A high voltage magnesium-prussian blue battery

Abstract

The application belongs to the technical field of magnesium battery, and particularly relates to a high-voltage magnesium-prussian blue battery. The application can significantly improve the discharge voltage equalization and energy density of the rechargeable magnesium metal battery by preparing the rechargeable magnesium metal battery (i.e. the high-voltage magnesium-prussian blue battery) from the sodium-containing prussian blue compound and the magnesium / sodium mixed electrolyte. The discharge voltage equalization of the prepared high-voltage magnesium-prussian blue battery is up to 2.70 V, and the energy density is up to 360 Wh / kg, which is much higher than that of the existing magnesium ion battery and close to or higher than that of some sodium ion batteries. Meanwhile, the prussian blue positive electrode material with a stable three-dimensional framework structure makes the capacity retention rate of the battery after 100 cycles at 1C reach 82.21%, and the battery exhibits excellent cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of magnesium battery technology, specifically relating to a high-voltage magnesium-Prussian blue battery. Background Technology

[0002] Lithium-ion batteries, with their high energy density and long cycle life, have been widely used in electric vehicles, renewable energy storage, and portable electronic products over the past decade. However, with the increasing global demand for efficient and sustainable energy storage systems, issues such as limited lithium reserves, rising costs, and safety concerns have become increasingly prominent, urgently requiring the development of alternative battery technologies to overcome these limitations. Magnesium-ion batteries, due to the high theoretical specific capacity (2205 mAh / g), low reduction potential, low dendrite growth risk of the magnesium anode, and the abundant and inexpensive magnesium resources, are considered a promising rechargeable battery system.

[0003] Despite the significant advantages of magnesium-ion batteries in terms of safety and cost, currently developed rechargeable magnesium metal batteries generally suffer from low operating voltages. The vast majority of magnesium-ion batteries operate below 3V, a considerable gap compared to the 3.65V and above operating voltages of current lithium / sodium-ion batteries. Furthermore, the lack of a suitable cathode material that can operate stably at high voltages and possesses high capacity is a major obstacle to achieving high-capacity magnesium-ion battery performance. 2+ The efficient and reversible insertion and extraction of magnesium ion batteries is crucial for achieving optimal performance. Existing magnesium ion batteries often struggle to balance capacity and cycle performance, resulting in low energy density, poor cycle stability, and severely limited practicality.

[0004] Therefore, how to effectively improve the energy density and operating voltage of rechargeable magnesium metal batteries, while simultaneously improving their cycle stability, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] Therefore, the present invention aims to provide a high-voltage magnesium-Prussian blue battery. The present invention uses sodium-containing Prussian blue compounds as the positive electrode active material to prepare a rechargeable magnesium metal battery (i.e., a high-voltage magnesium-Prussian blue battery), which features high operating voltage, high energy density, and good cycle performance.

[0006] To achieve the above objectives, the present invention can adopt the following technical solutions:

[0007] This invention provides a high-voltage magnesium-Prussian blue battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator. The active material of the positive electrode is a Prussian blue compound, the crystal structure of which contains sodium ions. The electrolyte contains magnesium salt and sodium salt. The sodium salt is selected from one or more combinations of sodium tetra(hexafluoroisopropoxy)borate, sodium tetra(perfluorotert-butyl)borate, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide.

[0008] Preferably, in the above-mentioned high-voltage magnesium-Prussian blue battery, the molecular formula of the Prussian blue compound is Na. 2- x Fe a Mn b Cu c [Fe(CN)6], wherein 0≤x≤1, 0.3≤a≤0.65, 0.35≤b≤0.65, 0.03≤c≤0.15, and a+b+c=1. More preferably, in the above high-voltage magnesium-Prussian blue battery, the molecular formula of the Prussian blue compound is Na. 1.72 Fe 0.35 Mn 0.58 Cu 0.07 [Fe(CN)6] or Na 1.87 Fe 0.35 Mn 0.58 Cu 0.07 [Fe(CN)6].

[0009] Preferably, in the above-mentioned high-voltage magnesium-Prussian blue battery, the magnesium salt in the electrolyte is one or a combination of magnesium tetra(hexafluoroisopropoxy)borate and magnesium tetra(perfluorotert-butyl)borate in any proportion.

[0010] Preferably, in the above-mentioned high-voltage magnesium-Prussian blue battery, the molar ratio of magnesium salt to sodium salt in the electrolyte is 1:0.5 to 1:0.99.

[0011] Preferably, in the above-mentioned high-voltage magnesium-Prussian blue battery, the non-aqueous solvent of the electrolyte is one or more combinations of ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (G2), triethylene glycol dimethyl ether (G3), tetraethylene glycol dimethyl ether (G4), acetonitrile, propionitrile, tetrahydrofuran (THF), 2-methyltetrahydrofuran, or 2,2,2-trifluoroethyl ether.

[0012] More preferably, in the above-mentioned high-voltage magnesium-Prussian blue battery, the negative electrode is a magnesium foil, a magnesium alloy foil, or a magnesium-copper plated foil; and / or the current collector in the positive electrode is an aluminum foil or a carbon-coated aluminum foil, the conductive agent is one or more of Super-P, Ketjen black, acetylene black, carbon nanotubes, or graphene, the binder is one or more of PVDF, CMC, PTFE, or SBR; and / or the separator is a glass fiber separator, a PP separator, a PE separator, or a composite separator of PP and PE.

[0013] In another aspect, the present invention provides a Prussian blue compound with the molecular formula Na. 1.72 Fe 0.35 Mn 0.58 Cu 0.07 [Fe(CN)6] or Na 1.87 Fe0.35 Mn 0.58 Cu 0.07 [Fe(CN)6].

[0014] In another aspect, the present invention provides a method for preparing the above-mentioned Prussian blue compounds. The method includes: dissolving sodium ferrocyanide in water as a first solution; dissolving a transition metal salt containing iron, manganese, and copper salts in water as a second solution; dissolving a sodium-containing salt in water as a base solution, wherein the sodium-containing salt is sodium chloride and / or sodium citrate; mixing the first solution, the second solution, and the base solution, and then aging, centrifuging, and drying to obtain the Prussian blue compounds.

[0015] In another aspect, the present invention provides the application of the above-mentioned Prussian blue compounds as positive electrode active materials in high-voltage magnesium-Prussian blue batteries.

[0016] The beneficial effects of this invention include at least the following: By preparing a high-voltage magnesium-Prussian blue battery using sodium-containing Prussian blue compounds and a sodium-containing electrolyte, this invention can significantly improve the discharge voltage and energy density of the high-voltage magnesium-Prussian blue battery. The high-voltage magnesium-Prussian blue battery prepared can achieve a discharge voltage of up to 2.70V and an energy density of 360Wh / kg, which is far higher than that of existing magnesium battery systems using Prussian blue materials as positive electrode active materials (energy density of about 200Wh / kg), and is close to or higher than that of some sodium-ion batteries; at the same time, it uses Prussian blue-based positive electrode materials with a stable three-dimensional framework structure (such as Na+). 2-x Fe a Mn b Cu c [Fe(CN)6], where 0≤x≤1, 0.3≤a≤0.65, 0.35≤b≤0.65, 0.03≤c≤0.15, a+b+c=1), makes the battery retain a capacity of up to 82.21% after 100 cycles at 1C, demonstrating excellent cycle stability. Attached Figure Description

[0017] Figure 1 The charge-discharge curves of the rechargeable magnesium metal battery of Example 1 are shown at a current density of 0.1C (1C=120mA / g) and a voltage range of 1.0V to 3.65V.

[0018] Figure 2 The cycling performance curve of the rechargeable magnesium metal battery in Example 1 at a current density of 1C is shown.

[0019] Figure 3 The charge-discharge curves of the rechargeable magnesium metal battery of Example 2 are shown at a current density of 0.1C and a voltage range of 1.0 to 3.65V.

[0020] Figure 4The charging and discharging curves of the rechargeable magnesium metal battery of Example 3 are shown at a current density of 0.1C and a voltage range of 1.0 to 3.65V. Detailed Implementation

[0021] The illustrated embodiments are provided to better illustrate the present invention, but are not intended to limit the scope of the invention to the illustrated embodiments. Therefore, non-essential improvements and adjustments made to the embodiments by those skilled in the art based on the above description of the invention still fall within the protection scope of the present invention.

[0022] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. Singular expressions include plural expressions unless they have a distinct meaning in the context. As used herein, it should be understood that terms such as “comprising,” “having,” “including,” are intended to indicate the presence of features, numbers, operations, components, parts, elements, materials, or combinations thereof. The terminology of the invention is disclosed in the specification and is not intended to exclude the possibility that one or more other features, numbers, operations, components, parts, elements, materials, or combinations thereof may be present or added. As used herein, “ / ” may be interpreted as “and” or “or,” depending on the context.

[0023] In a first aspect, embodiments of the present invention provide a high-voltage magnesium-Prussian blue battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator. The active material of the positive electrode is a Prussian blue compound, the crystal structure of which contains sodium ions. The electrolyte contains magnesium salts and sodium salts. The sodium salt is selected from one or more combinations of sodium tetra(hexafluoroisopropoxy)borate, sodium tetra(perfluorotert-butyl)borate, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide.

[0024] It should be noted that this invention prepares a high-voltage magnesium-Prussian blue battery by combining sodium-containing Prussian blue compounds with a sodium-containing electrolyte, which can significantly improve the discharge voltage and energy density of the high-voltage magnesium-Prussian blue battery. The high-voltage magnesium-Prussian blue battery prepared in this invention can achieve a discharge voltage of up to 2.70V and an energy density of 360Wh / kg, which is far higher than the existing magnesium battery system using Prussian blue materials as the positive electrode active material (energy density of about 200Wh / kg), and is close to or higher than some sodium-ion batteries. At the same time, by using Prussian blue-based positive electrode materials with a stable three-dimensional framework structure, the battery achieves a capacity retention rate of up to 82.21% after 100 cycles at 1C, exhibiting excellent cycle stability. The sodium salt can preferably be sodium tetra(hexafluoroisopropoxy)borate, sodium tetra(perfluorotert-butyl)borate, or sodium trifluoromethanesulfonate, etc., which are suitable for magnesium salt systems, and have both ionic conductivity and interface modification effects. It can improve the overall performance of the electrolyte whether used alone or in combination.

[0025] In some specific examples, in the aforementioned high-voltage magnesium-Prussian blue battery, the molecular formula of the Prussian blue compound is Na. 2-x Fe a Mn b Cu c [Fe(CN)6], where 0≤x≤1, 0.3≤a≤0.65, 0.35≤b≤0.65, 0.03≤c≤0.15, and a+b+c=1.

[0026] It should be noted that the ratio of elements in the Prussian blue molecular formula can balance crystal stability, sodium content, and electrochemical activity. Furthermore, Prussian blue compounds utilize abundant Fe, Mn, and Cu elements found in the Earth's crust, resulting in low cost. The co-precipitation preparation process is simple and compatible with existing battery material production lines. Moreover, the magnesium anode is less prone to dendrite formation, offering high safety and environmental friendliness. Therefore, this invention effectively overcomes the shortcomings of existing magnesium-ion batteries, such as low operating voltage, low energy density, and poor cycle stability, providing a practical and feasible technical solution for the practical application of magnesium-ion batteries.

[0027] In some specific examples, in the aforementioned high-voltage magnesium-Prussian blue battery, the molecular formula of the Prussian blue compound is Na. 1.72 Fe 0.35 Mn 0.58 Cu 0.07 [Fe(CN)6] or Na 1.87 Fe 0.35 Mn 0.58 Cu 0.07 [Fe(CN)6].

[0028] In some specific examples, the molar ratio of magnesium salt to sodium salt in the electrolyte of the above-mentioned high-voltage magnesium-Prussian blue battery is 1:0.5 to 1:0.99.

[0029] It should be noted that the molar ratio of magnesium salt to sodium salt in the electrolyte can be 1:0.5, 1:0.6, 1:0.7 or 1:0.8, etc. A small amount of sodium salt can play a synergistic modification role. This ratio range takes into account ionic conductivity, interfacial kinetics and magnesium deposition safety, and is the optimal compound ratio of electrolyte.

[0030] In some specific examples, in the above-mentioned high-voltage magnesium-Prussian blue battery, the magnesium salt in the electrolyte is one or a combination of magnesium tetra(hexafluoroisopropoxy)borate and magnesium tetra(perfluorotert-butyl)borate in any proportion.

[0031] It should be noted that the magnesium salt in this invention can preferably be one of magnesium tetra(hexafluoroisopropoxy)borate and magnesium tetra(perfluorotert-butyl)borate or a combination thereof in any proportion. It has good solubility and high electrochemical stability, can suppress magnesium anode passivation, and is more suitable for the high-voltage magnesium-Prussian blue battery system of this invention.

[0032] In some specific examples, in the above-mentioned high-voltage magnesium-Prussian blue battery, the non-aqueous solvent of the electrolyte is one or more combinations of ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (G2), triethylene glycol dimethyl ether (G3), tetraethylene glycol dimethyl ether (G4), acetonitrile, propionitrile, tetrahydrofuran (THF), 2-methyltetrahydrofuran, or 2,2,2-trifluoroethyl ether.

[0033] It should be noted that non-aqueous solvents can preferably be ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, etc. Ether solvents have good solubility for magnesium / sodium salts, a wide electrochemical window, and strong compatibility with magnesium anodes. Single or compound solvents can adjust the electrolyte viscosity and ionic conductivity to meet the battery operation requirements at different temperatures and ensure rapid ion transport.

[0034] In some specific examples, in the above-mentioned high-voltage magnesium-Prussian blue battery, the negative electrode is a magnesium foil, magnesium alloy foil, or magnesium-copper foil; and / or the current collector in the positive electrode is an aluminum foil or a carbon-coated aluminum foil, the conductive agent is one or more combinations of Super-P, Ketjen black, acetylene black, carbon nanotubes, and graphene, the binder is one or more combinations of PVDF, CMC, PTFE, and SBR; and / or the separator is a glass fiber separator, a PP separator, a PE separator, or a composite separator of PP and PE.

[0035] It should be noted that the negative electrode can preferably be magnesium foil, magnesium alloy foil, or magnesium-copper foil, which have high capacity, low potential, and good processability; the positive electrode current collector can preferably be aluminum foil or carbon-coated aluminum foil; the conductive agent can preferably be Super-P, carbon nanotubes, graphene, etc.; and the binder can preferably be PVDF, SBR, etc., to ensure the conductivity and structural stability of the positive electrode; the separator can preferably be glass fiber separator, PP / PE composite separator, etc., which are resistant to electrolyte corrosion, block the positive and negative electrodes, prevent short circuits, and are suitable for the safe and stable operation of magnesium battery systems.

[0036] In some specific examples, in the above-mentioned high-voltage magnesium-Prussian blue battery, the mass ratio of positive electrode active material, conductive agent and binder in the positive electrode is 7:2:1, 8:1:1 or other positive electrode active material accounts for ≥70%, conductive agent accounts for ≥3%, binder accounts for ≥3% in any proportion, the solvent is NMP, and generally the binder is preferably mixed with NMP solvent to form a gel.

[0037] In some specific examples, in the above-mentioned high-voltage magnesium-Prussian blue battery, the oxide layer on the surface of the negative electrode can be treated with a low-concentration dilute acid, which is one or more combinations of dilute hydrochloric acid, dilute sulfuric acid, and dilute nitric acid.

[0038] Secondly, embodiments of the present invention provide a Prussian blue compound with the molecular formula Na. 1.72 Fe 0.35 Mn 0.58 Cu 0.07 [Fe(CN)6] or Na 1.87 Fe 0.35 Mn 0.58 Cu 0.07 [Fe(CN)6].

[0039] Thirdly, embodiments of the present invention provide a method for preparing the above-mentioned Prussian blue compounds. The method includes: dissolving sodium ferrocyanide in water as a first solution; dissolving a transition metal salt containing iron, manganese, and copper salts in water as a second solution; dissolving a sodium-containing salt in water as a base solution, wherein the sodium-containing salt is sodium chloride and / or sodium citrate; mixing the first solution, the second solution, and the base solution, and obtaining the Prussian blue compounds after aging, centrifugation, and drying.

[0040] It should be noted that the present invention uses a co-precipitation method, which has mild process conditions, simple operation, and is easy to scale up. The prepared compound has high purity, complete crystal structure, uniform sodium distribution, and stable and controllable electrochemical performance.

[0041] Fourthly, embodiments of the present invention provide an application of the above-mentioned Prussian blue compounds as positive electrode active materials in high-voltage magnesium-Prussian blue batteries.

[0042] It should be noted that the Prussian blue compound in this invention is suitable for high-voltage magnesium-Prussian blue battery cathodes, possessing high voltage, high discharge equalization voltage, excellent cycle stability, and ionic conductivity; it can significantly improve battery energy density and extend service life, making it suitable for applications such as energy storage and power batteries, with significant industrial application value.

[0043] To better understand the present invention, specific examples are provided below to further illustrate the content of the present invention, but the content of the present invention is not limited to the examples below.

[0044] Preparation Example

[0045] Example 1

[0046] (1) Synthesis of positive electrode active material (Prussian blue compounds)

[0047] Prussian blue-based compound cathode active materials were synthesized using a co-precipitation method, as detailed below:

[0048] 1) Preparation of the first solution: Dissolve 3.65g of anhydrous sodium ferrocyanide (Na4Fe(CN)6) in 30mL of pure water and stir until homogeneous.

[0049] 2) Preparation of the second solution: Dissolve 0.639g ferrous sulfate (FeSO4), 1.245g manganese nitrate (Mn(NO3)2) and 0.208g copper sulfate pentahydrate (CuSO4·5H2O) in 30mL of pure water and stir well.

[0050] 3) Preparation of the base solution: Dissolve 7.3g of sodium chloride (NaCl) in 50mL of pure water and stir well.

[0051] Under stirring, the first and second solutions were slowly and continuously added dropwise to the base liquid. After the addition was complete, the reaction solution was allowed to stand and age for 8 hours. Then, the solution was washed three times by centrifugation with deionized water and anhydrous ethanol to obtain a precipitate. The precipitate was vacuum dried at 150°C for 16 hours to obtain a Prussian blue-like material with the molecular formula Na. 1.72 Fe 0.35 Mn 0.58 Cu 0.07 [Fe(CN)6].

[0052] (2) Preparation of positive electrode sheet

[0053] The above-mentioned positive electrode active material, conductive agent Super-P, and binder PVDF were weighed at a mass ratio of 7:2:1. First, the binder was mixed with NMP solvent to prepare a 0.018 g / mL adhesive solution. Then, the positive electrode active material and conductive agent were added, and the mixture was stirred until homogeneous to obtain the positive electrode slurry. The positive electrode slurry was uniformly coated onto the positive electrode current collector aluminum foil, dried at 120°C for 10 hours, rolled, and cut into sheets to obtain the positive electrode sheet, which was then packaged for later use.

[0054] (3) Treatment of negative electrode sheet

[0055] Magnesium foil is soaked in low-concentration dilute hydrochloric acid to remove the oxide layer on the surface, then cleaned with anhydrous ethanol, vacuum dried at 60°C, cut into appropriate sizes, and packaged for later use.

[0056] (4) Preparation of electrolyte

[0057] In an argon-filled glove box, magnesium tetra(hexafluoroisopropoxy)borate (Mg[B(hfip)4]2) and dimethyl ethylene glycol (DME) solvent were mixed to prepare an electrolyte solution with a concentration of 0.3 mol / L for later use.

[0058] (5) Battery assembly

[0059] The above-mentioned positive electrode, negative electrode, electrolyte, and GF / F glass fiber separator are assembled into a coin cell using a CR2032 positive and negative electrode battery case, a spring, and a gasket, thus completing the preparation of a rechargeable magnesium metal battery.

[0060] Example 2

[0061] Example 2 is largely the same as Example 1, except that in the preparation of the base solution in step (1) of Example 1, 20 wt% sodium citrate (i.e., the mass of sodium citrate is 20% of the mass of sodium chloride) is added. Otherwise, it is the same as Example 1. The molecular formula of the Prussian blue-like material obtained is Na. 1.87 Fe 0.35 Mn 0.58 Cu 0.07 [Fe(CN)6].

[0062] Example 3

[0063] Example 3 is largely the same as Example 2, except that in the electrolyte preparation process in step (4) of Example 2, magnesium tetra(hexafluoroisopropoxy)borate and sodium tetra(hexafluoroisopropoxy)borate are prepared in a molar ratio of 1:0.5 to form an electrolyte with a concentration of 0.3 mol / L. The rest is the same as in Example 1.

[0064] Performance testing

[0065] (1) Electrochemical performance testing methods

[0066] The assembled coin cells were left to stand at room temperature for 12 hours, and then charge-discharge tests were conducted at 20℃~30℃ using a coin cell testing system. The test voltage range was 1.0V~3.65V. The current density was set to 0.1C (1C=120mA / g) and 1C, and constant current constant voltage charge-discharge tests and cycle performance tests were performed respectively.

[0067] The charge-discharge curves of the rechargeable magnesium metal battery prepared in Example 1 at a current density of 0.1C were tested, and the results are as follows: Figure 1 As shown, the results indicate that the rechargeable magnesium metal battery exhibits a smooth charge-discharge platform within the voltage range of 1.0V to 3.65V, with a discharge specific capacity of 133.59mAh / g and a discharge average voltage of 2.28V.

[0068] The cycle performance curves of the rechargeable magnesium metal battery prepared in Example 1 at a 1C current density are shown below. Figure 2 As shown, the results indicate that the rechargeable magnesium metal battery retains 82.21% of its capacity after 100 cycles at 1C rate, and the capacity decay is gradual throughout the cycle, indicating that the battery has good cycle stability.

[0069] The charge-discharge curves of the rechargeable magnesium metal battery prepared in Example 2 at a current density of 0.1C were tested, and the results are as follows: Figure 3 As shown, compared with Example 1, the discharge plateau of Example 2 shifts upward to approximately 2.4–2.5V, indicating that increasing the sodium content in the cathode material can effectively improve the discharge voltage. Its discharge specific capacity is 131.75 mAh / g, the average discharge voltage is 2.47V, and the energy density is 325Wh / kg.

[0070] The charge-discharge curves of the rechargeable magnesium metal battery prepared in Example 3 at a current density of 0.1C were tested, and the results are as follows: Figure 4 As shown, compared with Examples 1 and 2, the discharge plateau of Example 3 is further shifted upward, and it exhibits a longer plateau region in the higher voltage range. Its discharge specific capacity is 133.02 mAh / g, the average discharge voltage is 2.70 V, and the energy density is 360 Wh / kg.

[0071] The discharge performance of the rechargeable magnesium metal batteries prepared in the examples is shown in Table 1 below.

[0072] Table 1 Electrochemical performance of the rechargeable magnesium metal batteries prepared in the examples

[0073] Example 1 133.59 2.28 305 Example 2 131.75 2.47 325 Example 3 133.02 2.70 360

[0074] From Table 1 above and Figures 1 to 4 It can be concluded that:

[0075] Comparing Examples 1, 2, and 3, it can be seen that with the increase of sodium content in the battery system, both the discharge voltage and energy density show a significant upward trend. Specifically, Example 1 (low-sodium cathode material, sodium-free electrolyte) has a discharge voltage of 2.28V and an energy density of 305Wh / kg; Example 2 (high-sodium cathode material, sodium-free electrolyte) has a discharge voltage increased to 2.47V (an increase of approximately 0.19V) and an energy density increased to 325Wh / kg (an increase of approximately 20Wh / kg); Example 3 (high-sodium cathode material + sodium-containing electrolyte) has a discharge voltage further increased to 2.70V (an increase of 0.23V compared to Example 2) and an energy density of 360Wh / kg (an increase of 35Wh / kg compared to Example 2). The above results indicate that increasing the sodium content in the cathode material and adding sodium salts to the electrolyte can effectively improve the average discharge voltage and energy density of the battery. The mechanism is that the excess sodium ions participate in the discharge reaction during the high-voltage stage of the battery, thereby increasing the average voltage of the entire discharge process.

[0076] 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 it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-voltage magnesium-Prussian blue battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator, characterized in that, The positive electrode is a Prussian blue-like compound with the molecular formula Na. 2-x Fe a Mn b Cu c [Fe(CN)6], where 0≤x≤1, 0.3≤a≤0.65, 0.35≤b≤0.65, 0.03≤c≤0.15, a+b+c=1; and The electrolyte contains magnesium and sodium salts; The sodium salt is selected from one or more combinations of sodium tetra(hexafluoroisopropoxy)borate, sodium tetra(perfluorotert-butyl)borate, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethanesulfonyl)imide.

2. The high-voltage magnesium-Prussian blue battery according to claim 1, characterized in that, The molecular formula of Prussian blue compounds is Na. 1.72 Fe 0.35 Mn 0.58 Cu 0.07 [Fe(CN)6] or Na 1.87 Fe 0.35 Mn 0.58 Cu 0.07 [Fe(CN)6].

3. The rechargeable magnesium metal battery according to claim 1, characterized in that, The magnesium salt in the electrolyte is one of magnesium tetra(hexafluoroisopropoxy)borate and magnesium tetra(perfluorotert-butyl)borate, or a combination thereof in any proportion.

4. The high-voltage magnesium-Prussian blue battery according to claim 1, characterized in that, The molar ratio of magnesium salt to sodium salt in the electrolyte is 1:0.5 to 1:0.

99.

5. The high-voltage magnesium-Prussian blue battery according to any one of claims 1 to 4, characterized in that, The non-aqueous solvent of the electrolyte is one or a combination of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, or 2,2,2-trifluoroethyl ether.

6. The high-voltage magnesium-Prussian blue battery according to any one of claims 1 to 4, characterized in that, The negative electrode is a magnesium foil, magnesium alloy foil, or magnesium-copper plated foil; and / or The current collector in the positive electrode is aluminum foil or carbon-coated aluminum foil; the conductive agent is one or more combinations of Super-P, Ketjen Black, acetylene black, carbon nanotubes, or graphene; and the binder is one or more combinations of PVDF, CMC, PTFE, or SBR; and / or The diaphragm is a glass fiber diaphragm, PP diaphragm, PE diaphragm, or a composite diaphragm of PP and PE.

7. A Prussian blue compound, characterized in that, Its molecular formula is Na 1.72 Fe 0.35 Mn 0.58 Cu 0.07 [Fe(CN)6] or Na 1.87 Fe 0.35 Mn 0.58 Cu 0.07 [Fe(CN)6].

8. The method for preparing the Prussian blue compound according to claim 7, characterized in that, Preparation methods include: Sodium ferrocyanide was dissolved in water to form the first solution; A transition metal salt containing iron, manganese, and copper salts is dissolved in water to form a second solution; A sodium-containing salt is dissolved in water to form a base solution, wherein the sodium-containing salt is sodium chloride and / or sodium citrate; The first solution, the second solution, and the base liquid were mixed, aged, centrifuged, and dried to obtain Prussian blue compounds.

9. The use of the Prussian blue compounds of claim 8 as positive electrode active materials in high-voltage magnesium-Prussian blue batteries.

Images