Fluorinated alkyl electrolyte for rechargeable magnesium battery and preparation method and application thereof

Abstract

The application discloses a fluorinated alkyl electrolyte for rechargeable magnesium batteries and a preparation method and application thereof, and the preparation method comprises the following steps: adding anhydrous aluminum chloride into an ether solvent under room temperature and an inert atmosphere, adding a fluorinated alkyl magnesium salt after uniform mixing, stirring until a colorless transparent clear liquid is obtained, and then adding anhydrous magnesium chloride, so that the fluorinated alkyl electrolyte for rechargeable magnesium batteries is obtained after reaction. The electrolyte can be synthesized by one-step stirring in the ether solvent, and no additional additives and water removing agents are needed, so that the electrolyte is easy to be produced on a large scale; the prepared fluorinated alkyl electrolyte has small polarization, high oxidation stability and high coulombic efficiency of magnesium deposition-dissolution.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, and more specifically, to a fluorinated alkyl electrolyte for rechargeable magnesium batteries, its preparation method, and its application. Background Technology

[0002] Battery technology has greatly improved the convenience of life in various fields. However, the increasingly tight global energy supply and critical environmental issues have placed stricter demands on energy storage technologies. Lithium-ion batteries, due to the scarcity of lithium resources and the safety issues arising from lithium dendrite growth, struggle to meet the demands of large-scale energy storage. Among various metal-ion batteries, those based on dual-electron (Mg...) batteries... 2+ The rechargeable magnesium battery with transferred capacity has a high theoretical capacity (3382 mAh / cm³) due to the magnesium metal anode. -3 and 2205mAh g -1 Magnesium batteries have attracted much attention due to their high safety (uniform coating morphology), abundant magnesium reserves (ranking first in the world), and low cost. However, the development of rechargeable magnesium batteries is still in its early stages, and the lack of suitable electrolytes remains the biggest challenge.

[0003] In recent decades, significant breakthroughs have been made in the development of electrolytes for magnesium battery systems. These breakthroughs range from the initial organic aluminum magnesium halide (Mg(AlCl2BuEt)2) electrolyte to later all-phenyl complex (PhMgCl-AlCl3) electrolytes, inorganic magnesium aluminum chloride complex (MgCl2-AlCl3) electrolytes, and hexamethyldisilazane alkyl (HMDSMgCl-AlCl3) electrolytes; and more recently, magnesium hexafluoroisopropylborate (Mg[B(HFIP)4]2) electrolytes. However, some of these electrolytes have narrow electrochemical windows, while others involve complex synthesis processes and high raw material costs. Finding an electrolyte system that simultaneously satisfies high oxidative stability, excellent cycle performance, low magnesium deposition dissolution overpotential, low cost, and simple preparation remains a major challenge in the field of magnesium battery research. Summary of the Invention

[0004] In view of this, the present invention provides a fluorinated alkyl electrolyte for rechargeable magnesium batteries, its preparation method and application, to solve the problems of low oxidation stability and complex preparation process of existing magnesium battery electrolytes.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] A method for preparing a fluorinated alkyl electrolyte for a rechargeable magnesium battery includes the following steps: adding anhydrous aluminum chloride to an ether solvent under an inert atmosphere at room temperature, mixing evenly, adding fluorinated alkyl magnesium salt, stirring until a colorless, transparent, and clear liquid is formed, then adding anhydrous magnesium chloride, and after reaction, the fluorinated alkyl electrolyte for a rechargeable magnesium battery is obtained.

[0007] According to the above scheme, the fluorinated alkyl magnesium salt includes one or more of trifluoroethyl magnesium, hexafluoroisopropyl magnesium, and nonafluorotert-butyl magnesium.

[0008] According to the above scheme, the ether solvent includes one or more of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxane, and 1,4-dioxane.

[0009] According to the above scheme, the molar ratio of the anhydrous aluminum chloride and the fluorinated alkyl magnesium salt is 1:(0.1-1).

[0010] According to the above scheme, the molar ratio of the anhydrous aluminum chloride and the anhydrous magnesium chloride is 1:(0.1-1).

[0011] According to the above scheme, the magnesium ion concentration in the fluorinated alkyl electrolyte of the rechargeable magnesium battery is 0.1-2 mol / L. -1 .

[0012] According to the above scheme, after adding the anhydrous magnesium chloride, the reaction time is 2-12 hours.

[0013] Based on the above-mentioned solution, the second objective of this invention is to provide a rechargeable magnesium battery fluorinated alkyl electrolyte, which is prepared by the above-described method for preparing rechargeable magnesium battery fluorinated alkyl electrolyte.

[0014] According to the above scheme, the oxidation stability potential window of the fluorinated alkyl electrolyte in the rechargeable magnesium battery is not less than 4V (vs. Mg / Mg). 2+ ).

[0015] Based on the above-mentioned solution, the third objective of this invention is to provide a magnesium battery, which includes a positive electrode, a separator, a negative electrode, and the aforementioned rechargeable magnesium battery fluorinated alkyl electrolyte.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) The preparation method used in this invention has low raw material cost, simple synthesis process, and the prepared fluorinated alkyl electrolyte has low polarization and high oxidation stability (>4V vs. Mg / Mg). 2+ The coulombic efficiency of magnesium deposition-dissolution is high (>99%).

[0018] (2) A full cell assembled using a rechargeable magnesium battery fluorinated alkyl electrolyte, achieving a performance of 128.8 mAg. -1 After 500 cycles at a current density of (1C), it still has 64.4 mAg. -1 Its discharge specific capacity demonstrates its potential for commercial applications. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this invention 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 some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 The cyclic voltammetry curves of the MPFB electrolyte described in Example 1 of this invention, using molybdenum foil as the working electrode;

[0021] Figure 2 The linear sweep voltammetry curves of the MPFB electrolyte described in Example 1 of this invention, with molybdenum foil as the working electrode;

[0022] Figure 3 The MPFB electrolyte described in Example 1 of this invention uses copper foil as the working electrode at 0.5 mA cm⁻¹ -2 Magnesium deposition-dissolution coulombic efficiency at current density;

[0023] Figure 4 The MPFB electrolyte described in Example 1 of this invention is used in a magnesium-magnesium symmetric battery at a current density of 0.5 mA / cm². -2 The dough mixing capacity is 0.5mAh cm. -2 Long-cycle performance under these conditions;

[0024] Figure 5 The MPFB electrolyte described in Example 1 of this invention was used in a coin cell assembled with Mo6S8 as the positive electrode material and magnesium metal as the negative electrode, achieving a flux of 128.8 mAg. -1 (1C) Cyclic performance at current density. Detailed Implementation

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0026] It should be noted that, in the description of the embodiments of this application, the term "some specific embodiments" means that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same implementation or instance. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0027] In this embodiment, "within the range" includes the values ​​at both ends, such as "within the range of 1 to 100", which includes the values ​​at both ends of 1 and 100.

[0028] This invention provides a method for preparing a fluorinated alkyl electrolyte for a rechargeable magnesium battery, comprising the following steps: adding anhydrous aluminum chloride to an ether solvent under an inert atmosphere at room temperature, stirring for 1-5 minutes to mix evenly to obtain a milky white insoluble liquid, then adding fluorinated alkyl magnesium salt, stirring for 1-10 minutes until a colorless, transparent, and clear liquid is obtained, and finally adding anhydrous magnesium chloride, reacting for 2-12 hours to obtain the fluorinated alkyl electrolyte for a rechargeable magnesium battery.

[0029] The fluorinated alkyl magnesium salts include one or more of trifluoroethyl magnesium, hexafluoroisopropyl magnesium, and nonafluorotert-butyl magnesium, with the following structural formula. The fluorinated alkyl magnesium salts are prepared according to the following metal substitution reaction: dibutyl magnesium is reacted with trifluoroethanol, hexafluoroisopropanol, and nonafluorotert-butanol respectively in anhydrous ethylene glycol dimethyl ether, and the reaction is carried out under an inert atmosphere. First, the alcohol reactants are dissolved in ethylene glycol dimethyl ether solvent, and then dibutyl magnesium is slowly added dropwise to the reaction solution to initiate the reaction, with a reaction time of 1-24 hours. After the reaction is completed, the solvent ethylene glycol dimethyl ether is removed from the reaction solution under vacuum to obtain the three different magnesium salts.

[0030] Trifluoroethyl magnesium:

[0031] Hexafluoroisopropylmagnesium:

[0032] Nonafluorotert-butylmagnesium:

[0033] Ether solvents include one or more of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxane, and 1,4-dioxane.

[0034] The conditions for an inert atmosphere include: water and oxygen content both below 0.1 ppm.

[0035] Preferably, the molar ratio of anhydrous aluminum chloride to fluorinated alkyl magnesium salt is 1:(0.1-1); the molar ratio of anhydrous aluminum chloride to anhydrous magnesium chloride is 1:(0.1-1); and the magnesium ion concentration in the fluorinated alkyl electrolyte of the rechargeable magnesium battery is 0.1-2 mol / L. -1 .

[0036] This invention only requires one step of stirring in an ether solvent to synthesize the electrolyte, without the need for additional additives and dehydrating agents, making it easy to scale up production.

[0037] Based on the above-described solution, another embodiment of the present invention provides a fluorinated alkyl electrolyte for rechargeable magnesium batteries, prepared using the aforementioned method for preparing fluorinated alkyl electrolytes for rechargeable magnesium batteries. This fluorinated alkyl electrolyte exhibits low polarization and high oxidation stability (>4V vs. Mg / Mg). 2+ The coulombic efficiency of magnesium deposition-dissolution is high (>99%).

[0038] Another embodiment of the present invention provides a magnesium battery, comprising a positive electrode, a separator, a negative electrode, and the aforementioned rechargeable magnesium battery fluorinated alkyl electrolyte. A full cell assembled using the rechargeable magnesium battery fluorinated alkyl electrolyte achieves a performance of 128.8 mAg. -1 After 500 cycles at a current density of (1C), it still has 64.4 mAg. -1 Its discharge specific capacity demonstrates its potential for commercial applications.

[0039] Based on the above embodiments, the present invention provides the following specific examples to further illustrate the invention. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following examples, unless otherwise specified, are generally performed according to the manufacturer's recommended conditions. Unless otherwise stated, percentages and parts are calculated by mass.

[0040] Example 1

[0041] This embodiment provides a method for preparing a fluorinated alkyl electrolyte for a rechargeable magnesium battery, comprising the following steps:

[0042] In an argon glove box with both water and oxygen content below 0.1 ppm, 0.533 g of anhydrous aluminum chloride was weighed and added to 10 mL of ethylene glycol dimethyl ether solvent. The mixture was magnetically stirred at room temperature for 1 minute to ensure uniform dispersion of aluminum chloride in the ethylene glycol dimethyl ether, resulting in a milky white, insoluble liquid. Subsequently, 0.988 g of nonafluorotert-butylmagnesium was weighed and added to the above reaction solution. The mixture was magnetically stirred for 10 minutes until the reaction was complete, resulting in a colorless, clear, transparent liquid. 0.19 g of anhydrous magnesium chloride was then added, and the mixture was stirred for 2–12 hours until the magnesium chloride was completely dissolved. The resulting liquid is the fluorinated alkyl electrolyte for rechargeable magnesium batteries (abbreviated as MPFB electrolyte), in which the concentration of magnesium ions is 0.4 mol / L. -1 .

[0043] Taking the MPFB electrolyte prepared in Example 1 as an example, using the MPFB electrolyte, molybdenum foil as the working electrode, and polished magnesium foil as the counter and reference electrodes, the deposition dissolution performance and oxidation stability window of the electrolyte were tested on a Biologic VMP300 electrochemical workstation, and the results were as follows. Figure 1 and Figure 2 The results are shown in the figure.

[0044] from Figure 1 It can be seen that the MPFB electrolyte can effectively deposit and dissolve magnesium, from Figure 2 It can be seen that the oxidative stability of the MPFB electrolyte is higher than that of 4V (vs. Mg / Mg). 2+ ).

[0045] Taking the MPFB electrolyte prepared in Example 1 as an example, the magnesium deposition-dissolution coulombic efficiency was tested. Specifically, in an argon glove box with water and oxygen contents both below 0.1 ppm, a CR2016 coin cell was assembled using MPFB electrolyte, a glass fiber GF / A separator, a cleaned magnesium foil negative electrode, and a copper foil positive electrode. The charge / discharge current was 0.5 mA cm⁻¹. -2 The discharge time was 15 minutes, and the charge cutoff voltage was 1.5V vs. Mg. Furthermore, a magnesium-magnesium symmetric cell was assembled and tested using this electrolyte. The results were as follows: Figure 3-4 The results are shown in the figure.

[0046] Figure 3 Using MPFT electrolyte with copper foil as the working electrode at 0.5 mA cm⁻¹ -2 Magnesium deposition-dissolution coulombic efficiency plot at current density, from Figure 3 It can be seen that the average deposition-dissolution coulombic efficiency of magnesium is higher than 99%, and it can be stably cycled for more than 3,000 times.

[0047] Figure 4 MPFT electrolyte was used in a magnesium-magnesium symmetric cell at a current density of 0.5 mA cm⁻¹. -2 The dough mixing capacity is 0.5mAh cm. -2- The following long-cycle performance graph, from Figure 4 It can be seen that when the charging and discharging current is 0.5mA cm -2 The surface capacity is 0.5mAh cm -2 At that time, the symmetric cell can cycle 1000 times, lasting up to 2000 hours, and the deposition dissolution overpotential is very low, only 60mV.

[0048] The above performance test results show that the electrolyte prepared by this invention not only has high oxidation stability, long cycle life, and low polarization, but also high coulombic efficiency. To further verify the practical application potential of this invention, a CR2016 coin cell was assembled using layered Mo6S8 as the positive electrode material, MPFB as the electrolyte, and magnesium metal as the negative electrode. Electrochemical tests were conducted, and the results were as follows: Figure 5 The results are shown in the figure.

[0049] from Figure 5 It can be seen that at 128.8mAg -1 After 500 cycles at a current density of (1C), it still has 64.4 mAg.-1 The discharge specific capacity further proves that the fluorinated alkyl electrolyte for rechargeable magnesium batteries prepared in this invention not only has long-term cycle stability but also has good compatibility with cathode materials.

[0050] Example 2

[0051] This embodiment provides a method for preparing a fluorinated alkyl electrolyte for a rechargeable magnesium battery, comprising the following steps:

[0052] In an argon glove box with both water and oxygen content below 0.1 ppm, 0.533 g of anhydrous aluminum chloride was weighed and added to 10 mL of ethylene glycol dimethyl ether solvent. The mixture was magnetically stirred at room temperature for 1 minute to ensure uniform dispersion of aluminum chloride in the ethylene glycol dimethyl ether, resulting in a milky white, insoluble liquid. Subsequently, 0.988 g of nonafluorotert-butylmagnesium was weighed and added to the above reaction solution. The mixture was magnetically stirred for 10 minutes until the reaction was complete, resulting in a colorless, clear, transparent liquid. 0.38 g of anhydrous magnesium chloride was then added, and the mixture was stirred for 2–12 hours until the magnesium chloride was completely dissolved. The resulting liquid is the fluorinated alkyl electrolyte for rechargeable magnesium batteries, with a magnesium ion concentration of 0.6 mol / L. -1 .

[0053] Example 3

[0054] This embodiment provides a method for preparing a fluorinated alkyl electrolyte for a rechargeable magnesium battery, comprising the following steps:

[0055] In an argon glove box with both water and oxygen content below 0.1 ppm, 0.533 g of anhydrous aluminum chloride was weighed and added to 10 mL of ethylene glycol dimethyl ether solvent. The mixture was magnetically stirred at room temperature for 1 minute to ensure uniform dispersion of aluminum chloride in the ethylene glycol dimethyl ether, resulting in a milky white, insoluble liquid. Subsequently, 1.976 g of nonafluorotert-butylmagnesium was weighed and added to the above reaction solution, and the mixture was magnetically stirred for 10 minutes. After sufficient reaction, a colorless, clear, and transparent liquid was obtained. 0.19 g of anhydrous magnesium chloride was added, and the mixture was stirred for 2–12 hours until the magnesium chloride was completely dissolved. The resulting liquid is the fluorinated alkyl electrolyte for rechargeable magnesium batteries, with a magnesium ion concentration of 0.6 mol / L. -1 .

[0056] Example 4

[0057] This embodiment provides a method for preparing a fluorinated alkyl electrolyte for a rechargeable magnesium battery, comprising the following steps:

[0058] In an argon glove box with both water and oxygen content below 0.1 ppm, 0.533 g of anhydrous aluminum chloride was weighed and added to 10 mL of ethylene glycol dimethyl ether solvent. The mixture was magnetically stirred at room temperature for 1 minute to ensure uniform dispersion of aluminum chloride in the ethylene glycol dimethyl ether, resulting in a milky white, insoluble liquid. Subsequently, 0.716 g of hexafluoroisopropylmagnesium was weighed and added to the above reaction solution, and the mixture was magnetically stirred for 10 minutes. After sufficient reaction, a colorless, clear, and transparent liquid was obtained. 0.19 g of anhydrous magnesium chloride was added, and the mixture was stirred for 2–12 hours until the magnesium chloride was completely dissolved. The resulting liquid is the fluorinated alkyl electrolyte for rechargeable magnesium batteries, with a magnesium ion concentration of 0.4 mol / L. -1 .

[0059] Example 5

[0060] This embodiment provides a method for preparing a fluorinated alkyl electrolyte for a rechargeable magnesium battery, comprising the following steps:

[0061] In an argon glove box with both water and oxygen content below 0.1 ppm, 0.533 g of anhydrous aluminum chloride was weighed and added to 10 mL of ethylene glycol dimethyl ether solvent. The mixture was magnetically stirred at room temperature for 1 minute to ensure uniform dispersion of aluminum chloride in the ethylene glycol dimethyl ether, resulting in a milky white, insoluble liquid. Subsequently, 0.716 g of hexafluoroisopropylmagnesium was weighed and added to the above reaction solution, and the mixture was magnetically stirred for 10 minutes. After sufficient reaction, a colorless, clear, and transparent liquid was obtained. 0.38 g of anhydrous magnesium chloride was added, and the mixture was stirred for 2–12 hours until the magnesium chloride was completely dissolved. The resulting liquid is the fluorinated alkyl electrolyte for rechargeable magnesium batteries, with a magnesium ion concentration of 0.6 mol / L. -1 .

[0062] Example 6

[0063] This embodiment provides a method for preparing a fluorinated alkyl electrolyte for a rechargeable magnesium battery, comprising the following steps:

[0064] In an argon glove box with both water and oxygen content below 0.1 ppm, 0.533 g of anhydrous aluminum chloride was weighed and added to 10 mL of ethylene glycol dimethyl ether solvent. The mixture was magnetically stirred at room temperature for 1 minute to ensure uniform dispersion of aluminum chloride in the ethylene glycol dimethyl ether, resulting in a milky white, insoluble liquid. Subsequently, 1.432 g of hexafluoroisopropylmagnesium was weighed and added to the above reaction solution, and the mixture was magnetically stirred for 10 minutes. After sufficient reaction, a colorless, clear, and transparent liquid was obtained. 0.19 g of anhydrous magnesium chloride was added, and the mixture was stirred for 2–12 hours until the magnesium chloride was completely dissolved. The resulting liquid is the fluorinated alkyl electrolyte for rechargeable magnesium batteries, with a magnesium ion concentration of 0.6 mol / L. -1 .

[0065] Example 7

[0066] This embodiment provides a method for preparing a fluorinated alkyl electrolyte for a rechargeable magnesium battery, comprising the following steps:

[0067] In an argon glove box with both water and oxygen content below 0.1 ppm, 0.533 g of anhydrous aluminum chloride was weighed and added to 10 mL of ethylene glycol dimethyl ether solvent. The mixture was magnetically stirred at room temperature for 1 minute to ensure uniform dispersion of aluminum chloride in the ethylene glycol dimethyl ether, resulting in a milky white, insoluble liquid. Subsequently, 0.222 g of trifluoroethyl magnesium was weighed and added to the above reaction solution, and the mixture was magnetically stirred for 10 minutes. After sufficient reaction, a colorless, clear, and transparent liquid was obtained. 0.19 g of anhydrous magnesium chloride was added, and the mixture was stirred for 2–12 hours until the magnesium chloride was completely dissolved. The resulting liquid is the fluorinated alkyl electrolyte for rechargeable magnesium batteries, with a magnesium ion concentration of 0.4 mol / L. -1 .

[0068] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for preparing a fluorinated alkyl electrolyte for a rechargeable magnesium battery, characterized in that, Includes the following steps: Anhydrous aluminum chloride was added to an ether solvent under an inert atmosphere at room temperature. After thorough mixing, a fluorinated alkyl magnesium salt was added, with the following structural formula: , The solution is prepared by stirring any one or a mixture thereof until a colorless, transparent, and clear liquid is formed, then anhydrous magnesium chloride is added, and the reaction yields a rechargeable magnesium battery fluorinated alkyl electrolyte; the molar ratio of the anhydrous aluminum chloride to the fluorinated alkyl magnesium salt is 1:(0.1-1); the molar ratio of the anhydrous aluminum chloride to the anhydrous magnesium chloride is 1:(0.1-1); the magnesium ion concentration in the rechargeable magnesium battery fluorinated alkyl electrolyte is 0.1-2 mol·L⁻¹. -1 .

2. The preparation method according to claim 1, characterized in that, The ether solvents include one or more of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxane, and 1,4-dioxane.

3. The preparation method according to claim 1, characterized in that, After adding the anhydrous magnesium chloride, the reaction time is 2-12 hours.

4. A fluorinated alkyl electrolyte for a rechargeable magnesium battery, characterized in that, It is prepared by the method of any one of claims 1-3 for preparing the fluorinated alkyl electrolyte for rechargeable magnesium batteries.

5. The fluorinated alkyl electrolyte for rechargeable magnesium batteries according to claim 4, characterized in that, The oxidation stability potential window of the fluorinated alkyl electrolyte in the rechargeable magnesium battery is not less than 4V.

6. A magnesium battery, characterized in that, It includes a positive electrode, a separator, a negative electrode, and the fluorinated alkyl electrolyte for a rechargeable magnesium battery as described in claim 4 or 5.

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