CN115132981A - Binary doped iron-based fluorophosphate sodium ion positive electrode material and preparation method thereof - Google Patents
Binary doped iron-based fluorophosphate sodium ion positive electrode material and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a binary doped iron-based fluorophosphate sodium ion anode material expressed as Na 2 Fe 1‑x‑y M x N y PO 4 F @ C of Na 2 Fe 1‑x‑y M x N y PO 4 F is obtained after surface carbon coating, wherein M is Mn, and x is more than or equal to 0.02 and less than or equal to 0.10; n is selected from at least one of Ni, Co, Cu, Zn and Ti, y is more than or equal to 0.005 and less than or equal to 0.05, and @ C represents carbon coating. The invention obviously improves the reversible specific capacity of the prepared anode material through binary doping, and particularly can improve the reversible specific capacity under high rateThe inverse specific capacity is beneficial to developing the industrialization of the sodium ion battery; in addition, the invention carries out carbon coating on the anode material, takes polysaccharide and imidazoline surfactant as a compound carbon source, can obtain a uniform and compact carbon coating layer, and obviously improves the circulation stability.
Description
Technical Field
The invention relates to a sodium ion battery anode material, in particular to a binary doped iron-based fluorophosphate sodium ion anode material and a preparation method thereof.
Background
The sodium ion battery has the advantages of rich resources, low cost, high cost performance and the like, and has good application prospect. The working principle of the sodium ion battery is similar to that of the lithium ion battery, and the energy density of the sodium ion battery is determined by the anode material. Compared with the transition metal layered oxide anode material, the polyanion compound has the advantages of higher working voltage, stable three-dimensional structural framework, relatively low cost and high safety. The polyanion type sodium ion positive electrode material has higher theoretical specific capacity and good safety, and is a research hotspot of the positive electrode material of the sodium ion battery at present.
The polyanionic compound is composed of polyanionic group and transition metal element, and is anion polyhedron [ XOx] n- The frame structure material formed by the transition metal-oxygen polyhedron is applied to the positive electrode material of the sodium ion battery, and has the following advantages: 1) the framework structure of the X-O covalent bond has higher stability, so that the safety of the prepared sodium ion battery is further improved; 2) The polyanion compound has abundant crystal lattice vacancies, and can relieve the capacity reduction of the battery caused by repeated embedding and releasing of sodium ions in the charge and discharge processes; 3) the polyanion has an inducing effect, which increases the redox potential of the transition metal example. However, in the polyanionic sodium ion positive electrode material, a polyhedron formed by transition metal and oxygen atoms is blocked by anion tetrahedron, electron cloud of the transition metal is in a discontinuous state to block electron exchange, and an electron transmission path is lacked, so that the electron conductivity is low, the diffusion kinetics of sodium ions are slow, and the specific capacity and the rate capability of the sodium ion battery are limited. Therefore, for the polyanion sodium ion positive electrode material, the lower limit of the multiplying power performance of the positive electrode material is determined by the intrinsic property of the material, so that the improvement of the electronic conductivity is the key for improving the polyanion positive electrode material, the multiplying power performance is further improved, the capacity is improved, and the method has very important significance.
Fluorophosphate-type positive electrode material Na 2 MPO 4 F has higher theoretical capacity, higher working voltage and cheap and easily obtained raw materials, and is a sodium ion anode material with a prospect at present. Wherein the iron group isFluorophosphate Na 2 FePO 4 F has a value of 124mAh g -1 High theoretical specific capacity of, however, Na 2 FePO 4 F has low electronic conductivity and poor rate performance, and limits the exertion of the electrochemical performance.
The prior art generally improves the telephone performance of the fluorophosphate-type cathode material by carbon coating, element doping and reducing the particle size of the material. The carbon coating can improve the surface conductivity of the particles and inhibit the growth of grains, and is a mature modification technology applied at present. There are reports that the electron and ion conductivity of fluorophosphate-type positive electrode materials are improved by doping Ni or Mn, but the cycle stability is reduced although the discharge specific capacity is improved after doping. However, it is difficult to obtain a carbon-coated layer with a uniform surface, and the coated amorphous carbon does not significantly improve the electronic conductivity of the material, and cannot exert the theoretical high capacity of the cathode material. Doping tends to result in reduced structural stability or affect the energy density of the material. And the nano-crystallization of the material can cause the primary particles to easily agglomerate. Therefore, the modification method has various characteristics, and various factors need to be comprehensively considered to obtain the fluorophosphate type sodium ion cathode material which can meet the practical application.
Disclosure of Invention
In order to overcome the defects that the electrochemical performance of a polyanion type sodium ion positive electrode material of iron-based fluorophosphate in the prior art needs to be further improved, and particularly the electron conductivity and the sodium ion diffusion coefficient are not high, the invention provides an improved iron-based fluorophosphate sodium ion positive electrode material and a preparation method thereof. According to the invention, the iron-based phosphate is subjected to binary doping to obtain the sodium ion anode material with excellent electrochemical performance, and the cycling stability of the sodium ion battery anode material is obviously improved by carbon coating, particularly by taking polysaccharide and imidazoline surfactant as carbon sources. The binary doped iron-based fluorophosphate sodium ion cathode material prepared by the method has excellent comprehensive performance, cheap and easily available raw materials and rich sources, and is a novel sodium ion battery cathode material with great application potential.
The purpose of the invention is realized by the following technical scheme:
the first purpose of the invention is to provide a binary doped iron-based fluorophosphate sodium ion anode material expressed as Na 2 Fe 1-x-y M x N y PO 4 F @ C of Na 2 Fe 1-x-y M x N y PO 4 F is obtained after surface carbon coating, wherein M is Mn, and x is more than or equal to 0.02 and less than or equal to 0.10; n is selected from at least one of Ni, Co, Cu, Zn and Ti, y is more than or equal to 0.005 and less than or equal to 0.05, and @ C represents carbon coating.
Furthermore, x is more than or equal to 0.03 and less than or equal to 0.07; n is Co, and y is more than or equal to 0.01 and less than or equal to 0.03.
Further, the particle size of the sodium ion cathode material is 200-1000nm, preferably 500-800nm, the thickness of the carbon coating layer is 1-10nm, preferably 4-7nm, and the carbon coating layer accounts for 5-10 wt% of the sodium ion cathode material.
The invention is to Na 2 PO 4 The F is subjected to binary doping of Mn and transition metal N (particularly Co), and the electron conductivity and the sodium ion diffusion performance of the sodium ion anode material can be remarkably improved by regulating and controlling the doping proportion, so that the high-rate performance of the sodium ion battery is facilitated. Meanwhile, the reversible specific capacity of the sodium ion anode material obtained by the invention at 0.1 ℃ is as high as 100 mAh.g -1 Above that, the reversible specific capacity under 5C high rate is also 80mAh g -1 The above, and the cycle stability is good. Is a sodium ion battery anode material with great potential of practical industrial application.
The second purpose of the invention is to provide a preparation method of the binary doped iron-based fluorophosphate sodium ion cathode material, which comprises the following steps:
(S1) adding a sodium source, a fluorine source, an iron source, a phosphorus source, a manganese source, a transition metal N source and a reducing agent into a dispersing agent, adjusting the pH to 9-11, reacting the mixed solution in a hydrothermal reaction kettle, cooling, washing and drying to obtain Na 2 Fe 1-x-y M x N y PO 4 F, material;
(S2) carbon-coating the material obtained in the step (S1).
Step (S1) adjusting the pH to 9-11, if the alkalinity is too strong, e.g., pH > 11, Fe 2+ Is easily oxidized into F e3+ If the basicity is too weak, Fe is unfavorable 2+ Hydrolysis of (3).
Further, in the step (S1), the sodium source is NaOH or Na 2 CO 3 NaF, wherein the fluorine element is NaF, the iron source is at least one of ferrous sulfate, ferrous chloride, ferrous nitrate and hydrates thereof, the manganese source is at least one of manganese chloride and manganese nitrate, and the transition metal N source is a salt of a divalent transition metal, such as a halogen salt and a nitrate; the phosphorus source is at least one of phosphoric acid, ammonium dihydrogen phosphate and ammonium monohydrogen phosphate.
Further, in the step (S1), the charge ratio of the sodium source, the fluorine source, the iron source, the phosphorus source, the manganese source, the transition metal N source, and the reducing agent satisfies Na: f: fe: p: mn: element N satisfies Na 2 Fe 1-x-y M x N y PO 4 Equivalent ratio of F @ C. The ratio of each element of the polyanionic phosphate obtained by the invention is calculated according to the equivalent of the charging ratio, and although the ratio is different from the actual measurement, the difference is not great.
Further, the hydrothermal reaction condition in the step (S1) is temperature programming, first preheating at 80-100 ℃ for 1-2h, then heating at 0.5-2 ℃/min to 120-130 ℃, reacting at the temperature for 2-4h, then heating at 3-5 ℃/min to 150-180 ℃, and reacting at the temperature for 6-10 h. According to the temperature programming process, the obtained positive electrode material structural framework has a multidimensional sodium ion channel, the structural framework has small obstruction to sodium ion diffusion, the sodium ion can migrate towards multiple directions, the size of the ion channel is large, the path is straight, the positive electrode material structural framework is more suitable for smooth diffusion of the sodium ion in the channel, the sodium ion diffusion potential barrier is reduced, and the diffusion coefficient of the sodium ion is improved.
At the initial stage of the solvothermal reaction, preheating at 80-100 ℃, and slowly heating to 120-130 ℃ to facilitate adjustment of the obtained Na 2 Fe 1-x-y M x N y PO 4 The crystal structure of the F material ensures that the frame structure of the material is stable, and then the temperature is quickly raised to 150-. The finally obtained material particles have good dispersibility and primary particle size D90 at 200-1000nm, preferably at 500-800 nm.
Further, in the step (S1), the dispersant is water and ethylene glycol in a mass ratio of 1: 2-5.
Further, the antioxidant in the step (S1) is not particularly limited, and is for preventing Fe 2+ Oxidation, which is a common water-soluble antioxidant in the art, such as ascorbic acid, vitamin C, and the like. The antioxidant is added in an amount of 0.05 to 0.1 equivalent to the Fe source (in terms of Fe).
Further, the carbon coating in the step (S2) is a gas phase deposition carbon coating or a dipping calcination carbon coating, preferably a dipping calcination carbon coating process, and specifically, the material obtained in the step (S1) and a carbon source are uniformly mixed in a dispersing agent, and are calcined for 6-10h at 600-800 ℃ under the protection of an inert atmosphere after being dried, so as to obtain the carbon-coated material.
The carbon source is polysaccharide and imidazoline type surfactant according to a mass ratio of 100: 5-10, the polysaccharide is selected from at least one of glucose and sucrose, and the imidazoline surfactant is long-chain alkyl imidazoline, such as at least one of undecyl carboxymethyl hydroxyethyl imidazoline, undecyl carboxyethyl hydroxyethyl imidazoline, dodecyl carboxymethyl hydroxyethyl imidazoline, tetradecyl carboxymethyl hydroxyethyl imidazoline and hexadecyl carboxymethyl hydroxyethyl imidazoline.
In the prior art, a surfactant is adopted for preparing a lithium ion or sodium ion battery positive electrode material, but the surfactant and other raw materials are added together in a hydrothermal method and a sol-gel method, and micelles formed by the surfactant in a disperse phase are used as a template agent to obtain porous or hollow microspheres. Unlike these patents, the surfactant is added with the carbon source after the formation of the positive electrode material particles and during the carbon coating.
In the invention, the polysaccharide is used as a carbon source, and has rich sources and low price. On one hand, the imidazoline surfactant enables the polysaccharide to be more uniformly attached to the surface of the positive electrode material particles, and a more uniform and compact carbon coating layer is formed in the subsequent calcining process; on the other hand, it also serves as a supplement to the carbon source itself. Although the reason is unknown, when the carbon coating is carried out, the addition of other surfactants, such as SDS, dodecyltrimethylammonium bromide, oleic acid and the like, cannot significantly improve the cycle stability of the sodium ion battery, and the replacement of the carbon source with other carbon sources, such as citric acid, phenolic resin and the like, cannot achieve the effect of using the polysaccharide and the imidazoline type surfactant, which indicates that the polysaccharide is used as the carbon source and plays a certain role in synergistic compounding with the imidazoline type surfactant.
And (4) during carbon coating, the dispersant is at least one of ethanol, glycol and propanol, and the dosage of the dispersant is 2-3 times of the total mass of the material and the carbon source obtained in the step (S1).
The amount of carbon source used was Na obtained in step (S1) 2 Fe 1-x-y M x N y PO 4 And 30-40 wt% of F material. The addition amount of the carbon source is large, so that the volume expansion can be more effectively inhibited, and the electronic conductivity of the material is also improved to a certain extent, but the carbon does not belong to an active substance in the electrode material, and the mass energy density of the battery is lowered due to the fact that the carbon coating layer is too thick or the mass content of the carbon coating layer is too large. Therefore, the amount of the carbon source used in the present invention is preferably controlled to 30 to 40 wt% of the material obtained in step (S1), and a carbon-coated positive electrode material for sodium ion batteries having excellent overall performance can be obtained in this range.
The invention achieves the following beneficial effects:
the binary doping polyanionic sodium-ion battery anode material is prepared by the invention, the doping elements are metal manganese and another transition metal, and the binary doping ensures that the reversible specific capacity of the prepared anode material is obviously improved, particularly the reversible specific capacity under high multiplying power, and is beneficial to developing the industrialization of sodium-ion batteries.
Secondly, the anode material is coated with carbon, and the uniform and compact carbon coating layer can be obtained by taking the polysaccharide and the imidazoline surfactant as the compounded carbon source, so that the circulation stability is obviously improved.
Drawings
FIG. 1 is an electron micrograph of a positive electrode material of production example 1 of the present invention;
FIG. 2 is an electron micrograph of a positive electrode material of production example 9 of the present invention;
fig. 3 is an electron micrograph of the positive electrode material of production example 11 of the present invention.
Secondly, the anode material is coated with carbon, and the uniform and compact carbon coating layer can be obtained by taking the polysaccharide and the imidazoline surfactant as the compounded carbon source, so that the circulation stability is obviously improved.
FIG. 1 is an electron micrograph of a positive electrode material of production example 1 of the present invention;
FIG. 2 is an electron micrograph of a positive electrode material of production example 9 of the present invention;
fig. 3 is an electron micrograph of the positive electrode material of production example 11 of the present invention.
Detailed Description
The present application is further illustrated by the following examples.
The quality of the carbon coating layer in the positive electrode material of the sodium-ion battery is obtained by testing through a thermal weight loss (TGA) method.
Preparation example 1
(S1) in a molar ratio of 1: 0.93: 1: 1: 0.05: 0.02: 0.1 adding NaOH, NaF and FeSO 4 ·7H 2 O、H 3 PO 4 、 Mn(NO 3 ) 2 、Co(NO 3 ) 2 And ascorbic acid, adding a dispersing agent 12 times of the raw materials by mass, wherein the dispersing agent is a mixed solvent of deionized water and ethylene glycol according to a mass ratio of 1:3, adjusting the pH value to 10, uniformly stirring, transferring the mixture into a polytetrafluoroethylene lining hydrothermal reaction kettle, preheating for 1h at 80 ℃, heating to 120 ℃ at a speed of 1 ℃/min, carrying out heat preservation reaction for 3h, heating to 170 ℃ at a speed of 4 ℃/min, carrying out heat preservation reaction for 8h, cooling, washing for 3 times with deionized water and ethanol respectively, filtering, and carrying out vacuum drying for 15h at 0.01Mpa and 90 ℃ to obtain Na 2 Fe 0.93 Mn 0.05 Co 0.02 PO 4 F。
(S2) adding Na obtained in the step (S1) 2 Fe 0.93 Mn 0.05 Co 0.02 PO 4 F and a carbon source are added into the dispersant ethanol, wherein the carbon source is glucose and undecyl carboxymethyl hydroxyethyl imidazoline according to the mass ratio of 100: 8, the dosage of the carbon source is Na 2 Fe 0.93 Mn 0.05 Co 0.02 PO 4 34 wt% of F, the amount of dispersant ethanol is Na 2 Fe 0.93 Mn 0.05 Co 0.02 PO 4 2.2 times of the F material and the carbon source, performing ultrasonic oscillation for 1 hour, fully and uniformly mixing, drying at 110 ℃ under 0.01MPa, grinding, then putting into a muffle furnace, calcining at 700 ℃ for 6 hours under the argon atmosphere, and finally obtaining the carbon-coated Na 2 Fe 0.93 Mn 0.05 Co 0.02 PO 4 F, expressed as Na 2 Fe 0.93 Mn 0.05 Co 0.02 PO 4 F @ C, @ C denotes carbon coating. After testing, the obtained Na 2 Fe 0.93 Mn 0.05 Co 0.02 PO 4 The particle size D90 of F @ C is about 570nm, the thickness of the carbon coating layer is 6nm, and the mass of the carbon coating layer is 7.3 wt%.
Preparation example 2
(S1) in a molar ratio of 1: 0.94: 1: 1: 0.03: 0.03: 0.1 addition of NaOH, FeSO 4 ·7H 2 O、NaF、H 3 PO 4 、 Mn(NO 3 ) 2 、Co(NO 3 ) 2 And ascorbic acid, adding a dispersing agent 12 times of the raw materials by mass, wherein the dispersing agent is a mixed solvent of deionized water and ethylene glycol according to a mass ratio of 1:5, adjusting the pH value to 10, uniformly stirring, transferring the mixture into a polytetrafluoroethylene lining hydrothermal reaction kettle, preheating for 1h at 90 ℃, heating to 120 ℃ at a speed of 0.5 ℃/min, carrying out heat preservation reaction for 3h, heating to 160 ℃ at a speed of 3 ℃/min, carrying out heat preservation reaction for 10h, cooling, washing for 3 times with deionized water and ethanol respectively, filtering, and carrying out vacuum drying for 15h at 0.01Mpa and 90 ℃ to obtain Na 2 Fe 0.94 Mn 0.03 Co 0.03 PO 4 F。
(S2) adding Na obtained in the step (S1) 2 FeMn 0.05 Co 0.02 PO 4 F and a carbon source are added into a dispersant ethylene glycol, wherein the carbon source is sucrose and undecyl carboxyethyl hydroxyethyl imidazoline according to a mass ratio of 100: 5, the dosage of the carbon source is Na 2 Fe 0.94 Mn 0.03 Co 0.03 PO 4 30 wt% of F, the amount of the dispersant being Na 2 Fe 0.94 Mn 0.03 Co 0.03 PO 4 2.2 times of the F material and the carbon source, and ultrasonically oscillating for 1h, and fillingMixing, oven drying at 110 deg.C under 0.01MPa, grinding, loading into muffle furnace, calcining at 700 deg.C for 6 hr under argon atmosphere to obtain carbon-coated Na 2 Fe 0.94 Mn 0.03 Co 0.03 PO 4 F, expressed as Na 2 Fe 0.94 Mn 0.03 Co 0.03 PO 4 F, @ C denotes carbon coating. After testing, the obtained Na 2 Fe 0.94 Mn 0.03 Co 0.03 PO 4 The particle size D90 of F @ C is about 680nm, the thickness of the carbon coating layer is 5nm, and the mass of the carbon coating layer is 6.8 wt%.
Preparation example 3
(S1) in a molar ratio of 1: 0.92: 1: 1: 0.07: 0.01: 0.1 addition of NaOH, FeSO 4 ·7H 2 O、NaF、H 3 PO 4 、 Mn(NO 3 ) 2 、Co(NO 3 ) 2 And ascorbic acid, adding a dispersing agent 12 times of the raw materials by mass, wherein the dispersing agent is a mixed solvent of deionized water and ethylene glycol according to the mass ratio of 1:3, adjusting the pH value to 10, uniformly stirring, transferring the mixture into a polytetrafluoroethylene lining hydrothermal reaction kettle, preheating for 1h at 90 ℃, heating to 120 ℃ at the speed of 2 ℃/min, carrying out heat preservation reaction for 3h, heating to 180 ℃ at the speed of 3 ℃/min, carrying out heat preservation reaction for 6h, cooling, washing for 3 times with deionized water and ethanol respectively, filtering, and carrying out vacuum drying for 15h at the temperature of 0.01Mpa and 90 ℃ to obtain Na 2 Fe 0.92 Mn 0.07 Co 0.01 PO 4 F。
(S2) adding Na obtained in the step (S1) 2 Fe 0.92 Mn 0.07 Co 0.01 PO 4 F and a carbon source are added into dispersant ethanol, the carbon source is a compound of glucose and undecyl carboxymethyl hydroxyethyl imidazoline according to a mass ratio of 100:10, and the dosage of the carbon source is Na 2 Fe 0.92 Mn 0.07 Co 0.01 PO 4 40 wt% of F, the amount of dispersant being Na 2 Fe 0.92 Mn 0.07 Co 0.01 2.2 times of the material and the carbon source, ultrasonically oscillating for 1h, fully and uniformly mixing, drying at the temperature of 110 ℃ under the pressure of 0.01MPa, grinding, then loading into a muffle furnace, calcining at the temperature of 700 ℃ for 6h under the argon atmosphere, and finally obtaining the carbon-coated Na 2 Fe 0.92 Mn 0.07 Co 0.01 PO 4 F, expressed as Na 2 Fe 0.92 Mn 0.07 Co 0.01 PO 4 F @ C, @ C denotes carbon coating. After testing, the obtained Na 2 Fe 0.92 Mn 0.07 Co 0.01 PO 4 The particle size D90 of F @ C is about 700nm, the thickness of the carbon coating layer is 8nm, and the mass of the carbon coating layer is 8.1 wt%.
Preparation example 4
The other conditions and operations were the same as in preparation example 1 except that the reaction mixture was stirred in a molar ratio of 1: 0.9: 1: 1: 0.05: 0.05: 0.1 addition of NaOH, FeSO 4 ·7H 2 O、NaF、H 3 PO 4 、Mn(NO 3 ) 2 、Co(NO 3 ) 2 And ascorbic acid to finally obtain Na 2 Fe 0.9 Mn 0.05 Co 0.05 PO 4 F@C。
Preparation example 5
The other conditions and operations were the same as in preparation example 1 except that the reaction mixture was changed in a molar ratio of 1: 0.9: 1: 1: 0.08: 0.02: 0.1 addition of NaOH, FeSO 4 ·7H 2 O、NaF、H 3 PO 4 、Mn(NO 3 ) 2 、Co(NO 3 ) 2 And ascorbic acid to finally obtain Na 2 Fe 0.9 Mn 0.08 Co 0.02 PO 4 F@C。
Preparation example 6
The other conditions and operations were the same as in preparation example 1 except that Co (NO) 3 ) 2 Replacement with an equimolar amount of Cu (NO) 3 ) 2 To finally obtain Na 2 Fe 0.93 Mn 0.05 Cu 0.02 PO 4 F@C。
Preparation example 7
The other conditions and operations were the same as in preparation example 1 except that Co (NO) 3 ) 2 Replacement with an equimolar amount of Ni (NO) 3 ) 2 To finally obtain Na 2 Fe 0.93 Mn 0.05 Ni 0.02 PO 4 F@C。
Preparation example 8
The other conditions and operations were the same as in preparation example 1 except that Co (NO) 3 ) 2 By replacing with an equimolar amount of Zn (NO) 3 ) 2 To finally obtain Na 2 Fe 0.93 Mn 0.05 Zn 0.02 PO 4 F@C。
Preparation example 9
The other conditions and operations were the same as in preparation example 1 except that in step (S2), the carbon source was glucose and undecylcarboxymethylhydroxyethyl imidazoline in a mass ratio of 100: 2, compounding.
Preparation example 10
The other conditions and operations were the same as in preparation example 1 except that in step (S2), the carbon source was glucose and undecylcarboxymethylhydroxyethyl imidazoline in a mass ratio of 100: 15 is prepared.
Preparation example 11
The other conditions and operations were the same as in preparation example 1 except that in step (S2), the carbon source was glucose, that is, undecylcarboxymethylhydroxyethyl imidazoline was not added.
Fig. 1 is an electron micrograph of the positive electrode material obtained in production example, fig. 2 is an electron micrograph of the positive electrode material obtained in production example 9, and fig. 3 is an electron micrograph of the positive electrode material obtained in production example 11. It can be seen that in preparation example 1, glucose and undecyl carboxymethyl hydroxyethyl imidazoline are used as the carbon source together, and the thickness of the obtained carbon coating layer is uniform; the carbon coating thickness of the cathode material obtained in preparation example 9 was not uniform, while in preparation example 11, the carbon coating thickness was not uniform and significant bare occurred without the addition of undecylcarboxymethyl hydroxyethyl imidazoline surfactant. The invention adopts the compounding of polysaccharide and imidazoline surfactant in a certain proportion as a carbon source, and can realize good carbon coating on the sodium ion battery.
Preparation example 12
The other conditions and operations were the same as in preparation example 1 except that in step (S1), after preheating at 80 ℃ for 1 hour, the temperature was raised to 170 ℃ at a temperature raising rate of 4 ℃/min, and the reaction was maintained for 12 hours.
Comparative example 1
The other conditions and operations were the same as in preparation example 1, except that in step (S1), the feed was prepared in the molar ratio of 1: 0.95: 1: 1: 0.05: 0.1 addition of NaOH, FeSO 4 ·7H 2 O、NaF、H 3 PO 4 、Mn(NO 3 ) 2 And ascorbic acid, i.e. without Co doping. Finally obtaining the positive electrode material Na of the sodium-ion battery 2 Fe 0.95 Mn 0.05 PO 4 F@C。
Comparative example 2
The other conditions and operations were the same as in preparation example 1 except that in step (S1), the material charge was changed in a molar ratio of 1: 0.98: 1: 1: 0.02: 0.1 addition of NaOH, FeSO 4 ·7H 2 O、NaF、H 3 PO 4 、Co(NO 3 ) 2 And ascorbic acid, i.e. without Mn doping. Finally obtaining the positive electrode material Na of the sodium-ion battery 2 Fe 0.98 Co 0.02 PO 4 F@C。
Comparative example 3
The positive electrode material was Na obtained in step (S1) of production example 1 2 Fe 0.93 Mn 0.05 Co 0.02 PO 4 F, namely the anode material is not coated by carbon.
Application example
Mixing the positive electrode material powder prepared in the preparation example, a conductive agent super P and PVDF according to the mass ratio of 8:1:1, using NMP as a dispersing agent to prepare slurry, coating the slurry on an aluminum foil, drying in vacuum, and compacting to obtain a positive electrode sheet. Using sodium metal as cathode, commercial polypropylene diaphragm, 1mol/L NaPF 6 (the molar ratio of the solvents EC and DEC is 1: 1) is taken as electrolyte, the positive plate prepared in the above way is taken as a positive electrode, and a 2032 button cell is assembled in a glove box under inert atmosphere. Testing the performance of the battery: the charging and discharging voltage is set to 2.5-4.0V, and the constant current charging and discharging test is carried out by using a battery tester, and the results are shown in the following table 1:
TABLE 1
As can be seen from the data in Table 1, the positive electrode material of the sodium-ion battery prepared by the invention has excellent electrochemical performance, and the reversible specific capacity of the preferred embodiment is 110mAh g under the current density of 0.1C -1 The above; also has 90mAh g at a high rate current density of 5C -1 The above reversible specific capacity; and the circulation stability is good, and the capacity retention rate of more than 90% can be maintained after the operation of 100 circles.
Claims (10)
1. A binary doped iron-based fluorophosphate sodium ion positive electrode material is characterized in that the expression is Na 2 Fe 1-x- y M x N y PO 4 F @ C which is Na 2 Fe 1-x-y M x N y PO 4 F is obtained after surface carbon coating, wherein M is Mn, and x is more than or equal to 0.02 and less than or equal to 0.10; n is selected from at least one of Ni, Co, Cu, Zn and Ti, y is more than or equal to 0.005 and less than or equal to 0.05, and @ C represents carbon coating.
2. The sodium ion positive electrode material according to claim 1, wherein x is 0.03. ltoreq. x.ltoreq.0.07; n is Co, and y is more than or equal to 0.01 and less than or equal to 0.03.
3. The sodium ion cathode material as claimed in claim 1, wherein the particle size of the sodium ion cathode material is 200-1000nm, preferably 500-800nm, the thickness of the carbon coating layer is 1-10nm, preferably 4-7nm, and the carbon coating layer accounts for 5-10 wt% of the sodium ion cathode material.
4. A method for producing a sodium ion positive electrode material according to any one of claims 1 to 3, characterized by comprising the steps of:
(S1) mixing a sodium source, a fluorine source, an iron source, a phosphorus source,Adding a manganese source, a transition metal N source and a reducing agent into a dispersing agent, adjusting the pH value to be alkaline, reacting the mixed solution in a hydrothermal reaction kettle, cooling, washing and drying to obtain Na 2 Fe 1-x-y M x N y PO 4 F, material;
(S2) carbon-coating the material obtained in the step (S1).
5. The method according to claim 4, wherein in the step (S1), the sodium source is NaOH or Na 2 CO 3 The fluorine element is NaF, the iron source is at least one of ferrous sulfate, ferrous chloride, ferrous nitrate and hydrates thereof, the manganese source is at least one of manganese chloride and manganese nitrate, and the transition metal N source is a salt of a divalent transition metal; the phosphorus source is at least one of phosphoric acid, ammonium dihydrogen phosphate and ammonium monohydrogen phosphate.
6. The method as claimed in claim 4, wherein the hydrothermal reaction condition in step (S1) is temperature programming, the preheating is performed at 80-100 ℃ for 1-2h, the heating is performed at 0.5-2 ℃/min to 120-130 ℃, the reaction is performed at the temperature for 2-4h, the heating is performed at 3-5 ℃/min to 150-180 ℃, and the reaction is performed at the temperature for 6-10 h.
7. The production method according to claim 4, wherein the dispersant in the step (S1) is water, ethylene glycol, in a mass ratio of 1: 2-5 of a mixed solvent; the antioxidant is water-soluble antioxidant, and the addition amount of the antioxidant is 0.05-0.1 equivalent of the Fe source (calculated by Fe).
8. The method of claim 4, wherein the carbon coating process of the step (S2) comprises the steps of: and (S1) uniformly mixing the material obtained in the step (S1) and a carbon source in a dispersing agent, drying, and calcining for 6-10h at the temperature of 600-800 ℃ under the protection of an inert atmosphere to obtain the carbon-coated material.
9. The method according to claim 8, wherein the carbon source is a polysaccharide and an imidazoline-type surfactant at a mass ratio of 100: 5-10 compounding; preferably, the polysaccharide is at least one selected from glucose and sucrose, and the imidazoline-type surfactant is at least one of long-chain alkyl imidazoline, preferably undecyl carboxymethyl hydroxyethyl imidazoline, undecyl carboxyethyl hydroxyethyl imidazoline, dodecyl carboxymethyl hydroxyethyl imidazoline, tetradecyl carboxymethyl hydroxyethyl imidazoline, and hexadecyl carboxymethyl hydroxyethyl imidazoline.
10. The method according to claim 8, wherein the amount of the carbon source used is Na obtained in step (S1) 2 Fe 1-x-y M x N y PO 4 And 30-40 wt% of F material.
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| PCT/CN2022/107771 WO2023193372A1 (en) | 2022-04-07 | 2022-07-26 | Binary-doped iron-based fluorophosphate sodium ion positive electrode material and preparation method therefor |
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| CN115566187A (en) * | 2022-11-11 | 2023-01-03 | 上海领钫新能源科技有限公司 | Positive active material for sodium ion battery and preparation method and application thereof |
| CN117012956A (en) * | 2023-09-26 | 2023-11-07 | 深圳华钠新材有限责任公司 | Iron-manganese-cobalt-based sodium-rich anion doped positive electrode material and preparation method thereof |
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| CN117239101A (en) * | 2023-11-10 | 2023-12-15 | 临沂大学 | Nitrogen-doped carbon nanotube-coated polyanion type positive electrode material and preparation method thereof |
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| JP5388162B2 (en) * | 2008-01-22 | 2014-01-15 | 日本カーリット株式会社 | Method for producing corrosion-resistant conductive coating material |
| JP2012204322A (en) * | 2011-03-28 | 2012-10-22 | Gs Yuasa Corp | Method for producing active material for nonaqueous electrolyte secondary battery |
| EP2842186B1 (en) * | 2012-04-24 | 2018-10-17 | National University of Singapore | Electrode material and method of synthesizing |
| CN104795564B (en) * | 2014-09-23 | 2018-02-13 | 中国科学院物理研究所 | A kind of positive electrode of Aqueous solution secondary battery, pole piece, secondary cell and purposes |
| CN106058249A (en) * | 2016-07-21 | 2016-10-26 | 天津大学 | Method for preparing carbon coated nano rodlike sodium ferrous phosphate material by solvent thermal |
| CN107180960B (en) * | 2017-06-08 | 2020-03-20 | 四川理工学院 | Carbon-coated lamellar-structure lithium iron phosphate and preparation method thereof |
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| CN115566187A (en) * | 2022-11-11 | 2023-01-03 | 上海领钫新能源科技有限公司 | Positive active material for sodium ion battery and preparation method and application thereof |
| CN117012956A (en) * | 2023-09-26 | 2023-11-07 | 深圳华钠新材有限责任公司 | Iron-manganese-cobalt-based sodium-rich anion doped positive electrode material and preparation method thereof |
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