CN111834673B - Alkaline earth metal hexafluorophosphate electrolyte and preparation method of electrolyte - Google Patents

Abstract

The invention relates to the field of secondary batteries, and particularly provides a calcium hexafluorophosphate electrolyte, an electrolyte and a preparation method thereof, a magnesium hexafluorophosphate electrolyte, an electrolyte and a preparation method thereof, and a calcium ion battery and a magnesium ion battery containing the electrolyte or the electrolyte. The electrolyte or electrolyte can be used as an active material of a calcium ion battery or a magnesium ion battery. The preparation method adopts cheap and easily-obtained reaction raw materials; the preparation method is simple and has strong operability; the prepared electrolyte and electrolyte have high purity and good stability, and the problem that the electrolyte and the electrolyte required by a calcium ion battery and a magnesium ion battery are difficult to obtain is effectively solved; and the by-products of the preparation method can be recycled and have high added value.

Description

A kind of alkaline earth metal hexafluorophosphate electrolyte and preparation method of electrolyte

technical field

The invention relates to the field of secondary batteries, in particular, to an electrolyte of calcium hexafluorophosphate and magnesium hexafluorophosphate and a preparation method thereof, an electrolyte solution and a preparation method thereof, and a calcium ion battery and a magnesium ion battery comprising the electrolyte or electrolyte solution Battery.

Background technique

Energy storage technology is an important part of energy application. Compared with primary batteries, secondary batteries have the advantages of resource recycling, economy and environmental protection; high-performance lithium-ion batteries are widely used in mobile electronic equipment, electric vehicles and other fields. However, the global reserves of lithium are only 14 million tons and the geographical distribution is uneven, which makes it difficult to support future energy storage demand. Therefore, it is of great significance to develop new energy storage systems, such as sodium ion, potassium ion, magnesium ion, calcium ion and other energy storage systems.

Calcium and magnesium ions act as divalent ions, and each mole of ions can react to produce twice as much charge as lithium ions. In addition, the crustal abundance of calcium element ranks fifth, and the crustal abundance of magnesium element ranks eighth, and the natural reserves are much higher than lithium. To this end, calcium-ion batteries and magnesium-ion batteries are expected to become a new generation of high-performance, low-cost energy storage technologies.

In the secondary battery, the electrolyte, as one of the main components of the battery, greatly affects the performance of the battery. Generally, the electrolyte of a secondary battery is composed of organic solvents, electrolytes (solutes), additives, etc., among which the electrolyte is the most critical component. Classified according to the type of anion, commonly used electrolytes include hexafluorophosphate, tetrafluoroborate, perchlorate and the like. Compared with other electrolytes, hexafluorophosphate electrolytes have many outstanding advantages, such as: better stability; good compatibility with conventional organic solvents; higher solubility in conventional organic solvents; electrolytes composed of them Has good electrical conductivity and ion mobility; does not corrode current collectors; etc. Based on the above advantages, lithium hexafluorophosphate and its electrolyte have been widely used in lithium-ion batteries. Accordingly, its alkaline earth metal electrolytes, especially hexafluorophosphate electrolytes such as calcium hexafluorophosphate, magnesium hexafluorophosphate and their electrolytes, are crucial for the development of calcium-ion batteries and magnesium-ion batteries.

For calcium ion and magnesium ion energy storage systems, corresponding electrolytes and electrolytes have not been well prepared. Document Chem.Mater.2015,27,8442 reported a synthetic method of calcium hexafluorophosphate (Ca(PF ₆ ) ₂ ): using acetonitrile as a solvent, silver hexafluorophosphate (AgPF ₆ ) and calcium chloride (CaCl ₂ ) ) as reactants and predict the reaction to occur:

The filtrate was vacuum dried to finally obtain a solid product. However, this report only verifies that the solid product contains hexafluorophosphate ions, and does not verify the cation species, purity and whether it contains crystallization solvent molecules in the product. Since the silver chloride (AgCl) produced by the reaction is a solid-phase product, it will adhere to the surface of the reactant and hinder the continuous progress of the reaction, so it cannot be guaranteed that the reaction can proceed completely. In addition, the precious metal precursor AgPF ₆ will bring extremely high production costs.

Document J.Am.Chem.Soc.2016,138,8682 used acetonitrile as solvent, nitroso hexafluorophosphate (NOPF ₆ ) and metal magnesium as reactants to prepare magnesium hexafluorophosphate (Mg(PF ₆ ) ₂ ) in acetonitrile solution, and the solid product Mg(PF ₆ ) ₂ (CH ₃ CN) ₆ containing crystallization solvent molecules was obtained by post-treatment. However, this document only prepared magnesium hexafluorophosphate electrolyte in acetonitrile, and failed to provide electrolytes of other organic solvent systems such as: magnesium hexafluorophosphate electrolytes of esters, ethers, sulfones, etc., while the electrolyte of acetonitrile The chemical window is relatively narrow, thus limiting the application of this electrolyte. In addition, if Mg(PF ₆ ) ₂ (CH ₃ CN) ₆ solid is used as electrolyte and other conventional organic solvents are used as solvent, dissolving 1 mol of magnesium source will bring 6 mol of acetonitrile molecules, causing significant solvent contamination.

The literature Chem. Commun. 2017, 53, 4573 intends to learn from the above method, using NOPF ₆ as a precursor to react with metal calcium to prepare calcium hexafluorophosphate electrolyte. However, experiments have shown that this method causes the oxidative decomposition of hexafluorophosphate ions to generate impurity difluorophosphate ions (PO ₂ F ₂ ⁻ ). This is because when NOPF ₆ is used as a precursor, the strong oxidizing gas NO generated by the reaction can oxidize hexafluorophosphate ions.

Another preparation method of Ca(PF ₆ ) ₂ electrolyte and electrolyte is: using the solution of alkali metal hexafluorophosphate, such as potassium hexafluorophosphate (KPF ₆ ), as the precursor, and using ion exchange resin for alkali metal cation make a replacement. The disadvantage of this method is that the ion exchange resin is expensive and cannot be reused, and the method cannot guarantee the purity of the cations in the electrolyte, and the prepared electrolyte contains a large amount of impurity ions.

The most mainstream method of industrial production of alkali metal hexafluorophosphate electrolyte is to use anhydrous hydrofluoric acid (HF), phosphorus pentafluoride (PF ₅ ) gas and metal fluoride (lithium fluoride, sodium fluoride, potassium fluoride) as a reactant. At present, the industrial production method of alkali metal hexafluorophosphate has not been used to prepare alkaline earth metal hexafluorophosphate. The reason is that there are intrinsic differences between alkali metal elements and alkaline earth metal elements. The outermost electron orbital of an alkali metal atom has only one electron, and the attraction of the outermost electron of the nucleus is very small, and it is easy to lose the outermost electron and become a cation with a positive charge; while the outermost electron orbital of an alkaline earth metal atom is With two electrons, this paired electron reduces the energy of the electron orbital. Therefore, alkaline earth metal nuclei are more attractive to the outermost orbital electrons, and the outermost electrons need more energy to break free from the nuclei. This intrinsic difference results in great differences in physical and chemical properties such as atomic radius, first ionization energy and chemical reactivity between alkali metal substances and alkaline earth metal substances. For this reason, it is unpredictable whether the preparation method of alkali metal hexafluorophosphate can be applied to alkaline earth metal hexafluorophosphate.

There are no other reports on the preparation of hexafluorophosphate electrolytes or electrolytes of calcium and magnesium ion systems.

In view of this, the present invention is proposed.

SUMMARY OF THE INVENTION

The first object of the present invention is to provide a preparation method of calcium hexafluorophosphate and magnesium hexafluorophosphate electrolyte, which has low cost, simple process, high product purity and high material utilization rate.

The second object of the present invention is to provide a calcium hexafluorophosphate electrolyte or a magnesium hexafluorophosphate electrolyte prepared by the above-mentioned electrolyte preparation method, which has high purity, good chemical stability, high ion mobility, and no corrosion. collector.

The third object of the present invention is to provide a preparation method of calcium hexafluorophosphate electrolyte and magnesium hexafluorophosphate electrolyte, which method has the same advantages as the above-mentioned preparation method of electrolyte solution.

The fourth object of the present invention is to provide calcium hexafluorophosphate electrolyte and magnesium hexafluorophosphate electrolyte, and the electrolyte prepared by using the electrolyte has the same advantages as the above electrolyte.

The fifth object of the present invention is to provide a calcium ion battery or a magnesium ion battery, including the above-mentioned calcium hexafluorophosphate electrolyte or electrolyte, or the above-mentioned magnesium hexafluorophosphate electrolyte or electrolyte.

The sixth object of the present invention is to provide an energy storage system including the above-mentioned calcium ion battery or magnesium ion battery.

The seventh object of the present invention is to provide an electrical device including the above-mentioned calcium ion battery or magnesium ion battery.

In order to realize the above-mentioned purpose of the present invention, the following technical solutions are specially adopted:

In the first aspect, the present invention provides a preparation method of calcium hexafluorophosphate and magnesium hexafluorophosphate electrolyte, and the reaction formula is as follows:

Here, MH ₂ is MgH ₂ or CaH ₂ , and the solvent is a non-aqueous organic solvent. The preparation method includes the following steps: placing an organic solvent, ammonium hexafluorophosphate and an alkaline earth metal hydride in the same container under the protection of an inert gas, and after the reaction is completed, an alkaline earth metal hexafluorophosphate electrolyte is obtained.

As a further preferred technical solution, the alkaline earth metal hydride is calcium hydride or magnesium hydride;

Preferably, the substance amount (molar number) of alkaline earth metal hydride should not be less than half of the substance amount of ammonium hexafluorophosphate;

In a second aspect, the present invention provides a calcium hexafluorophosphate electrolyte and a magnesium hexafluorophosphate electrolyte prepared by the above-mentioned electrolyte preparation method.

In a third aspect, the present invention provides a preparation method of calcium hexafluorophosphate electrolyte and magnesium hexafluorophosphate electrolyte, comprising the following steps: removing the organic solvent from the calcium hexafluorophosphate electrolyte or the magnesium hexafluorophosphate electrolyte. , or reduce the solubility of calcium hexafluorophosphate or magnesium hexafluorophosphate in a solvent to obtain calcium hexafluorophosphate electrolyte or magnesium hexafluorophosphate electrolyte.

In a fourth aspect, the present invention provides a calcium hexafluorophosphate electrolyte and a magnesium hexafluorophosphate electrolyte prepared by the above electrolyte preparation method.

In a fifth aspect, the present invention provides a calcium ion battery and a magnesium ion battery, comprising the above-mentioned calcium hexafluorophosphate electrolyte or electrolyte, or the above-mentioned magnesium hexafluorophosphate electrolyte or electrolyte.

In a sixth aspect, the present invention provides an energy storage system, comprising the above-mentioned calcium ion battery or magnesium ion battery.

In a seventh aspect, the present invention provides an electrical device, including the above-mentioned calcium ion battery or magnesium ion battery.

Compared with the prior art, the beneficial effects of the present invention are:

The preparation method of calcium hexafluorophosphate electrolyte and electrolyte, magnesium hexafluorophosphate electrolyte and electrolyte provided by the invention uses industrialized cheap precursor NH ₄ PF ₆ and metal hydride as raw materials, and avoids the use of toxic and strong corrosive raw materials HF, PF ₅ ; the preparation method is simple and does not require complicated instruments and equipment; the preparation method has nothing to do with organic solvents, and the solvent can be freely selected; the prepared product has high _{purity ;} It is a stable reducing gas to avoid the oxidative decomposition of hexafluorophosphate ions; the by-product NH ₃ is the raw material for industrial production of nitrogen fertilizer, and the by-product H ₂ is a kind of clean energy.

The calcium hexafluorophosphate electrolyte and electrolyte and the magnesium hexafluorophosphate electrolyte and electrolyte provided by the invention have higher purity and better chemical stability; have good compatibility with conventional electrode materials; High rate; does not corrode current collectors.

The calcium hexafluorophosphate electrolyte and the magnesium hexafluorophosphate electrolyte provided by the invention have high solubility in conventional organic solvents; the electrolyte obtained after the electrolyte is dissolved has high concentration, good electrical conductivity and ion mobility; no Corrosive current collectors.

The calcium ion battery and the magnesium ion battery provided by the present invention comprise the above electrolyte or electrolyte, and the calcium ion battery and the magnesium ion battery have higher working voltage and capacity.

The energy storage system provided by the present invention includes the above-mentioned calcium ion battery and magnesium ion battery, so it has at least the same advantages as the above calcium ion battery and magnesium ion battery, and has higher discharge voltage and charge-discharge capacity.

The electrical equipment provided by the present invention includes the above-mentioned calcium ion battery and magnesium ion battery, so it has at least the same advantages as the above calcium ion battery and magnesium ion battery, and has the advantages of high discharge voltage and high charge and discharge capacity. It can work for a longer time, reduce the number of charging times, prolong the service life, and be more convenient to use.

Description of drawings

Fig. 1 is the NMR spectrum (a) of ¹⁹ F and the NMR spectrum (b) of ³¹ P of electrolyte solution obtained in Example 1;

Fig. 2 is the mass spectrum of the gas produced by the reaction of Example 1;

Fig. 3 is the EDX figure of the electrolyte obtained in Example 2;

FIG. 4 is a constant-current charge-discharge curve diagram of the dual-carbon calcium ion battery formed in Example 3. FIG.

5 is a schematic structural diagram of a calcium ion battery or a magnesium ion battery provided by the present invention;

Icons: 1 - negative electrode current collector; 2 - negative electrode active material layer; 3 - separator; 4 - electrolyte solution; 5 - positive electrode active material layer; 6 - positive electrode current collector.

Detailed ways

The embodiments of the present invention will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. If the specific conditions are not indicated in the examples, it is carried out according to the conventional conditions or the conditions suggested by the manufacturer.

It should be noted:

In the present invention, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form new technical solutions.

In the present invention, unless otherwise specified, all the technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

In the present invention, unless otherwise specified, the involved components or their preferred components can be combined with each other to form a new technical solution.

A "range" disclosed herein may be in the form of a lower limit and an upper limit, which may be one or more lower limits, and one or more upper limits, respectively.

In the present invention, unless otherwise specified, each reaction or operation step may be performed sequentially or not. Preferably, the reaction methods herein are performed sequentially.

Unless otherwise defined, professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods or materials similar or equivalent to those described can also be used in the present invention.

In a first aspect, in at least one embodiment, a method for preparing a calcium hexafluorophosphate electrolyte or a magnesium hexafluorophosphate electrolyte is provided, comprising the following steps: mixing an organic solvent, ammonium hexafluorophosphate, and an alkaline earth metal hydride in an inert Place in the same container under gas protection, and obtain alkaline earth metal hexafluorophosphate electrolyte after the reaction is complete.

The method uses industrialized inexpensive precursors NH ₄ PF ₆ and metal hydrides; avoids the use of toxic and strong corrosive raw materials HF and PF ₅ ; the preparation method is simple and does not require complicated equipment; the preparation method is independent of the solvent, and the solvent can be freely selected; The prepared product has high purity; the by-products are all gases, ensuring the complete reaction; the by-products NH ₃ and H ₂ are stable reducing gases to avoid the oxidative decomposition of hexafluorophosphate ions; the by-product NH ₃ is the raw material for industrial production of nitrogen fertilizers , _H2 is a kind of clean energy.

The organic solvent is not particularly limited, and can be an organic solvent such as esters, sulfones, ethers, nitriles or ionic liquids. Specifically, including propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), acetonitrile (ACN), methyl formate (MF), methyl acetate (MA), N,N-dimethylacetamide (DMA), fluoroethylene carbonate (FEC), methyl propionate (MP), ethyl propionate (EP), acetic acid Ethyl ester (EA), γ-butyrolactone (GBL), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2MeTHF), 1,3-dioxolane (DOL), 4-methyl-1,3 -Dioxolane (4MeDOL), Dimethoxymethane (DMM), 1,2-Dimethoxypropane (DMP), Triethylene glycol dimethyl ether (DG), Dimethyl sulfone (MSM), Diethylene glycol Methyl ether (DME), vinyl sulfite (ES), propylene sulfite (PS), dimethyl sulfite (DMS), diethyl sulfite (DES), crown ether (12-crown-4), 1-Ethyl-3-methylimidazole-hexafluorophosphate, 1-ethyl-3-methylimidazole-tetrafluoroborate, 1-ethyl-3-methylimidazole-bis-trifluoromethanesulfonate Imide salt, 1-propyl-3-methylimidazole-hexafluorophosphate, 1-propyl-3-methylimidazole-tetrafluoroborate, 1-propyl-3-methylimidazole-bis Trifluoromethanesulfonimide salt, 1-butyl-1-methylimidazole-hexafluorophosphate, 1-butyl-1-methylimidazole-tetrafluoroborate, 1-butyl-1- Methylimidazole-bis-trifluoromethanesulfonimide salt, N-butyl-N-methylpyrrolidine-bis-trifluoromethylsulfonimide salt, 1-butyl-1-methylpyrrolidine- Bis-trifluoromethanesulfonimide salt, N-methyl-N-propylpyrrolidine-bis-trifluoromethylsulfonimide salt, N-methyl, propylpiperidine-bis-trifluoromethylsulfonyl One or more of imide salts, N-methyl, butylpiperidine-bis-trifluoromethanesulfonimide salts.

Preferably, the alkaline earth metal hydride is calcium hydride or magnesium hydride;

Preferably, the substance amount (molar number) of alkaline earth metal hydride should not be less than half of the substance amount of ammonium hexafluorophosphate;

In a second aspect, at least one embodiment provides a calcium hexafluorophosphate electrolyte or a magnesium hexafluorophosphate electrolyte, which is obtained by the above-mentioned preparation method of the calcium hexafluorophosphate electrolyte or the magnesium hexafluorophosphate electrolyte. The electrolyte has good chemical stability, high ion mobility, and does not corrode the current collector.

In a third aspect, a method for preparing calcium hexafluorophosphate electrolyte or magnesium hexafluorophosphate electrolyte is provided in at least one embodiment. The calcium hexafluorophosphate or magnesium hexafluorophosphate electrolyte is removed from the organic solvent, or the solubility of calcium hexafluorophosphate and magnesium hexafluorophosphate in the solvent is reduced to obtain calcium hexafluorophosphate electrolyte or magnesium hexafluorophosphate electrolyte.

The method of removing the organic solvent is not particularly limited. Specifically, it can be evaporated by heating, evaporation under reduced pressure, volatilization at room temperature and the like.

The method for reducing the solubility of calcium hexafluorophosphate and magnesium hexafluorophosphate in a solvent is not particularly limited. Specifically, methods such as freezing, passing through a weak polar or non-polar solvent, etc. can be used.

In a fourth aspect, at least one embodiment provides a calcium hexafluorophosphate electrolyte or a magnesium hexafluorophosphate electrolyte obtained by the above-mentioned preparation method of a calcium hexafluorophosphate electrolyte or a magnesium hexafluorophosphate electrolyte.

In a fifth aspect, in at least one embodiment, a calcium ion battery or magnesium ion battery is provided, comprising a positive electrode, a separator, a negative electrode, and the above-mentioned calcium hexafluorophosphate electrolyte or electrolyte, or the above-mentioned magnesium hexafluorophosphate electrolyte or electrolyte.

The calcium ion battery or magnesium ion battery provided by the present invention has two working principles, one of which is: during the charging process, the calcium ion or magnesium ion is extracted from the positive electrode and enters the electrolyte, and the calcium ion or magnesium ion in the electrolyte It migrates to the negative electrode and is embedded in the negative electrode active material; during the discharge process, calcium ions or magnesium ions are extracted from the negative electrode material and enter the electrolyte, and the calcium ions or magnesium ions in the electrolyte migrate to the positive electrode and are embedded in the positive electrode active material. . The second is: during the charging process, the anions in the electrolyte migrate to the positive electrode and are embedded in the positive electrode active material, and the calcium ions or magnesium ions in the electrolyte migrate to the negative electrode and are embedded in the negative electrode active material; during the discharge process, the anions are removed from the positive electrode. And into the electrolyte, calcium ions or magnesium ions are extracted from the negative electrode and enter the electrolyte.

positive electrode

The positive electrode comprises a positive electrode active material layer and a positive electrode current collector, the positive electrode active material layer comprises a positive electrode active material, a positive electrode conductive agent and a positive electrode binder, the content of the positive electrode active material is 60-95 wt %, and the content of the positive electrode conductive agent is 2-30wt%, and the content of the positive electrode binder is 2-10wt%.

Preferably, the positive electrode active material includes at least one of carbon materials, metals, alloys, sulfides, nitrides, oxides or carbides.

Preferably, the positive electrode current collector or the negative electrode current collector is any one of aluminum, copper, iron, tin, zinc, nickel, titanium, manganese, lead, antimony, cadmium, gold, bismuth or germanium, preferably aluminum;

Or, the positive electrode current collector or the negative electrode current collector is an alloy comprising at least any one of aluminum, copper, iron, tin, zinc, nickel, titanium, manganese, lead, antimony, cadmium, gold, bismuth or germanium;

Or, the positive electrode current collector or the negative electrode current collector is a composite material including at least any one of aluminum, copper, iron, tin, zinc, nickel, titanium, manganese, lead, antimony, cadmium, gold, bismuth or germanium.

"Alloy" refers to a substance with metallic properties synthesized by a certain method from two or more metals and metals or non-metals.

"Metal composite material" refers to a metal matrix composite conductive material formed by the combination of metal and other non-metallic materials. Typical but non-limiting metal composites include graphene-metal composites, carbon fiber-metal composites, ceramic-metal composites, and the like.

negative electrode

The negative electrode comprises a negative electrode active material layer and a negative electrode current collector, the negative electrode active material layer comprises a negative electrode active material, a negative electrode conductive agent and a negative electrode binder, the content of the negative electrode active material is 60-90 wt %, and the content of the negative electrode conductive agent is 5-30wt%, and the content of the negative electrode binder is 5-10wt%.

Preferably, the negative electrode active material includes at least one of carbon materials, metals, alloys, sulfides, nitrides, oxides or carbides.

Further, the positive electrode conductive agent or the negative electrode conductive agent includes at least one of conductive carbon black, conductive carbon spheres, conductive graphite, carbon nanotubes, conductive carbon fibers, graphene or reduced graphene oxide.

Further, the positive electrode binder or the negative electrode binder includes polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, carboxymethyl cellulose, SBR rubber (Styrene Butadiene Rubber, styrene-butadiene rubber) or polyolefins. at least one.

Electrolyte

The electrolyte includes the above-mentioned calcium hexafluorophosphate electrolyte or electrolyte, or magnesium hexafluorophosphate electrolyte or electrolyte.

Further, the electrolyte also includes additives, and the content of the additives is preferably 0.1-20 wt %. Adding additives to the electrolyte can form a stable solid electrolyte membrane on the surface of the electrode and improve the service life of the battery.

The additives include at least one of esters, sulfones, ethers, nitriles or olefins.

Additives include fluoroethylene carbonate, vinylene carbonate, ethylene ethylene carbonate, 1,3-propane sultone, 1,4-butane sultone, vinyl sulfate, propylene sulfate, ethylene sulfate Ester, vinyl sulfite, propylene sulfite, dimethyl sulfite, diethyl sulfite, ethylene sulfite, methyl chloroformate, dimethyl sulfoxide, anisole, acetamide , diazepine, meta-diazepine, crown ether 12-crown-4, crown ether 18-crown-6, 4-fluoroanisole, fluorinated chain ether, difluoromethyl ethylene carbonate, Trifluoromethyl ethylene carbonate, chloroethylene carbonate, bromoethylene carbonate, trifluoroethylphosphonic acid, bromobutyrolactone, fluoroacetoxyethane, phosphate, phosphite, phosphazene , ethanolamine, carbodimethamine, cyclobutyl sulfone, 1,3-dioxolane, acetonitrile, long chain olefins, aluminum oxide, magnesium oxide, barium oxide, sodium carbonate, calcium carbonate, carbon dioxide, sulfur dioxide or At least one of lithium carbonate.

diaphragm

The separator includes a porous polymer film or an inorganic porous film, preferably at least one of a porous polypropylene film, a porous polyethylene film, a porous composite polymer film, glass fiber paper or a porous ceramic separator.

5 is a schematic structural diagram of a calcium ion battery or a magnesium ion battery with a structure provided by the present invention, including a negative electrode current collector 1, a negative electrode active material layer 2, a separator 3, an electrolyte 4, a positive electrode active material layer 5 and Positive current collector 6.

Exemplarily, the above-mentioned preparation method of a calcium ion battery or a magnesium ion battery includes: assembling a positive electrode, a separator, a negative electrode and an electrolyte. The above preparation method has simple process and low manufacturing cost, and the calcium ion battery or magnesium ion battery prepared by the method has the advantages of high discharge voltage and high charge and discharge capacity.

Further preferably, the method comprises the following steps:

(a) Preparation of negative electrode: the negative electrode active material, negative electrode conductive agent and negative electrode binder are made into negative electrode slurry, and then the negative electrode slurry is coated on the surface of the negative electrode current collector, and dried and cut to obtain a negative electrode of the desired size; or , the negative electrode active material is pressed on the surface of the negative electrode current collector, and the negative electrode of the required size is obtained after cutting;

(b) preparation of electrolyte: the electrolyte prepared by the above-mentioned calcium hexafluorophosphate electrolyte and magnesium hexafluorophosphate electrolyte preparation method, or the electrolyte prepared by the above-mentioned calcium hexafluorophosphate electrolyte and magnesium hexafluorophosphate electrolyte preparation method is dissolved in organic Solvent-based electrolyte.

(c) Preparation of diaphragm: the porous polymer film or inorganic porous film of the required size is used as the diaphragm for standby use;

(d) Preparation of the positive electrode: the positive electrode active material, the positive electrode conductive agent and the positive electrode binder are made into a positive electrode slurry, and then the positive electrode slurry is coated on the surface of the positive electrode current collector, and dried to obtain a positive electrode of the desired size;

(e) assembling the negative electrode obtained in step (a), the electrolyte obtained in step (b), the separator obtained in step (c) and the positive electrode obtained in step (d).

Preferably, assembling specifically includes: in an inert environment, closely stacking or winding the prepared negative electrode, separator and positive electrode in turn, dripping electrolyte to completely infiltrate the separator, and then encapsulating it into a casing to complete the calcium ion battery or magnesium ion battery Assembly of the ion battery.

The shape of the calcium ion battery or magnesium ion battery of the present invention is not limited to a button battery, and can also be designed into a flat shape, a cylindrical shape and the like according to the core components.

In a sixth aspect, an energy storage system is provided in at least one embodiment, comprising the above-mentioned calcium ion battery or magnesium ion battery. The energy storage system includes the above calcium ion battery or magnesium ion battery, and thus has at least the same advantages as the above calcium ion battery or magnesium ion battery, and has higher discharge voltage and charge and discharge capacity.

The above energy storage system refers to a power storage system that mainly uses calcium ion batteries or magnesium ion batteries as a power storage source, including but not limited to household energy storage systems or distributed energy storage systems. For example, in a home energy storage system, electric power is stored in a calcium ion battery or a magnesium ion battery serving as an electric power storage source, and the electric power stored in the calcium ion battery or the magnesium ion battery is consumed as needed to enable use such as home electronics Various installations of products.

In a seventh aspect, in at least one embodiment, an electrical device is provided, comprising the above-mentioned calcium ion battery or magnesium ion battery. The electrical equipment includes the above-mentioned calcium ion battery or magnesium ion battery, so it has at least the same advantages as the above calcium ion battery or magnesium ion battery, and has the advantages of high discharge voltage and high charge and discharge capacity. Under the same discharge current, it can Work longer, reduce charging times, extend service life, and be more convenient to use.

The above-mentioned electrical equipment includes, but is not limited to, electronic devices, electric tools, or electric vehicles. The electronic device is an electronic device that performs various functions (eg, playing music) using a calcium ion battery or a magnesium ion battery as an operation power source. A power tool is a power tool that uses a calcium-ion battery or a magnesium-ion battery as a driving power source for moving parts (eg, drills). Electric vehicles are electric vehicles (including electric bicycles, electric vehicles) that rely on calcium ion batteries or magnesium ion batteries as driving power sources, and may be automobiles equipped with other driving sources in addition to calcium ion batteries or magnesium ion batteries (including hybrid vehicle).

Below in conjunction with embodiment and comparative example, the present invention will be described in further detail.

Example 1

The present embodiment provides a calcium hexafluorophosphate electrolyte and a preparation method thereof, comprising the following steps:

In an argon glove box, 0.652 g (4 mmol) NH ₄ PF ₆ and 0.2 g (4.7 mmol) CaH ₂ were placed in 10 mL dimethyl carbonate DMC; after stirring for 48 hours, a clear solution was obtained by filtration; The clear solution is degassed to obtain a Ca(PF ₆ ) ₂ electrolyte.

The prepared electrolyte was taken for ¹⁹ F and ³¹ P nuclear magnetic resonance (NMR) characterization. As shown in FIG. 1 , ¹⁹ F shows a doublet, and ³¹ P shows a septet, which are characteristic spectral lines of PF ₆ ^-ions , indicating that the solution contains PF ₆ ^-ions . No other peak shapes of ¹⁹ F and ³¹ P were seen, indicating that PF ₆ ^- was not decomposed; no characteristic peaks of ¹⁴ N/ ¹⁵ N were seen, indicating that the reaction of ammonium hexafluorophosphate had been completed.

The reaction product was taken for mass spectrometry (MS) characterization. As shown in FIG. 2 , the gas product contains a large amount of H ₂ and NH ₃ , which proves that the reaction generates gas product H ₂ and NH ₃ . The rest of the mass spectral signals were derived from the volatile molecules of the solvent dimethyl carbonate DMC and the argon gas in the glove box.

Take the prepared electrolyte, drop it on an inert substrate, and conduct elemental analysis after drying. The results show that the surface of the substrate contains a large amount of Ca element, indicating that the electrolyte contains a large amount of Ca ²⁺ . In addition, P and F elements can be seen.

Example 2

The present embodiment provides a calcium hexafluorophosphate electrolyte and a preparation method thereof, comprising the following steps:

The electrolyte solution prepared in Example 1 was taken and dried in vacuum for 24 hours to obtain calcium hexafluorophosphate electrolyte without organic liquid.

The prepared calcium hexafluorophosphate electrolyte was taken and characterized by energy dispersive X-ray spectroscopy (EDX). As shown in Fig. 3, it was proved that Ca, P, and F elements were contained in the electrolyte.

Example 3

This embodiment provides a calcium ion battery, which is prepared according to the following steps:

(1) Preparation of the negative electrode of the battery: The mesocarbon microspheres MCMB, conductive carbon black, and polyvinylidene fluoride PVDF were adjusted to a uniform slurry with N-methylpyrrolidone NMP in a mass ratio of 8:1:1. The slurry was uniformly coated on the surface of aluminum foil (negative electrode current collector) and dried in vacuum. The battery pole pieces obtained by drying were cut into circular pieces with a diameter of 12 mm, which were used as battery negative electrodes after compaction.

(2) Preparation of the positive electrode of the battery: The expanded graphite, conductive carbon black, and polyvinylidene fluoride PVDF were adjusted to a uniform slurry with N-methylpyrrolidone NMP in a mass ratio of 8:1:1. The slurry was uniformly coated on the surface of aluminum foil (positive electrode current collector) and dried in vacuum. The battery pole pieces obtained by drying were cut into circular pieces with a diameter of 10 mm, which were used as battery positive electrodes after compaction.

(3) Preparation of separator: The glass fiber film was cut into discs with a diameter of 16 mm and used as a separator for later use.

(4) battery assembly: in a glove box protected by an inert gas, the above-mentioned prepared negative pole piece, separator, and positive pole piece are closely stacked successively, drip the electrolyte obtained in Example 1 to make the separator completely infiltrate, and then stack the above-mentioned Part of it is packaged into the button battery case to complete the double carbon calcium ion battery assembly.

The constant current charge-discharge curve of the battery is shown in Figure 4. The calcium-ion battery has a specific charge capacity of 65.6mAh/g and a specific discharge capacity of 54.1mAh/g.

Example 4

The present embodiment provides a calcium ion battery, which is different from Example 3 in that the electrolyte used is: the calcium hexafluorophosphate electrolyte obtained in Example 2 is dissolved in EC+DMC+EMC (volume ratio is 4: 3:2) to prepare a calcium hexafluorophosphate electrolyte with a concentration of 0.6 mol/L. The rest are the same as those in Embodiment 3, and are not repeated here.

Examples 5-65

Examples 5-65 provide methods for preparing calcium hexafluorophosphate electrolytes and electrolytes. The difference from Example 1-2 lies in the amount of calcium hydride used, the type of organic solvent, the reaction time, and the method for removing the organic solvent, as shown in Table 1.

The preparation method of the calcium hexafluorophosphate electrolyte of table 1 embodiment 5-65 and electrolyte

Examples 66-126

Embodiments 66-126 provide the preparation methods of magnesium hexafluorophosphate electrolyte and electrolyte. The difference from Examples 5-55 lies in the amount of magnesium hydride used, the type of organic solvent, the reaction time, and the method for removing the organic solvent, as shown in Table 2.

The preparation method of the magnesium hexafluorophosphate electrolyte of table 2 embodiment 66-126 and electrolyte

Examples 127-156

Examples 127-156 provide methods of making calcium-ion batteries and magnesium-ion batteries. The difference from Examples 3-4 is that the electrolytes used in Examples 127-131 are respectively from the calcium hexafluorophosphate electrolytes obtained in Examples 5-9, and the electrolytes used in Examples 132-136 are respectively Examples 5-9 The 0.8mol/L calcium hexafluorophosphate electrolyte prepared by the gained calcium hexafluorophosphate electrolyte, the electrolyte used in Examples 137-141 are respectively the 0.5mol/L prepared by the gained calcium hexafluorophosphate electrolyte in Examples 5-9. Calcium hexafluorophosphate electrolyte; the electrolytes used in Examples 142-146 are respectively from the magnesium hexafluorophosphate electrolytes obtained in Examples 66-70, and the electrolytes used in Examples 147-151 are respectively the magnesium hexafluorophosphates obtained in Examples 66-70 The 0.7mol/L magnesium hexafluorophosphate electrolyte prepared by the electrolyte, the electrolytes used in Examples 152-156 are respectively the 0.4mol/L magnesium hexafluorophosphate electrolyte prepared by the magnesium hexafluorophosphate electrolyte obtained in Examples 66-70. liquid.

Examples 157-170

Examples 157-170 provide preparation methods for calcium ion batteries and magnesium ion batteries, and the differences from Examples 3-4 lie in the electrolytes and positive active materials used, as shown in Table 3.

The preparation method of the calcium ion battery and the magnesium ion battery of table 3 embodiment 157-170

Examples 171-184

Examples 171-184 provide preparation methods for calcium-ion batteries and magnesium-ion batteries, and differ from Examples 3-4 in the electrolyte used. The electrolyte used is obtained by blending the stock solution and the blending solution, as shown in Table 4.

The preparation method of the calcium ion battery and the magnesium ion battery of table 4 embodiment 171-184

Comparative Examples 1-4

The difference between Comparative Example 1-4 and Example 1-4 is that the amount of ammonium hexafluorophosphate used is 1.63 g (10 mmol), the dimethyl carbonate DMC used is 25 ml, and the rest are the same as in Example 1-4, No longer.

Comparative Examples 5-8

The difference between Comparative Example 5-8 and Example 1-4 is that the amount of ammonium hexafluorophosphate used is 1.63 g (10 mmol), the amount of magnesium hydride used is 0.05 g (2 mmol), and the amount of dimethyl carbonate used is 0.05 g (2 mmol). DMC is 25 ml, and the rest are the same as those in Examples 1-4, and will not be repeated here.

Elemental analysis of the electrolytes and electrolytes prepared in Comparative Examples 1-2 and 5-6 shows that the cations in the samples include not only calcium/magnesium ions, but also a large amount of ammonium ions, indicating that the corresponding preparation methods are not perfect, and the preparation The resulting electrolyte and electrolyte are of low purity.

Performance Testing

The calcium ion batteries and magnesium ions of Examples 127-184 and Comparative Examples 3-4 and 7-8 were subjected to constant current charge-discharge tests; the test results are shown in Table 5.

Table 5 Performance test results of calcium ion batteries or magnesium ion batteries of Examples 127-156 and Comparative Examples 3-4 and 7-8

As can be seen from Table 5, the preferred embodiments of the present invention (such as Examples 132-136, 145, and 149) have higher initial discharge specific capacity and higher specific discharge capacity than Comparative Examples 3-4 and 7-8. Stable discharge specific capacity. Therefore, the preferred embodiments of the present invention can provide more effective methods for preparing calcium hexafluorophosphate electrolyte and electrolyte, magnesium hexafluorophosphate electrolyte and electrolyte, and calcium ion batteries and magnesium ion batteries with better performance.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features thereof can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention. scope.

Claims (8)

1. a preparation method of alkaline earth metal hexafluorophosphate electrolyte, is characterized in that, comprises the following steps: The organic solvent, ammonium hexafluorophosphate and alkaline earth metal hydride are placed in the same container under the protection of inert gas, and the alkaline earth metal hexafluorophosphate electrolyte is obtained after the reaction is complete; wherein, the alkaline earth metal is magnesium or calcium. 2. preparation method according to claim 1 is characterized in that, alkaline earth metal hydride should be excessive, to ensure the purity of product. 3. The preparation method according to claim 1, wherein the organic solvent is any one of esters, sulfones, ethers, nitriles and ionic liquids. 4. preparation method according to claim 1, is characterized in that, The organic solvent is propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, acetonitrile, methyl formate, methyl acetate, N,N-dimethylacetamide, fluoroethylene carbonate Esters, methyl propionate, ethyl propionate, ethyl acetate, gamma-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-diol Oxycyclopentane, dimethoxymethane, 1,2-dimethoxypropane, triethylene glycol dimethyl ether, dimethyl sulfone, dimethyl ether, vinyl sulfite, propylene sulfite, dimethyl sulfite ester, diethyl sulfite, 12-crown-4, 1-ethyl-3-methylimidazole-hexafluorophosphate, 1-ethyl-3-methylimidazole-tetrafluoroborate, 1- Ethyl-3-methylimidazole-bistrifluoromethylsulfonimide salt, 1-propyl-3-methylimidazole-hexafluorophosphate, 1-propyl-3-methylimidazole-tetrafluoroboron acid salt, 1-propyl-3-methylimidazole-bis-trifluoromethylsulfonimide salt, 1-butyl-1-methylimidazole-hexafluorophosphate, 1-butyl-1-methyl Imidazole-tetrafluoroborate, 1-butyl-1-methylimidazole-bis-trifluoromethylsulfonimide salt, N-butyl-N-methylpyrrolidine-bis-trifluoromethylsulfonylidene Amine salt, N-methyl-N-propylpyrrolidine-bis-trifluoromethylsulfonimide salt, N-methyl-N-propylpiperidine-bis-trifluoromethylsulfonimide salt, N - One or more of methyl-N-butylpiperidine-bis-trifluoromethanesulfonimide salts. 5. an alkaline earth metal hexafluorophosphate electrolyte, characterized in that, The alkaline earth metal hexafluorophosphate electrolyte prepared by the preparation method according to any one of claims 1-4. 6. a preparation method of alkaline earth metal hexafluorophosphate electrolyte, is characterized in that, According to the alkaline earth metal hexafluorophosphate electrolyte prepared by the preparation method according to any one of claims 1-4, the organic solvent is removed, or the solubility of calcium hexafluorophosphate or magnesium hexafluorophosphate electrolyte in the solvent is reduced to obtain six Calcium fluorophosphate electrolyte or magnesium hexafluorophosphate electrolyte. 7. A calcium ion battery, characterized in that it comprises the calcium hexafluorophosphate electrolyte prepared by the preparation method according to any one of claims 1-4. 8. A magnesium ion battery, characterized in that it comprises the magnesium hexafluorophosphate electrolyte prepared by the preparation method according to any one of claims 1-4.

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