Organic magnesium-potassium mixed ion electrolyte and magnesium-potassium mixed ion battery

Abstract

The invention provides an organic magnesium-potassium mixed ion electrolyte, which belongs to the technical field of rechargeable batteries, and comprises a magnesium salt electrolyte, a potassium salt electrolyte, an amido organic solvent and an ether organic solvent, in the electrolyte, the concentration of the magnesium salt electrolyte is 0.1-1.0 mol / L, and the concentration of the potassium salt electrolyte is 0.1-1.0 mol / L; the magnesium salt electrolyte comprises at least one of Mg (TFSI) 2, Mg (PF6) 2, Mg (OTf) 2 and Mg (BF4) 2; the potassium salt electrolyte comprises at least one of KFSI, KPF6, KTFSI and KOTf. The monovalent metal ion potassium is introduced into the electrolyte, so that magnesium ions and potassium ions can be synergistically intercalated, the magnesium ions are promoted to be embedded into / separated from layered oxides, the organic magnesium-potassium mixed ion electrolyte has good compatibility with magnesium metal, the magnesium metal or magnesium alloy can be used as a negative electrode material of a mixed ion battery, and the organic magnesium-potassium mixed ion electrolyte can be used as a negative electrode material of the mixed ion battery. The energy density and the long cycle life of the battery are improved. The invention also provides a magnesium-potassium mixed ion battery.

Description

Technical Field

[0001] The invention belongs to the technical field of rechargeable batteries, and in particular relates to an organic magnesium-potassium mixed ion electrolyte and a magnesium-potassium mixed ion battery. Background Art

[0002] Rechargeable batteries are an important energy storage device that can be used to store intermittent energy generated by renewable energy sources such as solar energy and wind energy. Among them, lithium-ion battery (LI B) technology is considered to be one of the best existing energy storage technologies in the field of rechargeable batteries, with high energy density and excellent long-term cycle performance. Due to the explosive growth in demand for lithium-ion batteries, lithium-ion batteries obviously have the disadvantages of insufficient abundance in the earth's crust and difficulty in mining and use. In addition, the safety issues caused by uncontrollable lithium dendrite growth have also seriously hindered the development of lithium-ion batteries. Therefore, researchers have turned their attention to magnesium-ion batteries, zinc-ion batteries, calcium-ion batteries and other multivalent metal battery systems with richer resources, more friendly environment and higher energy density. Among them, rechargeable magnesium-ion batteries (RMBs) have a higher volumetric capacity (the volumetric capacity of magnesium is 3833mAh·cm -3 , almost twice that of lithium, 2062 mAh cm -3 ), in most cases without dendrites, low redox potential, abundant resources and other advantages have made it one of the most promising batteries in the post-lithium era.

[0003] Although magnesium-ion batteries have many advantages, the lack of suitable magnesium-ion battery cathode materials limits the development of high-performance magnesium batteries. + and Na + In contrast, due to the divalent nature of magnesium ions, Mg 2+ The electrostatic interaction with the cathode material is stronger, which increases the reaction energy barrier and slows down the Mg 2+ The diffusion dynamics of the layered cathode material lead to unsatisfactory electrochemical performance. In addition, during the charge and discharge process of the layered cathode material, as the metal ions are inserted / deintercalated between the layers, the valence state of the transition metal also changes. Among them, the manganese-based compounds are due to the Mn 3+ Ions are prone to Jahn-Te l ler distortion and disproportionation reaction (2Mn 3+ →Mn 2+ +Mn 4+ ), resulting in the elongation of the Mn-O bond and the 2+ The dissolution causes serious volume changes in the overall structure, resulting in structural instability, which in turn affects the cycle stability of the battery.

[0004] In recent years, magnesium-ion hybrid batteries have received extensive attention, including magnesium-lithium hybrid batteries, magnesium-sodium hybrid batteries, etc., but there are fewer reports on magnesium-potassium hybrid batteries. On the one hand, there is a lack of suitable positive electrode materials that can achieve reversible insertion / extraction of magnesium and potassium ions, and on the other hand, there is a lack of organic magnesium-potassium mixed ion electrolytes that can match magnesium metal negative electrodes. In addition, traditional mixed ion electrolytes are often accompanied by solvent and electrolyte decomposition, corrosion, passivation and other problems during the cycle process, so it is difficult to give full play to the advantages of high energy density and long life of the mixed ion battery system.

[0005] For example, the invention patent "Sodium-magnesium hybrid battery of P2 phase layered oxide positive electrode material and its preparation method and application" prepared a P2 phase layered oxide positive electrode material, whose chemical formula is Na x Mn y M z O 2-δ The invention also provides a preparation method and application of a sodium-magnesium hybrid battery using a P2-phase layered oxide positive electrode material. 2+ Due to the strong electrostatic attraction between the surrounding atoms, the diffusion in the solid phase material is slow and the kinetic performance is poor. In addition, due to the influence of the Jan-Taylor effect, the cycle performance of the manganese-based layered oxide positive electrode material is poor. 2+ Poor diffusion kinetics and poor structural stability are the current problems. According to the nomenclature proposed by Delmas et al., the letters P and O represent the prismatic or octahedral coordination environment of the alkali metal site, respectively, and the numbers 2 and 3 represent the number of repeating TMO2 layers in a single unit cell. x Among TMO2 oxides, the P2 structure seems to be suitable as a positive electrode material for long cycle life tests. However, in actual applications, the narrow TMO2 interlayer spacing makes it difficult for ions to insert / eject between layers, which seriously limits the battery's rate performance and cycle stability.

[0006] The patent "Porous sheet-like nickel selenide nanomaterials and preparation methods, aqueous lithium / magnesium mixed ion electrolyte, lithium / magnesium mixed ion battery" prepared aqueous lithium-magnesium mixed electrolyte and lithium / magnesium mixed ion battery. In aqueous lithium-magnesium mixed ion batteries, the designed lithium-magnesium mixed ion aqueous electrolyte will passivate the metal magnesium negative electrode, so metal magnesium and its alloys cannot be used as battery negative electrodes, abandoning the advantage that metal magnesium and its alloys can be directly used as magnesium battery negative electrodes, and it is difficult to give full play to the characteristics of high volume energy density of magnesium metal negative electrodes. Summary of the invention

[0007] In order to obtain a novel magnesium-potassium mixed ion battery, the present invention provides an organic magnesium-potassium mixed ion electrolyte, which introduces monovalent metal ion potassium, can achieve synergistic intercalation of magnesium ions and potassium ions, promote the embedding / deintercalation of magnesium ions in layered oxides, and the organic magnesium-potassium mixed ion electrolyte has good compatibility with magnesium metal, and magnesium metal or magnesium alloy can be used as the negative electrode material of the mixed ion battery, thereby improving the battery energy density and long cycle life.

[0008] The invention also provides a magnesium-potassium mixed ion battery.

[0009] The present invention is achieved through the following technical solutions:

[0010] The present invention provides an organic magnesium-potassium mixed ion electrolyte, wherein the electrolyte comprises a magnesium salt electrolyte, a potassium salt electrolyte, an amine-based organic solvent and an ether-based organic solvent;

[0011] In the electrolyte, the concentration of the magnesium salt electrolyte is 0.1-1.0 mol / L, and the concentration of the potassium salt electrolyte is 0.1-1.0 mol / L;

[0012] The magnesium salt electrolyte includes at least one of Mg(TFSI)2, Mg(PF6)2, Mg(OTf)2 and Mg(BF4)2 (magnesium tetrafluoroborate);

[0013] The potassium salt electrolyte includes at least one of KFSI, KPF6, KTFSI and KOTf (potassium trifluoromethanesulfonate).

[0014] Further, the amino-based organic solvent includes at least one of 1-methoxy-2-propylamine, 2-methoxyethylamine, 3-methoxypropylamine, ethylenediamine and bis(2-methoxyethyl)amine;

[0015] The ether organic solvent includes at least one of tetrahydrofuran (THF), DME (ethylene glycol dimethyl ether), G2 (diethylene glycol dimethyl ether), G3 (triethylene glycol dimethyl ether) and G4 (tetraethylene glycol dimethyl ether).

[0016] Furthermore, the mass ratio of the amino organic solvent to the ether organic solvent is 5:1 to 1:5.

[0017] Based on the same inventive concept, the present invention provides a method for preparing an organic magnesium-potassium mixed ion electrolyte, the preparation method comprising:

[0018] Mixing an amino organic solvent and an ether organic solvent to obtain a mixed solvent;

[0019] A magnesium salt electrolyte and a potassium salt electrolyte are dissolved together in the mixed solvent to obtain an organic magnesium potassium mixed ion electrolyte.

[0020] Based on the same inventive concept, the present invention provides an application of an organic magnesium-potassium mixed ion electrolyte in the preparation of a magnesium-potassium mixed ion battery.

[0021] Based on the same inventive concept, the present invention provides a magnesium-potassium mixed ion battery, which contains the above-mentioned organic magnesium-potassium mixed ion electrolyte.

[0022] Based on the same inventive concept, the present invention also provides a magnesium-potassium mixed ion battery, which uses magnesium metal or magnesium alloy as the negative electrode, a Mn composite material as the positive electrode, a glass fiber membrane as the separator, and the above-mentioned organic magnesium-potassium mixed ion electrolyte as the electrolyte.

[0023] Furthermore, the raw materials for preparing the Mn composite material include K x MnO2 positive electrode material, conductive agent and binder, and K x The mass ratio of MnO2 positive electrode material, conductive agent and binder is 7:2:1;

[0024] The conductive agent includes at least one of graphene, Super P, Ketjen black and acetylene black;

[0025] The binder includes at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) and polyacrylic acid (PAA).

[0026] Furthermore, the positive electrode is prepared by the following method:

[0027] The potassium salt and the manganese salt are mixed and ball-milled in a certain molar ratio to obtain a powdery precursor;

[0028] The powdered precursor is calcined to obtain K x MnO2 cathode material;

[0029] The K x The MnO2 positive electrode material is mixed with a conductive agent and a binder, and then an organic solvent is added to prepare a slurry;

[0030] The slurry is coated on a current collector and dried to obtain a positive electrode sheet.

[0031] Preferably, the molar ratio of the potassium salt to the manganese salt is 1:2;

[0032] The potassium salt includes potassium carbonate, and the manganese salt includes manganese trioxide;

[0033] The calcination temperature of the powdered precursor is 900±50° C., and the calcination time is 12±2 h.

[0034] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0035] 1. The present invention discloses an organic magnesium-potassium mixed ion electrolyte. Compared with a single magnesium ion electrolyte, the electrolyte of the present invention introduces monovalent metal ion potassium, which can achieve synergistic intercalation of magnesium ions and potassium ions and promote the embedding / ejection of magnesium ions in layered oxides. In addition, unlike the passivation of magnesium metal by aqueous magnesium battery electrolyte, the organic magnesium-potassium mixed ion electrolyte of the present invention has good compatibility with magnesium metal, and magnesium foil or magnesium alloy can be used as the negative electrode material of the mixed ion battery, so that the mixed ion battery can have a higher energy density and a longer cycle life.

[0036] 2. The present invention discloses an organic magnesium-potassium mixed ion electrolyte. The electrolyte adopts a mixed solvent of an amine organic solvent and an ether organic solvent from the perspective of solvent regulation. The mixed solvent is a solvent with a molecular structure similar to that of traditional DME. The mixed solvent can change the desolvation energy of the solvated magnesium ions on the negative electrode side, promote the interfacial charge transfer kinetics, and thus improve the electrochemical performance of the ion battery, thereby solving the problem of mismatch between the electrolyte and the magnesium metal negative electrode.

[0037] 3. A magnesium-potassium mixed ion battery of the present invention, wherein the battery uses magnesium metal or magnesium alloy as the negative electrode, a Mn composite material as the positive electrode, and an organic magnesium-potassium mixed ion electrolyte as the electrolyte, wherein the P3 type K x MnO2 has a typical layered structure, and its large interlayer distance can weaken the Mg 2+ The electrostatic interaction with the surrounding atoms is Mg 2+ The diffusion migration provides sufficient space to reduce the reaction energy barrier, thereby improving ionic conductivity and accelerating Mg 2+ The diffusion dynamics of the magnesium-potassium mixed ion battery of the present invention can be improved, and the cycle stability of the material during the cycle process is improved. The magnesium-potassium mixed ion battery of the present invention can realize the synergistic energy storage of magnesium ions and potassium ions in a mixed system, and has a significant improvement in capacity and cycle performance compared to a single magnesium ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 is the SEM image of KMO prepared in Example 1;

[0040] Figure 2TEM image of KMO prepared in Example 1;

[0041] Figure 3 The 10th charge-discharge curve of the KMO positive electrode material in the mixed ion electrolyte of Example 1;

[0042] Figure 4 It is the long cycle curve of KMO positive electrode material in the mixed ion electrolyte of Example 2;

[0043] Figure 5 The charge and discharge curves of the KMO positive electrode material in the magnesium battery electrolyte in Comparative Example 1 for the first 50 cycles;

[0044] Figure 6 The charge and discharge curves of the KMO positive electrode material in the magnesium-potassium mixed ion electrolyte without amine solvent in Comparative Example 2 for the first 20 cycles. DETAILED DESCRIPTION

[0045] The present invention will be described in detail below in conjunction with specific implementations and examples, and the advantages and various effects of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific implementations and examples are used to illustrate the present invention, rather than to limit the present invention.

[0046] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. In the event of a conflict, the present specification takes precedence.

[0047] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0048] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0049] The technical principle of the present invention is as follows:

[0050] Layered transition metal oxides have unique structural advantages and meet the requirements of Mg 2+ Insertion requirements, high theoretical specific capacity, simple synthesis, have great development potential in RMBs, especially manganese-based layered oxides, which have been widely studied due to their low cost and environmentally friendly characteristics. Although magnesium-ion batteries have many advantages, the lack of suitable magnesium-ion battery positive electrode materials limits the development of high-performance magnesium batteries. This is because: compared with monovalent Li + and Na + In contrast, due to the divalent nature of magnesium ions, Mg 2+The electrostatic interaction with the cathode material is stronger, which increases the reaction energy barrier and slows down the Mg 2+ The diffusion dynamics of Mg(TFSI)2 in the electrolyte are poor, which leads to poor electrochemical performance. In addition, in traditional electrolyte systems, the decomposition of electrolyte solvents such as ethylene glycol dimethyl ether (DME) or electrolyte salts such as Mg(TFSI)2 and the solvation of Mg in the electrolyte are also important. 2+ Difficulty in removing solvents also leads to poor electrochemical performance. In addition, during the charge and discharge process of the positive electrode material, as the alkali metal ions are inserted / deinserted between the layers, the valence state of the transition metal also changes. 3+ Ions are prone to Jahn-Te l ler distortion and disproportionation reaction (2Mn 3+ →Mn 2+ +Mn 4+ ), resulting in the elongation of the Mn-O bond and the 2+ The dissolution of the layered oxides causes a serious volume change in the overall structure, leading to structural instability, which in turn affects the cycle stability of the battery. Therefore, the development of new and stable layered oxide cathode materials is of great significance to the development of magnesium-ion batteries.

[0051] Typically, Mg 2+ The reasons for the slow diffusion in the cathode are: (1) Mg 2+ The transport at the liquid-solid interface is slow, that is, the solvated Mg 2+ The desolvation process is difficult, resulting in Mg 2+ Cannot diffuse quickly into the interior of the material; (2) Mg 2+ Diffusion in the bulk material is slow, i.e. divalent Mg 2+ The strong mutual attraction between the atoms and the surrounding atoms. 2+ Slow diffusion in bulk materials has long been a problem. Commonly used strategies include pre-embedding organic / inorganic small molecules to expand the interlayer distance. However, the positive electrode materials prepared by this type of method are thermodynamically unstable, and the layered structure is not easy to maintain during the cycle, which may lead to poor cycle stability.

[0052] Generally speaking, modified electrolyte is a solution for Mg 2+ The study in recent years shows that the interface dynamic behavior is affected by Mg 2+ The inventors found that the introduction of methoxyethylamine additives into the traditional Mg(TFSI)2 salt / ether electrolyte made the magnesium metal anode highly reversible through the solvation sheath reorganization. This solvation sheath reorganization not only bypassed the unfavorable desolvation process, but also achieved Mg 2+ Rapid diffusion at the interface is beneficial for suppressing the decomposition of solvent / electrolyte salt.

[0053] Based on this, the present invention proposes an organic magnesium-potassium mixed ion electrolyte and a battery. Starting from the perspective of solvent regulation, the electrolyte adopts a mixed solvent of an amine-based organic solvent and an ether solvent, which changes the desolvation energy of the solvated magnesium ions on the negative electrode side, promotes the interfacial charge transfer kinetics, solves the problem of mismatch between the electrolyte and the magnesium metal negative electrode, and inhibits the decomposition of the solvent / electrolyte salt.

[0054] The magnesium-potassium mixed ion battery of the present invention adopts a positive electrode material containing K x MnO2, with alkali metal ions K having a larger ionic radius + Replaced Na + , while achieving thermodynamic stability and expanding the intrinsic interlayer spacing, thereby increasing the Mg 2+ Diffusion rate in bulk material. K of P3 type of the present invention x MnO2 has a typical layered structure, and its large interlayer distance can weaken the Mg 2+ The electrostatic interaction with the surrounding atoms is Mg 2+ The diffusion migration provides sufficient space to improve ionic conductivity and accelerate the Mg 2+ The diffusion dynamics of the material can be improved and the cyclic stability of the material can be enhanced during the cycle.

[0055] Specifically, the present invention provides an organic magnesium-potassium mixed ion electrolyte, wherein the electrolyte comprises a magnesium salt electrolyte, a potassium salt electrolyte, an amine-based organic solvent, and an ether-based organic solvent;

[0056] In the electrolyte, the concentration of the magnesium salt electrolyte is 0.1-1.0 mol / L, and the concentration of the potassium salt electrolyte is 0.1-1.0 mol / L;

[0057] The magnesium salt electrolyte includes at least one of Mg(TFSI)2, Mg(PF6)2, Mg(OTf)2 and Mg(BF4)2;

[0058] The potassium salt electrolyte includes at least one of KFSI, KPF6, KTFSI and KOTf.

[0059] In the present invention, the concentration of the magnesium salt electrolyte in the electrolyte is 0.1-1.0 mol / L. Within this concentration range, the electrolyte has a high ion diffusion rate and a suitable viscosity, ensuring rapid ion diffusion; if the electrolyte concentration is too low, it may lead to low ion conductivity; if the concentration is too high, on the one hand, it generates higher costs, and on the other hand, it also increases the viscosity of the electrolyte, which is not conducive to ion diffusion.

[0060] In the present invention, the concentration of potassium salt electrolyte in the electrolyte is 0.1-1.0 mol / L. Within this concentration range, the electrolyte has a high ion diffusion rate and a suitable viscosity, thereby ensuring rapid ion diffusion. If the electrolyte concentration is too low, it may lead to low ion conductivity. If the concentration is too high, on the one hand, it generates higher costs, and on the other hand, it also increases the viscosity of the electrolyte, which is not conducive to ion diffusion.

[0061] In the present invention, the magnesium salt electrolyte uses at least one of Mg(TFSI)2, Mg(PF6)2, Mg(OTf)2 and Mg(BF4)2, all of which are common magnesium salts in magnesium batteries and are easily soluble in solvents commonly used in magnesium batteries. The potassium salt electrolyte uses at least one of KFSI, KPF6, KTFSI and KOTf, all of which are common potassium salts in potassium batteries and are easily soluble in solvents commonly used in potassium batteries.

[0062] Further, the amino-based organic solvent includes at least one of 1-methoxy-2-propylamine, 2-methoxyethylamine, 3-methoxypropylamine, ethylenediamine and bis(2-methoxyethyl)amine;

[0063] The ether organic solvent includes at least one of tetrahydrofuran, DME, G2, G3 and G4.

[0064] Furthermore, the mass ratio of the amino organic solvent to the ether organic solvent is 5:1 to 1:5.

[0065] In the present invention, the mass ratio of the amine organic solvent to the ether organic solvent is 5:1 to 1:5, which has the advantage that the amount of the amine solvent added is moderate, which can improve the solvation structure of the magnesium ions, promote the diffusion of cations, and alleviate the decomposition of anions.

[0066] Based on the same inventive concept, the present invention provides a magnesium-potassium mixed ion battery, which uses magnesium metal or magnesium alloy as a negative electrode, a Mn composite material as a positive electrode, a glass fiber membrane as a separator, and the above-mentioned organic magnesium-potassium mixed ion electrolyte as an electrolyte.

[0067] Furthermore, the raw materials for preparing the Mn composite material include K x MnO2 positive electrode material, conductive agent and binder, and K x The mass ratio of MnO2 positive electrode material, conductive agent and binder is 7:2:1;

[0068] The conductive agent includes at least one of graphene, Super P, Ketjen black and acetylene black;

[0069] The binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene and polyacrylic acid.

[0070] Furthermore, the positive electrode is prepared by the following method:

[0071] The potassium salt and the manganese salt are mixed and ball-milled in a certain molar ratio to obtain a powdery precursor;

[0072] The powdered precursor is calcined to obtain K x MnO2 cathode material;

[0073] The K x The MnO2 positive electrode material is mixed with a conductive agent and a binder, and then an organic solvent is added to prepare a slurry;

[0074] The slurry is coated on a current collector and dried to obtain a positive electrode sheet.

[0075] Preferably, the molar ratio of the potassium salt to the manganese salt is 1:2;

[0076] The potassium salt includes potassium carbonate, and the manganese salt includes manganese trioxide;

[0077] The calcination temperature of the powdered precursor is 900±50° C., and the calcination time is 12±2 h.

[0078] In the present invention, potassium carbonate is used as potassium salt and manganese trioxide is used as manganese salt. The advantages are low cost, safety, reliability and abundant raw materials. On the one hand, the synthesis process is simple, and on the other hand, the battery cost is reduced.

[0079] The organic magnesium-potassium mixed ion electrolyte and the magnesium-potassium mixed ion battery of the present invention will be described in detail below in combination with the embodiments and experimental data.

[0080] Example 1

[0081] A method for preparing a positive electrode material for a magnesium-potassium mixed ion battery comprises the following steps:

[0082] (1) Potassium carbonate and manganese trioxide in a stoichiometric ratio (1:2) are mixed to form a precursor, and the precursor is placed in a ball mill and ground at high speed for four hours to obtain a powdered precursor;

[0083] (2) After the powder precursor is pressed into a sheet precursor, the temperature is raised from room temperature to 900° C. in a muffle furnace at a heating rate of 5° C. / min, and heat treated in an air atmosphere for 12 hours; after natural cooling, the obtained product is taken out and quickly ground in a mortar for 5 to 10 minutes to obtain a P3 phase layered oxide magnesium potassium mixed ion battery positive electrode material K 0.5 MnO2.

[0084] The SEM image of the prepared magnesium-potassium mixed ion battery positive electrode material is shown in Figure 1 As shown, the synthesized K 0.5MnO2 has a uniform lamellar structure and the particle size is 2-5μm. Figure 2 This is the TEM image of the prepared magnesium-potassium mixed ion battery positive electrode material. Obvious lattice fringes can be seen from the TEM image, and the layer spacing is relatively large, about 0.64nm.

[0085] A method for preparing an organic magnesium-potassium mixed ion electrolyte comprises the following steps:

[0086] In this embodiment, the magnesium salt electrolyte used is Mg(TFSI)2, the potassium salt electrolyte is KTFSI, the ether organic solvent is DME (ethylene glycol dimethyl ether), the amine organic solvent is 2-methoxyethylamine, and the concentration of magnesium salt and potassium salt in the mixed electrolyte is 0.5 mol / L respectively. The preparation method comprises the following steps:

[0087] (1) adding 4A molecular sieves to dry DME (ethylene glycol dimethyl ether) and 2-methoxyethylamine solvents (wherein the mass ratio of DME to 2-methoxyethylamine is 4.7:1);

[0088] (2) Weigh a certain amount of the above magnesium salt and potassium salt and transfer them to a clean bottle. Calculate the amount of each solvent required based on the mass of the weighed salt, then use a pipette to accurately measure the amount of each required solvent and add it to the bottle containing the mixed electrolyte salt to prepare the required mixed ion electrolyte. The prepared electrolyte is stirred at room temperature using a magnetic stirrer for more than 12 hours until all the electrolyte salts are dissolved to obtain a clear magnesium-potassium mixed ion electrolyte.

[0089] A preparation method of a magnesium-potassium mixed ion battery, the specific preparation method is:

[0090] The positive electrode material K prepared in the above embodiment 1 0.5 MnO2, magnesium-potassium mixed ion electrolyte, GF-A glass fiber separator and polished magnesium foil were assembled into CR2032 button batteries: 0.5 MnO2 powder was uniformly mixed with conductive agent acetylene black and binder polyvinylidene fluoride (PVDF) in a mass ratio of 70:20:10, and a certain amount of N-methylpyrrolidone (NMP) solution was added to prepare slurry in a room temperature dry environment, and then the slurry was uniformly coated on the current collector aluminum (Al) foil, cut into pole pieces with a diameter of 12 mm, and vacuum dried for 12 hours, and assembled with polished magnesium foil, GF-A glass fiber separator and 100 μL of the mixed ion electrolyte in Example 1 into a magnesium potassium hybrid battery. The entire battery assembly process was carried out in a glove box filled with argon protection. Figure 3 The hybrid ion battery assembled for this example is -1 The charge and discharge curve of the 10th cycle under current shows a higher capacity and high coulombic efficiency.

[0091] Example 2

[0092] A method for preparing a positive electrode material for a magnesium-potassium mixed ion battery comprises the following steps:

[0093] (1) Potassium carbonate and manganese trioxide in a stoichiometric ratio of 1:2 are mixed to form a precursor, and the precursor is placed in a ball mill and ground at high speed for four hours to obtain a powdered precursor;

[0094] (2) After the powder precursor is pressed into a sheet precursor, the temperature is raised from room temperature to 900° C. in a muffle furnace at a heating rate of 5° C. / min, and heat-treated in an air atmosphere for 12 hours; after natural cooling, the obtained product is taken out and quickly ground in a mortar for 5 to 10 minutes to obtain a P3 phase layered oxide magnesium potassium mixed ion battery positive electrode material K 0.5 MnO2.

[0095] A method for preparing an organic magnesium-potassium mixed ion electrolyte comprises the following steps:

[0096] In this embodiment, the magnesium salt electrolyte used is Mg(TFSI)2, the potassium salt electrolyte is KTFSI, the ether organic solvent is DME (ethylene glycol dimethyl ether), the amine organic solvent is 3-methoxypropylamine, and the concentration of magnesium salt and potassium salt in the mixed electrolyte is 0.5 mol / L respectively. The preparation method comprises the following steps:

[0097] (1) adding 4A molecular sieve to dry DME (ethylene glycol dimethyl ether) and 3-methoxypropylamine solvents (wherein the mass ratio of DME to 3-methoxypropylamine is 4.67:1);

[0098] (2) Weigh a certain amount of the above magnesium salt and potassium salt and transfer them to a clean bottle. Calculate the amount of each solvent required based on the mass of the weighed salt, then use a pipette to accurately measure the amount of each required solvent and add it to the bottle containing the mixed electrolyte salt to prepare the required mixed ion electrolyte. The prepared electrolyte is stirred at room temperature using a magnetic stirrer for more than 12 hours until all the electrolyte salts are dissolved to obtain a clear magnesium-potassium mixed ion electrolyte.

[0099] A preparation method of a magnesium-potassium mixed ion battery, the specific preparation method is:

[0100] The positive electrode material K prepared in the above embodiment 2 0.5 MnO2, magnesium-potassium mixed ion electrolyte, GF-A glass fiber separator and polished magnesium foil were assembled into CR2032 button batteries: 0.5MnO2 powder was uniformly mixed with conductive agent acetylene black and binder polyvinylidene fluoride (PVDF) in a mass ratio of 70:20:10, and a certain amount of N-methylpyrrolidone (NMP) solution was added to prepare slurry in a room temperature dry environment, and then the slurry was uniformly coated on the current collector aluminum (Al) foil, cut into pole pieces with a diameter of 12 mm, and vacuum dried for 12 hours, and assembled with polished magnesium foil, GF-A glass fiber separator and 100 μL of mixed ion electrolyte in Example 2 to form a magnesium potassium hybrid battery. The entire battery assembly process was carried out in a glove box filled with argon protection. Figure 4 The cycle curve of the hybrid ion battery assembled in this embodiment shows its excellent cycle stability and high coulombic efficiency.

[0101] Comparative Example 1

[0102] A method for preparing a positive electrode material for a magnesium battery comprises the following steps:

[0103] (1) mixing potassium carbonate and manganese trioxide in a stoichiometric ratio of 1:2 to form a precursor, and grinding the precursor in a ball mill at high speed for four hours to obtain a powdered precursor;

[0104] (2) After the powder precursor is pressed into a sheet precursor, the temperature is raised from room temperature to 900° C. in a muffle furnace at a heating rate of 5° C. / min, and heat-treated in an air atmosphere for 12 hours; after natural cooling, the obtained product is taken out and quickly ground in a mortar for 5 to 10 minutes to obtain a P3 phase layered oxide magnesium battery positive electrode material K 0.5 MnO2.

[0105] The prepared K 0.5 MnO2 powder is mixed with conductive agent acetylene black and binder polyvinylidene fluoride (PVDF) in a mass ratio of 70:20:10, and a certain amount of N-methylpyrrolidone (NMP) solution is added. The slurry is ground in a dry environment at room temperature, and then the slurry is evenly coated on the current collector molybdenum (Mo) foil. After drying, it is cut into pole pieces with a diameter of 12 mm. The cut pole pieces are dried at 60°C under vacuum conditions for 12 hours and then transferred to a glove box for use.

[0106] A method for preparing an organic magnesium battery electrolyte comprises the following steps:

[0107] The magnesium salt electrolyte selected in this comparative example is Mg(TFSI)2, the ether organic solvent is DME (ethylene glycol dimethyl ether), the amine organic solvent is 3-methoxypropylamine, and the concentration of magnesium salt in the mixed electrolyte is 0.5 mol / L. The preparation method comprises the following steps:

[0108] (1) adding 4A molecular sieve to dry DME (ethylene glycol dimethyl ether) and 3-methoxypropylamine solvents (wherein the mass ratio of DME to 3-methoxypropylamine is 4.67:1);

[0109] (2) Weigh a certain amount of the above magnesium salt and transfer it to a clean bottle. Calculate the amount of each solvent required based on the mass of the weighed salt, then use a pipette to accurately measure the amount of each required solvent and add it to the bottle containing the electrolyte salt to prepare the required electrolyte. The prepared electrolyte is stirred at room temperature using a magnetic stirrer for more than 12 hours until all the electrolyte salt is dissolved to obtain a clear magnesium battery electrolyte.

[0110] According to the same battery assembly method as in Examples 1 and 2, the materials in Comparative Example 1 were assembled into a magnesium battery. Figure 5 The charge and discharge curves of the magnesium battery assembled in this comparative example, compared with Example 2, show that the mixed ion battery using the magnesium-potassium mixed electrolyte has a more excellent performance.

[0111] Comparative Example 2

[0112] The preparation method of the positive electrode material is consistent with that of the aforementioned embodiment 1;

[0113] The electrolyte does not contain amine organic solvents, and the specific preparation method is as follows:

[0114] The magnesium salt electrolyte selected in this comparative example is Mg(TFSI)2, the potassium salt electrolyte is KTFSI, the ether organic solvent is DME (ethylene glycol dimethyl ether), and the concentration of magnesium salt and potassium salt in the mixed electrolyte is 0.5 mol / L respectively. The preparation method comprises the following steps:

[0115] (1) Add a certain amount of 4A molecular sieve to DME (ethylene glycol dimethyl ether) solvent for drying;

[0116] (2) Weigh a certain amount of the above magnesium salt and potassium salt and transfer them to a clean bottle. Calculate the amount of DME solvent required based on the mass of the weighed salts. Use a pipette to accurately measure the required amount of solvent and add it to the bottle containing the mixed electrolyte salt to prepare the required mixed ion electrolyte. The prepared electrolyte is stirred at room temperature using a magnetic stirrer for more than 12 hours until all the electrolyte salts are dissolved to obtain a clear magnesium-potassium mixed ion electrolyte.

[0117] The assembly method of the hybrid ion battery is the same as that of the above embodiment, and the test results are as follows: Figure 6, it can be seen that without the assistance of amine solvents, the hybrid ion battery using pure Mg(TFSI)2-KTFSI-DME electrolyte cannot cycle normally. Finally, it should be noted that the terms "include", "comprising" or any other variants thereof are intended to cover non-exclusive inclusions, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0118] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0119] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An organic magnesium potassium mixed ion electrolyte, characterized in that: The electrolyte comprises a magnesium salt electrolyte, a potassium salt electrolyte, an amine-based organic solvent and an ether-based organic solvent; In the electrolyte, the concentration of the magnesium salt electrolyte is 0.1-1.0 mol / L, and the concentration of the potassium salt electrolyte is 0.1-1.0 mol / L; The magnesium salt electrolyte includes at least one of Mg(TFSI)2, Mg(PF6)2, Mg(OTf)2 and Mg(BF4)2; The potassium salt electrolyte includes at least one of KFSI, KPF6, KTFSI and KOTf.

2. An organic magnesium potassium mixed ion electrolyte according to claim 1, characterized in that: The amino organic solvent includes at least one of 1-methoxy-2-propylamine, 2-methoxyethylamine, 3-methoxypropylamine, ethylenediamine and bis(2-methoxyethyl)amine; The ether organic solvent includes at least one of tetrahydrofuran, DME, G2, G3 and G4.

3. An organic magnesium potassium mixed ion electrolyte according to claim 1 or 2, characterized in that: The mass ratio of the amino organic solvent to the ether organic solvent is 5:1 to 1:

5.

4. A method for preparing an organic magnesium-potassium mixed ion electrolyte according to any one of claims 1 to 3, characterized in that: The preparation method comprises: Mixing an amino organic solvent and an ether organic solvent to obtain a mixed solvent; A magnesium salt electrolyte and a potassium salt electrolyte are dissolved together in the mixed solvent to obtain an organic magnesium potassium mixed ion electrolyte.

5. Use of an organic magnesium-potassium mixed ion electrolyte as described in any one of claims 1 to 3 in the preparation of a magnesium-potassium mixed ion battery.

6. A magnesium-potassium mixed ion battery, characterized in that: The magnesium-potassium mixed ion battery contains an organic magnesium-potassium mixed ion electrolyte according to any one of claims 1 to 3.

7. A magnesium-potassium mixed ion battery, characterized in that: The magnesium-potassium mixed ion battery uses magnesium metal or magnesium alloy as the negative electrode, a Mn composite material as the positive electrode, a glass fiber membrane as the separator, and an organic magnesium-potassium mixed ion electrolyte as described in any one of claims 1 to 3 as the electrolyte.

8. A magnesium-potassium mixed ion battery according to claim 7, characterized in that: The raw materials for preparing the Mn composite material include K x MnO2 positive electrode material, conductive agent and binder, and K x The mass ratio of MnO2 positive electrode material, conductive agent and binder is 7:2:1; The conductive agent includes at least one of graphene, Super P, Ketjen black and acetylene black; The binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene and polyacrylic acid.

9. A magnesium-potassium mixed ion battery according to claim 7, characterized in that: The positive electrode is prepared by the following method: The potassium salt and the manganese salt are mixed and ball-milled in a certain molar ratio to obtain a powdery precursor; The powdered precursor is calcined to obtain K x MnO2 cathode material; The K x The MnO2 positive electrode material is mixed with a conductive agent and a binder, and then an organic solvent is added to prepare a slurry; The slurry is coated on a current collector and dried to obtain a positive electrode sheet.

10. A magnesium-potassium mixed ion battery according to claim 9, characterized in that: The molar ratio of the potassium salt to the manganese salt is 1:2; The potassium salt includes potassium carbonate, and the manganese salt includes manganese trioxide; The calcination temperature of the powdered precursor is 900±50° C., and the calcination time is 12±2 h.

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