A cathode material for a magnesium-based battery and a high-voltage magnesium-based battery

Abstract

The present invention belongs to the technical field of magnesium batteries, and particularly relates to a magnesium-based battery cathode material and a high-voltage magnesium-based battery. The chemical formula of the magnesium-based battery cathode material is A x Mn y M 1‑y [Fe(CN)6] z ·nH2O, wherein A is any one of Na, K, Mg, and Ca, M is selected from any one of transition metals, 0 ≤ x ≤ 2, 0 < y < 1, 0 < z < 1, 0 ≤ n < 4; the preparation method of the magnesium-based battery cathode material has mild conditions, the reaction can be completed at room temperature, and the reaction raw materials are relatively conventional and the cost is relatively low; moreover, the working voltage is high, up to 3V; the discharge specific capacity is large, up to 117 mAhg ‑1 ; and the cycle performance is good. At a current density of 100 mAg ‑1 , after 100 cycles, the specific capacity can still be maintained above 50%.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnesium batteries, and particularly relates to a positive electrode material for a magnesium-based battery and a high-voltage magnesium-based battery. Background Art

[0002] A magnesium-based battery refers to a rechargeable battery with metallic magnesium as the negative electrode. The core components of a magnesium-based battery are the magnesium negative electrode, the electrolyte, and the positive electrode material. In recent years, the developed rechargeable magnesium-based battery has great potential. The working principle of a magnesium-based battery is similar to that of a lithium battery. However, a magnesium-based battery is safer than a lithium battery because magnesium and quite a number of magnesium compounds are non-toxic or low-toxic, magnesium is less reactive than lithium, is easy to process and operate, is safer when exposed to air than lithium, and a magnesium-based battery does not have the problem of dendrite growth similar to that of a lithium battery. In terms of price, since magnesium has a higher abundance in the earth's crust, the price of magnesium is 24 times cheaper than that of lithium, and China is rich in magnesium resources, ranking first in the world in reserves. Developing magnesium batteries has unique advantages. Therefore, researching and developing metallic magnesium as the negative electrode of a battery has important significance and an attractive prospect. However, because Mg ions have a large polarization effect and a strong solvation effect, and the ion migration kinetics of embedding into an inorganic host is slow, the positive electrode materials commonly used in lithium-ion batteries cannot be similarly applied to magnesium batteries.

[0003] Traditional magnesium batteries mainly use Chevrel phase Mo6S8 as the positive electrode, a chlorine-containing organic aluminum magnesium salt as the electrolyte, and pure magnesium as the negative electrode. Mo6S8 can only output an average discharge voltage of about 1.1V and a maximum specific capacity of 122mAh / g, with a low energy density (134.2Wh / kg); at the same time, the oxidation stability of the chlorine-containing electrolyte is not high, and the current collector will be severely corroded during the charging process, making it difficult for magnesium batteries to be widely applied. Prussian blue-based compound crystals have an open framework structure and have the characteristics of a high voltage platform, stable structure, and excellent ion diffusion kinetics as positive electrode materials, and the synthesis process is simple and the price is low, making them suitable as positive electrode materials for magnesium-based batteries; manganese-based Prussian white is one of the Prussian blue-based compounds, with a theoretical specific capacity of 170mAh / g. However, the current manganese-based Prussian white often contains more crystal water and vacancy defects, and has defects such as low sodium content, low specific capacity, and poor cycle stability; at the same time, there is still no suitable chlorine-free high-voltage electrolyte to match it to achieve normal reversible charge and discharge.

[0004] Therefore, it is necessary to develop a magnesium-based battery with a high specific capacity, high working voltage, charge-discharge ability, and good cycle stability. Summary of the Invention

[0005] Aiming at the above problems, one of the purposes of the present invention is to provide a key component of a high-voltage magnesium-based battery and its preparation method, so as to provide a magnesium-based battery with a high specific capacity, high working voltage, and good cycle stability.

[0006] To achieve the above object, the following technical solutions may be adopted:

[0007] On the one hand, the present invention provides a cathode material for a magnesium-based battery, with the chemical formula A x Mn y M 1-y [Fe(CN)6] z ·nH2O, where A is any one of Na, K, Mg, and Ca, M is selected from any one of transition metals, 0 ≤ x ≤ 2, 0 < y < 1, 0 < z < 1, and 0 ≤ n < 4.

[0008] On the other hand, the present invention provides a preparation method for the above-mentioned cathode material for a magnesium-based battery, including: dissolving Mn 2+ salt and a transition metal salt in water to obtain solution A, and dissolving sodium ferrocyanide hydrate or potassium ferrocyanide and a metal salt in water to obtain solution B; mixing solution A and solution B, and centrifuging to obtain the cathode material for a magnesium-based battery, where the metal salt is selected from any one of Na salts, K salts, Mg salts, and Ca salts.

[0009] On yet another aspect, the present invention provides a high-voltage magnesium-based battery, which includes a positive electrode, a negative electrode, and an electrolyte; the positive electrode includes the above-mentioned cathode material for a magnesium-based battery or the cathode material for a magnesium-based battery prepared by the above-mentioned preparation method.

[0010] The beneficial effects of the present invention at least include:

[0011] (1) The preparation method for the cathode material for a magnesium-based battery provided by the present invention has mild conditions, the reaction can be completed at room temperature, and the reaction raw materials are all relatively conventional, with a relatively low cost;

[0012] (2) The high-voltage magnesium-based battery provided by the present invention has a high working voltage, which can reach 3V; the discharge specific capacity is large, which can reach 117 mAhg -1 ; moreover, it has good cycling performance. At a current density of 100 mAg -1 , after 100 cycles, the specific capacity can still be maintained above 50%. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 X-ray diffraction spectra of the cathode materials prepared in Example 1 and Example 3;

[0014] Figure 2 SEM images of the cathode materials prepared in Example 1 and Example 3;

[0015] Figure 3 TG diagrams of the cathode materials prepared in Example 1 and Example 3;

[0016] Figure 4 X-ray diffraction spectra of the cathode materials prepared in Example 2 and Example 4;

[0017] Figure 5 SEM images of the cathode materials prepared in Example 2 and Example 4;

[0018] Figure 6 TG diagrams of the cathode materials prepared in Example 2 and Example 4;

[0019] Figure 7 First charge-discharge curves of the high-voltage magnesium-based battery of Example 1;

[0020] Figure 8 Cycling curves of the high-voltage magnesium-based battery of Example 1;

[0021] Figure 9 First charge-discharge curves of the high-voltage magnesium-based battery of Example 2;

[0022] Figure 10 Cycling curves of the high-voltage magnesium-based battery of Example 2;

[0023] Figure 11 First charge-discharge curves of the high-voltage magnesium-based battery of Example 3;

[0024] Figure 12 Cycling curves of the high-voltage magnesium-based battery of Example 3;

[0025] Figure 13 First charge-discharge curves of the high-voltage magnesium-based battery of Example 4;

[0026] Figure 14 Cycling curves of the high-voltage magnesium-based battery of Example 4. Detailed implementation manners

[0027] The examples given are for better explaining the present invention, but the content of the present invention is not limited only to the examples given. Therefore, those skilled in the art who make non-essential improvements and adjustments to the implementation manners based on the above-described invention content still fall within the protection scope of the present invention.

[0028] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. Unless having a significantly different meaning in the context, the expressions in the singular form include the plural form. As used herein, it should be understood that terms such as "including", "having", "containing" are intended to indicate the presence of features, numbers, operations, components, parts, elements, materials or combinations. The terms of the present invention are disclosed in the specification, and are not intended to exclude the possibility of the existence or addition of one or more other features, numbers, operations, components, parts, elements, materials or their combinations. As used herein, depending on the circumstances, " / " can be interpreted as "and" or "or".

[0029] On the one hand, the present invention provides a cathode material for a magnesium-based battery, with the chemical formula A x Mn y M 1-y [Fe(CN)6] z ·nH2O, where A is any one of Na, K, Mg, and Ca, M is selected from any one of transition metals, 0 ≤ x ≤ 2, 0 < y < 1, 0 < z < 1, 0 ≤ n < 4. Specifically, the cathode material for the magnesium-based battery in the present invention is a manganese-based Prussian white-like compound, and its specific capacity can actually reach 117 mAh g -1 , and can still maintain more than 50% of the specific capacity after 100 cycles at a high current density (100 mA g -1 ), and the cycling performance is good. It should be noted that due to the Jahn-Teller effect, the cycling life of pure manganese is not high, so other ions (other transition metal elements except Mn) need to be doped to alleviate the Jahn-Teller effect and improve the cycling life; that is, in some embodiments, M may not be selected as manganese, and the obtained cathode material for the magnesium-based battery has a higher cycling life. It should also be understood that for the cathode material for the magnesium-based battery (A x Mn y M 1-y [Fe(CN)6] z ·nH2O) (0 ≤ x ≤ 2, 0 < y < 1, 0 < z < 1, 0 ≤ n < 4), x can be 0, 1, 1.5, etc., y can be 0.5, 0.8, 0.9, etc., z can be 0.6, 0.8, 0.9, etc., n can be 0, 1, 2, 3, etc.; in some embodiments, the above-mentioned cathode material for the magnesium-based battery can preferably be Na 1.9 Mn 0.9 Fe 0.1 [Fe(CN)6] 0.9 or Na 1.9 Mn[Fe(CN)6] 0.9 with high capacity and high working voltage.

[0030] On the other hand, the present invention provides a preparation method for the above-mentioned cathode material for a magnesium-based battery, including: dissolving a Mn 2+ salt and a transition metal salt in water to obtain solution A, and dissolving sodium ferrocyanide hydrate or potassium ferrocyanide and a metal salt in water to obtain solution B; mixing solution A and solution B, and centrifuging to obtain the cathode material for the magnesium-based battery (A x Mn y M 1-y [Fe(CN)6] z ·nH2O), and the metal salt is selected from any one of Na, K, Mg, and Ca; this preparation method can complete the reaction at room temperature, and the reaction conditions are relatively mild, which is conducive to industrialization.

[0031] It should be noted that in the above preparation method of the magnesium-based battery cathode material, in solution A, the mass concentration of the Mn 2+ salt can be 6 g / L - 8 g / L, such as 6.8 g / L, 7 g / L or 7.8 g / L, etc. The Mn 2+ salt is known in the art, such as MnCl2 and MnSO4, etc.; the mass concentration of the transition metal salt is 0.9 g / L - 1.5 g / L, such as 0.96 g / L, 1 g / L or 1.2 g / L, etc. The transition metal salt is known in the art, such as the trivalent salt FeCl3 of the transition metal iron; in solution B, the mass concentration of sodium ferrocyanide hydrate can be 14 g / L - 15 g / L, such as 14.5 g / L, 14.6 g / L or 14.7 g / L, etc., and the mass concentration of the metal salt can be 6 g / L - 8 g / L, such as 6.5 g / L, 7 g / L or 7.5 g / L, etc.

[0032] It should also be noted that in the above preparation method of the magnesium-based battery cathode material, in order to make the reaction between solution A and solution B more sufficient, the mixing method of solution A and solution B can be to slowly drip solution A into solution B; during the dripping process, in order to further fully react, stirring can also be carried out, and the stirring method can be selected from the methods known in the art, such as magnetic stirring or stirrer stirring, etc.; after solution A is completely dripped into solution B, continue to stir for a period of time. In addition, it should be understood that in the above preparation method, the precipitate obtained after centrifugation can be washed conventionally with deionized water, and the centrifugation-deionized water washing can be cycled many times. In order to ensure more thorough washing, after washing with deionized water, it can be centrifuged again and washed with alcohol. The precipitate obtained after alcohol washing is the above-mentioned magnesium-based battery cathode material. Of course, it should be understood that the obtained precipitate needs to be dried before being used as the battery cathode material, and the drying method can be selected from the methods known in the art, such as drying in a vacuum environment or drying in an oven, etc., or drying can be carried out in stages, such as first drying in an oven at 60°C for 24 h, and then drying in a vacuum at 120°C for 24 h.

[0033] The present invention provides a high-voltage magnesium-based battery in one aspect, which includes a positive electrode, a negative electrode and an electrolyte; the positive electrode includes the above-mentioned magnesium-based battery cathode material or the magnesium-based battery cathode material prepared by the above-mentioned preparation method. It should be understood that in addition to the positive electrode, the negative electrode and the electrolyte, the high-voltage magnesium-based battery also includes a separator, and the separator can be selected from those known in the art, such as a three-layer composite film composed of polypropylene, polyethylene and polypropylene, or a glass fiber separator, etc.

[0034] Further, in the above high-voltage magnesium-based battery, the positive electrode further includes a conductive agent and a binder. Among them, the mass ratio of the magnesium-based battery positive electrode material, the conductive agent, and the binder is (6.5 - 7.5):(1.5 - 2.5):1. For example, the mass ratio is 7:2:1, 7.2:2.1:1, or 6.6:1.5:1, etc. It should be understood that the conductive agent can be selected from the conductive agents for batteries known in the art, such as carbon black conductive agent, graphite conductive agent, carbon fiber conductive agent, carbon nanotube conductive agent, and graphene conductive agent, etc.; the binder can be selected from the binders for batteries known in the art, such as PVDF (polyvinylidene fluoride), PVA (polyvinyl alcohol), CMC (sodium carboxymethyl cellulose), PTEF (polytetrafluoroethylene), PP (polyethylene hydrocarbons), fluorinated rubber, polyurethane, or SBR rubber, etc.

[0035] It should be noted that in the above high-voltage magnesium-based battery, the preparation method of the positive electrode is a conventional preparation method in the art. In some specific embodiments, the positive electrode material (compound A x Mn y M 1-y [Fe(CN)6] z ·nH2O), the conductive agent, and the binder are dispersed in NMP solvent according to the mass ratio, and after mixing evenly, they are coated on the Al foil and then dried to obtain the positive electrode.

[0036] Further, in the above high-voltage magnesium-based battery, the electrolyte can be selected from the magnesium-based battery electrolytes known in the art, such as organic borate complex salts or inorganic borates; in some embodiments, the organic borate complex salt can be Na x B(OR)4, K x B(OR)4, Mg x B(OR)4, and Ca x B(OR)4, one or more combinations of which, where, Na x B(OR)4, K x B(OR)4, Mg x B(OR)4, and Ca x B(OR)4, the value of x in which is 0.5 ≤ x ≤ 1, and R is a fluoroalkyl group; it should be noted that, Na x B(OR)4, K x B(OR)4, Mg x B(OR)4, and Ca xThe values of x in B(OR)4 can be the same or different, and R can be the same fluoroalkyl group or different fluoroalkyl groups; in certain specific embodiments, the electrolyte can include NaB(OCHC2F6)4, Mg[B(OCHC2F6)4]2, KB(OCHC2F6)4, etc.; in certain specific embodiments, the electrolyte can include a combination of NaB(OCHC2F6)4 and Mg[B(OCHC2F6)4]2, or a combination of NaB(OCHC2F6)4 and KB(OCHC2F6)4, etc.; in certain specific embodiments, the electrolyte can include a combination of NaB(OCHC2F6)4 and Mg[B(OCHC2F6)4]2, where the molar ratio of NaB(OCHC2F6)4 to Mg[B(OCHC2F6)4]2 can be (1.5 - 2.5):1, such as 2:1, 2.2:1, or 2.3:1, etc.

[0037] In some embodiments, the inorganic borate can be selected from one or more combinations of NaBH4, KBH4, Mg(BH4)2, NaBF4, KBF4, and Mg(BF4)2. For example, NaBH4 or KBH4 can be selected alone, or a combination of NaBH4 and KBH4 can be selected, or a combination of Mg(BH4)2 and NaBF4 can be selected, or a combination of NaBH4, KBH4, and Mg(BH4)2 can be selected, etc.

[0038] Furthermore, in the above high-voltage magnesium-based battery, the solvent of the electrolyte can be selected from one or more combinations of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. For example, tetrahydrofuran, ethylene glycol dimethyl ether, or diethylene glycol dimethyl ether can be selected alone, or a mixture of tetrahydrofuran, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether can be selected, or a combination of triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether can be selected.

[0039] It should also be noted that the electrolyte of the above high-voltage magnesium-based battery does not contain chlorine, avoiding the problem that the oxidation stability of the chlorine-containing electrolyte is not high, which will cause serious corrosion of the current collector during the charging process.

[0040] Furthermore, the negative electrode can be selected from magnesium foil or magnesium alloy. The magnesium alloy is a magnesium alloy known in the art, such as AZ31, magnesium gadolinium alloy, or magnesium cerium alloy. It should be noted that the negative electrode can be selected from the negative electrode materials of magnesium batteries known in the art. Preferably, any one of magnesium foil, AZ31, magnesium gadolinium alloy, and magnesium cerium alloy is selected. These several materials are all negative electrode materials with relatively excellent performance currently used in magnesium batteries. In addition, it should be understood that before use, the surface of the negative electrode can be polished to be shiny to increase its conductivity.

[0041] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with specific examples, but the content of the present invention is not limited to the following examples only.

[0042] I. Cathode Material and Battery Preparation

[0043] Example 1

[0044] (1) Dissolve 0.34 g of MnCl2 and 0.048 g of FeCl3 in 50 ml of deionized water to form solution A, and dissolve 1.45 g of Na4Fe(CN)6·10H2O and 0.7 g of NaCl in 100 ml of deionized water to form solution B; at 25 °C and under magnetic stirring, slowly drip solution A into solution B and continue stirring for 12 h, then centrifuge and wash three times with deionized water and once with alcohol to obtain a light blue precipitate. After that, dry the precipitate at 60 °C for 24 h, and then vacuum dry at 120 °C for 24 h to obtain the cathode material Na 1.9 Mn 0.9 Fe 0.1 [Fe(CN)6] 0.9 ;

[0045] (2) Disperse the cathode material Na 1.9 Mn 0.9 Fe 0.1 [Fe(CN)6] 0.9 , conductive carbon black, and binder PVDF in a mass ratio of 7:2:1 in NMP solvent, stir for 12 h to obtain a uniformly mixed cathode slurry. Then, uniformly coat the cathode slurry on Al foil, and vacuum dry at 60 °C for 5 h. After cutting into pieces, quickly transfer the cathode sheet to an argon glove box for standby;

[0046] (3) Polish the surface of a 50-μm-thick magnesium metal foil with 800-mesh and 1500-mesh sandpapers until it is shiny, wipe off the ground powder with lint-free paper, cut it into a certain size, and then put it into an argon glove box for standby;

[0047] (4) In an argon glove box, add NaB(OCHC2F6)4 and Mg[B(OCHC2F6)4]2 to DME in a molar ratio of 2:1 to prepare a boron-based electrolyte with a sodium ion concentration of 0.6 mol / L and a magnesium ion concentration of 0.3 mol / L for standby;

[0048] (5) Assemble the cathode sheet, anode sheet, boron-based electrolyte, and glass fiber separator into a CR2032 button-type rechargeable magnesium-based battery according to the conventional method.

[0049] Example 2

[0050] (1) Take 53.68 g of a 50 wt% aqueous solution of Mn(NO3)2 as Solution A, and dissolve 72.609 g of Na4Fe(CN)6·10H2O and 35.064 g of NaCl in 600 ml of deionized water to form Solution B; at 25 °C with magnetic stirring, slowly add Solution A dropwise to Solution B and continue stirring for 12 h, then centrifuge and wash three times with deionized water and once with alcohol to obtain a white precipitate. After that, dry the precipitate at 60 °C for 24 h, and then vacuum dry at 120 °C for 24 h to obtain the cathode material Na 1.9 Mn[Fe(CN)6] 0.9 ;

[0051] (2) Disperse the cathode material Na 1.9 Mn[Fe(CN)6] 0.9 , conductive carbon black, and binder PVDF in a mass ratio of 7:2:1 in NMP solvent, stir for 12 h to obtain a uniformly mixed cathode paste. Then, uniformly coat the cathode paste on an Al foil, and vacuum dry at 60 °C for 5 h. After cutting into pieces to obtain cathode sheets, quickly transfer them to an argon glove box for standby;

[0052] (3) Polish the surface of a 50-μm-thick magnesium metal foil with 800-mesh and 1500-mesh sandpapers until it is shiny, wipe off the ground powder with lint-free paper, cut it into a certain size, and then put it into an argon glove box for standby;

[0053] (4) In an argon glove box, add NaB(OCHC2F6)4 and Mg[B(OCHC2F6)4]2 to DME in a molar ratio of 2:1 to prepare a boron-based electrolyte with a sodium ion concentration of 0.6 mol / L and a magnesium ion concentration of 0.3 mol / L for standby;

[0054] (5) Assemble the cathode sheet, anode sheet, boron-based electrolyte, and glass fiber separator into a CR2032 coin-type rechargeable magnesium-based battery according to the conventional method.

[0055] Example 3

[0056] (1) Dissolve 0.34 g of MnCl2 and 0.048 g of FeCl3 in 50 ml of deionized water to form Solution A, and dissolve 1.45 g of Na4Fe(CN)6·10H2O and 0.7 g of NaCl in 100 ml of deionized water to form Solution B; at 25 °C with magnetic stirring, slowly add Solution A dropwise to Solution B and continue stirring for 12 h, then centrifuge and wash three times with deionized water and once with alcohol to obtain a light blue precipitate. After that, dry the precipitate at 60 °C for 24 h, and then vacuum dry at 120 °C for 24 h to obtain the cathode material Na 1.9 Mn 0.9 Fe 0.1 [Fe(CN)6]0.9 ;

[0057] (2)Disperse the cathode material Na 1.9 Mn 0.9 Fe 0.1 [Fe(CN)6] 0.9 , conductive carbon black and binder PVDF in a mass ratio of 7:2:1 in NMP solvent, stir for 12 h to obtain a uniformly mixed cathode slurry. Then, uniformly coat the cathode slurry on Al foil, and vacuum dry at 60 °C for 5 h. After cutting into pieces to obtain the cathode sheet, quickly transfer it to an argon glove box for standby;

[0058] (3) Polish the surface of 0.7 mm thick magnesium gadolinium alloy with 800-mesh and 1500-mesh sandpaper until it is shiny, wipe off the ground powder with lint-free paper, cut it into a certain size and put it into an argon glove box for standby;

[0059] (4) Add NaB(OCHC2F6)4 and Mg[B(OCHC2F6)4]2 into DME in a molar ratio of 2:1 in the argon glove box to prepare a boron-based electrolyte with a sodium ion concentration of 0.6 mol / L and a magnesium ion concentration of 0.3 mol / L for standby;

[0060] (5) Assemble the cathode sheet, anode sheet, boron-based electrolyte and glass fiber separator into a CR2032 coin-type rechargeable magnesium-based battery according to the conventional method.

[0061] Example 4

[0062] (1) Dissolve 0.3775 g of MnCl2 in 50 ml of deionized water to form solution A, and dissolve 3.8015 g of K4Fe(CN)6·10H2O in 100 ml of deionized water to form solution B; at 25 °C and under magnetic stirring, slowly drop solution A into solution B and continue stirring for 12 h. Then, centrifuge and wash with deionized water three times and with alcohol once to obtain a light blue precipitate. After that, dry the precipitate at 60 °C for 24 h, and then vacuum dry at 120 °C for 24 h to obtain the cathode material K 1.9 Mn[Fe(CN)6] 0.9 ;

[0063] (2) Disperse the cathode material K 1.9 Mn[Fe(CN)6] 0.9 , conductive carbon black and binder PVDF in a mass ratio of 7:2:1 in NMP solvent, stir for 12 h to obtain a uniformly mixed cathode slurry. Then, uniformly coat the cathode slurry on Al foil, and vacuum dry at 60 °C for 5 h. After cutting into pieces to obtain the cathode sheet, quickly transfer it to an argon glove box for standby;

[0064] (3) Polish the surface of the 50-μm-thick magnesium foil until it is shiny with 800-mesh and 1500-mesh sandpaper, wipe off the ground powder with lint-free paper, cut it into a certain size and place it in an argon glove box for standby;

[0065] (4) In an argon glove box, add NaB(OCHC2F6)4 and Mg[B(OCHC2F6)4]2 to DME in a molar ratio of 2:1 to prepare a boron-based electrolyte with a sodium ion concentration of 0.3 mol / L and a magnesium ion concentration of 0.3 mol / L for standby;

[0066] (5) Assemble the positive electrode sheet, negative electrode sheet, boron-based electrolyte and glass fiber separator into a CR2032 coin-type rechargeable magnesium-based battery according to the conventional method.

[0067] Comparative Example 1

[0068] (1) Disperse the positive electrode material Na 1.9 Mn[Fe(CN)6] 0.9 , conductive carbon black and binder PVDF in a mass ratio of 7:2:1 in NMP solvent, stir for 12 h to obtain a uniformly mixed positive electrode paste, then uniformly coat the positive electrode paste on Al foil, and vacuum dry at 60 °C for 5 h. After cutting into pieces, transfer the positive electrode sheet to an argon glove box for standby quickly;

[0069] (2) Polish the surface of the 50-μm-thick magnesium foil until it is shiny with 800-mesh and 1500-mesh sandpaper, wipe off the ground powder with lint-free paper, cut it into a certain size and place it in an argon glove box for standby;

[0070] (3) In an argon glove box, dissolve magnesium bis(hexamethyldisilazide), magnesium chloride and aluminum chloride in a molar ratio of 1:1:2 in ethylene glycol dimethyl ether to prepare an electrolyte with a magnesium ion concentration of 1.8 mol / L for standby;

[0071] (4) Assemble the positive electrode sheet, negative electrode sheet, electrolyte and glass fiber separator into a CR2032 coin-type magnesium-based battery according to the conventional method.

[0072] II. Characterization of the positive electrode material

[0073] Perform X-ray diffraction test, SEM test and thermogravimetric analysis on the positive electrode materials Na 1.9 Mn 0.9 Fe 0.1 [Fe(CN)6] 0.9 prepared in Example 1 and Example 3. The X-ray diffraction results are as shown in Figure 1 shown, the SEM test results are as shown in Figure 2 shown, and the thermogravimetric analysis results are as shown in Figure 3 shown;

[0074] The positive electrode material Na 1.9 Mn[Fe(CN)6] prepared in Example 2 and Example 4 0.9 was subjected to X-ray diffraction test, SEM test and thermogravimetric analysis. The X-ray diffraction results are as Figure 4 shown, the SEM test results are as Figure 5 shown, and the thermogravimetric analysis results are as Figure 6 shown.

[0075] III. Battery Performance Test

[0076] After the button cells assembled in Examples 1 to 4 and Comparative Example 1 were left standing for 12 h, they were tested using a Neware battery tester with a test current of 100 mAg -1 , and the charge and discharge cut-off voltages were 1.0 - 3.5 V; the test results are shown in Table 1 below.

[0077] Table 1 Performance test of button cells assembled in Examples 1 to 4 and Comparative Example 1

[0078]

[0079] The test results of the button cells in Examples 1 to 4 were plotted: The first charge and discharge curve of the button cell in Example 1 is as Figure 7 shown, and the cycle curve is as Figure 8 shown; the first charge and discharge curve of the button cell in Example 2 is as Figure 9 shown, and the cycle curve is as Figure 10 shown; the first charge and discharge curve of the button cell in Example 3 is as Figure 11 shown, and the cycle curve is as Figure 12 shown; the first charge and discharge curve of the button cell in Example 3 is as Figure 13 shown, and the cycle curve is as Figure 14 shown.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A high-voltage magnesium-based battery, characterized in that, It includes a positive electrode, a negative electrode and an electrolyte; the positive electrode includes a magnesium-based battery positive electrode material, and the magnesium-based battery positive electrode material has the chemical formula A x Mn y M 1-y [Fe(CN)6] z ·nH2O, where A is any one of Na, K, Mg and Ca, M is selected from any one of transition metals, 0 ≤ x ≤ 2, 0 < y < 1, 0 < z < 1, 0 ≤ n < 4; the electrolyte contains NaB(OCHC2F6)4 and Mg[B(OCHC2F6)4]2, and the molar ratio of NaB(OCHC2F6)4 to Mg[B(OCHC2F6)4]2 is (0 - 2.5):

1.

2. The high-voltage magnesium-based battery according to claim 1, characterized in that, The positive electrode material of the magnesium-based battery is Na 1.9 Mn 0.9 Fe 0.1 [Fe(CN)6] 0.9 or Na 1.9 Mn[Fe(CN)6] 0.9 。 3. The high-voltage magnesium-based battery according to claim 1 or 2, characterized in that, The preparation method of the positive electrode material for the magnesium-based battery includes: dissolving Mn 2+ salt and transition metal salt in water to obtain solution A, and dissolving sodium ferrocyanide hydrate or potassium ferrocyanide and metal salt in water to obtain solution B; mixing solution A and solution B, and centrifuging to obtain the positive electrode material for the magnesium-based battery; the metal salt is selected from any one of Na salt, K salt, Mg salt and Ca salt.

4. The high-voltage magnesium-based battery according to claim 1 or 2, characterized in that The positive electrode also includes a conductive agent and a binder, wherein the mass ratio of the magnesium-based battery positive electrode material, the conductive agent and the binder is (6.5-9.5):(0.3-2.5):(0.2-1).

5. The high-voltage magnesium-based battery according to claim 1 or 2, characterized in that, The solvent of the electrolyte is selected from one or a combination of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.

6. The high-voltage magnesium-based battery according to claim 4, wherein The solvent of the electrolyte is selected from one or a combination of tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.

7. The high-voltage magnesium-based battery according to claim 1, 2 or 6, characterized in that, The negative electrode is selected from magnesium foil or magnesium alloy.

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