Positive electrode material, preparation method thereof, positive electrode sheet and sodium ion battery

Abstract

The application provides a positive electrode material and a preparation method thereof, a positive electrode sheet and a sodium ion battery, and belongs to the technical field of sodium ion batteries. x Fe y Fe(CN) z F 6‑z ·nH2O·mHCl, wherein, and 1.90≤x≤2.20, 0.9≤y≤1.2, 4.20≤z≤5.50, 1.00≤n≤1.75, 0.001≤m≤0.007. The application is beneficial to improving the structural stability of the positive electrode material, and the high-efficiency diffusion channel of sodium ions is optimized, thereby improving the sodium storage capacity and cycle stability. Through the synergistic effect among the ions, the problem of high content of crystal water in the positive electrode material is solved, the structural stability of the positive electrode material and the stability of the electrochemical sodium storage performance are improved, the production cost is reduced, and the application range of the sodium ion battery is expanded.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium ion batteries, in particular to a positive electrode material, a preparation method thereof, a positive electrode sheet and a sodium ion battery. BACKGROUND

[0002] Prussian blue (PB) and its analogues (PBAs) are composed of a three-dimensional framework structure, which can provide a wide channel for the insertion and extraction of sodium ions, and PB and its analogues are an ideal positive electrode material for sodium ion batteries (SIBs). However, there are a large number of water molecules and vacancies in PBAs materials, which greatly reduces the storage sites of sodium ions, and the transition metal ions in the metal-organic framework are prone to be precipitated during the cycle process, resulting in limited sodium storage capacity and poor cycle stability of the PBAs positive electrode material. In recent years, various PBAs modification technologies have been researched, which have significantly improved the electrochemical sodium storage performance.

[0003] Among them, metal element doping is a basic method for adjusting capacity, life, rate performance and production cost, and has been widely used in the preparation of SIB materials. Metal ions are usually doped at M sites or Na sites, and transition metal ions such as Ni 2+ , Co 2+ , Cu 2+ , Mn 2+ , Sn 4+ , etc. partially replace the metals at M sites, and K + is usually doped at Na sites. However, the doping of metal cations cannot reduce the content of crystallization water in PBAs, and the doping of expensive metals will also increase the production cost of SIB products. SUMMARY

[0004] In view of the technical problems in the background art, the present application provides a positive electrode material, a preparation method thereof, a positive electrode sheet and a sodium ion battery, aiming to solve the technical problem that the rate performance and cycle performance of Prussian blue sodium battery material are poor due to too high crystallization water content.

[0005] In a first aspect, the embodiments of the present application provide a positive electrode material, which comprises a Prussian blue material, and the molecular formula of the Prussian blue material is Na x Fe y Fe(CN) z F 6-z ·nH2O·mHCl, wherein 1.90≤x≤2.20, 0.9≤y≤1.2, 4.20≤z≤5.50, 1.00≤n≤1.75, and 0.001≤m≤0.007.

[0006] In the technical scheme of the embodiment of the present application, by controlling the chemical composition of the Prussian blue material, fluorine elements are introduced to replace part of the cyanide ions to reduce the content of crystal water and the crystal water vacancy is occupied by HCl, thereby effectively improving the stability of the positive electrode material and improving the electrochemical performance of the positive electrode material.

[0007] In some embodiments, the diffusion coefficient of sodium ions in the Prussian blue material described above is 3.00*10 -13 cm 2 / s~1.00*10 -10 cm 2 / s.

[0008] In this embodiment, the diffusion coefficient of sodium ions in the Prussian blue material is controlled to be within the above range, which is beneficial to improve the transmission speed of sodium ions, so that sodium ions can be embedded and extracted in the positive electrode material faster, which is beneficial to improve the rate performance and cycle performance of the sodium ion battery using the positive electrode material and other improvements in electrochemical performance.

[0009] In a second aspect, the embodiment of the present application provides a preparation method of a positive electrode material, the preparation method of the positive electrode material comprising: providing a base solution, the base solution comprising sodium ions, iron ions and hydrogen fluoride; mixing the base solution, a sodium ferrocyanide solution, a ferrous salt solution and a sodium salt solution, and performing aging treatment to obtain an aged slurry; performing first solid-liquid separation treatment on the aged slurry to obtain an intermediate product; performing slurry treatment on the intermediate product to obtain a reaction slurry; and performing reaction treatment on the reaction slurry to obtain the positive electrode material.

[0010] In the technical scheme of the embodiment of the present application, in the high-concentration fluorine ion environment of the base solution, the fluorine ions with strong complexing ability form complexes with the added ferrous ions and replace part of the cyanide ions, thereby partially introducing fluorine ions into the Prussian blue material. Aging treatment is beneficial to the full crystallization of the Prussian blue material, and reaction treatment further reduces the crystal water inside the Prussian blue material, which is beneficial to improve the stability of the positive electrode material and improve the electrochemical performance of the positive electrode material in terms of cycle stability and rate performance.

[0011] In some embodiments, the step of obtaining the above-mentioned base solution comprises mixing a first solution and a second solution to obtain the base solution, the first solution comprising sodium fluoride and iron fluoride, and the second solution comprising hydrogen fluoride; the pH value of the base solution is 2.5-3.5; the molar ratio of the solute of the sodium ferrocyanide solution, the solute of the ferrous salt solution, and the solute of the sodium salt solution is 1:(1.2-1.5):(2-3); wherein the concentration of the sodium ferrocyanide solution is 1-2 mol / L; and / or, the concentration of the ferrous salt solution is 1.5-2.5 mol / L, and the ferrous salt solution is selected from any one or more of ferrous chloride solution, ferrous sulfate solution, and ferrous acetate solution; and / or, the ferrous salt solution further comprises a reducing agent and a complexing agent; and / or, the reducing agent is a sulfite and / or hydrazine hydrate; and / or, the concentration of the reducing agent in the ferrous salt solution is 0.1-0.5 mol / L; and / or, the complexing agent is ethylenediaminetetraacetic acid and / or citric acid; and / or, the concentration of the complexing agent in the ferrous salt solution is 0.01-0.2 mol / L; and / or, the concentration of the sodium salt solution is 3-5 mol / L, and the mass fraction of sodium fluoride in the solute of the sodium salt solution is 10-20%, and the remaining sodium salt in the solute of the sodium salt solution is selected from any one or more of sodium chloride, sodium sulfate, sodium acetate, and sodium citrate.

[0012] In this embodiment, the formation step of the base solution and the composition, ratio, and concentration of each solution are controlled within the above-mentioned ranges, which is conducive to optimizing the synthesis conditions of the positive electrode material, thereby improving the overall performance of the positive electrode material; at the same time, controlling the pH value within the above-mentioned range is conducive to improving the effectiveness of fluorine ion doping. In addition, by optimizing the above-mentioned parameters, not only is the uniform doping of fluorine ions promoted, but also the structural integrity of the positive electrode material is improved, thereby improving the overall performance of the positive electrode material.

[0013] In some embodiments, the temperature of the aging treatment is 70-90°C, and the time of the aging treatment is 1-2 h; the molar ratio of sodium fluoride to iron fluoride in the first solution is 1:(0.1-0.2); and / or, the total concentration of fluorine ions in the first solution is 2-4 mol / L; and / or, the concentration of the second solution is 5-8 mol / L.

[0014] Controlling the temperature and time of the aging treatment, and controlling the concentration of the above-mentioned solutions and the molar ratio of the solutes in the above-mentioned solutions within the above-mentioned corresponding ranges, is more conducive to improving the efficiency and effectiveness of fluorine ion doping, thereby being conducive to improving the structural stability of the positive electrode material and improving the electrochemical performance of the positive electrode material.

[0015] In some embodiments, the intermediate product and the acid solution are mixed and slurried to obtain a reaction slurry; the slurry treatment is performed; and / or, the temperature of the reaction treatment is 110-130°C, the time of the reaction treatment is 30-60 min; and / or, the stirring speed of the reaction treatment is 100-300 r / min; and / or, the acid solution is a hydrochloric acid-ethanol solution, the concentration of hydrogen ions in the acid solution is 0.5-1 mol / L; and / or, the mass ratio of the solid to the liquid in the reaction slurry is 1:(3-4).

[0016] The step of controlling the slurry treatment is as described above, which is beneficial to improve the dispersion effect of the slurry; at the same time, the conditions of the controlling and reaction treatment are within the above-mentioned corresponding ranges, which is beneficial to fully utilize the ethanol-hydrogen chloride system to erode the intermediate product and to co-boil and replace the partial crystal water at high temperature, so as to further reduce the content of the crystal water in the positive electrode material and to improve the stability and the electrochemical performance of the positive electrode material.

[0017] In some embodiments, the intermediate product is sequentially subjected to a second washing and a second drying before the slurry treatment, wherein the conductivity of the washing water after the completion of the second washing is ≤150 μS / cm, and the water content in the intermediate product is lower than 0.2%.

[0018] By controlling the conditions of the second washing and the second drying, it is beneficial to reduce the water content of the reaction slurry obtained after the slurry treatment of the intermediate product, so as to be more beneficial to further reduce the content of the internal crystal water in the positive electrode material through the reaction treatment and to improve the stability and the electrochemical performance of the positive electrode material.

[0019] In some embodiments, the product obtained through the reaction treatment is sequentially subjected to a second solid-liquid separation treatment, a first washing, a first drying and a crushing to obtain the positive electrode material; and / or, the first washing is performed using alcohol, and the pH value of the washing liquid after the washing is 5.5 or higher; the first drying is performed under the protection of a protective gas, the mass fraction of ethanol in the material is less than 0.1%, the temperature of the first drying is 110-150°C, and the oxygen content in the environment during the first drying is less than 1000 ppm; and the particle size of the positive electrode material after the crushing is 1-5 μm.

[0020] Controlling the conditions of the first washing and the first drying within the above-mentioned ranges is beneficial to remove the residual acid solution and impurities and to improve the purity of the positive electrode material. At the same time, controlling the oxygen content in the environment during the first drying and performing the first drying under the protection of a protective gas is beneficial to reduce the oxidation and the adsorption of water of the positive electrode material. Controlling the particle size of the positive electrode material after the crushing within the above-mentioned range is beneficial to improve the particle size uniformity and the compaction density of the positive electrode material. Through the synergistic effect of the above-mentioned steps, it is more beneficial to improve the electrochemical performance of the sodium ion battery using the positive electrode material.

[0021] In a third aspect, the embodiments of the present application provide a positive electrode tab, which comprises the positive electrode material or the positive electrode material prepared by the preparation method of the positive electrode material.

[0022] In this embodiment, thanks to the low content of crystal water of the positive electrode material, the positive electrode tab comprising the positive electrode material is prepared by the positive electrode material of the present application, and thus the positive electrode tab has better electrochemical performance such as cycle stability and rate capability.

[0023] In a fourth aspect, the embodiments of the present application provide a sodium ion battery comprising the positive electrode tab, which is the positive electrode tab described above.

[0024] In this embodiment, since the sodium ion battery is prepared by the positive electrode tab of the present application, the sodium ion battery not only has higher cycle performance and rate capability, but also the low content of crystal water of the positive electrode material reduces the risk of hydrolysis of the electrolyte of the sodium ion battery, thereby improving the stability and electrochemical performance of the sodium ion battery.

[0025] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented according to the content of the description, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following will specifically describe the embodiments of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creating any creative labor.

[0027] Figure 1 The preparation process flow chart of the positive electrode material in the embodiment 1 of the present application is shown in the figure.

[0028] Figure 2 The test results of the charge specific capacity and discharge specific capacity of the sodium ion battery using the positive electrode material of the embodiment 1 of the present application are shown in the figure. DETAILED DESCRIPTION

[0029] The embodiments of the technical solutions of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and thus only serve as examples, but cannot limit the protection scope of the present application.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the use of the terms "including," "comprising," or "having" and variations thereof herein is intended to be broad and encompass the terms "consisting of" and "consisting essentially of" and variations thereof. Unless otherwise required by context, singular terms shall include pluralities and vice versa. Unless otherwise required by context, the use herein of the singular is also to be construed as a use of the plural and vice versa.

[0031] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise explicitly and specifically limited.

[0032] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearance of the phrase in various places in the specification is not necessarily all referring to the same embodiment, or to a particular embodiment, or to a particular set of embodiments. It will be explicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0033] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A existing alone, A and B existing together, and B existing alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0034] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two), and similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0035] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the embodiments of the present application.

[0036] In the description of the embodiments of the present application, unless specially stated, the solvent of "bottom liquid", "solution", "slurry" is selected from at least one of deionized water, secondary water, distilled water, pure water, ultrapure water.

[0037] In the description of the embodiments of the present application, "ppm" represents the mass percentage concentration.

[0038] Some specific examples are listed below, it should be noted that the examples described below are exemplary, only for the explanation of the present application, and can not be understood as a limitation of the present application. The specific technology or condition is not noted in the examples, according to the technology or condition described in the literature or according to the product instruction. The reagent or instrument used is not noted by the manufacturer, which is a conventional product that can be obtained by market purchase.

[0039] In a first aspect, the present application provides a positive electrode material, the positive electrode material comprising a Prussian blue material, the Prussian blue material having a molecular formula of Na x Fe y Fe(CN) z F 6-z ·nH2O·mHCl, wherein 1.90≤x≤2.20, 0.9≤y≤1.2, 4.20≤z≤5.50, 1.00≤n≤1.75, 0.001≤m≤0.007.

[0040] Further, 1.90≤x≤2.16, preferably 2.00≤x≤2.16, for example, the value of x can be 2.00, 2.08 or 2.16, etc., or other values within the above range, which are not limited here;

[0041] Further, 0.93≤y≤1.12, for example, the value of y can be 0.93, 0.97, 1.00, 1.02, 1.05 or 1.12, etc., or other values within the above range, which are not limited here;

[0042] Further, 4.21≤z≤5.50, preferably 4.21≤z≤5.38, for example, the value of z can be 4.21, 4.92, 4.96, 4.99, 5.00, 5.06, 5.08 or 5.38, etc., or other values within the above range, which are not limited here;

[0043] Further, 1.00≤n≤1.74, preferably 1.10≤n≤1.74, for example, the value of n can be 1.10, 1.12, 1.13, 1.19, 1.24, 1.38, 1.44, 1.48, 1.55, 1.58 or 1.74, etc., or other values within the above range, which are not limited here;

[0044] Further, when 0.001≤m≤0.007, the value of m can be 0.001, 0.002, 0.003, 0.004 or 0.007, or other values within the above range, which are not limited herein;

[0045] Further, the molecular formula of the Prussian blue material can be Na 2.00 Fe 1.00 Fe(CN) 4.99 F 1.01 ·1.12H2O·0.003HCl, Na 2.00 Fe 1.05 Fe(CN) 4.92 F 1.08 ·1.10H2O·0.003HCl, Na 2.00 Fe 1.12 Fe(CN) 4.21 F 1.79 ·1.48H2O·0.004HCl, Na 2.00 Fe 1.00 Fe(CN) 5.00 F 1.00 ·1.13H2O·0.003HCl, Na 2.00 Fe 1.00 Fe(CN) 5.06 F 0.94 ·1.38H2O·0.003HCl, Na 2.08 Fe 0.97 Fe(CN) 4.96 F 1.04 ·1.44H2O·0.004HCl, Na 2.16 Fe 0.93 Fe(CN) 5.08 F 0.92 ·1.58H2O·0.007HCl, Na 2.00 Fe 1.02 Fe(CN) 4.99 F 1.01 ·1.19H2O·0.003HCl, Na 2.16 Fe 1.12 Fe(CN) 5.38 F 1.01 ·1.55H2O·0.004HCl, Na 2.00 Fe 1.00 Fe(CN) 4.99 F 1.01 ·1.24H2O·0.002HCl, or Na 2.00 Fe 1.00 Fe(CN) 4.99 F 1.01• 1.74H2O·0.001HCl, or other molecular formulae conforming to the above-mentioned general formula of Prussian blue material, which are not limited herein.

[0046] In the technical solution of the embodiments of the present application, by controlling the chemical composition of the Prussian blue material, introducing fluorine element to replace part of the cyanide ions, reducing the content of crystal water, and using HCl to occupy the crystal water vacancy, the stability of the positive electrode material is effectively improved, and the electrochemical performance of the positive electrode material is improved.

[0047] Specifically, the fluorine ion has high electronegativity and small ionic radius, can effectively replace part of the cyanide ions, form a stable complex structure, not only increase the electrical conductivity of the positive electrode material, but also reduce the content of crystal water, reduce the damage to the structure of the positive electrode material caused by the deintercalation of water molecules in the cycle process, thereby improving the structural stability of the positive electrode material; at the same time, due to the doping of fluorine ions, the deintercalation channel of sodium ions in the positive electrode material is optimized, thereby improving the deintercalation speed of sodium ions and improving the electrochemical performance of the positive electrode material in terms of rate performance and cycle performance. The HCl in the Prussian blue material occupies the vacancy of the crystal water, reduces the content of the crystal water, avoids the structural damage of the positive electrode material caused by the crystal water, and effectively improves the stability of the positive electrode material.

[0048] In some embodiments of the present application, the diffusion coefficient of sodium ions in the above-mentioned Prussian blue material is 3.00×10 - 13 cm 2 / s~1.00×10 -10 cm 2 / s.

[0049] The diffusion coefficient of sodium ions in the Prussian blue material is 1.00×10 -13 cm 2 / s~1.00×10 -10 cm 2 / s, preferably 3.74×10 -13 cm 2 / s~8.97×10 -11 cm 2 / s, for example, can be 8.97×10 -11 cm 2 / s, 5.67×10 -11 cm 2 / s, 4.89×10 -13 cm 2 / s, 7.69×10 -11 cm 2 / s, 7.57×10 -13 cm 2 / s, 1.32×10-11 cm 2 / s, 8.65 x 10 -13 cm 2 / s, 8.12 x 10 -11 cm 2 / s, 3.74 x 10 -13 cm 2 / s, 4.72 x 10 -11 cm 2 / s or 9.23 x 10 -13 cm 2 / s, etc., and other values within the above ranges are also possible and are not limited herein.

[0050] Controlling the diffusion coefficient of sodium ions in the Prussian blue material within the above range is conducive to improving the transmission speed of sodium ions, so that sodium ions can be embedded and extracted in the positive electrode material faster, which is conducive to improving the rate performance and cycle performance of sodium ion batteries using the positive electrode material and other improvements in electrochemical performance.

[0051] In some embodiments, the loose bulk density of the positive electrode material is 0.58 g / mL to 0.78 g / mL, for example, the loose bulk density can be 0.58 g / mL, 0.60 g / mL, 0.61 g / mL, 0.63 g / mL, 0.64 g / mL, 0.66 g / mL, 0.69 g / mL, or 0.78 g / mL, etc., and other values within the above ranges are also possible and are not limited herein.

[0052] In some embodiments, the tap density of the positive electrode material is 1.15 g / mL to 1.39 g / mL, for example, the tap density can be 1.15 g / mL, 1.16 g / mL, 1.18 g / mL, 1.20 g / mL, 1.21 g / mL, 1.23 g / mL, 1.29 g / mL, 1.31 g / mL, or 1.39 g / mL, etc., and other values within the above ranges are also possible and are not limited herein.

[0053] In some embodiments, the compacted density of the positive electrode material is 1.78 g / mL to 2.09 g / mL, for example, the compacted density can be 1.78 g / mL, 1.87 g / mL, 1.91 g / mL, 1.93 g / mL, 1.94 g / mL, 1.97 g / mL, 1.98 g / mL, 2.04 g / mL, or 2.09 g / mL, etc., and other values within the above ranges are also possible and are not limited herein.

[0054] Controlling the loose bulk density, tap density, and compacted density of the positive electrode material within the above respective ranges is conducive to obtaining a positive electrode material with improved energy density, thereby improving the charge specific capacity, discharge specific capacity, and other electrochemical performance of the positive electrode material.

[0055] In some embodiments, the D10 particle size of the positive electrode material is 0.3-0.8 μm, for example, the D10 particle size can be 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm or 0.8 μm, etc., or other values within the above range, which are not limited herein.

[0056] In some embodiments, the D50 particle size of the positive electrode material is 2.3-3.1 μm, for example, the D50 particle size can be 2.3 μm, 2.4 μm, 2.5 μm, 2.7 μm, 2.8 μm, 2.9 μm or 3.1 μm, etc., or other values within the above range, which are not limited herein.

[0057] In some embodiments, the D10 particle size and the D50 particle size of the positive electrode material are tested by a laser particle size analyzer, the D10 particle size represents the particle size corresponding to the cumulative volume distribution percentage of 10% of the positive electrode material, and the D50 particle size represents the particle size corresponding to the cumulative volume distribution percentage of 50% of the positive electrode material.

[0058] Controlling the D10 particle size and the D50 particle size of the positive electrode material within the above corresponding ranges is beneficial to obtain the positive electrode material with concentrated particle size distribution, thereby improving the consistency of the positive electrode material in the charging-discharging process and improving the electrochemical performance of the positive electrode material.

[0059] In some embodiments, the iron elution amount of the positive electrode material is 6.4-59.2 ppm, for example, the iron elution amount can be 6.4 ppm, 6.7 ppm, 10.3 ppm, 11.2 ppm, 11.3 ppm, 12.1 ppm, 12.5 ppm, 13.8 ppm, 15.3 ppm or 59.2 ppm, etc., or other values within the above range, which are not limited herein.

[0060] In some embodiments, the magnetic substance amount of the positive electrode material is 0.11-0.14 ppm, for example, the magnetic substance amount can be 0.11 ppm, 0.12 ppm or 0.14 ppm, etc., or other values within the above range, which are not limited herein.

[0061] In some embodiments, the free water content of the positive electrode material is 103-399 ppm, for example, the free water content can be 103 ppm, 109 ppm, 137 ppm, 168 ppm, 178 ppm, 189 ppm, 198 ppm, 212 ppm, 256 ppm or 399 ppm, etc., or other values within the above range, which are not limited herein.

[0062] The iron leaching amount, the magnetic substance amount and the free water content of the positive electrode material are respectively controlled within the above corresponding ranges, which is beneficial to improving the product quality of the positive electrode material and improving the effect of the positive electrode material when applied in the sodium ion battery.

[0063] In a second aspect, the application provides a preparation method of a positive electrode material, which comprises: providing a base solution, the base solution comprising sodium ions, iron ions and hydrogen fluoride; mixing the base solution, a sodium ferrocyanide solution, a ferrous salt solution and a sodium salt solution, and obtaining an aging slurry through an aging treatment; obtaining an intermediate product through a first solid-liquid separation treatment of the aging slurry; obtaining a reaction slurry through a slurry treatment of the intermediate product; and obtaining the positive electrode material through a reaction treatment of the reaction slurry.

[0064] In the technical scheme of the embodiments of the application, in the high-concentration fluoride ion environment of the base solution, the fluoride ions with strong complexing ability form complexes with the added ferrous ions and replace part of the cyanide ions, so that the fluoride ions are partially introduced into the Prussian blue material. The aging treatment is beneficial to the full crystallization of the Prussian blue material, and the reaction treatment further reduces the crystal water in the Prussian blue material, which is beneficial to improving the stability of the positive electrode material and improving the electrochemical performance of the positive electrode material in terms of cycle stability and rate performance.

[0065] In some embodiments of the application, the step of obtaining the above base solution comprises: mixing a first solution and a second solution to obtain the base solution, the first solution comprising sodium fluoride and iron fluoride, and the second solution comprising hydrogen fluoride.

[0066] The addition of iron fluoride provides fluoride ions and fluoride-iron complex ions, which provides a basis for subsequent substitution of fluoride.

[0067] In some embodiments, the pH value of the base solution is 2.5-3.5.

[0068] A pH value that is too low is not conducive to the stability of the material structure, and a pH value that is too high is not conducive to the embedding of fluoride ions. Controlling the pH value within the above range is beneficial to improving the effectiveness of fluoride ion doping.

[0069] In some embodiments, the pH value of the above base solution can be 2.5, 2.6, 2.7, 2.8, 2.9, 3.1, 3.2, 3.3, 3.4 or 3.5, etc., or other values within the above range, which are not limited herein.

[0070] In some embodiments, the molar ratio of the solute of the sodium ferrocyanide solution, the solute of the ferrous salt solution and the solute of the sodium salt solution is 1:(1.2-1.5):(2-3).

[0071] Controlling the above molar ratio is helpful to more accurately control the chemical composition of the final positive electrode material, so that the molecular formula of the positive electrode material is closer to Na xFe y Fe(CN) z F 6-z The optimal ratio of nH2O.mHCI. Such a ratio helps to optimize the structural stability and ion diffusion channels of the positive electrode material, thereby improving the capacity and cycle stability of the positive electrode material.

[0072] In some embodiments, the molar ratio of the solute of the sodium ferrocyanide solution, the solute of the ferrous salt solution, and the solute of the sodium salt solution can be 1:1.2:2, 1:1.3:2, 1:1.4:2, 1:1.5:2, 1:1.2:2.5, 1:1.3:2.5, 1:1.4:2.5, 1:1.5:2.5, 1:1.2:3, 1:1.3:3, 1:1.4:3, or 1:1.5:3, etc., and can also be other values within the above ranges, which are not limited herein.

[0073] In some embodiments, the concentration of the sodium ferrocyanide solution is 1 mol / L-2 mol / L.

[0074] In some embodiments, the concentration of the ferrous salt solution is 1.5 mol / L-2.5 mol / L; the ferrous salt solution is selected from any one or more of ferrous chloride solution, ferrous sulfate solution, and ferrous acetate solution. In some embodiments, the concentration of the sodium ferrocyanide solution can be 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2.0 mol / L, 2.1 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L, or 2.5 mol / L, etc., and can also be other values within the above ranges, which are not limited herein.

[0075] The concentration of the sodium ferrocyanide solution and the concentration of the ferrous salt solution are controlled within the above corresponding ranges based on the consideration of reaction kinetics and chemical equilibrium, so as to facilitate efficient reaction, while reducing the risk of side reactions or material structure damage caused by excessive reactants. The preferred above-mentioned ferrous salt has a wide source and a moderate price, which helps to improve the economy of the entire production process, and at the same time, they have good solubility in solution, which is convenient for control and operation, and is conducive to the stability and cost control of the production process.

[0076] In some embodiments, the ferrous salt solution further includes a reducing agent and a complexing agent.

[0077] Fe 2+is the key to constitute the framework of Prussian blue type materials, keeping its reduced state is essential to form the correct crystal structure, the presence of reducing agent is conducive to ensure that ferrous ions remain in the divalent state during the synthesis process, to avoid oxidation to trivalent iron ions (Fe 3+ ). Complexing agent helps to form a stable complex with ferrous ions, reducing the risk of premature precipitation or oxidation of ferrous ions in solution, thereby improving the uniform dispersion and stable existence of ferrous ions during the reaction process, conducive to the formation of uniform crystal structure.

[0078] In some embodiments, the reducing agent is sulfite and / or hydrazine hydrate.

[0079] Sulfite and / or hydrazine hydrate as a reducing agent helps to facilitate the progress of the synthesis reaction, especially the step involving sodium ferrocyanide solution and the bottom liquid reaction.

[0080] In some embodiments, the concentration of the reducing agent in the ferrous salt solution is 0.1 mol / L to 0.5 mol / L.

[0081] Too high concentration of reducing agent may produce unnecessary side reactions, consume too much resources, while too low concentration may not be able to effectively promote the reduction reaction, affecting the quality of the material and the progress of the reaction, controlling the concentration of reducing agent in the above range helps to balance the efficiency of the reducing agent in the reaction and the use cost problem.

[0082] In some embodiments, the concentration of the reducing agent in the ferrous salt solution can be 0.1 mol / L, 0.15 mol / L, 0.20 mol / L, 0.25 mol / L, 0.30 mol / L, 0.35 mol / L, 0.40 mol / L, 0.45 mol / L or 0.50 mol / L, etc. It can also be other values within the above range, which is not limited here.

[0083] In some embodiments, the complexing agent is ethylenediaminetetraacetic acid (EDTA) and / or citric acid.

[0084] The above kind of complexing agent helps to form a more stable complex with ferrous ions, thereby facilitating the formation of a uniform crystal structure, thereby improving the stability of the structure of the positive electrode material.

[0085] In some embodiments, the concentration of the complexing agent in the ferrous salt solution is 0.01 mol / L to 0.2 mol / L.

[0086] Controlling the concentration of the complexing agent in the above range is more conducive to improving the effectiveness of the complexing reaction and the controllability of the material structure.

[0087] In some embodiments, the concentration of the complexing agent in the ferrous salt solution can be 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.11 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L, 0.15 mol / L, 0.16 mol / L, 0.17 mol / L, 0.18 mol / L, 0.19 mol / L, or 0.2 mol / L, etc., and can also be other values within the above range, which are not limited herein.

[0088] In some embodiments, the concentration of the sodium salt solution is 3-5 mol / L, the mass fraction of sodium fluoride in the solute of the sodium salt solution is 10-20%, and the remaining sodium salt in the solute of the sodium salt solution is selected from any one or more of sodium chloride, sodium sulfate, sodium acetate, and sodium citrate. In some embodiments, the concentration of the sodium salt solution can be 3 mol / L, 3.1 mol / L, 3.2 mol / L, 3.3 mol / L, 3.4 mol / L, 3.5 mol / L, 3.6 mol / L, 3.7 mol / L, 3.8 mol / L, 3.9 mol / L, 4.0 mol / L, 4.1 mol / L, 4.2 mol / L, 4.3 mol / L, 4.4 mol / L, 4.5 mol / L, 4.6 mol / L, 4.7 mol / L, 4.8 mol / L, 4.9 mol / L, or 5 mol / L, etc., and can also be other values within the above range, which are not limited herein.

[0089] By controlling the concentration of the sodium salt solution, the mass fraction of sodium fluoride, and selecting different sodium salts, the synthesis conditions of the positive electrode material can be optimized, the efficient reaction can be promoted, the microstructure of the positive electrode material can be controlled, the electrochemical performance of the positive electrode material can be improved, and the cost and performance can be balanced at the same time.

[0090] In summary, by controlling the formation step of the base solution and the composition, ratio, and concentration of each solution within the above range, the synthesis conditions of the positive electrode material can be optimized, thereby improving the overall performance of the positive electrode material. At the same time, by optimizing the above parameters, not only the uniform doping of fluorine ions is promoted, but also the structural integrity of the positive electrode material is improved, thereby improving the overall performance of the positive electrode material.

[0091] In some embodiments, the steps of mixing the base solution, the sodium ferrocyanide solution, the ferrous salt solution, and the sodium salt solution include:

[0092] The temperature of the sodium ferrocyanide solution, the ferrous salt solution, and the sodium salt solution is maintained respectively;

[0093] The sodium ferrocyanide solution, the ferrous salt solution and the sodium salt solution are added to the bottom solution within a first mixing time.

[0094] In some embodiments, the temperature of the sodium ferrocyanide solution, the ferrous salt solution and the sodium salt solution is maintained at 70-90°C.

[0095] In some embodiments, the temperature of the bottom solution is maintained at 70-90°C before the sodium ferrocyanide solution, the ferrous salt solution and the sodium salt solution are added to the bottom solution.

[0096] In some embodiments, the temperature of the sodium ferrocyanide solution, the ferrous salt solution, the sodium salt solution and / or the bottom solution is maintained at the same temperature as the aging treatment.

[0097] In some embodiments, the sodium ferrocyanide solution, the ferrous salt solution and the sodium salt solution are added to the bottom solution within the first mixing time respectively; or, the sodium ferrocyanide solution, the ferrous salt solution and the sodium salt solution are mixed and then added to the bottom solution within the first mixing time.

[0098] In some embodiments, the first mixing time is 30-60 minutes, for example, it can be 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, etc.

[0099] In some embodiments, the bottom solution, the sodium ferrocyanide solution, the ferrous salt solution and the sodium salt solution are stirred. The stirring speed can be 100-300 r / min.

[0100] In some embodiments of the present application, the temperature of the above-mentioned aging treatment is 70-90°C, the time of the aging treatment is 1-2 hours; the molar ratio of sodium fluoride to ferric fluoride in the first solution is 1:(0.1-0.2).

[0101] The aging treatment in the above temperature range and time range helps to reduce the risk of generating excessive agglomeration or too small particles, thereby facilitating the formation of a uniform and orderly crystal structure, improving the electrical conductivity and ion diffusion efficiency of the positive electrode material, and thus enhancing the sodium storage capacity and cycle stability of the battery. In some embodiments of the present application, the temperature of the above aging treatment can be 70℃, 72℃, 74℃, 75℃, 76℃, 78℃, 80℃, 82℃, 84℃, 85℃, 86℃, 88℃, or 90℃, etc., and can also be other values within the above range, which are not limited herein; the time of the aging treatment can be 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, or 2h, etc., and can also be other values within the above range, which are not limited herein; the amount-of-substance ratio of sodium fluoride to iron fluoride in the first solution can be 1:0.1, 1:0.11, 1:0.12, 1:0.13, 1:0.14, 1:0.15, 1:0.16, 1:0.17, 1:0.18, 1:0.19, or 1:0.2, etc., and can also be other values within the above range, which are not limited herein.

[0102] In some embodiments, the total concentration of fluoride ions in the first solution is 2mol / L-4mol / L.

[0103] By controlling the amount-of-substance ratio of sodium fluoride to iron fluoride in the first solution within the above range, it is beneficial to the uniform doping of fluoride ions in the positive electrode material. In some embodiments, the total concentration of fluoride ions in the first solution can be 2mol / L, 2.1mol / L, 2.2mol / L, 2.3mol / L, 2.4mol / L, 2.5mol / L, 2.6mol / L, 2.7mol / L, 2.8mol / L, 2.9mol / L, 3.0mol / L, 3.1mol / L, 3.2mol / L, 3.3mol / L, 3.4mol / L, 3.5mol / L, 3.6mol / L, 3.7mol / L, 3.8mol / L, 3.9mol / L, or 4mol / L, etc., and can also be other values within the above range, which are not limited herein.

[0104] In some embodiments, the concentration of the second solution is 5mol / L-8mol / L.

[0105] The concentration of the second solution is controlled within the above range, which helps to inhibit side reactions, improve the purity and performance of the positive electrode material, and is conducive to the structural stability of the positive electrode material. In some embodiments, the concentration of the second solution can be 5 mol / L, 5.2 mol / L, 5.4 mol / L, 5.5 mol / L, 5.7 mol / L, 5.8 mol / L, 6.0 mol / L, 6.2 mol / L, 6.4 mol / L, 6.5 mol / L, 6.7 mol / L, 6.8 mol / L, 7.0 mol / L, 7.2 mol / L, 7.4 mol / L, 7.5 mol / L, 7.7 mol / L, 7.8 mol / L, or 8 mol / L, etc., and can also be other values within the above range, which are not limited herein.

[0106] The temperature and time of the aging treatment, the concentration of the above solution, and the amount of substance ratio of the solute in the above solution are controlled within the corresponding ranges, which is more conducive to improving the efficiency and effect of fluorine ion doping, thereby improving the structural stability of the positive electrode material and improving the electrochemical performance of the positive electrode material.

[0107] In some embodiments, the first solid-liquid separation treatment can be performed by normal pressure filtration, pressure filtration, suction filtration, centrifugal separation, etc.

[0108] In some embodiments of the present application, the above intermediate product and the acid solution are mixed and slurried to obtain a reaction slurry.

[0109] The above steps help to reduce the amount of crystal water, optimize the sodium ion diffusion path, improve the purity of the material, improve the dispersibility of the intermediate product, and control the microstructure, which plays a role in improving the performance of the positive electrode material, such as high sodium storage capacity, good cycle stability, and rate performance.

[0110] In some embodiments, the temperature of the reaction treatment is 110°C to 130°C, and the time of the reaction treatment is 30 min to 60 min.

[0111] Controlling the temperature and time of the reaction treatment within the above range helps the crystal water to fully escape in the form of water vapor, while maintaining the integrity and stability of the positive electrode material structure. In some embodiments, the temperature of the reaction treatment can be 110°C, 112°C, 115°C, 117°C, 120°C, 122°C, 125°C, 128°C, or 130°C, etc., and can also be other values within the above range, which are not limited herein; the time of the reaction treatment can be 30 min, 32 min, 35 min, 38 min, 40 min, 42 min, 45 min, 48 min, 50 min, 52 min, 55 min, or 60 min, etc., and can also be other values within the above range, which are not limited herein.

[0112] In some embodiments, the stirring speed of the reaction treatment is 100 r / min to 300 r / min.

[0113] Controlling the above stirring speed helps to promote uniform mixing of the reactants, improve reaction efficiency, control the particle size of the positive electrode material, and reduce the generation of by-products, thereby helping to synthesize a positive electrode material with excellent performance. In some embodiments, the stirring speed of the reaction treatment can be 100 r / min, 120 r / min, 150 r / min, 200 r / min, 250 r / min, or 300 r / min, etc., or other values within the above range, which are not limited herein.

[0114] In some embodiments, the acid solution is a hydrochloric acid-ethanol solution, and the concentration of hydrogen ions in the acid solution is 0.5 mol / L to 1 mol / L.

[0115] The present application utilizes the ethanol-hydrogen chloride system at high temperature to realize the corrosion of the positive electrode material and the azeotropy and replacement of part of the crystal water. Specifically, the reaction treatment of the reaction slurry in the present application utilizes the ethanol-hydrogen chloride system at high temperature to corrode the intermediate product and realize the azeotropy and replacement of part of the crystal water. At high temperature, part of the crystal water and hydrogen chloride form azeotropy, thereby removing the intermediate product, and the vacancy position generated thereby is occupied by hydrogen chloride. This reduces the crystal water content of the Prussian blue material and effectively reduces the collapse of the structure of the Prussian blue material caused by the removal of water.

[0116] Further, hydrogen ions can accelerate the formation of vacancies in the positive electrode material, and these vacancies are subsequently occupied by chloride ions. Controlling the concentration of hydrogen ions within the above range helps to optimize the diffusion channel of sodium ions and improve the diffusion coefficient of sodium ions while removing the crystal water, which helps to form the complex structure unique to the Prussian blue material and improve the rate performance and cycle stability of the positive electrode material. In addition, the presence of ethanol can act as a dispersant, which helps to reduce the excessive aggregation of positive electrode material particles. In some embodiments, the concentration of hydrogen ions in the acid solution can be 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, 0.85 mol / L, 0.9 mol / L, 0.95 mol / L, or 1 mol / L, etc., or other values within the above range, which are not limited herein.

[0117] In some embodiments, the mass ratio of solids to liquids in the reaction slurry is 1:(3-4), i.e., the solid-liquid ratio in the reaction slurry is 1:(3-4).

[0118] The above mass ratio is not only conducive to the removal of the crystallization water in the intermediate product, but also conducive to reducing the agglomeration and improving the electrochemical performance, production efficiency and reducing the cost of the positive electrode material. In some embodiments, the mass ratio of the solid to the liquid in the reaction slurry can be 1:3, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9 or 1:4, etc., and can also be other values within the above range, which is not limited herein.

[0119] In summary, by controlling the slurry treatment within the above corresponding range, the dispersion effect of the slurry is improved. At the same time, by controlling the conditions of the reaction treatment within the above corresponding range, the ethanol-hydrogen chloride system is fully utilized to erode the intermediate product and to azeotrope and replace the partial crystallization water at high temperature, so as to further reduce the content of the crystallization water in the positive electrode material and improve the stability and electrochemical performance of the positive electrode material.

[0120] In some embodiments, the intermediate product is sequentially subjected to the second washing and the second drying before the slurry treatment.

[0121] In some embodiments, the washing liquid of the second washing can be at least one of deionized water, secondary water, distilled water, pure water, ultrapure water. The conductivity of the washing water after the completion of the second washing is less than or equal to 150 μS / cm, i.e., the conductivity of the washing liquid after the completion of the second washing is less than or equal to 150 μS / cm.

[0122] In some embodiments, the water content in the intermediate product after the completion of the second drying is less than 0.2%.

[0123] In some embodiments, the second drying can adopt vacuum drying.

[0124] In some embodiments, the temperature of the second drying can be lower than the temperature of the reaction treatment.

[0125] In some embodiments of the present application, the product obtained by the reaction treatment is sequentially subjected to the second solid-liquid separation treatment, the first washing, the first drying and the crushing to obtain the positive electrode material.

[0126] In some embodiments, the crushed positive electrode material is sequentially subjected to the screening, the iron removal and the packaging to obtain the final positive electrode material.

[0127] Through the screening, the iron removal and the packaging, the quality of the positive electrode material in the particle size, the purity and the storage state is improved, so as to improve the comprehensive performance of the positive electrode material in the sodium ion battery, including improving the cycle stability, the rate performance, the energy density and prolonging the battery life, etc.

[0128] In some embodiments, the second solid-liquid separation treatment can be performed by using normal pressure filtration, pressure filtration, suction filtration, centrifugal separation, etc.

[0129] In some embodiments, the pH value of the washing liquid after the first washing using alcohol is 5.5 or above; the first drying is performed under the protection of a protective gas, the mass fraction of ethanol in the material is less than 0.1%, the temperature of the first drying is 110-150°C, and the oxygen content in the environment during the first drying is less than 1000 ppm; and the particle size of the positive electrode material after crushing is 1-5 μm.

[0130] The alcohol washing is beneficial to effectively removing residual impurities, improving the purity of the positive electrode material, reducing the risk of impurities in the sodium ion battery, and improving the stability and life of the sodium ion battery. Washing to a pH value of 5.5 or above helps to ensure that the positive electrode material can be used in a neutral or nearly neutral environment, which is beneficial to improving the cycle performance and stability of the battery.

[0131] The first drying under the protection of a protective gas is beneficial to effectively reducing the risk of oxidation reaction of the positive electrode material with oxygen in the air, reducing by-products, and maintaining the electrochemical activity of the positive electrode material. By controlling the temperature of the first drying to be 110-150°C, it is helpful to quickly evaporate ethanol and control the mass fraction of ethanol to be less than 0.1% and as much as possible to reduce the content of crystal water in the positive electrode material, improve the structural stability of the positive electrode material, and reduce the negative impact of water precipitation in the battery cycle process on the performance of the sodium ion battery. Controlling the oxygen content in the environment during the first drying to be less than 1000 ppm helps to provide a nearly oxygen-free environment for the first drying, further reducing the possibility of oxidation. In some embodiments, the temperature of the first drying can be 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, or 150°C, etc., or other values within the above range, which are not limited herein; the particle size of the positive electrode material after crushing can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, or 5 μm, etc., or other values within the above range, which are not limited herein.

[0132] Controlling the particle size of the positive electrode material after crushing within the above range is beneficial to improving the particle size uniformity and the compaction density of the positive electrode material. Through the synergistic effect of the above steps, it is more beneficial to improve the electrochemical performance of the sodium ion battery.

[0133] In addition, in some embodiments, the protective gas for the above first drying is nitrogen, the first drying is performed in an oven, and the oxygen content in the environment during the first drying refers to the oxygen content in the oven.

[0134] In a third aspect, the application provides a positive electrode tab, which comprises the positive electrode material or the positive electrode material prepared by the preparation method.

[0135] In this embodiment, thanks to the low crystallization water content of the positive electrode material, the positive electrode tab comprising the positive electrode material is prepared by the positive electrode material of the application, and thus the positive electrode tab has better electrochemical properties such as cycle stability and rate capability.

[0136] In a fourth aspect, the application provides a sodium ion battery comprising the positive electrode tab, which is the positive electrode tab described above.

[0137] In this embodiment, since the sodium ion battery is prepared by the positive electrode tab of the application, the sodium ion battery not only has higher cycle performance and rate capability, but also the low crystallization water content of the positive electrode material reduces the risk of hydrolysis of the electrolyte of the sodium ion battery, thereby improving the stability and electrochemical performance of the sodium ion battery.

[0138] In a fifth aspect, the application provides an electric device comprising the sodium ion battery, which is the sodium ion battery described above. In this embodiment, the electric device contains the sodium ion battery described above, and thus has good stability and electrochemical performance.

[0139] The electric device provided by the embodiments of the application can be, but is not limited to, a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric vehicle, an electric automobile, a ship, a spacecraft, etc. The electric toy can include a fixed or mobile electric toy, such as a game console, an electric automobile toy, an electric ship toy, an electric aircraft toy, etc. The spacecraft can include an airplane, a rocket, a space shuttle, a spacecraft, etc.

[0140] I. Preparation method

[0141] Embodiment 1

[0142] Reference Figure 1 The preparation process flow chart of the positive electrode material shown in FIG. 1 is as follows: sodium fluoride and iron fluoride are mixed to form a first solution, the amount-of-substance ratio of sodium fluoride to iron fluoride is 1:0.15, and the concentration of fluoride ions in the first solution is 3.45 mol / L; the first solution is mixed with a second solution, the second solution is a hydrogen fluoride solution with a concentration of 6.5 mol / L, the pH of the mixed solution is adjusted to 3.1, and a bottom solution is prepared.

[0143] Sodium ferrocyanide, ferrous salt and sodium salt are configured into solution respectively, the concentration of sodium ferrocyanide solution is 1.5mol / L, the concentration of ferrous salt is 2mol / L, the concentration of sodium salt solution is 4mol / L, the temperature of sodium ferrocyanide solution, ferrous salt solution and sodium salt solution is maintained at 80℃, the ferrous salt is ferrous chloride, sodium sulfite is added into the ferrous salt solution, the concentration of sodium sulfite in the ferrous salt solution is 0.3mol / L, the complexing agent is ethylenediaminetetraacetic acid (EDTA), the concentration of EDTA in the ferrous salt solution is 0.08mol / L, the mass ratio of sodium fluoride in the solute of sodium salt solution is 15%, the rest of sodium salt is sodium chloride, the amount-of-substance ratio of solute in sodium ferrocyanide, ferrous chloride and sodium salt solution is 1:1.35:2.5; under the state of stirring, the three solutions are added into the bottom liquid together, the adding time is 45min, the reaction and aging is continued at 80℃ for 1.5h, the reaction slurry is obtained;

[0144] After the reaction slurry is filtered and washed with pure water until the conductivity of washing liquid is ≤150μS / cm (second washing), the washing material obtained is vacuum dried (second drying) until the water content is less than 0.2%, the intermediate product is obtained; the intermediate product is transferred into a sealed reaction kettle, hydrochloric acid-ethanol solution with a hydrogen ion concentration of 0.8mol / L is added for slurry, the reaction slurry is obtained, the solid-liquid ratio of the reaction slurry is 1:3.5; the sealed reaction kettle is then heated to a temperature of 120℃, the pressure is 3.3kg / cm 2 , the reaction slurry is reacted under this condition for 45min, the stirring speed is 180r / min, then after cooling, the material is filtered and washed, alcohol is used as washing liquid, the washing is stopped after the pH value of washing liquid is 5.5 or above, the material after washing is subjected to first drying by nitrogen gas flow, the temperature of first drying is 130℃, the oxygen content in the oven is maintained below 1000ppm during first drying, the drying is stopped after the alcohol content in the material is below 0.1wt%, then the material is crushed until the particle size is 2.7μm, the crushing is stopped, the positive electrode material is obtained, the specific chemical formula is Na 2.00 Fe 1.00 Fe(CN) 4.99 F 1.01 ·1.12H2O·0.003HCl.

[0145] The detection data of the positive electrode material obtained are as follows:

[0146] Table 1

[0147]

[0148] Example 2

[0149] The first solution is prepared by mixing sodium fluoride and iron fluoride, the molar ratio of sodium fluoride to iron fluoride is 1:0.2, and the concentration of fluoride ions in the first solution is 3.45 mol / L; the first solution is mixed with the second solution, the second solution is a hydrogen fluoride solution with a concentration of 6.5 mol / L, the pH of the mixed solution is adjusted to 3.1 to prepare the bottom solution;

[0150] Sodium ferrocyanide, ferrous salt and sodium salt are respectively configured into solutions, the concentration of the sodium ferrocyanide solution is 1.5 mol / L, the concentration of the ferrous salt solution is 2 mol / L, and the concentration of the sodium salt solution is 4 mol / L, the temperature of the sodium ferrocyanide solution, the ferrous salt solution and the sodium salt solution is maintained at 80°C, the ferrous salt is ferrous chloride, sodium sulfite is added to the ferrous salt solution, the concentration of sodium sulfite in the ferrous salt solution is 0.3 mol / L, the complexing agent is ethylenediaminetetraacetic acid (EDTA), the concentration of EDTA in the ferrous salt solution is 0.08 mol / L, the mass fraction of sodium fluoride in the solute of the sodium salt solution is 15%, and the remaining sodium salt is sodium chloride, the molar ratio of the solutes in the sodium ferrocyanide, ferrous chloride and sodium salt solutions is 1:1.35:2.5; under stirring, the three solutions are added to the bottom solution, the adding time is 45 min, and the reaction is continued at 80°C for 1.5 h to obtain a reaction slurry;

[0151] The reaction slurry is filtered and washed with pure water until the conductivity of the washing liquid is ≤150 μS / cm (second washing), the washing material obtained is vacuum dried (second drying) until the water content is less than 0.2%, and an intermediate product is obtained; the intermediate product is transferred into a sealed reaction kettle, a hydrochloric acid-ethanol solution with a hydrogen ion concentration of 0.8 mol / L is added for slurry, and a reaction slurry is obtained, the solid-liquid ratio of the reaction slurry is 1:3.5; the sealed reaction kettle is then heated to a temperature of 120°C and a pressure of 3.3 kg / cm 2 , the reaction slurry is reacted under this condition for 45 min at a stirring speed of 180 r / min, and then filtered and washed after cooling, alcohol is used as a washing liquid for washing, the washing is stopped after the pH value of the washing liquid is 5.5 or higher, the material after washing is subjected to first drying by nitrogen gas flow, the temperature of the first drying is 130°C, the oxygen content in the oven is maintained below 1000 ppm during the first drying, the drying is stopped when the alcohol content in the material is below 0.1 wt%, then the material is crushed to a particle size of 2.7 μm, and the crushing is stopped, to obtain a positive electrode material, and the specific chemical formula is Na 2.00 Fe 1.05 Fe(CN) 4.92 F 1.08 ·1.10H2O·0.003HCl.

[0152] The detection data of the obtained positive electrode material are as follows:

[0153] Table 2

[0154]

[0155] Example 3

[0156] The sodium fluoride and iron fluoride are mixed to form a first solution, the mass ratio of sodium fluoride and iron fluoride is 1:0.3, the concentration of fluoride ion in the first solution is 3.45 mol / L; the first solution is mixed with a second solution, the second solution is a hydrogen fluoride solution with a concentration of 6.5 mol / L, the pH of the mixed solution is adjusted to 3.1 to prepare a bottom solution;

[0157] The sodium ferrocyanide, ferrous salt and sodium salt are respectively configured into solutions, the concentration of the sodium ferrocyanide solution is 1.5 mol / L, the concentration of the ferrous salt solution is 2 mol / L, and the concentration of the sodium salt solution is 4 mol / L, the temperature of the sodium ferrocyanide solution, the ferrous salt solution and the sodium salt solution is maintained at 80℃, the ferrous salt is ferrous chloride, sodium sulfite is added to the ferrous salt solution, the concentration of the sodium sulfite in the ferrous solution is 0.3 mol / L, the complexing agent is ethylenediaminetetraacetic acid (EDTA), the concentration of the EDTA in the ferrous salt solution is 0.08 mol / L, the mass ratio of sodium fluoride in the solute of the sodium salt solution is 15%, and the remaining sodium salt is sodium chloride, the mass ratio of the solute in the sodium ferrocyanide solution, the ferrous chloride solution and the sodium salt solution is 1:1.35:2.5; under the condition of stirring, the three solutions are added to the bottom solution, the adding time is 45 min, and the reaction is continued to age at 80℃ for 1.5 h to obtain a reaction slurry;

[0158] After the reaction slurry is filtered and washed with pure water until the conductivity of the washing liquid is ≤150 μS / cm (second washing), the obtained washing material is vacuum dried (second drying) until the water content is less than 0.2%, to obtain an intermediate product; the intermediate product is transferred into a sealed reaction kettle, and a hydrogen ion concentration of 0.8 mol / L hydrochloric acid-ethanol solution is added to slurry, to obtain a reaction slurry, the solid-liquid ratio of the reaction slurry is 1:3.5; the sealed reaction kettle is then heated to a temperature of 120℃, and the pressure is 3.3 kg / cm 2 , the reaction slurry is reacted under this condition for 45 min, the stirring speed is 180 r / min, then it is cooled and filtered and washed, the alcohol is used as a washing liquid, the washing is stopped after the pH value of the washing liquid is 5.5 or above, the material after washing is subjected to first drying by nitrogen gas flow, the temperature of the first drying is 130℃, the oxygen content in the oven is maintained to be less than 1000 ppm during the first drying, the drying is stopped after the alcohol content in the material is less than 0.1 wt%, then the material is crushed to a particle size of 2.7 μm, and the crushing is stopped, to obtain a positive electrode material, the specific chemical formula of which is Na 2.00 Fe 1.12 Fe(CN) 4.21 F1.79 • 1.48 H2O • 0.004 HC1.

[0159] The obtained positive electrode material detection data are as follows:

[0160] Table 3

[0161]

[0162]

[0163] Example 4

[0164] Sodium fluoride and iron fluoride are mixed to form a first solution, the mass ratio of sodium fluoride to iron fluoride is 1:0.2, the concentration of fluoride ions in the first solution is 2 mol / L; the first solution is mixed with a second solution, the second solution is a hydrogen fluoride solution with a concentration of 6.5 mol / L, the pH of the mixed solution is adjusted to 3.1 to prepare a bottom solution;

[0165] Sodium ferrocyanide, ferrous salt and sodium salt are respectively configured into solutions, the concentration of the sodium ferrocyanide solution is 1.5 mol / L, the concentration of the ferrous salt solution is 2 mol / L, and the concentration of the sodium salt solution is 4 mol / L; the temperature of the sodium ferrocyanide solution, the ferrous salt solution and the sodium salt solution is maintained at 80°C; the ferrous salt is ferrous chloride; sodium sulfite is added to the ferrous salt solution, the concentration of the sodium sulfite in the ferrous salt solution is 0.3 mol / L; the complexing agent is ethylenediaminetetraacetic acid (EDTA), the concentration of the EDTA in the ferrous salt solution is 0.08 mol / L; the mass ratio of sodium fluoride in the solute of the sodium salt solution is 15%, and the remaining sodium salt is sodium chloride; the mass ratio of the solutes in the sodium ferrocyanide solution, the ferrous chloride solution and the sodium salt solution is 1:1.35:2.5; under stirring, the three solutions are added to the bottom solution, the adding time is 45 min, and the reaction and aging are continued at 80°C for 1.5 h to obtain a reaction slurry;

[0166] The reaction slurry is filtered and washed with pure water until the conductivity of the washing liquid is ≤ 150 μS / cm (second washing), and the obtained washed material is vacuum dried (second drying) until the moisture content is less than 0.2%, to obtain an intermediate product; the intermediate product is transferred into a sealed reaction kettle, and a hydrogen ion concentration of 0.8 mol / L hydrochloric acid-ethanol solution is added to slurry, to obtain a reaction slurry, and the solid-liquid ratio of the reaction slurry is 1:3.5; the sealed reaction kettle is then heated to a temperature of 120°C and a pressure of 3.3 kg / cm2, and the reaction slurry is reacted under this condition for 45 min, with a stirring speed of 180 r / min, and then cooled, filtered and washed, the washing is performed using alcohol as the washing liquid, and the washing is stopped after the pH value of the washing liquid is 5.5 or higher, the washed material is subjected to first drying using a nitrogen gas flow, the temperature of the first drying is 130°C, the oxygen content in the oven is maintained to be lower than 1000 ppm during the first drying, the drying is stopped after the alcohol content in the material is lower than 0.1 wt%, then the material is crushed to a particle size of 2.7 μm, and the crushing is stopped, to obtain a positive electrode material, and the specific chemical formula is Na 2.00 Fe 1.00 Fe(CN) 5.00 F 1.00 ·1.13H2O·0.003HCl.

[0167] The obtained positive electrode material has the following test data:

[0168] Table 4

[0169]

[0170]

[0171] Example 5

[0172] Sodium fluoride and iron fluoride are mixed to form a first solution, the amount-of-substance ratio of sodium fluoride to iron fluoride is 1:0.2, and the fluoride ion concentration in the first solution is 1.5 mol / L; the first solution is mixed with a second solution, the second solution is a hydrogen fluoride solution with a concentration of 6.5 mol / L, and the pH of the mixed solution is adjusted to 3.1, to prepare a bottom liquid;

[0173] Sodium ferrocyanide, ferrous salt and sodium salt are configured into solutions respectively, the concentration of sodium ferrocyanide solution is 1.5 mol / L, the concentration of ferrous salt solution is 2 mol / L, the concentration of sodium salt solution is 4 mol / L, the temperature of sodium ferrocyanide solution, ferrous salt solution and sodium salt solution is maintained at 80℃, the ferrous salt is ferrous chloride, sodium sulfite is added into the ferrous salt solution, the concentration of sodium sulfite in the ferrous solution is 0.3 mol / L, the complexing agent is ethylenediaminetetraacetic acid (EDTA), the concentration of EDTA in the ferrous salt solution is 0.08 mol / L, the mass ratio of sodium fluoride in the solute of sodium salt solution is 15%, the remaining sodium salt is sodium chloride, the amount-of-substance ratio of solutes in sodium ferrocyanide, ferrous chloride and sodium salt solutions is 1:1.35:2.5; under the state of stirring, the three solutions are added into the bottom liquid together, the adding time is 45 min, the reaction and aging are continued at 80℃ for 1.5 h, and the reaction slurry is obtained;

[0174] After the reaction slurry is filtered and washed with pure water until the conductivity of the washing liquid is ≤150 μS / cm (second washing), the washing material obtained is vacuum dried (second drying) until the water content is less than 0.2%, and an intermediate product is obtained; the intermediate product is transferred into a sealed reaction kettle, and a hydrochloric acid-ethanol solution with a hydrogen ion concentration of 0.8 mol / L is added for slurry, and a reaction slurry is obtained, the solid-liquid ratio of the reaction slurry being 1:3.5; the sealed reaction kettle is then heated to a temperature of 120℃ and a pressure of 3.3 kg / cm 2 , the reaction slurry is reacted under this condition for 45 min at a stirring speed of 180 r / min, and then cooled, filtered and washed, the alcohol is used as a washing liquid, the washing is stopped after the pH value of the washing liquid is 5.5 or higher, the material after washing is subjected to first drying by nitrogen gas flow, the temperature of the first drying is 130℃, the oxygen content in the oven is maintained to be lower than 1000 ppm during the first drying, the drying is stopped after the alcohol content in the material is lower than 0.1 wt%, then the material is crushed to a particle size of 2.7 μm, and the crushing is stopped, and a positive electrode material is obtained, the specific chemical formula of which is Na 2.00 Fe 1.00 Fe(CN) 5.06 F 0.94 ·1.38H2O·0.003HCl.

[0175] The detection data of the positive electrode material obtained are as follows:

[0176] Table 5

[0177]

[0178]

[0179] Example 6

[0180] The first solution is prepared by mixing sodium fluoride and iron fluoride, the molar ratio of sodium fluoride to iron fluoride is 1:0.2, and the concentration of fluoride ions in the first solution is 3.45 mol / L; the first solution is mixed with the second solution, the second solution is a hydrogen fluoride solution with a concentration of 6.5 mol / L, the pH of the mixed solution is adjusted to 2.5 to prepare the bottom solution;

[0181] The sodium ferrocyanide solution, the ferrous salt solution and the sodium salt solution are prepared respectively, the concentration of the sodium ferrocyanide solution is 1.5 mol / L, the concentration of the ferrous salt solution is 2 mol / L, and the concentration of the sodium salt solution is 4 mol / L, the temperature of the sodium ferrocyanide solution, the ferrous salt solution and the sodium salt solution is maintained at 80℃, the ferrous salt is ferrous chloride, sodium sulfite is added to the ferrous salt solution, the concentration of sodium sulfite in the ferrous salt solution is 0.3 mol / L, the complexing agent is ethylenediaminetetraacetic acid (EDTA), the concentration of EDTA in the ferrous salt solution is 0.08 mol / L, the mass fraction of sodium fluoride in the solute of the sodium salt solution is 15%, and the remaining sodium salt is sodium chloride, the molar ratio of the solute in the sodium ferrocyanide solution, the ferrous chloride solution and the sodium salt solution is 1:1.35:2.5; under stirring, the three solutions are added to the bottom solution, the adding time is 45 min, and the reaction is continued at 80℃ for 1.5 h to obtain a reaction slurry;

[0182] The reaction slurry is filtered and washed with pure water until the conductivity of the washing liquid is ≤150 μS / cm (second washing), the washing material obtained is vacuum dried (second drying) until the water content is less than 0.2%, and an intermediate product is obtained; the intermediate product is transferred into a sealed reaction kettle, a hydrochloric acid-ethanol solution with a hydrogen ion concentration of 0.8 mol / L is added for slurry, and a reaction slurry is obtained, the solid-liquid ratio of the reaction slurry is 1:3.5; the sealed reaction kettle is then heated to a temperature of 120℃ and a pressure of 3.3 kg / cm 2 , the reaction slurry is reacted under this condition for 45 min at a stirring speed of 180 r / min, and then filtered and washed after cooling, alcohol is used as a washing liquid for washing, the washing is stopped after the pH value of the washing liquid is 5.5 or higher, the material after washing is subjected to first drying by nitrogen gas flow, the temperature of the first drying is 130℃, the oxygen content in the oven is maintained below 1000 ppm during the first drying, the drying is stopped when the alcohol content in the material is below 0.1 wt%, then the material is crushed to a particle size of 2.7 μm, and the crushing is stopped, to obtain a positive electrode material, and the specific chemical formula is Na 2.08 Fe 0.97 Fe(CN) 4.96 F 1.04 1.44H2O·0.004HCl.

[0183] The detection data of the obtained positive electrode material are as follows:

[0184] Table 6

[0185]

[0186] Example 7

[0187] The sodium fluoride and iron fluoride are mixed to form a first solution, the mass ratio of sodium fluoride and iron fluoride is 1:0.2, the concentration of fluoride ions in the first solution is 3.45 mol / L; the first solution is mixed with a second solution, the second solution is a hydrogen fluoride solution with a concentration of 6.5 mol / L, the pH of the mixed solution is adjusted to 2.0 to prepare a bottom solution;

[0188] The sodium ferrocyanide, ferrous salt and sodium salt are respectively configured into solutions, the concentration of the sodium ferrocyanide solution is 1.5 mol / L, the concentration of the ferrous salt solution is 2 mol / L, and the concentration of the sodium salt solution is 4 mol / L, the temperature of the sodium ferrocyanide solution, the ferrous salt solution and the sodium salt solution is maintained at 80℃, the ferrous salt is ferrous chloride, sodium sulfite is added to the ferrous salt solution, the concentration of the sodium sulfite in the ferrous salt solution is 0.3 mol / L, the complexing agent is ethylenediaminetetraacetic acid (EDTA), the concentration of the EDTA in the ferrous salt solution is 0.08 mol / L, the mass ratio of sodium fluoride in the solute of the sodium salt solution is 15%, and the remaining sodium salt is sodium chloride, the mass ratio of the solutes in the sodium ferrocyanide, ferrous chloride and sodium salt solutions is 1:1.35:2.5; under stirring, the three solutions are added to the bottom solution, the adding time is 45 min, and the reaction is continued at 80℃ for 1.5 h to obtain a reaction slurry;

[0189] After the reaction slurry is filtered and washed with pure water until the conductivity of the washing liquid is ≤150 μS / cm (second washing), the obtained washing material is vacuum dried (second drying) until the water content is less than 0.2%, to obtain an intermediate product; the intermediate product is transferred into a sealed reaction kettle, and a hydrogen ion concentration of 0.8 mol / L hydrochloric acid-ethanol solution is added to slurry, to obtain a reaction slurry, the solid-liquid ratio of the reaction slurry is 1:3.5; the sealed reaction kettle is then heated to a temperature of 120℃, and the pressure is 3.3 kg / cm 2 , the reaction slurry is reacted under this condition for 45 min, the stirring speed is 180 r / min, then it is cooled and filtered and washed, the alcohol is used as a washing liquid, the washing is stopped after the pH of the washing liquid is 5.5 or above, the material after washing is subjected to first drying by nitrogen gas flow, the temperature of the first drying is 130℃, the oxygen content in the oven is maintained to be less than 1000 ppm during the first drying, the drying is stopped after the alcohol content in the material is less than 0.1 wt%, then the material is crushed to a particle size of 2.7 μm, and the crushing is stopped, to obtain a positive electrode material, the specific chemical formula of which is Na 2.16 Fe 0.93 Fe(CN) 5.08 F0.92 • 1.58 H2O • 0.007 HC1.

[0190] The obtained positive electrode material detection data are as follows:

[0191] Table 7

[0192]

[0193] Example 8

[0194] Sodium fluoride and ferric fluoride are mixed to form a first solution, the amount-of-substance ratio of sodium fluoride to ferric fluoride is 1:0.2, and the concentration of fluoride ions in the first solution is 3.45 mol / L; the first solution is mixed with a second solution, the second solution is a hydrogen fluoride solution with a concentration of 6.5 mol / L, the pH of the mixed solution is adjusted to 3.1, and a bottom solution is prepared;

[0195] Sodium ferrocyanide, ferrous salt, and sodium salt are respectively configured into solutions, the concentration of the sodium ferrocyanide solution is 2 mol / L, the concentration of the ferrous salt solution is 2.5 mol / L, and the concentration of the sodium salt solution is 3 mol / L; the temperature of the sodium ferrocyanide solution, the ferrous salt solution, and the sodium salt solution is maintained at 80°C; the ferrous salt is ferrous chloride; sodium sulfite is added to the ferrous salt solution, and the concentration of the sodium sulfite in the ferrous salt solution is 0.5 mol / L; the complexing agent is ethylenediaminetetraacetic acid (EDTA), and the concentration of the EDTA in the ferrous salt solution is 0.2 mol / L; the mass fraction of sodium fluoride in the solute of the sodium salt solution is 15%, and the remaining sodium salt is sodium chloride; the amount-of-substance ratio of the solutes in the sodium ferrocyanide solution, the ferrous chloride solution, and the sodium salt solution is 1:1.35:2.5; under stirring, the three solutions are added to the bottom solution, the adding time is 45 min, and the reaction is continued at a temperature of 80°C for 1.5 h to obtain a reaction slurry;

[0196] After the reaction slurry is filtered and washed with pure water until the conductivity of the washing liquid is ≤150 μS / cm (second washing), the obtained washing material is vacuum dried (second drying) until the water content is less than 0.2%, and an intermediate product is obtained; the intermediate product is transferred into a sealed reaction kettle, a hydrogen ion concentration of 0.8 mol / L hydrochloric acid-ethanol solution is added for slurry, and a reaction slurry is obtained, the solid-liquid ratio of the reaction slurry is 1:3.5; the sealed reaction kettle is then heated to a temperature of 120°C and a pressure of 3.3 kg / cm 2, the reaction slurry is reacted for 45 min under the condition, the stirring speed is 180 r / min, then after cooling, it is filtered and washed, the alcohol is used as the washing liquid, the washing is stopped after the pH value of the washing liquid is 5.5 and above, the material after washing is dried by the nitrogen airflow, the temperature of the first drying is 130 DEG C, the oxygen content in the oven is maintained below 1000 ppm during the first drying, the drying is stopped after the alcohol content in the material is below 0.1 wt%, then after the material is crushed to the particle size of 2.7 μm, the crushing is stopped, the positive electrode material is obtained, and the specific chemical formula is Na 2.00 Fe 1.02 Fe(CN) 4.99 F 1.01 ·1.19H2O·0.003HCl.

[0197] The detection data of the obtained positive electrode material are as follows:

[0198] Table 8

[0199]

[0200] Example 9

[0201] Sodium fluoride and iron fluoride are mixed to form a first solution, the amount-of-substance ratio of sodium fluoride to iron fluoride is 1:0.2, the concentration of fluoride ions in the first solution is 3.45 mol / L; the first solution is mixed with a second solution, the second solution is a hydrogen fluoride solution with a concentration of 6.5 mol / L, the pH of the mixed solution is adjusted to 3.1, and a bottom solution is prepared;

[0202] Sodium ferrocyanide, ferrous salt and sodium salt are respectively configured into solutions, the concentration of the sodium ferrocyanide solution is 1.5 mol / L, the concentration of the ferrous salt solution is 2 mol / L, and the concentration of the sodium salt solution is 4 mol / L, the temperature of the sodium ferrocyanide solution, the ferrous salt solution and the sodium salt solution is maintained at 80 DEG C, the ferrous salt is ferrous chloride, sodium sulfite is added to the ferrous salt solution, the concentration of sodium sulfite in the ferrous salt solution is 0.3 mol / L, the complexing agent is ethylenediaminetetraacetic acid (EDTA), the concentration of EDTA in the ferrous salt solution is 0.08 mol / L, the mass fraction of sodium fluoride in the solute of the sodium salt solution is 15%, and the remaining sodium salt is sodium chloride, the amount-of-substance ratio of sodium ferrocyanide, ferrous chloride and sodium salt in the solution is 1:1:1.5; under the stirring state, the three solutions are added to the bottom solution, the adding time is 45 min, the reaction and aging are continued at 80 DEG C for 1.5 h, and a reaction slurry is obtained;

[0203] The reaction slurry is filtered and washed with pure water until the conductivity of the washing liquid is less than or equal to 150 μS / cm (second washing), and the obtained washed material is vacuum dried (second drying) until the moisture content is less than 0.2%, to obtain an intermediate product; the intermediate product is transferred into a sealed reaction kettle, and a hydrogen ion concentration of 0.8 mol / L hydrochloric acid-ethanol solution is added to slurry, to obtain a reaction slurry, and the solid-liquid ratio of the reaction slurry is 1:3.5; the sealed reaction kettle is then heated to a temperature of 120°C and a pressure of 3.3 kg / cm 2 , the reaction slurry is reacted under this condition for 45 min at a stirring speed of 180 r / min, and then cooled, filtered and washed; the washing is stopped after the washing liquid is adjusted to a pH of 5.5 or higher, and the washed material is first dried by a nitrogen gas flow, the first drying temperature is 130°C, the oxygen content in the oven is maintained to be less than 1000 ppm during the first drying, and the drying is stopped after the alcohol content in the material is less than 0.1 wt%; then the material is crushed to a particle size of 2.7 μm, and the crushing is stopped, to obtain a positive electrode material, and the specific chemical formula of the positive electrode material is Na 2.16 Fe 1.12 Fe(CN) 5.38 F 1.01 ·1.55H2O·0.004HCl.

[0204] The obtained positive electrode material has the following test data:

[0205] Table 9

[0206]

[0207] Example 10

[0208] Sodium fluoride and iron fluoride are mixed to form a first solution, the amount-of-substance ratio of sodium fluoride to iron fluoride is 1:0.2, and the fluoride ion concentration in the first solution is 3.45 mol / L; the first solution is mixed with a second solution, the second solution is a hydrogen fluoride solution with a concentration of 6.5 mol / L, and the pH of the mixed solution is adjusted to 3.1, to prepare a bottom liquid;

[0209] Sodium ferrocyanide, ferrous salt and sodium salt are configured into solution respectively, the concentration of sodium ferrocyanide solution is 1.5mol / L, the concentration of ferrous salt solution is 2mol / L, the concentration of sodium salt solution is 4mol / L, the temperature of sodium ferrocyanide solution, ferrous salt solution and sodium salt solution is maintained at 80℃, the ferrous salt is ferrous chloride, sodium sulfite is added into the ferrous salt solution, the concentration of sodium sulfite in the ferrous salt solution is 0.3mol / L, the complexing agent is ethylenediaminetetraacetic acid (EDTA), the concentration of EDTA in the ferrous salt solution is 0.08mol / L, the mass ratio of sodium fluoride in the solute of sodium salt solution is 15%, the rest of sodium salt is sodium chloride, the amount-of-substance ratio of solute in sodium ferrocyanide, ferrous chloride and sodium salt solution is 1:1.35:2.5; under the state of stirring, the three solutions are added into the bottom liquid together, the adding time is 45min, the reaction and aging is continued at 80℃ for 1.5h, the reaction slurry is obtained;

[0210] After the reaction slurry is filtered and washed with pure water until the conductivity of washing liquid is ≤150μS / cm (second washing), the washing material obtained is vacuum dried (second drying) until the water content is less than 0.2%, the intermediate product is obtained; the intermediate product is transferred into a sealed reaction kettle, and a hydrochloric acid-ethanol solution with a hydrogen ion concentration of 0.5mol / L is added for slurry, the reaction slurry is obtained, the solid-liquid ratio of the reaction slurry is 1:3.5; the sealed reaction kettle is then heated to a temperature of 120℃ and a pressure of 3.3kg / cm 2 , the reaction slurry is reacted under this condition for 45min, the stirring speed is 180r / min, then it is cooled, filtered and washed, alcohol is used as washing liquid, the washing is stopped after the pH value of washing liquid is 5.5 or above, the material after washing is subjected to first drying by nitrogen gas flow, the temperature of first drying is 130℃, the oxygen content in the oven is maintained below 1000ppm during first drying, the drying is stopped after the alcohol content in the material is below 0.1wt%, then the material is crushed to a particle size of 2.7μm, the crushing is stopped, the positive electrode material is obtained, and its specific chemical formula is Na 2.00 Fe 1.00 Fe(CN) 4.99 F 1.01 ·1.24H2O·0.002HCl.

[0211] The detection data of the positive electrode material obtained are as follows:

[0212] Table 10

[0213]

[0214] Example 11

[0215] The sodium fluoride and iron fluoride are mixed to form a first solution, the molar ratio of sodium fluoride and iron fluoride is 1:0.2, the concentration of fluoride ions in the first solution is 3.45 mol / L; the first solution is mixed with a second solution, the second solution is a hydrogen fluoride solution with a concentration of 6.5 mol / L, the pH of the mixed solution is adjusted to 3.1 to prepare a bottom solution;

[0216] The sodium ferrocyanide, ferrous salt and sodium salt are respectively configured into solutions, the concentration of the sodium ferrocyanide solution is 1.5 mol / L, the concentration of the ferrous salt solution is 2 mol / L, and the concentration of the sodium salt solution is 4 mol / L, the temperature of the sodium ferrocyanide solution, the ferrous salt solution and the sodium salt solution is maintained at 80℃, the ferrous salt is ferrous chloride, sodium sulfite is added to the ferrous salt solution, the concentration of the sodium sulfite in the ferrous salt solution is 0.3 mol / L, the complexing agent is ethylenediaminetetraacetic acid (EDTA), the concentration of the EDTA in the ferrous salt solution is 0.08 mol / L, the mass ratio of sodium fluoride in the solute of the sodium salt solution is 15%, and the remaining sodium salt is sodium chloride, the molar ratio of the solutes in the sodium ferrocyanide, ferrous chloride and sodium salt solutions is 1:1.35:2.5; under stirring, the three solutions are added to the bottom solution, the adding time is 45 min, and the reaction is continued at 80℃ for 1.5 h to obtain a reaction slurry;

[0217] The reaction slurry is filtered and washed with pure water until the conductivity of the washing liquid is ≤150 μS / cm (second washing), the washing material obtained is vacuum dried (second drying) until the water content is less than 0.2%, and an intermediate product is obtained; the intermediate product is transferred into a sealed reaction kettle, a hydrochloric acid-ethanol solution with a hydrogen ion concentration of 0.3 mol / L is added for slurry, and a reaction slurry is obtained, the solid-liquid ratio of the reaction slurry is 1:3.5; the sealed reaction kettle is then heated to a temperature of 120℃, and the pressure is 3.3 kg / cm 2 , the reaction slurry is reacted under this condition for 45 min, the stirring speed is 180 r / min, then it is cooled and filtered and washed, alcohol is used as a washing liquid, the washing is stopped after the pH value of the washing liquid is 5.5 or higher, the material after washing is subjected to first drying by nitrogen gas flow, the temperature of the first drying is 130℃, the oxygen content in the oven is maintained to be lower than 1000 ppm during the first drying, the drying is stopped after the alcohol content in the material is lower than 0.1 wt%, then the material is crushed to a particle size of 2.7 μm, and the crushing is stopped, and a positive electrode material is obtained, and the specific chemical formula is Na 2.00 Fe 1.00 Fe(CN) 4.99 F 1.01 ·1.74H2O·0.001HCl.

[0218] The detection data of the positive electrode material obtained are as follows:

[0219] Table 11

[0220]

[0221] Comparative Example 1

[0222] The difference from Example 1 is that sodium fluoride and iron fluoride are respectively replaced by sodium chloride and iron chloride in equal amounts, and finally a comparative positive electrode material is obtained, and the specific chemical formula is Na 2.00 Fe 1.00 Fe(CN) 5.75 F 0.25 ·1.65H2O·0.002HCl.

[0223] The test data of the obtained Prussian blue sodium battery material are as follows:

[0224] Table 12

[0225]

[0226] Comparative Example 2

[0227] The difference from Example 1 is that hydrogen fluoride is not added, and finally a comparative positive electrode material is obtained, and the specific chemical formula is Na 2.00 Fe 1.00 Fe(CN) 5.55 F 0.45 ·1.45H2O·0.001HCl.

[0228] The test data of the obtained Prussian blue sodium battery material are as follows:

[0229] Table 13

[0230]

[0231] Comparative Example 3

[0232] Preparation of Prussian blue type positive electrode material carbon-manganese nickel sodium ferrocyanide:

[0233] (1) 0.04 mol of sodium ferrocyanide and 20 mg of activated Vulcan carbon were weighed and dissolved in 100 mL of deionized water to prepare solution A, wherein the concentration of sodium ferrocyanide was 0.4 mol / L, and the concentration of Vulcan carbon was 0.2 g / L;

[0234] (2) 0.032 mol of manganese sulfate and 0.128 mol of sodium citrate were weighed and dissolved in 80 mL of deionized water to prepare solution B, wherein the concentration of manganese sulfate was 0.4 mol / L, and the molar ratio of manganese sulfate to sodium citrate was 1:4;

[0235] (3) 0.008 mol of nickel sulfate and 0.032 mol of sodium citrate were weighed and dissolved in 20 mL of deionized water to prepare solution C, wherein the concentration of nickel sulfate was 0.4 mol / L, the molar ratio of nickel sulfate to sodium citrate was 1:4, and the volume ratio of solution A, solution B and solution C was 1:0.8:0.2;

[0236] (4) Solution A was placed on a magnetic stirrer and heated to 60°C, and solution B was added dropwise to the high-speed stirred solution A using a peristaltic pump. White precipitate was generated during the dropwise addition process, and the dropwise addition speed was 0.25 mL / min to obtain a precursor solution;

[0237] (5) The precursor solution A was continuously stirred for 2 hours, and solution C was added dropwise to the high-speed stirred precursor solution A using a peristaltic pump, and the dropwise addition speed was 0.25 mL / min.

[0238] (6) The mixed solution was continuously stirred for 0.5 h and then statically placed for 6 h;

[0239] (7) The mixed solution after static placement was centrifuged to obtain a light green precipitate, which was washed, centrifuged and then dried at 120°C under vacuum for 24 h to obtain a Prussian blue-based positive electrode material.

[0240] II. Test method

[0241] Property test of positive electrode material

[0242] The free water content was tested by Karl Fischer coulometry;

[0243] The crystal water was tested by high-temperature weight loss method;

[0244] The D10 / D50 / D90 particle size was tested by a laser particle size analyzer according to the laser diffraction method;

[0245] The BET specific surface area was tested by a BET tester using nitrogen adsorption method;

[0246] Impurity elements were tested by inductively coupled plasma optical emission spectrometry (ICP-OES);

[0247] Magnetic substances were collected by a magnet, then dissolved with aqua regia, and tested by inductively coupled plasma optical emission spectrometry.

[0248] Iron dissolution amount: 1 g of the sample to be tested was added into 100 mL of a hydrogen fluoride-ethanol solution with a concentration of 0.1 mol / L, and stirred and dissolved at a temperature of 45°C for 30 min, then filtered, and the content of iron elements in the filtrate was measured, which was the iron dissolution amount.

[0249] Tap density refers to GB T 31057.1-2014, and is tested by a funnel method.

[0250] Tap density is tested by a tap density tester, and the vibration frequency is 5000 times.

[0251] Tap density is tested by a tap density tester, and the vibration frequency is 5000 times.

[0252] Chloride ions are tested by a chloride ion selective electrode.

[0253] The test method of sodium ion diffusion coefficient is obtained by electrochemical impedance spectroscopy (EIS) test.

[0254] III. Analysis of test results of each embodiment and comparative example

[0255] The above obtained material is assembled into a button cell, and the assembly process is as follows:

[0256] The positive electrode material obtained in the example or comparative example is mixed with acetylene black (conductive agent) and polyvinylidene fluoride (PVDF, as a binder) in a mass ratio of 85:10:5, and the mass is weighed to 0.001g, to obtain a positive electrode active mixture. A carbon-coated aluminum foil is used as a current collector, the positive electrode active mixture is mixed with N-methyl pyrrolidone and stirred to form a slurry, the slurry is uniformly coated on the carbon-coated aluminum foil, dried in a 100°C oven, cut into a positive electrode sheet with a diameter of 15mm and a thickness of 0.10mm, and the positive electrode sheet is weighed to 0.0001g.

[0257] Battery assembly

[0258] In an inert gas glove box with water and oxygen content ≤0.0005%, a metal sodium sheet is used as a negative electrode sheet, a polypropylene microporous film is used as a separator, a 1mol / L sodium hexafluorophosphate and mixed carbonate-based organic solvent [ethylene carbonate (EC) / diethyl carbonate (DEC) / fluoroethylene carbonate (FEC) (volume ratio of EC, DEC, FEC is 1:1:0.05)] electrolyte, the positive electrode sheet, the negative electrode sheet, the separator, and the electrolyte are assembled into a button cell, and the button cell is sealed and tested by a sodium ion battery electrochemical performance tester.

[0259] Battery test

[0260] The prepared button cell is charged-discharged cycled at 25°C on a sodium ion battery electrochemical performance tester, and the charge-discharge test is as follows:

[0261] a) 0.2C rate current charging, and the charging limit voltage is 4.2V;

[0262] b) 0.2C rate current discharging, and the discharging termination voltage is 2.0V.

[0263] The button cell was placed in a thermostat (25±0.2℃) for cycle performance test, and the capacity retention rate was 89.9% after 1000 cycles at 1C (the capacity retention rate of the conventional prussian blue sodium battery material was less than 85% after 1000 cycles). The test results are as follows:

[0264] Table 14

[0265]

[0266]

[0267] As can be seen from the data in Table 14, the capacity retention rates of the positive electrode materials in the embodiments of the present application were all higher than 86% after 1000 cycles at 1C, and the initial charge specific capacity at 0.2C was all above 150 mAh / g, and the initial discharge specific capacity at 0.2C was all above 144 mAh / g, indicating that the comprehensive electrical performance of the positive electrode materials in the embodiments of the present application was obviously superior to that of the prussian blue sodium battery materials in Comparative Examples 1 to 3.

[0268] Further, Figure 2 The charge specific capacity and discharge specific capacity test results of the sodium ion battery of the positive electrode material of Example 1 are shown in the following figures: Figure 2 It can be seen that the positive electrode material of Example 1 has excellent charge and discharge performance.

[0269] The chemical formula of the positive electrode material in Comparative Example 1 is Na 2.00 Fe 1.00 Fe(CN) 5.75 F 0.25 ·1.65H2O·0.002HCl, and the chemical formula of the positive electrode material in Comparative Example 2 is Na 2.00 Fe 1.00 Fe(CN) 5.55 F 0.45 ·1.45H2O·0.001HCl. It can be seen that the contents of cyanide ions and fluorine ions in the positive electrode materials in Comparative Examples 1 and 2 are all outside the range of 4.20<z<5.50 in the general chemical formula Na x Fe y Fe(CN) z F 6-z nH2O·mHCl, and the content of fluorine ions in the positive electrode materials in Comparative Examples 1 and 2 is lower than that in the prussian blue material obtained in the embodiments of the present application, thereby resulting in that the electrochemical performance of the sodium ion battery corresponding to the positive electrode material in Comparative Examples 1 and 2 is poorer than that of the sodium ion battery corresponding to the positive electrode material obtained in the embodiments of the present application.

[0270] The electrochemical performance results of the button cells with the positive electrode materials provided in Table 14 and the button cells with the positive electrode materials provided in Comparative Examples 1-3 show that by controlling the chemical composition of the Prussian blue material, introducing fluorine element to replace part of the cyanide ions, reducing the content of crystal water, and occupying the crystal water vacancy with HCl, the stability of the positive electrode material is effectively improved, and the electrochemical performance of the positive electrode material is improved.

[0271] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration and playing the same role and effects as the technical idea within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the gist of the present application, various modifications that can be thought of by those skilled in the art, other modes constructed by combining part of the elements of the embodiments are also included in the scope of the present application.

Claims

1. A positive electrode material, characterized by, The positive electrode material comprises a Prussian blue material, a molecular formula of the Prussian blue material is Na x Fe y Fe(CN) z F 6-z ·nH2O·mHCl, wherein, 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.90 1.

2. The positive electrode material of claim 1, wherein, The diffusion coefficient of sodium ions in the Prussian blue material is 3.00 x 10 -13 cm 2 / s~1.00 x 10 -10 cm 2 / s.

3. A method for producing a positive electrode material, characterized by, The preparation method of the positive electrode material comprises: a base solution is provided, the base solution comprising sodium ions, iron ions and hydrogen fluoride; the base solution, a sodium ferrocyanide solution, a ferrous salt solution and a sodium salt solution are mixed, and the mixture is subjected to aging treatment to obtain an aged slurry; the aged slurry is subjected to first solid-liquid separation treatment to obtain an intermediate product; the intermediate product is subjected to slurry treatment to obtain a reaction slurry; the reaction slurry is subjected to reaction treatment to obtain the positive electrode material; the ferrous salt solution is selected from any one or more of ferrous chloride solution, ferrous sulfate solution and ferrous acetate solution; the solute of the sodium salt solution comprises sodium fluoride, and the solute of the sodium salt solution further comprises any one or more of sodium chloride, sodium sulfate, sodium acetate and sodium citrate.

4. The method of claim 3, wherein the lithium transition metal oxide is prepared by the steps of: preparing a lithium transition metal oxide precursor; and calcining the lithium transition metal oxide precursor in the presence of a lithium source. The step of obtaining the base solution comprises mixing a first solution and a second solution to obtain the base solution, the first solution comprising sodium fluoride and iron fluoride, and the second solution comprising hydrogen fluoride; the pH value of the base solution is 2.5-3.5; the molar ratio of the solute of the sodium ferrocyanide solution, the solute of the ferrous salt solution and the solute of the sodium salt solution is 1:(1.2-1.5):(2-3); wherein, the concentration of the sodium ferrocyanide solution is 1 mol / L-2 mol / L; and / or, the concentration of the ferrous salt solution is 1.5 mol / L-2.5 mol / L; and / or, the ferrous salt solution further comprises a reducing agent and a complexing agent; and / or, the reducing agent is a sulfite and / or hydrazine hydrate; and / or, the concentration of the reducing agent in the ferrous salt solution is 0.1 mol / L-0.5 mol / L; and / or, the complexing agent is ethylenediaminetetraacetic acid and / or citric acid; and / or, the concentration of the complexing agent in the ferrous salt solution is 0.01 mol / L-0.2 mol / L; and / or, the concentration of the sodium salt solution is 3 mol / L-5 mol / L, and the mass fraction of sodium fluoride in the solute of the sodium salt solution is 10%-20%.

5. The method for preparing the cathode material according to claim 4, characterized in that, the temperature of the aging treatment is 70°C-90°C, and the time of the aging treatment is 1 h-2 h; the molar ratio of sodium fluoride to iron fluoride in the first solution is 1:(0.1-0.2); and / or, the total concentration of fluoride ions in the first solution is 2 mol / L-4 mol / L; and / or, the concentration of the second solution is 5 mol / L-8 mol / L.

6. The method of claim 3, wherein the lithium transition metal oxide is prepared by the steps of: preparing a lithium transition metal oxide precursor; and calcining the lithium transition metal oxide precursor in the presence of a lithium source. The intermediate product and an acid solution are mixed and slurried to obtain a reaction slurry; and / or, the temperature of the reaction treatment is 110°C-130°C, and the time of the reaction treatment is 30 min-60 min; and / or, the acid solution is a hydrochloric acid-ethanol solution, and the concentration of hydrogen ions in the acid solution is 0.5 mol / L-1 mol / L; and / or, the mass ratio of solid to liquid in the reaction slurry is 1:(3-4).

7. The method for preparing the cathode material according to claim 3, characterized in that, The intermediate product is sequentially subjected to second washing and second drying before the slurry treatment, wherein the conductivity of washing water after the second washing is ≤150 μS / cm, and the water content in the intermediate product is lower than 0.2%.

8. The method for preparing the cathode material according to claim 3, characterized in that, The product obtained after the reaction is subjected to a second solid-liquid separation treatment, a first washing, a first drying, and crushing in sequence, to obtain the positive electrode material; And / or, the first washing is performed using alcohol, and a pH value of the washing liquid after washing is 5.5 or higher; The first drying is performed under protection of a protective gas, a mass fraction of ethanol in the material is less than 0.1%, a temperature of the first drying is 110 DEG C to 150 DEG C, and an oxygen content in the environment during the first drying is less than 1000 ppm; A particle size of the positive electrode material obtained after the crushing is 1 mu m to 5 mu m.

9. A positive electrode sheet characterized by comprising: The positive electrode plate comprises the positive electrode material according to any one of claims 1 to 2 or the positive electrode material prepared by the preparation method of the positive electrode material according to any one of claims 3 to 8.

10. A sodium-ion battery comprising a positive electrode sheet, characterized by, The positive electrode plate is the positive electrode plate according to claim 9.

Images