Amine additive-based ester and nitrile electrolyte of rechargeable magnesium battery and battery

Abstract

The invention discloses an ester and nitrile electrolyte of a rechargeable magnesium battery based on an amine additive and the battery. The electrolyte is composed of electrolyte salt and a non-aqueous solvent, the non-aqueous solvent is composed of a main solvent and an additive, the main solvent is an ester organic solvent or a nitrile organic solvent, and the additive is an amine compound; wherein the concentration of the electrolyte salt in the electrolyte ranges from 0.01 mol / L to the maximum solubility of the electrolyte salt, and the additive accounts for 1%-40% of the volume of the main solvent. The electrolyte is modified through the additive, the solvation structure of the electrolyte is improved, the magnesium metal negative electrode is protected, the deposition and dissolution overpotential of the magnesium metal negative electrode in ester and nitrile solvents is greatly reduced, and construction of an ester or nitrile-based magnesium metal battery system is facilitated. And meanwhile, the compatibility between the positive electrode and the negative electrode of the electrolyte and the electrolyte is realized, the electrochemical window of the electrolyte and the application range of the positive electrode material are remarkably widened, and the large-scale application prospect and the huge commercial development value are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of magnesium metal rechargeable batteries, and in particular relates to an electrolyte based on amine additives, and a preparation method and application thereof. Background Art

[0002] Rechargeable magnesium battery is a multivalent metal battery with great development potential. Compared with lithium metal battery, magnesium negative electrode has many advantages: its volume energy density is higher than lithium (3833mAh / cc Mg vs. 2046mAh / cc Li); at the same time, magnesium resources are abundant in the earth's crust, and the price of magnesium is much cheaper than lithium; in addition, unlike lithium, magnesium tends to form a smooth plane during the deposition process, and is not easy to form dendrites, and magnesium metal is relatively stable at room temperature and safer. Therefore, magnesium secondary batteries are expected to have significant advantages over lithium secondary batteries in terms of cost and safety.

[0003] However, due to the high reactivity brought by the lower electrode potential of magnesium metal, the magnesium metal negative electrode is very easy to react with the solvent in the electrolyte to form a solid interface layer during the battery cycle, and the high charge density divalent magnesium ions are difficult to migrate in the generated interface layer to produce negative electrode passivation, and cause irreversible magnesium deposition and dissolution behavior and ultra-high overpotential on the negative electrode side, which ultimately leads to battery failure. Therefore, the solvents of magnesium battery electrolytes are currently concentrated in ether systems that are stable to magnesium metal, because the magnesium negative electrode is not easy to react with ether solvents during the electrochemical cycle, thus ensuring the freshness of the negative electrode interface and no adverse passivation film formation. However, the electrochemical window of the ether system is narrow and is incompatible with most positive electrode materials, which greatly limits the application range of the ether electrolyte system. In contrast, the ester system or nitrile system has higher compatibility with most positive electrodes, and has a higher oxidation stability window, so it can match higher voltage positive electrode materials. However, due to the high reactivity of ester solvents and nitrile solvents themselves to the magnesium negative electrode, this type of electrolyte system is also unable to match the magnesium metal negative electrode. Therefore, designing advanced electrolytes that are compatible with both high-voltage positive electrode materials and magnesium metal negative electrode materials has become a hot topic and a major challenge in the development of magnesium batteries. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an ester and nitrile electrolyte for a rechargeable magnesium battery based on amine additives and a preparation method and application thereof, thereby solving the problems in the above-mentioned background technology.

[0005] One of the technical solutions adopted by the present invention to solve its technical problems is: providing an ester and nitrile electrolyte for a rechargeable magnesium battery based on an amine additive, which is composed of an electrolyte salt and a non-aqueous solvent, wherein the non-aqueous solvent is composed of a main solvent and an additive, wherein the main solvent is an ester organic solvent or a nitrile organic solvent, and the additive is an amine compound; wherein the concentration range of the electrolyte salt in the electrolyte is from 0.01 mol / L to the maximum solubility of the electrolyte salt, and the additive accounts for 1% to 40% of the volume of the main solvent.

[0006] In a preferred embodiment of the present invention, the ester organic solvent includes at least one of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC).

[0007] In a preferred embodiment of the present invention, the nitrile organic solvent includes at least one of acetonitrile (AN) or succinonitrile.

[0008] In a preferred embodiment of the present invention, the amine compound is at least one of 3-methoxypropylamine, 2-methoxyethylamine, 1,3-propylenediamine, 2-ethoxyethylamine, N-(2-methoxyethyl)methylamine, and 2-amino-1-methoxybutane.

[0009] In a preferred embodiment of the present invention, the volume of the additive accounts for 1% to 40% of the main solvent.

[0010] In a preferred embodiment of the present invention, the electrolyte salt comprises Mg(TFSI) 2 、Mg(PF 6 ) 2 、Mg(OTf) 2 Mg(BF 4 ) 2 MgCl 2 Mg(ClO 4 ) 2 MgSO 4 Mg 3 (PO 4 ) 2 Mg(NO 3 ) 2 .

[0011] The second technical solution adopted by the present invention to solve the technical problem is: a method for preparing an electrolyte based on amine additives is provided, comprising the following steps:

[0012] 1) Weigh the electrolyte salt and dry it in a vacuum oven until it is completely dry;

[0013] 2) Take the main solvent and additives, add molecular sieves for pre-drying, mix them in proportion after drying, and stir at room temperature to mix them evenly;

[0014] 3) Mixing the electrolyte salt with the solvent prepared in step 2), stirring at room temperature using magnetic stirring until the electrolyte salt is completely dissolved; then adding molecular sieves and drying until the water content is less than 20 ppm, the electrolyte is prepared.

[0015] The third technical solution adopted by the present invention to solve its technical problem is: to provide an application of an electrolyte based on amine additives for a rechargeable magnesium battery.

[0016] The fourth technical solution adopted by the present invention to solve its technical problem is: providing a rechargeable magnesium battery, including a positive electrode, a metal magnesium negative electrode and an electrolyte, wherein the electrolyte is the above-mentioned electrolyte based on amine additives.

[0017] In a preferred embodiment of the present invention, the positive electrode material includes but is not limited to MnO 2 、V 2 O 5 MgMn 2 O 4 Iso-oxide positive electrode, S, Mo 6 S 8 A sulfide positive electrode, a polyanion positive electrode, an organic positive electrode, or one of the modified materials of the above materials.

[0018] Compared with the background technology, this technical solution has the following advantages:

[0019] 1. The electrolyte of the present invention improves the solvation structure of the electrolyte and protects the magnesium metal negative electrode by adding an amine additive having a N atom functional group to the main solvent, through the regulation of the solvation structure of magnesium ions by amine molecules and the protective effect of amine molecules on the magnesium negative electrode interface, so that the magnesium metal negative electrode can achieve a lower cycle overpotential in ester and nitrile solvents.

[0020] 2. The electrolyte of the present invention uses esters and nitriles as main solvents, which significantly broadens the electrochemical window of the electrolyte and the applicable scope of the positive electrode material, is conducive to the development of high-voltage magnesium metal batteries, and has large-scale application prospects.

[0021] 3. Since amine molecules can enhance the kinetics of the magnesium metal negative electrode, the organic rechargeable magnesium battery using the electrolyte of the present invention can perfectly match the high-voltage positive electrode material, while satisfying the compatibility of the high-voltage positive electrode material and the magnesium metal negative electrode material, and can have excellent electrochemical performance and cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1Figure 2 shows a Mg / / Mg symmetric cell with a current density of 0.1 mA / cm -2 , area capacity is 0.1mAh / cm -2 .

[0023] Figure 2A A time-voltage diagram showing a Mg / / SS (stainless steel) half-cell test, Figure 2B Coulombic efficiency plot showing the Mg / / SS half-cell test at a current density of 0.1 mA / cm -2 , area capacity is 0.1mAh / cm -2 .

[0024] Figure 3 Shown is the cyclic voltammogram of Mg / / SS with a scan rate of 25 mV / s.

[0025] Figure 4 Shows Mg / / Mo 6 S 8 Full battery charge and discharge curve, the positive electrode material is Mo 6 S 8 , the current density is 5mA / g.

[0026] Figure 5 Shown is Mg / / V 2 O 5 Full battery charge and discharge curve, positive electrode material is V 2 O 5 , the current density is 5mA / g. DETAILED DESCRIPTION

[0027] Example 1

[0028] This embodiment provides an electrolyte based on amine additives, wherein the magnesium salt of the electrolyte is selected from Mg(TFSI) 2 The main solvent is propylene carbonate, an ester solvent, and the amine additive is 3-methoxypropylamine. The volume mixing ratio is 4:1, and the preparation concentration is 0.5 mol / L. The electrolyte preparation method is as follows:

[0029] 1) Weigh the electrolyte salt and dry it in a vacuum oven for several hours until it is completely dry;

[0030] 2) adding the ester organic main solvent and the amine additive solvent to molecular sieves for pre-drying, and after drying completely, stirring at room temperature in a ratio of 4:1 to mix them evenly;

[0031] 3) mixing the electrolyte salt with the solvent prepared in step 2), stirring at room temperature for several hours using a magnetic stirrer until the electrolyte salt is completely dissolved; then adding a molecular sieve and drying for several hours, the drying process is repeated at least three times until the water content is less than 20 ppm using a Karl Fischer water meter, and the electrolyte is prepared.

[0032] The electrolyte of this embodiment was used to assemble Mg / / Mg symmetric battery, Mg / / SS semi-symmetric battery, Mo 6 S 8 / / Mg full battery, test results are shown in the attached figure.

[0033] Figure 1 The cycling diagram of the Mg / / Mg symmetric battery using 3-methoxypropylamine as an additive is shown. The test results show that the -2 Under the above conditions, the symmetrical battery with the electrolyte of Example 1 has an ultra-low overpotential (less than 0.15 V) and can maintain a cycle performance of more than 30 hours, indicating that this type of electrolyte has excellent electrochemical properties of magnesium metal negative electrode.

[0034] Figure 2A The cycling diagram of the Mg / / SS semi-symmetric battery using 3-methoxypropylamine as an additive is shown. The test results show that the -2 Under these conditions, it can undergo a reversible deposition-dissolution cycle, and both the deposition overpotential and the dissolution overpotential are low; Figure 2B The Coulombic efficiency curve of the Mg / / SS semi-symmetric cell using 3-methoxypropylamine as the solvent is shown. The test results show that the Mg / / SS semi-symmetric cell has a coulombic efficiency of 0.1 mA / cm -2 Under the same conditions, the average coulombic efficiency can be maintained at more than 60% for more than 20 cycles. These test results show that this type of electrolyte has excellent electrochemical performance of magnesium metal anode.

[0035] Figure 3 The cyclic voltammogram of Mg / / SS using 3-methoxypropylamine as an additive is shown. The test results show that under the condition of 25mV / s, it has a very low deposition or stripping overpotential, and can undergo reversible deposition and dissolution cycles. Its high response current also indicates its excellent electrochemical reaction kinetics. The test results show that this type of electrolyte has excellent electrochemical performance of magnesium metal anode.

[0036] Figure 4 Mg / / Mo using 3-methoxypropylamine as an additive is shown 6 S 8 From the charge and discharge curve of the full battery, it can be seen that the rechargeable magnesium battery has a higher charge and discharge voltage platform and a higher discharge capacity at a current density of 5 mA / g. The test results show that the electrolyte of this embodiment has excellent electrochemical properties.

[0037] Figure 5 The Mg / / V using 3-methoxypropylamine as an additive is shown. 2 O 5From the charge and discharge curve of the full battery, it can be seen that the rechargeable magnesium battery has a higher charge and discharge voltage platform and a higher discharge capacity at a current density of 5 mA / g. The test results show that the electrolyte of this embodiment has excellent electrochemical properties.

[0038] Example 2

[0039] The difference between this embodiment and embodiment 1 is that the magnesium salt is Mg(TFSI) 2 The main solvent is ester solvent propylene carbonate, the amine additive is 3-methoxypropylamine, the volume mixing ratio is 4:1, and the preparation concentration is 1.0 mol / L.

[0040] Example 3

[0041] The difference between this embodiment and embodiment 1 is that the magnesium salt is MgCl 2 The main solvent is ester solvent propylene carbonate, the amine additive is 2-methoxyethylamine, the volume mixing ratio is 4:1, and the preparation concentration is 0.5 mol / L.

[0042] Example 4

[0043] The difference between this embodiment and embodiment 1 is that the magnesium salt is MgCl 2 The main solvent is ester solvent propylene carbonate, the amine additive is 2-methoxyethylamine, the volume mixing ratio is 4:1, and the preparation concentration is 1.0 mol / L.

[0044] Example 5

[0045] The difference between this embodiment and embodiment 1 is that the magnesium salt is Mg(ClO 4 ) 2 The main solvent is ester solvent ethylene carbonate, the amine additive is 2-methoxyethylamine, the volume mixing ratio is 4:1, and the preparation concentration is 0.1 mol / L.

[0046] Example 6

[0047] The difference between this embodiment and embodiment 1 is that the magnesium salt is Mg(NO 3 ) 2 The main solvent is ester solvent propylene carbonate, the amine additive is 2-methoxyethylamine, the volume mixing ratio is 4:1, and the preparation concentration is 0.5 mol / L.

[0048] Example 7

[0049] The difference between this embodiment and embodiment 1 is that the magnesium salt is Mg 3 (PO 4 ) 2The main solvent is ester solvent propylene carbonate, the amine additive is 2-methoxyethylamine, the volume mixing ratio is 3:2, and the preparation concentration is 0.5 mol / L.

[0050] Example 8

[0051] The difference between this embodiment and embodiment 1 is that the magnesium salt is Mg(NO 3 ) 2 The main solvent is ester solvent propylene carbonate, the amine additive is 3-methoxypropylamine, the volume mixing ratio is 3:2, and the preparation concentration is 0.5 mol / L.

[0052] Example 9

[0053] The difference between this embodiment and embodiment 1 is that the magnesium salt is Mg(NO 3 ) 2 The main solvent is acetonitrile, an ester solvent, and the amine additive is 3-methoxypropylamine. The volume mixing ratio is 4:1, and the preparation concentration is 1.0 mol / L.

[0054] Example 10

[0055] The difference between this embodiment and embodiment 1 is that the magnesium salt is MgCl 2 The main solvent is acetonitrile, an ester solvent, and the amine additive is 3-methoxypropylamine. The volume mixing ratio is 3:2, and the preparation concentration is 0.5 mol / L.

[0056] Comparative Example 1

[0057] The difference between this comparative example and Example 1 is that the magnesium salt is Mg(TFSI) 2 The solvent is single propylene carbonate, and the preparation concentration is 0.1 mol / L.

[0058] Comparative Example 2

[0059] The difference between this comparative example and Example 1 is that the magnesium salt is Mg(TFSI) 2 The solvent is single propylene carbonate, and the preparation concentration is 0.2 mol / L.

[0060] Comparative Example 3

[0061] The difference between this comparative example and Example 1 is that the magnesium salt is Mg(TFSI) 2 The solvent is single propylene carbonate, and the preparation concentration is 0.3 mol / L.

[0062] Comparative Example 4

[0063] The difference between this comparative example and Example 1 is that the magnesium salt is Mg(TFSI) 2The solvent is single propylene carbonate, and the preparation concentration is 0.5 mol / L.

[0064] Comparative Example 5

[0065] The difference between this comparative example and Example 1 is that the magnesium salt is Mg(TFSI) 2 The solvent is single propylene carbonate, and the preparation concentration is 1.0 mol / L.

[0066] Comparative Example 6

[0067] The difference between this comparative example and Example 1 is that the magnesium salt is MgCl 2 The solvent is single propylene carbonate, and the preparation concentration is 0.1 mol / L.

[0068] Comparative Example 7

[0069] The difference between this comparative example and Example 1 is that the magnesium salt is MgCl 2 The solvent is single ethylene carbonate, and the preparation concentration is 0.5 mol / L.

[0070] Comparative Example 8

[0071] The difference between this comparative example and Example 1 is that the magnesium salt is MgCl 2 The solvent is single acetonitrile and the preparation concentration is 0.1 mol / L.

[0072] Comparative Example 9

[0073] The difference between this comparative example and Example 1 is that the magnesium salt is MgCl 2 The solvent is single acetonitrile, and the preparation concentration is 0.2 mol / L.

[0074] Comparative Example 10

[0075] The difference between this comparative example and Example 1 is that the magnesium salt is MgCl 2 The solvent is single acetonitrile and the preparation concentration is 0.3 mol / L.

[0076] Table 1 Comparison of coulombic efficiency of Examples 1-12 and Comparative Examples 1-10

[0077]

[0078]

[0079] As can be seen from Table 1, when an amine compound is used as an additive, reversible deposition and dissolution of magnesium metal can be performed, and high coulomb efficiency (>60%) and low overpotential (<0.2V) are maintained; when esters or nitriles are used as pure solvents, reversible deposition and dissolution cycles cannot be performed due to the large overpotential, and the coulomb efficiency is 0.0% and the overpotential is greater than 2.0V. It can be seen that the electrolyte of the present invention improves the solvation structure of the electrolyte and protects the magnesium metal negative electrode by adding an amine additive having a N atom functional group to the main solvent, through the regulation of the solvation structure of magnesium ions by amine molecules and the protective effect of amine molecules on the magnesium negative electrode interface, so that the magnesium metal negative electrode can achieve a lower cycle overpotential in ester and nitrile solvents.

[0080] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte based on amine additives, Features: It is composed of an electrolyte salt and a non-aqueous solvent, wherein the non-aqueous solvent is composed of a main solvent and an additive, wherein the main solvent is an ester organic solvent or a nitrile organic solvent, and the additive is an amine compound; wherein the concentration range of the electrolyte salt in the electrolyte is from 0.01 mol / L to the maximum solubility of the electrolyte salt, and the volume of the additive accounts for 1% to 40% of the main solvent.

2. An electrolyte based on amine additives according to claim 1, Features: The ester organic solvent includes at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate.

3. An electrolyte based on amine additives according to claim 1, Features: The nitrile organic solvent includes at least one of acetonitrile or succinonitrile.

4. An electrolyte based on amine additives according to claim 1, Features: The amine compound is at least one of 3-methoxypropylamine, 2-methoxyethylamine, 1,3-propylenediamine, 2-ethoxyethylamine, N-(2-methoxyethyl)methylamine and 2-amino-1-methoxybutane.

5. An electrolyte based on amine additives according to claim 1, Features: The volume of the additive accounts for 1% to 40% of the main solvent.

6. An electrolyte based on amine additives according to claim 1, Features: The electrolyte salt includes Mg(TFSI) 2 、Mg(PF 6 ) 2 、Mg(OTf) 2 Mg(BF 4 ) 2 MgCl 2 Mg(ClO 4 ) 2 MgSO 4 Mg 3 (PO 4 ) 2 Mg(NO 3 ) 2 .

7. A method for preparing an electrolyte based on amine additives according to any one of claims 1 to 6, Features: The steps include: 1) Weigh the electrolyte salt and dry it in a vacuum oven until it is completely dry; 2) Take the main solvent and additives, add molecular sieves for pre-drying, mix them in proportion after drying, and stir at room temperature to mix them evenly; 3) Mixing the electrolyte salt with the solvent prepared in step 2), stirring at room temperature using magnetic stirring until the electrolyte salt is completely dissolved; then adding molecular sieves and drying until the water content is less than 20 ppm, the electrolyte is prepared.

8. Use of an electrolyte based on amine additives as claimed in any one of claims 1 to 6, Features: For use in rechargeable magnesium batteries.

9. A rechargeable magnesium battery, Features: The invention comprises a positive electrode, a metal magnesium negative electrode and an electrolyte, wherein the electrolyte is an electrolyte based on an amine additive as claimed in any one of claims 1 to 6.

10. A rechargeable magnesium battery according to claim 9, Features: The positive electrode material includes MnO 2 、V 2 O 5 MgMn 2 O 4 , S, Mo 6 S 8 .

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