阅读说明：本技术 一种碳包覆磷酸钛钠复合材料的制备方法 (Preparation method of carbon-coated sodium titanium phosphate composite material ) 是由 鲍克燕 张佳其 毛武涛 钱逸泰 于 2021-08-27 设计创作，主要内容包括：本发明公开一种碳包覆磷酸钛钠复合材料的制备方法,该方法是：以硫酸氧钛作为钛源,以磷酸作为磷源,然后将所述硫酸氧钛和所述磷酸与钠源和碳源混合,经共沉淀、湿法混合、喷雾干燥和高温煅烧,制得所述碳包覆磷酸钛钠复合材料。本发明提供了一种以资源丰富的硫酸氧钛和磷酸作为原料,可以规模化制备碳包覆磷酸钛钠复合材料的技术方案。在本发明的技术方案中,不仅原料来源丰富,价格低廉,而且副产物少、无有害气体排环境友好。将本发明制备的碳包覆磷酸钛钠复合材料用作钠离子电池负极材料,可以表现出优异的比容量、倍率、长循环等电化学性能。(The invention discloses a preparation method of a carbon-coated sodium titanium phosphate composite material, which comprises the following steps: and (2) taking titanyl sulfate as a titanium source and phosphoric acid as a phosphorus source, then mixing the titanyl sulfate and the phosphoric acid with a sodium source and a carbon source, and preparing the carbon-coated titanium sodium phosphate composite material through coprecipitation, wet mixing, spray drying and high-temperature calcination. The invention provides a technical scheme for preparing a carbon-coated titanium sodium phosphate composite material in a large scale by using titanyl sulfate and phosphoric acid which are rich in resources as raw materials. According to the technical scheme, the raw materials are rich in source and low in price, byproducts are few, and no harmful gas is generated, so that the environment is protected. The carbon-coated sodium titanium phosphate composite material prepared by the invention can be used as a sodium ion battery cathode material and can show excellent electrochemical properties such as specific capacity, multiplying power, long cycle and the like.)

1. A preparation method of a carbon-coated sodium titanium phosphate composite material is characterized by comprising the following steps: and (2) taking titanyl sulfate as a titanium source and phosphoric acid as a phosphorus source, then mixing the titanyl sulfate and the phosphoric acid with a sodium source and a carbon source, and preparing the carbon-coated titanium sodium phosphate composite material through coprecipitation, wet mixing, spray drying and high-temperature calcination.

2. The method for preparing the carbon-coated sodium titanium phosphate composite material according to claim 1, wherein the method comprises the following steps:

(1) preparing a homogeneous phase aqueous solution of titanyl sulfate;

(2) preparing a phosphoric acid aqueous solution;

(3) mixing the titanyl sulfate homogeneous phase aqueous solution and the phosphoric acid aqueous solution for reaction, then standing for aging, and carrying out vacuum filtration to obtain a filter cake;

(4) washing the filter cake, and putting the filter cake, water, the sodium source and the carbon source into a reaction kettle for reaction to obtain reaction slurry;

(5) spray drying the reaction slurry to obtain a powdery precursor;

(6) and calcining the powdery precursor at a high temperature in an inert atmosphere, and naturally cooling to obtain the carbon-coated sodium titanium phosphate composite material.

3. The preparation method of the carbon-coated sodium titanium phosphate composite material according to claim 2, wherein the step (1) is carried out by preparing 0.5-2mol/L homogeneous aqueous solution of titanyl sulfate; and (2) preparing 0.5-4mol/L phosphoric acid aqueous solution.

4. The preparation method of the carbon-coated sodium titanium phosphate composite material according to claim 2, wherein in the step (3), the homogeneous titanyl sulfate aqueous solution and the phosphoric acid aqueous solution are simultaneously added into the reaction kettle at a constant speed, so that the two solutions are simultaneously added, the stirring reaction is carried out for 0.5 to 3 hours, the mixture is kept stand and aged for 0.5 to 24 hours after the reaction, and then the mixture is subjected to vacuum filtration to obtain a filter cake; the volume ratio of the titanyl sulfate homogeneous phase aqueous solution to the phosphoric acid aqueous solution is (1-2): 1.

5. the preparation method of the carbon-coated sodium titanium phosphate composite material as claimed in claim 2, wherein in the step (4), the filter cake is washed by pure water, and then put into a reaction kettle together with water, a sodium source and a carbon source to be stirred and reacted for 0.5-5 hours, so as to obtain a reaction slurry with a solid content of 15-55%.

6. The method for preparing the carbon-coated sodium titanium phosphate composite material as claimed in claim 2, wherein the step (5) comprises spray drying the reaction slurry, controlling the temperature of the air inlet at 170-225 ℃ and the temperature of the air outlet at 75-115 ℃ to obtain the powdery precursor.

7. The preparation method of the carbon-coated sodium titanium phosphate composite material according to claim 2, wherein in the step (6), the powdery precursor is subjected to heating calcination in an inert atmosphere, and the carbon-coated sodium titanium phosphate composite material is obtained after natural cooling; the heating rate is 5-20 ℃/min, and the temperature is heated to 1000 ℃ for 700-plus-energy and then the heat is preserved and calcined for 120-plus-energy 600 minutes.

8. The method for preparing the carbon-coated sodium titanium phosphate composite material according to claim 1, wherein the method comprises the following steps:

(1) preparing a homogeneous phase aqueous solution of titanyl sulfate;

(2) preparing a phosphoric acid aqueous solution;

(3) mixing the titanyl sulfate homogeneous phase aqueous solution and the phosphoric acid aqueous solution for reaction, then standing for aging, and carrying out vacuum filtration to obtain a filter cake;

(4) washing the filter cake, putting the washed filter cake, water and the sodium source into a hydrothermal reaction kettle for reaction, cooling after the reaction, filtering and washing to obtain pure-phase sodium titanium phosphate;

(5) adding the sodium titanium phosphate and the carbon source into a reaction kettle, and stirring for reaction to obtain slurry;

(6) and drying the obtained slurry, calcining in an inert atmosphere, and cooling to obtain the carbon-coated sodium titanium phosphate composite material.

9. The method for preparing the carbon-coated sodium titanium phosphate composite material according to claim 8, wherein the method comprises the following steps:

(1) preparing 0.5-2mol/L homogeneous aqueous solution of titanyl sulfate;

(2) preparing 0.5-4mol/L phosphoric acid aqueous solution;

(3) according to the volume ratio (1-2): 1, mixing and stirring the titanyl sulfate homogeneous phase aqueous solution and the phosphoric acid aqueous solution for reaction for 0.5 to 3 hours, then standing and aging for 0.5 to 24 hours, and carrying out vacuum filtration to obtain a filter cake;

(4) washing the filter cake, putting the washed filter cake, water and the sodium source into a hydrothermal reaction kettle for reaction for 5-24 hours at the temperature of 120-170 ℃, naturally cooling to room temperature after the reaction, filtering and washing to obtain pure-phase sodium titanium phosphate;

(5) adding the sodium titanium phosphate and the carbon source into a reaction kettle, and stirring for reaction to obtain slurry;

(6) and after vacuum drying or spray drying, calcining the slurry in an inert atmosphere at the temperature of 500-700 ℃ for 600 minutes for 120-600 minutes, and cooling to obtain the carbon-coated sodium titanium phosphate composite material.

10. The method for preparing the carbon-coated sodium titanium phosphate composite material as claimed in claim 1, wherein the sodium source is at least one selected from sodium dihydrogen phosphate, sodium hydroxide, sodium citrate, sodium malate, sodium tartrate and sodium ethylene diamine tetracetate; the carbon source is at least one selected from glucose, sucrose, polyvinyl alcohol, dextrin, carbon nano tubes and graphene.

Technical Field

The invention relates to the technical field of nano materials and electrochemistry, in particular to a preparation method of a carbon-coated sodium titanium phosphate composite material.

Background

In the process of changing new and old energy forms, and utilizing and developing new energy, secondary batteries play an important role. At present, although lead-acid batteries and lithium-ion batteries are widely used in the fields of mobile power supplies, energy storage, and the like, new battery systems are rapidly developed due to their respective defects, and new water-based batteries are receiving attention.

Sodium titanium phosphate (NaTi) having NASICON structure₂(PO₄)₃) The polyanion material has the advantages of high ion conductivity and high structural stability due to the three-dimensional polyanion framework. The sodium ion battery or the water system sodium ion battery cathode material can keep stable in the process of charging and discharging, and the volume change is almost zero. However, most of the prior art for preparing sodium titanium phosphate uses nano titanium dioxide, metatitanic acid, or titanate (such as tetraethyl titanate, isopropyl titanate, tetraethyl titanate) as raw material, which is relatively expensive, especially titanate compounds. The titanium ore resources in China are rich, and 98 percent of the titanium ore exists in the form of ilmenite. In the process of preparing titanium dioxide and other products from ilmenite, titanyl sulfate intermediate products are generated, so that if titanyl sulfate is used as a raw material to prepare sodium titanium phosphate, a more extensive technical process can be developed, and the preparation cost can be greatly reduced. At present, the technology for preparing the sodium titanium phosphate by directly taking the titanyl sulfate as the raw material is rarely reported, and the main reason is that the method for preparing the sodium titanium phosphate by directly taking the titanyl sulfate as the raw material not only can generate a large amount of sulfur-containing waste gas, but also can wrap a large amount of sulfur-containing complex products in the product, so that the purity of a sample is poor. In addition, the phosphoric acid has strong acidity, is viscous liquid and is difficult to process into a powdery precursor with strong operability with other raw materials, so that the phosphoric acid is used as the raw material to realize the large-scale preparation of the sodium titanium phosphate, and the sodium titanium phosphate is still preparedThere are a number of technical difficulties.

Disclosure of Invention

The invention aims to provide a novel preparation method of a carbon-coated titanium sodium phosphate composite material, aiming at the problems that the cost of raw materials is high, sulfur-containing waste gas is generated in the process of directly preparing the titanium sodium phosphate by taking titanyl sulfate as the raw material, and more sulfur-containing complex products are easily wrapped in the product, and the like in the existing preparation technology of the titanium sodium phosphate.

The invention is realized by the following technical scheme:

a preparation method of a carbon-coated sodium titanium phosphate composite material is characterized by comprising the following steps: and (2) taking titanyl sulfate as a titanium source and phosphoric acid as a phosphorus source, then mixing the titanyl sulfate and the phosphoric acid with a sodium source and a carbon source, and preparing the carbon-coated titanium sodium phosphate composite material through coprecipitation, wet mixing, spray drying and high-temperature calcination.

The preparation method of the invention takes titanyl sulfate, phosphoric acid, a sodium source and a carbon source as raw materials to prepare the coated sodium titanium phosphate composite material. In the preparation process, the use of the titanyl sulfate can greatly reduce the whole preparation cost, and the process solves the problems that harmful sulfur-containing waste gas is easily generated when the titanyl sulfate is used as a raw material and the obtained product is easily wrapped with a mixed sulfur-containing compound. The product prepared by the method is used as a sodium ion battery cathode material, and can show excellent specific capacity, multiplying power, long cycle and other electrochemical properties.

Further, one of the preparation methods of the carbon-coated sodium titanium phosphate composite material comprises the following steps:

(1) preparing a homogeneous phase aqueous solution of titanyl sulfate;

(2) preparing a phosphoric acid aqueous solution;

(3) mixing the titanyl sulfate homogeneous phase aqueous solution and the phosphoric acid aqueous solution for reaction, then standing for aging, and carrying out vacuum filtration to obtain a filter cake;

(4) washing the filter cake, and putting the filter cake, water, the sodium source and the carbon source into a reaction kettle for reaction to obtain reaction slurry;

(5) spray drying the reaction slurry to obtain a powdery precursor;

(6) and calcining the powdery precursor at a high temperature in an inert atmosphere, and naturally cooling to obtain the carbon-coated sodium titanium phosphate composite material.

Specifically, in the preparation method of the carbon-coated sodium titanium phosphate composite material, a homogeneous phase aqueous solution of titanyl sulfate and an aqueous solution of phosphoric acid are mixed in a coprecipitation reaction kettle for reaction, and after the reaction, the mixture is kept stand for aging and is subjected to vacuum filtration to obtain a filter cake; after the reaction, the sulfur element in the titanyl sulfate remains in solution, and the obtained filter cake does not contain the sulfur element. Therefore, when the filter cake is used for preparing the carbon-coated sodium titanium phosphate composite material by a subsequent process, sulfur-containing waste gas cannot be generated, and the sulfur-containing compound with more impurities in the product cannot be generated.

Further, 0.5-2mol/L of titanyl sulfate homogeneous phase aqueous solution is prepared in the step (1); and (2) preparing 0.5-4mol/L phosphoric acid aqueous solution.

Further, step (3) adding the titanyl sulfate homogeneous phase aqueous solution and the phosphoric acid aqueous solution into a reaction kettle at a constant speed simultaneously, completing the addition of the two solutions simultaneously, stirring for reaction for 0.5-3 hours, standing for aging for 0.5-24 hours after the reaction, and then carrying out vacuum filtration to obtain a filter cake; the volume ratio of the titanyl sulfate homogeneous phase aqueous solution to the phosphoric acid aqueous solution is (1-2): 1.

and (3) further, washing the filter cake with pure water in the step (4), and then putting the filter cake, water, a sodium source and a carbon source into a reaction kettle together to be stirred and reacted for 0.5-5 hours to obtain reaction slurry with the solid content of 15-55%.

Further, the step (5) is to spray dry the reaction slurry, the temperature of the air inlet is controlled to be 170-225 ℃, and the temperature of the air outlet is controlled to be 75-115 ℃, so as to obtain the powdery precursor.

Further, step (6) heating and calcining the powdery precursor in an inert atmosphere, and naturally cooling to obtain the carbon-coated sodium titanium phosphate composite material; the heating rate is 5-20 ℃/min, and the temperature is heated to 1000 ℃ for 700-plus-energy and then the heat is preserved and calcined for 120-plus-energy 600 minutes.

Further, another preparation method of the carbon-coated sodium titanium phosphate composite material comprises the following steps:

(1) preparing a homogeneous phase aqueous solution of titanyl sulfate;

(2) preparing a phosphoric acid aqueous solution;

(3) mixing the titanyl sulfate homogeneous phase aqueous solution and the phosphoric acid aqueous solution for reaction, then standing for aging, and carrying out vacuum filtration to obtain a filter cake;

(4) washing the filter cake, putting the washed filter cake, water and the sodium source into a hydrothermal reaction kettle for reaction, cooling after the reaction, filtering and washing to obtain pure-phase sodium titanium phosphate;

(5) adding the sodium titanium phosphate and the carbon source into a reaction kettle, and stirring for reaction to obtain slurry;

(6) and drying the obtained slurry, calcining in an inert atmosphere, and cooling to obtain the carbon-coated sodium titanium phosphate composite material.

Specifically, in the preparation method, pure-phase sodium titanium phosphate is prepared firstly, and then the prepared sodium titanium phosphate is mixed with a carbon source for carbon coating. Although the preparation cost is slightly increased by the preparation method provided by the invention, the carbon-coated sodium titanium phosphate composite material prepared by the method has more uniform micro-morphology.

Further, the method comprises the following steps:

(1) preparing 0.5-2mol/L homogeneous aqueous solution of titanyl sulfate;

(2) preparing 0.5-4mol/L phosphoric acid aqueous solution;

(3) according to the volume ratio (1-2): 1, mixing and stirring the titanyl sulfate homogeneous phase aqueous solution and the phosphoric acid aqueous solution for reaction for 0.5 to 3 hours, then standing and aging for 0.5 to 24 hours, and carrying out vacuum filtration to obtain a filter cake;

(4) washing the filter cake, putting the washed filter cake, water and the sodium source into a hydrothermal reaction kettle for reaction for 5-24 hours at the temperature of 120-170 ℃, naturally cooling to room temperature after the reaction, filtering and washing to obtain pure-phase sodium titanium phosphate;

(5) adding the sodium titanium phosphate and the carbon source into a reaction kettle, and stirring for reaction to obtain slurry;

(6) and after vacuum drying or spray drying, calcining the slurry in an inert atmosphere at the temperature of 500-700 ℃ for 600 minutes for 120-600 minutes, and cooling to obtain the carbon-coated sodium titanium phosphate composite material.

Further, the sodium source is selected from at least one of sodium dihydrogen phosphate, sodium hydroxide, sodium citrate, sodium malate, sodium tartrate and sodium ethylene diamine tetracetate; the carbon source is at least one selected from glucose, sucrose, polyvinyl alcohol, dextrin, carbon nano tubes and graphene.

The carbon-coated sodium titanium phosphate composite material prepared by the method can be used as a negative electrode material of a sodium ion battery.

The invention has the beneficial effects that:

(1) the invention provides a technical scheme for preparing a carbon-coated titanium sodium phosphate composite material in a large scale by using titanyl sulfate and phosphoric acid which are rich in resources as raw materials. According to the technical scheme, the raw materials are rich in source and low in price, byproducts are few, and no harmful gas is generated, so that the environment is protected.

(2) The carbon-coated sodium titanium phosphate composite material prepared by the invention can be used as a sodium ion battery cathode material and can show excellent electrochemical properties such as specific capacity, multiplying power, long cycle and the like.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is an XRD pattern of the sodium titanium phosphate prepared in example 1 and the carbon-coated sodium titanium phosphate composite prepared in example 2;

fig. 2 is a graph showing the cycle capacity and coulombic efficiency under the condition of a sodium ion battery 5C assembled by the carbon-coated sodium titanium phosphate composite prepared in example 1.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

A preparation method of a carbon-coated sodium titanium phosphate composite material comprises the following steps:

(1) 40 liters of titanyl sulfate homogeneous phase aqueous solution with the concentration of 1mol/L is prepared;

(2) preparing 20 liters of 2mol/L phosphoric acid aqueous solution;

(3) simultaneously adding 40 liters of the prepared titanyl sulfate homogeneous phase aqueous solution and 20 liters of phosphoric acid aqueous solution into a coprecipitation reaction kettle at a constant speed by using a peristaltic pump, continuously stirring for reaction for 1 hour after 2 hours of feeding, then standing for aging for 2 hours, and carrying out vacuum filtration to obtain a filter cake;

(4) washing the obtained filter cake with pure water, transferring the filter cake to a hydrothermal reaction kettle, adding 20 liters of water and 3120g of sodium dihydrogen phosphate, uniformly stirring, heating to 150 ℃ for reaction for 6 hours, naturally cooling to room temperature after the reaction, filtering, and washing to obtain pure-phase sodium titanium phosphate (NTP);

(5) adding 5 kg of the obtained sodium titanium phosphate into a reaction kettle, then adding 10 kg of water, then adding 500g of glucose, 100g of polyvinyl alcohol and 100g of carbon nano tube dispersion liquid with the mass fraction of 10%, and stirring and reacting for 2 hours to obtain slurry;

(6) and (3) spray-drying the obtained slurry (controlling the temperature of an air inlet to be 200 ℃ and the temperature of an air outlet to be 100 ℃) to obtain a precursor, heating the precursor to 550 ℃ under the protection of nitrogen, calcining for 180 minutes, and naturally cooling to room temperature to obtain the carbon-coated titanium sodium phosphate composite material.

Example 2

A preparation method of a carbon-coated sodium titanium phosphate composite material comprises the following steps:

(1) 40 liters of titanyl sulfate homogeneous phase aqueous solution with the concentration of 1mol/L is prepared;

(2) preparing 20 liters of 2mol/L phosphoric acid aqueous solution;

(3) simultaneously adding 40 liters of the prepared titanyl sulfate homogeneous phase aqueous solution and 20 liters of phosphoric acid aqueous solution into a coprecipitation reaction kettle at a constant speed by using a peristaltic pump, continuously stirring for reaction for 1 hour after 2 hours of feeding, then standing for aging for 2 hours, and carrying out vacuum filtration to obtain a filter cake;

(4) washing the filter cake with pure water, transferring the filter cake to a hydrothermal reaction kettle, adding 20 liters of water, 3120g of sodium dihydrogen phosphate, 500g of glucose, 100g of polyvinyl alcohol and 100g of carbon nano tube dispersion liquid with the mass fraction of 10%, and stirring for reaction for 2 hours to obtain reaction slurry;

(5) spray-drying the obtained reaction slurry, and controlling the temperature of an air inlet to be 200 ℃ and the temperature of an air outlet to be 100 ℃ to obtain a powdery precursor;

(6) and heating the obtained powdery precursor to 550 ℃ under the protection of nitrogen, calcining for 180 minutes, and naturally cooling to room temperature to obtain the carbon-coated sodium titanium phosphate composite material (NTP @ C).

The two methods provided by the invention are respectively selected to prepare the carbon-coated sodium titanium phosphate composite material in the above embodiment 1 and embodiment 2.

Example 3

Example 3 differs from example 1 in the carbon source added and the remaining preparation conditions are the same; wherein the carbon source added in example 3 was 500g of glucose, 100g of polyvinyl alcohol and 200g of a 5% by mass graphene dispersion.

Example 4

A preparation method of a carbon-coated sodium titanium phosphate composite material comprises the following steps:

(1) 20 liters of titanyl sulfate homogeneous phase aqueous solution with the concentration of 1mol/L is prepared;

(2) preparing 15 liters of 2mol/L phosphoric acid aqueous solution;

(3) simultaneously adding the prepared 20 liters of titanyl sulfate homogeneous phase aqueous solution and 15 liters of phosphoric acid aqueous solution into a coprecipitation reaction kettle at a constant speed by using a peristaltic pump, continuously stirring for reaction for 1 hour after 2 hours of feeding, then standing for aging for 2 hours, and carrying out vacuum filtration to obtain a filter cake;

(4) washing the filter cake with pure water, transferring the filter cake to a hydrothermal reaction kettle, adding 10 liters of water, 860g of sodium citrate and 200g of glucose, and stirring for reaction for 3 hours to obtain reaction slurry;

(5) spray-drying the obtained reaction slurry, and controlling the temperature of an air inlet to be 200 ℃ and the temperature of an air outlet to be 95 ℃ to obtain a powdery precursor;

(6) and heating the obtained powdery precursor to 350 ℃ at the speed of 5 ℃/min under the protection of nitrogen, calcining for 120 minutes, heating to 800 ℃ at the speed of 10 ℃/min, calcining for 240 minutes, and naturally cooling to room temperature to obtain the carbon-coated sodium titanium phosphate composite material.

Example 5

A preparation method of a carbon-coated sodium titanium phosphate composite material comprises the following steps:

(1) 20 liters of titanyl sulfate homogeneous phase aqueous solution with the concentration of 1mol/L is prepared;

(2) 10 liters of 2mol/L phosphoric acid aqueous solution is prepared;

(3) simultaneously adding the prepared 20 liters of titanyl sulfate homogeneous phase aqueous solution and 10 liters of phosphoric acid aqueous solution into a coprecipitation reaction kettle at a constant speed by using a peristaltic pump, continuously stirring for reaction for 1 hour after 2 hours of feeding, then standing for aging for 2 hours, and carrying out vacuum filtration to obtain a filter cake;

(4) washing the filter cake with pure water, transferring the filter cake to a hydrothermal reaction kettle, adding 10 liters of water, 1560g of sodium dihydrogen phosphate and 500g of glucose, and stirring for reaction for 3 hours to obtain reaction slurry;

(5) spray-drying the obtained reaction slurry, and controlling the temperature of an air inlet to be 200 ℃ and the temperature of an air outlet to be 95 ℃ to obtain a powdery precursor;

(6) and heating the obtained powdery precursor to 350 ℃ at the speed of 5 ℃/min under the protection of nitrogen, calcining for 120 minutes, heating to 800 ℃ at the speed of 10 ℃/min, calcining for 240 minutes, and naturally cooling to room temperature to obtain the carbon-coated sodium titanium phosphate composite material.

The above example 5 is different from the above example 4 in the volume of the phosphoric acid solution and the sodium source and the carbon source, and the other preparation conditions are the same.

Example 6

A preparation method of a carbon-coated sodium titanium phosphate composite material comprises the following steps:

(1) 20 liters of titanyl sulfate homogeneous phase aqueous solution with the concentration of 1mol/L is prepared;

(2) 10 liters of 2mol/L phosphoric acid aqueous solution is prepared;

(3) simultaneously adding the prepared 20 liters of titanyl sulfate homogeneous phase aqueous solution and 10 liters of phosphoric acid aqueous solution into a coprecipitation reaction kettle at a constant speed by using a peristaltic pump, continuously stirring for reaction for 1 hour after 2 hours of feeding, then standing for aging for 2 hours, and carrying out vacuum filtration to obtain a filter cake;

(4) washing the filter cake with pure water, transferring the filter cake to a hydrothermal reaction kettle, adding 10 liters of water, 1560g of sodium dihydrogen phosphate, 500g of glucose and 20g of polyvinyl alcohol, and stirring for reaction for 3 hours to obtain reaction slurry;

(5) spray-drying the obtained reaction slurry, and controlling the temperature of an air inlet to be 200 ℃ and the temperature of an air outlet to be 95 ℃ to obtain a powdery precursor;

(6) and heating the obtained powdery precursor to 350 ℃ at the speed of 5 ℃/min under the protection of nitrogen, calcining for 120 minutes, heating to 800 ℃ at the speed of 10 ℃/min, calcining for 240 minutes, and naturally cooling to room temperature to obtain the carbon-coated sodium titanium phosphate composite material.

Example 6 differs from example 5 in the carbon source and the rest of the preparation conditions are the same.

And (3) testing:

x-ray diffraction was performed on the pure-phase sodium titanium phosphate (NTP) prepared in the step (4) of example 1 and the carbon-coated sodium titanium phosphate composite material (NTP @ C) prepared in example 2, and the results are shown in fig. 1, and it can be seen from fig. 1 that the peak patterns of the sodium titanium phosphate material prepared in example 1 and the carbon-coated sodium titanium phosphate composite material prepared in example 2 match the standard pattern, confirming that the materials were successfully prepared.

The application comprises the following steps:

taking the carbon-coated sodium titanium phosphate composite material prepared in the embodiment 1 as a negative electrode material, assembling a sodium ion battery, and testing the electrochemical performance of the assembled sodium ion battery;

the sodium ion battery is assembled by the following steps:

(1) dissolving a carbon-coated sodium titanium phosphate composite material, a conductive agent (Super P) and a binder (polyvinylidene fluoride) in N-methylpyrrolidone to obtain coating slurry; the mass ratio of the carbon-coated sodium titanium phosphate composite material to the conductive agent to the binder is 7: 2: 1;

(2) uniformly coating the obtained coating slurry on a copper foil, then carrying out vacuum drying for 2 hours at the temperature of 110 ℃, and pressing by using a roller press to obtain a negative electrode of the sodium-ion battery; the loading amount on the copper foil is 1mg/cm²；

(3) A CR2032 type coin cell was assembled in an argon-filled glove box with a sodium metal sheet as the counter electrode and glass fibers as the separator, the electrolyte being 1mol/L NaClO dissolved in a mixture of ethylene carbonate and dimethyl carbonate (1: 1, v/v)₄。

The assembled sodium ion battery was tested for electrochemical performance: the Land-2001A (Wuhan, China) is used for carrying out constant current discharge/charge test under the voltage of 1.5-3V, the result is shown in figure 2, and the figure 2 shows that the prepared titanium sodium phosphate cathode material has very high rate performance and ultra-long cycle life, under the condition of 5C rate, after 2000 cycles, the specific capacity still reaches about 57 milliampere per gram, and the capacity retention rate exceeds 90%.

The above-mentioned preferred embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention. Obvious variations or modifications of the present invention are within the scope of the present invention.