Use of a gel electrolyte in rechargeable magnesium batteries

Abstract

The application discloses application of a gel electrolyte in a rechargeable magnesium battery, wherein a magnesium salt in the electrolyte is a commercially available dibenzylamine magnesium chloride lithium chloride compound, a solvent is tetrahydrofuran, a concentration is 0.5 mol / L, a ring-opening polymerized monomer is 1,3-dioxolane, and an initiator is scandium triflate. The prepared gel polymer electrolyte has excellent magnesium anode compatibility, exhibits extremely low overpotential and highly reversible magnesium deposition-dissolution behavior, maintains a coulombic efficiency of about 98% after 600 cycles, and the overpotential of a symmetrical battery almost remains unchanged after 1000 cycles, being lower than 100 mV. An anodic decomposition potential on stainless steel is 2.5 V vs. Mg / Mg 2+ The rechargeable magnesium battery gel polymer electrolyte prepared according to the application method has the advantages of simple preparation process, cheap raw materials, high magnesium deposition-dissolution efficiency, low overpotential, high safety and flexibility, and the like, and provides a feasible way for the research of solid-state rechargeable magnesium batteries.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnesium battery, and particularly relates to application of a gel electrolyte in a rechargeable magnesium battery. BACKGROUND

[0002] Magnesium is located on the diagonal line with lithium in the periodic table, and has similar ionic radius and chemical properties. Due to the characteristics of divalent ions of Mg 2+ , Mg has a high theoretical capacity (3833 mAh cm –3 ); in addition, magnesium is abundant in nature and has low cost, and has potential for sustainable development. Magnesium is stable in air and has few dendrites, which makes it have good safety characteristics. Therefore, rechargeable magnesium batteries have become a strong competitor for the next generation of energy storage systems. The electrolyte is a key factor affecting the development of rechargeable magnesium batteries, and the development of electrolyte systems with strong oxidation stability, high conductivity, high magnesium reversible deposition-dissolution efficiency, excellent cycle performance and low cost is crucial for promoting the development of high-performance rechargeable magnesium batteries.

[0003] The feasibility of rechargeable magnesium batteries was first proposed by Gregory et al. in 1990 (Gregory T D, Hoffman RJ, Winterton, Development of an ambient secondary magnesium battery, J. Electrochem. Soc., 1990, 137: 775-780). In 2000, Aurbach et al. made a major breakthrough in the field of rechargeable magnesium batteries (Aurbach D, Lu Z, Schechter A, et al. Prototype systems for rechargeable magnesium batteries. Nature, 2000, 407: 724-727). Subsequently, a large number of researchers have devoted themselves to the research of rechargeable magnesium battery electrolyte and have made significant progress.

[0004] Firstly, magnesium salts based on Grignard reagent are widely used due to their highly reversible magnesium deposition-dissolution performance. However, Grignard reagent gradually loses its favor due to its low oxidation stability, high corrosiveness and nucleophilicity. In order to further enhance the oxidation stability window and the reversibility of magnesium deposition-dissolution, electrolytes based on bis(hexamethyldisilazane) magnesium, magnesium borohydride and halide-containing mixed salts (such as magnesium aluminum chloride complex and magnesium lithium chloride complex) are gradually developed, and their oxidation stability can reach 3 V vs. Mg / Mg 2+ The above has a magnesium deposition-dissolution efficiency of up to 99%, and their non-nucleophilicity broadens the positive electrode compatibility.

[0005] Secondly, the development of electrolytes with bulky weakly coordinating anions, such as magnesium tetra (hexafluoroisopropyl) borate and carborane cluster magnesium salts, further expanded the oxidative stability of electrolytes (>4 V vs. Mg / Mg 2+ ). Their properties, including highly reversible magnesium deposition-stripping efficiency, non-corrosive, and wide positive compatibility, greatly promoted the development of rechargeable magnesium battery liquid electrolytes.

[0006] Thirdly, the incorporation of beneficial additives has been shown to change the solvation structure of electrolytes, making the utilization of passivation salts in rechargeable magnesium batteries possible. For example, magnesium bis (trifluoromethanesulfonimide) can be used with magnesium chloride or ionic liquids, thereby mitigating the passivation of the metal magnesium negative electrode.

[0007] In addition, by introducing chelating agents, the overpotential of magnesium bis (trifluoromethanesulfonimide) and magnesium triflate electrolyte is greatly reduced, making the magnesium deposition-stripping reversibility significantly enhanced.

[0008] Although important progress has been made in liquid electrolytes for rechargeable magnesium batteries, their inherent shortcomings remain a concern. The presence of soluble impurities in liquid electrolytes increases the likelihood of side reactions, thereby compromising the stability of the positive and negative electrodes, ultimately leading to the deterioration of the battery's electrochemical performance. In addition, liquid electrolytes also have the risk of leakage, volatilization and flammability, which will pose serious safety hazards in practical applications. In response to these challenges, gel polymer electrolytes have been proposed as a means to improve the overall performance of the battery. By dispersing magnesium salts in a flexible polymer matrix, this electrolyte has significant advantages, including higher thermal and mechanical stability, excellent structural flexibility, higher safety, wider working temperature range, and less tendency for side reactions. In addition, in-situ gel electrolytes also exhibit good interface contact, high room temperature ionic conductivity, low interface impedance and excellent positive and negative compatibility. Based on these improvements in comprehensive performance, gel polymer electrolytes are expected to be a promising direction in future practical applications. SUMMARY

[0009] To achieve the above-mentioned purpose, the present application provides a gel electrolyte for use in a rechargeable magnesium battery, the gel electrolyte comprising a magnesium salt, a ring-opening polymerization monomer, a solvent and an initiator, the ring-opening polymerization monomer being 1,3-dioxolane. Generally speaking, 1,3-dioxolane monomer has good compatibility with lithium metal, but has a passivation effect on the metal magnesium negative electrode, and the passivation effect on the metal magnesium will be weakened after ring-opening polymerization of the monomer. At the same time, the magnesium salt contains chloride, which can further alleviate the passivation phenomenon of the magnesium negative electrode, thereby improving the compatibility of the gel electrolyte with the magnesium negative electrode.

[0010] In some embodiments, the magnesium salt is a dibenzylamine magnesium chloride lithium chloride complex or other magnesium chloride lithium chloride complex.

[0011] In some embodiments, the solvent is tetrahydrofuran.

[0012] In some embodiments, the initiator is scandium triflate, preferably, the mass fraction of the initiator relative to 1,3-dioxolane is 3-4wt%.

[0013] In some embodiments, the magnesium salt is dissolved in a tetrahydrofuran solvent to form a magnesium salt / tetrahydrofuran electrolyte, and the concentration of magnesium ions in the magnesium salt / tetrahydrofuran is 0.5mol / L.

[0014] In some embodiments, the volume ratio of the magnesium salt / tetrahydrofuran electrolyte to the ring-opening polymerization monomer can be adjusted, preferably, the volume ratio of the magnesium salt / tetrahydrofuran electrolyte to the ring-opening polymerization monomer is 3:1.

[0015] In some embodiments, aluminum chloride can be added to the magnesium salt / tetrahydrofuran electrolyte and reacted for 24 hours to improve the activity and oxidation stability of the electrolyte. The amount of aluminum chloride is 1-2 times the concentration of magnesium ions, i.e., the molar ratio of aluminum ions to magnesium ions is 1:1-2:1.

[0016] In some embodiments, the gel electrolyte is prepared by the following method:

[0017] Step 1), adding an initiator to a ring-opening polymerization monomer and mixing at 40°C for 8-9 minutes to obtain solution A;

[0018] Step 2), adding the magnesium salt / tetrahydrofuran electrolyte to solution A and stirring vigorously (stirring speed is about 1000r / min) at room temperature until a homogeneous solution is obtained to obtain precursor solution B;

[0019] Step 3), placing the precursor solution B at room temperature for more than 24 hours to obtain a transparent gel-state electrolyte.

[0020] In preferred embodiments, the above operations are all carried out in a glove box filled with argon atmosphere (water content <0.01ppm, oxygen content <0.01ppm).

[0021] In some embodiments, the rechargeable magnesium battery is prepared by the following method:

[0022] A 2032 type 316 stainless steel battery shell, metallic magnesium, and exfoliated Mo6S8 are used as the positive electrode, the precursor solution B is added, metallic magnesium is used as the negative electrode, and a polyethylene film is used as the separator to assemble a button cell, which is placed for more than 24 hours.

[0023] In some embodiments, the rechargeable magnesium battery (full battery) has an average discharge specific capacity of 95.6 mAh / g at a rate of 0.5C at room temperature, the discharge specific capacity is maintained above 92 mAh / g after 600 charge-discharge cycles, the capacity retention rate is above 88%, and the coulombic efficiency is maintained at 100%.

[0024] The rechargeable magnesium battery gel polymer electrolyte in the application adopts 0.5 mol / L of a dibenzylamine magnesium chloride lithium chloride compound or other lithium chloride magnesium chloride compound as an active magnesium salt, initiates 1,3-dioxolane ring-opening polymerization through a Lewis acid, and the in-situ formed gel electrolyte has good magnesium anode compatibility, the magnesium deposition-dissolution efficiency after stabilization is about 98%, and the overpotential is lower than 100 mV. The anodic oxidation decomposition potential of the gel electrolyte on stainless steel can reach 2.5 V vs. Mg / Mg 2+ The above. The gel polymer electrolyte prepared by in-situ ring-opening polymerization has the advantages of simple preparation process, cheap raw materials, excellent electrochemical performance, flexible structure, good mechanical stability, etc.

[0025] Technical effects

[0026] The rechargeable magnesium battery gel polymer electrolyte provided by the application has the advantages of high magnesium deposition-dissolution efficiency, low overpotential, good positive electrode matching, high safety and flexibility, etc. The possibility of side reactions is reduced, thereby improving the stability of the positive and negative electrodes, and finally promoting the significant improvement of the electrochemical performance of the full battery; the electrolyte almost has no risk of leakage, volatilization, etc., and will not cause serious safety hazards in actual application. The obtained rechargeable magnesium battery has excellent performance, and provides a feasible way for the practicalization of solid-state rechargeable magnesium batteries.

[0027] The application discloses application of a simple ring-opening polymerization gel electrolyte in a rechargeable magnesium battery. The magnesium salt in the electrolyte is a commercially available dibenzylamine magnesium chloride lithium chloride compound or other lithium chloride magnesium chloride compound, the solvent is tetrahydrofuran, the concentration is 0.5 mol / L, the ring-opening polymerization monomer is 1,3-dioxolane, and the initiator is scandium triflate. The prepared gel polymer electrolyte has excellent magnesium anode compatibility, exhibits extremely low overpotential and highly reversible magnesium deposition-dissolution behavior, maintains a coulombic efficiency of about 98% after 600 cycles, the overpotential of the symmetrical battery almost remains unchanged after 1000 cycles, and is lower than 100 mV. The anodic oxidation decomposition potential on stainless steel is 2.5 V vs. Mg / Mg 2+ The above. In addition, the electrolyte is modified by adding aluminum chloride, and the obtained gel electrolyte has good matching with a Mo6S8 positive electrode, has an average discharge specific capacity of 95.6 mAh / g after 600 cycles at a rate of 0.5C, the capacity retention rate is above 88%, and the coulombic efficiency is close to 100%. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a digital photograph of the gel polymer electrolyte obtained after ring opening polymerization of the dibenzylamine based magnesium chloride lithium chloride complex / tetrahydrofuran + 1,3-dioxolane + initiator obtained in Example 1;

[0029] Figure 2 is the magnesium deposition-dissolution efficiency of the gel polymer electrolyte obtained in Example 2 on stainless steel, the inset is the corresponding partial magnesium deposition-dissolution curve (first ten cycles);

[0030] Figure 3 is the charge-discharge curve of the magnesium vs. magnesium symmetric cell of the gel polymer electrolyte obtained in Example 3, the inset is the corresponding partially enlarged charge-discharge curve;

[0031] Figure 4 is the cyclic voltammogram of the gel polymer electrolyte obtained in Example 4 on stainless steel;

[0032] Figure 5 is the linear sweep voltammogram of the gel polymer electrolyte obtained in Example 5 on stainless steel;

[0033] Figure 6 is the magnesium deposition-dissolution efficiency of the gel electrolyte obtained after ring opening polymerization of the dibenzylamine based magnesium chloride lithium chloride complex + aluminum trichloride (molar ratio 1:2) / tetrahydrofuran + 1,3-dioxolane + initiator obtained in Example 6 on stainless steel, the inset is the corresponding partial magnesium deposition-dissolution curve (first ten cycles);

[0034] Figure 7 is the charge-discharge cycling performance of the full cell obtained in Example 7 at 0.5C rate;

[0035] Figure 8 is a digital photograph of the 0.5 mol / L dibenzylamine based magnesium chloride lithium chloride complex / tetrahydrofuran liquid electrolyte obtained in Comparative Example 1;

[0036] Figure 9 is the magnesium deposition-dissolution efficiency of the 0.5 mol / L dibenzylamine based magnesium chloride lithium chloride complex / tetrahydrofuran liquid electrolyte obtained in Comparative Example 2 on stainless steel, the inset is the corresponding partial magnesium deposition-dissolution curve (first ten cycles);

[0037] Figure 10 is the cyclic voltammogram of the 0.5 mol / L dibenzylamine based magnesium chloride lithium chloride complex / tetrahydrofuran liquid electrolyte obtained in Comparative Example 3 on stainless steel;

[0038] Figure 11Magnesium deposition-dissolution efficiency of 0.5 mol / L dibenzylamine magnesium chloride lithium chloride complex / lithium chloride / tetrahydrofuran + aluminum chloride (molar ratio 1:2) liquid electrolyte obtained from Comparative Example 4 on stainless steel, and the corresponding partial magnesium deposition-dissolution curve (first ten cycles) is shown in the inset. DETAILED DESCRIPTION

[0039] The technical content of the present application will be more clearly understood and facilitated to be understood through the following description of the drawings accompanying the specification, which introduces a plurality of preferred embodiments of the present application. The present application can be embodied in many different forms of embodiments, and the protection scope of the present application is not limited to the embodiments mentioned herein.

[0040] Example 1

[0041] A certain amount of 1,3-dioxolane was pipetted, and then 3-4 wt% scandium triflate relative to the mass of 1,3-dioxolane was weighed and added thereto, and the mixture was stirred at 40°C for 8-9 minutes to obtain solution A.

[0042] Subsequently, 3 times the volume of dibenzylamine magnesium chloride lithium chloride complex / tetrahydrofuran electrolyte was pipetted according to the amount of 1,3-dioxolane and added to solution A (i.e. the volume ratio of 1,3-dioxolane to dibenzylamine magnesium chloride lithium chloride complex / tetrahydrofuran electrolyte was 1:3), and the mixture was stirred at room temperature (stirring speed was about 1000 r / min) until a homogeneous solution was obtained, to obtain precursor solution B.

[0043] The precursor solution B was allowed to stand at room temperature for 24 hours to obtain a gel-state polymer electrolyte.

[0044] The above operations were all carried out in a glove box filled with argon atmosphere (water content <0.01 ppm, oxygen content <0.01 ppm).

[0045] Figure 1 As can be seen from the digital photograph of the precursor solution B after standing at room temperature for 24 hours, the obtained gel electrolyte was in a red-brown transparent state, and had no flowability, and even if the black cover bottle was inverted, the electrolyte still remained at the bottom of the bottle and did not flow down.

[0046] Example 2

[0047] The precursor solution B was prepared according to Example 1, a 2032 type 316 stainless steel battery shell was used as the positive electrode, a certain amount of the precursor solution B was added, metallic magnesium was used as the negative electrode, and a polyethylene film was used as the separator, to assemble a button cell, and magnesium deposition-dissolution performance test was carried out.

[0048] The above operations were all carried out in a glove box filled with argon atmosphere (water content <0.01 ppm, oxygen content <0.01 ppm).

[0049] Subsequently, the button cell batteries were left to stand for 24 hours, followed by charge-discharge cycles at a current of 0.1 mA·cm⁻¹. -2 Discharge for 30 minutes, charging cut-off voltage is 1.0V. Magnesium deposition-dissolution efficiency is as follows: Figure 2 As shown in the figure, the inset plot shows the corresponding deposition-dissolution curve. The deposition-dissolution overpotential of the obtained gel electrolyte on stainless steel is approximately 0.1 V. An activation process occurs in the early stage of cycling, and the magnesium deposition-dissolution efficiency gradually increases from 70% to eventually stabilize at around 98.5%. After 600 cycles, the average coulombic efficiency is approximately 98%, demonstrating good cycling stability.

[0050] Example 3

[0051] According to Example 1, precursor solution B was prepared, and magnesium metal was used as the positive electrode. A certain amount of precursor solution B was added, magnesium metal was used as the negative electrode, and polyethylene membrane was used as the separator to assemble a symmetrical coin cell.

[0052] All the above operations were carried out in a glove box filled with argon atmosphere (water content <0.01ppm, oxygen content <0.01ppm).

[0053] Subsequently, the symmetrical button cells were left to stand for 24 hours, followed by charge-discharge cycles at a current of 0.1 mA·cm⁻¹. -2 The charge and discharge times are both 30 minutes. The charge and discharge curves of the symmetrical battery are as follows: Figure 3 As shown, the overpotential was approximately 0.12V in the early stage of cycling, while after 1200 hours of charge-discharge cycling, the overpotential was approximately 0.1V. This may be attributed to the brief activation process in the early stage. Overall, after 1500 hours of charge-discharge cycling, the overpotential of the assembled symmetrical battery did not show a significant increase, remaining at around 0.1V, which fully demonstrates the good magnesium anode compatibility and excellent cycling stability of the gel electrolyte.

[0054] Example 4

[0055] According to Example 1, precursor solution B was prepared. A 2032 type 316 stainless steel battery case was used as the positive electrode. A certain amount of precursor solution was added, magnesium metal was used as the negative electrode, and polyethylene film was used as the separator. The battery was assembled into a button cell and then left to stand for 24 hours.

[0056] All the above operations were carried out in a glove box filled with argon atmosphere (water content <0.01ppm, oxygen content <0.01ppm).

[0057] Subsequently, the assembled button cell was subjected to cyclic voltammetry testing outside the glove box at a scan rate of 1 mV / s. -1 The voltage range is -1 to 2V. The cyclic voltammetry test results are as follows: Figure 4As shown, it can be seen that at -0.26V vs. Mg / Mg 2+ Magnesium deposition begins at 0.6V vs. Mg / Mg 2+ The oxidation peaks appearing on the left and right correspond to the dissolution of magnesium, with a peak current density of approximately 2.0 mA / cm². -2 Compared to the liquid electrolyte in Comparative Example 1, the magnesium deposition-dissolution process exhibits lower polarization, primarily due to the formation of a more stable solid electrolyte interphase (SEI) layer. However, the resulting gel electrolyte displays a lower peak current value, likely due to its lower conductivity compared to the liquid electrolyte.

[0058] Example 5

[0059] According to Example 1, precursor solution B was prepared. A 2032 type 316 stainless steel battery case was used as the positive electrode. A certain amount of precursor solution was added, magnesium metal was used as the negative electrode, and polyethylene film was used as the separator. The battery was assembled into a button cell and then left to stand for 24 hours.

[0060] All the above operations were carried out in a glove box filled with argon atmosphere (water content <0.01ppm, oxygen content <0.01ppm).

[0061] Subsequently, the assembled battery was subjected to a linear voltammetric scan outside the glove box at a scan rate of 5 mV / s. -1 The linear voltammetric scan results are as follows: Figure 5 As shown, the anodic oxidation potential of the obtained gel electrolyte on stainless steel reaches 2.5V vs. Mg / Mg. 2+ above.

[0062] Example 6

[0063] A certain amount of aluminum trichloride was weighed and slowly added to tetrahydrofuran. The mixture was stirred thoroughly in a magnetic stirrer to dissolve the aluminum trichloride, preparing a 1.0 mol / L aluminum trichloride solution. Then, a 1.0 mol / L dibenzylaminomagnesium chloride-lithium chloride complex electrolyte was slowly added dropwise, and stirring continued for 24 hours to obtain a dibenzylaminomagnesium chloride-lithium chloride complex + aluminum trichloride (molar ratio 1:2) / tetrahydrofuran electrolyte with a magnesium ion concentration of 0.5 mol / L. All the above operations were carried out in a glove box filled with argon atmosphere (water content <0.01 ppm, oxygen content <0.01 ppm).

[0064] A certain amount of 1,3-dioxolane was taken in a pipette, then 3-4wt% scandium triflate was weighed relative to the mass of 1,3-dioxolane and added, and mixed and stirred at 40°C for 8-9 minutes to obtain solution A. Subsequently, 3 times the volume of 0.5mol / L dibenzylamine magnesium chloride lithium chloride complex + aluminum chloride (molar ratio 1:2) / tetrahydrofuran electrolyte was taken in a pipette according to the amount of 1,3-dioxolane and added to solution A (i.e. the volume ratio of 1,3-dioxolane to dibenzylamine magnesium chloride lithium chloride complex + aluminum chloride / tetrahydrofuran electrolyte is 1:3), and stirred vigorously (stirring speed is about 1000r / min) at room temperature until a homogeneous solution is obtained, to obtain precursor solution B.

[0065] A 2032 type 316 stainless steel battery shell was used as the positive electrode, a certain amount of the above precursor solution B was added, magnesium metal was used as the negative electrode, and a polyethylene film was used as the separator to assemble a button cell. The above operations were all carried out in a glove box filled with argon atmosphere (water content <0.01ppm, oxygen content <0.01ppm).

[0066] After the assembled battery was left to stand for 24 hours, magnesium deposition-dissolution testing was carried out, the discharge time was 30 minutes, the charging cutoff voltage was 1.0V, and the current density was 0.1mAcm -1 , the results are shown in Figure 6 , the initial coulombic efficiency was 86%, the stable magnesium deposition-dissolution efficiency reached more than 98%, the average coulombic efficiency after 160 cycles was as high as 97.8%, and the dissolution overpotential was less than 60mV.

[0067] Example 7

[0068] According to the preparation of precursor solution C in Example 6, a delithiated Mo6S8 material was used as the positive electrode, a certain amount of precursor solution C was added, magnesium metal was used as the negative electrode, and a polyethylene film was used as the separator to assemble a button cell, which was then left to stand for 24 hours.

[0069] The above operations were all carried out in a glove box filled with argon atmosphere (water content <0.01ppm, oxygen content <0.01ppm).

[0070] Subsequently, the assembled full cell was subjected to charge-discharge cycle testing in an electrochemical test system, the cycle rate used was 0.5C, the charging cutoff voltage was 2V, and the discharge cutoff voltage was 0.2V. The results are shown in Figure 7 , the initial discharge specific capacity of the obtained full cell was 104mAh / g, the discharge specific capacity remained above 92mAh / g after 600 cycles, the capacity retention rate reached more than 88%, and the coulombic efficiency remained at 100%. This indicates that the obtained gel electrolyte has good positive electrode compatibility and also exhibits excellent cycle stability in the full cell.

[0071] Comparative Example 1

[0072] A certain amount of 1 mol / L dibenzylamine-based magnesium chloride lithium chloride complex / tetrahydrofuran electrolyte was taken with a pipette, and an equal volume of tetrahydrofuran solvent was added. The mixture was stirred on a magnetic stirrer for 8 hours to obtain 0.5 mol / L dibenzylamine-based magnesium chloride lithium chloride complex / tetrahydrofuran liquid electrolyte. The above operations were all carried out in a glove box filled with argon atmosphere (water content <0.01 ppm, oxygen content <0.01 ppm). Figure 8 A digital photo of the liquid electrolyte is shown. In sharp contrast to Example 1, when the black cap bottle was inverted, the liquid electrolyte did not stay at the bottom of the bottle, but flowed to the end of the bottle cap under the action of gravity.

[0073] Comparative Example 2

[0074] A 0.5 mol / L dibenzylamine-based magnesium chloride lithium chloride complex / tetrahydrofuran liquid electrolyte was prepared according to Comparative Example 1. Then a 2032 type 316 stainless steel battery shell was used as the positive electrode, a certain amount of the above liquid electrolyte was added, a magnesium metal was used as the negative electrode, and a polyethylene film was used as the separator to assemble a button cell. The above operations were all carried out in a glove box filled with argon atmosphere (water content <0.01 ppm, oxygen content <0.01 ppm).

[0075] After standing for 4 hours, magnesium deposition-dissolution tests were carried out on an electrochemical test system, the discharge time was 30 minutes, the charge cutoff voltage was 1.0 V, and the current density was 0.1 mA cm -1 . The results are shown in Figure 9 , the initial coulombic efficiency was 68.8%, the efficiency after 5 cycles was 92%, the average efficiency of magnesium deposition-dissolution after 1000 cycles was 98.3%, and the overpotential was about 100 mV.

[0076] Comparative Example 3

[0077] A 0.5 mol / L dibenzylamine-based magnesium chloride lithium chloride complex / tetrahydrofuran liquid electrolyte was prepared according to Comparative Example 1. Then a 2032 type 316 stainless steel battery shell was used as the positive electrode, a certain amount of the above liquid electrolyte was added, a magnesium metal was used as the negative electrode, and a polyethylene film was used as the separator to assemble a button cell. The above operations were all carried out in a glove box filled with argon atmosphere (water content <0.01 ppm, oxygen content <0.01 ppm).

[0078] After standing for 4 hours, cyclic voltammetry tests were carried out, the scanning speed was 1 mV s -1 , and the voltage range was -1-2 V. The results of the cyclic voltammetry tests are shown in Figure 10 . It can be seen that the reduction peak potential was -0.26 V vs. Mg / Mg 2+The magnesium deposition started to occur at 0.87 V vs. Mg / Mg 2+ The oxidation peaks on the right correspond to the dissolution of magnesium, with a peak current density of about 6.0 mA cm -2 Compared with the gel electrolyte, the polarization during the magnesium deposition-dissolution process is greater, but the corresponding peak current value is also greater, mainly due to the inherent advantage of the liquid electrolyte in terms of conductivity.

[0079] Comparative Example 4

[0080] A certain amount of aluminum chloride was slowly added to tetrahydrofuran, and was fully stirred and dissolved in a magnetic stirrer to prepare a 1.0 mol / L aluminum chloride solution. Then, 1.0 mol / L dibenzylamine-based magnesium chloride lithium chloride complex electrolyte was slowly added in proportion, and stirring was continued for 24 hours to obtain a dibenzylamine-based magnesium chloride lithium chloride complex + aluminum chloride (molar ratio 1:2) / tetrahydrofuran electrolyte with a magnesium ion concentration of 0.5 mol / L.

[0081] A 2032 type 316 stainless steel battery shell was used as the positive electrode, a certain amount of the above electrolyte was added, magnesium metal was used as the negative electrode, and a polyethylene film was used as the separator to assemble a button cell. The above operations were all carried out in a glove box filled with argon gas atmosphere (water content <0.01 ppm, oxygen content <0.01 ppm).

[0082] After standing for 4 hours, magnesium deposition-dissolution test was carried out, the discharge time was 30 minutes, the charge cutoff voltage was 1.0 V, and the current density was 0.1 mA cm -1 , the results are shown in Figure 11 , the initial coulombic efficiency was 88.4%, the average efficiency of magnesium deposition-dissolution after 350 cycles was 98.9%, and the overpotential was about 90 mV.

[0083] The above describes the preferred embodiments of the present application in detail. It should be understood that those skilled in the art can make many modifications and changes without creative labor based on the concept of the present application. Therefore, any technical solution obtained by logical analysis, reasoning or limited experiment based on the prior art according to the concept of the present application shall be within the protection scope determined by the claims.

Claims

1. The application of a gel electrolyte in a rechargeable magnesium battery, the gel electrolyte comprising a magnesium salt, a ring-opening polymerizable monomer, a solvent, and an initiator, wherein the ring-opening polymerizable monomer is 1,3-dioxolane; the magnesium salt is a dibenzylaminomagnesium chloride-lithium chloride complex; and the initiator is scandium trifluoromethanesulfonate. The gel electrolyte is prepared by the following method: Step 1), the initiator is added to the ring-opening polymerization monomer, and the mixture is mixed at 40°C for 8-9 minutes to obtain solution A; Step 2), add magnesium salt / tetrahydrofuran electrolyte to solution A and stir vigorously at room temperature until homogeneous, which is the precursor solution B; Step 3), the precursor solution B is left to stand at room temperature for more than 24 hours to obtain a transparent gel electrolyte; The rechargeable magnesium battery is prepared by the following method: A coin cell battery is assembled using a 316 stainless steel battery casing of type 2032, magnesium metal, and intercalation-deintercalation type Mo6S8 as the positive electrode, with the aforementioned precursor solution B added, magnesium metal as the negative electrode, and polyethylene membrane as the separator. The battery is then left to stand for more than 24 hours. The rechargeable magnesium battery has an average discharge specific capacity of 95.6 mAh / g at a 0.5 C rate after 600 charge-discharge cycles, and the discharge specific capacity remains above 92 mAh / g, with a capacity retention rate of over 88%.

2. The application according to claim 1, wherein, The solvent is tetrahydrofuran.

3. The application according to claim 1, wherein, The initiator has a mass fraction of 3-4 wt% relative to 1,3-dioxolane.

4. The application according to claim 1, wherein, The magnesium ion concentration in the magnesium salt / tetrahydrofuran electrolyte is 0.5 mol / L.

5. The application according to claim 1, wherein, The volume ratio of the magnesium salt / tetrahydrofuran electrolyte to the ring-opening polymer monomer is 3:

1.

6. The application according to claim 1, wherein, The method further includes first adding aluminum trichloride to the magnesium salt / tetrahydrofuran electrolyte and reacting for 24 h.

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