A High-Performance Gel Electrolyte for Magnesium-Lithium Dual-Ion Batteries and Its Preparation Method

Abstract

The present invention discloses a high-performance gel electrolyte for a magnesium-lithium dual-ion battery in the technical field of magnesium-lithium dual-ion batteries and a preparation method thereof, aiming to solve the problems in the prior art that the liquid electrolyte is prone to leakage and Mg dendrites exist, which may pierce the separator and cause short circuit between the positive and negative electrodes of the battery. It includes steps such as the preparation of HCA fiber membrane, the preparation of ZIF-67@HCA fiber membrane, and the preparation of ZIF-67@HCA gel electrolyte. The high-performance gel electrolyte prepared by the present invention can effectively regulate the ion concentration of Mg<supgt;2+< / supgt; on the surface of the negative electrode, thereby inhibiting the generation of magnesium dendrites, effectively promoting ion transport, and improving the ionic conductivity.

Description

Technical Field

[0001] The present invention relates to a high-performance gel electrolyte for a magnesium-lithium dual-ion battery and a preparation method thereof, belonging to the technical field of magnesium-lithium dual-ion batteries. Background Art

[0002] Lithium-ion batteries have occupied a dominant position in various fields due to a series of advantages such as high energy density, long cycle life, no memory effect, and low self-discharge. Therefore, the problem of limited lithium resources on the earth has gradually become one of the most worrying problems in the lithium-ion battery manufacturing industry. Compared with lithium-ion batteries, magnesium-ion batteries have a series of advantages: First, magnesium is the eighth most abundant element in the earth's crust, with lower costs; second, the magnesium negative electrode has a higher volume specific capacity; in addition, magnesium metal has good air stability. Therefore, magnesium-ion batteries have always received the attention of researchers.

[0003] However, there is a key restrictive problem in the magnesium-ion battery (MIB) system, that is, the diffusion kinetics of Mg 2+ in the electrode is relatively slow. Currently, the concept of dual-ion batteries has made the magnesium-lithium dual-ion battery (MLIB) a research hotspot, and its emergence provides a direction for the development of MIB. First, MLIB will continue to maintain the advantages of the metallic magnesium negative electrode in MIB; second, MLIB avoids the disadvantages of slow insertion and extraction of magnesium ions in the positive electrode material.

[0004] However, due to relatively few studies on the MLIB battery system, the existing electrolyte systems are mostly liquid electrolyte systems, which have risks such as leakage; at the same time, with the gradual in-depth research, researchers have found that at high current densities, Mg 2+ will also generate Mg dendrites during the deposition / dissolution process on the negative electrode surface, and there is a problem of short circuit between the positive and negative electrodes of the battery caused by piercing the separator. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a high-performance gel electrolyte for a magnesium-lithium dual-ion battery and a preparation method thereof, which can effectively regulate the ion concentration on the negative electrode surface, thereby inhibiting the generation of magnesium dendrites, effectively promoting ion transport, and improving the ionic conductivity. 2+ To achieve the above purpose, the present invention is implemented by the following technical solutions:

[0006] To achieve the above object, the present invention is implemented by the following technical solutions:

[0007] According to the first aspect of the invention, a preparation method of a high-performance gel electrolyte for a magnesium-lithium dual-ion battery includes the following steps

[0008] Prepare a cellulose acetate fiber membrane through the electrospinning process. Immerse the cellulose acetate fiber membrane in a sodium hydroxide solution. After the immersion is completed, take it out, wash it with deionized water until neutral, and then freeze-dry it to obtain the HCA fiber membrane.

[0009] Immerse the HCA fiber membrane in a Co(NO3)2·6H2O / methanol solution for soaking time I. After taking it out, continue to immerse it in a 2-methylimidazole / methanol solution, let it stand at room temperature for standing time II. After taking it out, wash it with a methanol solvent and dry it at room temperature to obtain the ZIF-67@HCA fiber membrane.

[0010] Cut the ZIF-67@HCA fiber membrane into circular pieces and soak them in a liquid electrolyte for gelation to obtain the ZIF-67@HCA gel electrolyte (ZIF-67@HCA GPE).

[0011] Furthermore, the preparation method of the cellulose acetate fiber membrane specifically includes:

[0012] Add cellulose acetate powder to an organic solvent and stir to prepare a cellulose acetate spinning solution.

[0013] Prepare a cellulose acetate fiber membrane from the cellulose acetate spinning solution through the electrospinning process.

[0014] Furthermore, the organic solvent is an acetone / DMAC solvent, where the mass ratio of acetone to DMAC is 2:1.

[0015] Furthermore, the stirring process is to stir at 40 - 50 °C for 3 - 4 h first, and then stir at room temperature for 12 - 24 h.

[0016] Furthermore, the mass fraction of the cellulose acetate spinning solution is 13 - 14%.

[0017] Furthermore, the electrospinning process parameters are set as follows: spinning voltage 17 - 18 kV, spinning injection rate 0.9 - 1 ml / h, distance from the electrospinning needle to the receiving roller 17 - 18 cm, the inner diameter of the electrospinning needle is 0.41 mm, and the outer diameter is 0.73 mm.

[0018] Furthermore, the concentration of the sodium hydroxide solution is 0.06 mol / L, and the soaking time of the cellulose acetate fiber membrane in the sodium hydroxide solution is 2.9 - 3.2 h.

[0019] Furthermore, the molar concentration of the Co(NO3)2·6H2O / methanol solution is 1.8 - 1.9 mmol / L, the soaking time I is 3 - 5 h, the molar concentration of the 2-methylimidazole / methanol solution is 7.0 - 8.0 mmol / L, and the standing time II is 20 - 24 h.

[0020] Furthermore, the preparation method of the liquid electrolyte is as follows: Under an argon atmosphere, 0.1696 g of LiCl is added to 10 ml of 0.4 M (PhMgCl)2-AlCl3 / THF electrolyte, and stirred at room temperature for 24 h until the solid is completely dissolved.

[0021] According to the second aspect of the invention, there is also provided a high-performance gel electrolyte for a magnesium-lithium dual-ion battery, which is prepared by the preparation method described in any one of the above.

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0023] The ZIF-67@HCA gel electrolyte prepared by the present invention constructs a 3D-on-1D three-dimensional hierarchical porous structure by in-situ growing ZIF-67 particles on the surface of HCA fibers. This structure combines the three-dimensional macro-porous structure of the cellulose acetate fiber membrane prepared by the electrospinning process and the microporous structure of ZIF-67 particles, which can significantly increase the liquid absorption capacity of the liquid electrolyte, thereby promoting ion transport.

[0024] Based on the interaction between Co 2+ ions and the HCA fiber membrane, the ion pre-anchoring effect is realized, inducing the ZIF-67 particles to be closely arranged on the surface of the HCA fiber membrane, constructing an ion transport channel from MOF to MOF, which can effectively promote ion transport, improve ion conductivity, and the closely arranged ZIF-67 particles can effectively regulate the ion concentration on the surface of the negative electrode, thereby inhibiting the generation of magnesium dendrites. 2+ Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of the ZIF-67@HCA fiber membrane in the embodiment of the present invention;

[0026] Figure 2 It is a schematic SEM diagram of the ZIF-67@HCA fiber membrane in the embodiment of the present invention;

[0027] Figure 3 It is a schematic diagram of the cycle performance of the Mo6S8 / ZIF-67@HCA GPE / Mg battery in the embodiment of the present invention. Detailed Embodiments

[0028] The present invention will be further described below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be used to limit the protection scope of the present invention.

[0029] The endpoints and any values in the ranges disclosed herein are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0030] For the purposes of this specification and the appended claims, unless otherwise stated, all numbers expressing amounts, percentages or proportions and other numerical values used in this specification and the appended claims are understood to be modified in all cases by the term "about". In addition, all ranges disclosed herein include the endpoints and can be combined independently.

[0031] Example 1:

[0032] (1) Preparation of HCA fiber membrane

[0033] A certain amount of cellulose acetate (CA) powder was added to acetone / DMAC solvent (mass ratio 2:1), stirred at 50 °C for 3 h, and stirred at room temperature for 12 h to prepare a CA spinning solution (mass fraction 14%); then, a CA fiber membrane was prepared by electrospinning process.

[0034] The above electrospinning process parameters are preferably: spinning voltage 18 kV, distance from the needle to the receiving roller 18 cm, spinning injection rate 1 ml / h, inner diameter of the electrospinning needle 0.41 mm, outer diameter 0.73 mm.

[0035] Then, the CA fiber membrane was immersed in 0.06 mol / L sodium hydroxide solution for 3 h. After soaking, it was taken out, washed with deionized water until neutral, and freeze-dried to obtain the HCA fiber membrane.

[0036] (2) Preparation of ZIF-67@HCA fiber membrane

[0037] First, the HCA fiber membrane was soaked in 1.8 mmol / L Co(NO3)2·6H2O / methanol solution for 5 h. After completion, the membrane was taken out and soaked again in 7.0 mmol / L 2-methylimidazole (2-MIM) / methanol solution, and left standing at room temperature for 24 h. Finally, the membrane was taken out, washed with methanol solvent, and dried at room temperature to obtain the ZIF-67@HCA fiber membrane.

[0038] (3) Preparation of ZIF-67@HCA gel electrolyte

[0039] The ZIF-67@HCA fiber membrane was cut into circular pieces with a diameter of 19 mm, and then immersed in a liquid electrolyte for 3 h for the gelation process to prepare the ZIF-67@HCA gel electrolyte (ZIF-67@HCAGPE).

[0040] Example 2:

[0041] (1) Preparation of HCA fiber membrane

[0042] A certain amount of cellulose acetate (CA) powder was added to the acetone / DMAC solvent (mass ratio of 2:1), stirred at 40 °C for 3 h, and stirred at room temperature for 12 h to prepare a CA spinning solution (mass fraction of 13%); then, a CA fiber membrane was prepared by the electrospinning process.

[0043] The above electrospinning process parameters were preferably: spinning voltage 17 kV, distance from the needle to the receiving roller 17 cm, spinning injection rate 0.9 ml / h, inner diameter of the electrospinning needle 0.41 mm, and outer diameter 0.73 mm.

[0044] Then, the CA fiber membrane was immersed in a 0.06 mol / L sodium hydroxide solution for 3 h. After soaking, it was taken out, washed with deionized water until neutral, and freeze-dried to obtain the HCA fiber membrane.

[0045] (2) Preparation of ZIF-67@HCA fiber membrane

[0046] First, the HCA fiber membrane was soaked in a 1.9 mmol / L Co(NO3)2·6H2O / methanol solution for 3 h. After completion, the membrane was taken out and immersed again in an 8.0 mmol / L 2-methylimidazole (2-MIM) / methanol solution, and left standing at room temperature for 20 h. Finally, the membrane was taken out, washed with a methanol solvent, and dried at room temperature to obtain the ZIF-67@HCA fiber membrane.

[0047] (3) Preparation of ZIF-67@HCA gel electrolyte

[0048] The ZIF-67@HCA fiber membrane was cut into circular pieces with a diameter of 19 mm, and then immersed in a liquid electrolyte for 2 h for the gelation process to prepare the ZIF-67@HCA gel electrolyte (ZIF-67@HCAGPE).

[0049] Example 3:

[0050] (1) Preparation of HCA fiber membrane

[0051] A certain amount of cellulose acetate (CA) powder was added to acetone / DMAC solvent (mass ratio 2:1), stirred at 45 °C for 3 h, and then stirred at room temperature for 12 h to prepare a CA spinning solution (mass fraction 13.5%); then, a CA fiber membrane was prepared by electrospinning process.

[0052] The above electrospinning process parameters were preferably: spinning voltage 17 kV, distance from the needle to the receiving roller 17.5 cm, spinning injection rate 0.9 ml / h, inner diameter of the electrospinning needle 0.41 mm, and outer diameter 0.73 mm.

[0053] Then, the CA fiber membrane was immersed in 0.06 mol / L sodium hydroxide solution for 3 h. After the immersion, it was taken out, washed with deionized water until neutral, and freeze-dried to obtain the HCA fiber membrane.

[0054] (2) Preparation of ZIF-67@HCA fiber membrane

[0055] First, the HCA fiber membrane was soaked in 1.85 mmol / L Co(NO3)2·6H2O / methanol solution for 4 h. After completion, the membrane was taken out and then soaked in 7.5 mmol / L 2-methylimidazole (2-MIM) / methanol solution, and left standing at room temperature for 22 h. Finally, the membrane was taken out, washed with methanol solvent, and dried at room temperature to obtain the ZIF-67@HCA fiber membrane.

[0056] (3) Preparation of ZIF-67@HCA gel electrolyte

[0057] The ZIF-67@HCA fiber membrane was cut into circular discs with a diameter of 19 mm, and then soaked in the liquid electrolyte for 2.5 h for the gelation process to prepare the ZIF-67@HCA gel electrolyte (ZIF-67@HCA GPE).

[0058] The preparation process of the liquid electrolyte used in the above Examples 1-3 was as follows: under an argon atmosphere, 0.1696 g of LiCl was added to 10 ml of 0.4 M (PhMgCl)2-AlCl3 / THF electrolyte, and stirred at room temperature for 24 h until the solid was completely dissolved.

[0059] Next, the performance of the products obtained in the embodiments of the present invention will be analyzed in conjunction with the accompanying drawings.

[0060] As Figure 1 shown, Figure 1 the prepared ZIF-67@HCA fiber membrane was cut into circular thin slices and folded multiple times, and it can be seen that the prepared ZIF-67@HCA fiber membrane has good flexibility.

[0061] Combined with Figure 2 ,Figure 2 SEM micrograph of the as-prepared ZIF-67@HCA fiber membrane. It can be seen from the figure that ZIF-67 particles are closely arranged on the surface of the HCA fiber membrane and are evenly distributed, constructing an ion transport channel from MOF to MOF, which can effectively promote ion transport and improve ionic conductivity.

[0062] Next, the performance of the ZIF-67@HCA gel electrolytes prepared in Examples 1-3 was tested.

[0063] (1) Conductivity test: In the glove box, using a stainless steel sheet (SS) as the working electrode and reference electrode, an SS / ZIF-67@HCA GPE / SS symmetric cell was assembled, and an AC impedance test was performed on it using a Gamry 600+ electrochemical workstation. The test frequency range was 0.01 - 10 6 Hz. The conductivity value of the electrolyte was calculated according to the following formula.

[0064]

[0065] where: l - the thickness of the electrolyte (cm), σ - the conductivity (S / cm), S - the area of the stainless steel electrode (cm 2 ), R b - the bulk resistance (Ω).

[0066] The measured conductivities are shown in Table 1 below:

[0067]

[0068]

[0069] (2) Cycling performance test of lithium-ion battery: The prepared ZIF-67@HCA GPE electrolyte was assembled into a Mo6S8 / ZIF-67@HCA GPE / Mg battery. At 25 °C, the voltage test range was 0.5 - 1.8 V, and its cycling performance was tested. The test data are as Figure 3 shown.

[0070] Combining Table 1 and Figure 3 , the following conclusions can be drawn:

[0071] The ZIF-67@HCA GPE electrolyte prepared by the method of the present invention has the advantage of high conductivity. Moreover, the assembled Mo6S8 / ZIF-67@HCA GPE / Mg battery shows excellent cycling performance under the test conditions of 25 °C and 30C, indicating that the electrolyte can effectively inhibit the growth of magnesium dendrites and has good compatibility with the positive and negative electrodes, which can significantly improve the cycling performance of the MLIB battery.

[0072] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a high-performance gel electrolyte for a magnesium-lithium dual-ion battery, characterized in that: Comprising the following steps, Preparing a cellulose acetate fiber membrane by an electrospinning process, including: adding cellulose acetate powder into an organic solvent, stirring to prepare a cellulose acetate spinning solution; preparing a cellulose acetate fiber membrane from the cellulose acetate spinning solution by an electrospinning process; Immersing the cellulose acetate fiber membrane in a sodium hydroxide solution, taking it out after the immersion is completed, washing it with deionized water until neutral, and freeze-drying to obtain an HCA fiber membrane; Immersing the HCA fiber membrane in a Co(NO3)2·6H2O / methanol solution for soaking time I, taking it out and then continuing to soak it in a 2-methylimidazole / methanol solution, standing at room temperature for standing time II, taking it out and washing the surface with a methanol solvent, and drying at room temperature to obtain a ZIF-67@HCA fiber membrane; Cutting the ZIF-67@HCA fiber membrane into thin slices and soaking them in a liquid electrolyte for gelation to obtain a ZIF-67@HCA gel electrolyte.

2. The preparation method of a high-performance gel electrolyte for a magnesium-lithium dual-ion battery according to claim 1, characterized in that: The organic solvent is an acetone / DMAC solvent, wherein the mass ratio of acetone to DMAC is 2:

1.

3. The preparation method of a high-performance gel electrolyte for a magnesium-lithium dual-ion battery according to claim 1, wherein: The stirring process is to stir at 40 - 50 °C for 3 - 4 h first, and then stir at room temperature for 12 - 24 h.

4. The preparation method of a high-performance gel electrolyte for a magnesium-lithium dual-ion battery according to claim 1, characterized in that: The mass fraction of the cellulose acetate spinning solution is 13 - 14%.

5. The preparation method of a high-performance gel electrolyte for a magnesium-lithium dual-ion battery according to claim 1, characterized in that: The electrospinning process parameters are set as follows: spinning voltage 17 - 18 kV, spinning injection rate 0.9 - 1 ml / h, distance from the electrospinning needle to the receiving roller 17 - 18 cm, the inner diameter of the electrospinning needle is 0.41 mm, and the outer diameter is 0.73 mm.

6. The preparation method of a high-performance gel electrolyte for a magnesium-lithium dual-ion battery according to claim 1, characterized in that: The concentration of the sodium hydroxide solution is 0.06 mol / L, and the soaking time of the cellulose acetate fiber membrane in the sodium hydroxide solution is 2.9 - 3.2 h.

7. The preparation method of a high-performance gel electrolyte for a magnesium-lithium dual-ion battery according to claim 1, characterized in that: The molar concentration of the Co(NO3)2·6H2O / methanol solution is 1.8 - 1.9 mmol / L, the soaking time I is 3 - 5 h, the amount of substance of the 2-methylimidazole / methanol solution is 7.0 - 8.0 mmol / L, and the standing time II is 20 - 24 h.

8. The preparation method of a high-performance gel electrolyte for a magnesium-lithium dual-ion battery according to claim 1, characterized in that: The preparation method of the liquid electrolyte is: under an argon atmosphere, adding 0.1696 g of LiCl to 10 ml of 0.4 M (PhMgCl)2 - AlCl3 / THF electrolyte, stirring at room temperature for 24 h until the solid is completely dissolved.

9. A high-performance gel electrolyte for a magnesium-lithium dual-ion battery, characterized in that: Prepared by the preparation method according to any one of claims 1 - 8.

Images