A magnesium battery rare earth chloride electrolyte and a preparation method and use method thereof

Abstract

The application provides a magnesium battery rare earth chloride electrolyte and a preparation method and use method thereof, and belongs to the technical field of magnesium air battery electrolytes, and the electrolyte components include 0.45-0.65M of sodium chloride, 0.4-0.6M of yttrium chloride and 0.4-0.6M of gadolinium chloride in terms of molar fraction; the pH of the electrolyte is 7±0.2. The magnesium battery rare earth chloride electrolyte and the preparation method and use method thereof can solve the problems that the current Mg-0.2Ca anode material has high electrochemical activity and is prone to corrosion, the anode utilization efficiency is low, and insoluble Mg(OH)2 is prone to being deposited on the surface of the anode in the discharging process and reducing the discharging voltage, and the preparation and use are economic and efficient and environment-friendly.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnesium air battery electrolyte, in particular to a rare earth chloride electrolyte for magnesium battery and a preparation method and use method thereof. BACKGROUND

[0002] Currently, fossil energy is increasingly depleted, which has become a serious challenge facing the world. Among various types of air batteries, magnesium air batteries have attracted widespread attention due to their unique advantages. The energy conversion nature of magnesium air batteries is to utilize the spontaneous redox reaction of magnesium oxidation and oxygen reduction. The chemical energy released in the reaction forces electrons to flow from the negative electrode (Mg) to the positive electrode (O2) through the external circuit, thereby generating available current (electric energy). The ion migration in the electrolyte ensures the internal charge balance of the battery, so that the reaction can continue. Finally, the chemical energy (stored in Mg and O2) is efficiently converted into electric energy (to drive external loads) and chemical energy (stored in the reaction product Mg(OH)2).

[0003] Although lithium air batteries have the ability to be charged and discharged, due to the more active chemical properties of lithium than magnesium, lithium air batteries need to work in a glove box. If the lithium air battery is directly placed in the air, lithium is prone to spontaneous combustion, and also prone to spontaneous combustion in a high-temperature environment. Moreover, the reaction of lithium with water is more violent, not only exists a great safety hazard, but also the price of lithium resources is expensive, and the theoretical specific capacity is relatively low. Although zinc air batteries have good safety and low cost advantages, due to the weak activity of zinc metal, it is difficult to achieve high voltage output. In the discharge process of aluminum air battery, a stable passivation film is formed on the surface of the aluminum electrode, which inhibits the continuous discharge reaction, resulting in the increase of electrode potential, thereby gradually reducing the output voltage and power.

[0004] In contrast, magnesium air batteries have more outstanding performance advantages. Magnesium metal has high electronegativity and high chemical activity, high theoretical specific capacity and voltage, and is easy to process and relatively safe to use, so it has become a research hotspot in recent years.

[0005] Magnesium air batteries have broad application prospects and can be used in submarine power systems, long-range communication equipment, and field emergency power supply fields.

[0006] However, there are some problems in the practical use of magnesium-air batteries. During the discharge process, the continuous contact of the magnesium anode with the electrolyte can trigger a side reaction with hydrogen ions in the electrolyte, producing hydrogen gas and insoluble discharge products such as magnesium hydroxide (Mg(OH)2), which can deposit on the surface of the anode, hindering the contact between the anode and the electrolyte, affecting the stability of the battery output voltage and power. Moreover, excessive cathode hydrogen evolution reaction can also exacerbate magnesium corrosion, causing some magnesium that has not participated in the discharge reaction to be encapsulated and shed, reducing the utilization rate of the anode material and specific capacity, and shortening the service life of the battery.

[0007] To improve the discharge performance of magnesium-air batteries, there are currently two main technical paths: one is to optimize the anode material, and the other is to adjust the chemical composition of the electrolyte. In terms of optimizing the anode material, alloying or heat treatment processes are often used. For example, by introducing elements such as calcium, the negative effects of impurity elements (such as iron and manganese) on the magnesium matrix can be reduced, and the potential difference between the second phase and the matrix can be reduced, thereby improving corrosion resistance; heat treatment processes such as low-temperature tempering can improve the alloy microstructure, promote uniform dissolution of the anode, and improve discharge stability. However, such methods usually require expensive processing equipment and longer processing cycles, have low cost-effectiveness, and have limited improvement in discharge performance.

[0008] Adjusting the electrolyte composition is a more efficient, economical and environmentally friendly strategy. By optimizing the chemical composition of the electrolyte, the side reactions can be effectively suppressed, and the generation of insoluble products can be reduced, thereby significantly improving the discharge voltage, anode utilization efficiency and overall performance of the battery. Therefore, optimizing the chemical composition and ratio of the electrolyte is of great significance for promoting the application of magnesium-air batteries. However, the current research on electrolytes is still in its early stages, and there are still many deficiencies in the developed electrolytes.

[0009] For example, the patent with application number CN202410882642.2 proposes a mixed solution of disodium hydrogen phosphate and sodium acetate as the electrolyte for magnesium-air batteries, which shows the discharge voltage under three current densities. The anode exhibits the highest discharge voltage in 0.005M / L sodium acetate and 0.5M / L sodium acetate, but the anode discharge voltage is not stable, and the initial discharge process shows a very obvious voltage drop, which cannot provide stable output power. At the same time, when the anode current density increases to 10mA cm -2 , the electrolyte has weak effect on the output voltage of the magnesium anode, and the average discharge voltage of the anode is less than 1.3V, indicating that the electrolyte is not suitable for use under high current density.

[0010] For example, the patent with application number CN202211577325.7 proposes an ionic liquid electrolyte synthesized from 0.1 mol of choline hydroxide, 0.1 mol of glycolic acid, and 0.1 M salicylic acid to improve the performance of magnesium-air batteries. This method can increase the voltage of magnesium alloys because the salicylic acid in the ionic liquid can complex with Mg 2+ and improve electrochemical activity. However, synthesizing ionic liquids requires stirring the reaction at room temperature for 12-24 hours, and after the reaction is complete, complex processes such as rotary evaporation and drying are required, making the overall process complex and costly. On the other hand, ionic liquids can reduce ion transfer rates and affect discharge voltage. At a current density of 5 mA cm -2 , the average discharge voltage of the anode in an electrolyte containing 0.1 M salicylic acid choline is only 1.368 V.

[0011] Therefore, there is an urgent need for an economical, efficient, and environmentally friendly electrolyte and its preparation method to effectively solve the problems of high electrochemical activity of Mg-0.2Ca anode materials, easy corrosion, low anode utilization efficiency, and the deposition of insoluble Mg(OH)2 on the anode surface during the electrolysis process, which reduces the discharge voltage. SUMMARY

[0012] The technical problem to be solved by the present application is to provide an economical, efficient, and environmentally friendly rare earth chloride electrolyte for magnesium batteries and its preparation method and use method to solve the problems of high electrochemical activity of Mg-0.2Ca anode materials, easy corrosion, low anode utilization efficiency, and the deposition of insoluble Mg(OH)2 on the anode surface during the discharge process, which reduces the discharge voltage.

[0013] To solve the above technical problems, the present application provides a rare earth chloride electrolyte for magnesium batteries, which comprises, by mole fraction, 0.45-0.65 M sodium chloride, 0.4-0.6 M yttrium chloride, and 0.4-0.6 M gadolinium chloride.

[0014] The pH of the electrolyte is 7±0.2.

[0015] The present application also provides a preparation method for a rare earth chloride electrolyte for magnesium batteries, comprising the following steps:

[0016] Mix the required amounts of sodium chloride, yttrium chloride, and gadolinium chloride uniformly to obtain a mixture;

[0017] Add the mixture to deionized water and heat and stir until a transparent solution is obtained;

[0018] Add dilute hydrochloric acid or sodium hydroxide to the transparent solution to adjust the pH of the solution to 7.0±0.2 to obtain the electrolyte.

[0019] Further, the stirring speed is controlled at 200-300 rpm / min.

[0020] Further, the heating temperature is 50±5℃.

[0021] Further, the pH value of the transparent solution is detected by a pH-conductivity meter.

[0022] The application also provides a method for using the rare earth chloride electrolyte of the magnesium battery, comprising the following steps:

[0023] applying an external current in an electrochemical workstation;

[0024] collecting the voltage change signal of the battery;

[0025] inserting the magnesium anode and the air cathode into the electrolyte for electrolysis.

[0026] Further, the current density applied by the electrochemical workstation is 2.5-10 mA·cm -2 .

[0027] Further, the magnesium anode is a Mg-0.2Ca anode, the magnesium content is ≥99.9 wt.%, the calcium content is ≥0.2 wt.%, the tin content is 0.01-0.012 wt.%, and the manganese impurity content is ≤0.01 wt.%.

[0028] Further, 10-15% of the surface area of the magnesium anode is exposed to the surface of the electrolyte.

[0029] Further, the air cathode is prepared by pressing and shearing the material including copper mesh, graphite powder and foil under a pressure of 450-550 Mpa.

[0030] The rare earth chloride electrolyte of the magnesium battery provided by the application takes sodium chloride, yttrium chloride and gadolinium chloride as the components of the electrolyte. sp The K sp of Y(OH)3 and Gd(OH)3 is less than that of Mg(OH)2, i.e. sp Y(OH)3 / Gd(OH)3<K sp Mg(OH)2, in the electrolysis process, yttrium chloride and gadolinium chloride can react with OH - generated in the electrolysis to form a precipitate, and a thin and dense discharge product layer is formed on the surface of the magnesium anode, which can effectively avoid the formation of a loose and thick discharge product layer, and enhance the discharge performance of the magnesium anode, so as to effectively improve the discharge voltage and the anode utilization efficiency of the magnesium air battery, and meet the application of the magnesium air battery in small-sized long-distance communication equipment and the like.

[0031] And, the magnesium battery rare earth chloride electrolyte provided by the application can greatly improve the utilization efficiency of the magnesium anode, and can improve the utilization efficiency of the magnesium anode to 82.2%. Compared with the NaCl electrolyte, the rare earth chloride electrolyte provided by the application can not only improve the specific capacitance of the magnesium anode by about 822.3 mgh g -1 but also can improve the discharge voltage of the magnesium anode from 1.59 to 1.61 V, and the discharge potential is stable and stable, and can be suitable for various current densities.

[0032] Meanwhile, the magnesium battery rare earth chloride electrolyte provided by the application is prepared by using non-toxic and harmless sodium chloride, yttrium chloride and gadolinium chloride, which is not only green and environment-friendly, but also has relatively low preparation cost and high economic benefit. Meanwhile, the preparation method is simple, easy to prepare, convenient and fast. It has good application potential and is worth promoting. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The preparation method flow chart of the magnesium battery rare earth chloride electrolyte provided by the embodiment of the application is shown in the figure;

[0034] Fig. 2 (a) is an impedance analysis diagram of Mg-0.2Ca anode immersed in the electrolyte prepared in the comparative example 1 for 20 min, 1 h, 3 h, 6 h, 12 h and 24 h respectively;

[0035] Fig. 2 (b) is an impedance analysis diagram of Mg-0.2Ca anode immersed in the electrolyte prepared in the embodiment 1 for 20 min, 1 h, 3 h, 6 h, 12 h and 24 h respectively;

[0036] Fig. 2 (c) is an impedance analysis diagram of Mg-0.2Ca anode immersed in the electrolyte prepared in the embodiment 2 for 20 min, 1 h, 3 h, 6 h, 12 h and 24 h respectively;

[0037] Fig. 2 (d) is an impedance analysis diagram of Mg-0.2Ca anode immersed in the electrolyte prepared in the embodiment 3 for 20 min, 1 h, 3 h, 6 h, 12 h and 24 h respectively;

[0038] Figure 3 Fig. 2 (d) is an impedance analysis diagram of Mg-0.2Ca anode immersed in the electrolyte prepared in the embodiment 3 for 20 min, 1 h, 3 h, 6 h, 12 h and 24 h respectively;

[0039] Figure 4The macroscopic morphology diagram of Mg-0.2Ca anode immersed in the electrolyte prepared in Comparative Example 1 and Inventive Examples 1-3 for 7 days, wherein (a) is the macroscopic morphology diagram of Mg-0.2Ca anode immersed in the electrolyte prepared in Comparative Example 1 for 7 days, (b) is the macroscopic morphology diagram of Mg-0.2Ca anode immersed in the electrolyte prepared in Inventive Example 1 for 7 days, (c) is the macroscopic morphology diagram of Mg-0.2Ca anode immersed in the electrolyte prepared in Inventive Example 2 for 7 days, and (d) is the macroscopic morphology diagram of Mg-0.2Ca anode immersed in the electrolyte prepared in Inventive Example 3 for 7 days;

[0040] Figure 5 The discharge potential curve diagram of Mg-0.2Ca anode discharged at different current densities for 10h in the electrolyte prepared in Comparative Example 1 and Inventive Examples 1-3;

[0041] Figure 6 The surface morphology diagram of Mg-0.2Ca anode discharged at 10mA cm -2 for 10h in the electrolyte prepared in Comparative Example 1 and Inventive Examples 1-3, wherein (a) is the surface morphology diagram of Mg-0.2Ca anode discharged at 10mA cm -2 for 10h in the electrolyte prepared in Comparative Example 1, (b) is the surface morphology diagram of Mg-0.2Ca anode discharged at 10mA cm -2 for 10h in the electrolyte prepared in Inventive Example 1, (c) is the surface morphology diagram of Mg-0.2Ca anode discharged at 10mA cm -2 for 10h in the electrolyte prepared in Inventive Example 2, and (d) is the surface morphology diagram of Mg-0.2Ca anode discharged at 10mA cm -2 for 10h in the electrolyte prepared in Inventive Example 3, wherein the microscope scale lengths are 50µm and 5µm respectively;

[0042] Figure 7 The surface morphology diagram of Mg-0.2Ca anode discharged at 10mA cm -2 for 10h in the electrolyte prepared in Comparative Example 1 and Inventive Examples 1-3. DETAILED DESCRIPTION

[0043] The rare earth chloride electrolyte for magnesium battery provided by the embodiment of the application comprises, in mole fraction, 0.45-0.65M of sodium chloride, 0.4-0.6M of yttrium chloride, and 0.4-0.6M of gadolinium chloride.

[0044] The pH of the electrolyte is 7±0.2.

[0045] The rare earth chloride electrolyte for magnesium battery provided by the present invention uses sodium chloride, yttrium chloride and gadolinium chloride as the components of the electrolyte. sp Both are less than the K of Mg(OH)2 sp , that is, K sp Y(OH)3 / Gd(OH)3 <K sp Mg(OH)2, during the electrolysis process, yttrium chloride and gadolinium chloride can react with OH produced by electrolysis. - The reaction generates precipitation, forming a thin and dense discharge product layer on the surface of the magnesium anode, which can effectively avoid the formation of a loose and thick discharge product layer, enhance the discharge performance of the magnesium anode, and thus effectively improve the discharge voltage and anode utilization efficiency of the magnesium-air battery, meeting the application of magnesium-air batteries in small long-distance communication equipment and other aspects.

[0046] Compared with NaCl electrolyte, the rare earth chloride electrolyte provided by the present invention can increase the specific capacitance of magnesium anode by about 822.3 mgh g -1 The discharge voltage of the magnesium anode was increased from 1.59 to 1.61 V, making the discharge potential stable and applicable to various current densities. The utilization efficiency of the magnesium anode was also increased to 82.2%.

[0047] Furthermore, the magnesium battery rare earth chloride electrolyte provided by the present invention is not only green and environmentally friendly, but also has a relatively low preparation cost and high economic benefits because it is prepared using non-toxic and relatively inexpensive sodium chloride, yttrium chloride and gadolinium chloride.

[0048] See also Figure 1 The present invention provides a method for preparing a rare earth chloride electrolyte for a magnesium battery, comprising the following steps:

[0049] Step 1) According to the electrolyte containing 0.45-0.65M sodium chloride, 0.4-0.6M yttrium chloride, and 0.4-0.6M gadolinium chloride in a molar dispersion, the required amounts of sodium chloride, yttrium chloride, and gadolinium chloride are weighed and uniformly mixed to obtain a mixture.

[0050] Step 2) Add the mixture to deionized water and heat and stir until a transparent solution is obtained.

[0051] Wherein, in order to avoid the mixture from overheating when dissolving, ensure that the temperature of the solution does not rise sharply, when the mixture is dissolved in deionized water, the mixture is added to a 1 L beaker with a medicine spoon, then the beaker is combined with a glass rod to guide the flow, finally the deionized water is slowly poured into the uniformly mixed material along the inner wall of the beaker, to ensure that the mixture is uniformly dissolved and does not over-dissolve locally. Then the rotor is stirred and heated until the solution becomes transparent, to obtain a transparent solution.

[0052] Wherein, the stirring speed is controlled at 200-300 rpm / min.

[0053] Wherein, the temperature during heating is controlled at 50±5℃.

[0054] Step 3) Add dilute hydrochloric acid or sodium hydroxide to the transparent solution to adjust the pH of the solution to 7.0±0.2, to obtain a rare earth chloride electrolyte including 0.45-0.65 M of sodium chloride, 0.4-0.6 M of yttrium chloride, and 0.4-0.6 M of gadolinium chloride in terms of molar fraction.

[0055] Wherein, when adjusting the pH of the transparent solution, a pH-conductivity meter is used for detection and adjustment.

[0056] The preparation method of the rare earth chloride electrolyte for magnesium batteries provided by the application is simple, easy to prepare, and convenient and fast.

[0057] The application further provides a use method of the rare earth chloride electrolyte for magnesium batteries, comprising the following steps:

[0058] 1) Apply an external current in an electrochemical workstation.

[0059] Wherein, the current density applied by the electrochemical workstation is 2.5-10 mA·cm -2 .

[0060] 2) Collect the voltage change signal of the battery.

[0061] 3) Insert the magnesium anode and air cathode into the electrolyte for electrolysis.

[0062] Wherein, the magnesium anode is a Mg-0.2Ca anode, the magnesium content is ≥99.9 wt.%, the calcium content is ≥0.2 wt.%, the tin content is 0.01-0.012 wt.%, and the manganese and other impurity content is ≤0.01 wt.%.

[0063] Wherein, 10-15% of the surface area of the magnesium anode is exposed on the surface of the electrolyte.

[0064] Wherein, the air cathode is prepared by pressing and shearing treatment of materials including copper mesh, graphite powder, and foil under a pressure of 450-550 Mpa.

[0065] The rare earth chloride electrolyte for magnesium battery, and the preparation method and use method thereof provided by the present application are further explained and described below through the comparative examples and examples. It is hereby proposed that the following examples only illustrate the implementation method of the present application. The implementation method can be moderately improved without substantial change by those skilled in the art after skilled operation, and the implementation method is not limited to the examples provided by the present application.

[0066] Comparative Example 1

[0067] Deionized water was added to sodium chloride, and stirring treatment was performed by using a 45 mm rotor at a stirring speed of 120 rpm. The solution was monitored by using a pH-conductivity meter until the pH value was 7.0±0.2. The comparative electrolyte was prepared.

[0068] The use method of the electrolyte prepared in the present comparative example is as follows:

[0069] The Mg-0.2Ca alloy was used as the anode of the air battery, and the electrolyte used was 0.6M sodium chloride electrolyte. The Princeton electrochemical workstation was used to pass current to the magnesium anode material. The anode material specifically included ≥99.9wt.% of magnesium, 0.19-0.21wt.% of calcium, 0.01-0.012wt.% of tin, and ≤0.01wt.% of impurity elements such as manganese and iron. The applied current density was 2.5mA cm -2 and 10mA cm -2 . The cathode material was prepared by pressurizing treatment at 500MPa, shearing, and the like, and was composed of copper mesh, platinum sheet, and graphite powder and the like.

[0070] Before the experiment, the anode sample was polished bright by using sandpaper until the particle size was 4500. After polishing, alcohol was sprayed and blown dry, and cooled to room temperature. The Mg-0.2Ca anode material was placed in the electrolyte prepared in Comparative Example 1 for about 24h, and the area exposed to the electrolyte in the impedance analysis test was about 1cm -2 . The test frequency was set to 10 -2 ~10 5 Hz, and the material impedance analysis diagram was obtained as shown in FIG. 2(a).

[0071] The Mg-0.2Ca alloy anode material was placed in the electrolyte prepared in Comparative Example 1 for 3h and 24h, respectively, and the area exposed to the electrolyte in the potentiodynamic polarization test was about 1cm -2 . The scanning speed of the potentiodynamic polarization test was 0.333mV S -1 , and the starting point of the cathode scanning was 300mV below the open circuit potential, and the termination was at a current density of 10mA cm -2 . The potentiodynamic polarization diagram of the anode material in the electrolyte was obtained as shown in FIG. 3. Figure 3 .

[0072] The Mg-0.2Ca anode material was placed in the electrolyte prepared in Comparative Example 1 and allowed to stand at room temperature for seven days. The size of the magnesium anode used was 10×10×3 mm. The macroscopic morphology of the anode with weight loss after seven days was as follows: Figure 4 (a) shown.

[0073] After discharge, the Mg-0.2Ca anode was drawn in the electrolyte prepared in Comparative Example 1 at a discharge current density of 2.5 mA cm -2 and 10 mA cm -2 The potential curve after discharging for 10 hours is as follows: Figure 5 shown.

[0074] At a discharge current density of 2.5 mA cm -2 and 10 mA cm -2 When the discharge test duration is 10 h, the weight loss of the Mg-0.2Ca anode material after discharge in the electrolyte prepared in Comparative Example 1 is recorded, and the anode utilization efficiency and discharge specific capacity are obtained as shown in Table 1.

[0075] As can be seen from Figure 2(a), after immersion for more than 1 hour, the magnesium anode shows a small capacitive arc at different time points in the electrolyte prepared in Comparative Example 1. After long-term immersion, an obvious inductive arc will appear. This means that the corrosion resistance of the Mg-0.2Ca anode in the electrolyte prepared in Comparative Example 1 is poor, indicating that the utilization efficiency and specific capacitance of the Mg-0.2Ca anode during the discharge test are relatively low.

[0076] The fitted impedance data of the Mg-0.2Ca anode immersed in the electrolyte prepared in Comparative Example 1 for a certain period of time are shown in Table 1.

[0077] Table 1

[0078]

[0079]

[0080] From Table 1, we can see that as the immersion time increases, the polarization impedance (R p ) continued to decline and was only 258.1Ωcm at 24h. -2 , indicating that the Mg-0.2Ca anode cannot maintain high corrosion resistance in the electrolyte prepared in Comparative Example 1.

[0081] from Figure 3 As can be seen, the cathode polarization curve shifts to the right with increasing immersion time, indicating that the dissolution tendency of the Mg-0.2Ca anode in the electrolyte prepared in Comparative Example 1 increases with discharge time. Similar to the impedance results, this indicates that the anode exhibits poor corrosion resistance in the electrolyte prepared in Comparative Example 1.

[0082] The macroscopic morphology of Mg-0.2Ca anode after immersion in the electrolyte prepared in Comparative Example 1 for 7 days is shown in Fig. 2(a). It can be seen that the anode has been severely corroded at this time, and the anode has been dissolved from a block into an irregular shape, indicating that the electrolyte prepared in Comparative Example 1 cannot provide protection for the Mg-0.2Ca anode, and when used as an electrolyte, it is not conducive to improving the utilization efficiency of the anode. Figure 4

[0083] It can be seen from Fig. 2(b) that the Mg-0.2Ca anode has been severely corroded, and the anode has been dissolved from a block into an irregular shape, indicating that the electrolyte prepared in Comparative Example 1 cannot provide protection for the Mg-0.2Ca anode, and when used as an electrolyte, it is not conducive to improving the utilization efficiency of the anode. Figure 5 It can be seen from Fig. 2(b) that the Mg-0.2Ca anode has been severely corroded, and the anode has been dissolved from a block into an irregular shape, indicating that the electrolyte prepared in Comparative Example 1 cannot provide protection for the Mg-0.2Ca anode, and when used as an electrolyte, it is not conducive to improving the utilization efficiency of the anode. -2 The discharge voltage of the Mg-0.2Ca anode in the electrolyte prepared in Comparative Example 1 is 1.59 V at a current density of 2.5 mA cm -2 When the current density is increased to 10 mA cm -2 , the average discharge voltage is only 1.46 V, indicating that the voltage is low and the voltage fluctuation is large in the electrolyte prepared in Comparative Example 1.

[0084] The surface morphology of the Mg-0.2Ca anode after discharging at a current density of 10 mA cm -2 in the electrolyte prepared in Comparative Example 1 for 10 h is shown in Fig. 2(c). It is found by observation that a large amount of discharge product is deposited on the surface of the anode, which reduces the contact area of the anode with the electrolyte and significantly reduces the discharge voltage. Figure 6

[0085] The utilization efficiency and specific capacitance of the Mg-0.2Ca anode after discharging in the electrolyte prepared in Comparative Example 1 are shown in Table 2. It can be seen from Table 2 that the utilization efficiency and specific capacitance of the anode in the electrolyte prepared in Comparative Example 1 are low, and the discharge performance is poor.

[0086] The calculation formula of the anode utilization efficiency is as follows: (1) ;

[0087] The calculation formula of the specific capacitance is as follows:

[0088] (2) ;

[0089] The calculation formula of the theoretical weight loss is as follows:

[0090] (3).

[0091] Wherein, W theo represents the theoretical anode weight loss, △W represents the actual weight loss, t represents the discharge time, I represents the current density, F represents the Faraday constant, x i represents the valence of Mg and Ca elements, n i represents the mass fraction of each element in the anode, and m iThe relative atomic mass of each element in the anode.

[0092] The formula (1-3) shows that the utilization efficiency and specific capacitance of the anode depend on the actual reaction weight loss. Figure 7 It is shown that the anode reaction weight loss depends on the real-time hydrogen evolution amount during the discharge process. When the hydrogen evolution amount is lower, it represents that the mass loss of the Mg-0.2Ca anode during the discharge process is less, and the utilization efficiency and specific capacitance are higher; on the contrary, when the hydrogen evolution amount is high, it represents that the mass loss of the Mg-0.2Ca anode during the discharge process is more, and the utilization efficiency and specific capacitance are lower.

[0093] From Figure 7 It can be seen that the real-time hydrogen evolution amount of the Mg-0.2Ca anode in the electrolyte prepared in Comparative Example 1 is higher after being discharged at a current density of 10 mA cm -2 for 10 h, and the real-time hydrogen evolution amount of the Mg-0.2Ca anode in the electrolyte prepared in Comparative Example 1 is as high as 3.9 mL cm -2 Therefore, it can be shown that the mass loss of the Mg-0.2Ca anode during the discharge process is more, and the utilization efficiency and specific capacitance are lower.

[0094] In summary, the discharge voltage, utilization efficiency and specific capacitance of the Mg-0.2Ca anode in the electrolyte prepared in Comparative Example 1 are not improved.

[0095] Example 1

[0096] The concentration of sodium chloride in the rare earth chloride electrolyte for a magnesium battery provided by Example 1 of the present application is 0.6M, and the concentration of yttrium chloride is 0.5M.

[0097] The preparation method of the rare earth chloride electrolyte for a magnesium battery provided by Example 1 of the present application comprises:

[0098] Mixing sodium chloride and yttrium chloride to prepare a mixture;

[0099] Adding a proper amount of deionized water to the mixture;

[0100] Stirring the mixed and uniform material by using a 45mm rotor at a stirring speed of 150rpm; stirring while heating, the heating temperature is 45℃, and the solution is monitored by using a pH-conductivity meter until the pH value is 7.0±0.2, thereby preparing the rare earth chloride electrolyte of Example 1 of the present application;

[0101] The use method of the rare earth chloride electrolyte prepared by Example 1 of the present application is:

[0102] Mg-0.2Ca alloy as an air cell anode, the electrolyte used is the rare earth chloride electrolyte prepared in Example 1; the Princeton electrochemical workstation is used to pass current to the Mg-0.2Ca anode material; the anode material specifically includes ≥99.9wt.% of magnesium, 0.19-0.21wt.% of calcium, 0.01-0.012wt.% of tin, and ≤0.01wt.% of manganese, iron and other impurity elements. The applied current density is 2.5mA cm -2 and 10mA cm -2 ; the cathode material is prepared by 500MPa pressure treatment, shearing and the like, and is composed of copper mesh, platinum sheet and graphite powder and the like.

[0103] Before the experiment, the anode sample is polished with sandpaper until the particle size is 4500. After polishing, alcohol is sprayed and dried, and cooled to room temperature. The Mg-0.2Ca anode material is placed in the rare earth chloride electrolyte prepared in Example 1 for about 24h, and the area exposed to the electrolyte in the impedance analysis test is about 1cm -2 . The test frequency is set to 10 -2 -10 5 Hz, and the impedance analysis diagram of the anode material is shown in FIG. 2(b).

[0104] The Mg-0.2Ca alloy anode material is placed in the rare earth chloride electrolyte prepared in Example 1 for 3h and 24h respectively, and the area exposed to the electrolyte in the potentiodynamic polarization test is about 1cm -2 . The scanning speed of the potentiodynamic polarization test is 0.333mV S -1 , the starting point of the cathode scanning is 300mV below the open circuit potential, and the termination is at a current density of 10mA cm -2 ; the potentiodynamic polarization diagram of the anode material in the electrolyte is shown in FIG. 3. Figure 3

[0105] The Mg-0.2Ca anode material is placed in the rare earth chloride electrolyte prepared in Example 1 for seven days at room temperature, and the size of the Mg-0.2Ca anode used is 10x10x3mm, and the macroscopic morphology of the seven-day weight loss anode is shown in FIG. 4(b). Figure 4

[0106] After discharging, the discharge potential curve of the Mg-0.2Ca anode in the rare earth chloride electrolyte prepared in Example 1 at a discharge current density of 2.5mA cm -2 and 10mA cm -2 for 10h is drawn, and the discharge potential curve diagram is shown in FIG. 5. Figure 5

[0107] ​​​at a discharge current density of 2.5 mA cm -2 and 10 mA cm -2 for 10 h. The weight loss of Mg-0.2Ca anode material after discharge in the rare earth chloride electrolyte prepared in Example 1 was recorded, and the anode utilization efficiency and specific capacity were shown in Table 1.

[0108] Figure 2(b) shows that the capacitive resistance arc of Mg-0.2Ca anode material in the rare earth chloride electrolyte prepared in Example 1 increases with the increase of immersion time, indicating that the corrosion resistance of the anode is improved compared with Comparative Example 1.

[0109] Table 1 shows the fitting impedance data of Mg-0.2Ca anode after immersion in the rare earth chloride electrolyte prepared in Example 1 of the present application for a certain period of time, and the inhibition efficiency is calculated. When the immersion time reaches 24 h, the polarization resistance of Mg-0.2Ca anode material reaches 5530 Ω cm -2 , and the inhibition efficiency reaches 95.3%, indicating that Example 1 greatly improves the corrosion resistance of the anode, which may help to improve the anode utilization efficiency and specific capacity.

[0110] The potentiodynamic polarization curve of Mg-0.2Ca anode in the rare earth chloride electrolyte prepared in Example 1 is shown in Figure 3 Compared with the polarization curve of 3 h, the polarization curve of 24 h moves obviously to the left, indicating that the corrosion and dissolution of Mg-0.2Ca anode are inhibited.

[0111] Figure 4 (b) is the macroscopic morphology of Mg-0.2Ca anode after immersion in the rare earth chloride electrolyte prepared in Example 1 for 7 days. Compared with the irregular material of Comparative Example 1, Example 1 improves the corrosion resistance, but the Mg-0.2Ca anode material still shows obvious pitting in Example 1, indicating that Example 1 has limited improvement in the corrosion resistance of Mg-0.2Ca anode material. When Mg-0.2Ca anode dissolves in the discharge state, the metal / solution interface is significantly increased in pH due to the cathodic hydrogen evolution, and the local OH - content increases significantly. After the introduction of yttrium chloride, Y 3+ + 3OH - → Y(OH)3, the solubility product constant of Y(OH)3 is 1.6 × 10 -23 , and the solubility product constant of Mg(OH)2 is 5.6 × 10 -12 , indicating that Y(OH)3 preferentially deposits on the surface of Mg-0.2Ca anode. Y(OH)3 is more dense than Mg(OH)2, which effectively protects the anode and enhances the corrosion resistance.

[0112] Figure 5The discharge voltage curve of the Mg-0.2Ca anode after 10 h of discharge in the rare earth chloride electrolyte prepared in Example 1 is shown. It was observed that Example 1 could not effectively increase the discharge voltage.

[0113] Figure 6 (b) Mg-0.2Ca anode at 10 mA cm -2 Surface morphology after 10h discharge at the current density. Figure 6 It can be seen that after the anode is discharged in the rare earth chloride electrolyte prepared in Example 1, a large amount of discharge products are deposited on the surface. Although the amount of discharge products generated is less than that in the electrolyte prepared in Comparative Example 1, it still hinders the charge transfer and is not conducive to increasing the discharge voltage. Comparing the anode utilization efficiency and specific capacitance after discharge, it is found that the Mg-0.2Ca anode shows a utilization efficiency of 69.2% and a specific capacitance of 1463.8 mAh g in the rare earth chloride electrolyte prepared in Example 1. -1 The specific capacitance of Mg-0.2Ca anode is shown to be 0.8447 W·m-1, which indicates that the formed Y(OH)3-rich discharge product layer weakens the self-corrosion process of Mg-0.2Ca anode during discharge to some extent.

[0114] The utilization efficiency and specific capacitance changes of the Mg-0.2Ca anode after discharge in the rare earth chloride electrolyte prepared in Example 1 are shown in Table 2. As can be seen from Table 2, the utilization efficiency and specific capacitance of the anode in the rare earth chloride electrolyte prepared in Example 1 are not high, and the discharge performance is average.

[0115] Figure 7 This is a graph showing the real-time hydrogen evolution rate of the Mg-0.2Ca anode when discharged in the rare earth chloride electrolyte prepared in Example 1 for 10 h. The real-time hydrogen evolution rate at this time is 2.8 mL cm -2 Compared with comparative example 1, the real-time hydrogen evolution amount is reduced by about 1.1 mL cm -2 , indicating that the rare earth chloride electrolyte prepared in Example 1 can reduce the weight loss of the Mg-0.2Ca anode during the discharge process.

[0116] In summary, the electrolyte of Example 1 of the present invention contains a large amount of OH produced by the partial dissolution of yttrium chloride. - The reaction forms Y(OH)3, which is insoluble in water. Comparison of the solubility product constants reveals that Y(OH)3 is significantly lower than Mg(OH)2 and is more inclined to deposit on the surface of the Mg-0.2Ca anode. The deposition of Y(OH)3 reduces the content of loose and porous Mg(OH)2, improving the corrosion resistance of the anode. At the same time, it inhibits the real-time hydrogen evolution of the Mg-0.2Ca anode, reduces the amount of hydrogen evolved during discharge, and improves the anode utilization efficiency and specific capacitance. However, the effect of single yttrium chloride on improving discharge performance is limited. The pitting corrosion of the anode after long-term immersion and the low discharge voltage illustrate this problem.

[0117] Example 2

[0118] The concentration of sodium chloride in the rare earth chloride electrolyte for magnesium battery provided by the embodiment 2 of the present application is 0.6M, and the concentration of gadolinium chloride is 0.5M.

[0119] The preparation method of the rare earth chloride electrolyte for magnesium battery provided by the embodiment 2 of the present application is the same as that of the embodiment 1.

[0120] The use method and test method of the rare earth chloride electrolyte for magnesium battery prepared by the embodiment 2 of the present application are the same as those of the embodiment 1.

[0121] As can be seen from the figure 2(c), after the Mg-0.2Ca anode material is immersed in the rare earth chloride electrolyte prepared by the embodiment 2 for 1h, the capacitive reactance arc is obviously increased, which indicates that the rare earth chloride electrolyte prepared by the embodiment 2 can effectively improve the corrosion resistance of the anode in a short period of time.

[0122] As can be seen from the table 1, the impedance fitting values of the Mg-0.2Ca anode after being immersed in the rare earth chloride electrolyte prepared by the embodiment 2 for different time. When the immersion time is 1h, the polarization resistance of the Mg-0.2Ca anode material reaches 10144Ω cm -2 , and the inhibition efficiency reaches 87.9%. But when the immersion time is increased to 24h, the polarization resistance is only 2031.5Ω cm -2 , which indicates that the effect of the embodiment 2 on improving the corrosion resistance of the Mg-0.2Ca anode is limited, which may help to improve the utilization efficiency and specific capacitance of the anode.

[0123] As can be seen from the Figure 3 , the comparison of the movement of the polarization curves shows that the 24h polarization curve is obviously moved to the right, which indicates that the rare earth chloride electrolyte prepared by the embodiment 2 cannot continuously inhibit the corrosion process of the Mg-0.2Ca anode.

[0124] As can be seen from the Figure 4 (c), compared with the comparative example 1, after the corrosion products are removed, the residual amount of the Mg-0.2Ca anode in the rare earth chloride electrolyte prepared by the embodiment 2 is more, which indicates that the rare earth chloride electrolyte prepared by the embodiment 2 can improve the corrosion resistance, but the effect is not obvious. Since the gadolinium chloride is introduced, Gd 3+ + 3OH - → Gd (OH)3, and the solubility product constant of Gd(OH)3 is 2.0×10 -23 , while the solubility product constant of Mg(OH)2 is 5.6×10 -12, which means that Gd(OH)3 is preferentially deposited on the surface of Mg-0.2Ca anode. The compactness of Gd(OH)3 is better than Mg(OH)2 but weaker than Y(OH)3, so the corrosion resistance of Mg-0.2Ca anode in the rare earth chloride electrolyte prepared in Example 2 is better than Comparative Example 1 but worse than Example 1.

[0125] From Figure 5 It can be seen that, similar to Example 1, the rare earth chloride electrolyte prepared in Example 2 cannot effectively improve the discharge voltage.

[0126] Referring to Figure 6 (c), after 10 h of discharge at a current density of 10 mA cm -2 , a large amount of discharge product is deposited on the surface of Mg-0.2Ca anode in the rare earth chloride electrolyte prepared in Example 2 after discharge, which hinders the continuous contact of the anode with the electrolyte and reduces the electrochemical activity, and is not conducive to improving the discharge voltage. By comparing the utilization efficiency and specific capacitance of the anode after discharge, it is found that the Mg-0.2Ca anode in the rare earth chloride electrolyte prepared in Example 2 has a utilization efficiency of 63% and a specific capacitance of 1422.5 mAh g -1 , which is higher than that in Comparative Example 1. The Gd(OH)3 discharge product layer generated after the introduction of gadolinium chloride inhibits the excessive dissolution of the Mg-0.2Ca anode and improves the discharge performance.

[0127] The changes in the utilization efficiency and specific capacitance of the Mg-0.2Ca anode after discharge in the rare earth chloride electrolyte prepared in Example 2 are shown in Table 2. As can be seen from Table 2, the utilization efficiency and specific capacitance of the anode in the rare earth chloride electrolyte prepared in Example 2 are not high, and the discharge performance is general.

[0128] Referring to Figure 7 , the real-time hydrogen evolution amount of the Mg-0.2Ca anode in the rare earth chloride electrolyte prepared in Example 2 is 2.9 mL cm -2 , which is about 1 mL cm -2 lower than that in Comparative Example 1, indicating that the rare earth chloride electrolyte prepared in Example 2 can reduce the mass loss of the Mg-0.2Ca anode during discharge.

[0129] In summary, gadolinium chloride also reacts with OH - generated by the dissolution of the anode / electrolyte interface to form Gd(OH)3, which is difficult to dissolve in water and is more likely to be deposited on the surface of the Mg-0.2Ca anode due to its low solubility product constant, inhibiting the deposition process of loose Mg(OH)2 in the corrosion and discharge environment, and improving the utilization efficiency and specific capacitance of the anode. However, similar to the electrolyte formed by single yttrium chloride, the effect of single gadolinium chloride on improving the discharge performance of the Mg-0.2Ca anode is limited.

[0130] Example 3

[0131] In a rare earth chloride electrolyte for a magnesium battery provided in Example 3 of the present invention, the concentration of sodium chloride is 0.6M, the concentration of yttrium chloride is 0.5M, and the concentration of gadolinium chloride is 0.5M.

[0132] The preparation method of a rare earth chloride electrolyte for a magnesium battery provided in Example 3 of the present invention is the same as that in Example 1.

[0133] The usage and testing methods of the rare earth chloride electrolyte for magnesium batteries prepared in Example 3 of the present invention are the same as those in Example 1.

[0134] As can be seen from Figure 2(d), the capacitive reactance arc of the Mg-0.2Ca anode in the rare earth chloride electrolyte prepared in Example 3 is the largest after immersion for 24 hours, which proves that the corrosion resistance of the anode material in the rare earth chloride electrolyte prepared in Example 3 is the best.

[0135] Table 1 shows the fitted impedance data obtained after the Mg-0.2Ca anode was immersed in the rare earth chloride electrolyte prepared in Example 3 of the present invention for a certain period of time. As shown in Table 1, when the immersion time reaches 24 hours, the polarization impedance value of the Mg-0.2Ca anode is 8891Ω cm -2 , the inhibition efficiency is as high as 97.1%.

[0136] See also Figure 3 After the Mg-0.2Ca anode was immersed in the rare earth chloride electrolyte prepared in Example 3 for 24 h, the cathode polarization curve shifted significantly to the right, which also shows that the rare earth chloride electrolyte prepared in Example 3 of the present invention is most helpful in inhibiting the self-corrosion phenomenon of the Mg-0.2Ca anode.

[0137] See also Figure 4 (d) It can be seen that the surface of the Mg-0.2Ca anode is flat after being immersed in the rare earth chloride electrolyte prepared in Example 3 for seven days, and the material still maintains a block shape, indicating that the rare earth chloride electrolyte prepared in Example 3 has a long-term protective effect on the anode material.

[0138] See also Figure 5 It can be seen that the Mg-0.2Ca anode material has a high conductivity at 2.5 mA cm in the rare earth chloride electrolyte prepared in Example 3. -2 At the current density of 10 mA cm, the average discharge voltage reached 1.6 V, and the discharge voltage curve was stable, indicating that the rare earth chloride electrolyte prepared in Example 3 can greatly improve the discharge performance of the anode. -2The discharge voltage of the rare earth chloride electrolyte prepared in Example 3 can still be greatly improved by about 400 mV at a current density, which indicates that the discharge performance of the Mg-0.2Ca anode in the rare earth chloride electrolyte prepared in Example 3 is stable and reliable at different current densities.

[0139] Referring to Figure 6 (d), after the Mg-0.2Ca anode is discharged in the rare earth chloride electrolyte prepared in Example 3 for 10 h, no large amount of discharge products is deposited on the surface of the Mg-0.2Ca anode, which indicates that the rare earth chloride electrolyte prepared in Example 3 can effectively inhibit the deposition process of the discharge products on the surface of the anode, form a thin and dense discharge product layer on the surface, and ensure the charge transfer rate, thereby improving the discharge voltage. By comparing the utilization efficiency and the specific capacity value, the Mg-0.2Ca anode in the rare earth chloride electrolyte prepared in Example 3 has a utilization efficiency of 82.2% and a specific capacity of 1856 mA h g -2 at a current density, which shows extremely high anode utilization efficiency and specific capacity, respectively 82.2% and 1856 mA h g -1 The rare earth chloride electrolyte prepared in Example 3 significantly improves the discharge performance of the Mg-0.2Ca anode, and has great industrial application potential.

[0140] The utilization efficiency and specific capacity of the Mg-0.2Ca anode after being discharged in the rare earth chloride electrolyte prepared in Example 3 are shown in Table 2. As can be seen from Table 2, the utilization efficiency and specific capacity of the anode in the rare earth chloride electrolyte prepared in Example 3 are higher, and the discharge performance is better.

[0141] Referring to Figure 7 By comparing the real-time hydrogen evolution amount, it can be seen that the real-time hydrogen evolution amount of the Mg-0.2Ca anode in the rare earth chloride electrolyte prepared in Example 3 is only 2.5 mL cm -2 , which indicates that the rare earth chloride electrolyte prepared in Example 3 can effectively inhibit the self-corrosion process of the anode during the discharge process, reduce the mass loss of the anode, and improve the utilization efficiency and specific capacity.

[0142] This is because yttrium chloride and gadolinium chloride are introduced at the same time, and the reactivity of Y 3+ and Gd 3+ with OH - is obviously higher than that of Mg 2 + A protective layer rich in Gd(OH)3 and Y(OH)3 is deposited on the surface of the Mg-0.2Ca anode. At the same time, the solubility product constant of Gd(OH)3 (2.0 x 10 -23 ) is slightly higher than that of Y(OH)3 (1.6 x 10 -23), the preferentially deposited Y(OH)3 will provide more nucleation sites for the formation of Gd(OH)3, further promoting the deposition of Gd(OH)3 and resulting in a dense Mg-0.2Ca anode surface film layer.

[0143] As described above, in the rare earth chloride electrolyte prepared in Example 3, the Mg-0.2Ca anode forms a thin layer rich in Gd(OH)3 and Y(OH)3 on the surface under the discharge environment due to the combined action of Gd 3+ , Y 3+ . The thin layer not only ensures ion transmission, but also inhibits the self-corrosion process of the anode material, so that the Mg-0.2Ca anode exhibits extremely high electrochemical performance in the rare earth chloride electrolyte prepared in Example 3.

[0144] Table 2

[0145]

[0146] Example 4

[0147] In the rare earth chloride electrolyte for magnesium batteries provided in Example 4 of the present application, the concentration of sodium chloride is 0.45M, the concentration of yttrium chloride is 0.4M, and the concentration of gadolinium chloride is 0.4M.

[0148] The preparation method of the rare earth chloride electrolyte for magnesium batteries provided in Example 4 of the present application is the same as that in Example 1.

[0149] The use method of the rare earth chloride electrolyte for magnesium batteries prepared in Example 4 of the present application is the same as that in Example 1.

[0150] The utilization efficiency and specific capacitance change of the Mg-0.2Ca anode after discharge in the rare earth chloride electrolyte prepared in Example 4 of the present application are shown in Table 2. As can be seen from Table 2, the utilization efficiency and specific capacitance of the anode in the rare earth chloride electrolyte prepared in Example 4 are higher, and the discharge performance is better.

[0151] Example 5

[0152] In the rare earth chloride electrolyte for magnesium batteries provided in Example 5 of the present application, the concentration of sodium chloride is 0.55M, the concentration of yttrium chloride is 0.45M, and the concentration of gadolinium chloride is 0.5M.

[0153] The preparation method of the rare earth chloride electrolyte for magnesium batteries provided in Example 5 of the present application is the same as that in Example 1.

[0154] The use method of the rare earth chloride electrolyte for magnesium batteries prepared in Example 5 of the present application is the same as that in Example 1.

[0155] The utilization efficiency and specific capacitance change of Mg-0.2Ca anode after discharging in the rare earth chloride electrolyte prepared in Example 5 of the present application are shown in Table 2, and it can be seen from Table 2 that the utilization efficiency and specific capacitance of the anode in the rare earth chloride electrolyte prepared in Example 5 are higher, and the discharging performance is better.

[0156] Example 6

[0157] In the rare earth chloride electrolyte for magnesium battery provided in Example 6 of the present application, the concentration of sodium chloride is 0.65 M, the concentration of yttrium chloride is 0.6 M, and the concentration of gadolinium chloride is 0.6 M.

[0158] The preparation method of the rare earth chloride electrolyte for magnesium battery provided in Example 6 of the present application is the same as that in Example 1.

[0159] The use method of the rare earth chloride electrolyte for magnesium battery provided in Example 6 of the present application is the same as that in Example 1.

[0160] The utilization efficiency and specific capacitance change of Mg-0.2Ca anode after discharging in the rare earth chloride electrolyte prepared in Example 6 of the present application are shown in Table 2, and it can be seen from Table 2 that the utilization efficiency and specific capacitance of the anode in the rare earth chloride electrolyte prepared in Example 6 are higher, and the discharging performance is better.

[0161] Example 7

[0162] In the rare earth chloride electrolyte for magnesium battery provided in Example 7 of the present application, the concentration of sodium chloride is 0.6 M, the concentration of yttrium chloride is 0.5 M, and the concentration of gadolinium chloride is 0.4 M.

[0163] The preparation method of the rare earth chloride electrolyte for magnesium battery provided in Example 7 of the present application is the same as that in Example 1.

[0164] The use method of the rare earth chloride electrolyte for magnesium battery provided in Example 7 of the present application is the same as that in Example 1.

[0165] The utilization efficiency and specific capacitance change of Mg-0.2Ca anode after discharging in the rare earth chloride electrolyte prepared in Example 7 of the present application are shown in Table 2, and it can be seen from Table 2 that the utilization efficiency and specific capacitance of the anode in the rare earth chloride electrolyte prepared in Example 7 are higher, and the discharging performance is better.

[0166] Example 8

[0167] In the rare earth chloride electrolyte for magnesium battery provided in Example 8 of the present application, the concentration of sodium chloride is 0.5 M, the concentration of yttrium chloride is 0.55 M, and the concentration of gadolinium chloride is 0.5 M.

[0168] The preparation method of the rare earth chloride electrolyte for magnesium battery provided in Example 8 of the present application is the same as that in Example 1.

[0169] The application embodiment 8 provides a use method of the rare earth chloride electrolyte of the magnesium battery.

[0170] The utilization efficiency and specific capacitance change of the Mg-0.2Ca anode after discharging in the rare earth chloride electrolyte prepared in the application embodiment 8 are shown in Table 2, and it can be known from Table 2 that the utilization efficiency and specific capacitance of the anode in the rare earth chloride electrolyte prepared in the application embodiment 8 are higher, and the discharging performance is better.

[0171] Embodiment 9

[0172] The application embodiment 9 provides a rare earth chloride electrolyte of a magnesium battery, wherein the concentration of sodium chloride is 0.6 M, the concentration of yttrium chloride is 0.6 M, and the concentration of gadolinium chloride is 0.6 M.

[0173] The application embodiment 9 provides a preparation method of the rare earth chloride electrolyte of the magnesium battery, which is same as that of the application embodiment 1.

[0174] The application embodiment 9 provides a use method of the rare earth chloride electrolyte of the magnesium battery, which is same as that of the application embodiment 1.

[0175] The utilization efficiency and specific capacitance change of the Mg-0.2Ca anode after discharging in the rare earth chloride electrolyte prepared in the application embodiment 9 are shown in Table 2, and it can be known from Table 2 that the utilization efficiency and specific capacitance of the anode in the rare earth chloride electrolyte prepared in the application embodiment 9 are higher, and the discharging performance is better.

[0176] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the application rather than limit the application, and although the application is described in detail with reference to the examples, those skilled in the art should understand that the technical solutions of the application can be modified or replaced equivalently without departing from the spirit and scope of the technical solutions of the application, and all should be covered in the scope of the claims of the application.

Claims

1. A rare earth chloride electrolyte for a magnesium battery, characterized in that: In terms of mole fraction, its components include 0.45-0.65M sodium chloride, 0.4-0.6M yttrium chloride, and 0.4-0.6M gadolinium chloride; The pH of the electrolyte is 7±0.2; The method for preparing the rare earth chloride electrolyte for magnesium batteries comprises the following steps: Taking required amounts of sodium chloride, yttrium chloride and gadolinium chloride and mixing them evenly to obtain a mixture; Add the mixture into deionized water and heat and stir until a transparent solution is obtained; Dilute hydrochloric acid or sodium hydroxide is added to the transparent solution to adjust the pH of the solution to 7.0±0.2 to obtain the electrolyte.

2. The rare earth chloride electrolyte for magnesium batteries according to claim 1, characterized in that: The stirring speed is controlled at 200-300 rpm / min.

3. The rare earth chloride electrolyte for magnesium batteries according to claim 1, characterized in that: The heating temperature is 50±5°C.

4. The rare earth chloride electrolyte for magnesium batteries according to claim 1, characterized in that: The pH value of the transparent solution is detected by a pH-conductivity meter.

5. A method for using the rare earth chloride electrolyte for magnesium batteries according to any one of claims 1 to 4, characterized in that: The steps include: Apply an external current to the electrochemical workstation; Collect battery voltage change signals; A magnesium anode and an air cathode are inserted into the electrolyte to perform electrolysis.

6. The method for using the rare earth chloride electrolyte for magnesium batteries according to claim 5, characterized in that: The current density applied by the electrochemical workstation is 2.5 to 10 mA·cm-2.

7. The method for using the rare earth chloride electrolyte for magnesium batteries according to claim 5, characterized in that: The magnesium anode is a Mg-0.2Ca anode, with a magnesium content of ≥99.9 wt.%, a calcium content of ≥0.2 wt.%, a tin content of 0.01-0.012 wt.%, and a content of impurities such as manganese of ≤0.01 wt.%.

8. The method for using the rare earth chloride electrolyte for magnesium batteries according to claim 5, characterized in that: In the electrolyte, 10-15% of the surface area of ​​the magnesium anode is exposed on the surface of the electrolyte.

9. The method for using the rare earth chloride electrolyte for magnesium batteries according to claim 5, characterized in that: The air cathode is prepared by using materials including copper mesh, graphite powder and foil through 450-550 MPa pressure pressing and shearing treatment.

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