Methods and applications for in-situ growth of SEI film on the surface of magnesium anode in rechargeable magnesium batteries

Abstract

This invention discloses a method for in-situ growth of an SEI film on the surface of a magnesium anode in a rechargeable magnesium battery, comprising the following steps: 1) dissolving and mixing tin salt and antimony salt, then adding an electrolytic solvent and stirring until homogeneous to obtain an electrolyte; 2) using magnesium metal as the anode, assembling a rechargeable magnesium battery with the electrolyte prepared in step 1), wherein during storage and charging / discharging, the electrolyte generates an in-situ SnSb-based SEI film on the magnesium metal surface. This invention utilizes an electrolyte containing tin and antimony, which undergoes a reduction-oxidation reaction with magnesium metal to grow an artificial SnSb-based SEI film on the magnesium anode surface. Simultaneously, Sb and Sn exhibit good magnesium affinity, enhancing the Mg²⁺-coated interface between the electrolyte and the electrode. 2+ The SEI film can alleviate the direct contact between magnesium metal and electrolyte, reduce the nucleation potential and dissolution barrier of magnesium deposition, inhibit the growth of magnesium dendrites, and improve the overall performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology, specifically relating to a method for in-situ growth of an SEI film on the surface of a rechargeable magnesium battery metallic magnesium anode and its application. Background Technology

[0002] The high cost and safety issues of lithium-ion batteries still pose significant challenges. In the post-lithium era, there is an urgent need to develop next-generation energy storage devices to meet the current demands of the energy storage field. China has abundant magnesium resources and a mature industry, and magnesium is more stable in the atmosphere than lithium. Magnesium has a low electrode potential (-2.37V vs. SHE) and a high theoretical volumetric capacity (3833 mA h cm⁻¹). -3 This means that magnesium is a suitable candidate energy storage device from both a cost and safety perspective. Therefore, unlike secondary batteries such as lithium, pure metallic magnesium holds promise as a direct anode for rechargeable magnesium metal batteries. However, metallic magnesium anodes are not compatible with traditional simple electrolytes; electrolyte decomposition forms a passivation layer on the magnesium surface, making magnesium ion transport difficult. Furthermore, for current fast-charging technologies, uneven deposition of pure metallic magnesium anodes has been observed under high-current charge and discharge, limiting the development of rechargeable magnesium batteries.

[0003] The construction of artificial SEI films is an effective method to solve the problems of pure magnesium anodes. On the one hand, a stable SEI film on the electrode surface can isolate the direct contact between the anode material and the electrolyte, thereby effectively suppressing side reactions between the anode and the electrolyte. On the other hand, the SEI film can change the activation energy of ion deposition, suppress dendrite formation, and achieve homogeneous deposition. Most existing artificial SEI film construction methods for secondary batteries employ direct coating, redox treatment, and other methods, which are complex and require high-precision processes. In-situ SEI film generation generally refers to the construction of the SEI film through in-situ electrochemical reactions within the battery. This method has advantages such as simple process and stable function. However, there are few reports on in-situ SEI film construction on pure magnesium anodes, making it necessary to conduct relevant research and improvements on the in-situ construction of SEI films on existing magnesium anodes. Summary of the Invention

[0004] 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 method for in-situ growth of an SEI film on the surface of a magnesium anode in a rechargeable magnesium battery, aiming to solve the problems of difficulty in magnesium ion desolvation, high deposition dissolution barriers, and uneven deposition in existing methods. This application also provides the application of this in-situ surface-grown SEI film on a magnesium anode in a rechargeable magnesium battery.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] In a first aspect, a method for in-situ growing an SEI film on the surface of a metallic magnesium anode in a rechargeable magnesium battery includes the following steps:

[0007] 1) Preparation of electrolyte

[0008] After dissolving and mixing the tin salt and antimony salt evenly, add the electrolytic solvent dropwise and stir until evenly mixed to obtain the electrolyte.

[0009] 2) In-situ generation of SEI film

[0010] Using metallic magnesium as the negative electrode, a rechargeable magnesium battery is assembled with the electrolyte prepared in step 1). During the resting and charging / discharging processes of the rechargeable magnesium battery, a SnSb-based SEI film is generated in situ on the surface of metallic magnesium by the electrolyte.

[0011] Preferably, the tin salt is tin trifluoromethanesulfonate, the antimony salt is antimony chloride, and the electrolytic solvent is ethylene glycol dimethyl ether.

[0012] Preferably, the concentrations of the tin salt and antimony salt after dissolution are both 0.05-0.15 mol / L.

[0013] Preferably, step 2) further includes pretreatment of the magnesium metal, specifically: grinding the magnesium metal to remove the oxide layer, ultrasonically cleaning it with ethanol, and drying it for later use.

[0014] Preferably, the molar ratio of the tin salt to the antimony salt is (1-3):(1-3).

[0015] Secondly, a rechargeable magnesium battery metallic magnesium anode obtained by the aforementioned method.

[0016] Thirdly, a rechargeable magnesium battery includes the aforementioned rechargeable magnesium battery metallic magnesium anode.

[0017] Preferably, the positive electrode sheet of the rechargeable magnesium battery comprises the following raw materials by mass percentage: 65-75% positive electrode active material; 15-25% conductive agent; and 5-15% binder.

[0018] Preferably, the positive electrode active material is Mo6S8 positive electrode material; the conductive agent is conductive carbon, and can be any one of acetylene black, carbon black, natural graphite, artificial graphite, Ketjen black, carbon fiber, copper, aluminum, silver, and nickel.

[0019] Preferably, the adhesive is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, polychlorotrifluoroethylene, polyvinyl fluoride (PVDF), and polyvinyl alcohol.

[0020] Compared with the prior art, the present invention has at least the following advantages:

[0021] 1) The method for in-situ growth of an SEI film on the surface of a magnesium anode in a rechargeable magnesium battery provided by this invention utilizes an electrolyte containing tin and antimony. This electrolyte undergoes a reduction-oxidation reaction with magnesium, resulting in the growth of a SnSb-based artificial SEI film on the surface of the magnesium anode. Simultaneously, Sb and Sn exhibit good magnesium affinity, enhancing the Mg exchange between the electrolyte and electrode interface. 2+ The SEI film can alleviate the direct contact between magnesium metal and electrolyte, reduce the nucleation potential and dissolution barrier of magnesium deposition, inhibit the growth of magnesium dendrites, and improve the overall performance of the battery.

[0022] 2) In this application, after the SnSb-based SEI film is generated in situ, the Mg(OTf)2 and MgCl2 that are displaced enter the electrolyte to form a new electrolyte. This electrolyte can be used as an electrolyte for rechargeable magnesium batteries, that is, the electrolyte is formed in situ while the SEI is formed, achieving two goals at once. Compared with artificially added Mg(OTf)2 and MgCl2 salts, the electrolyte after the displacement reaction can provide better magnesium ion transport capacity. In the full cell, it can be matched with a traditional cathode to achieve stable high-capacity cycling.

[0023] 3) The SnSb-based SEI film in this application can provide abundant magnesium deposition sites, wherein the Sn-based structure enables rapid Mg deposition. 2+ The Sb-based electrolyte provides transport capabilities, while the Sb group offers a low magnesium deposition barrier. The combined synergistic effect of these two components results in uniform and dense magnesium deposition and desolvation, achieving ultra-long stable cycling performance under high current density and deposition capacity. The formulated electrolyte can be used with both pure magnesium anodes and conventional Mo6S8 cathodes to achieve full-cell cycling, exceeding 100 cycles while maintaining a capacity of 80 mA hg. -1 above;

[0024] 4) The preparation method of this invention is simple, the raw materials are inexpensive and readily available, and the materials are highly portable. It can be used to form SEI films in situ on a large scale, making it suitable for widespread application. Attached Figure Description

[0025] 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.

[0026] Figure 1 The images show the scanning electron microscope (SEM) image, energy dispersive spectroscopy (EDS) spectrum, and physical image of the in-situ SEI microstructure prepared according to this invention.

[0027] Figure 2 The XRD pattern of the in-situ SEI prepared according to this invention;

[0028] Figure 3 This is a scanning electron microscope image of the magnesium deposition morphology under the conditions of the multi-component electrolyte prepared in this invention;

[0029] Figure 4 The multi-component electrolyte prepared for this invention has a current density of 0.5 mA cm⁻¹. -2 Initial discharge voltage curve for Mg deposition under certain conditions;

[0030] Figure 5 The diagram shows the cycling performance of a symmetrical battery under the 0.1M Sn-Sb-based electrolyte prepared in this invention.

[0031] Figure 6 The rate capability diagram of the symmetric battery under the conditions of the 0.1M Sn-Sb-based electrolyte prepared in this invention;

[0032] Figure 7 Full cell cycle and rate profiles of the 0.1M Sn-Sb-based electrolyte prepared in this invention, coupled with a Mo6S8 cathode;

[0033] Figure 8 Cycling diagrams of the 0.2M Sn-Sb-based electrolyte prepared in this invention and asymmetric cell with stainless steel foil (SS) are shown.

[0034] Figure 9 The diagram shows the cycling process of assembling a symmetric cell using the Sn(OTf)2 and SbCl3 electrolytes prepared according to the present invention. Detailed Implementation

[0035] 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.

[0036] 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.

[0037] Unless otherwise stated, all percentages, parts, ratios, etc. in this document are by weight.

[0038] The materials, methods, and embodiments described herein are exemplary and should not be construed as limiting unless otherwise stated.

[0039] Example 1

[0040] The method for in-situ growth of SEI film on the surface of a rechargeable magnesium battery anode provided in this embodiment includes the following steps:

[0041] S1: Using metallic magnesium as the negative electrode, the oxide layer is removed by grinding with sandpaper of 250, 400, 600, 800, 1000, 1200 and 1500 grit. After grinding, the metal surface is ultrasonically cleaned with ethanol for 7 minutes. Then, it is dried with nitrogen at room temperature. The treated magnesium sheet is then cut into 12mm diameter circular electrode sheets on a cutting machine. To avoid oxidation, it is quickly transferred to a glove box for later use.

[0042] S2: Weigh out Sn(OTf)2 with a purity of 99.99% and SbCl3 with a purity of 99.99% in a molar ratio of 1:1, and prepare a solution with a concentration of 0.1 mol / L for both salts. -1 Mix thoroughly and place in a 5mL reagent bottle. Use a disposable sterile syringe or pipette to accurately take 2mL of dimethyl ethylene glycol (DME) and add it to the electrolyte bottle dropwise. The total time for the dropwise addition process is 30s. Stir the prepared electrolyte magnetically for 12 hours until it becomes clear to obtain the target electrolyte.

[0043] S3: Using the prepared electrolyte, glass fiber (GF / D) as the separator, and magnesium sheets for both the positive and negative electrodes, a CR2032 coin cell is assembled in an argon-filled glove box and sealed under a pressure of 800 MPa to obtain a rechargeable magnesium battery.

[0044] Example 2

[0045] The method for in-situ growth of SEI film on the surface of a rechargeable magnesium battery anode provided in this embodiment includes the following steps:

[0046] S1: Using metallic magnesium as the negative electrode, the oxide layer is removed by grinding with sandpaper of 250, 400, 600, 800, 1000, 1200 and 1500 grit. After grinding, the metal surface is ultrasonically cleaned with ethanol for 7 minutes. Then, it is dried with nitrogen at room temperature. The treated magnesium sheet is then cut into 12mm diameter circular electrode sheets on a cutting machine. To avoid oxidation, it is quickly transferred to a glove box for later use.

[0047] S2. Weigh out Sn(OTf)₂ with a purity of 99.99% and SbCl₃ with a purity of 99.99% in a molar ratio of 1:1, and prepare a solution of 0.2 mol / L for each salt. -1 Mix thoroughly and place in a 5mL reagent bottle. Using a disposable sterile syringe or pipette, accurately add 2mL of dimethyl ethylene glycol (DME) to the electrolyte bottle dropwise. The total time for the dropwise addition process is 30s. Stir the prepared electrolyte magnetically for 12 hours until clear to obtain the target electrolyte.

[0048] S3. Using the prepared electrolyte, glass fiber (GF / D) as the separator, and magnesium sheets for both the positive and negative electrodes, CR2032 button cells are assembled in an argon-filled glove box and sealed under a pressure of 800 MPa to obtain a rechargeable magnesium battery.

[0049] Comparative Example 1

[0050] The method for in-situ growth of SEI film on the surface of a rechargeable magnesium battery anode provided in this embodiment includes the following steps:

[0051] S1: Using metallic magnesium as the negative electrode, the oxide layer is removed by grinding with sandpaper of 250, 400, 600, 800, 1000, 1200 and 1500 grit. After grinding, the metal surface is ultrasonically cleaned with ethanol for 7 minutes. Then, it is dried with nitrogen at room temperature. The treated magnesium sheet is then cut into 12mm diameter circular electrode sheets on a cutting machine. To avoid oxidation, it is quickly transferred to a glove box for later use.

[0052] S2. Weigh out Sn(OTf)₂ with a purity of 99.99% and MgCl₂ with a purity of 99.99%, in a molar ratio of 1:1, with a concentration of 0.1 mol / L for each. -1 Mix thoroughly and place in a 5mL reagent bottle. Using a disposable sterile syringe or pipette, accurately add 2mL of dimethyl ethylene glycol (DME) to the electrolyte bottle dropwise. The total time for the dropwise addition process is 30s. Stir the prepared electrolyte magnetically for 12 hours until clear to obtain the target electrolyte.

[0053] S3. Using the prepared electrolyte, glass fiber (GF / D) as the separator, and magnesium sheets for both the positive and negative electrodes, CR2032 button cells are assembled in an argon-filled glove box and sealed under a pressure of 800 MPa to obtain a rechargeable magnesium battery.

[0054] Comparative Example 2

[0055] The method for in-situ growth of an SEI film on the surface of a rechargeable magnesium battery anode provided by the present invention includes the following steps:

[0056] S1: Using metallic magnesium as the negative electrode, the oxide layer is removed by grinding with sandpaper of 250, 400, 600, 800, 1000, 1200 and 1500 grit. After grinding, the metal surface is ultrasonically cleaned with ethanol for 7 minutes. Then, it is dried with nitrogen at room temperature. The treated magnesium sheet is then cut into 12mm diameter circular electrode sheets on a cutting machine. To avoid oxidation, it is quickly transferred to a glove box for later use.

[0057] S2. Weigh out Mg(OTf)2 with a purity of 99.99% and SbCl3 with a purity of 99.99%, in a molar ratio of 1:1, with a concentration of 0.1 mol / L for each.-1 Mix thoroughly and place in a 5mL reagent bottle. Using a disposable sterile syringe or pipette, accurately add 2mL of dimethyl ethylene glycol (DME) to the electrolyte bottle dropwise. The total time for the dropwise addition process is 30s. Stir the prepared electrolyte magnetically for 12 hours until clear to obtain the target electrolyte.

[0058] S3. Using the prepared electrolyte, glass fiber (GF / D) as the separator, and magnesium sheets for both the positive and negative electrodes, CR2032 button cells are assembled in an argon-filled glove box and sealed under a pressure of 800 MPa to obtain a rechargeable magnesium battery.

[0059] Comparative Example 3

[0060] The method for in-situ growth of an SEI film on the surface of a rechargeable magnesium battery anode provided by the present invention includes the following steps:

[0061] S1: Using metallic magnesium as the negative electrode, the oxide layer is removed by grinding with sandpaper of 250, 400, 600, 800, 1000, 1200 and 1500 grit. After grinding, the metal surface is ultrasonically cleaned with ethanol for 7 minutes. Then, it is dried with nitrogen at room temperature. The treated magnesium sheet is then cut into 12mm diameter circular electrode sheets on a cutting machine. To avoid oxidation, it is quickly transferred to a glove box for later use.

[0062] S2. Weigh out Sn(OTf)2 with a purity of 99.99% and prepare a solution with a concentration of 0.1 mol / L. -1 Mix thoroughly and place in a 5mL reagent bottle. Using a disposable sterile syringe or pipette, accurately add 2mL of dimethyl ethylene glycol (DME) to the electrolyte bottle dropwise. The total time for the dropwise addition process is 30s. Stir the prepared electrolyte magnetically for 12 hours until clear to obtain the target electrolyte.

[0063] S3. Using the prepared electrolyte, glass fiber (GF / D) as the separator, and magnesium sheets for both the positive and negative electrodes, CR2032 button cells are assembled in an argon-filled glove box and sealed under a pressure of 800 MPa to obtain a rechargeable magnesium battery.

[0064] Comparative Example 4

[0065] The method for in-situ growth of an SEI film on the surface of a rechargeable magnesium battery anode provided by the present invention includes the following steps:

[0066] S1: Using metallic magnesium as the negative electrode, the oxide layer is removed by grinding with sandpaper of 250, 400, 600, 800, 1000, 1200 and 1500 grit. After grinding, the metal surface is ultrasonically cleaned with ethanol for 7 minutes. Then, it is dried with nitrogen at room temperature. The treated magnesium sheet is then cut into 12mm diameter circular electrode sheets on a cutting machine. To avoid oxidation, it is quickly transferred to a glove box for later use.

[0067] S2. Weigh out SbCl3 with a purity of 99.99% and prepare a solution with a concentration of 0.1 mol / L. -1 Mix thoroughly and place in a 5mL reagent bottle. Using a disposable sterile syringe or pipette, accurately add 2mL of dimethyl ethylene glycol (DME) to the electrolyte bottle dropwise. The total time for the dropwise addition process is 30s. Stir the prepared electrolyte magnetically for 12 hours until clear to obtain the target electrolyte.

[0068] S3. Using the prepared electrolyte, glass fiber (GF / D) as the separator, and magnesium sheets for both the positive and negative electrodes, CR2032 button cells are assembled in an argon-filled glove box and sealed under a pressure of 800 MPa to obtain a rechargeable magnesium battery.

[0069] Performance test example:

[0070] This application conducts performance tests on the rechargeable magnesium battery metallic magnesium anodes prepared in Examples 1-2 and Comparative Examples 1-4, specifically as follows:

[0071] 1) Reaction process testing

[0072] This test example uses Example 1, Comparative Example 1, and Comparative Example 2 to test the in-situ reaction process of the magnesium anode in this rechargeable magnesium battery. Specifically, in a glove box, 40 μL of the electrolyte from step S2 was dropped onto the treated magnesium sheet and left to stand for a period of time to visualize the in-situ reaction of the three electrolytes. After standing in a button cell with the Mg(OTf)2-SbCl3 (Mg-Sb) electrolyte for 6 hours, the color of the Mg anode changed from silvery-white to gray. In contrast, the Sn(OTf)2-MgCl2 (Sn-Mg) in the comparative example only left a faint silvery-gray product. In comparison, in the presence of the Sn(OTf)2-SbCl3 (Sn-Sb) electrolyte, the Mg anode turned pure black after only 1 minute. This indicates that all three electrolytes can react in-situ with the Mg anode and produce an SEI protective film; the Sn-Sb electrolyte reacts faster with the Mg anode, and the presence of Sn(OTf)2 promotes the formation of the SEI.

[0073] 2) Appearance and morphology test

[0074] This test uses Example 1 as an example to perform performance testing on the prepared rechargeable magnesium battery metallic magnesium anode, specifically as follows:

[0075] Figure 1 Figures a and b show the surface morphology and cross-sectional view of the pure magnesium anode, proving that the oxide layer was removed after polishing. Figure c shows a visual image of the magnesium anode treated with pure magnesium and three different electrolytes. Figures d1, d2, e1, and e2 show Sn(OTf)2-SbCl3 electrolyte f1 and f2, g1 and g2 show Mg(OTf)2-SbCl3 electrolyte f1, h1, h2, i1, and i2 show scanning electron microscope (SEM) images, energy dispersive X-ray spectroscopy (EDS) spectra, cross-sectional views, and EDS spectra of Sn(OTf)2-MgCl2 reacting with magnesium sheets. As can be seen from the figures, a protective layer with a thickness of approximately 10 μm is formed on the Sn-Sb magnesium sheet. This protective layer is thinner than the Mg-Sb protective layer, which is more conducive to subsequent magnesium transport. Furthermore, this protective layer is smoother than that of the pure magnesium sheet after sandpaper polishing. Energy dispersive X-ray spectroscopy (EDS) analysis... Figure 1 (as shown) and X-ray diffraction spectroscopy (XRD, Figure 2 Both studies demonstrate that the Sn and Sb obtained from the reaction are uniformly distributed within the SEI film. The protective layer of Sn-Mg shows that it consists of reduced Sn blocks and trifluoromethanesulfonate, and the Sn metal does not completely cover the magnesium surface. (3mA cm⁻¹) –1 Discharging at a high current density for 1 hour resulted in magnesium deposition on the magnesium sheet at the positive electrode and magnesium detachment from the magnesium sheet at the negative electrode. Figure 3 It is the positive (a) of Sn(OTf)2-MgCl2 1、 a2) negative (b) 1、 b2) electrode, Sn(OTf)2-SbCl3 positive (c 1、 c2) negative (d 1、 d2) The positive electrode of Mg(OTf)2-SbCl3 (e) 1、 e2) negative(f 1、 f2) Extreme SEM images at different magnifications, in which the magnesium deposit formed by Sn(OTf)2-SbCl3 is uniform and dense, with a uniform number of corrosion pits and small pore size.

[0076] 3) Electrochemical performance testing

[0077] This test examines the electrochemical performance of the batteries encapsulated in Examples 1 and 2, as well as Comparative Examples 1-4. Specifically, the encapsulated batteries are subjected to an electric field of 0.5 mA cm⁻¹. -1 The charge / discharge was performed at a current density of 0.5 mA h cm⁻¹, with a cutoff capacity of 0.5 mA h cm⁻¹. -1 Overpotential and cycle performance tests were conducted, and the specific results are as follows:

[0078] The overpotential test of the battery packaged in Example 1 is as follows: Figure 4 As shown, at a current density of 0.5 mA / cm² -2 At that time, the Sn(OTf)2-SbCl3 electrolyte reaches a relatively low overpotential μ. n The initial voltage is 0.04V. As Mg deposition continues, the voltage decreases until it reaches a stable plateau value (deposition potential μ). p Notably, μ in Sn(OTf)2-SbCl3 p Only 0.17V. Cyclic results ( Figure 5 The results show that the symmetric cell in Sn(OTf)₂-SbCl₃ electrolyte exhibits a deposition potential of approximately 0.12V, which decreases with cycling, reaching approximately 0.08V after over 1000 hours of cycling. This demonstrates its excellent magnesium deposition behavior and cycling performance, verifying the reduction of the energy barrier for Mg nucleation by the SnSb-based SEI film. The rate performance test results of the symmetric cell are as follows... Figure 6 As shown, at 3mA cm -1 Under high current density, the battery did not short-circuit, and the deposition potential was only 0.45V;

[0079] The overpotential test of the battery packaged in Comparative Example 1 is as follows: Figure 4 As shown, at a current density of 0.5 mA / cm² -2 At that time, Sn(OTf)2-MgCl2 electrolyte reached a lower μ value. n The overpotential is 0.24V. As Mg deposition continues, the overpotential decreases, reaching a stable plateau value (μ). p μ in Sn(OTf)2-MgCl2 p The voltage is 0.34V. Cyclic results ( Figure 5 The results show that the symmetric cell in Sn(OTf)₂-MgCl₂ electrolyte exhibits a deposition potential of approximately 0.23V and a cycling life exceeding 600 hours. However, the polarization voltage increases with cycling. Compared to the Sn(OTf)₂-SbCl₂ example, the deposition potential is significantly higher, verifying that the presence of Sb in the SEI film plays a crucial role in lowering the energy barrier for Mg nucleation. The rate performance test results of the symmetric cell are as follows... Figure 6 As shown, at 3mA cm –1 Under high current density, the battery did not short-circuit, and the deposition potential was 0.62V. The deposition morphology was as follows. Figure 3 As shown, uneven granular deposits are present, the number of corrosion pits is uneven, and the pore size is relatively large.

[0080] The overpotential test of the battery packaged in Comparative Example 2 is as follows: Figure 4 As shown, at a current density of 0.5 mA / cm²-2 At that time, the Mg(OTf)2-SbCl3 electrolyte reached a high μ n The overpotential is 2.55V. As Mg deposition continues, the overpotential decreases, reaching a stable plateau value (μ). p μ in Mg(OTf)2-SbCl3 p The voltage is 0.86V. Cyclic results ( Figure 5 The results indicate that the symmetric cell with Sn(OTf)₂-MgCl₂ electrolyte exhibits a relatively high deposition potential of approximately 0.3V, the highest compared to the Sn(OTf)₂-SbCl₃ example and the Sn(OTf)₂-MgCl₂ comparative example, but experiences a short circuit after 180 hours of cycling. The presence of Sb in the SEI film can lower the energy barrier for Mg nucleation, but Sn(OTf)₂ shows better cycling performance than Mg(OTf)₂. The rate performance test results of the symmetric cell are as follows... Figure 6 As shown, at 3mA cm –1 Under high current density, the battery did not short-circuit, and the deposition potential was 1.08V.

[0081] The test results for overpotential and cycle performance of the battery packaged in Comparative Example 3 are as follows: Figure 9 As shown in the figure, the overpotential is as high as about 5V when only Sn(OTf)2 is present, indicating that Sn(OTf)2 has a high magnesium ion nucleation barrier, which will cause the electrolyte to decompose to a certain extent and form an unstable voltage curve.

[0082] The test results for overpotential and cycle performance of the battery packaged in Comparative Example 4 are as follows: Figure 9 As shown in the figure, the initial overpotential exceeds 4V in the presence of only SbCl3, and the deposition potential gradually decreases in subsequent cycles, exhibiting a short-circuit trend. This indicates that the presence of SbCl3 reduces the polarization voltage, verifying that the Sb-based SEI provides good magnesium deposition sites, which is beneficial for magnesium ion deposition. Subsequent cycles revealed that the overpotential increased again, possibly due to the instability of the independent Sb-based SEI leading to decomposition, while the MgCl2 produced by the reaction of the magnesium anode with SbCl3 further contributes to the deposition of magnesium ions. 2+ The signal could not be transmitted effectively, and eventually the battery short-circuited.

[0083] 4) Full battery performance analysis

[0084] This application uses Example 1 as an example to conduct full-cell performance analysis and testing on the rechargeable magnesium battery metallic magnesium anodes prepared in Example 1, Comparative Example 1, and Comparative Example 2. Specifically:

[0085] The testing method is as follows:

[0086] Preparation of Mo6S8 cathode: KCl was dried under vacuum at 150℃ for 3 hours and then used as a solvent. 0.623 g KCl, 1 g MoS2, 0.4 g CuS, and 0.6 g Mo were ground in a mortar for 30 minutes, then poured into a crucible. The sample was then calcined at 850℃ in an argon atmosphere for 60 hours. The product was washed with deionized water and then subjected to a 6 mol / L... –1 Oxygen was bubbled into an aqueous hydrochloric acid solution and stirred for 24 hours to obtain Mo6S8.

[0087] The prepared Mo6S8 cathode material, conductive carbon black Super P, and PVDF were mixed in NMP solvent at a weight ratio of 70:20:10 to form a homogeneous slurry. The slurry was then coated onto stainless steel (SS, 304) foil using a 100 μm doctor blade and dried under vacuum at 60 °C for 12 hours. The slurry was then cut into circular electrode sheets with a diameter of 12 mm using a cutting machine, with an average cathode loading of 1.0–1.2 mg / cm³. –2 ;

[0088] A 12mm diameter circular magnesium sheet was used as the negative electrode, and a Mo6S8 circular electrode sheet was used as the positive electrode. Three electrolytes—Sn(OTf)2-SbCl3, Sn(OTf)2-MgCl2, and Mg(OTf)2-SbCl3—prepared in Examples 1, 1, and 2, were used. In a glove box with H2O and O levels both less than 0.01ppm, CR2032 coin cells were assembled in the following order: negative electrode shell, spring sheet, gasket, magnesium sheet separator, electrolyte, Mo6S8 positive electrode, gasket, and positive electrode shell. The assembled CR2032 cells were sealed using a battery sealing machine under a pressure of 800MPa. The electrolyte volume for each cell was 100μL.

[0089] The assembled battery was placed in the NEWARE battery test channel for constant current charge-discharge electrochemical testing. The charging cutoff voltage was 2V, and the discharging cutoff voltage was 0.005V, at a rate of 50mA hg. -1 The tests were conducted at various current densities; the rate performance test involved changing the current density at 20, 50, 100, 150, 200, and 500 mA hg. -1 The experiment was conducted at a current density of [value missing].

[0090] Results analysis:

[0091] The rechargeable magnesium battery anode in one of the embodiments underwent full-cell performance analysis and testing, and the results are as follows: Figure 7 As shown, from Figure 7 From a, we can see that at 50mA g -1 The capacity can reach up to 87 mA hg at current density. -1Furthermore, after 100 full battery cycles, the capacity retention rate is approximately 80%, demonstrating excellent cycle performance. Figure 7 b, at 500mA g -1 Even at high current densities, the capacity can still be maintained at 20 mA hg -1 This proves its excellent rate capability.

[0092] The full-cell performance analysis test was performed on the rechargeable magnesium battery anode in Example 1, and the results are as follows: Figure 7 As shown in figure a, it can be seen from the figure that at 50mA g -1 At current densities, the capacity can reach up to 51 mA hg -1 Furthermore, the capacity of the full battery shows a slight increasing trend after 100 cycles, demonstrating good cycle stability.

[0093] The full-cell performance analysis of the rechargeable magnesium battery anode in Example 2 was conducted, and the results are as follows: Figure 7 As shown in figure a, it can be seen from the figure that at 50mA g -1 The lack of magnesium storage capacity at the given current density further demonstrates that Sn plays a more important role in the transport of magnesium ions in the electrolyte and their insertion into the positive electrode.

[0094] 5) Coulomb efficiency test

[0095] This test uses Example 2 as an example to test the coulombic efficiency of the magnesium metal anode of the rechargeable magnesium battery of this application, specifically as follows:

[0096] Test method: Using pure magnesium sheet as the negative electrode, a prepared electrolyte, glass fiber (GF / D) as the separator, and a 14mm diameter stainless steel electrode as the positive electrode, a CR2032 coin cell was assembled in a glove box. The packaged cell was then subjected to a 0.5mA test. -1 0.5mAh cm -1 Discharge is performed under the operating conditions, and the charging cut-off voltage is 1.2V.

[0097] The results are as follows Figure 8 As shown in figure a, it can be seen from the figure that, Figure 8 As shown, increasing the solute concentration proportionally resulted in a slight decrease in deposition potential. With continued cycling, the polarization voltage decreased more rapidly, reaching a minimum of approximately 0.05V, at which point a short circuit occurred after 680 hours. The ratio of magnesium ion deposition capacity to discharge fixed capacity on stainless steel reflects the coulombic efficiency. For example... Figure 8 As shown in b, 0.2 M Sn(OTf)2-SbCl3 has a coulombic efficiency of up to 99%, demonstrating excellent cycle reversibility.

[0098] Analysis of examples and comparative studies clearly shows that the passivation and decomposition problems of Mg(OTf)2 faced by Mg(OTf)2 as an improved electrolyte are solved by replacing Mg(OTf)2 with Sn(OTf)2 and introducing SbCl3. The presence of Sn(OTf)2 extends the cycle life, and Sn also becomes part of the SEI film through in-situ reaction. The presence of SbCl3 further enhances the passivation and decomposition of Mg(OTf)2. 2+ It facilitates deposition, reducing the polarization voltage. This enhances the Mg... 2+ Reversibility of transmission.

[0099] 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 in-situ growth of an SEI film on the surface of a magnesium anode in a rechargeable magnesium battery, characterized in that, Includes the following steps: 1) Preparation of electrolyte After dissolving and mixing the tin salt and antimony salt evenly, add the electrolytic solvent dropwise and stir until evenly mixed to obtain the electrolyte. 2) In-situ generation of SEI film Using metallic magnesium as the negative electrode, a rechargeable magnesium battery is assembled with the electrolyte prepared in step 1). During the resting and charging / discharging process, a SnSb-based SEI film is generated in situ on the surface of metallic magnesium in the electrolyte. The tin salt is tin trifluoromethanesulfonate, the antimony salt is antimony chloride, and the electrolytic solvent is ethylene glycol dimethyl ether.

2. The method for in-situ growth of an SEI film on the surface of a rechargeable magnesium battery anode according to claim 1, characterized in that, The concentrations of the dissolved tin salt and antimony salt are both 0.05-0.15 mol / L.

3. The method for in-situ growth of an SEI film on the surface of a rechargeable magnesium battery anode according to claim 2, characterized in that, Step 2) also includes pretreatment of the magnesium metal, specifically: grinding the magnesium metal to remove the oxide layer, ultrasonically cleaning it with ethanol, and drying it before use.

4. The method for in-situ growth of an SEI film on the surface of a rechargeable magnesium battery anode according to claim 3, characterized in that, The molar ratio of the tin salt to the antimony salt is (1-3):(1-3).

5. A rechargeable magnesium battery metallic magnesium anode obtained by the method according to any one of claims 1-4.

6. A rechargeable magnesium battery, characterized in that, Includes the rechargeable magnesium battery metallic magnesium anode as described in claim 5.

7. The rechargeable magnesium battery according to claim 6, characterized in that, The positive electrode sheet of the rechargeable magnesium battery comprises the following raw materials by mass percentage: 65-75% positive electrode active material; 15-25% conductive agent; and 5-15% binder.

8. The rechargeable magnesium battery according to claim 7, characterized in that, The positive electrode active material is Mo6S8 positive electrode material; the conductive agent is any one of carbon black, natural graphite, artificial graphite, carbon fiber, copper, aluminum, silver, and nickel.

9. The rechargeable magnesium battery according to claim 7, characterized in that, The adhesive is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, polychlorotrifluoroethylene, and polyvinyl alcohol.

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