Magnesium-based dual-ion battery as well as preparation method and application thereof

Abstract

The invention discloses a magnesium-based dual-ion battery and a preparation method and application thereof.According to the magnesium-based dual-ion battery, a battery configuration with magnesium metal as a negative electrode and a graphite material as a positive electrode is constructed, and a cation intercalation behavior in a traditional magnesium battery is replaced with an anion intercalation mechanism; the collaborative design of the ionic liquid electrolyte and the mixed magnesium salt is specifically adopted, the magnesium deposition interface is effectively regulated and controlled, and the performance obviously superior to that of a traditional magnesium battery is achieved. Through the working mechanism of the dual-ion battery, the advantages of high working voltage of the graphite positive electrode and high capacity of the magnesium metal negative electrode are combined, and the wide electrochemical window of the ionic liquid electrolyte is utilized, so that long-life deposition can be realized under low overpotential; meanwhile, through high-capacity and high-rate intercalation reaction of anions in the graphite positive electrode, the problems of narrow voltage window, flammability and explosiveness, short cycle life, low positive electrode capacity, low positive electrode voltage and the like of the current magnesium ion battery are effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a magnesium-based dual-ion battery, its preparation method, and its application. Background Technology

[0002] The emergence of lithium-ion batteries, with their high energy density and long cycle life, has rapidly propelled the development of smartphones, laptops, electric vehicles, and other fields. However, lithium's abundance in the Earth's crust is only about 20 ppm, and its distribution is uneven. The ever-increasing demand and scarce resources have caused lithium prices to skyrocket, limiting the large-scale application of lithium-ion batteries. Therefore, it is necessary to develop new energy storage devices based on abundant and inexpensive metal ions. Among these, magnesium is abundant (seventh in abundance in the Earth's crust) and has a high volumetric capacity (3833 mAh cm⁻¹). -3 ) and specific capacity (2205 mAhg) -1 Magnesium batteries possess advantages such as low standard potential (-2.37 V vs. SHE) and no dendrite growth, making them a promising next-generation low-cost energy storage device. However, the development of magnesium batteries faces the following bottlenecks: 1. The magnesium metal anode is incompatible with traditional aprotic solvents. During cycling, traditional aprotic solvents, such as carbonate solvents, form a passivation layer on the surface of the magnesium metal anode that insulates against magnesium ions. This prevents reversible deposition / dissolution of magnesium ions on the magnesium metal anode surface. 2. The small ionic radius and high charge density of magnesium ions result in strong electrostatic interactions between magnesium ions and the anionic framework in the cathode material. Only a small amount of material can reversibly insert / extract magnesium ions. Furthermore, the strong electrostatic interaction leads to poor diffusion kinetics of magnesium ions in the cathode material, limiting the battery's rate performance. Currently, magnesium-ion batteries generally use intercalated cathode materials, whose working mechanism is based on the extraction / insertion reaction of magnesium ions during charging and discharging. However, due to the strong electrostatic interaction caused by its divalent nature, the reversible insertion / extraction of magnesium ions in the cathode lattice framework is severely restricted, resulting in a scarcity of available cathode materials and the common problems of low operating voltage and insufficient specific capacity, which restricts the overall energy density of the battery. Summary of the Invention

[0003] To overcome the problems existing in the prior art, one objective of this invention is to provide a magnesium-based dual-ion battery. A second objective of this invention is to provide a method for preparing the aforementioned magnesium-based dual-ion battery. A third objective of this invention is to provide an electrical device.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a magnesium-based dual-ion battery, the magnesium-based dual-ion battery comprising a positive electrode, a negative electrode and an electrolyte; The active material of the positive electrode includes graphite-based materials; the negative electrode includes magnesium metal.

[0005] The electrolyte includes magnesium salts and ionic liquids.

[0006] In this invention, the magnesium-based dual-ion battery uses a dual-ion electrolyte composed of magnesium salt and ionic liquid. It utilizes a more kinetic anion intercalation process instead of traditional magnesium ion intercalation. In this dual-ion battery structure, anions from both the ionic liquid and the dissociated magnesium salt can be intercalated and deintercalated at the graphite cathode, significantly improving rate performance. Furthermore, the ionic liquid exhibits high reduction stability and is less prone to decomposition reactions on the magnesium metal anode surface, thus significantly reducing the formation of a passivation film on the magnesium metal surface. In this invention, the positive electrode active material is a novel graphite-based material, replacing the traditional cation-intercalated cathode material. Graphite materials possess sp... 2 The delocalized π-electron system formed by the hybrid carbon layer can be oxidized under high voltage, losing electrons and carrying a positive charge. Anions can reversibly intercalate between graphite layers under the influence of electric field and electrostatics. The anion intercalation reaction exhibits pseudocapacitive properties, and its reaction kinetics are significantly superior to those of magnesium ions in electrode materials. Therefore, this invention, combining the synergistic design of graphite cathode material, ionic liquid electrolyte, and magnesium salt, can effectively solve the problems of low cathode capacity, low voltage, poor rate performance, and mismatch between the negative electrode and electrolyte in existing magnesium-ion batteries. This enables the realization of magnesium-based energy storage devices with high energy density, long cycle life, and high safety, promoting the development of low-cost, high-performance battery technology.

[0007] Preferably, the magnesium salt includes at least one of magnesium chloride, magnesium nitrate, magnesium fluoride, magnesium bromide, magnesium iodide, magnesium sulfate, magnesium bis(trifluoromethanesulfonyl)imide, magnesium tetrafluoroborate, magnesium hexafluorophosphate, and magnesium perchlorate.

[0008] More preferably, the magnesium salt includes magnesium chloride and magnesium bis(trifluoromethanesulfonyl)imide, or further includes at least one of magnesium nitrate, magnesium fluoride, magnesium bromide, magnesium iodide, magnesium sulfate, magnesium tetrafluoroborate, magnesium hexafluorophosphate, and magnesium perchlorate.

[0009] More preferably, the molar ratio of magnesium chloride to magnesium bis(trifluoromethanesulfonyl)imide is 1:(0.1-10). For example, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.5, 1:2.

[0010] This invention uses a mixed magnesium salt of magnesium chloride and magnesium bis(trifluoromethanesulfonyl)imide, which can achieve low-potential magnesium deposition and provide anions for intercalating graphite. The resulting battery has a magnesium deposition active voltage as low as 0.2V and a cycle life of up to 2000 h.

[0011] Preferably, the ionic liquid includes at least one of pyrrolidine ionic liquids, piperidine ionic liquids, quaternary ammonium salt ionic liquids, quaternary phosphonium salt ionic liquids, and pyridine ionic liquids.

[0012] More preferably, the ionic liquid comprises N,N,N-tris-(2-(2-methoxyethoxy)ethyl)-N-(2-methoxyethoxy)amino-bis(trifluoromethanesulfonyl)imine salt (abbreviated as N... O7 TFSI), N,N,N-tris-(2-(2-methoxyethoxy)ethyl)-N-(2-methoxyethoxy)amino-hexafluorophosphate (abbreviated as N O7 PF6), N,N,N-tri-(2-(2-methoxyethoxy)ethyl)-N-(2-methoxyethoxy)amino-tetrafluoroborate (abbreviated as N) O7 BF4), N,N,N-tri-(2-(2-methoxyethoxy)ethyl)-N-(2-methoxyethoxy)ammonium chloride (abbreviated as N) O7Pip12TFSI, N-ethyl-N-methylpiperidine-bis(trifluoromethanesulfonyl)imine (abbreviated as Pip12TFSI), N-ethyl-N-methylpiperidine-hexafluorophosphate (abbreviated as Pip12PF6), N-ethyl-N-methylpiperidine tetrafluoroborate (abbreviated as Pip12BF4), N-ethyl-N-methylpiperidine chloride (abbreviated as Pip12Cl), N-propyl-N-methylpiperidine-bis(trifluoromethanesulfonyl)imine (abbreviated as Pip13TFSI), N-propyl-N-methylpiperidine-hexafluorophosphate (abbreviated as Pip13PF6), N-propyl-N-methylpiperidine tetrafluoroborate (abbreviated as Pip13BF4), N-propyl-N-methylpiperidine chloride (abbreviated as Pip1... 3Cl), N-butyl-N-methylpiperidine-bis(trifluoromethanesulfonyl)imide salt (abbreviated as Pip14TFSI), N-butyl-N-methylpiperidine-hexafluorophosphate (abbreviated as Pip14PF6), N-butyl-N-methylpiperidine tetrafluoroborate (abbreviated as Pip14BF4), N-butyl-N-methylpiperidine chloride salt (abbreviated as Pip14Cl), tetramethylammonium-bis(trifluoromethanesulfonyl)imide salt (abbreviated as N1111TFSI), tetramethylammonium-hexafluorophosphate (abbreviated as N1111PF6), tetramethylammonium tetrafluoroborate (abbreviated as N1111BF4), tetramethylammonium chloride salt (abbreviated as N1111Cl), tetraethylammonium-bis(trifluoromethanesulfonyl)imide salt (abbreviated as N2) Tetraethylammonium-hexafluorophosphate (N222PF6), tetraethylammonium tetrafluoroborate (N2222BF4), tetraethylammonium chloride (N2222Cl), tetrabutylammonium-bis(trifluoromethanesulfonyl)imide (N4444TFSI), tetrabutylammonium-hexafluorophosphate (N4444PF6), tetrabutylammonium tetrafluoroborate (N4444BF4), tetrabutylammonium chloride (N4444Cl), tetrabutylphosphonium-bis(trifluoromethanesulfonyl)imide (P4444TFSI), tetrabutylphosphonium-hexafluorophosphate (P4444PF6), tetrabutylphosphonium tetrafluoroborate (P4444BF4). Tetrabutylphosphonium chloride (P4444Cl), N-ethyl-N-methylpyrrolidine-bis(trifluoromethanesulfonyl)imine (Pyr12TFSI), N-ethyl-N-methylpyrrolidine-hexafluorophosphate (Pyr12PF6), N-ethyl-N-methylpyrrolidine tetrafluoroborate (Pyr12BF4), N-ethyl-N-methylpyrrolidine chloride (Pyr12Cl), N-propyl-N-methylpyrrolidine-bis(trifluoromethanesulfonyl)imine (Pyr13TFSI), N-propyl-N-methylpyrrolidine-hexafluorophosphate (Pyr13PF6), N-propyl-N-methylpyrrolidine tetrafluoroborate (Pyr13BF4)N-propyl-N-methylpyrrolidine chloride (abbreviated as Pyr13Cl), N-butyl-N-methylpyrrolidine-bis(trifluoromethanesulfonyl)imine (abbreviated as Pyr14TFSI), N-butyl-N-methylpyrrolidine-hexafluorophosphate (abbreviated as Pyr14PF6), N-butyl-N-methylpyrrolidine tetrafluoroborate (abbreviated as Pyr14BF4), N-butyl-N-methylpyrrolidine chloride (abbreviated as Pyr14Cl), N-ethylpyridine-bis(trifluoromethanesulfonyl)imine (abbreviated as C2Py) The N-ethylpyridine-hexafluorophosphate (C2PyPF6), N-ethylpyridine tetrafluoroborate (C2PyBF4), N-ethylpyridine chloride (C2PyCl), N-butylpyridine-bis(trifluoromethanesulfonyl)imide (C4PyTFSI), N-butylpyridine-hexafluorophosphate (C4PyPF6), N-butylpyridine tetrafluoroborate (C4PyBF4), and N-butylpyridine chloride (C4PyCl) are at least one of the following:

[0013] More preferably, the ionic liquid comprises N,N,N-tris-(2-(2-methoxyethoxy)ethyl)-N-(2-methoxyethoxy)ammonium chloride (abbreviated as N... O7 Cl).

[0014] The N,N,N-tris-(2-(2-methoxyethoxy)ethyl)-N-(2-methoxyethoxy)ammonium-chloride salt Preferably, the graphite material includes at least one of graphene, expanded graphite, artificial graphite, natural graphite, mesophase carbon microspheres, flake graphite, petroleum coke, highly oriented pyrolytic graphite, and spherical graphite.

[0015] More preferably, the graphite material includes graphene.

[0016] This invention uses graphene as a specific positive electrode material and utilizes its layered structure to achieve the high-capacity, high-rate intercalation reaction of the above-mentioned bis(trifluoromethanesulfonyl)imide anion.

[0017] Preferably, the concentration of the magnesium salt in the electrolyte is 0.1-10 mol / L.

[0018] More preferably, the concentration of the magnesium salt in the electrolyte is 0.1-5 mol / L.

[0019] More preferably, the concentration of the magnesium salt in the electrolyte is 0.3-2 mol / L. For example, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, and 1.8 mol / L.

[0020] Preferably, the solvent of the electrolyte is an ionic liquid and does not contain other organic solvents.

[0021] More preferably, the electrolyte is composed of an ionic liquid and a magnesium salt.

[0022] Traditional aprotic solvents, such as carbonate solvents, form a passivation layer on the surface of the magnesium metal anode that insulates against magnesium ions. This prevents reversible deposition / dissolution of magnesium ions on the magnesium metal anode surface. The electrolyte of this invention uses only ionic liquids as the electrolyte solvent, which significantly reduces the formation of the passivation film on the magnesium metal anode surface. It also enables a high-voltage, fast-kinetic, and cycle-stable anion intercalation mechanism, a mechanism not previously reported in the literature.

[0023] Preferably, the magnesium-based dual-ion battery further includes a separator; the separator includes at least one of a glass fiber separator, a porous ceramic separator, a porous polymer separator, and a porous polymer separator with a ceramic coating.

[0024] More preferably, the porous polymer membrane includes a porous polypropylene membrane, a porous polyethylene membrane, or a porous composite polyethylene membrane. More preferably, the porous polymer tape ceramic-coated separator comprises a porous polyethylene tape ceramic-coated separator. Preferably, the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, the positive electrode active material including the above-mentioned graphite-based material.

[0025] More preferably, the positive current collector is a metallic conductive material, including but not limited to one or more metals, alloys and composite materials selected from titanium, aluminum, copper, tin, zinc, lead, antimony, cadmium, gold, bismuth or germanium.

[0026] More preferably, the positive current collector is one or more of copper foil, aluminum foil, nickel foil, stainless steel foil, stainless steel mesh, and carbon-coated aluminum foil.

[0027] More preferably, the positive electrode active material layer further includes a conductive agent to improve the conductivity of the positive electrode. This application does not impose specific limitations on the type of conductive agent, which can be selected according to actual needs. As an example, the conductive agent can be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers.

[0028] More preferably, the positive electrode active material layer further includes a binder to firmly bond the positive electrode active material and an optional conductive agent to the positive electrode current collector. This application does not impose specific limitations on the type of binder, which can be selected according to actual needs. As an example, the binder can be one or more of polyvinylidene fluoride, styrene-butadiene rubber, polyacrylic acid, polytetrafluoroethylene, sodium alginate, polyimide, polyethylene oxide, polyvinyl alcohol, polytetrafluoroethylene, carboxymethyl cellulose, and SBR rubber.

[0029] More preferably, the mass ratio of the positive electrode active material, the conductive agent and the binder is (50-90):(5-40):(5-15).

[0030] Preferably, the negative electrode comprises magnesium metal.

[0031] More preferably, the negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, wherein the negative electrode active material layer includes one or more of magnesium sheets, magnesium foil, and magnesium powder.

[0032] More preferably, the negative electrode current collector can be made of materials such as metal foil or porous metal plate, and is further selected from one or more metals, alloys and composite materials selected from titanium, aluminum, copper, tin, zinc, lead, antimony, cadmium, gold, bismuth or germanium.

[0033] A second aspect of the present invention provides a method for preparing the magnesium-based dual-ion battery described in the first aspect, comprising the following steps: The positive electrode, negative electrode, separator, and electrolyte are assembled into a magnesium-based dual-ion battery.

[0034] Preferably, the method includes the following steps: After uniformly mixing the positive electrode active material, conductive agent, binder and organic solvent, the mixture is coated onto the current collector and dried under vacuum to obtain the positive electrode sheet; after uniformly mixing the negative electrode material, binder and organic solvent, the mixture is coated onto the current collector and dried under vacuum to obtain the negative electrode sheet; the obtained positive electrode sheet, negative electrode sheet and electrolyte are assembled into a battery.

[0035] Preferably, the packaging form can be any of the following battery types: Swagelok battery, button cell battery, cylindrical battery, or pouch cell battery.

[0036] A third aspect of the present invention provides an electrical device comprising the magnesium-based dual-ion battery described in the first aspect.

[0037] Preferably, the electrical equipment includes electronic equipment, energy storage system, communication equipment, or communication base station.

[0038] The beneficial effects of this invention are: This invention provides a magnesium dual-ion battery. The magnesium dual-ion battery constructs a battery configuration with magnesium metal as the negative electrode and graphite-like materials as the positive electrode, and uses an anion intercalation mechanism to replace the cation intercalation behavior in traditional magnesium batteries. Specifically, it adopts a synergistic design of ionic liquid electrolyte and mixed magnesium salt to effectively control the magnesium deposition interface, achieving performance significantly better than traditional magnesium batteries. This invention utilizes a dual-ion battery mechanism, combining the high operating voltage of graphite cathode with the high capacity of magnesium metal anode, and leveraging the wide electrochemical window of ionic liquid electrolyte. This effectively solves the problems currently faced by magnesium-ion batteries, such as narrow voltage window, flammability and explosiveness, short cycle life, low cathode capacity, and low cathode voltage. The magnesium dual-ion battery of this invention has the following main effects: it enables long-life deposition of magnesium metal anode at low overpotential (0.2 V) (symmetric battery cycle life reaches 2000 hours); simultaneously, through the high-capacity, high-rate intercalation reaction of anions in graphite cathode, the full battery achieves a discharge specific capacity of 120 mAh / g at 1 C current density, maintains 104 mAh / g at a high rate of 5 C, exhibits excellent capacity retention after 1500 cycles, and has a discharge voltage as high as 3.73 V, realizing a magnesium-based energy storage device with high energy density, long cycle life, and high safety. Attached Figure Description

[0039] Figure 1 The cycling curve of the magnesium symmetric battery in Example 1; Figure 2 This is a structural diagram of a magnesium dual-ion secondary battery; where 1 is the negative electrode current collector, 2 is the negative electrode of the battery, 3 is the electrolyte, 4 is the separator, 5 is the positive electrode of the battery, and 6 is the positive electrode current collector; Figure 3 The charge-discharge curve of the magnesium dual-ion battery in Example 85; Figure 4 The rate performance of the magnesium dual-ion battery of Example 85 and the conventional Mo6S8 cathode magnesium-ion battery is compared. Figure 5 The long-cycle performance of the magnesium dual-ion battery in Example 85. Detailed Implementation

[0040] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials used in the following embodiments can be obtained from conventional commercial channels or prepared and isolated through simple synthesis; unless otherwise specified, the processes employed are conventional processes in the art.

[0041] The N,N,N-tri-(2-(2-methoxyethoxy)ethyl)-N-(2-methoxyethoxy)amino-bis(trifluoromethanesulfonyl)imine salt (N O7 For the preparation method of TFSI, please refer to the literature [https: / / doi.org / 10.1016 / j.jpowsour.2019.03.049].

[0042] The N,N,N-tri-(2-(2-methoxyethoxy)ethyl)-N-(2-methoxyethoxy)amino-hexafluorophosphate used (abbreviated as N) O7 The preparation method of PF6 is also the same as described in the above literature, except that the bis(trifluoromethane)sulfonylimide salt in the raw materials is replaced with hexafluorophosphate.

[0043] The N,N,N-tris-(2-(2-methoxyethoxy)ethyl)-N-(2-methoxyethoxy)amino-tetrafluoroborate used (abbreviated as N) O7 The preparation method of BF4 is also the same as described in the above literature, except that the bis(trifluoromethane)sulfonylimide salt in the raw materials is replaced with tetrafluoroborate.

[0044] The preparation method of NN,N-tris-(2-(2-methoxyethoxy)ethyl)-N-(2-methoxyethoxyamino-aluminate) salt (abbreviated as NoCI) is also the same as described in the above literature, except that the intermediate product N is used instead of the above-mentioned product. O7 Br is exchanged for N by passing it through a chloride anion exchange resin. O7 Cl.

[0045] Example 1 This embodiment provides a magnesium-symmetric battery, the specific preparation method of which is as follows: 1. Preparation of battery electrodes: Polish and grind 12mm diameter magnesium sheets to remove the surface oxide layer, and use them directly as the positive and negative electrodes of the battery.

[0046] 2. Preparation of battery separator: Cut glass fiber to the required size, vacuum dry it and use it as battery separator.

[0047] 3. Prepare the battery electrolyte: Weigh the electrolyte salts MgCl2 + Mg(TFSI)2 (molar ratio 1:1) and add them to the ionic liquid solvent N. O7 In Cl, a battery electrolyte with a salt concentration of 0.5 M was prepared.

[0048] 4. Battery assembly: In a glove box protected by inert gas, the prepared materials are stacked in the order of positive electrode, separator, and negative electrode. Electrolyte is added until the separator is completely wetted, and then the battery is placed in the outer packaging to complete the encapsulation.

[0049] Battery test: at 0.5 mA cm -2 Current density, 0.5 mAh cm⁻¹ -2 Under the given capacitance conditions, constant current charge-discharge cycles are performed.

[0050] Example 2-52 The symmetric battery fabrication processes in Examples 2-52 and Example 1 are identical except for the electrolyte formulation, specifically the type of ionic liquid. The electrochemical performance of the symmetric batteries prepared in Examples 2-52 was characterized. The electrolytes and electrochemical performance of Examples 2-52 are shown in Table 1 below: Table 1: Ionic liquid solvents and electrochemical performance parameters used in the symmetric batteries of Examples 1-52 of this invention

[0051] As shown in Table 1, in the embodiments of the present invention, the electrolyte solvent is preferably N. O7 Cl has a low magnesium deposition voltage and a long cycle life. Figure 1 The figure shows the cycle life of the magnesium symmetric battery in Example 1. The horizontal axis represents the cycle life of the magnesium symmetric battery, and the vertical axis represents the battery voltage during cycling. The battery was charged and discharged under constant current conditions of 0.5 mA cm⁻¹. -2 Charge / discharge for 1 hour. As shown in the figure, the polarization of magnesium deposition stripping is only 0.2V, and it has a cycle life of approximately 2000 hours.

[0052] Examples 53-59 The symmetric battery fabrication processes in Examples 53-59 are identical to those in Example 1, except for the electrolyte salt used. The electrochemical performance of the symmetric batteries prepared in Examples 53-59 was characterized and compared with that in Example 1. The electrolyte salts used in Examples 53-59 and the electrochemical performance of the symmetric batteries are shown in Table 2 below. Table 2: Electrolyte salts and electrochemical performance parameters used in the symmetric batteries of Examples 53-59 of this invention

[0053] As shown in Table 2, in the embodiments of the present invention, the electrolyte salt is preferably a mixed salt of MgCl2 and Mg(TFSI)2, which has a low magnesium precipitation active voltage and a long cycle life.

[0054] Examples 60-61 The symmetrical battery fabrication processes in Examples 60-61 are identical to those in Example 1, except for the use of the negative electrode active material. The electrochemical performance of the symmetrical batteries prepared in Examples 60-61 was characterized and compared with that in Example 1. The negative electrode active material and electrochemical performance of the symmetrical batteries used in Examples 60-61 are shown in Table 3 below. Table 3: Negative electrode active materials and electrochemical performance parameters used in the symmetric batteries of Examples 60-61 of the present invention

[0055] As shown in Table 3, in the embodiments of the present invention, the negative electrode active material is preferably magnesium sheet, which has a low active voltage and long cycle life.

[0056] Examples 62-71 The secondary battery preparation processes in Examples 62-71 and Example 1 are identical except for the electrolyte salt concentration. The electrochemical performance of the symmetric batteries prepared in Examples 62-71 was characterized and compared with that in Example 1. The electrolyte salt concentrations and electrochemical performance of the symmetric batteries in Examples 62-71 are shown in Table 4 below. Table 4: Electrolyte salt concentration and electrochemical performance parameters of the symmetric batteries used in Examples 62-71 of this invention

[0057] As shown in Table 4, in the embodiments of the present invention, the electrolyte salt concentration is preferably a mixed salt of 0.5 M MgCl2 and Mg(TFSI)2, which has a low magnesium precipitation active voltage and a long cycle life.

[0058] Examples 72-79 The symmetric battery fabrication processes in Examples 72-79 and Example 1 are identical except for the molar ratio of the mixed electrolyte salts used. The electrochemical performance of the symmetric batteries prepared in Examples 72-79 was characterized and compared with that in Example 1. The electrolyte salt concentrations and electrochemical performance of the symmetric batteries in Examples 72-79 are shown in Table 5 below. Table 5: Electrolyte salt concentration and electrochemical performance parameters of the symmetric batteries used in Examples 72-79 of this invention

[0059] As shown in Table 5, in the embodiments of the present invention, the preferred molar ratio of the mixed salt of MgCl2 and Mg(TFSI)2 is 1:1, which results in a low magnesium precipitation active voltage and a long cycle life.

[0060] Examples 80-84 The secondary battery preparation processes in Examples 80-84 and Example 1 are identical except for the type of separator used; all other materials and preparation steps are the same. The electrochemical performance of the symmetric batteries prepared in Examples 80-84 was characterized and compared with that in Example 1. The electrolyte salt concentrations and electrochemical performance of the symmetric batteries in Examples 80-84 are shown in the table below: Table 6: Electrolyte salt concentration and electrochemical performance parameters of the symmetric batteries used in Examples 80-84 of this invention

[0061] As shown in Table 6, in the embodiments of the present invention, the diaphragm is preferably a glass fiber diaphragm, which has a low magnesium deposition active voltage and a long cycle life.

[0062] Example 85 This embodiment provides a magnesium dual-ion secondary battery, the structural diagram of which is shown below. Figure 2 The structure consists of: negative electrode current collector 1, battery negative electrode 2, electrolyte 3, separator 4, battery positive electrode 5, and positive electrode current collector 6. Its preparation method is as follows: 1. Preparation of the battery positive electrode: Graphene, conductive carbon black, and polyvinylidene fluoride were mixed and ground in a ratio of 8:1:1, and then added to a solution of N-methylpyrrolidone. The mixture was ground thoroughly to obtain a uniform paste. The paste was then coated onto the surface of a titanium foil current collector using a scraper. The electrode sheet was vacuum dried for 12 hours and then cut to the required size to serve as the battery positive electrode.

[0063] 2. Preparation of battery negative electrode: Polish and grind a 12mm diameter magnesium sheet to remove the surface oxide layer, and use it as the battery negative electrode.

[0064] 3. Preparation of battery separator: Cut glass fiber to the required size, vacuum dry it and use it as battery separator.

[0065] Preparation of battery electrolyte: Add electrolyte salts MgCl2 and Mg(TFSI)2 to the ionic liquid solvent N in a 1:1 molar ratio. O7 In Cl, a battery electrolyte with a salt concentration of 0.5 M was prepared.

[0066] 4. Battery assembly: In a glove box protected by inert gas, the prepared materials are stacked in the order of positive electrode, separator, and negative electrode. Electrolyte is added until the separator is completely wetted, and then the battery is placed in the outer packaging to complete the encapsulation.

[0067] Battery testing: Constant current charge-discharge cycles were performed within a voltage range of 2.3-4.3 V.

[0068] Examples 86-93 The secondary battery preparation processes in Examples 86-93 and Example 85 are identical except for the positive electrode active material used. The electrochemical performance of the secondary batteries prepared in Examples 86-93 was characterized and compared with that in Example 85. The positive electrode material and electrochemical performance of the secondary batteries prepared in Examples 86-93 are shown in Table 7 below: Table 7: Positive electrode active materials and electrochemical performance parameters used in the secondary batteries of Examples 85-93 of the present invention

[0069] As shown in Table 7, in the embodiments of the present invention, the preferred cathode material for the battery is graphene, which has high specific capacity, good rate performance, and good cycle performance.

[0070] Figure 3 The charge-discharge curves of the magnesium dual-ion battery in Example 85 are shown. Figure 3 The horizontal axis represents the specific capacity based on graphene mass, and the vertical axis represents the voltage. The battery uses constant current charging and discharging, with a battery rate of 1C and a voltage range of 2.3-4.3 V. From Figure 3 As can be seen from this, the magnesium dual-ion battery full cell has a high charge / discharge platform (3.73 V) and a high capacity (118 mAh g). -1 ).

[0071] Figure 4 The rate performance of the magnesium dual-ion battery of Example 85 and the conventional Mo6S8 cathode magnesium-ion battery is shown. Figure 4 The horizontal axis represents the number of cycles, and the vertical axis represents the specific capacity. The battery is cycled 10 times under current conditions of 1C, 2C, 3C, 5C, 3C, 2C, and 1C respectively. Figure 4 As can be seen, due to the rapid anion intercalation reaction on the positive electrode side, the magnesium dual-ion battery exhibits excellent rate performance compared to the traditional magnesium-ion battery with magnesium-ion intercalation (Mo6S8 positive electrode). Even under a high current of 5C, it can still achieve 104 mAh g⁻¹. -1 It boasts a high specific capacity. Furthermore, the battery exhibits good reversibility; when the current decreases to 1C after 60-70 cycles, the capacity reversibly recovers to 118 mAh g. -1 .

[0072] Figure 5 The long-cycle performance of the magnesium dual-ion battery in Example 85. Figure 5 The horizontal axis represents the number of cycles, the left vertical axis represents the specific capacity, and the right vertical axis represents the coulombic efficiency, with the battery cycled at a 1C current density. Figure 5 As can be seen, the magnesium dual-ion battery full cell has excellent cycle stability. After dozens of activation cycles, the battery coulombic efficiency exceeds 99.5%, and after about 2000 cycles, the battery capacity decays to 80% of the initial capacity.

[0073] Examples 94-101 The secondary battery preparation processes in Examples 94-101 and Example 85 are identical except for the conductive agent used. The electrochemical performance of the secondary batteries prepared in Examples 94-101 was characterized and compared with that in Example 85. The conductive agent used and the electrochemical performance of Examples 94-101 are shown in Table 8 below. Table 8: Conductive agents and electrochemical performance parameters used in the secondary batteries of Examples 94-101 of the present invention

[0074] As shown in Table 8, in the embodiments of the present invention, the conductive material is preferably conductive carbon black, which has high specific capacity, good rate performance and good cycle performance.

[0075] Examples 102-109 The secondary battery fabrication processes in Examples 102-109 and Example 85 are identical except for the binder used. The electrochemical performance of the secondary batteries prepared in Examples 102-109 was characterized and compared with that in Example 85. The binder materials used in Examples 102-109 and their electrochemical performance are shown in Table 9 below. Table 9: Binder materials and electrochemical performance parameters used in the secondary batteries of Examples 102-109 of the present invention

[0076] As shown in Table 9, in the embodiments of the present invention, the binder material is preferably polyvinylidene fluoride, which has high specific capacity, good rate performance and good cycle performance.

[0077] Examples 110-117 The secondary battery preparation processes in Examples 110-117 and Example 85 are identical except for the mass of the conductive agent and binder used. The electrochemical performance of the secondary batteries prepared in Examples 110-117 was characterized and compared with that in Example 85. The mass ratio of the conductive agent to the binder and the electrochemical performance in Examples 110-117 are shown in the table below: Table 10: Mass ratio of conductive agent to binder used in the secondary batteries of Examples 110-117 of the present invention and electrochemical performance parameter table

[0078] As shown in Table 10, in the embodiments of the present invention, the binder material is preferably polyvinylidene fluoride, which has high specific capacity, good rate performance and good cycle performance.

[0079] In summary, the secondary battery prepared using specific raw materials and proportions in Example 85 achieved a discharge specific capacity of 120 mAh / g at a 1 C current density, maintained 104 mAh / g at a high rate of 5 C, exhibited excellent capacity retention after 1500 cycles, and had a discharge voltage as high as 3.73 V. This overcomes the problems of low positive electrode capacity, low voltage, poor rate performance, and mismatch between negative electrode and electrolyte in existing magnesium-ion batteries, and realizes a magnesium-based energy storage device with high energy density, long cycle life, and high safety.

[0080] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A magnesium-based dual-ion battery, characterized in that, The magnesium-based dual-ion battery comprises a positive electrode, a negative electrode and an electrolyte; The active material of the positive electrode comprises a graphite material; the negative electrode comprises magnesium metal; The electrolyte comprises a magnesium salt and an ionic liquid.

2. The magnesium-based dual-ion battery of claim 1, wherein, The magnesium salt comprises at least one of magnesium chloride, magnesium nitrate, magnesium fluoride, magnesium bromide, magnesium iodide, magnesium sulfate, magnesium bis(trifluoromethylsulfonyl)imide, magnesium tetrafluoroborate, magnesium hexafluorophosphate, magnesium perchlorate.

3. The magnesium-based dual-ion battery of claim 1, wherein, The ionic liquid comprises at least one of a pyrrolidine ionic liquid, a piperidine ionic liquid, a quaternary ammonium salt ionic liquid, a quaternary phosphonium salt ionic liquid, a pyridine ionic liquid.

4. The magnesium-based dual-ion battery of claim 3, wherein, The ionic liquid comprises at least one of N,N,N-tris-(2-(2-methoxyethoxy)ethyl)-N-(2-methoxyethoxy)ammonium-bis(trifluoromethylsulfonyl)imide salt, N,N,N-tris-(2-(2-methoxyethoxy)ethyl)-N-(2-methoxyethoxy)ammonium-hexafluorophosphate salt, N,N,N-tris-(2-(2-methoxyethoxy)ethyl)-N-(2-methoxyethoxy)ammonium-tetrafluoroborate salt, N,N,N-tris-(2-(2-methoxyethoxy)ethyl)-N-(2-methoxyethoxy)ammonium-chloride salt, N-ethyl-N-methylpiperidinium-bis(trifluoromethylsulfonyl)imide salt, N-ethyl-N-methylpiperidinium-hexafluorophosphate salt, N-ethyl-N-methylpiperidinium-tetrafluoroborate salt, N-ethyl-N-methylpiperidinium-chloride salt, N-propyl-N-methylpiperidinium-bis(trifluoromethylsulfonyl)imide salt, N-propyl-N-methylpiperidinium-hexafluorophosphate salt, N-propyl-N-methylpiperidinium-tetrafluoroborate salt, N-propyl-N-methylpiperidinium-chloride salt, N-butyl-N-methylpiperidinium-bis(trifluoromethylsulfonyl)imide salt, N-butyl-N-methylpiperidinium-hexafluorophosphate salt, N-butyl-N-methylpiperidinium-tetrafluoroborate salt, N-butyl-N-methylpiperidinium-chloride salt, tetramethylammonium-bis(trifluoromethylsulfonyl)imide salt, tetramethylammonium-hexafluorophosphate salt, tetramethylammonium-tetrafluoroborate salt, tetramethylammonium-chloride salt, tetraethylammonium-bis(trifluoromethylsulfonyl)imide salt, tetraethylammonium-hexafluorophosphate salt, tetraethylammonium-tetrafluoroborate salt, tetraethylammonium-chloride salt, tetrabutylammonium-bis(trifluoromethylsulfonyl)imide salt, tetrabutylammonium-hexafluorophosphate salt, tetrabutylammonium-tetrafluoroborate salt, tetrabutylammonium-chloride salt, tetrabutylphosphonium-bis(trifluoromethylsulfonyl)imide salt, tetrabutylphosphonium-hexafluorophosphate salt, tetrabutylphosphonium-tetrafluoroborate salt, tetrabutylphosphonium-chloride salt, N-ethyl-N-methylpyrrolidinium-bis(trifluoromethylsulfonyl)imide salt, N-ethyl-N-methylpyrrolidinium-hexafluorophosphate salt, N-ethyl-N-methylpyrrolidinium-tetrafluoroborate salt, N-ethyl-N-methylpyrrolidinium-chloride salt, N-propyl-N-methylpyrrolidinium-bis(trifluoromethylsulfonyl)imide salt, N-propyl-N-methylpyrrolidinium-hexafluorophosphate salt, N-propyl-N-methylpyrrolidinium-tetrafluoroborate salt, N-propyl-N-methylpyrrolidinium-chloride salt, N-butyl-N-methylpyrrolidinium-bis(trifluoromethylsulfonyl)imide salt, N-butyl-N-methylpyrrolidinium-hexafluorophosphate salt, N-butyl-N-methylpyrrolidinium-tetrafluoroborate salt, N-butyl-N-methylpyrrolidinium-chloride salt, N-ethylpyridinium-bis(trifluoromethylsulfonyl)imide salt, N-ethylpyridinium-hexafluorophosphate salt, N-ethylpyridinium-tetrafluoroborate salt, N-ethylpyridinium-chloride salt, N-butylpyridinium-bis(trifluoromethylsulfonyl)imide salt, N-butylpyridinium-hexafluorophosphate salt, N-butylpyridinium-tetrafluoroborate salt, N-butylpyridinium-chloride salt.

5. The magnesium-based dual-ion battery of claim 1, wherein, The graphite-based material includes at least one of graphene, expanded graphite, artificial graphite, natural graphite, mesocarbon microbeads, flake graphite, petroleum coke, highly oriented pyrolytic graphite, and spheroidized graphite.

6. The magnesium-based dual-ion battery of claim 1, wherein, The concentration of the magnesium salt in the electrolyte is 0.1-10 mol / L.

7. The magnesium-based dual-ion battery of claim 1, wherein, The solvent of the electrolyte is an ionic liquid.

8. The magnesium-based dual-ion battery of claim 1, wherein, The magnesium-based dual-ion battery further includes a separator; the separator includes at least one of a glass fiber separator, a porous ceramic separator, a porous polymer separator, and a porous polymer separator with a ceramic coating.

9. The method of producing a magnesium-based dual-ion battery according to any one of claims 1 to 8, characterized in that, The method includes the following steps: Assembling the positive electrode, the negative electrode, and the electrolyte into a magnesium-based dual-ion battery.

10. An electric device, characterized by The electrical equipment includes the magnesium-based dual-ion battery according to any one of claims 1-8.

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