Magnesium ion battery electrolyte, preparation method thereof and magnesium ion battery

Abstract

The invention belongs to the technical field of magnesium ion batteries, and particularly relates to a magnesium ion battery electrolyte, a preparation method thereof and a magnesium ion battery. The invention provides a magnesium ion battery electrolyte. The magnesium ion battery electrolyte comprises a magnesium salt electrolyte, an amine organic solvent and an imidazole organic solvent. According to the magnesium ion electrolyte, the imidazole and amine organic solvents are used as the mixed cosolvent of the magnesium ion electrolyte, so that the electrolyte magnesium salt can be effectively dissolved, and the problems of decomposition and passivation of the electrolyte solvent and corrosion of a magnesium metal negative electrode can be effectively solved; the amine and imidazole co-soluble magnesium ion electrolyte provided by the invention can realize reversible deposition and dissolution of a magnesium metal negative electrode under the condition of a wide temperature range of-30 to 80 DEG C, and can be applied to a rechargeable magnesium battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnesium ion batteries, and particularly relates to a magnesium ion battery electrolyte, a preparation method thereof and a magnesium ion battery. BACKGROUND

[0002] The development of rechargeable batteries is the key to solving the problem of renewable energy storage. Metal magnesium is abundant in reserves, low in cost, environmentally friendly, and stable in physical and chemical properties, and has a very high theoretical volume specific capacity (3833 mAh / cm 3 The magnesium battery system with metal magnesium as the negative electrode material has the advantages of high energy density, low cost, high safety, etc., and is one of the new energy storage systems with great development prospects. However, due to the high charge density of magnesium ions, the strong electrostatic interaction leads to limited solubility of many magnesium salts and blocked ion transport, which greatly limits the ionic conductivity of the electrolyte. On the other hand, due to the low reduction potential of magnesium (-2.37 V vs. SHE), most organic solvents will react with the magnesium salt of the electrolyte and generate a passivation layer on the surface of the magnesium metal, which cannot effectively conduct magnesium ions, hindering the operation of the rechargeable magnesium battery.

[0003] Compared with lithium ion batteries, the development of magnesium batteries is still in its infancy, and a series of technical challenges and scientific problems limit the practical application of rechargeable magnesium batteries, which seriously hinders the further development of practical rechargeable magnesium batteries: (1) Corrosion problem of electrolyte. Most of the current magnesium battery electrolytes usually need to introduce chlorides (such as magnesium chloride, aluminum chloride, lithium chloride, etc.) to change the active material of the electrolyte and the electrode-electrolyte interface composition to realize the reversible deposition-dissolution of the magnesium metal negative electrode. However, Cl - will usually corrode many non-noble metal battery components, such as stainless steel battery cases, aluminum or copper current collectors, etc. (2) Referring to the traditional lithium ion battery electrolyte, the traditional magnesium ion electrolyte prepared using commercially available non-corrosive electrolyte salts can effectively solve the corrosion problem of Cl - . Due to the small ionic radius of Mg 2+ , it has a very high charge density (about 120 C / mm 3), which means that there is a strong electrostatic interaction between the cation and anion of many commercially available traditional magnesium salts, resulting in limited dissociation of them in ether solvents compatible with magnesium negative electrodes. Moreover, such electrolytes without chloride also have the problem of passivating the electrode-electrolyte interface, resulting in poor cycle performance. The common method at present is to introduce amine solvents or amine and ether solvents to enhance the dissociation of the above electrolyte salt, but the new problems of decomposition passivation of amine solvents and corrosion of magnesium metal negative electrode also appear. In addition, the existing electrolyte also generally has the problems of limited working temperature, impurity sensitivity, low coulomb efficiency, large overpotential, and non-uniform magnesium metal negative electrode deposition-dissolution, which limit the practical process of magnesium secondary batteries.

[0004] Based on the above analysis, the current magnesium ion battery electrolyte mainly has the following problems: (1) poor solubility of ether solvents, limited working temperature, easy passivation of magnesium metal negative electrode, etc.; (2) easy reduction and decomposition of amine solvents and corrosion of magnesium negative electrode interface, etc.; (3) the existing magnesium ion electrolyte has the problems of strong corrosion, low coulomb efficiency, large overpotential, non-uniform deposition-dissolution, poor stability, and short cycle life of magnesium ion battery, etc. SUMMARY

[0005] The purpose of the present application is to provide a magnesium ion battery electrolyte and a preparation method thereof, and a magnesium ion battery. The electrolyte provided by the present application can effectively solve the problems of electrolyte solvent decomposition passivation and magnesium metal negative electrode corrosion, and realize reversible deposition and dissolution of the magnesium metal negative electrode in a wide temperature range of-30 to 80℃.

[0006] In order to achieve the above purpose, the present application provides the following technical solutions:

[0007] The present application provides a magnesium ion battery electrolyte, which comprises a magnesium salt electrolyte, an amine organic solvent, and an imidazole organic solvent.

[0008] Preferably, the magnesium salt electrolyte comprises at least one of magnesium perchlorate, magnesium triflate, magnesium bis(trifluoromethanesulfonylimide), magnesium bis(hexamethyldisilazide), and magnesium bis(diisopropylamino).

[0009] Preferably, the amine organic solvent comprises at least one of 2-methoxyethylamine, 3-methoxypropylamine, 3-dimethylaminopropylamine, 1-(3-bromophenyl)-N,N-dimethylmethanamine, isobutylamine, dimethylacetamide, dimethylamine, 3-ethoxypropylamine, and 3-isopropoxypropylamine.

[0010] Preferably, the imidazole organic solvent comprises at least one of 1-methylimidazole, 1-ethylimidazole, 1-propylimidazole, 1-isopropylimidazole, 1-tert-butylimidazole, 1-allylimidazole, and 1-trimethylsilylimidazole.

[0011] Preferably, the concentration of the magnesium salt electrolyte in the magnesium ion battery electrolyte is 0.01-1.5 mol / L.

[0012] Preferably, the volume ratio of the amine organic solvent and the imidazole organic solvent is 1:0.1-10.

[0013] The application also provides a preparation method of the magnesium ion battery electrolyte, comprising the following steps:

[0014] Mixing the magnesium salt electrolyte, the amine organic solvent and the imidazole organic solvent to obtain the magnesium ion battery electrolyte.

[0015] Preferably, the mixing is performed in a protective atmosphere; the total content of oxygen and water in the protective atmosphere is less than 0.5 ppm; the protective atmosphere comprises argon.

[0016] The mixing is performed at a temperature of 0-100 DEG C for 6-72 h under stirring.

[0017] The application also provides a magnesium ion battery comprising the magnesium ion battery electrolyte or the magnesium ion battery electrolyte prepared by the preparation method.

[0018] Preferably, the negative electrode of the magnesium ion battery is magnesium metal, and the positive electrode is hexamolybdenum octasulfide.

[0019] The application provides a magnesium ion battery electrolyte comprising a magnesium salt electrolyte, an amine organic solvent and an imidazole organic solvent.

[0020] The magnesium ion battery electrolyte provided by the application can realize reversible deposition and dissolution of the magnesium metal negative electrode in a wide temperature range of-30-80 DEG C and can be applied to rechargeable magnesium batteries.

[0021] (1) Non-corrosive: In order to solve the decomposition passivation and magnesium metal negative electrode corrosion problems caused by the above-mentioned chloride and amine solvents for commercial magnesium salt, the present application introduces imidazole organic solvent. This amine and imidazole co-soluble magnesium ion electrolyte directly avoids the above defects of chloride and pure amine solvent. The imidazole organic solvent has stronger electronegativity than the amine solvent, which makes the amine and imidazole co-soluble magnesium ion electrolyte have a unique solvation structure. Due to the stronger coordination ability of imidazole, it enters the first solvation shell and expels part of the amine solvent, which reduces the possibility of decomposition of the amine solvent. Moreover, due to the stronger adsorption of imidazole organic solvent than amine organic solvent, it preferentially adsorbs on the electrode-electrolyte interface to form a planar interface barrier to isolate the amine solvent from direct contact with the magnesium negative electrode.

[0022] (2) Ultra-low overpotential and high coulombic efficiency: The chlorine-free and ether-free electrolyte system provided by the present application solves the poor cycle performance problem of electrolyte in pure ether or pure amine solvent. Even under the condition of larger current density, the overpotential of the electrolyte system in the Mg / / Mg symmetric battery is only about 50mV, and the average coulombic efficiency in the Mg / / Cu battery is as high as 99% or more.

[0023] (3) Wide temperature range and water-oxygen resistance: Compared with traditional ether solvents such as tetrahydrofuran (66℃), the boiling point of ethyleneglycol dimethyl ether (DME) is only about 85℃, and the boiling point of amine organic solvents such as 3-methoxypropylamine (MOPA) is about 118℃, and the boiling point of imidazole organic solvents such as 1-propylimidazole (PrIm) is as high as about 221℃. These characteristics make the amine and imidazole co-soluble magnesium ion electrolyte have higher thermal stability. Moreover, the -NH2 group of amine solvent can form hydrogen bond with water molecule, which makes the electrolyte containing amine solvent also has certain water resistance.

[0024] (4) Finally, due to the improvement of electrolyte corrosion and decomposition passivation of magnesium metal negative electrode, the magnesium metal negative electrode can be reversibly deposited-dissolved in the non-corrosive and commercially available traditional magnesium salt composed of magnesium ion electrolyte. The amine and imidazole co-soluble magnesium ion electrolyte can be applied to rechargeable magnesium batteries. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The deposition-dissolution rate performance of Mg / / Mg symmetric battery in Mg(TFSI)2-MOPA+PrIm electrolyte (Example 1);

[0026] Figure 2 The coulombic efficiency diagram of Mg / / Cu half-cell in Mg(TFSI)2-MOPA+PrIm electrolyte (Example 1);

[0027] Figure 3Cycling performance plot for Mg / / Mo6S8 battery in Mg(TFSI)2-MOPA + PrIm electrolyte (Example 1);

[0028] Figure 4 Charge-discharge curve for Mg / / Mo6S8 battery in Mg(TFSI)2-MOPA + PrIm electrolyte (Example 1);

[0029] Figure 5 Deposition-Stripping high temperature performance for Mg / / Cu half-cell in Mg(TFSI)2-MOPA + PrIm electrolyte (Example 1);

[0030] Figure 6 Deposition-Stripping low temperature performance for Mg / / Mg symmetric cell in Mg(TFSI)2-MOPA + PrIm electrolyte (Example 1);

[0031] Figure 7 Deposition-Stripping curve for Mg / / Mg symmetric cell in Mg(TFSI)2-MOPA + PrIm electrolyte with 30000 ppm water added (Example 1);

[0032] Figure 8 Coulombic efficiency plot for Mg / / Cu half-cell in Mg(TFSI)2-MOPA + PrIm electrolyte (Example 2);

[0033] Figure 9 Coulombic efficiency plot for Mg / / Cu half-cell in Mg(TFSI)2-iPOPA + PrIm electrolyte (Example 3);

[0034] Figure 10 Scanning electron microscope (SEM) of magnesium metal anode after deposition- stripping in Mg(TFSI)2-MOPA electrolyte (Comparative Example 1);

[0035] Figure 11 Scanning electron microscope (SEM) of magnesium metal anode after deposition- stripping in Mg(TFSI)2-MOPA + PrIm electrolyte (Example 1);

[0036] Figure 12 Scanning electron microscope (SEM) of fresh magnesium sheet after 72 hours of immersion in Mg(TFSI)2-MOPA electrolyte (Comparative Example 1);

[0037] Figure 13 Scanning electron microscope (SEM) of fresh magnesium sheet after 72 hours of immersion in Mg(TFSI)2-MOPA + PrIm electrolyte (Example 1);

[0038] Figure 14 Deposition-Stripping curve for Mg / / Mg symmetric cell in Mg(TFSI)2-MOPA electrolyte (Comparative Example 1);

[0039] Figure 15 Deposition-Stripping curve for Mg / / Mg symmetric cell in Mg(TFSI)2-MOPA+iPrIm electrolyte (Example 1);

[0040] Figure 16 Coulombic efficiency plot for Mg / / Cu half-cell in Mg(TFSI)2-MOPA+iPrIm electrolyte (Example 4);

[0041] Figure 17 Deposition-Stripping curve for Mg / / Mg symmetric cell in Mg(OTf)2-MOPA+EtIm electrolyte (Example 5). DETAILED DESCRIPTION

[0042] The present application provides a magnesium ion battery electrolyte, comprising a magnesium salt electrolyte, an amine organic solvent and an imidazole organic solvent.

[0043] In the present application, the magnesium salt electrolyte preferably comprises at least one of magnesium perchlorate (Mg(ClO4)2), magnesium triflate (Mg(OTf)2), magnesium bis(trifluoromethanesulfonylimide) (Mg(TFSI)2), magnesium bis(hexamethyldisilazide) (Mg(HMDS)2) and magnesium bis(diisopropylamide) (Mg[N(C3H7)]2).

[0044] In the present application, the amine organic solvent preferably comprises at least one of 2-methoxyethylamine (MOEA), 3-methoxypropylamine (MOPA), 3-dimethylaminopropylamine (DMAPA), 1-(3-bromophenyl)-N,N-dimethylmethanamine (BPDMA), isobutylamine (IBA), dimethylacetamide (DMAC), dimethylamine (DMA), 3-ethoxypropylamine (EOPA) and 3-isopropoxypropylamine (iPOPA).

[0045] In the present application, the imidazole organic solvent preferably comprises at least one of 1-methylimidazole (MeIm), 1-ethylimidazole (EtIm), 1-propylimidazole (PrIm), 1-isopropylimidazole (iPrIm), 1-tert-butylimidazole (tBuIm), 1-allylimidazole (AlIm) and 1-trimethylsilylimidazole (TSIm).

[0046] In the present application, the concentration of the magnesium salt electrolyte in the magnesium ion battery electrolyte is preferably 0.01-1.5 mol / L, and can be specifically 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 1.0 mol / L, or 1.5 mol / L.

[0047] In the present application, the volume ratio of the amine organic solvent and the imidazole organic solvent is preferably 1:0.1-10, and can be specifically 1:0.1, 1:0.5, 1:1, 1:5, or 1:10.

[0048] The present application also provides a preparation method of the magnesium ion battery electrolyte described in the above technical solution, which comprises the following steps:

[0049] The magnesium salt electrolyte, the amine organic solvent, and the imidazole organic solvent are mixed to obtain the magnesium ion battery electrolyte.

[0050] In the present application, the mixing is preferably carried out in a protective atmosphere; the total content of oxygen and water in the protective atmosphere is preferably less than 0.5 ppm; the protective atmosphere preferably comprises argon; the temperature of the mixing is preferably 0-100℃, and can be specifically 0℃, 10℃, 20℃, 30℃, 40℃, 46℃, 50℃, 60℃, 70℃, 80℃, 90℃, or 100℃; the time is preferably 6-72 h, and can be specifically 6 h, 12 h, 24 h, 36 h, 48 h, 60 h, or 72 h; and the mixing is preferably carried out under stirring.

[0051] The present application also provides a magnesium ion battery comprising the magnesium ion battery electrolyte described in the above technical solution or the magnesium ion battery electrolyte prepared by the preparation method described in the above technical solution.

[0052] In the present application, the negative electrode of the magnesium ion battery is preferably metallic magnesium, and the positive electrode is preferably hexamolybdenum octasulfide (Mo6S8). In the present application, the diameter of the negative electrode is preferably 12 mm, and the diameter of the positive electrode is preferably 10 mm. In the present application, the addition amount of the magnesium ion battery electrolyte is preferably 30-150 μL.

[0053] In the present application, the assembly process of the magnesium ion battery is preferably as follows: magnesium sheets and Mo6S8 are cut into the required diameter, and the oxide layer on the surface of the magnesium sheet is polished with sandpaper; Mo6S8 is first placed in the positive electrode side of the battery bottom shell, then a layer of glass fiber diaphragm is laid on the Mo6S8 to completely cover the positive electrode, the magnesium ion battery electrolyte is added dropwise with a pipette gun to ensure that the diaphragm is fully wetted, the polished magnesium sheet is placed as the negative electrode above the diaphragm, a stainless steel gasket and a spring are usually added above the negative electrode to ensure good electrical contact, and finally the cap is buckled on the battery bottom shell, and the battery is sealed by using a button cell packaging machine.

[0054] In the present application, the sandpaper preferably has a mesh number of 1500-2000 meshes. In the present application, the glass fiber separator preferably comprises GFB, GFD or GFA.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety.

[0056] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0057] Embodiment 1

[0058] In this embodiment, the magnesium salt electrolyte is Mg(TFSI)2(concentration of 0.3 mol / L); 3-methoxypropylamine (MOPA) and 1-propylimidazole (PrIm) are selected as the amine organic solvent and the imidazole organic solvent of the electrolyte, respectively, wherein the volume ratio of MOPA and PrIm is 2:1;

[0059] Preparation method: in a glove box with the content of oxygen and water being less than 0.5 ppm and filled with argon, the magnesium salt electrolyte is placed in the amine organic solvent and the imidazole organic solvent, and stirred at 46°C for 24 h to obtain the magnesium ion battery electrolyte;

[0060] In this embodiment, MOPA can well dissociate Mg(TFSI)2, but it also has the problems of decomposition passivation and corrosion of the magnesium metal negative electrode, which will also lead to poor magnesium deposition-dissolution reversibility and easy short circuit. The magnesium ion electrolyte co-dissolved with MOPA and PrIm has a unique solvation structure, and the PrIm with stronger electronegativity and adsorption can reduce the coordination of the MOPA solvent and can be preferentially adsorbed on the magnesium metal surface to improve the problems of decomposition passivation of the amine organic solvent and corrosion of the magnesium metal negative electrode, thereby effectively solving the short circuit and electrolyte decomposition passivation problems of the existing pure amine solvent and conventional ether solvent, and realizing highly reversible magnesium deposition-dissolution.

[0061] Embodiment 2

[0062] The electrolyte is prepared in the manner of embodiment 1, wherein the volume ratio of MOPA and PrIm is adjusted from 2:1 to 1:1.

[0063] Embodiment 3

[0064] The electrolyte is prepared in the manner of embodiment 1, wherein the amine organic solvent MOPA is replaced by 3-isopropoxypropylamine (iPOPA).

[0065] Example 4

[0066] An electrolyte was obtained in the same manner as in Example 1, wherein the imidazole co-solvent PrIm was replaced by 1-isopropylimidazole (iPrIm).

[0067] Example 5

[0068] An electrolyte was obtained in the same manner as in Example 1, wherein the magnesium salt electrolyte Mg(TFSI)2was replaced by Mg(OTf)2, and the imidazole co-solvent was replaced by 1- ethylimidazole (EtIm).

[0069] Comparative Example 1

[0070] An electrolyte was obtained in the same manner as in Example 1, wherein PrIm was omitted, i.e. MOPA was used as the sole solvent.

[0071] Performance Test

[0072] Test Example 1

[0073] The electrolyte obtained in Example 1 was subjected to a performance test;

[0074] Test (1): The electrolyte obtained in Example 1 was assembled into a Mg / / Mg symmetric cell in the following manner: the magnesium sheet was cut to the required diameter (12 mm) and the surface of the magnesium sheet was polished with sandpaper (typically 1500-2000 mesh) to remove the oxide layer. The polished magnesium sheet was first placed in the positive electrode side of the cell bottom shell, then a layer of glass fiber separator (GFB) was laid on the magnesium sheet to completely cover the positive electrode, an appropriate amount of electrolyte was added dropwise (150 μL) using a pipette to ensure that the separator was fully wetted, the polished negative electrode side magnesium sheet was placed on top of the separator, a stainless steel washer and spring were usually added on top of the negative electrode to ensure good electrical contact, and finally the cap was screwed onto the cell bottom shell and then sealed using a button cell packaging machine;

[0075] The Mg / / Mg symmetric cell obtained above exhibited excellent rate performance, Figure 1 The deposition-dissolution rate performance of the Mg / / Mg symmetric cell in the Mg(TFSI)2-MOPA+PrIm electrolyte, Figure 1 showing that it can be reversibly cycled at a current density of 1-12 mA / cm 2 .

[0076] Benefiting from the regulation of the amine and imidazole co-solvent on the electrode-electrolyte interface, Figure 15 The deposition-dissolution curve of the Mg / / Mg symmetric cell in the Mg(TFSI)2-MOPA+PrIm electrolyte, as Figure 15As shown, the Mg / / Mg symmetric cell assembled with Mg(TFSI)2-MOPA + PrIm electrolyte can work stably at 1.0 mA / cm 2 ; 1.0 mAh / cm 2 for 500 hours under the condition.

[0077] Test (2): The electrolyte obtained in Example 1 was assembled into a Mg / / Cu half-cell, and the assembly process was as follows: the magnesium sheet (diameter 12 mm) and the Cu foil were cut to the required diameter (diameter 16 mm), and the oxide layer on the surface of the magnesium sheet was polished with sandpaper (generally 1500-2000 mesh). First, the Cu foil was placed in the cell bottom shell on the positive side, then a layer of glass fiber separator (GFB) was laid on the Cu foil to completely cover the positive electrode, an appropriate amount of electrolyte (150 μL) was added dropwise with a pipette to ensure that the separator was fully wetted, the polished magnesium sheet was placed as the negative electrode above the separator, and a stainless steel gasket and a spring were usually added above the negative electrode to ensure good electrical contact, and finally the cap was buckled on the cell bottom shell, and then a button cell packaging machine was used for compression sealing;

[0078] The above obtained half-cell was subjected to electrochemical cycle test, Figure 2 The coulombic efficiency diagram of the Mg / / Cu half-cell in Mg(TFSI)2-MOPA + PrIm electrolyte is shown in Figure 2 , even at a current density of 10.0 mA / cm 2 , the battery can still have an ultra-high cycle performance of 1000 times, and the average coulombic efficiency is as high as 99.12%.

[0079] Test (3): In view of the solvent structure and negative electrode interface regulation effect of the amine and imidazole cosolvent on the Mg(TFSI)2-based magnesium ion electrolyte, a Mg / / Mo6S8 full cell was assembled to verify its application in magnesium secondary batteries.

[0080] The assembly process was as follows: the magnesium sheet (diameter 12 mm) and Mo6S8 were cut to the required diameter (diameter 10 mm), and the oxide layer on the surface of the magnesium sheet was polished with sandpaper (generally 1500-2000 mesh). First, the Mo6S8 was placed in the cell bottom shell on the positive side, then a layer of glass fiber separator (GFB) was laid on the Mo6S8 to completely cover the positive electrode, an appropriate amount of electrolyte (150 μL) was added dropwise with a pipette to ensure that the separator was fully wetted, the polished magnesium sheet was placed as the negative electrode above the separator, and a stainless steel gasket and a spring were usually added above the negative electrode to ensure good electrical contact, and finally the cap was buckled on the cell bottom shell, and then a button cell packaging machine was used for compression sealing;

[0081] Figure 3 The cycle performance diagram of the Mg / / Mo6S8 battery is Figure 4is the charge and discharge curve of Mg / / Mo6S8 battery;

[0082] like Figure 3 and 4 As shown, the Mg(TFSI)2-MOPA+PrIm electrolyte can be stably reversibly cycled 2000 times at a rate of 2C, and the mass specific capacity has remained stable at around 56mAh / g. This capacity retention rate and ultra-long life demonstrate the potential application of amine and imidazole co-dissolved magnesium ion electrolytes in rechargeable magnesium batteries.

[0083] Test (4): Since the magnesium ion electrolyte co-dissolved with amine and imidazole has a wide temperature range and water and oxygen resistance, the electrochemical cycling performance test was carried out at -30 to 80 ° C and under the condition of adding 30000 ppm of water to the Mg(TFSI)2-MOPA+PrIm electrolyte; the Mg / / Mg symmetrical cell in test (1) or the Mg / / Cu half-cell in test (2) was used as the test sample;

[0084] Figure 5 The deposition-dissolution high-temperature performance of the Mg / / Cu half-cell in Mg(TFSI)2-MOPA+PrIm electrolyte is shown in Figure 2. Figure 5 As shown in the figure, even at a high temperature of 80 °C, the Mg(TFSI)2-MOPA+PrIm electrolyte can still be activated at 4.0 mA / cm 2 ; 0.5mAh / cm 2 Under the conditions of deposition and dissolution for 240 times, the average coulombic efficiency is still 96.61%;

[0085] Figure 6 The deposition-dissolution low-temperature performance of Mg / / Mg symmetric cells in Mg(TFSI)2-MOPA+PrIm electrolyte is shown in Figure 2. Figure 6 As shown in the figure, at a temperature of -30 ° C, the Mg / / Mg symmetric battery assembled with this electrolyte can also achieve a high current density of 1.0 mA / cm 2 ;0.25mAh / cm 2 Continuously work for 200 hours under the conditions of

[0086] Figure 7 The deposition-dissolution curve of the Mg / / Mg symmetric cell in the Mg(TFSI)2-MOPA+PrIm electrolyte with 30000ppm water added is shown in Figure 2. Figure 7 As shown, even after adding 30000ppm water to the Mg(TFSI)2-MOPA+PrIm electrolyte, the Mg / / Mg symmetric cell can still operate at 2.0mA / cm 2 ; 0.5mAh / cm 2reversible deposition and dissolution under the conditions of 5.0 mA / cm

[0087] Test Example 2

[0088] The electrolyte obtained in Example 2 was tested for performance;

[0089] The Mg / / Cu half-cell was assembled according to the test (2) in Test Example 1 above;

[0090] The cycle performance curve of the Mg / / Cu half-cell obtained above is shown in Figure 8 It can be seen that the electrolyte can work continuously for 3000 times under the conditions of 5.0 mA / cm 2 ; 0.5 mAh / cm 2 , and has an ultra-high coulomb efficiency of 99.73%.

[0091] Test Example 3

[0092] The electrolyte obtained in Example 3 was tested for performance;

[0093] The Mg / / Cu half-cell was assembled according to the test (2) in Test Example 1 above;

[0094] The cycle performance curve of the Mg / / Cu half-cell obtained above is shown in Figure 9 It can be seen that the electrolyte can stably and reversibly cycle more than 600 times under the conditions of 3.0 mA / cm 2 ; 0.5 mAh / cm 2 , with an average coulomb efficiency of about 98.44%.

[0095] Test Example 4

[0096] The electrolyte obtained in Comparative Example 1 was tested for performance;

[0097] Figure 10 The scanning electron microscope of the magnesium metal negative electrode after deposition-dissolution in the Mg(TFSI)2-MOPA electrolyte (Comparative Example 1) is shown in Figure 10 It can be seen from the electron scanning microscope (SEM) characterization that in the pure amine electrolyte, the magnesium metal negative electrode surface after cycling in the Mg(TFSI)2-MOPA electrolyte has a morphology similar to magnesium dendrite, and the deposition morphology is not uniform and dense. These protruding deposition morphologies may be the reason why the Mg(TFSI)2-MOPA electrolyte short-circuits and fails after only 10 hours of cycling under the conditions of a current density of 1.0 mA / cm 2 Figure 14 ​The deposition-dissolution curve of Mg / / Mg symmetric cell in Mg(TFSI)2-MOPA electrolyte (comparative example 1); while for the electrolyte obtained from example 1, Figure 11 The scanning electron microscope (SEM) photo of the magnesium metal anode after deposition-dissolution in Mg(TFSI)2-MOPA+PrIm electrolyte (example 1) by Figure 11 It can be seen from the electron scanning photo that the surface of the magnesium metal anode after deposition in Mg(TFSI)2-MOPA+PrIm electrolyte is relatively flat and dense, which shows that the amine and imidazole co-soluble magnesium ion electrolyte can well solve the decomposition passivation and magnesium metal anode corrosion problems of pure amine solvent.

[0098] Figure 12 The scanning electron microscope (SEM) photo of the fresh magnesium sheet after soaking in Mg(TFSI)2-MOPA electrolyte (comparative example 1) for 72 hours, Figure 13 The scanning electron microscope (SEM) photo of the fresh magnesium sheet after soaking in Mg(TFSI)2-MOPA+PrIm electrolyte (example 1) for 72 hours;

[0099] As shown in Figure 12 It can be seen from the electron scanning microscope characterization that the surface of the fresh magnesium sheet after polishing has many corrosion pits after soaking in Mg(TFSI)2-MOPA electrolyte for 72 hours. These all show that the strong corrosiveness of pure amine solvent can cause irreversible magnesium metal anode deposition-dissolution. Figure 13 The surface morphology of the fresh magnesium sheet after sandpaper polishing after soaking in Mg(TFSI)2-MOPA+PrIm electrolyte (example 1) for 72 hours is shown. The magnesium sheet after soaking has no obvious corrosion pits except the obvious polishing marks on the surface.

[0100] Table 1 and Table 2 are the atomic content ratios of the relevant elements of the fresh magnesium sheet after soaking in the electrolyte of example 1 and comparative example 1;

[0101] Table 1 Test results of fresh magnesium sheet after soaking in electrolyte of example 1

[0102] Map

[0103]

[0104] Table 2 Test results of fresh magnesium sheet after soaking in electrolyte of comparative example 1

[0105] Map

[0106]

[0107] From Table 1 and Table 2, it can be seen that after the electrolyte obtained from Example 1 is soaked, the content of C, N, O, F, S elements accounts for a higher proportion than that after soaking in Mg(TFSI)2-MOPA electrolyte (Comparative Example 1), and these elements indicate that imidazole cosolvent and TFSI - Anions all have stronger adsorption capacity than MOPA, and preferentially adsorb on the surface of magnesium metal, which can effectively prevent the corrosion of amine solvents, which shows that amine and imidazole cosolvent can solve the corrosion problem of pure amine solvent.

[0108] Test Example 5

[0109] The electrolyte obtained in Example 4 was tested for performance;

[0110] The Mg / / Cu half-cell was assembled according to the test (2) in the above Test Example 1;

[0111] The cycle performance curve of the above obtained Mg / / Cu half-cell is shown in Figure 16 It can be seen that with copper foil as the working electrode, the Mg(TFSI)2-MOPA+iPrIm electrolyte can still work stably under the condition of 3.0 mA / cm 2 ; 0.5 mAh / cm 2 , and has a high average coulombic efficiency of 99.48% after more than 900 cycles.

[0112] Test Example 6

[0113] The electrolyte obtained in Example 5 was tested for performance;

[0114] The Mg / / Mg symmetric cell was assembled according to the test (1) in the above Test Example 1;

[0115] The deposition-dissolution curve of the above obtained Mg / / Mg symmetric cell is shown in Figure 17 It can be seen that the Mg(OTf)2-MOPA+EtIm electrolyte obtained can work continuously in the Mg / / Mg symmetric cell at a current density of 6.0 mA / cm 2 for more than 180 hours after several small current density activations.

[0116] Although the above examples have made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained according to the present embodiments without creativity, which are within the protection scope of the present application.

Claims

1. A magnesium-ion battery electrolyte, characterized in that, The magnesium salt electrolyte, the amine organic solvent and the imidazole organic solvent.

2. The magnesium-ion battery electrolyte of claim 1, wherein, The magnesium salt electrolyte comprises at least one of magnesium perchlorate, magnesium triflate, magnesium bis(trifluoromethanesulfonylimide), magnesium bis(hexamethyldisilazide) and magnesium bis(diisopropylamide).

3. The magnesium-ion battery electrolyte of claim 1, wherein, The amine organic solvent comprises at least one of 2-methoxyethylamine, 3-methoxypropylamine, 3-dimethylaminopropylamine, 1-(3-bromophenyl)-N,N-dimethylmethanamine, isobutylamine, dimethylacetamide, dimethylamine, 3-ethoxypropylamine and 3-isopropoxypropylamine.

4. The magnesium-ion battery electrolyte of claim 1, wherein, The imidazole organic solvent comprises at least one of 1-methylimidazole, 1-ethylimidazole, 1-propylimidazole, 1-isopropylimidazole, 1-tert-butylimidazole, 1-allylimidazole and 1-trimethylsilylimidazole.

5. The magnesium-ion battery electrolyte according to claim 1 or 2, wherein, The concentration of the magnesium salt electrolyte in the magnesium ion battery electrolyte is 0.01-1.5 mol / L.

6. The magnesium-ion battery electrolyte of claim 1, 3, or 4, wherein, The volume ratio of the amine organic solvent to the imidazole organic solvent is 1:0.1-10.

7. Process for the preparation of the electrolyte for magnesium-ion batteries according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: Mixing the magnesium salt electrolyte, the amine organic solvent and the imidazole organic solvent to obtain the magnesium ion battery electrolyte.

8. The preparation method according to claim 7, characterized in that The mixing is performed in a protective atmosphere; the total content of oxygen and water in the protective atmosphere is less than 0.5 ppm; and the protective atmosphere comprises argon. The mixing is performed at a temperature of 0-100 ℃ for 6-72 h under stirring.

9. A magnesium-ion battery, characterized by, The magnesium ion battery electrolyte is prepared by the method of any one of claims 1-6 or 7 or 8.

10. The magnesium-ion battery of claim 9, wherein, The negative electrode of the magnesium ion battery is metal magnesium, and the positive electrode is hexamolybdenum octasulfide.

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