Electrolyte for magnesium ion battery, preparation method thereof and magnesium ion battery

Abstract

The application discloses an electrolyte for a magnesium ion battery, a preparation method of the electrolyte and the magnesium ion battery. The electrolyte comprises a non-aqueous solvent, including one or more of an ionic liquid and an organic solvent; an electrolyte salt; and an imidazole additive having a structure of formula (1); wherein R1 and R2 are respectively selected from any one of hydrogen and C1-C7 alkyl, and R1 is connected with a carbon atom at any one position represented by C1, C2 and C3 in the formula (1). The imidazole additive in the application is combined with the non-aqueous solvent, can promote effective dissociation of cations in the electrolyte salt, improve ion conductivity, improve kinetic performance of a secondary battery containing the electrolyte, inhibit passivation of anions in the electrolyte on a negative electrode material, promote reversible deposition-dissolution of magnesium, and further improve energy density of the secondary battery containing the electrolyte, and improve charge-discharge specific capacity and cycle stability of the magnesium ion battery.

Description

Technical Field

[0001] This application belongs to the field of magnesium-ion battery technology, specifically relating to an electrolyte for magnesium-ion batteries, a method for preparing the electrolyte, and a magnesium-ion battery. Background Technology

[0002] The development of secondary batteries is considered key to solving the problem of renewable energy storage. Using magnesium ions as the active ions in secondary batteries offers significant advantages: magnesium is abundant, inexpensive, environmentally friendly, has relatively stable physicochemical properties, and is less prone to dendrite growth, resulting in a very high theoretical volumetric capacity (3833 mA·h / cm³). 3 Magnesium-ion battery systems, which use metallic magnesium or magnesium alloys as negative electrode materials, 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-ion batteries. Summary of the Invention

[0004] In view of this, this application aims to provide an electrolyte for magnesium-ion batteries that can improve the reversible deposition-dissolution properties of magnesium, and also provides a method for preparing the electrolyte and a magnesium-ion battery containing the electrolyte.

[0005] In a first aspect, embodiments of this application provide an electrolyte for magnesium-ion batteries, comprising:

[0006] Non-aqueous solvents, including one or more of ionic liquids and organic solvents;

[0007] Electrolyte salts; and

[0008] Imidazole additives have the structure of formula (1);

[0009]

[0010] R1 and R2 are selected from hydrogen and alkyl groups of C1-C7 respectively, and R1 is connected to a carbon atom at any position represented by C1, C2, or C3 in formula (1).

[0011] According to an embodiment of one aspect of this application, the imidazole additive includes one or more of 1-methylimidazole, 2-methylimidazole, 4-methylimidazole, ethylimidazole, propylimidazole, butylimidazole, pentylimidazole, hexylimidazole, and heptylimidazole.

[0012] According to one embodiment of this application, the molar ratio of imidazole additive to non-aqueous solvent is 1:(0.05 to 15.0).

[0013] According to one embodiment of this application, the molar concentration of the imidazole additive in the electrolyte is 0.1 to 10 mol / L.

[0014] According to one aspect of the present application, the ionic liquid includes one or more of imidazole ionic liquids, piperidine ionic liquids, or pyrrole ionic liquids.

[0015] According to an embodiment of one aspect of this application, imidazole ionic liquids include one or more of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonic acid)imine salt, 1-ethyl-3-methylimidazolium hexafluorophosphate, and 1-methyl-3-methylimidazolium bromide.

[0016] According to an embodiment of one aspect of this application, pyrrole-based ionic liquids include one or more of N-butyl-N-methylpyrrolidinyl bis(trifluoromethanesulfonyl)imide, N-alkylN-methylpyrrolidinyl bromotetrafluoroborate, and N-alkylN-methylpyrrolidinyl hexafluorophosphate.

[0017] According to an embodiment of one aspect of this application, the piperidine ionic liquid is selected from one or more of N-butyl-N-methylpiperidine bis(trifluoromethanesulfonyl)imide, N-octylpyridine bromide, and N-hexylpyridine bromide.

[0018] According to one embodiment of this application, the organic solvent includes one or more of ether compounds, pyridine compounds, sulfone compounds, amine compounds, nitrile compounds, and cyclic carbonate compounds.

[0019] According to an embodiment of one aspect of this application, the ether compound includes one or more of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dioxane, and polyethylene glycol dimethyl ether.

[0020] According to an embodiment of one aspect of this application, the amine compound includes one or more of dimethylamine, 1-methoxy-2-propylamine, 2-methoxyethylamine, and methoxyamine.

[0021] According to an embodiment of one aspect of this application, pyridine compounds include one or more of pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2,6-dichloropyridine, and 2-aminopyridine.

[0022] According to an embodiment of one aspect of this application, the sulfone compound includes one or more of dimethyl sulfone, sulfolane, dipropyl sulfone, phenethyl sulfone, and diethyl sulfone.

[0023] According to an embodiment of one aspect of this application, the nitrile compound includes one or more of acetonitrile, trichloroacetonitrile, and 3-cyanopyridine.

[0024] According to an embodiment of one aspect of this application, the cyclic carbonate compound or carboxylic acid ester compound includes one or more of ethylene carbonate, propylene carbonate, butyl carbonate, 1,2-dimethylethylene carbonate, methyl formate, ethyl formate, methyl acetate, ethyl propionate, methyl butyrate, and ethyl butyrate.

[0025] According to one embodiment of this application, the chemical formula of the electrolyte salt includes R. 1 a MgR 2 2, where R 1 Including one or more of C2H5, C3H7, and R 2 It includes one or more of organic and inorganic anions; 0 ≤ a ≤ 1.

[0026] According to an embodiment of one aspect of this application, the electrolyte salt includes one or more of [C2H5MgCl][TFSI], [C2H5MgCl][TFSI]·THF, [C3H7MgCl][TFSI], [C3H7MgCl][TFSI]·DME, Mg(ClO4)2, Mg(OTf)2, Mg(TFSI)2, Mg(HMDS)2, Mg[N(C3H7)]2, and Mg(BH4)2.

[0027] According to one embodiment of this application, the electrolyte comprises an electrolyte salt of 0.01-3.0 mol / L.

[0028] According to one embodiment of this application, the non-aqueous solvent is tetrahydrofuran and dimethyl ether, and the electrolyte salt is Mg(HMDS)2.

[0029] According to one embodiment of this application, the non-aqueous solvent is dimethyl ether, and the electrolyte salt is Mg(TFSI)2.

[0030] Secondly, embodiments of this application provide a magnesium-ion battery, comprising: an electrolyte for a magnesium-ion battery according to the first aspect.

[0031] According to one embodiment of this application, a magnesium-ion battery includes a negative electrode material, which includes magnesium metal or a magnesium alloy.

[0032] According to one embodiment of this application, a magnesium-ion battery includes a positive electrode material, which includes one or more of transition metal oxides, transition metal sulfides, polyanionic phosphate materials, and silicate materials.

[0033] Compared with the prior art, this application has at least the following beneficial effects:

[0034] According to the electrolyte of this application embodiment, the imidazole additives, in combination with non-aqueous solvents, can promote the effective dissociation of cations in the electrolyte salt, regulate the solvation structure of the electrolyte, thereby improving ionic conductivity and enhancing the kinetic performance of the secondary battery containing the electrolyte; suppressing the passivation of the negative electrode material by anions in the electrolyte, stripping magnesium salts from the negative electrode surface to avoid the formation of a passivation layer, promoting reversible deposition-dissolution of magnesium, and further improving the energy density of the secondary battery containing the electrolyte, as well as the charge-discharge specific capacity and cycle stability of the magnesium-ion battery. Attached Figure Description

[0035] 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.

[0036] Figure 1a The Mg-O in the Mg(TFSI)2-DME electrolyte of Comparative Example 1 of this application is shown. TFSI - Radial distribution function and coordination number;

[0037] Figure 1b The Mg-O in the Mg(TFSI)2-DME+MeIm electrolyte of Example 1 of this application is shown. TFSI - Radial distribution function and coordination number;

[0038] Figure 1c The Mg-N in the Mg(TFSI)2-DME+MeIm electrolyte of Example 1 of this application is shown. MeIm Radial distribution function and coordination number;

[0039] Figure 2 The Mg(TFSI)2-DME and Mg(TFSI)2-DME+MeIm electrolytes in Comparative Example 1 and Example 1 of this application are shown respectively. 25 Mg NMR spectrum;

[0040] Figure 3Raman spectra of Mg(TFSI)2-DME and Mg(TFSI)2-DME+MeIm electrolytes in Comparative Example 1 and Example 1 of this application are shown respectively;

[0041] Figure 4a The image shows a scanning electron microscope (SEM) image and energy dispersive spectroscopy (EDS) plot of the magnesium metal anode of this application after deposition and dissolution in comparative example 1Mg(TFSI)2-DME electrolyte;

[0042] Figure 4b The image shows a scanning electron microscope (SEM) image and energy dispersive spectroscopy (EDS) plot of the magnesium metal anode of this application after deposition and dissolution in the Mg(TFSI)2-DME+MeIm electrolyte of Example 1.

[0043] Figure 5a The X-ray photoelectron spectroscopy (XPS) spectrum of the F1s of the magnesium metal anode of this application after deposition and dissolution in the Mg(TFSI)2-DME electrolyte of Comparative Example 1 is shown.

[0044] Figure 5b The X-ray photoelectron spectroscopy (XPS) spectrum of the F1s of the magnesium metal anode of this application after deposition and dissolution in the Mg(TFSI)2-DME+MeIm electrolyte of Example 1 is shown.

[0045] Figure 6 The cyclic voltammetry (CV) curves of Mg(TFSI)2-DME and Mg(TFSI)2-DME+MeIm electrolytes in Comparative Example 1 and Example 1 of this application are shown in comparison.

[0046] Figure 7a The deposition-dissolution curves of the Mg / / Mg symmetric cell of Comparative Example 1 in Mg(TFSI)2-DME electrolyte are shown.

[0047] Figure 7b The following is a deposition-dissolution curve of the Mg / / Mg symmetric cell in Mg(TFSI)2-DME+MeIm electrolyte of Example 1 of this application;

[0048] Figure 8a The following is a comparison of the charge-discharge curves of the Mg / / Mo6S8 full cell of this application in the Mg(TFSI)2-DME electrolyte of Comparative Example 1 and the Mg(TFSI)2-DME+MeIm electrolyte of Example 1.

[0049] Figure 8bThe graph shows a comparison of the cycling performance of the Mg / / Mo6S8 full cell of this application in the Mg(TFSI)2-DME electrolyte of Comparative Example 1 and the Mg(TFSI)2-DME+MeIm electrolyte of Example 1.

[0050] Figure 9a The Mg-N2 content in the Mg(HMDS)2-THF electrolytes of Comparative Example 2 and Example 5 of this application are shown respectively. HMDS Radial distribution function and coordination number;

[0051] Figure 9b The Mg-N in the Mg(HMDS)2-THF+MeIm electrolyte of Example 5 of this application is shown. HMDS Radial distribution function and coordination number;

[0052] Figure 9c The Mg-N in the Mg(HMDS)2-THF+MeIm electrolyte of Example 5 of this application is shown. MeIm Radial distribution function and coordination number;

[0053] Figure 10a The deposition-dissolution rate performance of the Mg / / Mg symmetric cell of this application in the Mg(HMDS)2-THF electrolyte of Comparative Example 2 is shown.

[0054] Figure 10b The deposition-dissolution rate performance of the Mg / / Mg symmetric cell of this application in the Mg(HMDS)2-THF+MeIm electrolyte of Example 5 is shown;

[0055] Figure 10c The deposition-dissolution curves of the Mg / / Mg symmetric cell of this application in the Mg(HMDS)2-THF+MeIm electrolyte of Example 5 are shown. Detailed Implementation

[0056] 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.

[0057] 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.

[0058] In the description of this application, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, and "several" in "one or more" means two or more.

[0059] 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.

[0060] Magnesium-ion batteries include positive electrode materials, negative electrode materials, and electrolytes. Negative electrode materials include metallic magnesium and magnesium alloys. In related technologies, the electrolyte includes magnesium-containing electrolyte salts, and the presence of Mg in the electrolyte... 2+ Magnesium ions have small ionic radii and high charge density (approximately 120 C / mm²). Strong electrostatic interactions exist between the cations and anions in magnesium-containing electrolytes, leading to increased Mg content in the electrolyte. 2+ The degree of dissociation on the magnesium anode side is limited.

[0061] On the one hand, the low degree of dissociation of electrolyte salts limits the effective number of active ions transported by the electrolyte, resulting in low ionic conductivity in magnesium-ion batteries. Studies have found that even at low concentrations of 0.1 mol / L in conventional electrolytes, Mg(ClO4)2 / DME and Mg(OTf)2 / DME electrolytes still contain a large amount of solid electrolyte salts, with ionic conductivity as low as 0.061 mS / cm and 0.019 mS / cm, respectively. Even more concerning, 0.1 mol / L Mg(HMDS)2 / DME electrolyte, although a clear liquid, has an ionic conductivity of only 0.006 mS / cm. On the other hand, the strong interaction between cations and anions results in more contact ion pairs or aggregates in the electrolyte. These anions participate in the solvation structure of magnesium ions, making it easier for the electrolyte to decompose on the surface of the magnesium metal anode, forming an anion-derived interface. Since magnesium ions typically face a large diffusion barrier at the electrode-electrolyte interface, the interface acts as a passivation layer. The two main reasons mentioned above have led to the widespread irreversible magnesium deposition-dissolution behavior in many traditional magnesium ion electrolytes, which limits the practical application of magnesium secondary batteries.

[0062] The limited solvation capability in magnesium-ion batteries results in low effective dissociation of traditional magnesium salt electrolytes, which prevents efficient and rapid magnesium ion migration and diffusion, thus reducing the kinetic performance of magnesium-ion batteries.

[0063] The current common solution is to pre-apply interface protection to the magnesium anode surface to prevent the continuous decomposition of the electrolyte. However, this does not fundamentally solve the passivation problem of the magnesium anode. Furthermore, the additional interface protection layer cannot provide capacity to the battery and limits the dissolution of metallic magnesium, which further reduces the magnesium ion content and affects the energy density of the battery.

[0064] Based on this, the inventors conducted extensive research to provide an electrolyte for magnesium-ion batteries that increases the concentration of active ions in the electrolyte, thereby improving the ionic conductivity of the electrolyte and thus improving the kinetic performance of the magnesium-ion battery; and strips magnesium salts from the negative electrode surface to avoid the formation of a passivation layer, promoting the reversible deposition-dissolution of magnesium, thereby improving the energy density of the magnesium-ion battery.

[0065] Electrolyte for magnesium-ion batteries

[0066] In a first aspect, embodiments of this application provide an electrolyte for magnesium-ion batteries, comprising:

[0067] Non-aqueous solvents, including one or more of ionic liquids and organic solvents;

[0068] Electrolyte salts; and

[0069]

[0070] R1 and R2 are selected from hydrogen and alkyl groups of C1-C7 respectively, and R1 is connected to a carbon atom at any position represented by C1, C2, or C3 in formula (1).

[0071] According to embodiments of this application, the synergistic effect of imidazole additives and non-aqueous solvents can promote the effective dissociation of cations in the electrolyte salt, regulate the solvation structure of the electrolyte, thereby improving ionic conductivity and enhancing the kinetic performance of the secondary battery containing the electrolyte; it also inhibits the passivation of the negative electrode material by anions in the electrolyte, removes magnesium salts from the negative electrode surface to avoid the formation of a passivation layer, promotes reversible deposition-dissolution of magnesium, and further improves the energy density of the secondary battery containing the electrolyte, thereby enhancing the charge-discharge specific capacity and cycle stability of the magnesium-ion battery. 。

[0072] Imidazole additives, represented by methylimidazole (MeIm), are highly polar solvents with a donor number of 47 and a dielectric constant of 39, which are higher than those of dimethyl glycol ether (DME), which has a donor number of 19 and a dielectric constant of 7.5. Therefore, methylimidazole (MeIm) has a stronger ability to solubilize magnesium ions.

[0073] The relevant mechanism includes: In related technologies, there is a strong interaction between cations and anions in the electrolyte, resulting in numerous contact ion pairs or aggregates. Compared to free anions, these strongly interacting anions participate in solvation structures or aggregate structures, making it easier for the electrolyte to decompose on the magnesium metal negative electrode surface to form an anion-derived interface. In this application, by adding an appropriate amount of imidazole additives to the electrolyte, it is found that these additives possess strong coordination capabilities, effectively solvating magnesium ions, promoting the generation of more free anions, weakening the electrostatic interaction between magnesium ions and anions, mitigating the continuous side reactions between anions and the magnesium metal negative electrode, reducing the migration barrier of magnesium ions on the negative electrode surface, and thus improving the reversibility of the magnesium metal negative electrode in traditional magnesium ion electrolytes.

[0074] The relevant mechanism of solvation structure: The solvation process can be divided into three independent steps: the dissolution and solvation process of the electrolyte salt in the organic solvent (step I). This step has a significant impact on the electrolyte conductivity. Secondly, the migration process of the active cations in the electrolyte salt in the organic solvent (step II), which also affects the electrolyte conductivity. The third step is the desolvation process of the active cations at the electrolyte-electrode interface (step III), which greatly influences the ion insertion or deposition behavior. All three steps are driven by the interactions between cations, solvent molecules, and anions. For example, in step I, the interaction between anions and cations in the electrolyte salt determines the lattice energy of the salt, while the interaction between cations and solvent molecules determines the solvation energy. Therefore, on the one hand, weakly coordinated anionic sodium salts are developed to improve solubility. On the other hand, solvents with a high donor number can also improve the solubility of the salt. In step II, the migration rate of the active cation is also affected by the interactions between cations and anions, as well as between solvents. Strong coordination between cations and anions inhibits the transport of solvated sodium ions. Similarly, strong interactions between solvent molecules (such as hydrogen bonding) lead to increased viscosity, which in turn inhibits ion mobility. However, steps I and II only affect the electrolyte conductivity, resulting in a decrease in the rate performance of sodium-ion batteries. Step III, however, is a more complex process involving desolvation, the decomposition of solvent and anions on the surface, crossing energy barriers, and passing through interfacial films. The aforementioned solvation structures or processes significantly affect battery capacity, rate performance, voltage window, coulombic efficiency, and cycle stability.

[0075] Studies have shown that introducing imidazole additives, such as methylimidazolium (MeIm), as co-solvents into the non-aqueous solvent of the electrolyte can promote the effective separation of electrolyte salts, improve the ionic conductivity of the electrolyte, and improve the reversible deposition-dissolution of magnesium metal anodes in secondary batteries.

[0076] In addition, adding imidazole additives to the electrolyte helps to suppress the side reactions between some anions in the electrolyte salt and magnesium metal in the secondary battery, thereby improving the electrochemical performance of the secondary battery.

[0077] In some optional embodiments of this application, the imidazole additives include one or more of 1-methylimidazole, 2-methylimidazole, 4-methylimidazole, ethylimidazole, propylimidazole, butylimidazole, pentylimidazole, hexylimidazole, and heptylimidazole.

[0078] In some optional embodiments of this application, the molar ratio of the imidazole additive to the non-aqueous solvent is 1:(0.05–15.0). Optionally, the molar ratio of the imidazole additive to the non-aqueous solvent can be any value or range thereof from 1:0.05, 1:0.1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, and 1:15. The molar concentration of the imidazole additive in the electrolyte is 0.1–10 mol / L.

[0079] The molar concentrations of imidazole additives in the electrolyte can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 4.0 mol / L, 4.5 mol / L, 5.0 mol / L, 5.5 mol / L, 6.0 mol / L, 6.5 mol / L,

[0080] Any value or range of the concentrations of 7.0 mol / L, 7.5 mol / L, 8.0 mol / L, 9.0 mol / L, and 10 mol / L. According to embodiments of this application, when the molar concentration of the imidazole additive in the electrolyte or the molar ratio of the imidazole additive to the non-aqueous solvent is within the above range, it is beneficial to further promote the dissociation and solvation of the electrolyte salt, to increase the concentration of active cations, to increase ionic conductivity, and thereby improve the kinetic performance of the secondary battery containing this electrolyte.

[0081] In some optional embodiments of this application, the ionic liquid includes one or more of imidazole ionic liquids, piperidine ionic liquids, or pyrrole ionic liquids.

[0082] In some optional embodiments of this application, the imidazole ionic liquid includes one or more of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonic acid)imine salt, 1-ethyl-3-methylimidazolium hexafluorophosphate, and 1-methyl-3-methylimidazolium bromide.

[0083] In some optional embodiments of this application, the pyrrole ionic liquid includes one or more of N-butyl-N-methylpyrrolidinyl bis(trifluoromethanesulfonyl)imide, N-alkylN-methylpyrrolidinyl bromotetrafluoroborate, and N-alkylN-methylpyrrolidinyl hexafluorophosphate.

[0084] In some optional embodiments of this application, the piperidine ionic liquid is selected from one or more of N-butyl-N-methylpiperidine bis(trifluoromethanesulfonyl)imine salt, N-octylpyridine bromide salt, and N-hexylpyridine bromide salt.

[0085] In some optional embodiments of this application, the organic solvent includes one or more of ether compounds, pyridine compounds, sulfone compounds, amine compounds, nitrile compounds, and cyclic carbonate compounds;

[0086] In some optional embodiments of this application, the ether compounds include one or more of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dioxane, and polyethylene glycol dimethyl ether.

[0087] In some optional embodiments of this application, the amine compound includes one or more of dimethylamine, 1-methoxy-2-propylamine, 2-methoxyethylamine, and methoxyamine.

[0088] In some optional embodiments of this application, the pyridine compounds include one or more of pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2,6-dichloropyridine, and 2-aminopyridine.

[0089] In some optional embodiments of this application, the sulfone compounds include one or more of dimethyl sulfone, sulfolane, dipropyl sulfone, phenethyl sulfone, and diethyl sulfone.

[0090] In some optional embodiments of this application, the nitrile compound includes one or more of acetonitrile, trichloroacetonitrile, and 3-cyanopyridine.

[0091] In some optional embodiments of this application, the cyclic carbonate or carboxylic acid ester compound includes one or more of ethylene carbonate, propylene carbonate, butyl carbonate, 1,2-dimethylethylene carbonate, methyl formate, ethyl formate, methyl acetate, ethyl propionate, ethyl propionate, methyl butyrate, and ethyl butyrate.

[0092] In some optional embodiments of this application, the chemical formula of the electrolyte salt includes R. 1 a MgR 2 2, where R 1 Including one or more of C2H5, C3H7, and R 2 It includes one or more of organic and inorganic anions; 0 ≤ a ≤ 1.

[0093] In some optional embodiments of this application, the electrolyte salt includes one or more of [C2H5MgCl][TFSI], [C2H5MgCl][TFSI]·THF, [C3H7MgCl][TFSI], [C3H7MgCl][TFSI]·DME, Mg(ClO4)2, Mg(OTf)2, Mg(TFSI)2, Mg(HMDS)2, Mg[N(C3H7)]2, and Mg(BH4)2.

[0094] As an example, Mg(TFSI)₂ is an electrolyte salt with good thermal stability, high oxidative stability, and good solubility. Even low-concentration Mg(TFSI)₂ electrolytes exhibit significant anion-cation interactions. 2+ -TFSI - ] + Ions compared to TFSI alone - Magnesium deposition and dissolution are more likely to occur on the magnesium anode surface, forming a passivation interface that is not conducive to magnesium ion conduction. This ultimately leads to problems in secondary batteries containing this electrolyte, such as high magnesium deposition-dissolution overpotential (>2.0V), poor reversibility, and easy short circuits. Adding imidazole additives to the Mg(TFSI)2-DME electrolyte, through the high donor number and high dielectric constant of the imidazole additives, regulates the solvation structure of the electrolyte and promotes the solubilization of TFSI. - Anions and Mg 2+ The separation of cations effectively inhibits TFSI. - Side reactions between the magnesium metal anode and the anode.

[0095] In some optional embodiments of this application, the electrolyte comprises an electrolyte salt at a concentration of 0.01-3.0 mol / L. Optionally, the concentration of the electrolyte salt can be selected from any value or range thereof from 0.01 mol / L, 0.04 mol / L, 0.06 mol / L, 0.08 mol / L, 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.5 mol / L, 2.0 mol / L, and 3.0 mol / L. Controlling the concentration of the electrolyte salt in the electrolyte, under the action of imidazole additives, facilitates the dissociation of cations in the electrolyte salt, increases the concentration of cations (such as magnesium ions) in the electrolyte, improves ionic conductivity, and thereby improves the kinetic performance of the secondary battery containing this electrolyte.

[0096] In some embodiments, the electrolyte salt includes a magnesium-containing electrolyte salt with a high degree of dissociation in the electrolyte, and the viscosity of the magnesium-ion battery electrolyte is moderate. The viscosity of the electrolyte can be 0.2-50 Pa·s, or any value or range thereof from 0.2 Pa·s, 0.4 Pa·s, 1 Pa·s, 5 Pa·s, 10 Pa·s, 20 Pa·s, 40 Pa·s, and 50 Pa·s. Within the above viscosity range, it is advantageous for magnesium... 2+ The transmission of [mathematical components]. According to embodiments of this application, the components contained in the magnesium-ion battery electrolyte are within the above-mentioned range, making the viscosity of the magnesium-ion battery electrolyte moderate, which can further improve the [magnesium-ion battery electrolyte]... 2+ This facilitates the transport of ions and improves ionic conductivity.

[0097] In some optional embodiments of this application, the non-aqueous solvent is tetrahydrofuran and dimethyl ether, and the electrolyte salt is Mg(HMDS)2.

[0098] In some optional embodiments of this application, the non-aqueous solvent is dimethyl ether and the electrolyte salt is Mg(TFSI)2.

[0099] According to the embodiments of this application, the above combination can effectively achieve the dissociation of magnesium ions, strip the magnesium negative electrode passivation layer to optimize the reversible deposition-dissolution of magnesium and reduce the overpotential, while giving the electrolyte excellent water resistance, with very significant effects.

[0100] [Preparation method of electrolyte for magnesium-ion batteries]

[0101] In some optional embodiments of this application, a method for preparing an electrolyte for a magnesium-ion battery includes: mixing an imidazole additive, a non-aqueous solvent, and an electrolyte salt to obtain an electrolyte, wherein the non-aqueous solvent includes one or more of ionic liquids and organic solvents.

[0102] In some optional embodiments of this application, a method for preparing an electrolyte for a magnesium-ion battery includes: mixing an imidazole additive, a non-aqueous solvent, and an electrolyte salt under heating conditions to obtain an electrolyte, wherein the non-aqueous solvent includes one or more of ionic liquids and organic solvents.

[0103] In some embodiments, the mixture is cooled after mixing, with a target cooling temperature of 0–25°C.

[0104] In some embodiments, the above substances are mixed at a temperature of 25°C to 200°C to obtain an electrolyte; optionally, the reaction time is 3-48 hours; optionally, after mixing, the mixture is cooled to a target temperature of -30°C to 25°C.

[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, and optionally cooled, to obtain an electrolyte.

[0106] According to embodiments of this application, during the preparation of magnesium-ion 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] According to the embodiments of this application, the above preparation method is simple, and the prepared magnesium-ion battery electrolyte has good miscibility, stable system, and strong water resistance, thereby improving the battery performance of magnesium-ion batteries.

[0109] Magnesium-ion batteries

[0110] Secondly, embodiments of this application provide a magnesium-ion battery, comprising: the electrolyte for a magnesium-ion battery as described in the first aspect. According to the magnesium-ion battery of this application, the electrolyte includes imidazole additives that are substituted or substituted with C1-C7 alkyl groups. This helps to suppress the passivation of the negative electrode material by anions in the electrolyte, prevents the formation of a passivation layer by stripping magnesium salts from the negative electrode surface, promotes reversible deposition-dissolution of magnesium, and thereby improves the energy density of the secondary battery containing this electrolyte. 。

[0111] In some optional embodiments of this application, the electrolyte comprises magnesium ions at a concentration of (0.05)-(1.2) mol / L. A magnesium ion concentration within this range is beneficial for improving the ionic conductivity of the magnesium-ion battery and enhancing its kinetic performance, such as charge / discharge performance and rate capability. If the concentration of the magnesium electrolyte salt is below 0.05 mol / L, the ionic conductivity is low, resulting in greater ohmic polarization of the magnesium-ion battery; while when the electrolyte salt concentration is above 1.2 mol / L, the electrolyte viscosity increases, leading to increased concentration polarization and hindering ion mass transfer and diffusion.

[0112] In some optional embodiments of this application, the magnesium-ion battery includes a negative electrode material, which includes magnesium metal or a magnesium alloy.

[0113] In some embodiments, the anode and cathode materials are typically metallic magnesium or magnesium alloys. Metallic magnesium has a low redox potential and a high specific capacity (up to 2205 mA·h / g), enabling the formation of high-capacity batteries; however, a dense oxide film easily forms on the surface of metallic magnesium. Magnesium-based alloys, due to their lower reactivity than metallic magnesium, avoid the formation of a passivation film on the surface of active magnesium, thus improving the electrochemical behavior of magnesium-ion batteries.

[0114] In some embodiments, the negative electrode material further includes a negative electrode active material and a binder.

[0115] In some optional embodiments of this application, the magnesium-ion battery includes a positive electrode material, which may further include a positive electrode active material, including one or more of transition metal oxides, transition metal sulfides, polyanionic phosphate materials, and silicate materials.

[0116] In some embodiments, the positive electrode active material may include, but is not limited to, one or more of transition metal sulfides, transition metal oxides, transition metal borides, and polyanionic phosphates. As an example, the transition metal sulfides may include TiS2, MoS2, WS2, VS2, HfS2, ZrS2, NbS3, VS4, and Mg. a One or more of Mo3S4 (0 < a < 2), Mo6S8, CuS, and Cu2S. As an example, the transition metal oxide may include V2O5 and V6O. 13 One or more of MnO2, Mn2O3, MoO3, and WO3. As an example, the transition metal borides may include one or more of TiB2, MoB2, and ZrB2.

[0117] The main metal oxides include V2O5 and V6O 13 Materials such as MnO2 and Mn2O3 have high operating voltage and high capacitance, but poor reversibility of magnesium ion insertion / extraction. Transition metal sulfides mainly include TiS2, MoS2, WS2, VS2, HfS2, ZrS2, NbS3, VS4, and Mg. a Materials such as Mo3S4 (0 < a < 2), Mo6S8, CuS, and Cu2 exhibit high reversibility of magnesium ion insertion / extraction, but have low operating voltages. x M y SiO4 (M = Fe, Mn, Co, Ni, x + y = 2) is a type of polyanionic material that utilizes SiO4 2- The large-space and stable three-dimensional framework structure generated by M-O-Si completes the Mg 2+ The reversible insertion / extraction of metals allows for a discharge specific capacity of up to 300 mA·h / g. Transition metal composites mainly include spinel-structured compounds, NaSICON-structured compounds, and olivine-structured compounds, which possess relatively high electronic and ionic conductivity. Magnesium-transition metal composite cathode materials with high redox potentials can be used to improve the battery's operating voltage.

[0118] In some embodiments, the positive electrode material includes 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.

[0119] In some embodiments, the positive electrode material may further include a conductive agent and a binder. This application does not specifically limit the materials of the conductive agent and binder; conventional materials can be used.

[0120] 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.

[0121] The magnesium-ion battery of this application embodiment 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.

[0122] Example

[0123] 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.

[0124] Example 1

[0125] Preparation of magnesium-ion battery electrolyte: Mg(TFSI)₂, dimethyl ether (DME), and 1-methylimidazole (MeIm) were mixed in a glove box filled with argon gas, where the oxygen and water content was below 1 ppm. The concentration of Mg(TFSI)₂ in the electrolyte was 0.4 mol / L, and the volume ratio of DME to 1-methylimidazole was 2:1. The concentration of 1-methylimidazole in the electrolyte was 3.6 mol / L.

[0126] In a glove box filled with argon gas and containing less than 0.5 ppm of oxygen and water, a commercially available conventional magnesium salt electrolyte (MgR2) was dissolved at the desired concentration (0.01–1.5 mol / L) in a mixed solvent (volume ratio 1:0.1–10) of organic solvent (Q) and 1-methylimidazole (MeIm). The mixture was stirred at 0–150 °C for 6–72 h to obtain a magnesium ion electrolyte.

[0127] 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.

[0128] Preparation of the positive electrode: Mo6S8 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.

[0129] Preparation of the separator: A 7 μm thick porous polyethylene (PE) film was used as the separator.

[0130] Preparation of magnesium-ion batteries: The CuS positive electrode, electrolyte, separator, and magnesium sheet negative electrode are assembled in sequence to complete the preparation of magnesium-ion batteries.

[0131] Example 2

[0132] The difference between this embodiment and Example 1 is that the concentration of 1-methylimidazole in the electrolyte is 2.4 mol / L.

[0133] Example 3

[0134] The difference between this embodiment and Example 1 is that 1-methylimidazole is replaced with propylimidazole, and the concentration of propylimidazole is 4.5 mol / L.

[0135] Example 4

[0136] The difference between this embodiment and Example 1 is that Mg(TFSI)2 is replaced with Mg(HMDS)2, and its concentration is 0.3 mol / L.

[0137] Example 5

[0138] The difference between this embodiment and Example 1 is that half the volume of tetrahydrofuran (THF) in the dimethyl ether (DME) electrolyte is added to obtain the Mg(HMDS)2-THF+MeIm electrolyte.

[0139] Comparative Example 1

[0140] The difference between this comparative example and Example 1 is that 1-methylimidazole is not added, resulting in a magnesium-ion battery electrolyte.

[0141] Comparative Example 2

[0142] The difference between this comparative example and Comparative Example 1 is that Mg(TFSI)2 in Comparative Example 1 is replaced with Mg(HMDS)2, and half the volume of DME is replaced with tetrahydrofuran (THF).

[0143] Test section

[0144] 1) Ionic conductivity detection

[0145] The solvation structures of the electrolytes in Example 1 and Comparative Example 1 were simulated using molecular dynamics. Figure 1a As shown, Figure 1a The graph shows two vertical axes, left and right, with arrows indicating the vertical coordinates of the curves. Solid arrows indicate the left vertical axis (radial distribution function) corresponding to the black solid line; dashed arrows indicate the right vertical axis (coordination number) corresponding to the gray dashed line.

[0146] The dashed line mainly represents the plateau region (the value corresponding to the plateau is the coordination number). As shown in Figure 1, the coordination number corresponding to the plateau of the dashed line is approximately 5.4. Theoretical simulation results show that in the electrolyte of Comparative Example 1, Mg(TFSI)₂-DME exhibits a strong cation-anion interaction peak at 0.212 nm. 2+ and TFSI - The O atom in the anion exhibits a significant electrostatic interaction, namely Mg-O. TFSI - Interactions. When MeIm solvent is introduced, Mg-O TFSI - Electrostatic interactions were significantly weakened, with the coordination number decreasing from 5.4 to 1.6. Figure 1b In addition, a Mg-N atom located at 0.22 nm MeIm The interactions are clearly visible, with a coordination number as high as 4.3. Figure 1c The significant differences mentioned above indicate that the MeIm co-solvent, in conjunction with TFSI... - It won the coordination competition and effectively participated in the Mg 2+ The first solvation shell promotes the efficient dissociation of the Mg(TFSI)2 electrolyte salt. Therefore, Example 1 will have a higher ionic conductivity than Comparative Example 1.

[0147] The ionic conductivity meter test results show that the ionic conductivity (8.31 mS / cm) of the Mg(TFSI)2-DME+MeIm electrolyte according to Example 1 is more than twice that of the ionic conductivity (4.01 mS / cm) of the Mg(TFSI)2-DME electrolyte according to Comparative Example 1.

[0148] 2) Nuclear magnetic resonance spectroscopy and Raman spectroscopy detection

[0149] The electrolytes in Example 1 and Comparative Example 1 were tested, further confirming the solvation regulation ability of methylimidazole (MeIm). Figure 2 As shown, Comparative Example 1 contains Mg(TFSI)2-DME electrolyte. 25 The chemical shift peak of Mg is located at -2.8 ppm; in the Mg(TFSI)2-DME+MeIm electrolyte of Example 1, Mg 2+ The chemical shift (8.8 ppm) shifted by 11.6 ppm, due to: more Mg 2+ -MeIm solvent coordination and less Mg 2+-TFSI - Interaction. Raman spectra located at 740–745 cm⁻¹ -1 The nearby characteristic peaks correspond to TFSI - The vibrational peak of the anion, and the Raman peak corresponding to the electrolyte regulated by methylimidazole (MeIm) shift to lower wavenumbers. Figure 3 This also indicates that the Mg(TFSI)2-DME+MeIm electrolyte in Example 1 contains more free TFSI. - Anions.

[0150] 3) Detection of magnesium anode in secondary batteries

[0151] The magnesium anode after cycling with the Mg(TFSI)2-DME electrolyte in Comparative Example 1 was observed using a scanning electron microscope. Figure 4a As shown, numerous cracks exist on the magnesium metal surface. EDS results reveal that, in addition to the Mg element signal peak, the magnesium anode surface also contains significant signals of decomposition products derived from anions such as C, N, O, F, and S. Figure 4b The magnesium anode using the Mg(TFSI)2-DME+MeIm electrolyte in Example 1 was uniform and dense. Elemental analysis showed that the anode surface was dominated by Mg signals, while the impurity signals corresponding to the electrolyte decomposition products were weak. X-ray photoelectron spectroscopy (XPS) showed a strong MgF2 signal after cycling in the Mg(TFSI)2-DME electrolyte. Figure 5a In the Mg(TFSI)2-DME+MeIm electrolyte, the F element signal intensity is very weak. Figure 5b Due to TFSI - Anions are the only F source in the electrolyte, so it can be considered that the traditional Mg(TFSI)2 electrolyte regulated by MeIm effectively inhibits TFSI. - Passivation of magnesium metal anode.

[0152] Based on the detection methods 1)-3), the following conclusions can be drawn: Under the action of 1-methylimidazole (MeIm), due to its strong coordination ability, Mg... 2+ TFSI in solvation shell - The number of anions is significantly reduced, thereby alleviating the reduction and decomposition of the electrolyte on the magnesium anode surface and effectively inhibiting the formation of the passivation layer that hinders magnesium ion transport.

[0153] 4) Detection of polarization potential of deposited-dissolved metallic magnesium

[0154] A Mg / / PG battery was assembled using pyrolytic graphite (PG) as the working electrode, and cyclic voltammetry (CV) tests were performed. Figure 6As shown, the Mg(TFSI)2-DME electrolyte exhibits a low redox current density and a large deposition-dissolution overpotential. During dissolution, the oxidation peak is located at 1.56 V (vs. Mg / Mg). 2+ The deposition-dissolution current increased to 1.5 mA·cm⁻¹ when using Mg(TFSI)₂-DME+MeIm electrolyte. -2 The oxidation peak potential decreased to 0.46V. The potentials corresponding to the peak dissolution currents of the two electrolytes differed by 1.1V, reflecting a significant difference in the magnesium electroplating-stripping behavior of the electrolytes. In the original Mg(TFSI)2-DME electrolyte, Mg... 2+ -TFSI - Interaction-induced anionic reductive decomposition results in a very high deposition-dissolution overpotential (>1.0V) for the original electrolyte, such as... Figure 7a As shown, thanks to the effective dissociation of Mg(TFSI)₂ by MeIm, the deposition-dissolution overpotential of the magnesium metal anode in the Mg(TFSI)₂-DME+MeIm electrolyte is significantly reduced, reaching 0.1 mA·cm⁻¹. -2 It can operate continuously for 810 hours at current density with an overpotential below 0.3V. Figure 7b This indicates that the polarization potential is reduced under the influence of MeIm, suggesting that MeIm facilitates the effective dissociation of electrolyte salts.

[0155] 5) Measurement of charge / discharge overpotential, specific capacity, and coulombic efficiency of magnesium-ion batteries.

[0156] The magnesium-ion batteries of Example 1 and Comparative Example 1 were subjected to constant current charge-discharge tests. The voltage range of the battery test was 0.15-2.0V, and the battery test rate was 0.1C. The results were as follows: Figure 8a and 8b As shown, the passivation of the magnesium anode in Comparative Example 1 could not achieve reversible deposition and dissolution of magnesium, resulting in a magnesium anode failure. The discharge capacity of the Mg(TFSI)2-DME electrolyte decreased drastically after several cycles, reaching only 10 mAh·g at the 15th cycle. -1 Subsequently, almost no capacity was released. In contrast, in the Mg(TFSI)2-DME+MeIm electrolyte of Example 1, the Mg / / Mo6S8 battery was able to operate stably for 100 cycles after several initial electrochemical activations, exhibiting a discharge specific capacity greater than 40 mAh·g. -1 The charge / discharge overpotential, specific capacity, and retention rate were significantly better than those of the original electrolyte, demonstrating that methylimidazole (MeIm) in magnesium ion electrolyte can regulate the charge / discharge overpotential, specific capacity, and coulombic efficiency of magnesium ion batteries.

[0157] 6) Testing of the solvation regulation capability of magnesium ion electrolyte

[0158] To further verify the solvation regulation ability of methylimidazolium (MeIm) cosolvent on traditional magnesium ion electrolytes, the Mg(HMDS)2-THF electrolyte in Comparative Example 2 was tested using an ionic conductivity meter. The ionic conductivity of the obtained Mg(HMDS)2-THF electrolyte was only 8.15 μS / cm.

[0159] The Mg(HMDS)2-THF electrolyte in Example 5 was tested and found that its ionic conductivity increased by more than 30 times (250.9 μS / cm), which confirmed the strong dissociation ability of MeIm.

[0160] Furthermore, the electrolytes of Comparative Example 2 and Example 5 were subjected to molecular dynamics simulation tests as described above. Figure 9a Molecular dynamics simulations show that the sharp Mg-N at 0.192 nm in the Mg(HMDS)2-THF electrolyte of Comparative Example 2... HMDS The coordination peaks indicate that the Mg(HMDS)2 electrolyte salt is not readily dissociated in THF. - The average coordination number of the anion was 1.25. After introducing MeIm into the electrolyte of Example 5, HMDS... - The coordination number of the anion decreased to 0.85. Figure 9b Furthermore, a new Mg-N group appeared at 0.212 nm. MeIm Interactions, with an average coordination number as high as 3.54 ( Figure 9c This demonstrates that in the electrolyte of Example 5, MeIm, with its strong coordination ability, can promote the effective dissociation of Mg(HMDS)2, thus significantly improving the ionic conductivity of the electrolyte.

[0161] The electrolytes of Comparative Example 2 and Example 5 were subjected to polarization potential detection of deposited-dissolved metallic magnesium as described above. Mg / / Mg symmetric cells were assembled, and the deposition-dissolution behavior of the Mg(HMDS)2-based conventional magnesium salt electrolyte was investigated. Figure 10a As shown, the comparative example 2Mg(HMDS)2-THF electrolyte can only achieve a current of 0.05 mA·cm⁻¹. -2 and 0.1 mA·cm -2 Deposition-dissolution occurs under low current density conditions, and the overpotential is large. When the current density increases to 0.2 mA·cm⁻¹, [the process continues]. -2 The battery experienced a short circuit due to the extremely low ionic conductivity of the original electrolyte. However, the Mg(HMDS)₂-THF+MeIm electrolyte in Example 5, under the strong coordination dissociation effect of MeIm, exhibited significantly improved ionic conductivity, thus enabling reversible deposition and dissolution of metallic magnesium. Figure 10b The Mg(HMDS)2-THF+MeIm electrolyte can operate at 0.05–2.0 mA·cm⁻¹. -2It operates stably within the current range, with an overpotential much lower than that of the original electrolyte. Using the Mg(HMDS)2-THF+MeIm electrolyte from Example 5, the magnesium anode can operate at 0.5 mA·cm⁻¹. -2 Achieving deposition-dissolution behavior exceeding 200 hours at current densities ( Figure 10c ).

[0162] By comparing Example 1 with Comparative Example 1 and Example 5 with Comparative Example 2, it can be seen that the imidazole additives and non-aqueous solvents in the electrolyte according to the embodiments of this application can promote the effective dissociation of cations in the electrolyte salt, adjust the solvation structure of the electrolyte, thereby improving the ionic conductivity and the kinetic performance of the secondary battery containing the electrolyte; suppress the passivation of the negative electrode material by anions in the electrolyte, remove magnesium salts from the negative electrode surface to avoid the formation of a passivation layer, promote the reversible deposition-dissolution of magnesium, and thus improve the energy density of the secondary battery containing the electrolyte, and improve the charge-discharge specific capacity and cycle stability of the magnesium-ion battery.

[0163] The above are merely specific embodiments 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. An electrolyte for a magnesium-ion battery, characterized in that, Include: Non-aqueous solvents, including one or more of ionic liquids and organic solvents; Electrolyte salts, including one or more of [C2H5MgCl][TFSI], [C2H5MgCl][TFSI]·THF, [C3H7MgCl][TFSI], [C3H7MgCl][TFSI]·DME, Mg(ClO4)2, Mg(OTf)2, Mg(TFSI)2, Mg(HMDS)2, Mg[N(C3H7)]2, and Mg(BH4)2; and imidazole additives having the structure of formula (1); （1） Wherein, R1 and R2 are selected from hydrogen and alkyl groups of C1-C7 respectively, and R1 is connected to a carbon atom at any position represented by C1, C2, or C3 in formula (1); The imidazole additive has a molar concentration of 2.4~4.5 mol / L in the electrolyte.

2. The electrolyte according to claim 1, characterized in that, Imidazole additives include one or more of 1-methylimidazole, 2-methylimidazole, 4-methylimidazole, ethylimidazole, propylimidazole, butylimidazole, pentylimidazole, hexylimidazole, and heptylimidazole.

3. The electrolyte according to claim 1, characterized in that, The molar ratio of the imidazole additive to the non-aqueous solvent is 1:(0.05~15.0).

4. The electrolyte according to any one of claims 1-3, characterized in that, The ionic liquid includes one or more of imidazole ionic liquids, piperidine ionic liquids, or pyrrole ionic liquids.

5. The electrolyte according to claim 4, characterized in that, The imidazole ionic liquids include one or more of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonic acid)imine salt, 1-ethyl-3-methylimidazolium hexafluorophosphate, and 1-methyl-3-methylimidazolium bromide.

6. The electrolyte according to claim 4, characterized in that, The pyrrole-based ionic liquids include one or more of N-butyl-N-methylpyrrolidinyl bis(trifluoromethanesulfonyl)imine, N-alkylN-methylpyrrolidinyl bromotetrafluoroborate, and N-alkylN-methylpyrrolidinyl hexafluorophosphate.

7. The electrolyte according to claim 4, characterized in that, The piperidine-based ionic liquid is selected from N-butyl-N-methylpiperidine bis(trifluoromethanesulfonyl)imine salt.

8. The electrolyte according to any one of claims 1-3, characterized in that, The organic solvent includes one or more of the following: ether compounds, pyridine compounds, sulfone compounds, amine compounds, nitrile compounds, and cyclic carbonate compounds.

9. The electrolyte according to claim 8, characterized in that, The ether compounds include one or more of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and dioxane.

10. The electrolyte according to claim 8, characterized in that, The amine compounds include one or more of dimethylamine, 1-methoxy-2-propylamine, and 2-methoxyethylamine.

11. The electrolyte according to claim 8, characterized in that, The pyridine compounds include one or more of pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2,6-dichloropyridine, and 2-aminopyridine.

12. The electrolyte according to claim 8, characterized in that, The sulfone compounds include one or more of dimethyl sulfone, sulfolane, dipropyl sulfone, phenethyl sulfone, and diethyl sulfone.

13. The electrolyte according to claim 8, characterized in that, The nitrile compounds include one or more of acetonitrile, trichloroacetonitrile, and 3-cyanopyridine.

14. The electrolyte according to claim 8, characterized in that, The cyclic carbonate compounds include one or more of ethylene carbonate, propylene carbonate, butyl carbonate, and 1,2-dimethylethylene carbonate.

15. The electrolyte according to claim 8, characterized in that, The organic solvent also includes carboxylic acid ester compounds, which include one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, and ethyl butyrate.

16. The electrolyte according to any one of claims 1-3, characterized in that, The electrolyte contains 0.01-3.0 mol / L of the electrolyte salt.

17. The electrolyte according to any one of claims 1-3, characterized in that, The non-aqueous solvent is tetrahydrofuran and dimethyl ether, and the electrolyte salt is Mg(HMDS)2; and / or, The non-aqueous solvent is dimethyl ether, and the electrolyte salt is Mg(TFSI)2.

18. A magnesium-ion battery, characterized in that, include: The electrolyte for magnesium-ion batteries according to any one of claims 1 to 17.

19. The magnesium-ion battery according to claim 18, characterized in that, The magnesium-ion battery includes a negative electrode material, which comprises magnesium metal or a magnesium alloy; and / or, The magnesium-ion battery includes a positive electrode material, which includes one or more of the following: transition metal oxides, transition metal sulfides, polyanionic phosphate materials, and silicate materials.

Images