A magnesium metal negative electrode structure and a preparation method and application thereof

Abstract

The application provides a magnesium metal negative electrode structure and a preparation method and application thereof. The preparation method of the magnesium metal negative electrode structure comprises: coating a metal layer on at least one surface of a magnesium substrate by using a vacuum evaporation technology, and the material of the metal layer comprises one or a combination of multiple of Bi, Sn, Sb, Zn, Pb and In. The application forms a dense and uniform metal layer on the magnesium substrate by using the vacuum evaporation technology, so as to effectively isolate the direct contact between the electrolyte and the magnesium substrate, inhibit the occurrence of a side reaction and the formation of a passivation layer; the selected Bi, Sn, Sb, Zn, Pb and In metal materials have good magnesium affinity and good Mg 2+ ion conduction capacity, and the formed protective layer is also a low-impedance, high-stability ion conduction layer, which improves ion conduction efficiency, so that the electrochemical performance of a secondary magnesium battery based on the metal magnesium negative electrode structure is improved.

Description

Technical Field

[0001] This invention belongs to the field of new energy technology, specifically relating to a magnesium metal anode structure, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries have achieved large-scale commercial application and occupy a dominant position in fields such as energy storage power stations. However, while lithium-ion batteries are developing further, many problems have also emerged. First, lithium ranks only 27th in the abundance of elements in the Earth's crust. The continuous consumption and increasing demand for lithium-ion batteries will lead to lithium resource shortages and increased costs. Furthermore, side reactions between the lithium metal anode and the electrolyte, as well as uneven deposition on the electrode surface, can cause dendrite formation, which can puncture the separator and increase battery safety risks. The development of lithium-ion batteries is severely constrained by both cost and safety. Compared to lithium, magnesium resources are much more abundant, ranking 8th in the Earth's crust, and metallic magnesium has a content of 3833 mAh cm⁻¹. -3 The theoretical volumetric specific capacity (lithium metal is 2060 mAh cm⁻¹) -3 Therefore, magnesium metal anodes have the advantages of low cost and high capacity.

[0003] However, magnesium metal anodes suffer from problems such as uneven magnesium deposition and dendrite formation. Furthermore, magnesium metal has strong reducing properties; whether reacting with the electrolyte or present with impurities, it will be oxidized, resulting in a dense passivation film. This passivation film hinders the deposition of magnesium... 2+ Ion conduction inhibits the reversible redox reaction of the magnesium anode, slowing down the kinetics of magnesium electrodeposition. As charging and discharging continue, side reactions intensify, leading to irreversible magnesium deposition / dissolution and ultimately battery failure. Furthermore, the magnesium anode exhibits self-corrosion in chlorine-containing electrolytes; the continuous expansion of corrosion sites causes electrode penetration and the formation of "dead magnesium," reducing the cycle life and safety of rechargeable magnesium batteries. Summary of the Invention

[0004] To solve all or part of the above-mentioned technical problems, the present invention provides the following technical solutions:

[0005] A first aspect of the present invention provides a magnesium metal anode structure comprising:

[0006] A magnesium matrix, wherein the material of the magnesium matrix includes magnesium;

[0007] A protective layer is formed on at least one surface of the magnesium substrate. The protective layer is a metal layer, and the material of the metal layer includes one or more of Bi, Sn, Sb, Zn, Pb, and In. Alternatively, the protective layer is a magnesium alloy layer, and the metal alloyed with magnesium in the magnesium alloy layer includes one or more of Bi, Sn, Sb, Zn, Pb, and In.

[0008] The metal layer is formed by vacuum evaporation; the magnesium alloy layer is formed by first forming the metal layer on the magnesium substrate by vacuum evaporation, and then forming the metal layer by alloying with the magnesium element in the magnesium substrate during the battery charge and discharge cycle.

[0009] Bi, Sn, Sb, Zn, Pb, and In metals have good affinity for magnesium and good Mg content. 2+ The protective layer formed by the ion-conducting agent not only effectively isolates the electrolyte from direct contact with the magnesium substrate, suppressing side reactions and the formation of a passivation layer, but also functions as a low-impedance, high-stability ion-conducting layer, improving ion conduction efficiency and thus enhancing the battery's coulombic efficiency and cycle life. The metal layer formed by one or more of Bi, Sn, Sb, Zn, Pb, and In can also undergo alloying reactions with magnesium in the substrate during battery charge-discharge cycles to form magnesium alloys, further enhancing the magnesium affinity and transport capacity at the interface, thereby promoting uniform magnesium deposition and migration.

[0010] In some embodiments, the thickness of the metal layer is 0.4~1.6 μm. If the metal layer is too thin, the protective effect is weakened; if the metal layer is too thick, ion conduction will be hindered. A thickness range of 0.4~1.6 μm can achieve a balance between protective effect and ion conduction efficiency.

[0011] In some embodiments, the metal layer comprises metal nanoparticles formed from one or more of Bi, Sn, Sb, Zn, Pb, and In. The average particle size of the metal nanoparticles is 0.2–1.0 μm.

[0012] In some embodiments, the metal layer is made of Bi and / or Sn.

[0013] In some embodiments, the magnesium alloy layer contains Bi and / or Sn metals alloyed with magnesium.

[0014] First, the protective layer formed by Bi and / or Sn exhibits superior magnesium affinity and magnesium transport capabilities. Bi and / or Sn metals possess low adsorption and migration energies for magnesium atoms, enabling rapid induction of uniform magnesium deposition and migration. Second, Bi and / or Sn have strong alloying capabilities with magnesium, resulting in a stable alloy phase structure. This allows for the formation of a stable and uniform alloy coating during charge-discharge processes, providing longer-lasting protection for the magnesium substrate. Furthermore, the low volume expansion rate of the Bi and / or Sn alloying reaction with magnesium minimizes disruption to the coating's structural integrity during alloy phase formation. Finally, the Bi and / or Sn metal coating significantly suppresses electrolyte adsorption on the electrode surface, effectively reducing interfacial impedance and promoting magnesium ion interfacial transport.

[0015] In some embodiments, the thickness of the magnesium matrix can be 50~500 μm.

[0016] In some embodiments, the magnesium matrix can be metallic magnesium with a three-dimensional structure, such as magnesium foil, magnesium sheet, magnesium block, etc.

[0017] In some embodiments, the vacuum degree of the vacuum evaporation is 2×10⁻⁶. -4 Below Pa.

[0018] In some embodiments, the deposition rate of the vacuum evaporation is 0.2~4 Å s. -1 .

[0019] In some embodiments, the vacuum evaporation current is 60~120 A.

[0020] In some embodiments, the voltage for vacuum evaporation is 0.4~2.1 V.

[0021] A second aspect of the present invention provides a method for preparing a magnesium metal anode structure, comprising: depositing a metal layer on at least one surface of a magnesium substrate using vacuum evaporation technology, wherein the metal layer is made of one or a combination of Bi, Sn, Sb, Zn, Pb, and In.

[0022] This invention utilizes vacuum evaporation technology to form a dense and uniform artificial protective layer on a magnesium substrate. This allows for nanometer-level control over the layer's thickness, resulting in a dense, pinhole-free layer with strong adhesion to the magnesium substrate and high purity free of impurities. Furthermore, this preparation method is environmentally friendly and easily scalable for mass production.

[0023] In some embodiments, the vacuum degree of the vacuum evaporation is 2×10⁻⁶. -4 Below Pa.

[0024] In some embodiments, the deposition rate of the vacuum evaporation is 0.2~4 Å s. -1 .

[0025] In some embodiments, the vacuum evaporation current is 60~120 A.

[0026] In some embodiments, the voltage for vacuum evaporation is 0.4~2.1 V.

[0027] In some embodiments, the thickness of the protective layer is adjusted by controlling the deposition time, which can be 1000~80000 s, so that the thickness of the obtained protective layer is in the range of 0.4~1.6 μm.

[0028] Because magnesium substrates are prone to irregular scratches, vapor-deposited metal is easily agglomerated at protrusions on the magnesium substrate surface, affecting the uniformity of the protective layer. This invention, by controlling the deposition rate and thickness, enables the protective layer to grow slowly and uniformly, thus avoiding the impact of scratches on the quality of the protective layer. If the deposition rate is too fast, the deposited metal particles may not be able to migrate on the substrate surface, leading to particle agglomeration and the formation of an uneven protective layer. Furthermore, the vacuum degree is controlled at 2 × 10⁻⁶. -4 Below Pa, it is advantageous to obtain a high-quality protective layer efficiently, and this vacuum level can be achieved by using a molecular pump to evacuate.

[0029] For example, the preparation method specifically includes:

[0030] The magnesium substrate is fixed on the substrate holder of the vacuum evaporation equipment. The metal material is used as the evaporation source and placed in a tungsten boat, tantalum boat or ceramic boat. The distance between the substrate holder and the evaporation source is 20~50 cm. The metal material can be one or more of Bi, Sn, Sb, Zn, Pb and In. The metal material can be high-purity metal particles or powder with a purity of 99.99% or higher.

[0031] Start the vacuum system and evacuate the vapor deposition chamber to a vacuum level of 2×10⁻⁶. -4 Below Pa, the evaporation current is controlled at 60~120 A and the evaporation voltage at 0.4~2.1 V to melt and stably evaporate the metal material at a rate of 0.2~4 Å / s. -1 The deposition rate is used to form a protective layer with a thickness of 0.4 to 1.6 μm on the magnesium substrate.

[0032] In some embodiments, the preparation method further includes pretreating the magnesium substrate before vacuum evaporation to remove the oxide layer on its surface. A dense oxide layer easily forms on the surface of magnesium metal, which hinders the bonding between the protective layer and the substrate. Removing the oxide layer through pretreatment can improve the adhesion between the protective layer and the magnesium metal substrate.

[0033] In some embodiments, the average surface roughness of the magnesium substrate is made to be below 320 nm before the vacuum evaporation is performed, in order to further improve the adhesion between the protective layer and the substrate.

[0034] For example, sandpaper can be used to remove the oxide layer on the surface of the magnesium substrate and reduce its surface roughness. Specifically, the pretreatment may include: polishing the magnesium substrate to remove its surface oxide layer, then ultrasonically cleaning it with anhydrous ethanol for 5-10 minutes, and drying it in a vacuum drying oven at 60-80°C.

[0035] In some embodiments, the preparation method further includes controlling the temperature of the magnesium substrate to 15-25°C during vacuum evaporation. Magnesium metal has a low melting point and is easily deformed by temperature during evaporation, thereby compromising the flatness of the substrate. Therefore, temperature control of the magnesium substrate during vacuum evaporation can prevent deformation. For example, a water-cooled circulation pipeline can be installed around the magnesium substrate, and circulating water can be used to control the temperature of the magnesium substrate during vacuum evaporation.

[0036] In some embodiments, the preparation method further includes: assembling a magnesium metal negative electrode structure containing the metal layer into a battery and performing charge-discharge cycles, so that the metal elements in the metal layer and the magnesium elements in the magnesium metal matrix undergo an alloying reaction, thereby forming a magnesium alloy layer in situ.

[0037] A third aspect of the present invention provides a magnesium metal anode structure, which is prepared by the preparation method described in any of the technical solutions.

[0038] A fourth aspect of the present invention provides a secondary magnesium battery comprising the magnesium metal anode structure described in any of the technical solutions.

[0039] In some embodiments, the secondary magnesium battery is a magnesium-sulfur battery, a magnesium-air battery, or a solid-state magnesium battery. Addressing the severe side reactions between the magnesium anode and polysulfides in magnesium-sulfur batteries, the metal protective layer of this invention serves as an effective physical barrier, suppressing the shuttle effect and side reactions. In magnesium-air batteries, this metal protective layer can suppress self-corrosion and hydrogen evolution reaction of the magnesium anode, improving anode utilization and battery specific energy. In solid-state magnesium batteries, this metal protective layer can serve as an interface buffer layer between the solid electrolyte and the magnesium anode, reducing interface impedance and improving solid-solid contact.

[0040] Compared with the prior art, the present invention has at least the following beneficial effects: The present invention forms a dense and uniform metal protective layer on a magnesium substrate using vacuum evaporation technology, effectively isolating the electrolyte from direct contact with the magnesium substrate and suppressing the occurrence of side reactions and the formation of a passivation layer; the Bi, Sn, Sb, Zn, Pb, and In metal materials selected in the present invention have good magnesium affinity and good Mg...2+ The protective layer formed by the metal magnesium anode is itself a low-impedance, high-stability ion-conducting layer, which improves the ion conduction efficiency; thus, the electrochemical performance of the secondary magnesium battery based on this metal magnesium anode structure is improved. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 The images show the SEM morphology and EDS image of the negative electrode surface in Example 1.

[0043] Figure 2 The image shows the SEM morphology of the negative electrode surface in Comparative Example 1.

[0044] Figure 3 This is a SEM image of the negative electrode cross-section of Example 1;

[0045] Figure 4 This is a SEM image of the negative electrode cross-section of Example 8;

[0046] Figure 5 This is a SEM image of the negative electrode cross-section of Example 10;

[0047] Figure 6 The images show the SEM morphology and EDS image of the negative electrode surface in Example 12.

[0048] Figure 7 The symmetrical cell assembled based on the negative electrode of Example 1 and Comparative Example 1 is at 0.2 mA cm⁻¹. -2 Current density, 0.2 mAh cm⁻¹ -2 Figure showing the results of constant current charge-discharge tests under the areal capacity condition;

[0049] Figure 8 The symmetrical cells assembled with the negative electrodes of Example 1 and Comparative Example 1 were used at 0.5 mA cm⁻¹ -2 Current density, 0.05 mAh / cm³ -2 Constant current charge-discharge curves under areal capacity conditions;

[0050] Figure 9 The symmetrical cell of the negative electrode of Example 1 and Comparative Example 1 is at 1 mA cm⁻¹ -2 Current density, 1 mAh cm -2 Constant current charge-discharge curves under areal capacity conditions;

[0051] Figure 10 The half-cell assembled with the negative electrode of Example 1 and Comparative Example 1 at 1 mA cm⁻¹ -2 Current density, 1 mAh cm -2 Figure showing the results of constant current charge-discharge test under the areal capacity condition;

[0052] Figure 11 This is a graph showing the results of long-cycle charge-discharge tests of the full cell assembled with the negative electrode and Mo6S8 positive electrode of Example 1 and Comparative Example 1 under 1 C current density conditions.

[0053] Figure 12 Symmetrical cells assembled with the negative electrodes of Examples 1-6 and Comparative Example 1 at 0.5 mA cm⁻¹ -2 Current density, 0.05 mAh cm⁻¹ -2 Constant current charge-discharge curves under areal capacity conditions;

[0054] Figure 13 Symmetrical cells assembled with the negative electrodes of Examples 7, 10, and Comparative Example 1 at 0.5 mA cm⁻¹ -2 Current density, 0.05 mAh cm⁻¹ -2 Constant current charge-discharge curves under areal capacity conditions;

[0055] Figure 14 The XRD patterns of the symmetrical cell based on the negative electrode of Example 1 after 1 cycle and 10 cycles are shown.

[0056] Figure 15 This is based on the negative electrode of Comparative Example 1 at 1 mA cm⁻¹ -2 Deposition of 1 mAh cm at current density -2 SEM morphology of the surface after magnesium content;

[0057] Figure 16 Based on the negative electrode of Example 1 at 1 mA cm -2 Deposition of 1 mAh cm at current density -2 SEM morphology of the surface after magnesium content;

[0058] Figure 17 The symmetrical battery assembled with the negative electrode of Example 12 and Comparative Example 1 at 0.5 mA cm⁻¹ -2 Current density, 0.05 mAh cm⁻¹ -2 Constant current charge-discharge curves under areal capacity conditions. Detailed Implementation

[0059] The invention will be more fully understood through the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of the invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as intended to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0060] In addition, unless otherwise specified, all raw materials used in the following embodiments can be purchased from the market or other sources, and all production and testing equipment used are known in the art, as are the testing methods used.

[0061] Example 1

[0062] This embodiment provides a magnesium metal anode structure and a method for preparing the magnesium metal anode structure using vacuum thermal evaporation technology, specifically including the following steps:

[0063] (1) Pretreatment of magnesium metal substrate: The surface of magnesium sheet is mechanically polished with sandpaper until it is completely shiny to remove the oxide layer; the polished magnesium sheet is ultrasonically cleaned in anhydrous ethanol for 5 min to remove residual powder and obtain a magnesium metal substrate with a smooth surface and no oxide layer.

[0064] (2) Vacuum evaporation: The pretreated magnesium metal substrate with dimensions of 10 cm × 10 cm is fixed on the substrate holder of the vacuum thermal evaporation system. Bismuth (Bi) powder is used as the evaporation source and is placed in a tungsten boat. The distance between the substrate holder and the evaporation source is set to 40 cm. The chamber is closed and the vacuum system is started to evacuate the evaporation chamber to a vacuum degree of 1 × 10⁻⁶. -5 The deposition rate was set to 82 A, 0.65 V, and 2 Å / s. -1 The deposition thickness and rate were monitored using a film thickness gauge to form a 1 μm thick Bi coating on a magnesium metal substrate. After evaporation, the coating was shaped into 12 mm diameter discs using a slicing machine to obtain a magnesium anode electrode containing a Bi metal coating, denoted as Bi@Mg.

[0065] Example 2

[0066] Example 2 is essentially the same as Example 1, except that in the vacuum evaporation step of Example 2, tin (Sn) metal powder is used as the evaporation source, the evaporation current is 120 A, the evaporation voltage is 1.07 V, and the deposition rate is 2 Å / s. -1 The deposition thickness was 1 μm. The rest of the procedure was the same as in Example 1, and will not be repeated here.

[0067] Example 3

[0068] The process is essentially the same as in Example 1, except that in the vacuum evaporation step of Example 3, antimony (Sb) metal powder is used as the evaporation source, the evaporation current is 75 A, the evaporation voltage is 0.7 V, and the deposition rate is 2 Å / s. -1 The deposition thickness was 1 μm. The rest of the procedure was the same as in Example 1, and will not be repeated here.

[0069] Example 4

[0070] Example 4 is essentially the same as Example 1, except that in the vacuum evaporation step of Example 4, zinc (Zn) metal powder is used as the evaporation source, the evaporation current is 71 A, the evaporation voltage is 0.75 V, and the deposition rate is 2 Å / s. -1 The deposition thickness was 1 μm. The rest of the procedure was the same as in Example 1, and will not be repeated here.

[0071] Example 5

[0072] Example 5 is essentially the same as Example 1, except that in the vacuum evaporation step of Example 5, lead (Pb) metal powder is used as the evaporation source, the evaporation current is 70 A, the evaporation voltage is 0.73 V, and the deposition rate is 2 Å / s. -1 The deposition thickness was 1 μm. The rest of the procedure was the same as in Example 1, and will not be repeated here.

[0073] Example 6

[0074] Example 6 is essentially the same as Example 1, except that in the vacuum evaporation step of Example 6, indium (In) metal powder is used as the evaporation source, the evaporation current is 66 A, the evaporation voltage is 2.1 V, and the deposition rate is 2 Å / s. -1 The deposition thickness was 1 μm. The rest of the procedure was the same as in Example 1, and will not be repeated here.

[0075] Example 7

[0076] Example 7 is essentially the same as Example 1, except that in the vacuum evaporation step of Example 7, the thickness of the Bi metal coating is 0.6 μm, the evaporation current is 60 A, the evaporation voltage is 0.4 V, and the deposition rate is 0.2 Å s. -1 The rest is the same as in Example 1, and will not be described again here.

[0077] Example 8

[0078] Example 8 is essentially the same as Example 1, except that in the vacuum evaporation step of Example 8, the thickness of the Bi metal coating is 0.4 μm, the evaporation current is 72 A, the evaporation voltage is 0.55 V, and the deposition rate is 0.4 Å s. -1 The rest is the same as in Example 1, and will not be described again here.

[0079] Example 9

[0080] Example 9 is essentially the same as Example 1, except that in the vacuum evaporation step of Example 7, the thickness of the Bi metal coating is 1.2 μm, the evaporation current is 80 A, the evaporation voltage is 0.58 V, and the deposition rate is 0.8 Å s. -1 The rest is the same as in Example 1, and will not be described again here.

[0081] Example 10

[0082] Example 10 is essentially the same as Example 1, except that in the vacuum evaporation step of Example 10, the thickness of the Bi metal coating is 1.6 μm, the evaporation current is 83 A, the evaporation voltage is 0.90 V, and the deposition rate is 4 Å s. -1 The rest is the same as in Example 1, and will not be described again here.

[0083] Example 11

[0084] Example 11 is essentially the same as Example 1, except that in the vacuum evaporation step of Example 11, the thickness of the Bi metal coating is 1.0 μm, the evaporation current is 83 A, the evaporation voltage is 0.90 V, and the deposition rate is 4 Å s. -1 The rest is the same as in Example 1, and will not be described again here.

[0085] Example 12

[0086] Example 12 is essentially the same as Example 1, except that in the vacuum evaporation step of Example 12, a mixed powder of Bi metal and Pb metal at a mass ratio of 1:1 is used as the evaporation source, the evaporation current is 78 A, the evaporation voltage is 0.69 V, and the deposition rate is 2 Å / s. -1 The deposition thickness was 1.0 μm. The rest of the procedure was the same as in Example 1, and will not be repeated here.

[0087] Example 13

[0088] Example 13 is essentially the same as Example 10, except that the evaporation current is 84 A, the evaporation voltage is 1.12 V, and the deposition rate is 6 Å / s. -1 The rest is the same as in Example 10, and will not be described again here.

[0089] Example 14

[0090] Example 14 is basically the same as Example 10, except that the thickness of the metallic Bi coating is 2.0 μm. The rest is the same as in Example 10, and will not be described again here.

[0091] Comparative Example 1

[0092] Comparative Example 1 is a magnesium metal anode without metal coating modification, and its preparation steps are as follows:

[0093] Magnesium metal substrate pretreatment: The surface of the magnesium sheet is mechanically polished with sandpaper until it is completely shiny to remove the oxide layer; the polished magnesium sheet is ultrasonically cleaned in anhydrous ethanol for 5 min to remove residual powder and obtain a magnesium metal substrate with a smooth surface and no oxide layer; the pretreated magnesium metal substrate is made into a disc with a diameter of 12 mm using a slicing machine to obtain the magnesium negative electrode sheet.

[0094] Comparative Example 2

[0095] Comparative Example 2 describes the construction of a Bi metal coating on a magnesium substrate by electroplating, and the preparation steps are as follows:

[0096] (1) Pretreatment of magnesium metal substrate: The surface of magnesium sheet is mechanically polished with sandpaper until it is completely shiny to remove the oxide layer; the polished magnesium sheet is ultrasonically cleaned in anhydrous ethanol for 5 min to remove residual powder and obtain a magnesium metal substrate with a smooth surface and no oxide layer.

[0097] (2) Preparation of electroplating solution: 0.1 mol / L disodium ethylenediaminetetraacetate, 0.3 mol / L sodium citrate, 2 g / L polyethylene glycol, 0.03 mol / L bismuth nitrate pentahydrate, 0.5 g / L sodium dodecyl sulfate and 0.1 mol / L boric acid were added to 50 mL of deionized water in sequence and stirred continuously for 12 h until the solution was clear and transparent.

[0098] (3) Electroplating: Under room temperature conditions, using platinum as the counter electrode, pretreated magnesium foil as the working electrode, and the above solution as the electroplating solution, at 0.2 A cm -2 The magnesium foil was deposited under constant current for 60 s. After electroplating, the magnesium foil was removed from the electrolytic cell, rinsed with deionized water, and then dried under vacuum at 80°C for 12 h to obtain a magnesium metal anode with a metallic Bi coating.

[0099] Using the negative electrode sheets prepared in Comparative Examples 1 and 2 and Examples 1-14, CR2032 coin cells were assembled with APC electrolyte; half cells were assembled with Ti foil as the counter electrode and APC electrolyte; and full cells were assembled with Mo6S8 as the positive electrode and APC electrolyte.

[0100] The above-mentioned batteries underwent relevant performance tests, and the test results are summarized in Table 1.

[0101] Table 1

[0102] Group Symmetrical cell overpotential (mV) Symmetrical battery cycle life (h) Half-cell cycle count (revolutions) <![CDATA[Initial full-cell discharge specific capacity (mAh g -1 ).]]> Capacity retention rate (%) after 2500 full battery cycles Example 1 140 2600 1000 77.78 86.14 Example 2 145 2600 990 76.50 85.90 Example 3 205 800 800 70.10 72.10 Example 4 150 1900 950 73.50 80.99 Example 5 145 1490 930 70.88 80.15 Example 6 190 1460 920 70.75 80.01 Example 7 146 1750 945 72.10 80.52 Example 8 138 1200 895 70.01 79.58 Example 9 142 2000 965 73.89 81.20 Example 10 150 2500 985 75.51 84.21 Example 11 140 2500 980 75.62 83.05 Example 12 132 2400 976 75.78 82.59 Example 13 150 800 810 69.80 70.58 Example 14 170 900 815 69.88 71.24 Comparative Example 1 235 500 650 65.48 54.02 Comparative Example 2 210 700 750 68.58 65.74

[0103] Figure 1 The images shown are SEM images and EDS images of the negative electrode surface in Example 1. Figure 2 The image shows the SEM morphology of the negative electrode surface in Comparative Example 1. Figure 3 , Figure 4 and Figure 5 The images are SEM images of the negative electrode cross sections of Examples 1, 8 and 10, respectively. Figure 6 The images shown are SEM and EDS images of the negative electrode surface in Example 12. (Combined with...) Figure 1 , Figure 3-5 It can be seen that the above-mentioned vacuum evaporation technology forms a dense and uniform Bi particle coating on magnesium metal. The Bi coating is tightly bonded to the magnesium metal substrate, with no obvious gaps. (Comparison) Figure 1 , Figure 6 It was found that the coating formed by Bi metal alone had smaller particles with a nanoscale size (about 200 nm), while the composite coating formed by Pb metal and Bi metal had smaller Bi metal nanoparticles loaded on larger Pb metal particles.

[0104] Figure 7 The symmetrical cell assembled based on the negative electrode of Example 1 and Comparative Example 1 is at 0.2 mA cm⁻¹. -2 Current density, 0.2 mAh cm⁻¹ -2 The results of constant current charge-discharge tests under the areal capacity condition are shown in the figure. Figure 7 As shown, the symmetrical battery assembled using the negative electrode material in Example 1 can cycle stably for 4000 hours with only 76 mV overpotential, while Comparative Example 1 only cycles for 1000 hours with an overpotential of 124 mV. This indicates that the Bi metal coating can improve the cycle life of the magnesium metal negative electrode and promote the growth of Mg. 2+ Rapid ion transport.

[0105] Figure 8 The symmetrical cells assembled with the negative electrodes of Example 1 and Comparative Example 1 were used at 0.5 mA cm⁻¹ -2 Current density, 0.05 mAh / cm³ -2 Constant current charge-discharge curves under areal capacity conditions; Figure 9 The symmetrical cell with the negative electrode of Example 1 and Comparative Example 1 at 1 mAcm -2 Current density, 1 mAh cm -2 Constant current charge-discharge curves under areal capacity conditions. Figure 8It can be seen that at 0.5 mA cm -2 Current density, 0.05 mAh cm⁻¹ -2 Under the condition of areal capacity, the symmetrical battery assembled with the negative electrode of Example 1 can cycle stably for 2600 hours, while Comparative Example 1 can only cycle for 500 hours. According to Figure 9 It can be seen that the symmetrical battery assembled with the negative electrode in Example 1 has a performance of 1 mAcm. -2 Current density, 1 mAh cm -2 Under the areal capacity condition, it can stably cycle for more than 2500 hours, while Comparative Example 1 can only cycle for 50 hours. The results show that the negative electrode material in Example 1 exhibits more stable cycle life and lower overpotential at different current densities, which is significantly better than Comparative Example 1.

[0106] Figure 10 The half-cells assembled with Ti foil counter electrodes in Example 1 and Comparative Example 1 were measured at 1 mA cm⁻¹. -2 Current density, 1mAh cm -2 The graph shows the results of constant current charge-discharge tests under areal capacity conditions. Based on... Figure 10 It can be seen that at 1 mA cm -2 Current density, 1 mAh cm -2 Under the given areal capacity conditions, the half-cell assembled in Example 1 can stably cycle for over 1000 cycles, exhibiting more stable long-cycle performance compared to the half-cell assembled in Comparative Example 1.

[0107] Figure 11 This is a graph showing the results of long-cycle charge-discharge tests of the full cell assembled with the negative electrode and Mo6S8 positive electrode of Example 1 and Comparative Example 1 under a 1 C current density condition. Figure 11 As shown, when the current density is 1 C, the initial discharge specific capacity of the full cell assembled in Example 1 is 77.78 mAh g⁻¹. -1 It still retains 73.78 mAh g after 2000 stable cycles. -1 The discharge specific capacity and capacity retention rate are both high, with a coulombic efficiency approaching 100%. Under the same conditions, the full cell assembled in Comparative Example 1 has a discharge specific capacity of only 37.85 mAh g⁻¹ after 2000 cycles. -1 The results show that Example 1 also exhibits stable cycling performance and resistance to Mg in the full-cell system. 2+ The facilitating effect of reversible transport.

[0108] Figure 12 Symmetrical cells assembled with the negative electrodes of Examples 1-6 and Comparative Example 1 at 0.5 mA cm⁻¹ -2 Current density, 0.05 mAh cm⁻¹ -2 A constant current charge-discharge curve under the condition of areal capacity. (See figure.) Figure 12As shown, compared with Comparative Example 1, the anode materials prepared in Examples 1-6 all exhibited longer cycle life and lower overpotential, indicating that the method of constructing a coating containing one or more metals including Bi, Sn, Sb, Zn, Pb, and In on the surface of a magnesium anode using vacuum evaporation technology has a significant effect on improving the cycle life of magnesium anodes and enhancing the performance of magnesium batteries. Among them, the coating containing metallic Bi and / or metallic Sn has a more prominent effect on improving battery cycle life and stability, and is therefore the preferred solution.

[0109] Figure 13 Symmetrical cells assembled with the negative electrodes of Examples 7, 10, and Comparative Example 1 at 0.5 mA cm⁻¹ -2 Current density, 0.05 mAh cm⁻¹ -2 Constant current charge-discharge curves under areal capacity conditions. For example... Figure 13 As shown, when the coating thickness is 0.6 μm and 1.6 μm, the modified magnesium metal anode exhibits longer cycle life and lower overpotential, indicating that the method of constructing a Bi metal coating of different thicknesses on the surface of the magnesium metal anode using vacuum evaporation technology has a significant effect on the cycle stability and Mg content of the magnesium metal anode. 2+ Ion transport plays a significant role. Under the same conditions, the symmetric cell assembled in Example 1 exhibited the best cycle life, indicating that the optimal thickness of the Bi metal coating is 1 μm.

[0110] A symmetrical battery was assembled using the negative electrode material prepared in Example 1, and the battery was tested at 0.2 mA cm⁻¹. -2 Current density, 0.2 mAh cm⁻¹ -2 The cells were subjected to constant current charge-discharge cycles of 1 and 10 cycles under areal capacity conditions. The cycled symmetrical cells were disassembled in a glove box, the negative electrode was removed and cleaned with THF solution, and its surface was subjected to X-ray diffraction (XRD) testing. Figure 14 The images show the XRD patterns of a symmetrical cell based on the negative electrode of Example 1 after 1 cycle and 10 cycles. Figure 14 After cycling, the appearance of the Mg3Bi2 alloy phase on the surface of the negative electrode indicates that the metal Bi coating constructed on the surface of the magnesium negative electrode by vacuum evaporation technology can undergo an alloying reaction with magnesium during the battery charge-discharge cycle, forming an interface layer rich in magnesium-loving Mg3Bi2 alloy phase. Figure 15 and Figure 16 Comparative Example 1 and Example 1 were respectively measured at 1 mA cm⁻¹ -2 Deposition at current density 1 mh cm -2SEM images of magnesium deposition after areal capacity analysis. Comparison shows that the magnesium deposition in Example 1 is dense, uniform, and free of porosity and matrix exposure, while the magnesium deposition in Comparative Example 1 is loose and random, with large areas of exposed magnesium matrix. The results indicate that the interface layer of metallic Bi or the in-situ alloy Mg3Bi2 formed between Bi and Mg is beneficial to the uniform deposition / dissolution process of magnesium, improving the cycle stability of the magnesium metal anode.

[0111] Figure 17 The symmetrical battery assembled with the negative electrode of Example 12 and Comparative Example 1 at 0.5 mA cm⁻¹ -2 Current density, 0.05 mAh cm⁻¹ -2 Constant current charge-discharge curves under areal capacity conditions. For example... Figure 15 As shown, the magnesium metal anode with a composite coating of Pb and Bi can maintain a low overpotential and stable cycling for 2500 hours, indicating that coatings formed by vapor deposition of multiple metals on the surface of the magnesium anode can also improve the cycling stability of the anode and promote the growth of Mg. 2+ transmission.

[0112] Comparing Example 1 and Comparative Example 2, it was found that the metal layer formed by the vacuum evaporation technology of this invention has a smoother and denser surface, more uniform metal particle size, and extremely high purity, compared to the metal layer formed by the method in Comparative Example 2. Furthermore, it allows for nanometer-level thickness control, resulting in high sample consistency. In contrast, the metal layer formed in Comparative Example 2 has a porous and rough surface, less uniform thickness, and a higher content of impurities. The magnesium battery based on the negative electrode structure of Comparative Example 2 exhibits poor specific capacity and cycle performance.

[0113] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0114] All aspects, embodiments, features, and examples of this invention should be considered illustrative and used to explain and illustrate the invention, but not to limit the invention. The scope of the invention is defined only by the claims.

[0115] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the described embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims.

Claims

1. A magnesium metal anode structure, characterized in that, include: A magnesium matrix, wherein the material of the magnesium matrix includes magnesium; A protective layer is formed on at least one surface of the magnesium substrate. The protective layer is a metal layer, and the material of the metal layer includes one or more of Bi, Sn, Sb, Zn, Pb, and In. Alternatively, the protective layer is a magnesium alloy layer, and the metal alloyed with magnesium in the magnesium alloy layer includes one or more of Bi, Sn, Sb, Zn, Pb, and In. The metal layer is formed by vacuum evaporation; the magnesium alloy layer is formed by first forming the metal layer on the magnesium substrate by vacuum evaporation, and then forming the metal layer by alloying with the magnesium element in the magnesium substrate during the battery charge and discharge cycle.

2. The magnesium metal anode structure according to claim 1, characterized in that: The thickness of the metal layer is 0.4~1.6μm; And / or, the metal layer comprises metal nanoparticles formed from one or more of Bi, Sn, Sb, Zn, Pb, and In; And / or, the material of the metal layer includes Bi and / or Sn; And / or, the magnesium alloy layer contains metals alloyed with magnesium, including Bi and / or Sn.

3. The magnesium metal anode structure according to claim 1, characterized in that: The vacuum degree of the vacuum evaporation is 2×10⁻⁶. -4 Below Pa, and / or, the deposition rate of the vacuum evaporation is 0.2~4 Å s. -1 ; and / or, the vacuum evaporation current is 60~120 A, and / or, the vacuum evaporation voltage is 0.4~2.1 V.

4. A method for preparing a magnesium metal anode structure, characterized in that, include: A metal layer is deposited on at least one surface of a magnesium substrate using vacuum evaporation technology. The material of the metal layer includes one or a combination of Bi, Sn, Sb, Zn, Pb, and In.

5. The preparation method according to claim 4, characterized in that: The vacuum degree of the vacuum evaporation is 2×10⁻⁶. -4 Below Pa, and / or, the deposition rate of the vacuum evaporation is 0.2~4 Å s. -1 And / or, the vacuum evaporation current is 60~120 A, and / or, the vacuum evaporation voltage is 0.4~2.1 V.

6. The preparation method according to any one of claims 4-5, characterized in that, Also includes: The magnesium substrate is pretreated before vacuum evaporation to remove the oxide layer on its surface.

7. The preparation method according to any one of claims 4-5, characterized in that, Also includes: During the vacuum evaporation process, the temperature of the magnesium substrate is controlled at 15~25℃.

8. The preparation method according to any one of claims 4-5, characterized in that, Also includes: The magnesium metal anode structure containing the metal layer is assembled into a battery and subjected to charge-discharge cycles, so that the metal elements in the metal layer and the magnesium elements in the magnesium metal matrix undergo an alloying reaction, thereby forming a magnesium alloy layer in situ.

9. A magnesium metal anode structure, characterized in that, It is prepared by the preparation method according to any one of claims 4-8.

10. A secondary magnesium battery, characterized in that, Includes the magnesium metal anode structure as described in any one of claims 1-3 and 9.

Images