A magnesium battery electrolyte, a preparation method and application thereof

Abstract

The application discloses a magnesium battery electrolyte and a preparation method and application thereof. The magnesium battery electrolyte comprises a magnesium salt and a machine solvent, and the magnesium salt is hexafluoroisopropyl magnesium. The magnesium battery electrolyte provided by the application is non-corrosive, can realize high oxidation stability under various current collectors, can be applied in high-voltage magnesium batteries, and the full battery assembled by using the electrolyte still has no obvious capacity attenuation after 200 cycles.

Description

Technical Field

[0001] This invention relates to the field of magnesium battery technology, and more specifically, to a magnesium battery electrolyte, its preparation method, and its application. Background Technology

[0002] Magnesium batteries using magnesium as the negative electrode generally do not pose a risk of dendrite growth. Furthermore, magnesium boasts advantages such as low cost, high resource abundance (1.94% of the Earth's crust), low reduction potential, and high theoretical energy density, making it a promising candidate for next-generation energy storage devices. However, magnesium forms a dense passivation layer in most conventional electrolytes, hindering magnesium ion transport. This severely restricts the development of magnesium batteries, making the development of an electrolyte compatible with magnesium a top priority in magnesium battery research.

[0003] Currently, mainstream magnesium battery electrolytes are highly complex, often requiring the addition of multiple components such as aluminum chloride, phenyl magnesium chloride, and magnesium chloride. This not only increases the complexity of the preparation process but also leads to increased corrosivity due to the presence of chloride ions in the electrolyte. Therefore, magnesium battery current collectors often require expensive precious metals. On the other hand, simple, non-corrosive magnesium salts such as magnesium hexafluorophosphate [Mg(PF6)2], magnesium perchlorate [Mg(ClO4)2], and magnesium bis(trifluoromethanesulfonyl)imide [Mg(TFSI)2] react with the highly reactive magnesium metal anode to form a passivation layer. Electrolytes prepared using these magnesium salts cannot effectively deposit and dissolve magnesium. Therefore, developing an electrolyte that is both non-corrosive and simple in composition, while also being able to withstand high voltages, is a common research goal in the field of magnesium batteries. Summary of the Invention

[0004] In view of this, the present invention provides a magnesium battery electrolyte, its preparation method and application, to solve the problems of existing magnesium battery electrolytes having many components, low oxidation stability and severe corrosivity.

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

[0006] A magnesium battery electrolyte comprising a magnesium salt and an organic solvent, wherein the magnesium salt is hexafluoroisopropylmagnesium.

[0007] According to the above scheme, the organic solution is one or more of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxane, 1,4-dioxane, ethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, and diethyl carbonate.

[0008] According to the above scheme, the concentration of magnesium ions in the magnesium battery electrolyte is 0.1-2 mol / L. -1 .

[0009] According to the above scheme, the oxidation stability window of the magnesium battery electrolyte is not less than 3.7V (vs. Mg / Mg). 2+ ).

[0010] Based on the above scheme, the second objective of this invention is to provide a method for preparing the magnesium battery electrolyte as described above, comprising the steps of: adding a magnesium salt to an organic solvent under an inert atmosphere, stirring evenly, and obtaining the magnesium battery electrolyte after the magnesium salt is completely dissolved, wherein the magnesium salt is hexafluoroisopropyl magnesium.

[0011] According to the above scheme, the conditions for the inert atmosphere include: the water and oxygen contents are both below 0.1 ppm.

[0012] According to the above scheme, the stirring time is 1-2 minutes.

[0013] Based on the above-described solution, the third objective of this invention is to provide the application of the magnesium battery electrolyte as described above in the field of magnesium batteries.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] (1) The magnesium battery electrolyte provided by the present invention has a simple composition, the solute contains only one simple magnesium salt, and the preparation process of the electrolyte can be achieved by stirring at room temperature for a few minutes, which greatly simplifies the experimental steps and enables large-scale production.

[0016] (2) The magnesium battery electrolyte provided by the present invention is non-corrosive and can achieve high oxidation stability under various current collectors. It can be applied to high-voltage magnesium batteries. After 200 cycles, the full battery assembled with this electrolyte still has no obvious capacity decay. Attached Figure Description

[0017] 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.

[0018] Figure 1 The cyclic voltammetry curves of the magnesium battery electrolyte described in Example 1 of this invention, using magnesium foil as the counter electrode and reference electrode and stainless steel foil as the working electrode;

[0019] Figure 2 The linear sweep voltammetric curves of the magnesium battery electrolyte described in Example 1 of this invention are obtained by using magnesium foil as the counter electrode and reference electrode, and using different metals (molybdenum, aluminum, stainless steel, copper, and titanium) as working electrodes.

[0020] Figure 3 The results show the magnesium deposition-dissolution coulombic efficiency of the magnesium battery electrolyte described in Example 1 of this invention, using magnesium foil as the counter electrode and stainless steel foil as the working electrode.

[0021] Figure 4 The voltage-time curve of the magnesium battery electrolyte described in Example 1 of this invention in a magnesium-magnesium symmetric cell;

[0022] Figure 5 The ionic conductivity of the magnesium battery electrolyte described in Example 1 of this invention at different concentrations;

[0023] Figure 6 The coin cell assembled using Mo6S8 as the positive electrode material and magnesium metal as the negative electrode in the magnesium battery electrolyte of Embodiment 1 of this invention achieved a performance of 25.76 mA g. -1 Cyclic performance and coulombic efficiency at (0.2C) current density;

[0024] Figure 7 Cyclic voltammetry curves for Mg(TFSI)2 electrolyte with magnesium foil as counter and reference electrode and stainless steel foil as working electrode. 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] In existing technologies, when using simple, chloride-free magnesium salts such as Mg(PF6)2, Mg(ClO4)2, and Mg(TFSI)2 as electrolyte solutes, the high charge density of magnesium ions leads to strong solvation in the electrolyte. The desolvation process of magnesium ions requires significant energy, resulting in large battery polarization. Furthermore, the desolvation process of magnesium ions is often accompanied by solvent decomposition in the solvation sheath, forming a passivation layer on the magnesium metal surface that cannot transport magnesium ions, leading to irreversible magnesium deposition and dissolution. Although there are reports of using chloride-free magnesium hexafluoroisopropylborate Mg[B(HFIP)4]2 as an electrolyte solute and effectively depositing and dissolving magnesium, the high cost of boron-based reagents and the large molecular weight of this salt hinder the practical application of magnesium batteries.

[0029] To address the aforementioned problems, this invention provides a magnesium battery electrolyte comprising a magnesium salt and an organic solvent. The magnesium salt is hexafluoroisopropylmagnesium, and the organic solvent is one or more of the following: tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxane, 1,4-dioxane, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, and diethyl carbonate. The concentration of magnesium ions in the magnesium battery electrolyte is 0.1-2 mol / L. -1 .

[0030] Therefore, this embodiment uses simple hexafluoroisopropyl magnesium Mg(HFIP)2 as the electrolyte solute. Due to the weak coordination effect of this salt, the solvation structure of magnesium ions in the electrolyte is improved, the desolvation process is easier to occur, and no passivation layer is generated when it interacts with the magnesium metal anode, so magnesium can be effectively deposited and dissolved.

[0031] As can be seen, the magnesium battery electrolyte provided by this invention has a simple composition, with the solute containing only one simple, non-corrosive magnesium salt, and can achieve high oxidation stability under various current collector conditions (>3.7V vs. Mg / Mg). 2+ This improves the high-voltage resistance of magnesium batteries.

[0032] Based on the above scheme, another embodiment of the present invention provides a method for preparing the magnesium battery electrolyte as described above, including the steps of: adding magnesium salt to an organic solvent under an inert atmosphere, stirring evenly, and obtaining the magnesium battery electrolyte after the magnesium salt is completely dissolved, wherein the magnesium salt is hexafluoroisopropyl magnesium.

[0033] The conditions for an inert atmosphere include: water and oxygen content both below 0.1 ppm, and stirring time of 1-2 minutes.

[0034] Therefore, the preparation process of the magnesium battery electrolyte provided in this embodiment is very simple, which can be achieved by stirring at room temperature for a few minutes, greatly simplifying the experimental steps and making it easy to achieve large-scale production.

[0035] Based on the above solution, another embodiment of the present invention provides the application of the magnesium battery electrolyte as described above in the field of magnesium batteries.

[0036] A magnesium battery comprises a positive electrode, a separator, a negative electrode, and a magnesium electrolyte. This particular magnesium battery, a coin cell assembled with Mo6S8 as the positive electrode and magnesium metal as the negative electrode, achieves a capacitance of 25.76 mA g / g. -1 After 200 cycles at a current density of (0.2C), the capacity showed no significant decay.

[0037] The embodiments of the present invention utilize the characteristics of magnesium battery electrolyte, such as high conductivity, high magnesium deposition-dissolution efficiency, low polarization, high oxidation stability, and non-corrosiveness, making it suitable for matching with high-voltage cathode materials to form high-performance magnesium batteries, which have important value for promotion and application.

[0038] 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.

[0039] Example 1

[0040] This embodiment provides a method for preparing a magnesium battery electrolyte, including the following steps:

[0041] In an argon glove box with both water and oxygen content below 0.1 ppm, 7.16 g of hexafluoroisopropyl magnesium salt was weighed and added to 10 mL of ethylene glycol dimethyl ether solvent. The mixture was magnetically stirred at room temperature for 1 min until the magnesium salt was completely dissolved. The resulting liquid is the magnesium battery electrolyte, in which the concentration of magnesium ions is 2 mol / L. -1 .

[0042] Taking the magnesium battery electrolyte prepared in Example 1 as an example, using this electrolyte, stainless steel foil as the working electrode, and cleaned magnesium foil as the counter electrode and reference electrode, 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 , 2 The results are shown in the figure.

[0043] from Figure 1 , 2As can be seen from this, the magnesium battery electrolyte provided in this embodiment can effectively deposit and dissolve magnesium, and its oxidation stability is higher than 3.7V (vs. Mg / Mg) under different current collectors. 2+ ).

[0044] To further compare magnesium deposition-dissolution efficiency, Mg(TFSI)2 electrolyte, magnesium foil as counter and reference electrodes, and stainless steel foil as working electrode were used. Cyclic voltammetry curves were obtained as follows: Figure 7 The resulting graph shown is from Figure 7 It can be seen that, due to the formation of the passivation layer, the Mg(TFSI)2 electrolyte cannot deposit or dissolve magnesium. Figure 1 The deposition and dissolution peaks of magnesium can be clearly observed. This indicates that when magnesium hexafluoroisopropyltrimonium (Mg(HFIP)2)2 is used as the electrolyte solute, no passivation layer is formed when it interacts with the magnesium metal anode, and magnesium can be effectively deposited and dissolved.

[0045] Taking the magnesium battery electrolyte prepared in Example 1 as an example, the magnesium deposition-dissolution coulombic efficiency was tested. The specific test method was as follows: In an argon glove box with water and oxygen contents both below 0.1 ppm, the electrolyte, glass fiber GF / A separator, cleaned magnesium foil negative electrode, and stainless steel foil positive electrode were used to assemble a CR2016 coin cell for testing. The charge / discharge current was 0.5 mA cm⁻¹. -2 The discharge time was 30 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] from Figure 3 , 4 As can be seen, the electrolyte has a deposition and dissolution coulombic efficiency of over 95% and a polarization of around 200mV.

[0047] Figure 5 To illustrate the ionic conductivity of the magnesium battery electrolyte at different concentrations in this embodiment, from... Figure 5 It can be seen that the concentration of magnesium ions has a certain influence on ionic conductivity.

[0048] To further verify the application of this invention in full batteries, a CR2016 coin cell was assembled using the magnesium battery electrolyte, layered Mo6S8 cathode material, magnesium metal anode, and GF / A separator from this embodiment. Electrochemical tests were then performed, yielding the following results: Figure 6 The results are shown in the figure.

[0049] from Figure 6 It can be seen that the assembled magnesium metal full cell has a capacitance of 25.76 mA g. -1After 200 cycles at a current density of (0.2C), it still has 60 mA g. -1 The discharge specific capacity did not show significant capacity decay.

[0050] Example 2

[0051] This embodiment provides a method for preparing a magnesium battery electrolyte, including the following steps:

[0052] 3.58 g of hexafluoroisopropyl magnesium salt was weighed into 10 mL of ethylene glycol dimethyl ether solvent in an argon glove box with water and oxygen contents both below 0.1 ppm. The mixture was magnetically stirred at room temperature for 1 min until the magnesium salt was completely dissolved. The resulting liquid is the electrolyte, in which the concentration of magnesium ions is 1 mol / L. -1 .

[0053] Example 3

[0054] This embodiment provides a method for preparing a magnesium battery electrolyte, including the following steps:

[0055] 3.58 g of hexafluoroisopropyl magnesium salt was weighed into 10 mL of tetrahydrofuran solvent in an argon glove box with both water and oxygen content below 0.1 ppm. The mixture was then magnetically stirred at room temperature for 1 min until the magnesium salt was completely dissolved. The resulting liquid is the electrolyte, in which the concentration of magnesium ions is 1 mol / L. -1 .

[0056] Example 4

[0057] This embodiment provides a method for preparing a magnesium battery electrolyte, including the following steps:

[0058] 7.16 g of hexafluoroisopropyl magnesium salt was weighed into 10 mL of tetrahydrofuran solvent in an argon glove box with both water and oxygen content below 0.1 ppm. The mixture was then magnetically stirred at room temperature for 1 min until the magnesium salt was completely dissolved. The resulting liquid is the electrolyte, in which the concentration of magnesium ions is 2 mol / L. -1 .

[0059] Example 5

[0060] This embodiment provides a method for preparing a magnesium battery electrolyte, including the following steps:

[0061] 7.16 g of hexafluoroisopropyl magnesium salt was weighed into 10 mL of triethylene glycol dimethyl ether solvent in an argon glove box with water and oxygen contents both below 0.1 ppm. The mixture was magnetically stirred at room temperature for 1 min until the magnesium salt was completely dissolved. The resulting liquid is the electrolyte, in which the concentration of magnesium ions is 2 mol / L. -1 .

[0062] Example 6

[0063] This embodiment provides a method for preparing a magnesium battery electrolyte, including the following steps:

[0064] 7.16 g of hexafluoroisopropyl magnesium salt was weighed into 10 mL of tetraethylene glycol dimethyl ether solvent in an argon glove box with water and oxygen contents both below 0.1 ppm. The mixture was magnetically stirred at room temperature for 1 min until the magnesium salt was completely dissolved. The resulting liquid is the electrolyte, in which the concentration of magnesium ions is 2 mol / L. -1 .

[0065] 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 magnesium battery electrolyte, characterized in that, The magnesium battery electrolyte is composed of a magnesium salt and an organic solvent, wherein the magnesium salt is hexafluoroisopropylmagnesium, and the concentration of magnesium ions in the magnesium battery electrolyte is 0.1-2 mol / L. -1 The oxidation stability window of the magnesium battery electrolyte is not less than 3.7V (vs. Mg / Mg). 2+ The organic solvent is tetrahydrofuran or ethylene glycol dimethyl ether.

2. A method for preparing the magnesium battery electrolyte as described in claim 1, characterized in that, The process includes the following steps: under an inert atmosphere, magnesium salt is added to an organic solvent and stirred until it is completely dissolved to obtain the magnesium battery electrolyte, wherein the magnesium salt is hexafluoroisopropyl magnesium.

3. The preparation method according to claim 2, characterized in that, The conditions for the inert atmosphere include: water and oxygen content both below 0.1 ppm.

4. The preparation method according to claim 2, characterized in that, Stirring time is 1-2 minutes.

5. The application of the magnesium battery electrolyte as described in claim 1 in the field of magnesium batteries.

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