High-efficiency and stable magnesium metal negative electrode and modification method thereof

Abstract

The application discloses a kind of high-efficiency stable magnesium metal negative electrode and its modification method, it is related to the technical field of rechargeable magnesium battery, it includes the following steps: 1) in atmospheric / protection atmosphere environment, indium trichloride hydrate is dissolved in organic solvent, stirs overnight, and indium trichloride solution is prepared;2) in atmospheric / protection atmosphere environment, metal magnesium foil one side is pasted with adhesive tape, is completely soaked in indium trichloride solution, forms a layer of solid interface protective layer on the surface of metal magnesium foil in situ, is washed, and the magnesium metal negative electrode including magnesium metal foil and the artificial interface layer attached to the surface of the magnesium metal foil is obtained.The modification method is low to the roughness of metal magnesium foil surface and the external environment requirement during preparation process, the whole process is simple, fast, safe and efficient, low energy consumption, with industrialization prospect.The prepared magnesium metal negative electrode has good magnesium ion conductivity, so that the capacity and cycle life of magnesium metal battery are improved.

Description

Technical Field

[0001] This invention belongs to the field of rechargeable magnesium battery technology, specifically relating to a high-efficiency and stable magnesium metal anode and its modification method. Background Technology

[0002] With socio-economic development, people's demand for energy is increasing. The massive consumption of traditional fossil fuels has led to global warming, environmental degradation, and energy depletion, seriously threatening sustainable development. With the innovative development of new energy technologies, there is an urgent need for renewable energy to replace fossil fuels. Energy conversion and storage will be the core of new energy development and an effective means to achieve carbon neutrality. Lithium-ion batteries (LIBs), with their excellent cycle performance, are the most mature electrochemical energy storage technology and have been widely used in portable devices, electric vehicles, and grid energy storage. However, lithium resource shortages, high manufacturing costs, and safety issues hinder their application in large-scale energy storage. Electrode materials based on other metal ions hold promise for further expanding the development of rechargeable batteries, such as those with a unit price of (Na+). + and K + ) and polyvalent (Mg 2+ Ca 2+ Al 3+ and Zn 2+ The application of ions is expected to replace lithium-ion batteries, further expanding the application scenarios of batteries and reducing usage costs at the same time.

[0003] Among them, metallic Mg has a low standard electrode potential (-2.37 V SHE) and a high theoretical volumetric capacity (3832 mAh cm⁻¹). -3 Magnesium, with its abundant resources and excellent chemical stability, possesses great potential as a negative electrode material for rechargeable batteries. Firstly, magnesium is abundant in the Earth's crust, with an abundance of 23,000 ppm, approximately 1300 times that of elemental Li (18 ppm). This rich resource provides a solid foundation for the large-scale application of rechargeable magnesium batteries (RMB). Secondly, magnesium ions have a similar radius to lithium ions but can carry two charges, resulting in a volumetric capacity density that is almost twice that of lithium anodes (2062 mAh cm⁻¹). -3 Third, during the deposition process, due to the low diffusion barrier, Mg ions tend to deposit to form a smooth and flat metal layer. This greatly avoids the problem of dendrite formation common in metals like lithium / sodium, thus possessing intrinsic safety characteristics. Therefore, rechargeable magnesium batteries are expected to replace traditional lithium-ion batteries and become a potential candidate product in future rechargeable batteries.

[0004] However, magnesium readily forms passivation films in various solvents, salts, and contaminants, completely preventing any electrochemical reactions. This leads to significant voltage hysteresis and low coulombic efficiency (CE) in magnesium anodes, severely shortening the cycle life of magnesium batteries. Furthermore, while early researchers believed that Mg anodes exhibited uniform deposition / stripping behavior during electrochemical processes, recent studies have shown that due to the inhomogeneity of magnesium and its alloy surfaces and corrosion issues with Cl-containing electrolytes, Mg stripping / deposition is not as uniform as expected. Therefore, developing a simple and efficient method for preparing magnesium anodes is crucial to meet the demand for mass production of high-quality magnesium anodes for rechargeable magnesium batteries. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the main objective of this invention is to provide a highly efficient and stable magnesium metal anode and its modification method, which can alleviate passivation of the magnesium metal anode, guide uniform deposition of magnesium ions, and achieve highly reversible deposition and stripping.

[0006] The objective of this invention is achieved through the following technical solution: A method for modifying a high-efficiency and stable magnesium metal anode includes the following steps: 1) Under atmospheric / protective atmosphere, indium trichloride hydrate (InCl3·xH2O) is dissolved in an organic solvent and stirred overnight to prepare an indium trichloride solution; 2) Under atmospheric / protective atmosphere, apply tape to one side of the magnesium foil and immerse it completely in indium trichloride solution to form a solid interface protective layer on the surface of the magnesium foil in situ. After cleaning, the magnesium metal negative electrode is obtained.

[0007] In some specific embodiments, the indium trichloride hydrate (InCl3·xH2O) mentioned in step 1) includes indium trichloride tetrahydrate (InCl3·4H2O), and the concentration of the indium trichloride solution is 0.05-0.6 mol / L.

[0008] In some specific embodiments, the organic solvent mentioned in step 1) includes, but is not limited to, one or more of acetonitrile, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and N-methylpyrrolidone.

[0009] In some specific implementations, the soaking process parameters in step 2) are: soaking time of 5-60 seconds.

[0010] In some specific embodiments, the process also includes pretreatment of the magnesium foil, specifically: cutting the magnesium foil to a suitable size, polishing it, and rinsing it with anhydrous ethanol to remove surface contaminants in an atmospheric / protective atmosphere.

[0011] In some specific embodiments, the cleaning in step 2) specifically involves repeatedly cleaning the magnesium foil with the same organic solvent as in step 1) under atmospheric / protective atmosphere conditions, followed by vacuum drying to obtain a magnesium metal negative electrode with a protective layer.

[0012] Furthermore, the process parameters for vacuum drying are: vacuum drying temperature of 50-70℃ and time of 6-12h.

[0013] In some specific embodiments, the atmospheric environment is characterized by an ambient humidity of less than 70%; the protective atmosphere is an inert gas.

[0014] Furthermore, the inert gas is one of argon, neon, or helium.

[0015] A high-efficiency and stable magnesium metal anode prepared according to the aforementioned method includes a magnesium foil and a protective layer attached to the surface of the magnesium foil.

[0016] Compared with the prior art, the present invention has at least the following advantages: The method for modifying magnesium metal anode provided by the present invention involves dissolving indium trichloride hydrate in an organic solvent under atmospheric / protective atmosphere conditions and stirring overnight to obtain an indium trichloride solution; then, applying adhesive tape to one side of a magnesium foil and immersing it completely in the indium trichloride solution to form a solid interface protective layer in situ on the surface of the magnesium foil; and finally cleaning to obtain a magnesium metal anode. The operation method of this invention is simple, facilitating large-scale production and quantitative control. By immersing magnesium foil in an indium trichloride hydrate / organic solution to form an artificial interface layer mainly composed of inorganic matter (In / MgCl2), the entire process has low requirements for the external environment and the roughness of the magnesium foil. In addition, the partial hydrolysis of indium trichloride hydrate makes the indium trichloride solution acidic, which eliminates the oxide layer of pure magnesium foil in the air, greatly reducing the reaction time. At the same time, it has low requirements for the surface of the magnesium foil (no additional grinding and polishing is required). Simultaneously, by using a simple ion exchange reaction, an artificial interface layer is formed in situ on the surface of the magnesium foil, effectively reducing the passivation behavior of the magnesium metal anode. Furthermore, since the artificial interface layer has a large number of magnesium-loving sites, good magnesium ion conductivity, and electronic insulation, it can effectively regulate the deposition / stripping behavior of magnesium ions, thereby improving the electrochemical performance of magnesium metal batteries, such as capacity and cycle life.

[0017] The modification method for magnesium metal anode of the present invention constructs a good modified coating layer on the surface of magnesium metal through chemical methods. The reaction time is short, requiring only 5-60 seconds. The entire preparation process is simple and has high production efficiency.

[0018] Furthermore, the magnesium anode of the present invention can reduce the interface resistance, and the interface modification layer also acts as a physical barrier to effectively prevent magnesium metal from contacting the electrolyte and inhibit magnesium metal from being passivated, thereby reducing the possibility of a large amount of electrolyte being consumed due to passivation. Moreover, since the interface modification layer has good magnesium ion conductivity, the capacity and cycle life of the magnesium metal battery are improved. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0020] Figure 1 The image shown is a SEM image of the magnesium metal anode surface prepared in Example 1. Figure 2 The image shown is a SEM image of the cross-section of the magnesium metal negative electrode prepared in Example 1. Figure 3 The image shown is the XRD pattern of the magnesium metal anode surface prepared in Example 1. Figure 4 The magnesium metal symmetric cell in Example 1 at 1.0 mA cm⁻¹ -2 Cycle number-voltage curve at current density; Figure 5 The magnesium metal symmetric cell in Example 1 at 1.0 mA cm⁻¹ -2 Coulomb efficiency-cycle number plot at current density; Figure 6 The magnesium metal anode containing the artificial interface layer prepared in Example 1 was tested at 1.0 mA cm⁻¹. -2 SEM image of the surface after 100 cycles at a current density. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are merely descriptive and not limiting, and should not be construed as limiting the scope of protection of the present invention.

[0022] When a quantity, concentration, or other value or parameter is described as a range, preferred range, or preferred upper and lower limits, it should be understood that it is equivalent to specifically disclosing any range by combining any pair of upper or preferred values ​​with any lower or preferred values, regardless of whether the range is specifically disclosed. Unless otherwise stated, the numerical range values ​​listed herein include the endpoints of the range and all integers and fractions within that range.

[0023] Unless otherwise stated, all percentages, parts, ratios, etc. in this document are by weight.

[0024] The materials, methods, and embodiments described herein are exemplary and should not be construed as limiting unless otherwise stated.

[0025] Example 1

[0026] This embodiment provides a method for modifying a highly efficient and stable magnesium metal anode, comprising the following steps: S1. Under an argon atmosphere, the magnesium foil is cut into circular pieces with a diameter of 14 mm, then polished with 1500-grit sandpaper, and ultrasonically rinsed with anhydrous ethanol to remove surface contaminants, thus obtaining the pretreated magnesium foil. S2. Under an argon atmosphere, indium trichloride tetrahydrate was dissolved in acetonitrile solvent and stirred overnight to prepare 1 L of indium trichloride solution with a concentration of 0.4 mol / L; S3. Under an argon atmosphere, one side of the pretreated magnesium foil is covered with tape and then completely immersed in the indium trichloride solution in S2 for 10 seconds to form a solid interface protective layer on the surface of the magnesium foil in situ, thus obtaining a magnesium anode. S4. Under an argon atmosphere, the magnesium anode was repeatedly cleaned 5 times with acetonitrile solvent and then vacuum dried at 60°C for 6 hours to obtain a magnesium metal anode with a protective layer.

[0027] Example 2

[0028] This embodiment provides a method for modifying a highly efficient and stable magnesium metal anode, comprising the following steps: S1. Under atmospheric conditions (humidity 65%), cut the magnesium foil into 12mm diameter discs, then polish them with 1500-grit sandpaper and ultrasonically rinse them with ethylene glycol dimethyl ether to remove surface contaminants, thus obtaining pretreated magnesium foil. S2. Under atmospheric conditions (humidity 65%), dissolve indium trichloride tetrahydrate in ethylene glycol dimethyl ether and stir overnight to prepare 1 L of indium trichloride solution with a concentration of 0.15 mol / L; S3. In an atmospheric environment (humidity of 65%), one side of the pretreated magnesium foil is covered with tape and then completely immersed in the indium trichloride solution in S2 for 60 seconds to form a solid interface protective layer on the surface of the magnesium foil in situ, thus obtaining the magnesium anode. S4. Under atmospheric conditions (humidity 65%), the magnesium anode was repeatedly cleaned 4 times with ethylene glycol dimethyl ether solvent and then vacuum dried at 50°C for 12 hours to obtain a magnesium metal anode with a protective layer.

[0029] Example 3

[0030] This embodiment provides a method for modifying a highly efficient and stable magnesium metal anode, comprising the following steps: S1. Under a nitrogen atmosphere, the magnesium foil is cut into circular pieces with a diameter of 10 mm, then polished with 1500 grit sandpaper, and ultrasonically rinsed with anhydrous ethanol to remove surface contaminants, thus obtaining the pretreated magnesium foil. S2. Under a nitrogen atmosphere, indium trichloride hydrate was dissolved in N-methylpyrrolidone and stirred overnight to prepare 1 L of indium trichloride solution with a concentration of 0.6 mol / L; S3. Under a nitrogen atmosphere, one side of the pretreated magnesium foil is covered with tape and then completely immersed in the indium trichloride solution in S2 for 20 seconds to form a solid interface protective layer on the surface of the magnesium foil in situ, thus obtaining the magnesium anode. S4. Under a nitrogen atmosphere, the magnesium anode was repeatedly cleaned with N-methylpyrrolidone solvent and then vacuum dried at 70°C for 6 hours to obtain a magnesium metal anode with a protective layer.

[0031] Performance test examples This application uses Example 1 as an example to perform performance testing on the prepared magnesium metal anode, specifically as follows: 1) Morphological testing This application performs electron microscopy scanning on the magnesium metal anode prepared in Example 1, and the results are as follows: Figure 1 and Figure 2 As shown, from Figure 1 It can be seen that the surface of the magnesium metal anode after interface modification is a morphology of densely packed particles, and no obvious cracks were found on the surface; from Figure 2 The cross-sectional morphology shows that there are no obvious cracks between the artificial interface layer and the magnesium anode, indicating that the magnesium metal anode and the artificial interface have a good bonding force. The thickness of the artificial interface layer is about 2.3 μm.

[0032] This application also uses X-ray diffraction to test the phase composition of the magnesium metal anode prepared in Example 1, and the results are as follows: Figure 3 As shown. From Figure 3 It is known that the interface on the surface of the magnesium metal anode contains inorganic MgCl2 as well as metallic In and InMg alloy.

[0033] 2) Magnesium metal batteries and their electrochemical performance This application also prepared a magnesium metal battery with the magnesium metal anode from Example 1 as the anode, and tested its electrochemical performance, specifically as follows: 0.267 g of aluminum chloride (AlCl3) was weighed and dissolved in 3 mL of tetrahydrofuran (THF). After stirring for 5 hours, 2 mL of 2 M PhMgCl (dissolved in THF) was gradually added and stirred overnight to prepare the APC electrolyte.

[0034] In an argon glove phase with both water and oxygen values ​​less than 0.01 ppm, symmetrical cell assembly was performed using CR2032 type button cells. The positive and negative electrodes were both pure magnesium foil (comparative example) and magnesium anode with an artificial interface layer attached as described in this application. The separator was a Whatman GF / A glass fiber separator. 90 μL of electrolyte was added to each cell, and the test temperature was 30 °C. The test was conducted using the Xinwei Battery System.

[0035] At 1.0 mA cm -2 Cyclic stability tests were performed at a current density of [value missing], with each charge and discharge lasting 30 minutes. The results are as follows: Figure 4 As shown in the figure, compared with pure magnesium foil (comparative example), the magnesium anode with artificial interface layer can be stably cycled for 1500 cycles with a smaller overpotential, and the modification effect is obvious.

[0036] In an argon glove phase with both water and oxygen values ​​less than 0.01 ppm, asymmetric cell assembly was performed using CR2032 type button cells. The negative electrode was pure magnesium foil (comparative example) and magnesium foil with an artificial interface layer as described in this application. The positive electrode was copper foil, and the separator was a Whatman GF / A glass fiber separator. 90 μL of electrolyte was added to each cell, and the test temperature was 30°C. The test was conducted using the Xinwei Battery System.

[0037] At 1.0 mA cm -2 At a current density of [value missing], a discharge test was first conducted for 30 minutes, and a 0.5 mAh cm⁻¹ layer was electroplated onto the copper foil. -2 The metal Mg was then used; a charging test was subsequently performed at the same current density, with a cutoff voltage of 1.2V. The above process was then cycled, and the coulombic efficiency was calculated by dividing the discharge capacity by the charge capacity per cycle. Figure 5 As shown, compared to pure magnesium foil (comparative example), the magnesium anode containing the artificial interface layer can stably cycle for 500 cycles with a coulombic efficiency of 99%, demonstrating a significant modification effect.

[0038] The magnesium anode after 100 cycles was observed using a scanning electron microscope, and the results are as follows: Figure 6 As shown, the surface changes were not obvious, indicating that the prepared magnesium anode has excellent cycle stability.

[0039] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for modifying a high-efficiency and stable magnesium metal anode, characterized in that, Includes the following steps: 1) Under atmospheric / protective atmosphere, indium trichloride hydrate is dissolved in an organic solvent and stirred overnight to prepare an indium trichloride solution; 2) Under atmospheric / protective atmosphere, one side of the magnesium foil is covered with tape and then completely immersed in indium trichloride solution to form a solid interface protective layer on the surface of the magnesium foil in situ. After cleaning, a magnesium metal negative electrode is obtained, wherein the solid interface protective layer contains inorganic MgCl2 and metallic In and InMg alloy.

2. The method for modifying a highly efficient and stable magnesium metal anode according to claim 1, characterized in that, The concentration of the indium trichloride solution mentioned in step 1) is 0.05-0.6 mol / L.

3. The method for modifying a high-efficiency and stable magnesium metal anode according to claim 2, characterized in that, The organic solvent mentioned in step 1) is one or more of acetonitrile, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and N-methylpyrrolidone.

4. The method for modifying a highly efficient and stable magnesium metal anode according to claim 3, characterized in that, The soaking process parameters described in step 2) are: soaking time of 5-60 seconds.

5. The method for modifying a highly efficient and stable magnesium metal anode according to claim 1, characterized in that, It also includes pretreatment of the magnesium foil, specifically: cutting the magnesium foil to a suitable size, polishing and rinsing with anhydrous ethanol in an atmospheric / protective atmosphere to remove surface contaminants.

6. The method for modifying a highly efficient and stable magnesium metal anode according to claim 5, characterized in that, The cleaning in step 2) specifically involves repeatedly cleaning the magnesium foil with the same organic solvent as in step 1) under atmospheric / protective atmosphere conditions, followed by vacuum drying to obtain a magnesium metal negative electrode with a protective layer.

7. The method for modifying a highly efficient and stable magnesium metal anode according to claim 6, characterized in that, The process parameters for vacuum drying are: vacuum drying temperature of 50-70℃ and time of 6-12h.

8. The method for modifying a highly efficient and stable magnesium metal anode according to any one of claims 1-7, characterized in that, The atmospheric environment is characterized by an ambient humidity of less than 70%; the protective atmosphere is characterized by an inert gas.

9. A highly efficient and stable magnesium metal anode prepared by any one of claims 1-8, characterized in that, It includes a magnesium foil and a protective layer attached to the surface of the magnesium foil.

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