10nm to 50μm, more preferably 50nm to 40μm, more preferably 100nm to 30μm, more preferably 500nm to 20μm, more preferably 0.5 to 10μm, and most preferably 0.5 to 5μm; the coating thickness can be adjusted by adjusting the slurry viscosity and the blade height.

[0053] In this invention, the magnesium metal is preferably a polished magnesium metal surface.

[0054] In this invention, the coating process preferably further includes:

[0055] Dry it.

[0056] In this invention, the drying is preferably oven drying, and the drying is preferably carried out in a vacuum oven; the drying temperature is preferably 70-90°C, more preferably 75-85°C, and most preferably 80°C; the drying time is preferably 10-15 hours, and more preferably 12 hours.

[0057] In this invention, the drying process preferably further includes:

[0058] The dried product is cut into circular electrode pieces.

[0059] In this invention, the diameter of the circular electrode is preferably 10-16 mm, more preferably 11-15 mm, and most preferably 12-14 mm.

[0060] The present invention provides a battery comprising: a magnesium metal negative electrode modified with a black phosphorus coating as described in the above technical solution.

[0061] In this invention, the method for preparing the battery preferably includes:

[0062] The magnesium metal negative electrode modified with the black phosphorus coating was transferred to a glove box for symmetrical battery assembly.

[0063] In this invention, the method for preparing the battery preferably includes:

[0064] Step 1: Using solvent-assisted exfoliation technology, bulk black phosphorus is exfoliated into two-dimensional black phosphorus sheets. The bulk black phosphorus and auxiliary solvent are mixed at a mass ratio of 1:1 and exfoliated under ultrasonic (300W) for 12 hours. The entire exfoliation process is carried out under an argon atmosphere, with the temperature maintained below 15℃. After ultrasonication, the resulting dispersion is centrifuged at 7000 rpm and washed 3-5 times with a cleaning solvent. The prepared black phosphorus nanosheets are collected and dried in a vacuum oven for 12 hours. The auxiliary solvent used for exfoliation can be one or a mixture of several solvents such as N-methylpyrrolidone, N,N-dimethylformamide, methanol, and ethanol. The cleaning solvent can be acetone or ethanol.

[0065] Step 2: Mix black phosphorus nanosheets and binder in a 9:1 mass ratio in a suitable solvent to form a uniform coating slurry. Add 100mg of black phosphorus and polyvinylidene fluoride to 2mL of N-methylpyrrolidone and grind thoroughly to prepare a uniform coating slurry. Apply the slurry to the polished magnesium metal surface and then dry it in a vacuum oven at 80℃ for more than 12 hours. The coating thickness can be adjusted by adjusting the viscosity of the slurry and the height of the scraper.

[0066] Step 3: Transfer the dried black phosphorus-modified magnesium anode to a glove box, cut it into circular electrodes of the corresponding diameter, and assemble symmetrical cells to evaluate the cycle and rate performance of the black phosphorus-modified magnesium symmetrical cells; compare the assembled and polished original magnesium symmetrical cells and evaluate their cycle and rate performance.

[0067] The key to this invention lies in the black phosphorus@magnesium metal anode with a black phosphorus coating, the black phosphorus coating slurry applied to the magnesium metal anode, the black phosphorus coating slurry formulation and the black phosphorus coating composite method; and the magnesium metal battery, magnesium ion battery and hybrid ion battery involving magnesium ions constructed using the black phosphorus@magnesium metal anode.

[0068] Example 1

[0069] Bulk black phosphorus and N-methylpyrrolidone were mixed at a mass ratio of 1:1 and ultrasonically exfoliated (300W) for 12 hours under an argon atmosphere while maintaining the temperature at 10℃. After ultrasonication, the resulting dispersion was centrifuged at 7000 rpm and washed 3-5 times with a cleaning solvent. The prepared black phosphorus nanosheets were collected and dried in a vacuum oven for 12 hours.

[0070] 45 mg of the prepared black phosphorus nanosheets and 5 mg of polyvinylidene fluoride were added to 1 mL of N-methylpyrrolidone and thoroughly ground to prepare a uniform coating slurry. This slurry was then coated onto a polished magnesium metal surface and dried in a vacuum oven at 80°C for at least 12 hours, with the coating thickness controlled at 2 μm. Figure 1 and Figure 2 As shown;

[0071] The dried black phosphorus-modified magnesium anode was transferred to a glove box, cut into 12mm diameter circular electrodes, and assembled into a black phosphorus@magnesium symmetric cell.

[0072] Comparative experiment of Example 1: After polishing and drying the original magnesium metal negative electrode, it was transferred to a glove box, cut into 12mm circular electrodes of the corresponding diameter, and assembled into a magnesium metal symmetrical battery.

[0073] The symmetrical battery prepared in Example 1 was subjected to constant current charge-discharge cycle testing. The testing method was as follows: a current density of 2 mA cm⁻¹ was used. -2 Perform a 1-hour cycle of charging and discharging, with a battery resting step between the charging and discharging steps, and a resting time of 10 seconds.

[0074] The test results showed that the symmetric lithium battery using a black phosphorus-modified magnesium anode achieved a current density of 2 mA cm⁻¹. -2 The surface capacity is 2mAh cm -2 The initial deposition overpotential was only 0.81V, and it could cycle stably for 1720 hours. A comparative experiment was conducted using a symmetric lithium-ion battery with pristine magnesium metal at a current density of 2 mA cm⁻¹. -2 The surface area is 2cm³ -2 The initial deposition overpotential reached 1.91V, and a short circuit occurred after only 502 hours of stable cycling.

[0075] Example 2

[0076] Bulk black phosphorus and N-methylpyrrolidone were mixed at a mass ratio of 1:1 and ultrasonically exfoliated (300W) for 12 hours under an argon atmosphere while maintaining the temperature at 10℃. After ultrasonication, the resulting dispersion was centrifuged at 7000 rpm and washed 3-5 times with a cleaning solvent. The prepared black phosphorus nanosheets were collected and dried in a vacuum oven for 12 hours.

[0077] Add 45 mg of the black phosphorus nanosheets prepared above and 5 mg of polyvinylidene fluoride to 1 mL of N-methylpyrrolidone, grind thoroughly to prepare a uniform coating slurry, scrape the slurry onto the polished magnesium metal surface, and then dry it in a vacuum oven at 80°C for more than 12 hours, with the coating thickness controlled at 2 μm.

[0078] The dried black phosphorus-modified magnesium anode was transferred to a glove box, cut into 12mm diameter circular electrodes, and assembled into a symmetrical cell.

[0079] Example 2 Comparative Experiment: After polishing and drying the original magnesium metal negative electrode, it was transferred to a glove box, cut into 12mm diameter circular electrodes, and assembled into a magnesium metal symmetrical battery.

[0080] The rate performance of the symmetric battery prepared in Example 2 was tested using the following method: charge and discharge cycles were performed for 1 hour at different current densities, followed by 5 cycles at each current density. A 10-second rest period was included between the charge and discharge cycles. The current density gradients were increased, specifically 1, 2.5, 5, 10, 20, 40, 50, and 60 mA cm⁻¹. -2 Increase sequentially.

[0081] The test results showed that the symmetrical cell using a black phosphorus-modified magnesium anode operated at a current density of 60 mA cm⁻¹. -2 The surface capacity is 60mAh cm -2 A short circuit occurred. A comparative experiment was conducted using a symmetrical magnesium battery with pristine metallic magnesium at a current density of 40 mA / cm². -2 The surface area is 40cm² -2 A short circuit occurred.

[0082] The magnesium deposition in the black phosphorus-modified magnesium anode exhibits a uniform, dense, and smooth microstructure. In contrast, the magnesium deposition on the original magnesium surface shows uneven, spherical shapes with random distribution, such as... Figure 5 and Figure 6 As shown.

[0083] The black phosphorus modification layer provided by this invention significantly reduces the initial deposition overpotential of metallic magnesium. The constructed black phosphorus-modified metallic magnesium anode symmetric cell achieves an initial overpotential of 0.81V, compared to 1.96V for the original metallic magnesium anode. Figure 4 As shown. Meanwhile, the black phosphorus-modified magnesium anode can achieve a stable cycle life of 1720 hours, which is 3.4 times that of the original magnesium anode in the comparative experiment. Figure 3 As shown in the figure. Rate performance results show that the short-circuit current and short-circuit capacity of the black phosphorus-modified magnesium anode are 60 mA and 60 cm⁻¹, respectively. -2 and 60mAh cm -2 This is significantly higher than the short-circuit current and short-circuit capacity (40 mA cm⁻¹) of the original magnesium anode in the comparative test. -2 and 40mAh cm -2Furthermore, comparing the scanning electron microscopy images of the black phosphorus-modified magnesium anode after disassembly and the original magnesium anode reveals that the magnesium deposition on the surface of the black phosphorus-modified magnesium anode exhibits a smooth and uniform microstructure; while the magnesium deposition on the surface of the original magnesium anode shows a highly non-uniform microstructure with randomly distributed, spherical-like deposits of unequal sizes. The uniform and smooth microstructure of the magnesium deposition indicates that the black phosphorus-modified magnesium anode has uniform nucleation sites and electric field distribution, further proving the magnesium affinity of black phosphorus.

[0084] While the invention has been described and illustrated with reference to specific embodiments thereof, such description and illustration are not intended to limit the invention. It will be readily understood by those skilled in the art that various changes may be made to suit particular circumstances, materials, compositions, substances, methods, or processes to the objectives, spirit, and scope of this application without departing from the true spirit and scope of the invention as defined by the appended claims. All such modifications are intended to be within the scope of the appended claims. Although the methods disclosed herein have been described with reference to specific operations performed in a particular order, it should be understood that these operations may be combined, subdivided, or reordered to form equivalent methods without departing from the teachings of the invention. Therefore, unless specifically indicated herein, the order and grouping of operations are not a limitation of this application.

Claims

1. A magnesium metal anode modified by a black phosphorus coating, comprising: metallic magnesium; a coating disposed on the surface of the metallic magnesium; the coating contains black phosphorus nanosheets with a thickness of 1-100 nm; the black phosphorus nanosheets are prepared by: mixing bulk black phosphorus and a solvent and then performing exfoliation under the action of ultrasonic waves.

2. The black phosphorus coating-modified magnesium metal anode of claim 1, wherein, the thickness of the metallic magnesium is 5-1000 μm.

3. The black phosphorus coating-modified magnesium metal anode of claim 1, wherein, the thickness of the coating is 10 nm-50 μm. 4.A method for preparing the magnesium metal anode modified by a black phosphorus coating according to claim 1, comprising: coating a slurry on the surface of the metallic magnesium; the slurry comprises black phosphorus nanosheets, a binder and a solvent; the thickness of the black phosphorus nanosheets is 1-100 nm; the black phosphorus nanosheets are prepared by: mixing bulk black phosphorus and a solvent and then performing exfoliation under the action of ultrasonic waves.

5. The method of claim 4, wherein, the solvent is selected from one or more of N-methylpyrrolidone, N, N-dimethylformamide, methanol and ethanol; the mass ratio of the bulk black phosphorus to the solvent is 1: (0.5-1.5).

6. The method of claim 4, wherein, the power of the ultrasonic waves is 250-350 W;the exfoliation time is 10-15 h;the exfoliation is performed under an argon atmosphere at a temperature below 15℃.

7. The method of claim 4, wherein, the binder is polyvinylidene fluoride;the solvent is N-methylpyrrolidone.

8. A battery comprising: the magnesium metal anode modified by a black phosphorus coating according to claim 1.

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