Sodium vanadium phosphate prepared based on Joule heating and preparation method and application thereof

Abstract

The invention belongs to the technical field of synthesis of a positive electrode material of a sodium ion battery technology, and provides sodium vanadium phosphate prepared based on Joule heating as well as a preparation method and application of the sodium vanadium phosphate. The preparation method comprises the following steps: S1, uniformly mixing a vanadium source, a phosphorus source, a sodium source and a carbon source in a ball milling manner to obtain a precursor; and S2, loading the precursor in a graphite boat, and carrying out Joule heating treatment under inert gas or vacuum protection to obtain the uniform and compact carbon-coated sodium vanadium phosphate. The sodium vanadium phosphate is prepared through quick heating of Joule heat, the forming time difference of a carbon layer and a main body material can be effectively shortened, a uniform and compact carbon coating layer is obtained, and then the rate capability and the cycling stability of the sodium vanadium phosphate are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of synthesis of positive electrode materials for sodium ion battery technology, and in particular relates to sodium vanadium phosphate prepared based on Joule heating, and a preparation method and application thereof. Background Art

[0002] The excessive use of fossil fuels has led to serious environmental pollution, prompting people to turn to renewable energy sources such as solar, wind and tidal energy. However, due to the intermittent characteristics of these energy sources, effective energy storage systems (ESSs) are needed to ensure the continuity and stability of power supply. Among the many energy storage technologies, secondary batteries are favored for their flexibility, efficient energy conversion and simple maintenance. In particular, sodium-ion batteries are considered to be more suitable as large-scale energy storage solutions than lithium-ion batteries due to the abundance of sodium resources. Polyanionic materials, such as NASICON (fast ion conductor of sodium) compounds, have become a hot topic in the research of positive electrode materials for sodium-ion batteries due to their high operating voltage, stable structure and excellent safety. Recent studies on sodium-ion batteries (SIBs) have confirmed that Na3V2(PO4)3 (NVP) as a positive electrode material has a theoretical capacity of about 117 mAh / g and an operating voltage of about 3.3 V, showing excellent rate performance and supporting high-power fast charging and discharging. It also shows advantages in cycle stability and safety. Therefore, NVP cathode is very suitable for fast and frequent charging and discharging during peak load transfer in grid-scale energy storage systems.

[0003] The existing preparation technology of sodium vanadium phosphate has the problems of complicated procedures, high energy consumption, uneven morphology of the prepared sodium vanadium phosphate, different particle sizes, and poor carbon coating effect, which leads to poor electrical properties of the sodium vanadium phosphate positive electrode material. Summary of the invention

[0004] In order to solve the technical problems existing in the preparation technology of sodium vanadium phosphate, such as complicated procedures, high energy consumption, uneven morphology of the prepared sodium vanadium phosphate, different particle sizes, poor carbon coating effect, and poor electrical properties of the sodium vanadium phosphate positive electrode material, the present invention provides sodium vanadium phosphate prepared based on Joule heating, and a preparation method and application thereof.

[0005] The present invention provides a method for preparing sodium vanadium phosphate based on Joule heating, and the preparation method comprises the following steps:

[0006] S1. Mixing a vanadium source, a phosphorus source, a sodium source and a carbon source uniformly by ball milling to obtain a precursor;

[0007] S2. The precursor is placed in a graphite boat and subjected to Joule heating treatment under inert gas or vacuum protection to obtain sodium vanadium phosphate with a uniform and dense carbon coating layer.

[0008] Furthermore, in step S1, the molar ratio of the vanadium source, the phosphorus source, the sodium source and the carbon source is 2:3:3:1.

[0009] Furthermore, in step S1, the vanadium source is one or more of ammonium metavanadate, vanadium oxyhydroxide, sodium metavanadate, vanadium pentoxide, vanadium dioxide, and vanadium trioxide; and the carbon source is one or more of glucose, fructose, sucrose, starch, and cellulose.

[0010] Furthermore, in step S1, the sodium source is one or more of sodium carbonate, sodium hydroxide, sodium citrate, sodium acetate, sodium oxalate, and sodium dihydrogen phosphate.

[0011] Furthermore, the phosphorus source in step S1 is one or more of ammonium dihydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, diammonium hydrogen phosphate, phosphoric acid, and sodium phosphate.

[0012] Furthermore, the Joule heating treatment in step S2 is as follows: time 10ms-300s, voltage 20-40V, current 50-500A, temperature 700-1000°C.

[0013] Furthermore, the Joule heating treatment in step S2 is as follows: time 10s, voltage 30V, current 100A, temperature 800°C.

[0014] Furthermore, in the step S2, the precursor is dried before the Joule heating treatment, and the drying temperature is 80° C. and the time is 2-10 hours.

[0015] The present invention also includes sodium vanadium phosphate prepared by the above preparation method.

[0016] The present invention also includes a sodium ion battery, wherein the positive electrode of the sodium ion battery includes the above-mentioned sodium vanadium phosphate.

[0017] The present invention has found through a large amount of experimental data that there is a difference (temperature difference) between the temperature for forming the carbon layer (carbonization temperature) and the temperature for forming the main material (phase crystallization temperature), resulting in the formation of the carbon layer and the main material in sequence (time difference), and part of the carbon will exist in the product in a free form, resulting in poor carbon coating effect and poor electrical properties of the sodium vanadium phosphate positive electrode material. Shortening or even eliminating the temperature difference and time difference can theoretically overcome the above shortcomings and obtain sodium vanadium phosphate with excellent coating effect. The present invention prepares sodium vanadium phosphate by rapid heating with Joule heat, which can effectively shorten the time difference between the formation of the carbon layer and the main material, obtain a uniform and dense carbon coating layer, and thus improve the rate performance and cycle stability of sodium vanadium phosphate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The SEM images of the sodium vanadium phosphate samples prepared in Example 1 and Comparative Example 1 of the present invention;

[0019] Figure 2 TEM images comparing the carbon layers of the sodium vanadium phosphate materials prepared in Example 1 of the present invention and Comparative Example 1.

[0020] Figure 3 A comparison chart of charge and discharge curves of batteries made of sodium vanadium phosphate materials prepared in Example 1 of the present invention and Comparative Example 1 at 0.1C;

[0021] Figure 4 This is a comparison chart of the discharge specific capacities of batteries made of sodium vanadium phosphate materials prepared in Example 1 of the present invention and Comparative Example 1 at 0.3C, 1C, 3C, 5C, 10C, and 15C. DETAILED DESCRIPTION

[0022] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0023] Example 1

[0024] A method for preparing sodium vanadium phosphate based on Joule heating, the method comprising the following steps:

[0025] S1. Vanadyl hydroxide, sodium dihydrogen phosphate, sodium hydroxide and glucose are mixed uniformly by ball milling to obtain a precursor, wherein the molar ratio of the vanadium source, the phosphorus source, the sodium source and the carbon source is 2:3:3:1;

[0026] S2. The precursor is placed in a graphite boat, first dried at 80°C for 4 hours, and then subjected to Joule heating treatment under inert gas protection to obtain a uniform and dense carbon coating layer of sodium vanadium phosphate. The Joule heating treatment is: time 10s, voltage 30V, current 100A, temperature 800°C.

[0027] This embodiment also includes sodium vanadium phosphate prepared by the above preparation method.

[0028] This embodiment also includes a sodium ion battery, wherein the positive electrode of the sodium ion battery includes the above-mentioned sodium vanadium phosphate.

[0029] Example 2

[0030] A method for preparing sodium vanadium phosphate based on Joule heating, the method comprising the following steps:

[0031] S1. Mix ammonium metavanadate, ammonium dihydrogen phosphate, sodium carbonate and fructose by ball milling to obtain a precursor, wherein the molar ratio of the vanadium source, the phosphorus source, the sodium source and the carbon source is 2:3:3:1;

[0032] S2. The precursor is placed in a graphite boat, first dried at 80°C for 2 hours, and then subjected to Joule heating treatment under inert gas protection to obtain a uniform and dense carbon coating layer of sodium vanadium phosphate. The Joule heating treatment is: time 10ms, voltage 40V, current 500A, temperature 1000°C.

[0033] This embodiment also includes sodium vanadium phosphate prepared by the above preparation method.

[0034] This embodiment also includes a sodium ion battery, wherein the positive electrode of the sodium ion battery includes the above-mentioned sodium vanadium phosphate.

[0035] Example 3

[0036] A method for preparing sodium vanadium phosphate based on Joule heating, the method comprising the following steps:

[0037] S1. Sodium metavanadate, disodium hydrogen phosphate, sodium citrate and sucrose are mixed evenly by ball milling to obtain a precursor, wherein the molar ratio of the vanadium source, the phosphorus source, the sodium source and the carbon source is 2:3:3:1;

[0038] S2. The precursor is placed in a graphite boat, first dried at 80°C for 10 hours, and then subjected to Joule heating treatment under inert gas protection to obtain a uniform and dense carbon coating layer of sodium vanadium phosphate. The Joule heating treatment is: time 300s, voltage 20V, current 50A, temperature 700°C.

[0039] This embodiment also includes sodium vanadium phosphate prepared by the above preparation method.

[0040] This embodiment also includes a sodium ion battery, wherein the positive electrode of the sodium ion battery includes the above-mentioned sodium vanadium phosphate.

[0041] Example 4

[0042] A method for preparing sodium vanadium phosphate based on Joule heating, the method comprising the following steps:

[0043] S1. Vanadium pentoxide, diammonium hydrogen phosphate, sodium acetate and starch are mixed uniformly by ball milling to obtain a precursor, wherein the molar ratio of the vanadium source, the phosphorus source, the sodium source and the carbon source is 2:3:3:1;

[0044] S2. The precursor is placed in a graphite boat, first dried at 80°C for 5 hours, and then subjected to Joule heating treatment under inert gas protection to obtain a uniform and dense carbon coating layer of sodium vanadium phosphate. The Joule heating treatment is: time 150s, voltage 30V, current 250A, temperature 800°C.

[0045] This embodiment also includes sodium vanadium phosphate prepared by the above preparation method.

[0046] This embodiment also includes a sodium ion battery, wherein the positive electrode of the sodium ion battery includes the above-mentioned sodium vanadium phosphate.

[0047] Example 5

[0048] A method for preparing sodium vanadium phosphate based on Joule heating, the method comprising the following steps:

[0049] S1. Vanadium dioxide, phosphoric acid, sodium oxalate and cellulose are mixed uniformly by ball milling to obtain a precursor, wherein the molar ratio of the vanadium source, the phosphorus source, the sodium source and the carbon source is 2:3:3:1;

[0050] S2. The precursor is placed in a graphite boat, first dried at 80°C for 8 hours, and then subjected to Joule heating treatment under inert gas protection to obtain a uniform and dense carbon coating layer of sodium vanadium phosphate. The Joule heating treatment is: time 150s, voltage 30V, current 250A, temperature 800°C.

[0051] This embodiment also includes sodium vanadium phosphate prepared by the above preparation method.

[0052] This embodiment also includes a sodium ion battery, wherein the positive electrode of the sodium ion battery includes the above-mentioned sodium vanadium phosphate.

[0053] Example 6

[0054] A method for preparing sodium vanadium phosphate based on Joule heating, the method comprising the following steps:

[0055] S1. Vanadium trioxide, sodium phosphate, sodium oxalate and cellulose are mixed evenly by ball milling to obtain a precursor, wherein the molar ratio of the vanadium source, the phosphorus source, the sodium source and the carbon source is 2:3:3:1;

[0056] S2. The precursor is placed in a graphite boat, first dried at 80°C for 6 hours, and then subjected to Joule heating treatment under inert gas protection to obtain a uniform and dense carbon coating layer of sodium vanadium phosphate. The Joule heating treatment is: time 50s, voltage 35V, current 200A, temperature 850°C.

[0057] This embodiment also includes sodium vanadium phosphate prepared by the above preparation method.

[0058] This embodiment also includes a sodium ion battery, wherein the positive electrode of the sodium ion battery includes the above-mentioned sodium vanadium phosphate.

[0059] Example 7

[0060] A method for preparing sodium vanadium phosphate based on Joule heating, the method comprising the following steps:

[0061] S1. Vanadyl hydroxide, sodium dihydrogen phosphate, sodium hydroxide and glucose are mixed uniformly by ball milling to obtain a precursor, wherein the molar ratio of the vanadium source, the phosphorus source, the sodium source and the carbon source is 2:3:3:1;

[0062] S2. The precursor is placed in a graphite boat, first dried at 80°C for 3 hours, and then subjected to Joule heating treatment under inert gas protection to obtain a uniform and dense carbon coating layer of sodium vanadium phosphate. The Joule heating treatment is: time 10s, voltage 38V, current 400A, temperature 950°C.

[0063] This embodiment also includes sodium vanadium phosphate prepared by the above preparation method.

[0064] This embodiment also includes a sodium ion battery, wherein the positive electrode of the sodium ion battery includes the above-mentioned sodium vanadium phosphate.

[0065] Comparative Example 1

[0066] A preparation method of sodium vanadium phosphate based on heating in a tubular furnace, the preparation method comprising the following steps:

[0067] S1. Vanadyl hydroxide, sodium dihydrogen phosphate, sodium hydroxide and glucose are mixed uniformly by ball milling to obtain a precursor, wherein the molar ratio of the vanadium source, the phosphorus source, the sodium source and the carbon source is 2:3:3:1;

[0068] S2. The precursor is placed in a tube furnace for heating. The heating conditions are: heating from room temperature to 800°C at a heating rate of 5°C / min, then keeping at 800°C for 5 minutes, and then cooling to room temperature at a cooling rate of 5°C / min to obtain a sodium vanadium phosphate coating.

[0069] This comparative example also includes sodium vanadium phosphate prepared by the above preparation method.

[0070] This comparative example also includes a sodium ion battery, wherein the positive electrode of the sodium ion battery includes the above-mentioned sodium vanadium phosphate.

[0071] Experimental results and analysis

[0072] The performance test indicators of the batteries made of sodium vanadium phosphate materials prepared in Examples 1-7 and Comparative Examples are as follows:

[0073] Capacity retention rate after 100 cycles at 1C = capacity after 100 cycles / theoretical capacity (117.6 mAh / g)

[0074]

[0075] Figure 1 for Figure 1 The SEM images of the sodium vanadium phosphate samples prepared in Example 1 and Comparative Example 1 of the present invention show that there are differences in the morphology of the sodium vanadium phosphate samples prepared in Example 1 and Comparative Example 1. The surface coating layer of the sample obtained by Joule heating is smooth and uniform, while the carbon layer on the surface of the tube furnace sample is rough and uneven, and the detached carbon layer can be seen where the arrow points.

[0076] Figure 2 This is a comparative TEM image of the carbon layer of the sodium vanadium phosphate material prepared in Example 1 of the present invention and Comparative Example 1. The dotted line in the figure is the carbon coating layer. It can be seen that the carbon layer coated on the NVP particles obtained by Joule heating is denser and more uniform than the sample particles obtained in a tubular furnace.

[0077] Figure 3 This is a comparison chart of the charge and discharge curves of batteries made of sodium vanadium phosphate materials prepared in Example 1 of the present invention and in Comparative Example 1 at 0.1C; it can be seen that at a slower charge and discharge speed, the charge and discharge specific capacities of the two are close, which indicates that the difference in the coated carbon layer will not affect the capacity of sodium vanadium phosphate at a low rate.

[0078] Figure 4 The figure is a comparison chart of the discharge specific capacity of batteries made of sodium vanadium phosphate materials prepared in Example 1 of the present invention and Comparative Example 1 at 0.3C, 1C, 3C, 5C, 10C and 15C; the results show that the rate performance of Example 1 is significantly better than that of the comparative example, and the greater the rate, the more obvious the advantage of the embodiment.

[0079] In summary, the present invention prepares sodium vanadium phosphate by rapid heating using Joule heat to obtain a uniform and dense carbon coating layer, thereby improving the rate performance and cycle stability of sodium vanadium phosphate, effectively reducing capacity attenuation, and extending the life of the battery.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing sodium vanadium phosphate based on Joule heating, the preparation method comprising the following steps: S1. Mixing a vanadium source, a phosphorus source, a sodium source and a carbon source uniformly by ball milling to obtain a precursor; S2. The precursor is placed in a graphite boat and subjected to Joule heating treatment under inert gas or vacuum protection to obtain sodium vanadium phosphate with a uniform and dense carbon coating layer.

2. The method for preparing sodium vanadium phosphate based on Joule heating according to claim 1, characterized in that: In step S1, the molar ratio of the vanadium source, the phosphorus source, the sodium source and the carbon source is 2:3:3:

1.

3. The method for preparing sodium vanadium phosphate based on Joule heating according to claim 1, characterized in that: In step S1, the vanadium source is one or more of ammonium metavanadate, vanadyl hydroxide, sodium metavanadate, vanadium pentoxide, vanadium dioxide, and vanadium trioxide; and the carbon source is one or more of glucose, fructose, sucrose, starch, and cellulose.

4. The method for preparing sodium vanadium phosphate based on Joule heating according to claim 1, characterized in that: In step S1, the sodium source is one or more of sodium carbonate, sodium hydroxide, sodium citrate, sodium acetate, sodium oxalate, and sodium dihydrogen phosphate.

5. The method for preparing sodium vanadium phosphate based on Joule heating according to claim 1, characterized in that: In the step S1, the phosphorus source is one or more of diammonium dihydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, diammonium hydrogen phosphate, phosphoric acid, and sodium phosphate.

6. The method for preparing sodium vanadium phosphate based on Joule heating according to claim 1, characterized in that: The Joule heating treatment in step S2 is as follows: time 10ms-300s, voltage 20-40V, current 50-500A, temperature 700-1000°C.

7. The method for preparing sodium vanadium phosphate based on Joule heating according to claim 6, characterized in that: The Joule heating treatment in step S2 is as follows: time 10s, voltage 30V, current 100A, temperature 800°C.

8. The method for preparing sodium vanadium phosphate based on Joule heating according to claim 7, characterized in that: In the step S2, the precursor is dried before the Joule heating treatment, and the drying temperature is 80° C. and the drying time is 2-10 hours.

9. A sodium vanadium phosphate, characterized in that: The sodium vanadium phosphate is prepared by any one of the preparation methods in claims 1 to 8.

10. A sodium ion battery, characterized in that: The positive electrode of the sodium ion battery comprises the sodium vanadium phosphate according to claim 9.

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