Application of oxygen-containing cycloalkane, magnesium ion electrolyte and preparation method thereof

Abstract

The invention belongs to the technical field of magnesium ion batteries, and particularly relates to application of oxygen-containing cycloalkane, a magnesium ion electrolyte and a preparation method of the magnesium ion electrolyte. The invention provides an application of oxygen-containing cycloalkane in a magnesium ion electrolyte. The number of carbon atoms on a main chain of the oxygen-containing cycloalkane is not less than 3, and the number of oxygen atoms on the main chain is not less than 2. The oxygen-containing cycloalkane is used as the solvent of the magnesium ion electrolyte, the cycle life of the battery can be effectively prolonged, the coulombic efficiency of the battery can be effectively improved, and the magnesium ion electrolyte based on the oxygen-containing cycloalkane can be applied to a rechargeable magnesium battery.

Description

Technical Field

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

[0002] The development of rechargeable batteries is key to solving the problem of renewable energy storage. Magnesium is abundant, inexpensive, environmentally friendly, and has relatively stable physicochemical properties, possessing a high theoretical volumetric capacity (3833 mAh / cm³). 3 Magnesium batteries, using magnesium as the negative electrode material, possess advantages such as high energy density, low cost, and high safety, making them one of the most promising new energy storage systems. However, due to the high charge density of magnesium ions, strong electrostatic interactions limit the solubility of many magnesium salts and impede ion transport, significantly restricting the ionic conductivity of the electrolyte. Furthermore, due to magnesium's low reduction potential (-2.37V vs. SHE), most organic solvents and magnesium salts in the electrolyte undergo continuous interfacial side reactions with magnesium, ultimately forming a passivation layer on the magnesium surface that cannot effectively conduct magnesium ions, hindering the operation of rechargeable magnesium batteries.

[0003] Compared to lithium-ion batteries, the development of magnesium batteries is still in its infancy. A series of technical challenges and scientific problems limit the practical application of rechargeable magnesium batteries. Among them, the electrolyte used to transport magnesium ions continues to face numerous technical difficulties, seriously hindering the further development of practical rechargeable magnesium batteries. First, there's the issue of electrolyte corrosion. Currently, most magnesium battery electrolytes typically require the introduction of chlorides (such as magnesium chloride, aluminum chloride, lithium chloride, etc.) to alter the active materials and electrode-electrolyte interface composition in order to achieve reversible deposition-dissolution of the magnesium metal anode. However, chloride ions often corrode many non-precious metal battery components, such as stainless steel battery casings and aluminum or copper current collectors.

[0004] Secondly, the magnesium anode exhibits uneven deposition / dissolution in chloride-free (non-corrosive) electrolytes, resulting in low coulombic efficiency and short battery life. Currently, the most commonly used organic solvents in chloride-free magnesium ion electrolytes are tetrahydrofuran (THF) and dimethyl glycol ether (DME). Under the strong solvation effect of magnesium ions, these solvents readily undergo continuous reduction and decomposition on the magnesium metal anode surface, forming a discontinuous, uneven, and unfavorable passivation layer that hinders magnesium ion conduction. This leads to uneven magnesium deposition / solvent distribution and low coulombic efficiency (especially under electrolyte-poor test conditions), severely impacting the cycle life of magnesium metal batteries. Currently, rechargeable magnesium metal batteries generally use large amounts of electrolyte, but excessive electrolyte is detrimental to the practical application of magnesium batteries. Summary of the Invention

[0005] The purpose of this invention is to provide an application of oxygen-containing cycloalkanes, a magnesium ion electrolyte and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides an application of oxygen-containing cycloalkanes in magnesium ion electrolytes, wherein the main chain of the oxygen-containing cycloalkanes has no less than 3 carbon atoms and no less than 2 oxygen atoms.

[0007] Preferably, the oxygen-containing cycloalkanes include at least one of 1,3-dioxane, 1,4-dioxane, 1,3-dioxolane, 4-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, and 1,3,5-trioxane.

[0008] The present invention also provides a magnesium ion electrolyte, comprising a magnesium salt and a solvent; the solvent comprising an oxygen-containing cycloalkanes; The oxygen-containing cycloalkanes have at least 3 carbon atoms in their main chain and at least 2 oxygen atoms in their main chain.

[0009] Preferably, the solvent further includes an auxiliary solvent, which includes at least one of ether solvents, amine solvents, imidazole solvents, phosphate ester solvents, and ionic liquids.

[0010] Preferably, the ether solvent includes at least one of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; The amine solvents include at least one of 2-methoxyethylamine, 3-methoxypropylamine, 3-dimethylaminopropylamine, 1-(3-bromophenyl)-N,N-dimethylmethylamine, isobutylamine, dimethylacetamide, dimethylamine, and 3-isopropoxypropylamine; The imidazole solvents include at least one of 1-methylimidazolium, 1-ethylimidazolium, 1-propylimidazolium, 1-isopropylimidazolium, 1-tert-butylimidazolium, 1-allylimidazolium, and 1-trimethylsilylimidazolium; The phosphate ester solvents include at least one of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, and tributyl phosphate; The ionic liquid comprises at least one of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imine, and N-butyl-N-methylpiperidine bis(trifluoromethanesulfonyl)imine.

[0011] Preferably, the volume ratio of the oxygen-containing cycloalkane to the auxiliary solvent is 1~10:0~1, and is not 0.

[0012] Preferably, the magnesium salt comprises at least one of magnesium tetra(hexafluoroisopropoxy)borate, magnesium trifluoromethanesulfonate, bis(trifluoromethanesulfonylimide)magnesium, bis(hexamethyldisilazon)magnesium, and bis(diisopropylamino)magnesium.

[0013] Preferably, the concentration of magnesium salt in the magnesium ion electrolyte is 0.01~1.5 mol / L.

[0014] The present invention also provides a method for preparing the magnesium ion electrolyte described in the above technical solution, comprising the following steps: dissolving magnesium salt in a solvent to obtain the magnesium ion electrolyte.

[0015] Preferably, the dissolution is carried out in a glove box filled with a protective gas, the protective gas being argon, and the total content of oxygen and water in the glove box is less than 0.5 ppm; The dissolution is carried out under stirring conditions, with the stirring temperature being 0~100℃ and the time being 6~72h.

[0016] This invention provides the application of oxygen-containing cycloalkanes in magnesium ion electrolytes, wherein the main chain of the oxygen-containing cycloalkanes has at least 3 carbon atoms and at least 2 oxygen atoms. This invention uses oxygen-containing cycloalkanes as a solvent for magnesium ion electrolytes, which can effectively improve battery cycle life and coulombic efficiency. Magnesium ion electrolytes based on oxygen-containing cycloalkanes can be applied to rechargeable magnesium batteries. Details are as follows: (1) Non-corrosive: In this invention, oxygen-containing cycloalkanes are used as solvents to develop a new type of non-corrosive magnesium ion electrolyte, which solves the corrosion problem caused by chloride electrolytes.

[0017] (2) Long lifespan: The magnesium ion electrolyte prepared based on oxygen-containing cycloalkanes can form an SEI rich in organic polymers on the surface of magnesium metal anode, which induces uniform magnesium deposition and extends the cycle life of the battery.

[0018] (3) High coulombic efficiency: The organic polymer formed by the in-situ reduction and decomposition of oxygen-containing cycloalkanes has excellent stability and flexibility, and is not easy to break during repeated magnesium deposition / dissolution, which effectively improves the coulombic efficiency of the battery, thus enabling long-term electrochemical cycling under low electrolyte conditions. Attached Figure Description

[0019] Figure 1 The deposition-dissolution performance of Mg / / Mg symmetric cells in Mg[B(hfip)4]2 / DOX electrolyte; Figure 2 The specific capacity-voltage diagram of the Mg / / FeHCF full cell in Mg[B(hfip)4]2 / DOX electrolyte is shown. Figure 3The deposition-dissolution performance of Mg / / Mg symmetric cells in Mg[B(hfip)4]2 / DOX-THF=1-1 electrolyte; Figure 4 The deposition-dissolution performance of Mg / / Mg symmetric cells in Mg[B(hfip)4]2 / DOX-DME=9-1 electrolyte; Figure 5 The deposition-dissolution performance of Mg[B(hfip)4]2 / DME electrolyte in Mg / / Mg symmetric cells; Figure 6 XPS images of magnesium metal anodes after deposition and dissolution in Mg[B(hfip)4]2 / DME electrolyte; Figure 7 XPS images of magnesium metal anodes after deposition and dissolution in Mg[B(hfip)4]2 / DOX electrolyte; Figure 8 The deposition-dissolution curves of Mg / / Mg symmetric cells in Mg(OTf)2 / DOX-TEP=3-1 electrolyte are shown. Figure 9 The coulombic efficiency of the Mg / / Cu half-cell in Mg(TFSI)2 / DOX-MOPA=3-2 electrolyte is shown in the diagram. Figure 10 The coulombic efficiency diagram of the Mg / / Cu half-cell in Mg[B(hfip)4]2 / DOL electrolyte is shown. Detailed Implementation

[0020] This invention provides an application of oxygen-containing cycloalkanes in magnesium ion electrolytes, wherein the main chain of the oxygen-containing cycloalkanes has no less than 3 carbon atoms and no less than 2 oxygen atoms.

[0021] In this invention, the oxygen-containing cycloalkanes preferably include at least one of 1,3-dioxane, 1,4-dioxane, 1,3-dioxolane, 4-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, and 1,3,5-trioxane.

[0022] In this invention, the structural formula of the 1,3-dioxane is shown below. .

[0023] The present invention also provides a magnesium ion electrolyte, comprising a magnesium salt and a solvent; the solvent comprises an oxygen-containing cycloalkanes; the main chain of the oxygen-containing cycloalkanes has not less than 3 carbon atoms and not less than 2 oxygen atoms.

[0024] In this invention, the oxygen-containing cycloalkanes preferably include at least one of 1,3-dioxane, 1,4-dioxane, 1,3-dioxolane, 4-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, and 1,3,5-trioxane.

[0025] In this invention, the solvent preferably also includes an auxiliary solvent, which preferably includes at least one of ether solvents, amine solvents, imidazole solvents, phosphate ester solvents and ionic liquids.

[0026] In this invention, the ether solvent includes at least one of tetrahydrofuran (THF), diethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (DG), and tetraethylene glycol dimethyl ether (TG).

[0027] In this invention, the amine solvent preferably includes at least one of 2-methoxyethylamine (MOEA), 3-methoxypropylamine (MOPA), 3-dimethylaminopropylamine (DMAPA), 1-(3-bromophenyl)-N,N-dimethylmethylamine (BPDMA), isobutylamine (IBA), dimethylacetamide (DMAC), dimethylamine (DMA), and 3-isopropoxypropylamine (iPOPA).

[0028] In this invention, the imidazole solvent includes 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).

[0029] In this invention, the phosphate ester solvent preferably includes at least one of trimethyl phosphate (TMP), triethyl phosphate (TEP), tripropyl phosphate (TPP), and tributyl phosphate (TBP).

[0030] In this invention, the ionic liquid preferably includes at least one of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imine, and N-butyl-N-methylpiperidine bis(trifluoromethanesulfonyl)imine.

[0031] In this invention, the volume ratio of the oxygen-containing cycloalkanes to the auxiliary solvent is preferably 1~10:0~1, and not 0, specifically 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1.

[0032] In this invention, the magnesium salt preferably includes at least one of the following: magnesium tetra(hexafluoroisopropoxy)borate (Mg[B(hfip)4]2), magnesium trifluoromethanesulfonate (Mg(OTf)2), magnesium bis(trifluoromethanesulfonylimide) (Mg(TFSI)2), magnesium bis(hexamethyldisilazon) (Mg(HMDS)2), and magnesium bis(diisopropylamino) (Mg[N(C3H7)]2).

[0033] In this invention, the concentration of magnesium salt in the magnesium ion electrolyte is preferably 0.01~1.5 mol / L, specifically 0.01 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.5 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, or 1.5 mol / L.

[0034] The present invention also provides a method for preparing the magnesium ion electrolyte described in the above technical solution, comprising the following steps: dissolving magnesium salt in a solvent to obtain the magnesium ion electrolyte.

[0035] In this invention, the dissolution is preferably carried out in a glove box filled with a protective gas, preferably argon, and the total content of oxygen and water in the glove box is preferably less than 0.5 ppm; the dissolution is preferably carried out under stirring conditions, the stirring temperature is preferably 0~100℃, specifically 0℃, 25℃, 30℃, 50℃, 100℃; the stirring time is preferably 6~72h, specifically 6h, 12h, 24h, 36h, 72h.

[0036] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0037] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0038] Example 1 In a glove box filled with argon and containing less than 0.5 ppm of oxygen and water, magnesium tetra(hexafluoroisopropoxy)borate (Mg[B(hfip)4]2) was dissolved in 1,3-dioxane (DOX) and magnetically stirred at 25 °C for 12 h to prepare a Mg[B(hfip)4]2 / DOX magnesium ion electrolyte, wherein the concentration of magnesium salt was 0.3 mol / L.

[0039] The obtained electrolyte was used to assemble a Mg / / Mg symmetric cell (electrolyte volume 20 μL). Figure 1It shows that it can operate at 0.5 mA / cm 2 Current density, 0.25 mAh / cm 2 It exhibits excellent cycle stability with reversible cycling at its surface capacity and a battery life exceeding 900 hours.

[0040] Given the stable organic polymer SEI formed by DOX solvent at the magnesium anode interface, the electrolyte obtained above was used to assemble a Mg / / FeHCF full cell to verify its application in magnesium secondary batteries. Figure 2 The results show that, under reversible cycling at a 0.5C rate, its specific capacity reaches 44 mAh·g after 40 cycles. -1 .

[0041] Example 2 In a glove box filled with argon and containing less than 0.5 ppm of oxygen and water, magnesium tetra(hexafluoroisopropoxy)borate (Mg[B(hfip)4]2) was dissolved in 1,3-dioxane (DOX) and tetrahydrofuran (THF) (volume ratio 1:1), and the mixture was magnetically stirred at 25 °C for 12 h to prepare a magnesium ion electrolyte of Mg[B(hfip)4]2 / DOX-THF=1-1, wherein the concentration of magnesium salt was 0.3 mol / L.

[0042] The obtained electrolyte was used to assemble a Mg / / Mg symmetric cell (electrolyte volume 20 μL). Figure 3 It shows that it can operate at 0.5 mA / cm 2 Current density, 0.25 mAh / cm 2 It exhibits excellent cycle stability with reversible cycling at its surface capacity and a battery life exceeding 1200 hours.

[0043] Example 3 In a glove box filled with argon and containing less than 0.5 ppm of oxygen and water, magnesium tetra(hexafluoroisopropoxy)borate (Mg[B(hfip)4]2) was dissolved in 1,3-dioxane (DOX) and dimethyl ethylene glycol (DME) (volume ratio 9:1), and the mixture was magnetically stirred at 25 °C for 12 h to prepare a magnesium ion electrolyte of Mg[B(hfip)4]2 / DOX-DME=9-1, wherein the concentration of magnesium salt was 0.3 mol / L.

[0044] The obtained electrolyte was used to assemble a Mg / / Mg symmetric cell (electrolyte volume 20 μL). Figure 4 It shows that it can operate at 0.5 mA / cm 2 Current density, 0.25 mAh / cm 2 It exhibits excellent cycle stability with reversible cycling at its surface capacity and a battery life exceeding 750 hours.

[0045] Comparative Example 1 The magnesium ion electrolyte was prepared according to the method of Example 1, wherein the solvent was replaced with dimethyl ethylene glycol ether (DME). The obtained electrolyte was used to assemble a Mg / / Mg symmetric cell (electrolyte volume 20 μL). Figure 5 It shows that it can operate at 0.5 mA / cm 2 Current density, 0.25 mAh / cm 2 Despite being reversible in its capacity, the battery short-circuited after only 125 hours, demonstrating poor performance and lifespan.

[0046] Figure 6 and Figure 7 The images show the X-ray photoelectron spectroscopy (XPS) spectra of the magnesium metal anodes in Example 1 and Comparative Example 1 after deposition-dissolution at C 1s and O 1s. The XPS spectra show that after deposition-dissolution, the Mg[B(hfip)4]2 / DOX electrolyte with 1,3-dioxane as the main solvent forms a more significant organic polymer layer (mainly composed of CO) on the surface of the magnesium anode. This organic layer can effectively suppress the continuous side reactions between the magnesium anode and the electrolyte, achieve uniform magnesium deposition / dissolution, and effectively extend the battery life.

[0047] Example 4 In a glove box filled with argon and containing less than 0.5 ppm of oxygen and water, magnesium trifluoromethanesulfonate (Mg(OTf)2) was dissolved in 1,3-dioxane (DOX) and triethyl phosphate (TEP) (volume ratio 3:1), and the mixture was magnetically stirred at 25 °C for 24 h to prepare a magnesium ion electrolyte of Mg(OTf)2 / DOX-TEP=3-1, wherein the concentration of magnesium salt was 0.3 mol / L.

[0048] The obtained electrolyte was used to assemble a Mg / / Mg symmetric cell (electrolyte volume 20 μL). Figure 8 It shows that it can operate at 0.5 mA / cm 2 Current density, 0.5 mAh / cm 2 It features reversible cycling at its surface capacity and a battery life exceeding 300 hours.

[0049] Example 5 In a glove box filled with argon and containing less than 0.5 ppm of oxygen and water, magnesium bis(trifluoromethanesulfonylimide) (Mg(TFSI)2) was dissolved in 1,3-dioxane (DOX) and 3-methoxypropylamine (MOPA) (volume ratio 3:2), and the mixture was magnetically stirred at 25 °C for 12 h to prepare a magnesium ion electrolyte of Mg(TFSI)2 / DOX-MOPA=3-2, wherein the concentration of magnesium salt was 0.3 mol / L.

[0050] The obtained electrolyte was used to assemble a Mg / / Cu battery (electrolyte volume 20 μL). Figure 9 It shows that it can operate at 0.5 mA / cm 2 Current density, 0.1 mAh / cm 2 It operates stably under its surface capacity and has an average coulomb efficiency of 94.57% after more than 150 cycles.

[0051] Example 6 In a glove box filled with argon and containing less than 0.5 ppm of oxygen and water, magnesium tetra(hexafluoroisopropoxy)borate (Mg[B(hfip)4]2) was dissolved in 1,3-dioxolane (DOL) and magnetically stirred at 25 °C for 12 h to prepare a Mg[B(hfip)4]2 / DOX magnesium ion electrolyte, wherein the concentration of magnesium salt was 0.3 mol / L.

[0052] The obtained electrolyte was used to assemble a Mg / / Cu battery (electrolyte volume 20 μL). Figure 10 This indicates that it can reach 1mA / cm 2 Current density, 0.5 mAh / cm 2 It operates stably under its surface capacity and has an average coulomb efficiency of 96.37% after more than 100 cycles.

[0053] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. The application of an oxygen-containing cycloalkanes in magnesium ion electrolytes, characterized in that, The oxygen-containing cycloalkanes have at least 3 carbon atoms in their main chain and at least 2 oxygen atoms in their main chain.

2. The application according to claim 1, characterized in that, The oxygen-containing cycloalkanes include at least one of 1,3-dioxane, 1,4-dioxane, 1,3-dioxolane, 4-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, and 1,3,5-trioxane.

3. A magnesium ion electrolyte, characterized in that, Includes magnesium salts and solvents; the solvents include oxygen-containing cycloalkanes; The oxygen-containing cycloalkanes have at least 3 carbon atoms in their main chain and at least 2 oxygen atoms in their main chain.

4. The magnesium ion electrolyte according to claim 3, characterized in that, The solvent also includes an auxiliary solvent, which includes at least one of ether solvents, amine solvents, imidazole solvents, phosphate ester solvents, and ionic liquids.

5. The magnesium ion electrolyte according to claim 3, characterized in that, The ether solvent includes at least one of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; The amine solvents include at least one of 2-methoxyethylamine, 3-methoxypropylamine, 3-dimethylaminopropylamine, 1-(3-bromophenyl)-N,N-dimethylmethylamine, isobutylamine, dimethylacetamide, dimethylamine, and 3-isopropoxypropylamine; The imidazole solvents include at least one of 1-methylimidazolium, 1-ethylimidazolium, 1-propylimidazolium, 1-isopropylimidazolium, 1-tert-butylimidazolium, 1-allylimidazolium, and 1-trimethylsilylimidazolium; The phosphate ester solvents include at least one of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, and tributyl phosphate; The ionic liquid comprises at least one of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imine, and N-butyl-N-methylpiperidine bis(trifluoromethanesulfonyl)imine.

6. The magnesium ion electrolyte according to claim 4 or 5, characterized in that, The volume ratio of the oxygen-containing cycloalkanes to the auxiliary solvent is 1~10:0~1, and is not 0.

7. The magnesium ion electrolyte according to claim 3, characterized in that, The magnesium salt includes at least one of magnesium tetra(hexafluoroisopropoxy)borate, magnesium trifluoromethanesulfonate, bis(trifluoromethanesulfonylimide) magnesium, bis(hexamethyldisilazido) magnesium, and bis(diisopropylamino) magnesium.

8. The magnesium ion electrolyte according to claim 3 or 7, characterized in that, The concentration of magnesium salt in the magnesium ion electrolyte is 0.01~1.5 mol / L.

9. The method for preparing the magnesium ion electrolyte according to any one of claims 3 to 8, characterized in that, Includes the following steps: The magnesium salt is dissolved in a solvent to obtain the magnesium ion electrolyte.

10. The preparation method according to claim 9, characterized in that, The dissolution is carried out in a glove box filled with a protective gas, namely argon, and the total content of oxygen and water in the glove box is less than 0.5 ppm; The dissolution is carried out under stirring conditions, with the stirring temperature being 0~100℃ and the time being 6~72h.

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