Magnesium battery electrolyte and its preparation method and magnesium battery

Abstract

This application discloses a magnesium battery electrolyte, its preparation method, and a magnesium battery. The magnesium battery electrolyte of this application comprises: a non-aqueous solvent, selected from imidazole ionic liquids, pyrrole ionic liquids, piperidine ionic liquids, ether compounds, ester compounds, pyridine compounds, nitrile compounds, sulfone compounds, and ketone compounds or combinations thereof; an electron-deficient boron-containing compound; and a magnesium electrolyte salt having the following chemical formula: [R] p Mg m X n [TFSI] 2m‑n ·M q The synergistic effect among the components endows it with good stability, strong water resistance and impurity resistance, and excellent electrochemical performance. At the same time, the magnesium battery electrolyte containing electron-deficient boron compounds can promote the reversible deposition and dissolution of magnesium, reduce overpotential, inhibit the formation of a passivation layer of magnesium salt on the anode surface, and improve the charge-discharge specific capacity and cycle stability of magnesium batteries.

Description

Technical Field

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

[0002] Magnesium is abundant, inexpensive, environmentally friendly, has relatively stable physicochemical properties, and is not prone to dendrite growth. It also possesses a very high theoretical volumetric capacity (3833 mA·h / cm³). 3 Magnesium battery systems, which use metallic magnesium as the negative electrode material, have advantages such as high energy density, low cost, and high safety, and are one of the new energy storage systems with great development potential.

[0003] However, due to the high charge density and low reduction potential (-2.37V vs. SHE) of magnesium ions, most organic solvents and magnesium salts react with metallic magnesium, resulting in the accumulation of a large amount of passivating material in the magnesium anode interface layer, which is detrimental to the operation of magnesium batteries. Furthermore, the magnesium anode interface is highly susceptible to impurities (such as trace amounts of water, oxygen, and carbon dioxide), which may cause short circuits and other problems, affecting the performance of magnesium batteries. Summary of the Invention

[0004] In view of this, this application provides a magnesium battery electrolyte, a method for preparing the same, and a magnesium battery, aiming to provide an electrolyte that improves the reversible deposition-dissolution performance of magnesium.

[0005] In a first aspect, embodiments of this application provide a magnesium battery electrolyte, comprising:

[0006] The non-aqueous solvent is selected from imidazole ionic liquids, pyrrole ionic liquids, piperidine ionic liquids, ether compounds, ester compounds, pyridine compounds, nitrile compounds, sulfone compounds and ketone compounds or combinations thereof;

[0007] Electron-deficient boron compounds; and

[0008] Magnesium electrolyte salts with the following chemical formulas:

[0009] [R p Mg m X n [TFSI] 2m-n ·M q ,

[0010] Wherein, X is selected from halide ions;

[0011] TFSI represents bis(trifluoromethanesulfonyl)imide ion;

[0012] R is independently selected from alkyl, fluoroalkyl, and aryl groups;

[0013] M is a molecular ligand;

[0014] m is any integer selected from 1 to 6, n is any integer selected from 0 to 6, p is any integer selected from 0 to 6, q is any integer selected from 0 to 20, and 2m-n>0.

[0015] According to one embodiment of this application, the magnesium battery electrolyte comprises: 0.1-10 mol / L of the magnesium-containing electrolyte salt and 0.1-10 mol / L of an electron-deficient boron-containing compound.

[0016] According to one aspect of the present application, the magnesium battery electrolyte comprises: 0.1-3 mol / L of the magnesium-containing electrolyte salt and 0.1-3 mol / L of an electron-deficient boron-containing compound.

[0017] According to an embodiment of one aspect of this application, the imidazole ionic liquid is selected from 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonic acid)imine salt, 1-methyl-3-methylimidazolium bromide salt, or a combination thereof.

[0018] According to an embodiment of one aspect of this application, the pyrrole ionic liquid is selected from N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imine salt, N-alkylN-methylpyrrolidine bromotetrafluoroborate, N-alkylN-methylpyrrolidine hexafluorophosphate, or a combination thereof.

[0019] According to an embodiment of one aspect of this application, the piperidine ionic liquid is selected from N-butyl-N-methylpiperidine bis(trifluoromethanesulfonyl)imide salt, N-octylpyridinium salt, N-hexylpyridinium bromide salt, or combinations thereof.

[0020] According to one aspect of the embodiments of this application, the ether compound is selected from tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dioxane, polyethylene glycol dimethyl ether, or combinations thereof.

[0021] According to an embodiment of one aspect of this application, the ester compound is selected from ethyl acetate, methyl acetate, phenyl acetate, or combinations thereof.

[0022] According to an embodiment of one aspect of this application, the pyridine compound is selected from pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2,6-dichloropyridine, 2-aminopyridine, or combinations thereof.

[0023] According to an embodiment of one aspect of this application, the nitrile compound is selected from acetonitrile, acrylonitrile, methacrylonitrile, or a combination thereof.

[0024] According to an embodiment of one aspect of this application, the sulfone compound is selected from dimethyl sulfone, phenylethyl sulfone, diethyl sulfone, or combinations thereof.

[0025] According to an embodiment of one aspect of this application, the electron-deficient boron-containing compound is selected from tris(2,2,2-trifluoroethyl) borate / trialkylarylborates, tris(pentafluorobenzene)borane, or combinations thereof.

[0026] According to an embodiment of one aspect of this application, X is independently selected from fluoride ions, chloride ions, bromide ions, and iodide ions.

[0027] According to an embodiment of one aspect of this application, the molecular ligand M is independently selected from the non-aqueous solvent molecules.

[0028] According to one aspect of an embodiment of this application, p is selected from 1, 2, 3, 4, 5, and 6.

[0029] According to one aspect of the embodiments of this application, the magnesium-containing electrolyte salt is selected from MgTFSI2, [C2H5MgCl][TFSI], [C2H5MgCl][TFSI]·THF, [C3H7MgCl][TFSI], [C3H7MgCl][TFSI]·DME or a combination thereof.

[0030] According to one aspect of this application, the non-aqueous solvent is ethylene glycol dimethyl ether, and the magnesium-containing electrolyte salt is MgTFSI2.

[0031] Secondly, embodiments of this application provide a method for preparing the magnesium battery electrolyte of the first aspect, comprising:

[0032] Provides an electrolyte containing magnesium electrolyte salts and a non-aqueous solvent;

[0033] The electrolyte and an electron-deficient boron-containing compound are mixed at a temperature of 25℃-200℃ to obtain a magnesium battery electrolyte; optionally, the mixing time is 0.5-48h.

[0034] According to another embodiment of this application, the method for preparing the electrolyte includes:

[0035] An anhydrous magnesium salt and a non-aqueous solvent in liquid state are mixed to obtain a mixture, wherein the anhydrous magnesium salt is selected from magnesium chloride, magnesium fluoride, magnesium bromide, magnesium iodide, bis(hexamethyldisilazon) magnesium, bis(trifluoromethanesulfonylimide) magnesium and Grignard reagent or a combination thereof.

[0036] The mixture is reacted at a temperature of 25℃-200℃ to generate magnesium-containing electrolyte salt in the mixture. Optionally, it is cooled to obtain an electrolyte. Optionally, the reaction time is 3-48h and the target cooling temperature is -30~25℃.

[0037] Thirdly, embodiments of this application provide a magnesium battery, comprising: a magnesium battery electrolyte of the first aspect or a magnesium battery electrolyte obtained by the preparation method of the second aspect.

[0038] Compared with the prior art, this application has at least the following beneficial effects:

[0039] (1) The magnesium battery electrolyte provided in this application has good stability, strong water resistance and impurity resistance and excellent electrochemical performance due to the synergistic effect between the components. At the same time, the magnesium battery electrolyte containing electron-deficient boron compounds can promote the reversible deposition-dissolution of magnesium, reduce overpotential, inhibit the formation of passivation layer of magnesium salt on the anode surface, and improve the charge-discharge specific capacity and cycle stability of magnesium battery.

[0040] (2) The preparation method of magnesium battery electrolyte provided in this application is simple and easy to implement, has low equipment requirements, is compatible with existing processes, and has great potential for large-scale application.

[0041] (3) The magnesium battery provided in this application has good charge-discharge specific capacity and long cycle life. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0043] Figure 1 The voltage-time curve of the magnesium battery of Embodiment 1 of this application, showing the deposition-dissolution of metallic magnesium, is shown.

[0044] Figure 2 The voltage-time curve of the magnesium deposition-dissolution process of the magnesium battery in Comparative Example 1 of this application is shown.

[0045] Figure 3 The following is a voltage-time curve of magnesium deposition-dissolution in the electrolyte of the magnesium battery of Example 1 of this application when there is 800 ppm of H2O interference from impurities.

[0046] Figure 4 The voltage-time curve of deposited-dissolved metallic magnesium is shown in the electrolyte of the magnesium battery of Comparative Example 1 of this application when there is 800 ppm of H2O interference from impurities.

[0047] Figure 5 The charge-discharge cycle-specific capacity spectra of magnesium batteries of Example 1 and Comparative Example 1 of this application are shown;

[0048] Figure 6 The interfacial X-ray photoelectron spectrum of the magnesium anode of Example 1 of this application after cycling in an electrolyte containing an electron-deficient boron compound is shown: C 1s;

[0049] Figure 7 The interfacial X-ray photoelectron spectrum of the magnesium anode of Example 1 of this application after cycling in an electrolyte containing an electron-deficient boron compound is shown: F 1s;

[0050] Figure 8 The interfacial X-ray photoelectron spectrum of the magnesium anode of Comparative Example 1 of this application after cycling in an electron-deficient boron compound electrolyte is shown: C 1s;

[0051] Figure 9 The interfacial X-ray photoelectron spectrum of the magnesium anode of Comparative Example 1 of this application after cycling in an electron-deficient boron compound electrolyte is shown: F 1s. Detailed Implementation

[0052] To make the purpose, technical solution, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the embodiments described in this specification are merely for explaining this application and are not intended to limit it.

[0053] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0054] In the description of this application, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more.

[0055] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0056] Currently, among the developed magnesium battery electrolytes, those containing bis(trifluoromethanesulfonyl)imide ions and magnesium ions have high solubility in organic solvents and high ionic conductivity. Therefore, magnesium battery electrolytes synthesized based on MgTFSI2 salts have been extensively studied.

[0057] However, in such electrolyte systems, magnesium at the negative electrode still suffers from problems such as high deposition and dissolution overpotential, low battery discharge capacity, and poor stability. For example, it is susceptible to the influence of impurities (such as small amounts of water, oxygen, carbon dioxide, etc.), which prevent the effective conduction of magnesium ions, leading to high charge and discharge overpotential, uneven deposition and dissolution, and even short circuits.

[0058] On the other hand, in magnesium batteries, most organic solvents and magnesium salts react with metallic magnesium, easily forming a passivation layer on the magnesium metal surface that hinders magnesium ion conduction. Due to the presence of this passivation layer, the electrode-electrolyte interface can become unstable during prolonged charge-discharge cycles, preventing effective magnesium ion conduction. This can also lead to problems such as high overpotential during charge-discharge, uneven deposition-dissolution, and even short circuits, ultimately causing magnesium battery failure.

[0059] Based on this, the inventors conducted extensive research to provide a magnesium battery electrolyte that can promote the reversible deposition-dissolution of magnesium, reduce overpotential, strip magnesium salts to form a passivation layer on the anode surface, and at the same time make the electrolyte have certain water resistance properties, thereby improving the charge-discharge specific capacity and cycle life of magnesium batteries.

[0060] Magnesium battery electrolyte

[0061] In a first aspect, embodiments of this application provide a magnesium battery electrolyte, comprising:

[0062] The non-aqueous solvent is selected from imidazole ionic liquids, pyrrole ionic liquids, piperidine ionic liquids, ether compounds, ester compounds, pyridine compounds, nitrile compounds, sulfone compounds and ketone compounds or combinations thereof;

[0063] Electron-deficient boron compounds; and

[0064] Magnesium electrolyte salts with the following chemical formulas

[0065] [R p Mg m X n [TFSI] 2m-n ·M q ,

[0066] Wherein, X is selected from halide ions;

[0067] TFSI represents bis(trifluoromethanesulfonyl)imide ion;

[0068] R is independently selected from alkyl, fluoroalkyl, and aryl groups;

[0069] M is a molecular ligand;

[0070] m is any integer selected from 1 to 6, n is any integer selected from 0 to 6, p is any integer selected from 0 to 6, q is any integer selected from 0 to 20, and 2m-n>0.

[0071] According to embodiments of this application, the synergistic effect of electron-deficient boron-containing compounds with non-aqueous solvents and non-magnesium electrolyte salts promotes reversible deposition-dissolution of magnesium in the electrolyte, reduces overpotential, and effectively strips the passivation layer formed by magnesium salts on the anode surface. This gives the magnesium battery electrolyte excellent magnesium deposition-dissolution performance and good stability, thereby endowing the magnesium battery with high charge-discharge specific capacity and cycle performance. Furthermore, the electron-deficient boron-containing compounds also give the magnesium battery electrolyte strong water resistance.

[0072] Related technologies indicate that while magnesium metal is relatively stable as an anode, it can still react with most reducible compounds such as hydrocarbons, alcohols, phenols, amines, aldehydes, water, carbon dioxide, and oxygen. When these solvents are used in the electrolyte solution, a passivation layer that is both electron- and ion-insulating forms on the surface of the magnesium metal anode, hindering the reaction of Mg. 2+ The migration of these components is detrimental to fully realizing the battery's performance.

[0073] Through research and improvement by the inventors, an electron-deficient boron-containing compound was added to the electrolyte of a magnesium battery. Under the action of the compound and other components, the reversible deposition-dissolution of magnesium by a non-aqueous solvent can be achieved. Furthermore, the insulating phase formed at the interface between the negative electrode magnesium and the electrolyte is stripped away by the added electron-deficient boron-containing compound, thereby promoting the improvement of the charge-discharge specific capacity and cycle stability of the magnesium battery.

[0074] The mechanism by which electron-deficient boron compounds are added to strip the insulating phase is as follows: Mg in magnesium-containing electrolyte salts 2+ X - TFSI - R and molecular ligands form ion-pair structures, which can promote the formation of non-aqueous solvents and TFSI in magnesium battery electrolytes. - The decomposition on the magnesium anode surface leads to the accumulation of a large amount of passivating substances such as MgO and MgF2 in the magnesium anode interface layer, thereby deteriorating the magnesium ion interfacial transport performance. However, by adding an electron-deficient boron-containing compound, which can react with the electron-rich MgO and MgF2 in the magnesium anode interface layer, the content of passivating substances in the magnesium anode interface layer is reduced, thus achieving gradual stripping and further improving the electrolyte deposition-dissolution performance of metallic magnesium. In some embodiments, the electron-deficient boron-containing compound is selected from tris(2,2,2-trifluoroethyl) borate / trialkylarylborate, tris(pentafluorobenzene)borane, or combinations thereof.

[0075] Furthermore, trace amounts of water impurities in the magnesium battery electrolyte can be reduced on the surface of the magnesium anode and form a MgO passivation layer. Electron-deficient boron compounds can react with this MgO passivation layer, stripping the MgO from the magnesium anode surface and thus protecting it from passivation. Therefore, magnesium battery electrolytes containing electron-deficient boron compounds can withstand the interference of water impurities without being passivated, thus giving the magnesium battery electrolyte excellent water resistance.

[0076] In some embodiments, the imidazole ionic liquid is selected from 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonic acid)imine salt, 1-methyl-3-methylimidazolium bromide salt, or combinations thereof.

[0077] In some embodiments, the pyrrole ionic liquid is selected from N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imine salt, N-alkylN-methylpyrrolidine bromotetrafluoroborate, N-alkylN-methylpyrrolidine hexafluorophosphate, or combinations thereof.

[0078] In some embodiments, the piperidine ionic liquid is selected from N-butyl-N-methylpiperidine bis(trifluoromethanesulfonyl)imine salt, N-octylpyridine salt, N-hexylpyridine bromide salt, or combinations thereof.

[0079] In some embodiments, the ether compound is selected from tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dioxane, polyethylene glycol dimethyl ether, or combinations thereof.

[0080] In some embodiments, the ester compound is selected from ethyl acetate, methyl acetate, phenyl acetate, or combinations thereof.

[0081] In some embodiments, the pyridine compound is selected from pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2,6-dichloropyridine, 2-aminopyridine, or combinations thereof.

[0082] In some embodiments, the nitrile compound is selected from acetonitrile, acrylonitrile, methacrylonitrile, or combinations thereof.

[0083] In some embodiments, the sulfone compound is selected from dimethyl sulfone, phenylethyl sulfone, diethyl sulfone, or combinations thereof.

[0084] According to embodiments of this application, the aforementioned non-aqueous solvent possesses good conductivity and a stable electrochemical potential window, which can promote the activity of Mg in the electrolyte. 2+ The migration of these molecules improves the cycle stability of the battery.

[0085] In some embodiments, X is independently selected from fluoride ions, chloride ions, bromide ions, and iodide ions.

[0086] In some embodiments, the molecular ligand M is independently selected from the non-aqueous solvent molecules.

[0087] According to embodiments of this application, the molecular ligand M in the above chemical formula contributes to the reversible and stable operation of the magnesium anode in the magnesium battery electrolyte.

[0088] In some embodiments, in the chemical formula [Mg m X n R p [TFSI] 2m-n ·M q In this context, m can be arbitrarily selected from 1, 2, 3, 4, 5, 6, or any other range formed by any two of the aforementioned endpoints. n can be arbitrarily selected from 0, 1, 2, 3, 4, 5, 6, or any other range formed by any two of the aforementioned endpoints.

[0089] In some embodiments, p is selected from 1, 2, 3, 4, 5, and 6. p can be arbitrarily selected from 0, 1, 2, 3, 4, 5, 6, or other ranges consisting of any two of the above endpoints. q can be arbitrarily selected from 1, 2, 3, 4, 8, 12, 16, 20, or other ranges consisting of any two of the above endpoints.

[0090] In some embodiments, the magnesium electrolyte salt is selected from MgTFSI2, [C2H5MgCl][TFSI], [C2H5MgCl][TFSI]·THF, [C3H7MgCl][TFSI], [C3H7MgCl][TFSI]·DME, or a combination thereof.

[0091] In some embodiments, the non-aqueous solvent is ethylene glycol dimethyl ether, and the magnesium-containing electrolyte salt is MgTFSI2.

[0092] According to embodiments of this application, when the non-aqueous solvent is ethylene glycol dimethyl ether and the halide ion is chloride ion, the resulting contact ions decompose the structure, which is very detrimental to the performance of the magnesium anode. However, the addition of an electron-deficient boron-containing compound optimizes the reversible deposition-dissolution of magnesium and reduces the overpotential by stripping the magnesium anode passivation layer, while simultaneously giving the electrolyte excellent water resistance, demonstrating significant effects. In some embodiments, the magnesium battery electrolyte comprises: 0.1-10 mol / L of the aforementioned magnesium electrolyte salt and 0.1-10 mol / L of the electron-deficient boron-containing compound.

[0093] According to embodiments of this application, the concentration of the magnesium-containing electrolyte salt can be selected from 0.1 mol / L, 2 mol / L, 4 mol / L, 6 mol / L, 8 mol / L, 10 mol / L, or other ranges formed by any two of the above endpoints. The concentration of the electron-deficient boron-containing compound is selected from 0.1 mol / L, 2 mol / L, 4 mol / L, 6 mol / L, 8 mol / L, 10 mol / L, or other ranges formed by any two of the above endpoints. The concentration of the magnesium-containing electrolyte salt or the electron-deficient boron-containing compound in the magnesium battery electrolyte can also be any combination of the above values.

[0094] According to embodiments of this application, within the above-mentioned concentration range, magnesium-containing electrolyte salts exhibit high efficiency in non-aqueous solvents, and the viscosity of the magnesium battery electrolyte is moderate, ranging from 0.2 to 50 Pa·s, or even 0.2 Pa·s, 0.4 Pa·s, 1 Pa·s, 5 Pa·s, 10 Pa·s, 20 Pa·s, 40 Pa·s, 50 Pa·s, or other ranges formed by any two of the above endpoints. Within the above-mentioned concentration or viscosity range, it is advantageous for Mg... 2+ The transport of ions is affected by the concentration of magnesium electrolyte salts. If the concentration of magnesium electrolyte salts is below 0.1 mol / L, the ionic conductivity is low, resulting in greater ohmic polarization of the magnesium battery. However, when the concentration of electrolyte salts is above 10 mol / L, the electrolyte viscosity increases, the concentration polarization of the battery increases, and the mass transfer and diffusion of ions are hindered.

[0095] In some embodiments, the magnesium battery electrolyte comprises: 0.1-3 mol / L of the magnesium-containing electrolyte salt and 0.1-3 mol / L of an electron-deficient boron-containing compound.

[0096] According to the embodiments of this application, the components contained in the magnesium battery electrolyte are within the above-mentioned range, resulting in a suitable viscosity for the magnesium battery electrolyte, which can further improve the performance of magnesium batteries. 2+ This facilitates the transport of ions and improves ionic conductivity.

[0097] Preparation method of magnesium battery electrolyte

[0098] Secondly, embodiments of this application provide a method for preparing the magnesium battery electrolyte of the first aspect, comprising:

[0099] Provides an electrolyte containing magnesium electrolyte salts and a non-aqueous solvent;

[0100] The electrolyte and an electron-deficient boron-containing compound are mixed at a temperature of 25℃-200℃ to obtain a magnesium battery electrolyte; optionally, the mixing time is 0.5-48h.

[0101] In some embodiments, the mixture is cooled after mixing, with a target cooling temperature of 0–25°C.

[0102] In some embodiments, the method for preparing the electrolyte includes:

[0103] An anhydrous magnesium salt and a non-aqueous solvent in liquid state are mixed to obtain a mixture, wherein the anhydrous magnesium salt is selected from magnesium chloride, magnesium fluoride, magnesium bromide, magnesium iodide, bis(hexamethyldisilazon) magnesium, bis(trifluoromethanesulfonylimide) magnesium and Grignard reagent or a combination thereof.

[0104] The mixture is reacted at a temperature of 25℃-200℃ to generate magnesium-containing electrolyte salt in the mixture. Optionally, it is cooled to obtain an electrolyte. Optionally, the reaction time is 3-48h and the target cooling temperature is -30~25℃.

[0105] In some embodiments, the mixture is reacted in an environment with a water content of <0.1 ppm, an oxygen content of <0.1 ppm, and filled with an inert gas, at a temperature of 25°C to 200°C to generate a magnesium-containing electrolyte salt in the mixture, and optionally cooled to obtain an electrolyte.

[0106] According to embodiments of this application, during the preparation of magnesium battery electrolyte, anhydrous magnesium salt and non-aqueous solvent form a solvation structure with contact ion pairs, thereby promoting the dissolution of anhydrous magnesium salt.

[0107] In some embodiments, the inert gas is selected from helium, argon, or a combination thereof.

[0108] In some embodiments, the molar ratio of the anhydrous magnesium salt to the electron-deficient boron compound is 1:(0.1-4). For example, the molar ratio of the anhydrous magnesium salt to the electron-deficient boron compound may be 1:0.1, 1:1, 1:2, 1:3, 1:4, or any other range consisting of any two of the above endpoints.

[0109] According to the embodiments of this application, the above preparation method is simple, and the prepared magnesium battery electrolyte has good miscibility, stable system, and strong water resistance, thereby improving the battery performance of magnesium batteries.

[0110] Magnesium batteries

[0111] Thirdly, embodiments of this application provide a magnesium battery, comprising: a magnesium battery electrolyte of the first aspect or a magnesium battery electrolyte obtained by the preparation method of the second aspect.

[0112] According to an embodiment of this application, a magnesium battery includes an electrode assembly and an electrolyte. The electrode assembly includes a negative electrode, a positive electrode, and a separator disposed between the negative electrode and the positive electrode. The negative electrode includes a negative electrode current collector, which may be made of magnesium metal, a magnesium alloy, or a combination thereof. The negative electrode also includes a negative electrode active material and a binder.

[0113] In some embodiments, the positive electrode comprises a metallic conductive material or a non-metallic conductive material. The metallic conductive material can be a metal foil or a porous metal plate, such as foils or porous plates of metals or alloys thereof, such as aluminum, copper, nickel, titanium, iron, etc. The non-metallic conductive material can be conductive carbon black or conductive graphite.

[0114] In some embodiments, the positive electrode may further include a positive electrode active material, a conductive agent, and a binder. This application does not impose particular limitations on the materials of the conductive agent and binder; conventional materials can be used.

[0115] In some embodiments, the positive electrode active material can be an inorganic transition metal oxide, sulfide, or boride; preferably, the positive electrode active material is CuS. In some embodiments, the positive electrode is a mixture of Cu and CuS; the positive electrode is a mixture of conductive carbon black and CuS coated on its surface.

[0116] In some embodiments, the membrane may be a polyolefin-based fine porous membrane, such as polypropylene or polyethylene. In some embodiments, the binder may be a fluorinated polymer material, such as vinylidene fluoride (PVdF), hexafluoropropylene (HFP), or chlorotrifluoroethylene (CTFE), tetrafluoroethylene (PTFE), or copolymers of these polymer materials, such as copolymers of vinylidene fluoride and hexafluoropropylene, etc., are used as binders.

[0117] The magnesium battery according to the embodiments of this application, due to the inclusion of the magnesium battery electrolyte in any of the embodiments of the first aspect described above, exhibits good stability, strong water resistance, and excellent electrochemical performance through the synergistic effect of its components. Furthermore, it promotes reversible deposition-dissolution of magnesium, reduces overpotential, strips magnesium salts to form a passivation layer on the anode surface, and improves the charge-discharge specific capacity and cycle stability of the magnesium battery. Therefore, the magnesium battery of the embodiments of this application can be applied to energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in multiple fields such as power tools, military equipment, and aerospace.

[0118] Example

[0119] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0120] Example 1

[0121] Preparation of magnesium battery electrolyte: In a glove box filled with argon gas and containing less than 1 ppm of oxygen and water, 0.6 mol / L anhydrous magnesium chloride (MgCl2), 0.3 mol / L anhydrous magnesium bis(trifluoromethanesulfonyl)imide (MgTFSI2), and dimethyl ethylene glycol ether were mixed and reacted at 60 °C for 24 h. After cooling to 25 °C, the magnesium battery electrolyte was obtained. Then, an electron-deficient boron-containing compound was mixed with the electrolyte at a volume ratio of 2:100 to dimethyl ethylene glycol ether; the mixture was reacted at 25 °C for 2 h to obtain the magnesium battery electrolyte.

[0122] Preparation of the negative electrode: Magnesium foil is used as the negative electrode of the battery. Before use, the magnesium foil needs to be polished to remove the surface passivation layer.

[0123] Preparation of the positive electrode: CuS powder, conductive carbon black and binder polyvinylidene fluoride were mixed and stirred into a slurry at a mass ratio of 7:2:1. The slurry was then coated onto pyrolytic graphite paper and baked at 60°C for 24 hours to obtain the positive electrode material.

[0124] Preparation of the separator: A 7 μm thick porous polyethylene (PE) film was used as the separator.

[0125] Preparation of magnesium battery: The preparation of magnesium full cell is completed by assembling CuS positive electrode, electrolyte, separator and magnesium sheet negative electrode in sequence.

[0126] Example 2

[0127] The difference between this embodiment and Embodiment 1 is that:

[0128] In a glove box filled with argon and containing less than 1 ppm of oxygen and water, 0.1 mol / L anhydrous magnesium ethyl chloride (C2H5MgCl), 0.2 mol / L anhydrous magnesium bis(trifluoromethanesulfonyl)imide (MgTFSI2), and dimethyl ethylene glycol ether were mixed and reacted at 60°C for 24 h. The mixture was then cooled to 25°C to obtain a magnesium battery electrolyte. Subsequently, 0.1 mol / L of an electron-deficient boron compound was mixed with the electrolyte; the reaction was carried out at 25°C for 2 h to obtain the magnesium battery electrolyte.

[0129] Example 3

[0130] The difference between this embodiment and Embodiment 1 is that:

[0131] In a glove box filled with argon and containing less than 1 ppm of oxygen and water, 10 mol / L anhydrous magnesium ethyl chloride (C2H5MgCl), 10 mol / L anhydrous magnesium bis(trifluoromethanesulfonyl)imide (MgTFSI2), and tetrahydrofuran were mixed and reacted at 60°C for 24 h. The mixture was then cooled to 25°C to obtain a magnesium battery electrolyte. Subsequently, 3 mol / L of an electron-deficient boron-containing compound was mixed with the electrolyte; the reaction was carried out at 25°C for 2 h to obtain the magnesium battery electrolyte.

[0132] Comparative Example 1

[0133] The difference between this comparative example and Example 1 is that:

[0134] Preparation of magnesium battery electrolyte: In a glove box filled with argon and containing less than 1 ppm of oxygen and water, 0.6 mol / L anhydrous magnesium chloride (MgCl2), 0.3 mol / L anhydrous magnesium bis(trifluoromethanesulfonyl)imide (MgTFSI2) and ethylene glycol dimethyl ether were mixed and reacted at 60°C for 24 h. The mixture was then cooled to 25°C to obtain the magnesium battery electrolyte.

[0135] Comparative Example 2

[0136] The difference between this embodiment and Embodiment 1 is that:

[0137] In a glove box filled with argon and containing less than 1 ppm of oxygen and water, 0.1 mol / L anhydrous magnesium ethyl chloride (C2H5MgCl), 0.2 mol / L anhydrous magnesium bis(trifluoromethanesulfonyl)imide (MgTFSI2) and dimethyl ethylene glycol ether were mixed and reacted at 60°C for 24 h. The mixture was then cooled to 25°C to obtain the magnesium battery electrolyte.

[0138] Comparative Example 3

[0139] The difference between this embodiment and Embodiment 1 is that:

[0140] In a glove box filled with argon and containing less than 1 ppm of oxygen and water, 10 mol / L anhydrous magnesium ethyl chloride (C2H5MgCl), 10 mol / L anhydrous magnesium bis(trifluoromethanesulfonyl)imide (MgTFSI2) and tetrahydrofuran were mixed and reacted at 60°C for 24 h. The mixture was then cooled to 25°C to obtain the magnesium battery electrolyte.

[0141] Test section

[0142] 1) Polarization voltage test of deposited-dissolved metallic magnesium

[0143] Electrochemical tests were performed on the magnesium batteries of Example 1 and Comparative Example 1, and their potential and cycle life were measured, respectively. The current density was 0.5 mA cm⁻¹.-2 The battery capacity is 0.5mAh cm. -2 .

[0144] To test the performance of magnesium deposition-dissolution in magnesium battery electrolytes, the deposition-dissolution overpotential of magnesium in the electrolytes of Example 1 and Comparative Example 1 was tested under conditions of both electron-deficient boron compounds and electrolytes, as follows: Figure 1-2 As shown. By Figure 2 It can be seen that, in Comparative Example 1, when there is no electron-deficient boron-containing compound, the average reversible deposition-dissolution overpotential of magnesium ions in the electrolyte is 0.3V, and the cycle life is less than 320h; from Figure 1 It can be seen that after adding an electron-deficient boron-containing compound to the electrolyte of Example 1, the reversible deposition and dissolution overpotential of magnesium ions is less than 0.2V, and the cycle life is extended to 400h. This indicates that the additive helps to reduce the reversible deposition and dissolution overpotential of magnesium ions and improve the performance of magnesium anode.

[0145] To investigate the effect of water containing impurities on magnesium battery electrolytes, 800 ppm of tap water containing impurities was added to the magnesium battery electrolytes in Example 1 and Comparative Example 1. The results are as follows: Figure 3-4 As shown, by Figure 4 It can be seen that the magnesium battery electrolyte in Comparative Example 1 does not have water-resistant properties. When 800 ppm of water impurities are introduced into the system, the magnesium ion deposition dissolution curve becomes extremely unstable, the overpotential of the magnesium ion deposition solvent increases, and the cycle life becomes shorter. Figure 3 It can be seen that in Example 1, the magnesium battery electrolyte with added electron-deficient boron compounds still exhibits stable and reversible deposition and dissolution of magnesium ions after the introduction of 800 ppm of water impurities, indicating that the electron-deficient boron compounds endow the electrolyte with water-resistant properties.

[0146] 2) Measurement of specific capacity and coulombic efficiency of magnesium batteries

[0147] The magnesium batteries of Example 1 and Comparative Example 1 were subjected to constant current charge-discharge tests. The voltage range of the battery test was 0.1-2.0V, and the battery test rate was 1C. The results were as follows: Figure 5 The results are shown.

[0148] 3) X-ray photoelectron spectroscopy test

[0149] X-ray photoelectron spectroscopy was performed on the magnesium negative electrode sheets of the magnesium batteries in Example 1 and Comparative Example 1 after cycling to obtain... Figure 5-9 As shown, where, Figures 6-7 The energy spectrum of Example 1 is shown below. Figures 8-9 This is the energy spectrum of Comparative Example 1. Figure 6-9In the test, from 0 min to 4 min, the peak intensity of MgO and MgF2 on the surface of the negative electrode magnesium sheet in Example 1 decreased significantly more than that in the negative electrode magnesium sheet in Comparative Example 1, which proved the stripping effect of electron-deficient boron compounds on MgO and MgF2 in the magnesium negative electrode interface.

[0150] In summary, the difference between Example 1 and Comparative Example 1 is that Example 1 added an electron-deficient boron compound. The above experiments have shown that the electron-deficient boron compound can make the magnesium battery electrolyte more stable, more resistant to water and impurities, and have better electrochemical performance, thus giving the magnesium battery higher charge-discharge specific capacity and cycle performance.

[0151] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A magnesium battery electrolyte comprising: a non-aqueous solvent selected from the group consisting of imidazolium ionic liquid, pyrrolidinium ionic liquid, piperidinium ionic liquid, ether compound, ester compound, pyridinium compound, nitrile compound, sulfone compound, and ketone compound, or a combination thereof; an electron-deficient boron-containing compound selected from the group consisting of tris(2,2,2-trifluoroethyl) borate, tris(pentafluorophenyl) borane, or a combination thereof; and a magnesium-containing electrolyte salt having a chemical formula of: [R p Mg m X n ][TFSI] 2m-n ·M q , wherein X is selected from the group consisting of halide; TFSI represents bis(trifluoromethanesulfonyl)imide ion; R is independently selected from the group consisting of alkyl, fluoroalkyl, and aryl; M is a molecular complexing agent; m is an arbitrary integer selected from 1 to 6, n is an arbitrary integer selected from 0 to 6, p is an arbitrary integer selected from 0 to 6, q is an arbitrary integer selected from 0 to 20, and 2m-n > 0.

2. The magnesium battery electrolyte of claim 1, wherein: the imidazolium ionic liquid is selected from the group consisting of 1-ethyl-3- methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-methyl-3-methylimidazolium bromide, or a combination thereof; the pyrrolidinium ionic liquid is selected from the group consisting of N-butyl-N- methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, N-alkyl N-methylpyrrolidinium bromide tetrafluoroborate, N-alkyl N-methylpyrrolidinium hexafluorophosphate, or a combination thereof; the piperidinium ionic liquid is selected from the group consisting of N-butyl-N- methylpiperidinium bis(trifluoromethanesulfonyl)imide, N-octylpyridinium bromide, N- hexylpyridinium bromide, or a combination thereof; the ether compound is selected from the group consisting of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dioxane, polyethylene glycol dimethyl ether, or a combination thereof; the ester compound is selected from the group consisting of ethyl acetate, methyl acetate, phenyl acetate, or a combination thereof; the pyridinium compound is selected from the group consisting of pyridine, 2- methylpyridine, 3-methylpyridine, 4-methylpyridine, 2,6-dichloropyridine, 2- aminopyridine, or a combination thereof; the nitrile compound is selected from the group consisting of acetonitrile, propionitrile, methacrylonitrile, or a combination thereof; the sulfone compound is selected from the group consisting of dimethyl sulfone, phenyl ethyl sulfone, diethyl sulfone, or a combination thereof.

3. The magnesium battery electrolyte of claim 1, wherein, X is independently selected from the group consisting of fluoride, chloride, bromide, iodide; and / or, the molecular complexing agent M is independently selected from the non-aqueous solvent.

4. The magnesium battery electrolyte of claim 1, wherein, p is selected from the group consisting of 1, 2, 3, 4, 5, and 6; and / or, the magnesium-containing electrolyte salt is selected from the group consisting of MgTFSI2, [C2H5MgCl][TFSI], [C2H5MgCl][TFSI]·THF, [C3H7MgCl][TFSI], [C3H7MgCl][TFSI]·DME, or a combination thereof.

5. The magnesium battery electrolyte according to any one of claims 1 to 4, characterized in that, the non-aqueous solvent is ethylene glycol dimethyl ether, and the magnesium- containing electrolyte salt is MgTFSI2.

6. The magnesium battery electrolyte according to any one of claims 1 to 4, characterized in that the magnesium battery electrolyte comprises 0.1-10 mol / L of the magnesium- containing electrolyte salt and 0.1-10 mol / L of the electron-deficient boron-containing compound.

7. The magnesium battery electrolyte of claim 6, wherein, The magnesium battery electrolyte comprises 0.1-3 mol / L of the magnesium-containing electrolyte salt and 0.1-3 mol / L of the electron-deficient boron-containing compound.

8. A method for preparing the magnesium battery electrolyte according to any one of claims 1-7, comprising: providing an electrolyte comprising a magnesium-containing electrolyte salt and a non-aqueous solvent; mixing the electrolyte and an electron-deficient boron-containing compound at a temperature of 25-200°C to obtain the magnesium battery electrolyte.

9. The method for preparing the magnesium battery electrolyte according to claim 8, wherein the mixing of the electrolyte and the electron-deficient boron-containing compound at a temperature of 25-200°C to obtain the magnesium battery electrolyte is performed for 0.5-48 h.

10. The method for preparing the magnesium battery electrolyte according to claim 8 or 9, characterized in that, The method for preparing the electrolyte comprises: mixing anhydrous magnesium salt and a non-aqueous solvent in liquid state to obtain a mixture, wherein the anhydrous magnesium salt is selected from magnesium chloride, magnesium fluoride, magnesium bromide, magnesium iodide, bis (hexamethyldisilazide) magnesium, bis (trifluoromethanesulfonylimide) magnesium and Grignard reagent or a combination thereof; reacting the mixture at a temperature of 25-200°C to generate the magnesium-containing electrolyte salt in the mixture to obtain the electrolyte.

11. The method for preparing the magnesium battery electrolyte according to claim 10, characterized in that, The reacting of the mixture at a temperature of 25-200°C to generate the magnesium-containing electrolyte salt in the mixture to obtain the electrolyte is performed for 3-48 h.

12. The method of claim 10, wherein the magnesium battery electrolyte is prepared by the steps of: a) dissolving magnesium metal in a solvent; b) adding a salt to the solution; and c) adding a compound to the solution. The mixture is cooled in the step of reacting the mixture at a temperature of 25-200°C to generate the magnesium-containing electrolyte salt in the mixture to obtain the electrolyte, and the target temperature of the cooling is -30-25°C.

13. A magnesium battery comprising: The magnesium battery electrolyte according to any one of claims 1-7 or the magnesium battery electrolyte prepared by the method according to any one of claims 8-12.

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