A sulfonimidoyl chelated magnesium salt, electrolyte and rechargeable magnesium battery

Abstract

This invention provides a novel sulfonylimide-based chelated magnesium salt, its preparation method, an electrolyte containing the salt, and a rechargeable magnesium battery. The sulfonylimide-based chelated magnesium salt is (1,2-diphenylethane-1,2-diyl)bis((trifluoromethyl)sulfonyl)amide magnesium. The sulfonylimide anion designed in this invention can effectively chelate magnesium ions and regulate their solvation structure. This anion preferentially decomposes on the magnesium anode surface, participating in the formation of a dense and stable SEI film, significantly improving the interfacial compatibility between the electrolyte and the magnesium anode, thereby enhancing the coulombic efficiency and cycle stability of magnesium deposition / dissolution.

Description

Technical Field

[0001] This invention belongs to the field of magnesium battery technology, specifically relating to a sulfonylimide-based chelated magnesium salt, its preparation method, an electrolyte containing the salt, and a rechargeable magnesium battery. Background Technology

[0002] Compared to lithium-ion batteries, which are currently the subject of much research, metallic magnesium has the following advantages (S. Hou, X. Ji, K. Gaskell, P. Wang, L. Wang, J. Xu, R. Sun, O. Borodin, C. Wang, Science, 2021, 374, 172-178): (1) Magnesium ions are less prone to dendrite formation during deposition and are less reactive than lithium, making them safer: (2) Magnesium is abundant in the Earth's crust (2.33%, while lithium is only 0.0065%), so its price is lower and it has a cost advantage; (3) Magnesium is a divalent metal, and its theoretical volumetric capacity can reach 3833 mAh·cm³. -3 It is much higher than that of lithium (2046 mAh·cm⁻¹). -3 ).

[0003] Magnesium metal batteries are considered a next-generation energy storage technology due to their high volumetric capacity and low dendrite content. However, conventional electrolytes face significant challenges: traditional magnesium salts (such as Mg(TFSI)2), while exhibiting good oxidation stability, have poor compatibility with magnesium anodes and are difficult to form a dense SEI film, resulting in low coulombic efficiency (NN Rajput, X. Qu, N. Sa, AKBurrell, KA Persson, J. Am. Chem. Soc., 2015, 137, 3411-3420). Grignard reagent electrolytes (such as 0.4 M (PhMgCl)2-AlCl3 / THF, abbreviated as APC) have good reversibility, but they have low oxidation potentials (typically < 2.5 V vs Mg), are corrosive to current collectors, and use volatile solvents, resulting in poor safety (O. Mizrahi, N, Amir, E. Pollak, O. Chusid, V. Marks, H. Gottlieb, L. Larush, E. Zinigrad, D. Aurbach, J. Electrochem. Soc., 2007, 155, A103). Conventional additives struggle to balance high-voltage stability and interfacial activity.

[0004] Therefore, developing a novel magnesium salt and electrolyte that combines high oxidation stability, excellent magnesium anode compatibility, and low cost is crucial for promoting the industrialization of rechargeable magnesium batteries. Summary of the Invention

[0005] The present invention aims to solve the technical problem that existing rechargeable magnesium battery electrolytes are difficult to balance high oxidation stability, excellent magnesium deposition / dissolution performance and low cost, and provides a novel sulfonylimide-based chelated magnesium salt, its preparation method, and an electrolyte containing the salt and a rechargeable magnesium battery.

[0006] To achieve the above objectives, in one aspect, the present invention provides a sulfonylimide-based chelated magnesium salt having a structure as shown in Formula I:

[0007] Formula I.

[0008] In a second aspect, the present invention provides a method for preparing the sulfonylimide-chelated magnesium salt, comprising the following steps: S1, under inert gas protection, N,N'-(1,2-diphenylethane-1,2-diyl)bis(1,1,1-trifluoromethanesulfonamide) was dissolved in a solvent, and an organomagnesium reagent was added dropwise at room temperature to carry out the reaction; S2, the mixture after the reaction is subjected to vacuum treatment at room temperature to remove the solvent, and the sulfonylimide chelated magnesium salt, namely (1,2-diphenylethane-1,2-diyl)bis((trifluoromethyl)sulfonyl)amide magnesium, is obtained.

[0009] In this application, the N,N'-(1,2-diphenylethane-1,2-diyl)bis(1,1,1-trifluoromethanesulfonamide) is used as a ligand, and its structure is shown in Formula II:

[0010] Formula II.

[0011] In some embodiments, the inert gas is argon.

[0012] In some embodiments, the organomagnesium reagent is dibutylmagnesium, and a hexane solution of dibutylmagnesium can be used.

[0013] In some embodiments, the molar ratio of the organomagnesium reagent to N,N'-(1,2-diphenylethane-1,2-diyl)bis(1,1,1-trifluoromethanesulfonamide) is in the range of (1.3~1.05):1, preferably 1.1:1.

[0014] In some embodiments, the solvent is dimethyl ethylene glycol (DME).

[0015] In a third aspect, the present invention provides an electrolyte comprising the sulfonylimide-chelated magnesium salt and an organic solvent.

[0016] In some embodiments, the concentration of the sulfonylimide chelated magnesium salt in the electrolyte is 0.3–1.0 mol / L. -1 Preferably 0.5 mol L -1 .

[0017] In some embodiments, the organic solvent is an ether solvent, preferably ethylene glycol dimethyl ether.

[0018] In some embodiments, the electrolyte further comprises at least one of a halide, a nitrogen-containing Lewis base, or a phosphate ester. Preferably, the halide is magnesium chloride, magnesium bromide, lithium chloride, or lithium bromide. The nitrogen-containing Lewis base is 3-methoxyethylamine or 3-methoxypropylamine, and the phosphate ester is trimethyl phosphate, triethyl phosphate, or tributyl phosphate.

[0019] In a fourth aspect, the present invention provides a rechargeable magnesium battery comprising a positive electrode, a negative electrode, and an electrolyte.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The sulfonylimide anion designed in this invention can effectively chelate magnesium ions and regulate their solvation structure. This anion preferentially decomposes on the magnesium anode surface, participating in the formation of a dense and stable SEI film, significantly improving the interfacial compatibility between the electrolyte and the magnesium anode, thereby enhancing the coulombic efficiency and cycle stability of magnesium deposition / dissolution. As shown in Example 3, the electrolyte E2 with added MgCl2 can achieve 2000 stable cycles in a magnesium symmetric battery with an overpotential of only 0.2 V.

[0021] The sulfonylimide group has a good charge delocalization effect, making the anion difficult to oxidize. Therefore, the electrolyte prepared from it has an oxidation window that is much longer than that of traditional Grignard reagent electrolytes, making it suitable for high-voltage cathode materials and providing the possibility for the development of high-energy-density rechargeable magnesium batteries.

[0022] Conventional Mg(TFSI)2 absorbs moisture and deliquesces when exposed to air. However, the sulfonylimide anion designed in this invention has a chelating effect on magnesium ions, making the magnesium salt less susceptible to decomposition by trace amounts of water. It does not absorb moisture and deliquesce when exposed to air, exhibiting excellent deliquescence resistance, facilitating storage and handling, and reducing the environmental requirements for battery manufacturing.

[0023] The magnesium salt synthesis route of this invention is short, the raw materials are widely available and inexpensive, the reaction conditions are mild, and it is easy to scale up production, which has significant economic advantages.

[0024] The electrolyte formulated with the magnesium salt of this invention also exhibits good compatibility with the cathode material. As shown in Example 6, the full cell assembled using electrolyte E2 and Mo6S8 cathode retains a capacity of over 78% after 200 cycles at 0.5 C rate, and the coulombic efficiency remains close to 100%, demonstrating excellent cycle stability and practical application potential. Attached Figure Description

[0025] Figure 1 This is the 1H NMR spectrum of the sulfonylimide chelated magnesium salt synthesized in Example 1 of this invention; Figure 2 This is a charge-discharge curve of the magnesium-magnesium symmetric battery of Embodiment 2 of the present invention; Figure 3 This is a charge-discharge curve of the magnesium-magnesium symmetric battery obtained in Example 3 of the present invention; Figure 4 This is a full-cell charge-discharge curve of the rechargeable magnesium battery obtained in Example 6 of the present invention; Figure 5 This is a full-cell cycle stability curve of the rechargeable magnesium battery obtained in Example 6 of the present invention; Figure 6 This is a charge-discharge curve of the magnesium-magnesium symmetric battery obtained in Comparative Example 1. Figure 7 This is a charge-discharge curve of the magnesium-magnesium symmetric battery obtained in Comparative Example 2. Detailed Implementation

[0026] The embodiments of the present invention are described below with reference to the accompanying drawings to make the technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0027] Example 1

[0028] A method for preparing a sulfonylimide-chelated magnesium salt includes the following steps: Under argon protection, N,N'-(1,2-diphenylethane-1,2-diyl)bis(1,1,1-trifluoromethanesulfonamide) (structural formula shown in Formula II) was dissolved in DME, and dibutylmagnesium n-hexane solution was added dropwise at room temperature and reacted for 30 minutes, controlling the molar ratio of dibutylmagnesium to N,N'-(1,2-diphenylethane-1,2-diyl)bis(1,1,1-trifluoromethanesulfonamide) to be 1.1:1.

[0029]

[0030] Formula II

[0031] The mixture after the reaction was subjected to vacuum treatment at room temperature to completely remove the solvent, thereby obtaining the sulfonylimide chelated magnesium salt, namely (1,2-diphenylethane-1,2-diyl)bis((trifluoromethyl)sulfonyl)amide magnesium (structural formula shown in Formula II).

[0032]

[0033] Formula I

[0034] The 1H NMR spectrum of magnesium (1,2-diphenylethane-1,2-diyl)bis((trifluoromethyl)sulfonyl)amide is as follows: Figure 1 As shown.

[0035] Example 2

[0036] The preparation of an electrolyte containing the above-mentioned sulfonylimide chelated magnesium salt and the testing of its magnesium deposition and dissolution performance specifically include the following steps: The above-mentioned sulfonylimide chelated magnesium salt was dissolved in ethylene glycol dimethyl ether to prepare a solution with a concentration of 0.5 mol / L. -1 The solution yields electrolyte E1.

[0037] Polish the surface of the magnesium sheet with sandpaper until clean, cut it into round pieces with a diameter of 12 mm and a thickness of about 200 µm, and transfer it to an inert atmosphere for storage.

[0038] Under an inert atmosphere, using metallic magnesium as the positive and negative electrodes, and a commercial polyethylene membrane as the separator, 0.05 mL of electrolyte E1 was added to assemble a coin cell. Magnesium deposition-dissolution performance was then tested, with a charge-discharge current of 0.1 mA cm⁻¹. -2 0.05 mAh cm -2 Constant current charge and discharge were performed, and the results were as follows: Figure 2 As shown.

[0039] according to Figure 2 The charge-discharge curves of the magnesium-magnesium symmetric battery show that the magnesium-magnesium symmetric battery containing the electrolyte E1 can complete 500 charge-discharge cycles with an overpotential of approximately 0.3 V.

[0040] Example 3

[0041] The preparation of an electrolyte containing the above-mentioned sulfonylimide chelated magnesium salt and the testing of its magnesium deposition and dissolution performance specifically include the following steps: To improve the deposition kinetics on the magnesium anode surface, a halide additive, MgCl2, was introduced into the E1 electrolyte. The molar ratio of sulfonylimide chelated magnesium salt to MgCl2 was 1:0.1, resulting in a clear and transparent electrolyte E2.

[0042] Polish the surface of the magnesium sheet with sandpaper until clean, cut it into round pieces with a diameter of 12 mm and a thickness of about 200 µm, and transfer it to an inert atmosphere for storage.

[0043] Under an inert atmosphere, using metallic magnesium as the positive and negative electrodes, and a commercial polyethylene membrane as the separator, 0.05 mL of electrolyte E2 was added to assemble a coin cell. Magnesium deposition-dissolution performance was then tested, with a charge-discharge current of 0.1 mA cm⁻¹. -2 0.05 mAh cm -2 Perform constant current charging and discharging.

[0044] according to Figure 3 The charge-discharge curves of the magnesium-magnesium symmetric battery show that the magnesium-magnesium symmetric battery containing the electrolyte E2 can complete 2000 charge-discharge cycles with an overpotential of approximately 0.2 V.

[0045] Example 4

[0046] The preparation of an electrolyte containing the above-mentioned sulfonylimide chelated magnesium salt and the testing of its magnesium deposition and dissolution performance specifically include the following steps: To improve the deposition kinetics on the magnesium anode surface, a nitrogen-containing Lewis base additive was introduced into the E1 electrolyte. The nitrogen-containing Lewis base was 3-methoxyethylamine, and the molar ratio of sulfonylimide chelated magnesium salt and 3-methoxyethylamine was 1:1, resulting in a clear and transparent electrolyte E3.

[0047] Polish the surface of the magnesium sheet with sandpaper until clean, cut it into round pieces with a diameter of 12 mm and a thickness of about 200 µm, and transfer it to an inert atmosphere for storage.

[0048] Under an inert atmosphere, using metallic magnesium as the positive and negative electrodes, and a commercial polyethylene membrane as the separator, 0.05 mL of electrolyte E3 was added to assemble a coin cell. Magnesium deposition-dissolution performance was then tested, with a charge-discharge current of 0.1 mA cm⁻¹. -2 0.05 mAh cm -2 Perform constant current charging and discharging.

[0049] Magnesium-magnesium symmetric batteries containing the electrolyte E3 can complete 500 charge-discharge cycles with an overpotential of approximately 0.2 V.

[0050] Example 5

[0051] The preparation of an electrolyte containing the above-mentioned sulfonylimide chelated magnesium salt and the testing of its magnesium deposition and dissolution performance specifically include the following steps: To improve the deposition kinetics on the magnesium anode surface, a phosphate ester additive was introduced into the E1 electrolyte. The phosphate ester was trimethyl phosphate, and the molar ratio of sulfonylimide chelated magnesium salt and trimethyl phosphate was 1:3, resulting in a clear and transparent electrolyte E4.

[0052] Polish the surface of the magnesium sheet with sandpaper until clean, cut it into round pieces with a diameter of 12 mm and a thickness of about 200 µm, and transfer it to an inert atmosphere for storage.

[0053] Under an inert atmosphere, using metallic magnesium as the positive and negative electrodes, and a commercial polyethylene membrane as the separator, 0.05 mL of electrolyte E4 was added to assemble a coin cell. Magnesium deposition-dissolution performance was then tested, with a charge-discharge current of 0.1 mA cm⁻¹. -2 0.05 mAh cm -2 Perform constant current charging and discharging.

[0054] Magnesium-magnesium symmetric batteries containing the electrolyte E4 can complete 500 charge-discharge cycles with an overpotential of approximately 0.2 V.

[0055] Example 6

[0056] The preparation of an electrolyte containing the above-mentioned sulfonylimide chelated magnesium salt and a rechargeable magnesium battery containing the electrolyte specifically includes the following steps: To improve the deposition kinetics on the magnesium anode surface, a halide additive, MgCl2, was introduced into the E1 electrolyte. The molar ratio of sulfonylimide chelated magnesium salt to MgCl2 was 1:0.1, resulting in a clear and transparent electrolyte E2.

[0057] Polish the surface of the magnesium sheet with sandpaper until clean, cut it into round pieces with a diameter of 12 mm and a thickness of about 200 µm, and transfer it to an inert atmosphere for storage.

[0058] The Mo6S8 cathode material, along with the binder polyvinylidene fluoride and conductive carbon black, were ball-milled at a mass ratio of 8:1:1. After being mixed evenly, the mixture was coated onto a stainless steel substrate and dried. Once dried, the mixture was cut into 12 mm diameter circular cathode pieces and placed in an inert atmosphere for use as the cathode of a battery.

[0059] In an inert atmosphere, the negative electrode, electrolyte, and positive electrode are assembled into a battery. The battery structure, from bottom to top, consists of a perforated positive electrode shell, positive electrode, separator, negative electrode, gasket, spring, and negative electrode shell; the battery shell is made of commercially available 304 stainless steel 2032 type battery shell, and the separator is made of commercial polyethylene separator.

[0060] The charge / discharge performance of the rechargeable magnesium battery was tested. The charge / discharge current was 0.5 C, the discharge cutoff voltage was 0.2 V vs. Mg, and the charge cutoff voltage was 2.0 V vs. Mg.

[0061] according to Figure 4 The charge-discharge curves shown indicate that the discharge capacity of the full rechargeable magnesium battery is 59 mAh g. -1 .

[0062] according to Figure 5 As shown in the cycle stability curve, the discharge specific capacity of this rechargeable magnesium battery remains at 46 mAh g after 200 full cycles. -1 The capacity retention rate reached over 78%, and the coulombic efficiency remained at 100%. This indicates that the obtained electrolyte has good positive electrode compatibility and exhibits excellent cycle stability in full cells.

[0063] Comparative Example 1

[0064] Weigh a certain amount of commercially available magnesium bis(trifluoromethanesulfonyl)imide Mg(TFSI)2, dissolve it in ethylene glycol dimethyl ether solvent, and prepare an electrolyte E5 with a concentration of 0.5 mol / L; The surface of the magnesium metal was cleaned by sanding, and then cut into circular pieces with a diameter of 12 mm and a thickness of about 200 µm. The pieces were then transferred to an inert atmosphere for storage.

[0065] Under an inert atmosphere, using metallic magnesium as the positive and negative electrodes, and a commercial polyethylene membrane as the separator, 0.05 mL of electrolyte E5 was added to assemble a coin cell. Magnesium deposition-dissolution performance was then tested, with a charge-discharge current of 0.1 mA cm⁻¹. -2 0.05 mAh cm -2 Perform constant current charging and discharging.

[0066] according to Figure 6 As shown in the charge-discharge curve of the magnesium-magnesium symmetric cell with electrolyte E5, the overpotential of the magnesium-magnesium symmetric cell exceeds 2.0 V. The overpotential is too high, and normal magnesium deposition / dissolution cycles cannot be achieved. Therefore, full cell testing cannot be performed.

[0067] Comparative Example 2

[0068] Weigh a certain amount of commercially available magnesium bis(trifluoromethanesulfonyl)imide Mg(TFSI)2, dissolve it in ethylene glycol dimethyl ether solvent, and add MgCl2 as an example, with a ratio of 1:0.1, to prepare a solution with a concentration of approximately 0.5 mol / L. -1 Electrolyte E6; The surface of the magnesium metal was cleaned by sanding, and then cut into circular pieces with a diameter of 12 mm and a thickness of about 200 µm. The pieces were then transferred to an inert atmosphere for storage.

[0069] Under an inert atmosphere, using metallic magnesium as the positive and negative electrodes, and a commercial polyethylene membrane as the separator, 0.05 mL of electrolyte E6 was added to assemble a coin cell. Magnesium deposition-dissolution performance was then tested, with a charge-discharge current of 0.1 mA cm⁻¹. -2 0.05 mAh cm -2 Perform constant current charging and discharging.

[0070] according to Figure 7 As shown in the charge-discharge curve of the magnesium-magnesium symmetric cell with electrolyte E6, the overpotential of the magnesium-magnesium symmetric cell is approximately more than 2.0 V. The overpotential is too high, and normal magnesium deposition / dissolution cycles cannot be achieved. Therefore, full cell testing cannot be performed.

[0071] Comparing the charge-discharge performance of magnesium-magnesium symmetric batteries in Examples 2 and 3 and Comparative Examples 1 and 2, it is evident that the electrolyte prepared using the sulfonylimide-based chelated magnesium salt of the present invention (i.e., (1,2-diphenylethane-1,2-diyl)bis((trifluoromethyl)sulfonyl)amide magnesium) exhibits a lower overpotential and a longer cycle time. This demonstrates that the unique chelating structure of the sulfonylimide-based chelated magnesium salt of the present invention and the SEI film it induces are key to improving the compatibility and reversibility of the magnesium anode. In particular, the battery performance was further optimized after introducing the MgCl2 additive (E2), and a full cell with excellent cycle stability was successfully achieved. Figure 4 , 5 However, the electrolytes in Comparative Examples 1 and 2 could not be used for full-cell testing.

Claims

1. A sulfonylimide-chelated magnesium salt having the structure shown in Formula I: Formula I.

2. The method for preparing the sulfonylimide-chelated magnesium salt according to claim 1, comprising the following steps: S1, under inert gas protection, N,N'-(1,2-diphenylethane-1,2-diyl)bis(1,1,1-trifluoromethanesulfonamide) was dissolved in a solvent, and an organomagnesium reagent was added dropwise at room temperature to carry out the reaction; S2, the mixture after the reaction is subjected to vacuum treatment at room temperature to remove the solvent, and the sulfonylimide chelated magnesium salt is obtained.

3. The preparation method according to claim 2, wherein, The organomagnesium reagent is dibutylmagnesium.

4. The preparation method according to claim 2, wherein, The molar ratio of the organomagnesium reagent to N,N'-(1,2-diphenylethane-1,2-diyl)bis(1,1,1-trifluoromethanesulfonamide) is (1.3 ~ 1.05):

1.

5. The preparation method according to claim 2, wherein, The molar ratio of the organomagnesium reagent to N,N'-(1,2-diphenylethane-1,2-diyl)bis(1,1,1-trifluoromethanesulfonamide) is 1.1:

1.

6. An electrolyte comprising the sulfonylimide chelated magnesium salt of claim 1, and an organic solvent.

7. The electrolyte according to claim 6, wherein, The concentration of the sulfonylimide chelated magnesium salt in the electrolyte is 0.3–1.0 mol / L. -1 .

8. The electrolyte according to claim 6, wherein, The organic solvent is an ether solvent.

9. The electrolyte according to claim 6, wherein, The electrolyte also contains at least one of a halide, a nitrogen-containing Lewis base, or a phosphate ester.

10. A rechargeable magnesium battery comprising a positive electrode, a negative electrode, and an electrolyte according to any one of claims 6-9.

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