CN116553621B - Sodium iron sulfate and preparation method and application thereof - Google Patents

Sodium iron sulfate and preparation method and application thereof Download PDF

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CN116553621B
CN116553621B CN202310770903.7A CN202310770903A CN116553621B CN 116553621 B CN116553621 B CN 116553621B CN 202310770903 A CN202310770903 A CN 202310770903A CN 116553621 B CN116553621 B CN 116553621B
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sodium
sulfate
iron sulfate
preparation
temperature
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CN116553621A (en
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唐永炳
郑晓
姚文娇
韩晓琪
陈冲
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Shenzhen Institute of Advanced Technology of CAS
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Shenzhen Institute of Advanced Technology of CAS
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C01G49/009—Compounds containing, besides iron, two or more other elements, with the exception of oxygen or hydrogen
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/51—Particles with a specific particle size distribution
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/11—Powder tap density
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/10—Batteries in stationary systems, e.g. emergency power source in plant
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses sodium iron sulfate and a preparation method and application thereof, and belongs to the technical field of secondary battery materials. The preparation method of the sodium ferric sulfate provided by the invention comprises the steps of carrying out microwave solvothermal reaction on a mixed solution of a sodium source, an iron source, a sulfur source and an antioxidant; microwave solvothermal reaction is sequentially carried out on T 1 、T 1 ’ 、T 2 、T 2 ’ And T 3 The temperature is kept; wherein the temperature T 1 、T 2 、T 3 Each independently selected from 200-350 ℃; temperature T 1 ’ 、T 2 ’ Independently selected from 100-180 ℃. The preparation method provided by the invention can obviously improve the tap density of the sodium iron sulfate. The invention also provides the sodium iron sulfate prepared by the preparation method and the application of the sodium iron sulfate.

Description

Sodium iron sulfate and preparation method and application thereof
Technical Field
The invention relates to the technical field of secondary battery materials, in particular to sodium iron sulfate and a preparation method and application thereof.
Background
Since the 90 s of the last century, lithium ion batteries have been widely used in portable electronic devices and large energy storage systems because of their high specific capacity and high energy density. However, with the development of lithium resources in large quantities, the shortage and uneven distribution of global metal lithium resources, the raw material cost of lithium ion batteries is in a continuous trend. Sodium has similar physical and chemical properties with lithium, and the sodium resource reserves in the crust are considerable (the crust abundance of lithium is 0.006 percent and the crust abundance of sodium is 2.64 percent), so that the sodium ion battery has more advantages in cost, and the sodium ion battery becomes the battery system with the most commercial application potential after being used as the lithium ion battery. However, since the ionic radius of sodium ions is larger than that of lithium ions, the intercalation and deintercalation of sodium ions into electrode materials is more difficult than that of lithium ions in dynamics, and the relatively positive oxidation-reduction potential and the larger atomic mass of sodium ions lead to lower working voltage, lower specific capacity and poorer rate capability of the positive electrode materials of sodium ion batteries.
The prior sodium ion battery anode material mainly comprises layered oxide, polyanion compound, prussian blue compound, organic matters and the like. The layered oxide has higher energy density, but has poorer structural stability, the cycle life is difficult to break through ten thousands of times, and the cost is relatively higher; prussian blue system contains virulent cyanide ions, and the reversibility and stability of the electrochemical process of the Prussian blue system are seriously affected by crystal water, so that the Prussian blue system is not beneficial to industrial application; the organic positive electrode material is easy to dissolve in organic electrolyte due to low conductivity and density, and the energy density and the cycling stability of the organic positive electrode material are seriously influenced. While polyanionic materials have intrinsic advantages in terms of cost and cycling stability, they are becoming increasingly popular with researchers. Among the currently studied polyanion compounds, vanadium-based phosphate positive electrode materials are relevant due to high working voltage, but vanadium is toxic and expensive, which restricts the practical application of the materials; the iron-based sulfate positive electrode material has extremely low manufacturing cost and higher working potential, so the iron-based sulfate positive electrode material is considered as one of the most ideal positive electrode materials of sodium ion batteries.
The structure of the polyanionic sulfate compound may be represented by formula A x M y (SO 4 ) m Y n Wherein x is equal to or greater than 0, y is equal to or greater than 1, m is equal to or greater than 1, n is equal to or greater than 0, A represents an alkali metal ion such as Li, na, K, etc.; m represents one or more transition metal ions such as Fe, V, mn, co, cr, etc.; y represents an anion, e.g. F - ，Cl - ，PO 4 3- And OH (OH) - Etc. For monoanionic sulfate compounds, n=0, represented by MO 6 Octahedra and SO 4 Tetrahedra are connected in a mode of being co-point, co-edge or coplanarity to form a three-dimensional structure frame, and alkali metal ions are distributed in the frameThe gap of the frame can be wholly or partly moved in the frame. For the structure of the dianionic compounds, n>0,MX 6 (X is halogen or O) and Y anions, SO 4 Tetrahedral connections together form a three-dimensional framework. The monoanionic sulfate compound has simple components, easier control of the preparation process, less thermodynamic and kinetic influence factors of the electrochemical process, na + The deintercalation process is easier to study and regulate. In addition, sulfate radical has strong induction effect, is easy to obtain high potential material, and is a positive electrode material with great development potential.
Sodium iron sulfate Na 2 Fe 2 (SO 4 ) 3 Belongs to monoanionic sulfate positive electrode. Preparation of an aluaudiote-structured Na by ball milling 2 Fe 2 (SO 4 ) 3 Material in which FeO having two iron sites 6 Octahedral co-edge forms Fe 2 O 10 Dimers, which in turn are linked to SO 4 Tetrahedral bonding forms a three-dimensional open framework with 3 Na sodium sites. Subsequent studies have found that the material may exist in a non-stoichiometric ratio, forming Na by means of sodium and iron occupation and sodium vacancies 2.5 Fe 1.75 (SO 4 ) 3 、Na 2-x Fe 2 (SO 4 ) 3 And the like. At present, methods for preparing the sodium iron sulfate anode include a solid-phase method, a traditional hydrothermal method and the like. The solid phase method needs high temperature sintering and inert gas protection, has long calcination time, large energy consumption, difficult control of particle size and low tap density of the product. Although the active substances prepared by the traditional hydrothermal method are uniformly dispersed and have uniform particle size, the active substances are slow in heating speed, nonuniform in heating and long in reaction time, and the active substances are required to be baked at a high temperature under the protection of inert gas in the follow-up process, so that the energy consumption is high.
In conclusion, in the related sodium ion positive electrode material, the ferric sodium sulfate has a relatively wide application prospect, but the problems of difficult control of the particle size of the product, low tap density, complex process of the preparation method, high energy consumption, long time consumption and the like exist.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the invention provides the preparation method of the sodium iron sulfate, which can prepare the sodium iron sulfate with grain size grading, so that the tap density of the sodium iron sulfate is improved, and the high-rate capacity and the high-rate cycle performance of the sodium iron sulfate serving as the positive electrode material of the sodium ion battery are further improved.
The invention also provides the sodium iron sulfate prepared by the preparation method.
The invention also provides application of the preparation method in preparation of the sodium ion battery anode material.
The invention also provides a sodium ion battery positive plate.
The invention also provides a sodium ion battery.
The invention also provides application of the sodium ion battery.
According to an embodiment of the first aspect of the present invention, there is provided a method for preparing sodium iron sulfate, the method comprising subjecting a mixed solution of a sodium source, an iron source, a sulfur source and an antioxidant to a microwave solvothermal reaction;
the microwave solvothermal reaction is sequentially carried out on T 1 、T 1 ’ 、T 2 、T 2 ’ And T 3 The temperature is kept; wherein,
temperature T 1 、T 2 、T 3 Each independently selected from 200-350 ℃;
temperature T 1 ’ 、T 2 ’ Independently selected from 100-180 ℃.
The preparation method provided by the embodiment of the invention has at least the following beneficial effects:
(1) The basic principle of the microwave solvothermal method is that under the action of an electromagnetic field, polar molecules in a heated system are changed from the original random distribution state to be oriented according to the polar arrangement of the electromagnetic field. Under high frequency electromagnetic action, these orientations change in response to changes in the alternating electromagnetic field, which causes movement of the molecules and mutual friction to generate heat. At this time, the field energy of the alternating electromagnetic field is converted into kinetic energy in the heated material, so that the temperature of the heated material is continuously increased. The method has the advantages of high heating speed, uniform heating of the reaction system, sensitive reaction, lower reaction temperature and shorter reaction time, so that the efficient and controllable preparation of the functional material is easier to realize. The method shortens the reaction time by adopting a microwave solvothermal method, and the preparation of the sodium iron sulfate is more controllable.
Compared with the traditional solid phase method relying on heat transfer, the method does not need calcination, overcomes the defects of long calcination time and uncontrollable particle size, and is not energy-saving and environment-friendly.
Compared with the traditional hydrothermal method, the method does not need subsequent calcination treatment of the material, and has the advantages of energy conservation and environmental protection.
(2) In the preparation method provided by the invention, a multi-stage heating mode is adopted, and the temperature T is the temperature 1 、T 2 And T 3 The stage (the heat-preserving stage after the temperature rise) is carried out with three times of crystal nucleus generation, and the crystal nucleus grows gradually in the subsequent microwave solvothermal reaction stage. Since the nucleation stages are different, the time for growing the crystal nucleus is different in each stage, and the prepared sodium iron sulfate has three-level particle size distribution, namely, large, medium and small particles with three particle sizes. The invention realizes the preparation of the sodium ferric sulfate material with different particle size combinations under mild conditions. This optimized combination of different sizes is beneficial to increasing the tap density of the positive electrode. The positive electrode material is used in a sodium ion battery, and the mass specific energy and the volume specific energy of the positive electrode material are obviously improved.
(3) The preparation method provided by the invention has the advantages of simple process, quick reaction, high product purity, controllable particle size distribution and high tap density; and has excellent electrochemical properties including high discharge specific capacity at high charge rate, good rate performance, good cycling stability, etc.
In the invention, the sodium source, the iron source and the sulfur source can be respectively from three compounds, or can be from one or two compounds; for example, sodium sulfate contains both sulfur and sodium, so the addition of sodium sulfate corresponds to the addition of a sodium source and a sulfur source.
According to some embodiments of the invention, the sodium source comprises a soluble sodium salt.
According to some embodiments of the invention, the sodium source comprises at least one of sodium carbonate, sodium bicarbonate, sodium acetate, sodium oxalate, sodium citrate, sodium nitrate, sodium sulfate, sodium bisulfate, and hydrates thereof.
According to some embodiments of the invention, the sodium source comprises sodium sulfate.
According to some embodiments of the invention, the iron source comprises at least one of a ferrous salt and a ferric salt.
According to some embodiments of the invention, the iron source comprises at least one of a soluble ferrous salt and a soluble ferric salt.
According to some embodiments of the invention, the iron source comprises at least one of ferrous sulfate, ferric sulfate, ferrous ammonium sulfate, ferric ammonium sulfate, ferrous nitrate, ferric nitrate, ferrous chloride, ferric ammonium citrate, and hydrates thereof.
Wherein the hydrate comprises at least one of ferrous sulfate heptahydrate, ferrous nitrate hexahydrate, ferrous chloride tetrahydrate, ferrous ammonium sulfate hexahydrate, ferric chloride hexahydrate and ferric nitrate nonahydrate.
According to some embodiments of the invention, the iron source comprises ferrous sulfate hydrate. Ferrous sulfate heptahydrate may be particularly useful.
According to some embodiments of the invention, the sulfur source comprises at least one of sodium sulfate, sodium bisulfate, ammonium sulfate, ferric sulfate, ferrous ammonium sulfate, ferric ammonium sulfate, and hydrates thereof.
According to some embodiments of the invention, the sulfur source comprises sodium sulfate and/or ferrous sulfate hydrate.
According to some embodiments of the invention, the antioxidant comprises at least one of ascorbic acid, citric acid, oxalic acid, sodium sulfite, sodium D-erythorbate, sodium bisulfite, hydrazine, and paraformaldehyde.
According to some embodiments of the invention, the antioxidant comprises ascorbic acid.
According to some embodiments of the invention, the solvent of the mixed solution is at least one of water, an alcohol solvent, a carboxylic acid solvent, and a ketone solvent.
According to some embodiments of the invention, the solvent of the mixed solution comprises at least one of water, methanol, ethanol, acetone, ethylene glycol, a polyethylene glycol-water mixture, propylene glycol, diethylene glycol, triethylene glycol, glycerol, and butanetriol.
According to some embodiments of the invention, the solvent of the mixed solution is water.
According to some embodiments of the invention, the solvent of the mixed solution is a mixture of water and ethanol. Wherein the volume ratio of the water to the ethanol is 1:0.8-1.2. For example, it may be about 1:1.
According to some embodiments of the invention, the concentration of iron in the mixed solution is 0.01-10 mol/L.
According to some embodiments of the invention, the concentration of iron in the mixed solution is 0.1 to 5mol/L.
According to some embodiments of the invention, the concentration of iron in the mixed solution is 0.5-2 mol/L.
According to some embodiments of the invention, the concentration of iron in the mixed solution is 0.8 to 1.5mol/L. Further specifically, about 1mol/L is possible.
According to some embodiments of the invention, the molar ratio of iron to sodium in the mixed solution is 1 (0.83-1.2). And more specifically may be about 1:1.
According to some embodiments of the invention, the molar ratio of iron to sulfur in the mixed solution is 1 (1-2).
According to some embodiments of the invention, the molar ratio of iron to sulfur in the mixed solution is 1:1.4 to 1.6. And more specifically may be about 1:1.5.
Wherein the presence of iron, sodium, sulfur includes free ionic state, or ions containing the above elements, or compounds containing the above elements. And the molar ratio of iron, sodium and sulfur is not strictly limited, as long as the ratio of sodium iron sulfate can be prepared.
According to some embodiments of the invention, the antioxidant comprises 0.1-20% of iron in the mixed solution.
According to some embodiments of the invention, the antioxidant comprises 1-10% of iron in the mixed solution. For example, the content may be specifically 2 to 5%.
According to some embodiments of the invention, the method of formulating the mixed solution comprises mixing the sodium source, the iron source, the sulfur source, the antioxidant, and the solvent. Wherein,
the method of mixing includes at least one of acoustic, magnetic stirring, mechanical stirring, and thermal diffusion. For example, magnetic stirring may be used.
The mixing time period is not limited as long as it can be completely dissolved, and a mixed solution can be obtained.
According to some embodiments of the invention, in the microwave solvothermal reaction, the temperature T 1 220-300 ℃. For example, it may be about 250 ℃.
According to some embodiments of the invention, in the microwave solvothermal reaction, at a temperature T 1 The heat preservation time is 30-120 min.
According to some embodiments of the invention, in the microwave solvothermal reaction, at a temperature T 1 The heat preservation time is 35-50 min. For example, it may be about 40 minutes.
According to some embodiments of the invention, temperature T 1 ’ 150-170 ℃. For example, it may be about 160 ℃.
According to some embodiments of the invention, temperature T 1 Temperature T 1 ’ 。
According to some embodiments of the invention, in the microwave solvothermal reaction, at a temperature T 1 ’ The heat preservation time is 2-60 min.
According to some embodiments of the invention, in the microwave solvothermal reaction, at a temperature T 1 ’ The heat preservation time is 5-30 min.
According to some embodiments of the invention, temperature T 2 220-300 ℃. For example, it may be about 250 ℃.
According to some embodiments of the invention, temperatureT 2 Temperature T 1 ’ 。
According to some embodiments of the invention, in the microwave solvothermal reaction, at a temperature T 2 The heat preservation time is 20-120 min.
According to some embodiments of the invention, in the microwave solvothermal reaction, at a temperature T 2 The heat preservation time is 30-60 min. For example, it may be about 40 minutes.
According to some embodiments of the invention, temperature T 2 ’ 150-170 ℃. For example, it may be about 160 ℃.
According to some embodiments of the invention, temperature T 2 Temperature T 2 ’ 。
According to some embodiments of the invention, in the microwave solvothermal reaction, at a temperature T 2 ’ The heat preservation time is 2-60 min.
According to some embodiments of the invention, in the microwave solvothermal reaction, at a temperature T 2 ’ The heat preservation time is 4-30 min. For example, the time period may be specifically 5 to 10 minutes.
According to some embodiments of the invention, T 3 220-300 ℃. For example, it may be about 250 ℃.
According to some embodiments of the invention, temperature T 3 Temperature T 2 ’ 。
According to some embodiments of the invention, in the microwave solvothermal reaction, at a temperature T 3 The heat preservation time is 10-30 min.
As is clear from the above description, in the microwave solvothermal reaction employed in the present invention, heating to T is sequentially performed 1 Preserving heat and cooling to T 1 ’ Preserving the temperature; heated to T 2 Preserving heat after temperature, and cooling to T 2 ’ Preserving the temperature; finally heat to T 3 And (5) temperature preservation.
According to some embodiments of the invention, the microwave solvothermal reaction, the heating method comprises an oscillating heating method.
According to some embodiments of the invention, the preparing method further comprises sequentially performing solid-liquid separation, washing the solid product, and drying after the microwave solvothermal reaction.
According to some embodiments of the invention, the method of solid-liquid separation comprises at least one of filtration and centrifugation. Wherein the filtering comprises at least one of suction filtration and pressure filtration.
According to some embodiments of the invention, the washing employs a detergent that is at least one of water and ethanol.
According to some embodiments of the invention, the washing employs a detergent that is ethanol.
According to some embodiments of the invention, the method of drying comprises at least one of vacuum drying, forced air drying, and freeze drying. The drying method may have a small influence on the particle size of the sodium iron sulfate, but the changing conditions in the same drying method have little influence on the particle size of the sodium iron sulfate.
According to some embodiments of the invention, the method of drying is forced air drying. The temperature of the blast drying is 25-120 ℃.
According to an embodiment of the second aspect of the present invention, there is provided sodium iron sulfate produced by the production method, the tap density of the sodium iron sulfate being not less than 0.8g/cm 3 。
The sodium iron sulfate adopts all the technical schemes of the preparation method of the embodiment, so that the sodium iron sulfate has at least all the beneficial effects brought by the technical schemes of the embodiment. The obtained sodium iron sulfate has higher tap density, and when the sodium iron sulfate is used for a positive electrode material of a sodium ion battery, the sodium ion battery has higher rate capability, cycle performance and capacity density.
According to some embodiments of the invention, the tap density of the sodium iron sulfate is between 0.8 and 0.9g/cm 3 In particular, for example, about 0.81g/cm 3 、0.82g/cm 3 、0.83g/cm 3 、0.84g/cm 3 、0.85g/cm 3 、0.86g/cm 3 、0.87g/cm 3 、0.88g/cm 3 Or 0.89g/cm 3 。
According to an embodiment of the third aspect of the present invention, there is provided an application of the preparation method in preparing a positive electrode material of a sodium ion battery.
The application adopts all the technical schemes of the preparation method of the embodiment, so that the preparation method has at least all the beneficial effects brought by the technical schemes of the embodiment. The sodium ion positive electrode material in the application is good in performance.
According to an embodiment of the fourth aspect of the present invention, there is provided a sodium ion battery positive electrode sheet, wherein the preparation raw materials of the sodium ion battery positive electrode sheet include sodium iron sulfate prepared by the preparation method.
The sodium ion battery positive plate adopts all the technical schemes of the sodium iron sulfate in the embodiment, so that the sodium ion battery positive plate has at least all the beneficial effects brought by the technical schemes of the embodiment. Namely, has excellent high-rate discharge gram specific capacity and high-rate cycle performance.
According to some embodiments of the invention, the positive electrode sheet of the sodium ion battery comprises a positive electrode current collector and a positive electrode material layer coated on the positive electrode current collector.
According to some embodiments of the invention, the positive electrode material layer comprises a sodium ion battery positive electrode material, a conductive agent, and a binder.
According to some embodiments of the invention, the conductive agent accounts for 2-15% of the positive electrode material layer by mass. For example, it may be about 10%.
According to some embodiments of the invention, the conductive agent comprises at least one of carbon black, carbon nanotubes, and graphene.
According to some embodiments of the invention, the binder accounts for 2-15% of the positive electrode material layer by mass. For example, it may be about 10%.
According to some embodiments of the invention, the binder comprises PVDF.
The mass percentage sum of the positive electrode material layer of the sodium ion battery, the conductive agent and the binder is 100%.
According to some embodiments of the invention, the sodium ion battery positive electrode material comprises the sodium iron sulfate.
Further, the sodium ion battery positive electrode material may further include at least one of a Prussian blue positive electrode material, a layered oxide, and an organic positive electrode material. The sodium iron sulfate can be used as a positive electrode material of a sodium ion battery independently or can be mixed with a traditional material to be used as the positive electrode material of the sodium ion battery.
According to an embodiment of the fifth aspect of the present invention, there is provided a sodium ion battery, the preparation raw material of which includes sodium iron sulfate prepared by the preparation method.
The sodium ion battery adopts all the technical schemes of the sodium iron sulfate in the embodiment, so that the sodium ion battery has at least all the beneficial effects brought by the technical schemes of the embodiment.
According to some embodiments of the invention, the sodium-ion battery comprises at least one of a sodium-ion half-cell and a sodium-ion full-cell.
According to some embodiments of the invention, the sodium-ion half-cell comprises the sodium-ion cell positive electrode sheet, a separator and a sodium metal sheet in a stacked arrangement.
According to some embodiments of the invention, the sodium-ion full cell comprises a positive plate, a separator and a negative plate of the sodium-ion cell arranged in a superimposed manner.
According to some embodiments of the invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer.
According to some embodiments of the invention, the negative electrode material layer includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder. Wherein,
the negative active material includes at least one of graphite and hard carbon.
The negative electrode conductive agent includes at least one of carbon black, carbon nanotubes, and graphene.
The negative electrode binder includes PVDF.
The negative electrode conductive agent accounts for 2-15% of the negative electrode material layer by mass percent. For example, it may be about 10%.
The negative electrode binder accounts for 2-15% of the negative electrode material layer by mass percent. For example, it may be about 10%.
The sum of the mass percentages of the anode active material, the anode conductive agent and the anode binder in the anode material layer is 100%.
According to some embodiments of the invention, in the sodium ion half-cell, the gram specific capacity of the sodium iron sulfate as a positive electrode material at 2C rate is more than or equal to 85mAh/g.
According to some embodiments of the invention, in the sodium ion half-cell, the sodium iron sulfate has a gram specific capacity of 85-100 mAh/g as a positive electrode material at 2C rate. For example, about 95mAh/g, 91mAh/g, 90mAh/g, 89mAh/g, 88mAh/g, 87mAh/g or 86mAh/g may be mentioned.
According to some embodiments of the invention, in the sodium ion half-cell, the gram specific capacity of the sodium iron sulfate as a positive electrode material at 5C rate is equal to or greater than 80mAh/g.
According to some embodiments of the invention, in the sodium ion half-cell, the sodium iron sulfate has a gram specific capacity of 80-90 mAh/g as a positive electrode material at a 5C rate. For example, about 86mAh/g, 85mAh/g, 84mAh/g, 83mAh/g or 82mAh/g may be mentioned.
According to some embodiments of the invention, in the sodium ion half-cell, the gram specific capacity of the sodium iron sulfate as a positive electrode material at 10C rate is more than or equal to 70mAh/g.
According to some embodiments of the invention, in the sodium ion half-cell, the sodium iron sulfate has a gram specific capacity of 72-80 mAh/g at 10C rate as a positive electrode material. For example, about 79mAh/g, 78mAh/g, 77mAh/g, 76mAh/g, 75mAh/g or 74mAh/g may be mentioned.
According to some embodiments of the invention, in the sodium ion half-cell, the capacity retention rate of the sodium iron sulfate serving as a positive electrode material after 500 weeks circulation is equal to or greater than 78%. For example, it may be about 81%, 80.5%, 80%, 79.5%, 79%, 78.5%, 78%, 77.2%, 77%, 76.5% or 76%. According to some embodiments of the invention, in the sodium ion full cell, the gram specific capacity of the sodium iron sulfate serving as a positive electrode material at 2C multiplying power is more than or equal to 80mAh/g.
According to some embodiments of the invention, in the sodium ion full cell, the gram specific capacity of the sodium iron sulfate as a positive electrode material at 2C rate is between 80 and 90 mAh/g. For example, about 86mAh/g, 85mAh/g, 84mAh/g, 83mAh/g, 82mAh/g or 81mAh/g may be mentioned.
According to some embodiments of the invention, in the sodium ion full cell, the gram specific capacity of the sodium iron sulfate serving as a positive electrode material at 5C rate is more than or equal to 75mAh/g.
According to some embodiments of the invention, in the sodium ion full cell, the gram specific capacity of the sodium iron sulfate as a positive electrode material at 5C rate is 75-85 mAh/g. For example, about 82mAh/g, 81mAh/g, 80mAh/g, 79mAh/g or 78mAh/g may be mentioned.
According to some embodiments of the invention, in the sodium ion full cell, the gram specific capacity of the sodium iron sulfate serving as a positive electrode material at 10C rate is more than or equal to 70mAh/g.
According to some embodiments of the invention, in the sodium ion full cell, the gram specific capacity of the sodium iron sulfate as a positive electrode material at a 10C rate is 70-80 mAh/g. For example, about 75mAh/g, 74mAh/g, 73mAh/g, 72mAh/g or 71mAh/g may be mentioned.
According to some embodiments of the invention, in the sodium ion full cell, the capacity retention rate of the sodium iron sulfate serving as a positive electrode material after 250 weeks circulation is more than or equal to 78 percent at a 5C rate. For example, about 82%, 81.5%, 81%, 80.5%, 80%, 79.5%, 79%, 78.5%, 78%, 77.2%, 77%, 76.5% or 76% may be mentioned.
According to an embodiment of the sixth aspect of the present invention, there is provided the use of the sodium ion battery in the power battery field, the energy storage battery field and the 3C electronics field.
The application adopts all the technical schemes of the sodium ion battery of the embodiment, so that the sodium ion battery has at least all the beneficial effects brought by the technical schemes of the embodiment.
According to some embodiments of the invention, the power battery field includes at least one of electric vehicles and two-wheeled electric bicycles.
According to some embodiments of the invention, the 3C electronics field includes mobile electronic communication devices.
According to some embodiments of the invention, the energy storage battery field includes energy storage power stations.
The term "about" as used herein, unless otherwise specified, means that the tolerance is within + -2%, for example, about 100 is actually 100 + -2%. Times.100.
Unless otherwise specified, the term "between … …" in the present invention includes the present number, for example "between 2 and 3" includes the end values of 2 and 3.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
FIG. 1 is a temperature profile of a microwave solvothermal method in example 1 of the present invention.
FIG. 2 is a schematic representation of the particle positions of sodium iron sulfate obtained in the examples of the present invention when stacked.
FIG. 3 is an XRD pattern of sodium iron sulfate obtained in example 1 of the present invention.
FIG. 4 is a graph showing the particle size distribution of sodium iron sulfate obtained in example 1 of the present invention.
Fig. 5 is a graph of the electrochemical performance of the sodium-ion battery obtained in example 40.
Detailed Description
The conception and the technical effects produced by the present invention will be clearly and completely described in conjunction with the embodiments below to fully understand the objects, features and effects of the present invention. It is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and that other embodiments obtained by those skilled in the art without inventive effort are within the scope of the present invention based on the embodiments of the present invention.
In the description of the present invention, the descriptions of the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Example 1
The embodiment prepares the sodium iron sulfate, which comprises the following specific steps:
s1, weighing 0.25mol of Na 2 SO 4 (Sulfur source and sodium source), 0.5mol FeSO 4 ·7H 2 Adding O (iron source and sulfur source) and 0.025mol of ascorbic acid into 500ml of water, and magnetically stirring to obtain a mixed solution;
s2, placing the mixed solution into a microwave reactor, heating to 250 ℃ and preserving heat for 40min, cooling to 160 ℃ and preserving heat for 5min; continuously heating to 250 ℃ and preserving heat for 30min, cooling to 160 ℃ and preserving heat for 5min; heating to 250deg.C and maintaining for 10min; the heating mode is oscillation heating. The temperature profile of this example is shown in FIG. 1, where t 1 Is the temperature T 1 The following incubation period, other symbols are explained herein; it should be noted that, the height and length of the curve in fig. 1 cannot accurately represent the height and length of the time of the temperature, and the specific parameters are based on the data recorded in this step.
S3, cooling to normal temperature, filtering, washing the solid material with ethanol, and drying in a forced air drying oven to obtain the target product. The temperature of the forced air drying is 25-120 ℃, and the performance of the obtained sodium iron sulfate is not affected in the range.
Example 2
This example produced a sodium iron sulfate, which differs from example 1 in that:
In step S1, the volume of water employed was 50mL.
Example 3
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S1, the volume of water employed was 5000mL.
Example 4
This example produced a sodium iron sulfate, which differs from example 1 in that:
0.25mol of Na in step S1 2 SO 4 And 0.5mol FeSO 4 ·7H 2 O is replaced by:
0.25mol Na 2 CO 3 、0.5mol FeSO 4 ·7H 2 O、0.25mol(NH 4 ) 2 SO 4 。
example 5
This example produced a sodium iron sulfate, which differs from example 1 in that:
0.25mol of Na in step S1 2 SO 4 、0.5mol FeSO 4 ·7H 2 O, 0.025mol ascorbic acid and 500ml water were replaced by:
0.05mol NaNO 3 、0.05mol FeSO 4 ·7H 2 O、0.025mol NH 4 HSO 4 0.0025mol ascorbic acid and 50ml water.
Example 6
This example produced a sodium iron sulfate, which differs from example 1 in that:
0.25mol of Na in step S1 2 SO 4 And 0.5mol FeSO 4 ·7H 2 O is replaced by:
0.25mol Na 2 SO 4 、0.5mol Fe(NO 3 ) 2 ·6H 2 O、0.5mol(NH 4 ) 2 SO 4 。
example 7
This example produced a sodium iron sulfate, which differs from example 1 in that: 0.25mol of Na in step S1 2 SO 4 And 0.5mol FeSO 4 ·7H 2 O is replaced by: 0.25mol Na 2 SO 4 、0.5mol FeCl 2 ·4H 2 O、0.5mol NH 4 HSO 4 。
Example 8
This example produced a sodium iron sulfate, which differs from example 1 in that: 0.25mol of Na in step S1 2 SO 4 And 0.5mol FeSO 4 ·7H 2 O is replaced by: 0.5mol NaHCO 3 、0.5mol Fe(NH 4 ) 2 (SO 4 ) 2 ·6H 2 O。
Example 9
This example produced a sodium iron sulfate, which differs from example 1 in that: 0.25mol of Na in step S1 2 SO 4 And 0.5mol FeSO 4 ·7H 2 O is replaced by: 0.5mol CH 3 COONa、0.5mol NH 4 Fe(SO 4 ) 2 。
Example 10
This example produced a sodium iron sulfate, which differs from example 1 in that: 0.25mol of Na in step S1 2 SO 4 And 0.5mol FeSO 4 ·7H 2 O is replaced by: 0.25mol Na 2 C 2 O 4 、0.5mol FeCl 3 ·6H 2 O、0.75mol(NH 4 ) 2 SO 4 。
Example 11
This example produced a sodium iron sulfate, which differs from example 1 in that: 0.25mol of Na in step S1 2 SO 4 And 0.5mol FeSO 4 ·7H 2 O is replaced by: 0.17mol C 6 H 5 Na 3 O 7 、0.5mol C 6 H 8 FeNO 7 、0.5mol NH 4 HSO 4 。
Example 12
This example produced a sodium iron sulfate, which differs from example 1 in that: 0.25mol of Na in step S1 2 SO 4 And 0.5mol FeSO 4 ·7H 2 O is replaced by: 0.5mol NaHSO 4 、0.5mol Fe(NO 3 ) 3 ·9H 2 O。
Example 13
This example produced a sodium iron sulfate, which differs from example 1 in that: in step S1, the amount of sodium sulfate was 0.3mol.
Example 14
This example produced a sodium iron sulfate, which differs from example 1 in that: in step S1, the amount of the substance of 7-hydrate iron sulfate was 0.6mol.
Example 15
This example produced a sodium iron sulfate, which differs from example 1 in that: in step S1, the amount of the substance of ascorbic acid was 0.005mol.
Example 16
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S1, the amount of the substance of ascorbic acid was 0.1mol.
Example 17
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S1, ascorbic acid is replaced with citric acid in an equal amount.
Example 18
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S1, ascorbic acid is replaced with hydrazine (CAS: 302-01-2) in an equal amount.
Example 19
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S1, ascorbic acid is replaced with oxalic acid in an equal amount.
Example 20
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S1, ascorbic acid is replaced with sodium sulfite in an equal amount.
Example 21
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S1, ascorbic acid is replaced with an equal amount of sodium D-erythorbate (CAS: 7378-23-6).
Example 22
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S1, ascorbic acid is replaced with an equal amount of sodium bisulphite (CAS: 7631-90-5).
Example 23
This example produced a sodium iron sulfate, which differs from example 1 in that:
In step S1, water is replaced with an equal volume of triethylene glycol.
Example 24
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S1, water is replaced with an equal volume of butanetriol.
Example 25
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S1, water is replaced with an equal volume of methanol.
Example 26
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S1, water is replaced with an equal volume of ethanol.
Example 27
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S1, water is replaced with an equal volume of acetone.
Example 28
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S1, water is replaced with an equal volume of ethylene glycol.
Example 29
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S1, water was replaced with an equal volume of a polyethylene glycol-water mixture (polyethylene glycol mass concentration in the mixture 0.2 g/L).
Example 30
This example produced a sodium iron sulfate, which differs from example 1 in that:
In step S1, water is replaced with an equal volume of propylene glycol.
Example 31
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S2, the heating method is as follows: heating to 200deg.C and maintaining the temperature for 120min, cooling to 100deg.C and maintaining the temperature for 2min; continuously heating to 200 ℃ and preserving heat for 100min, cooling to 100 ℃ and preserving heat for 2min; and then heated to 200 ℃ and kept for 30min.
Example 32
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S2, the heating method is as follows: heating to 250deg.C and maintaining the temperature for 120min, cooling to 100deg.C and maintaining the temperature for 60min; continuously heating to 350 ℃ and preserving heat for 30min, cooling to 180 ℃ and preserving heat for 60min; heating to 250deg.C and maintaining for 15min.
Example 33
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S2, the heating method is as follows: heating to 350deg.C and maintaining the temperature for 30min, cooling to 180deg.C and maintaining the temperature for 60min; continuously heating to 200 ℃ and preserving heat for 100min, cooling to 150 ℃ and preserving heat for 30min; and then heated to 300 ℃ and kept for 10min.
Example 34
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S2, the heating method is as follows: heating to 300 ℃ and preserving heat for 50min, cooling to 120 ℃ and preserving heat for 30min; continuously heating to 220 ℃ and preserving heat for 120min, cooling to 130 ℃ and preserving heat for 60min; and then heated to 350 ℃ and kept for 120min.
Example 35
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S3, the solid material is washed with water.
Example 36
This example produced a sodium iron sulfate, which differs from example 1 in that:
in the step S3, the drying mode is vacuum drying, and the vacuum drying temperature is within the range of 25-120 ℃ and has no obvious influence on the performance of the obtained sodium iron sulfate.
Example 37
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S3, the drying method is freeze drying.
Example 38
This example produced a sodium iron sulfate, which differs from example 1 in that:
in step S1, 500mL of water was replaced with a mixed solution of 50mL of water and 50mL of ethanol.
Example 39
This example produced a sodium iron sulfate, which differs from example 31 in that:
in step S1, 500mL of water was replaced with a mixed solution of 50mL of water and 50mL of ethanol.
Example 40
The sodium ion battery is prepared by the method specifically comprises the following steps:
preparing a positive plate of the sodium ion battery: adding 16g of sodium ferric sulfate powder, 2g of carbon black and 2g of polyvinylidene fluoride into 20mL of nitrogen methyl pyrrolidone, and fully grinding to obtain uniform slurry; the slurry was uniformly coated on the surface of an aluminum foil (positive electrode current collector) and then vacuum-dried. Cutting the electrode plate obtained by drying into a wafer with the diameter of 10mm, compacting and taking the wafer as a battery anode plate for standby. The sodium iron sulfate used in this example was from example 1.
A diaphragm: the glass fiber film was cut into a disk with a diameter of 16mm and used as a separator.
Preparing an electrolyte: 12.244g of sodium perchlorate is weighed and dissolved in 95mL of propylene carbonate, 5mL of fluoroethylene carbonate is added as an additive, and the mixture is fully and uniformly mixed to be used as electrolyte for standby.
Preparing a sodium ion battery negative plate: pressing sodium metal into slices, cutting into wafers with the diameter of 12mm, and taking the wafers as the negative electrode of the battery for standby;
and (3) battery assembly: and in a glove box protected by inert gas, the prepared battery anode, the prepared diaphragm and the prepared battery cathode are sequentially and tightly stacked, electrolyte is dripped to completely infiltrate the diaphragm, and then the stacked part is sealed into a button battery shell to complete battery assembly.
Example 41
This example produced a sodium ion battery, which differs from example 40 in that: the sodium iron sulfate used in this example was from example 2.
Example 42
This example produced a sodium ion battery, which differs from example 40 in that: the sodium iron sulfate used in this example was from example 3.
Example 43
This example produced a sodium ion battery, which differs from example 40 in that: the sodium iron sulfate used in this example was from example 4.
Example 44
This example produced a sodium ion battery, which differs from example 40 in that: the sodium iron sulfate used in this example was from example 5.
Example 45
This example produced a sodium ion battery, which differs from example 40 in that: the sodium iron sulfate used in this example was from example 7.
Example 46
This example produced a sodium ion battery, which differs from example 40 in that: the sodium iron sulfate used in this example was from example 9.
Example 47
This example produced a sodium ion battery, which differs from example 40 in that: the sodium iron sulfate used in this example was from example 13.
Example 48
This example produced a sodium ion battery, which differs from example 40 in that: the sodium iron sulfate used in this example was from example 15.
Example 49
This example produced a sodium ion battery, which differs from example 40 in that: the sodium iron sulfate used in this example was from example 17.
Example 50
This example produced a sodium ion battery, which differs from example 40 in that: the sodium iron sulfate used in this example was from example 21.
Example 51
This example produced a sodium ion battery, which differs from example 40 in that:
the sodium iron sulfate used in this example was from example 25.
Example 52
This example produced a sodium ion battery, which differs from example 40 in that:
the sodium iron sulfate used in this example was from example 27.
Example 53
This example produced a sodium ion battery, which differs from example 40 in that:
the sodium iron sulfate used in this example was from example 30.
Example 54
This example produced a sodium ion battery, which differs from example 40 in that:
the sodium iron sulfate used in this example was from example 32.
Example 55
This example produced a sodium ion battery, which differs from example 40 in that:
the sodium iron sulfate used in this example was from example 34.
Example 56
This example produced a sodium ion battery, which differs from example 40 in that:
the sodium iron sulfate used in this example was from example 37.
Example 57
This example produced a sodium ion battery, which differs from example 40 in that:
the sodium iron sulfate used in this example was from example 39.
Example 58
This example produced a sodium ion battery, which differs from example 40 in that:
the preparation method of the sodium ion battery negative plate comprises the following steps: adding 8g of hard carbon, 1g of carbon black and 1g of polyvinylidene fluoride into 10mL of nitrogen methyl pyrrolidone, and fully grinding to obtain uniform slurry; uniformly coating the slurry on the surface of an aluminum foil (negative electrode current collector), and then drying in vacuum; cutting the electrode plate obtained by drying into a circular plate with the diameter of 12mm, compacting and then taking the circular plate as a negative plate of the sodium ion battery for standby.
Example 59
This example produced a sodium ion battery, which differs from example 58 in that:
the sodium iron sulfate used in this example was from example 5.
Example 60
This example produced a sodium ion battery, which differs from example 58 in that:
the sodium iron sulfate used in this example was from example 10.
Example 61
This example produced a sodium ion battery, which differs from example 58 in that:
the sodium iron sulfate used in this example was from example 15.
Example 62
This example produced a sodium ion battery, which differs from example 58 in that:
the sodium iron sulfate used in this example was from example 20.
Example 63
This example produced a sodium ion battery, which differs from example 58 in that:
the sodium iron sulfate used in this example was from example 25.
Example 64
This example produced a sodium ion battery, which differs from example 58 in that:
the sodium iron sulfate used in this example was from example 30.
Example 65
This example produced a sodium ion battery, which differs from example 58 in that:
the sodium iron sulfate used in this example was from example 35.
Example 66
This example produced a sodium ion battery, which differs from example 58 in that:
The sodium iron sulfate used in this example was from example 39.
Comparative example 1
The traditional ball milling solid phase method is adopted in the example to prepare the sodium ferric sulfate, and the specific steps are as follows:
weigh 0.25mol Na 2 SO 4 、0.5mol FeSO 4 ·7H 2 O and 0.025mol of ascorbic acid, and ball milling for 6 hours by using acetone as a medium; dried under vacuum and then heated under a continuous stream of Ar at 350℃for 24h.
The sodium iron sulfate prepared was assembled into sodium ion batteries according to examples 40 and 58, respectively.
Comparative example 2
The traditional liquid phase method is adopted to prepare the sodium iron sulfate, and the specific steps are as follows:
will 0.05mol Na 2 SO 4 、0.1mol FeSO 4 ·7H 2 Dissolving O and 0.005mol of vitamin C in 100mL of distilled water, performing ultrasonic treatment for 30min, and fully coprecipitating; filtering, washing a solid product with ethanol, and vacuum drying at 60 ℃ to obtain a precursor; after pre-sintering at 200 ℃ for 2H, in Ar/H 2 (5%) annealing at 400℃for 8h.
The sodium iron sulfate prepared was assembled into sodium ion batteries according to examples 40 and 58, respectively.
Comparative example 3
The common microwave solvothermal method is adopted to prepare the sodium iron sulfate, and the specific method is as follows:
weigh 0.25mol Na 2 SO 4 、0.5mol FeSO 4 ·7H 2 Adding O and 0.025mol of ascorbic acid into 500ml of water, and magnetically stirring uniformly to obtain a mixed solution; placing the mixed solution in a microwave hydrothermal reactor, heating to 250 ℃ and preserving heat for 90min; cooling to normal temperature, filtering, washing with ethanol, and drying in a forced air drying oven to obtain sodium ferric sulfate A polar material.
The sodium iron sulfate prepared was assembled into sodium ion batteries according to examples 40 and 58, respectively.
Test case
This example first tested the tap density tests of sodium iron sulfate obtained in examples 1-39 and comparative examples 1-3. The test follows GB/T5162-2006, a wet Rise-801 tap density instrument is adopted, and the amplitude is 3mm; vibration frequency: 250 times/min; measuring cylinder: 25mL. The test results are shown in Table 1.
TABLE 1 tap Density of sodium iron sulfate obtained in examples 1-39 and comparative examples 1-3
As can be seen from Table 1, the sodium iron sulfate positive electrode materials prepared in examples 1-39 of the present invention by the microwave solvothermal method of oscillation heating and adopting different raw materials and preparation conditions have high tap density, and are not less than 0.80g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The compacted density of the sodium ferric sulfate anode material prepared by other methods is lower than 0.70g/cm 3 . The possible reason is that the microwave method provided by the invention is directly added from the inside of the system through the interaction of microwaves and a medium, so that the preparation system is heated uniformly and rapidly. In addition, the multi-stage heating is realized by the oscillation mode, and the temperature is maintained at the time of primary heating (T 1 ) Forming a first-stage crystal nucleus and growing; when the temperature is kept for the second time (T) 2 ) The first-stage crystal nucleus continues to grow large, and a second-stage crystal nucleus is formed and grows; in the third heating and heat preservation (T) 3 ) The first and second crystal nuclei continue to grow and form third crystal nuclei and grow, and finally the sodium iron sulfate particles with three different grain sizes are formed. The three are mutually matched, so that the space utilization rate is effectively improved, and the positive electrode material with high tap density is formed, and the positive electrode material is specific: the large particles are adjacent to each other, the medium particles are filled in the gaps formed by the large particles, and the small particles are filled in the smaller gaps formed by the large particles and the medium particles. The positional relationship among the particles is schematically shown in FIG. 2.
The XRD patterns of the sodium iron sulfate obtained in the examples are also tested, and the results show that the patterns of all the examples are hardly different, and the sodium iron sulfate patterns obtained in the examples have good correspondence with the standard patterns of the sodium iron sulfate, so that the sodium iron sulfate prepared in the invention has higher cleanliness and purity. The XRD pattern of the sodium iron sulfate obtained in example 1 is shown in FIG. 3.
The particle size distribution of the sodium iron sulfate obtained in the examples was also tested in this example. The environment is a constant temperature and humidity room (25 ℃ and 35%) by adopting a European and American pearl sea NS-90Z nanometer granularity and potential analyzer. The results show that all the samples obtained in the examples exhibit a three-level distribution of particle sizes. The grain distribution of the sodium iron sulfate obtained in example 1 is shown in fig. 4.
The electrochemical properties of the obtained sodium ion batteries of examples 40 to 66 and comparative examples 1 to 3 were also tested in this example. Wherein the constant-current charge and discharge test adopts a BTSDA test system of Shenzhen Xinwei electronic Co Ltd, the environment is a constant temperature and humidity room (25 ℃, 35%), and the load capacity of the positive plate of the sodium ion battery is 6-8 mg/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the Examples 40 to 57 and comparative examples 1 to 2 were charged and discharged at rates of 2C, 5C and 10C (1c=120 mAh/g), and the voltage range tested was 2.0 to 4.5V. The positive and negative electrode N/P ratios in examples 58 to 66 and comparative examples 1 to 2 were 1.2, and the battery charge and discharge rates were 2C, 5C, and 10C (1c=120 mAh/g), and the voltage ranges tested were 1.5 to 4.1V. The test results are shown in tables 2 to 3.
Table 2 electrochemical performance of sodium ion half-cells
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The results in Table 2 show that the sodium ion half cell has a first coil capacity of 86-91 mAh/g at 2C, a first coil capacity of 82-86 mAh/g at 5C, a first coil capacity of 74-79 mAh/g at 10C, and a 500-coil capacity retention of 75.98-80.51% at 5C. Namely, the sodium iron sulfate prepared by the invention is used as a positive electrode active material, and can exert excellent capacity, high rate performance and cycle performance when in a half cell. Among them, the capacity retention and coulombic efficiency of the sodium ion battery obtained in example 40 are shown in fig. 5.
TABLE 3 electrochemical Properties of sodium ion full cells
The results in Table 3 show that the initial coil capacity obtained in the sodium ion full cell 2C is 81-85 mAh/g, the initial coil capacity obtained in the sodium ion full cell 2C is 78-81 mAh/g, the initial coil capacity obtained in the sodium ion full cell 10C is 70-75 mAh/g, and the capacity retention rate in the sodium ion full cell 2C is about 78.34-81.65%. Therefore, the sodium iron sulfate prepared by the method can be used as a positive electrode active material, and can exert excellent capacity, high rate performance and cycle performance in a sodium ion full battery.
The results in tables 2 to 3 are combined to show that the concentration of the raw materials for preparing the sodium iron sulfate and the concentration of the mixed aqueous solution are different, so that the performance of the sodium ion half cell and the performance of the sodium ion full cell are slightly influenced, but the obtained sodium iron sulfate can show excellent electrochemical performance. However, the sodium ion batteries assembled in comparative examples 1 to 3 have poor performance, probably because the inter-particle voids formed by the low tap density are large, resulting in discontinuous sodium ion transport, thereby affecting specific capacity and capacity retention.
In conclusion, the sodium ferric sulfate prepared by combining oscillation heating with a microwave solvothermal method has the advantages of high charge-discharge specific capacity, good rate capability, good cycle stability and the like when the sodium ferric sulfate is used as a positive electrode active material of a sodium ion battery. In addition, the oscillating microwave method adopted by the invention can be used for preparing the ferric sodium sulfate anode material with controllable morphology and size under mild conditions, and has the advantages of simple process, rapid reaction, low cost and good product performance. The prepared sodium iron sulfate can be used as a positive electrode material of a sodium ion battery, and the sodium ion battery comprising the positive electrode material of the sodium iron sulfate is expected to be widely applied to the fields of power batteries, energy storage batteries and 3C.
The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of one of ordinary skill in the art without departing from the spirit of the present invention. Furthermore, embodiments of the invention and features of the embodiments may be combined with each other without conflict.

Claims (15)

1. The preparation method of the sodium iron sulfate is characterized by comprising the steps of carrying out microwave solvothermal reaction on a mixed solution of a sodium source, an iron source, a sulfur source and an antioxidant;
the microwave solvothermal reaction is sequentially carried out on T 1 、T 1 ’ 、T 2 、T 2 ’ And T 3 The temperature is kept; wherein,
temperature T 1 、T 2 、T 3 Each independently selected from 200-350 ℃;
temperature T 1 ’ 、T 2 ’ Each independently selected from 100-180 ℃;
at temperature T 1 The heat preservation time is 30-120 min; at temperature T 2 The heat preservation time is 20-120 min; at temperature T 3 The heat preservation time is 10-30 min; at temperature T 1 ’ And T 2 ’ The heat preservation time is respectively and independently selected from 2-60 min.
2. The preparation method according to claim 1, wherein the molar ratio of iron to sodium in the mixed solution is 1 (0.83-1.2); and/or, in the mixed solution, the molar ratio of iron to sulfur is 1 (1-2).
3. The method according to claim 1, wherein the concentration of iron in the mixed solution is 0.01 to 10mol/L; and/or, the antioxidant accounts for 0.1-20% of the mole ratio of iron in the mixed solution.
4. The method according to any one of claims 1 to 3, wherein the solvent of the mixed solution is at least one of water, an alcohol solvent, a carboxylic acid solvent and a ketone solvent.
5. A method of preparation according to any one of claims 1 to 3, wherein the sodium source comprises a soluble sodium salt; and/or the sodium source comprises at least one of sodium carbonate, sodium bicarbonate, sodium acetate, sodium oxalate, sodium citrate, sodium nitrate, sodium sulfate, sodium bisulfate, and hydrates thereof.
6. A method of preparing according to any one of claims 1 to 3, wherein the iron source comprises at least one of a ferrous salt and a ferric salt; and/or the iron source comprises at least one of ferrous sulfate, ferric sulfate, ferrous ammonium sulfate, ferric ammonium sulfate, ferrous nitrate, ferric nitrate, ferrous chloride, ferric ammonium citrate, and hydrates thereof.
7. A method of preparing according to any one of claims 1 to 3, wherein the sulfur source comprises at least one of sodium sulfate, sodium bisulfate, ammonium sulfate, ferric sulfate, ferrous ammonium sulfate, ferric ammonium sulfate, and hydrates thereof.
8. A method according to any one of claims 1 to 3, wherein the antioxidant comprises at least one of ascorbic acid, citric acid, oxalic acid, sodium sulfite, sodium D-erythorbate, sodium bisulphite, hydrazine and paraformaldehyde.
9. A method according to any one of claims 1 to 3, further comprising sequentially performing solid-liquid separation, washing the solid product, and drying after the microwave solvothermal reaction.
10. The method according to claim 9, wherein the washing agent used for washing is at least one of water and ethanol; and/or the method of drying includes at least one of vacuum drying, forced air drying, and freeze drying.
11. The sodium iron sulfate produced by the production process according to any one of claims 1 to 10, wherein the tap density of the sodium iron sulfate is not less than 0.8g/cm 3 。
12. Use of a preparation method according to any one of claims 1 to 10 for the preparation of a positive electrode material for sodium ion batteries.
13. The positive plate of the sodium ion battery, which is characterized in that the preparation raw materials of the positive plate of the sodium ion battery comprise sodium iron sulfate prepared by the preparation method according to any one of claims 1 to 10.
14. A sodium ion battery, wherein the preparation raw material of the sodium ion battery comprises sodium iron sulfate prepared by the preparation method of any one of claims 1 to 10.
15. Use of a sodium ion battery according to claim 14 in the field of power batteries, energy storage batteries and 3C electronics.
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