Method for preparing nano-sodium vanadium phosphate material

Abstract

The present invention relates to a method for preparing a nanometer sodium vanadium phosphate material, comprising the following preparation steps: 1) weighing raw materials, the raw materials consisting of a tetravalent vanadium compound, a sodium phosphate salt and sodium fluoride, or the raw materials consisting of a tetravalent vanadium compound and a sodium phosphate salt; and 2) placing the raw materials in a high-speed homogenizing mill to complete a rapid nucleation process and control a crystal growth process. The present invention takes use of the principle of atom economy, and uses the milling device having a high power and a high rotation speed to perform efficient preparation of the nanometer sodium vanadium phosphate. The present invention achieves efficient atom utilization of the raw materials, and avoids generation of unnecessary waste materials and waste of the raw materials, which omits waste liquid treatment steps involved in solvent emission and washing processes, thereby achieving green preparation. On the basis of the milling device having a high power and a high rotation speed, high-speed collision is achieved to accelerate the reaction and to efficiently control the particle size of the product, thereby achieving nano-scale preparation. The present invention has the advantages of simple operation, high efficiency, easy industrial scale-up production and the like and helps to promote the research, popularization and application of the sodium vanadium phosphate material in the field of electrochemical energy storage.

Description

Method for preparing nano sodium vanadium phosphate material TECHNICAL FIELD

[0001] The present application relates to the technical field of electrode material preparation, and particularly relates to a method for preparing nano sodium vanadium phosphate material which can be used as electrode material of alkali metal secondary battery such as lithium, sodium and potassium. BACKGROUND

[0002] As a sodium ion superconductor material, sodium vanadium phosphate has excellent sodium ion migration efficiency and is an ideal electrode material of sodium ion secondary battery. At present, the preparation of sodium vanadium phosphate material mainly adopts high-temperature solid-phase synthesis, sol-gel method and other methods. However, the particle size distribution of sodium vanadium phosphate prepared by these methods is relatively uneven, and there is a problem of high energy consumption caused by long preparation time and high temperature, which greatly restricts the progress of large-scale production.

[0003] In recent years, the method for efficiently preparing sodium vanadium phosphate by hydrothermal / solvothermal method has gradually emerged, such as the method for preparing sodium vanadium phosphate fluoride disclosed in Chinese patent application CN105762355A, the method for preparing sodium vanadium phosphate fluoride and its application disclosed in Chinese patent application CN105762356A, and the sodium vanadium phosphate fluoride and its preparation method and application disclosed in Chinese patent application CN107154493A. Although the liquid phase reaction avoids the problems of high energy consumption and uneven product particle size distribution, it has the problem of poor electronic conductivity caused by large particle size, which affects the sodium storage performance of the product. In view of this problem, some researchers have proposed methods such as ion exchange (such as the method for preparing sodium vanadium phosphate material disclosed in Chinese patent application CN114572957A and the method for preparing nano sodium vanadium phosphate by nucleation and crystallization isolation disclosed in Chinese patent application CN114604842A) to realize the nanometerization of sodium vanadium phosphate, effectively control the particle size of sodium vanadium phosphate, improve the electronic / ion transport efficiency of sodium vanadium phosphate, and thus improve its sodium storage performance. It is worth noting that the use of a large amount of solvent in the liquid phase synthesis process and the washing process of the primary product will produce a large amount of wastewater, which not only increases the preparation cost, but also wastes raw material resources. So far, there is no practical solution to this problem.

[0004] SUMMARY

[0005] Based on the difficulties and problems faced in the preparation and application of sodium vanadium phosphate material, the application provides a method for preparing nano sodium vanadium phosphate material; the high-power high-speed grinding equipment is used to efficiently prepare the nano sodium vanadium phosphate material according to the principle of atomic economy; meanwhile, the atomic utilization of raw materials is efficiently realized, no redundant waste is generated, and no waste liquid treatment link generated by the solvent discharge and washing process is cancelled, so that green preparation is realized; the high-power high-speed grinding equipment is used to realize high-speed collision acceleration reaction, effectively control the particle size of the product, and realize nano preparation; the preparation method has the advantages of simple operation, high efficiency, easy industrial amplification, and the like, and is beneficial to promoting the research and popularization and application of sodium vanadium phosphate material in the field of electrochemical energy storage.

[0006] In order to achieve the above purpose, the application adopts the following technical scheme:

[0007] A method for preparing nano sodium vanadium phosphate material, the sodium vanadium phosphate is in the form of nanoparticles, and the chemical formula is Na2+x(VOPO4)2F x ·yH2O, wherein x=0 or 1, and y=0-2; the preparation steps are as follows:

[0008] 1) The raw materials are weighed according to the raw material ratio, the raw materials are composed of tetravalent vanadium, sodium phosphate salt and sodium fluoride, or the raw materials are composed of tetravalent vanadium and sodium phosphate salt, and the raw material ratio meets the atomic number ratio of Na2+x(VOPO4)2F x ·yH2O;

[0009] 2) The raw materials are placed in a high-speed homogenizing mill, the speed and reaction time of the high-speed homogenizing mill are adjusted, and the rapid nucleation process and the controlled crystallization growth process are sequentially completed; in the rapid nucleation process, the speed of the high-speed homogenizing mill is controlled to be 1000-5000 rpm, and the forward rotation or the reverse rotation is at least 10 min; in the controlled crystallization growth process, the speed of the high-speed homogenizing mill is controlled to be 300-1000 rpm, and the forward rotation and the reverse rotation are alternately performed for 1-5 times, and each time is at least 15 min; and the target product is obtained after reaction.

[0010] Further, in the step 1), the tetravalent vanadium is one or both of VO2 and VOOH.

[0011] Further, in the step 1), the sodium phosphate salt is one or both of Na2HPO4 and NaH2PO4.

[0012] Further, in the step 2), the high-speed homogenizing mill is a Chinese herbal medicine grinder, a colloid mill or a planetary ball mill.

[0013] Further, in the step 2), when the forward rotation and the reverse rotation are switched, at least 10 min is interval.

[0014] Further, the prepared sodium vanadium phosphate has a particle size of less than or equal to 100 nm.

[0015] Compared with the prior art, the present application has the following beneficial effects:

[0016] 1) Based on the principle of atomic economy and supplemented by the method of "rapid nucleation + controlled crystallization growth", the green and efficient preparation of sodium vanadium phosphate material with controllable particle size distribution is realized;

[0017] 2) Based on the principle of atomic economy, the utilization rate of each atom of the reaction raw material is maximized, and the residues of excess raw materials and the generation of three wastes are avoided; the conventional three waste product treatment, reaction product washing and drying processes are cancelled, and the production and preparation cost is reduced;

[0018] 3) Based on the high centrifugal force and high shear force of the high-speed homogenizing mill such as colloidal mill, the reaction raw materials are rapidly rotated and collided in the mill to achieve the required activation energy; by reducing the mass transfer resistance to the minimum value, the collision probability is greatly improved, a large number of small nanocrystal nuclei are rapidly formed, the reaction is promoted to occur rapidly, the sodium vanadium phosphate is rapidly nucleated, and the separation of the nucleation and crystallization processes is effectively realized; by controlling the reaction frequency and time, the crystallization growth process is controlled, the combination and growth between the crystal nuclei are controlled, and the purpose of controlling the particle size of sodium vanadium phosphate material is achieved, thereby realizing the effective regulation of sodium vanadium phosphate in nanometer scale;

[0019] 4) Not only can the generation of three wastes be effectively avoided, the process be simplified, and the production and preparation cost be reduced, but also the particle size of sodium vanadium phosphate can be effectively regulated, and the controllable preparation of the average particle size in nanometer level can be realized;

[0020] 5) The preparation conditions are green, simple and efficient, and easy to realize scale-up production;

[0021] 6) The prepared product has advantages in structure and performance; the nanocrystallization of sodium vanadium phosphate increases the conductivity and electrolyte wettability of the material, thereby showing excellent electrochemical performance, and is expected to improve the limitations of sodium vanadium phosphate materials in the application of energy storage field, and has certain application prospect in the electrode materials of lithium, sodium and potassium alkali metal secondary batteries. BRIEF DESCRIPTION OF DRAWINGS

[0022] Fig. 1 is an XRD curve of the prepared sodium vanadium phosphate material in Example 1 of the present application.

[0023] Fig. 2 is a particle size distribution graph of the prepared sodium vanadium phosphate material in Example 1 of the present application.

[0024] Fig. 3 is a SEM graph of the prepared sodium vanadium phosphate material in Example 2 of the present application.

[0025] Figure 4 is a cyclic voltammogram of the sodium vanadium phosphate material prepared in Example 2 of the present application.

[0026] Figure 5 is a constant current charge-discharge curve of the sodium vanadium phosphate material prepared in Example 3 of the present application. DETAILED DESCRIPTION

[0027] The chemical formula of the sodium vanadium phosphate material is Na 2+x (VOPO4)2F x ·yH2O, wherein x = 0 or 1, y = 0-2, and the micro-morphology of the material is nanoparticle, with concentrated nanoparticle size distribution and high specific surface area.

[0028] The sodium vanadium phosphate material is prepared based on the principle of atom economy and the method of "fast nucleation + controlled crystallization growth", and the specific steps are as follows:

[0029] 1) The raw materials are weighed, which are composed of tetravalent vanadium, sodium phosphate salt and sodium fluoride, or tetravalent vanadium and sodium phosphate salt; the tetravalent vanadium is one or both of VO2 and VOOH, and the sodium phosphate salt is one or both of Na2HPO4 and NaH2PO4. The raw material ratio meets the principle of atom economy, that is, it meets the atomic number ratio of Na 2+x (VOPO4)2F x ·yH2O.

[0030] 2) The raw materials meeting the above ratio are placed in a high-speed homogenizing mill, and the speed and reaction time of the high-speed homogenizing mill are adjusted to realize the process of "fast nucleation + controlled crystallization growth". Specifically, the fast nucleation process: the speed of the high-speed homogenizing mill is 1000-5000 rpm, and the forward or reverse rotation is at least 10 min; the controlled crystallization growth process: the speed of the high-speed homogenizing mill is 300-1000 rpm, and the forward rotation and reverse rotation are alternately performed for 1-5 times, each for at least 15 min; after the reaction, the target product sodium vanadium phosphate is obtained without the need for subsequent washing and drying.

[0031] The high-speed homogenizing mill includes a Chinese herbal medicine grinder, a colloid mill, a planetary ball mill and the like. The switching time between each forward rotation and reverse rotation is at least 10 min.

[0032] The preparation method of the sodium vanadium phosphate material avoids the problems of solvent discharge and waste liquid treatment in the conventional preparation process, realizes efficient utilization of raw materials and extremely high atom utilization rate, and realizes green preparation.

[0033] The preparation method of the sodium vanadium phosphate material can effectively control the particle size of the sodium vanadium phosphate particles, and realizes controllable preparation of the average particle size in nanometer level. The prepared sodium vanadium phosphate is used as an electrode material, has good electrochemical performance, and can be used as an electrode material of lithium, sodium, potassium and other alkali metal secondary batteries.

[0034] In order to more directly reflect the present application, the embodiments of the present application are further described in combination with examples. The following examples are only preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art can obtain the technical solutions within the technical range disclosed by the present application, including simple changes or equivalent replacements, which are within the protection scope of the present application.

[0035] [Example 1]

[0036] 0.2 mol of VO2, 0.1 mol of NaF and 0.2 mol of NaH2PO4 are weighed, and the atomic ratio is Na:V:P:F:H:O = 3:2:2:1:4:12. The three raw materials are added to a Chinese herbal medicine grinder. Under the condition of 3000 rpm, the grinding is carried out for 10 min in the forward direction, and then the speed is adjusted to 600 rpm, and the grinding is carried out for 15 min in the forward direction and the reverse direction alternately. After the reaction is completed, the steel wire filter screen is used for screening, and the sodium vanadium phosphate material is obtained. The chemical formula of the obtained sodium vanadium phosphate material is Na3(VOPO4)2F·2H2O (equivalent to the case of x = 1 and y = 2 in the chemical formula Na 2+ x(VOPO4)2F x ·yH2O).

[0037] [Example 2]

[0038] 0.1 mol of VO2 and 0.1 mol of NaH2PO4 are weighed, and the atomic ratio is Na:V:P:H:O = 1:1:1:2:6. The three raw materials are added to a colloid mill. Under the condition of 5000 rpm, the grinding is carried out for 10 min in the forward direction, and then the speed is adjusted to 1000 rpm, and the grinding is carried out for 15 min in the forward direction and the reverse direction alternately. After the reaction is completed, the steel wire filter screen is used for screening, and the sodium vanadium phosphate material is obtained. The chemical formula of the obtained sodium vanadium phosphate material is Na2(VOPO4)2·H2O (equivalent to the case of x = 0 and y = 1 in the chemical formula Na 2+ x(VOPO4)2F x ·yH2O), which can be expressed as 2NaVOPO4·H2O, and can be further simplified as NaVOPO4·H2O.

[0039] [Example 3]

[0040] Take 0.2 mol of VOOH, 0.1 mol of NaF and 0.2 mol of Na2HPO4, the atomic ratio is Na:V:P:F:H:O=3:2:2:1:4:12. The three raw materials are added to the planetary ball mill. Under the condition of 1000 rpm, the forward rotation grinding is carried out for 10 min, and then the rotation speed is adjusted to 500 rpm, and the forward and reverse rotation grinding is carried out for 5 times, each time for 15 min. After the reaction is completed, the steel wire screen is used for screening, and the sodium vanadium phosphate material is obtained. The chemical formula of the obtained sodium vanadium phosphate material is Na3(VOPO4)2F·2H2O (equivalent to the chemical formula Na 2+ x(VOPO4)2F x ·yH2O, x=1, y=2).

[0041] Figure 1 is the XRD curve of the sodium vanadium phosphate material prepared in Example 1; it can be seen from Figure 1 that the characteristic diffraction peaks of the curve correspond to the peak positions of the standard card PDF#01-076-3645 one by one, which shows that the prepared sample product is sodium vanadium phosphate (Na3(VOPO4)2F·2H2O), and the intensity of the XRD characteristic diffraction peak is strong, which shows that the obtained sample product has good crystallinity.

[0042] Figure 2 is the particle size distribution diagram of the sodium vanadium phosphate material prepared in Example 1; it can be seen from Figure 2 that the particle size of the prepared sodium vanadium phosphate is small (below 100 nm), and the particle size distribution is relatively concentrated.

[0043] Figure 3 is the SEM diagram of the sodium vanadium phosphate material prepared in Example 2; it can be seen from Figure 3 that the micro-morphology of the prepared sodium vanadium phosphate is nanoparticle, and the particle size distribution of the nanoparticles is relatively concentrated, mainly around 100 nm.

[0044] Figure 4 is the cyclic voltammetry (CV) diagram of the sodium vanadium phosphate material prepared in Example 2; it can be seen from Figure 4 that the prepared sodium vanadium phosphate has reversible redox characteristic peaks, showing good sodium ion intercalation and deintercalation performance, and can be used as sodium ion secondary battery electrode material.

[0045] Figure 5 is the constant current charge-discharge curve of the sodium vanadium phosphate material prepared in Example 3; it can be seen from Figure 5 that under the condition of 0.1C charge-discharge current density, the specific capacity of the prepared sodium vanadium phosphate is 103.1 mAh / g, showing good discharge specific capacity.

[0046] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can make equivalent replacement or change according to the technical scheme and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A method for preparing a nanosized sodium vanadium phosphate material, characterized in that, Sodium vanadyl phosphate is in the form of nanoparticles and has the chemical formula Na2+x(VOPO4)2F x • yH2O, where x = 0 or 1 and y = 0-2; the preparation steps are as follows: 1) The raw materials are weighed according to the ratio, and the raw materials are composed of tetravalent vanadium, sodium phosphate salt and sodium fluoride, or the raw materials are composed of tetravalent vanadium and sodium phosphate salt, and the raw material ratio meets the atomic ratio of Na2+x(VOPO4)2F x ·yH2O; 2) Put the raw materials into a high-speed homogenizing mill, adjust the rotation speed and reaction time of the high-speed homogenizing mill, and sequentially complete the rapid nucleation process and the controlled crystallization growth process; in the rapid nucleation process, the rotation speed of the high-speed homogenizing mill is controlled to be 1000-5000 rpm, and the rotation direction is forward or reverse for at least 10 min; in the controlled crystallization growth process, the rotation speed of the high-speed homogenizing mill is controlled to be 300-1000 rpm, and the rotation direction is alternately forward and reverse for 1-5 times, each for at least 15 min; the target product is obtained after the reaction. 2.The method for preparing nano-sodium vanadium phosphate material according to claim 1, characterized in that, In the step 1), the tetravalent vanadium is one or both of VO2 and VOOH. 3.The method of claim 1, wherein the method further comprises: adding a sodium phosphate solution to the sodium vanadate solution to prepare a sodium vanadate nanoparticle solution; and adding a sodium hydroxide solution to the sodium vanadate nanoparticle solution to prepare the sodium vanadate nanoparticle material. In the step 1), the sodium phosphate salt is one or both of Na2HPO4 and NaH2PO4. 4.The method for preparing nano-sodium vanadium phosphate material according to claim 1, characterized in that, In the step 2), the high-speed homogenizing mill is a Chinese herbal medicine grinder, a colloid mill or a planetary ball mill.

5. The method for preparing nano-sodium vanadium phosphate material according to claim 1, characterized in that, In the step 2), the switching between the forward rotation and the reverse rotation is at least interval of 10 min. 6.The method for preparing nano-sodium vanadium phosphate material according to claim 1, characterized in that, The particle size of the prepared sodium vanadium phosphate is ≤100 nm.

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