Needle-shaped sodium zirconium phosphate sodium supplement as well as preparation method and application thereof

Abstract

The invention relates to a needle-like sodium zirconium phosphate sodium supplement and a preparation method and application thereof. The chemical general formula of the sodium supplementing agent is Na2Zr (PO4) 2. The preparation method comprises the following steps: adding a phosphorus source, a zirconium source and deionized water into a reaction kettle through a multi-step hydrothermal method, reacting at a specific temperature to generate a precursor, adding the precursor, a sodium source and deionized water into the reaction kettle, and reacting at a specific temperature to obtain polygonal flaky sodium zirconium phosphate. And finally, mixing the polygonal flaky sodium zirconium phosphate with the O3 type sodium ion battery positive electrode material in an N-methyl pyrrolidone solution, and reacting and drying in a vacuum drying oven to obtain the needle-like sodium zirconium phosphate. The needle-like sodium zirconium phosphate serving as a sodium supplementing agent of the O3 type sodium ion positive electrode material can enhance the structural stability of the material, improve the diffusion kinetics of sodium ions, improve the conductivity of the material and improve the electrochemical performance. And an effective way is provided for the development of a high-performance sodium ion battery sodium supplementing agent.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and in particular relates to a sodium supplement for sodium ion batteries, a preparation method thereof and an application thereof. Background Art

[0002] With the transformation of the global energy structure and the growing demand for clean energy storage, sodium-ion batteries have shown broad application prospects in the field of large-scale energy storage due to their advantages such as abundant sodium resources and low cost. However, sodium-ion batteries still face some key technical challenges in practical applications, among which the performance optimization of positive electrode materials is one of the core issues. During the charge and discharge cycle of sodium-ion batteries, some sodium ions will be trapped in the lattice defects or surface of the positive electrode material, and cannot be completely reversibly released from the positive electrode material during the subsequent discharge process, resulting in the irreversible loss of some sodium ions, which in turn affects the capacity and cycle life of the battery. In order to compensate for this loss of sodium ions and improve the initial coulombic efficiency and cycle stability of the battery, the research and development of sodium supplements has gradually received widespread attention. Although a sodium supplement composed of sodium carbonate and sodium-ion battery layered oxide can be used to increase the volumetric specific capacity of the sodium supplement, a composite pre-sodium system can be constructed to effectively supplement the irreversible capacity loss of active sodium ions (patent application number 202410939637.0); or a self-sacrificial Na 4 CaSi 3 O 9 Sodium supplement, while improving the first cycle coulombic efficiency of the battery, can also 0.67 Mn 0.67 Ni 0.33 O 2 The capacity retention rate of the battery after 50 cycles of charge and discharge is increased to 90.4% (patent application number 202411472007.3); or the sodium supplement Na is treated by the sol-gel method 3.8 Li 0.2 Fe 2 O 5 The re-coating modification is carried out so that the residual by-products when it is used as a sodium supplement will not affect the subsequent performance of the positive electrode, making Na 2 / 3 Ni 1 / 3 Ti 1 / 3 Mn 1 / 3 O 2 The capacity retention rate of the material after 50 cycles of charge and discharge is as high as 97.5% (patent application number 202410752749.5); or by selecting an organic chain sodium supplement with high compatibility with the positive electrode material to regulate the first effect of the battery, so that Na 2 / 3 Ni 1 / 3 Ti 1 / 3 Mn 1 / 3 O 2The capacity retention rate of the material after 50 cycles of charge and discharge is as high as 98.4% (patent application number 202410051490.1). However, these methods have not yet achieved good stability and electrochemical performance for large-scale applications. Sodium zirconium phosphate is insoluble in water and general organic solvents, is resistant to strong acids and certain alkalis, and can maintain a stable structure and performance in the complex chemical environment of the battery. Its unique crystal structure gives it good ion exchange capacity. During the battery charging and discharging process, it can effectively exchange sodium ions with the positive electrode material, and promptly replenish the sodium ions lost due to irreversible reactions, thereby improving the reversible capacity and cycle stability of the battery.

[0003] The present invention can appropriately modify the large particles of sodium zirconium phosphate through multiple hydrothermal reactions and the final reaction with the positive electrode material to generate small-sized needle-shaped sodium zirconium phosphate, so that the distribution of the material is more uniform and the sodium supplementation effect is better, thereby improving the structural stability of the material during the cycle and improving the electrochemical performance of the battery. The sodium zirconium phosphate sodium supplement can effectively improve the electrochemical performance of sodium ion batteries; the synthesis method of the sodium supplement is simple to operate, efficient, and conducive to industrial promotion and application.

[0004] Compared with the existing sodium supplements, the sodium supplement of the present invention shows excellent data advantages. In terms of capacity retention, the sodium ion battery using the sodium supplement of the present invention has a cycle capacity retention rate of up to 99.20% after 50 cycles of charge and discharge at a rate of 0.2C (1C = 130mA / g), and the discharge specific capacity is increased to 129.3mAh / g. Summary of the invention

[0005] In view of the problems in the prior art that the positive electrode material of the sodium ion battery collapses due to the long-term complex phase change, some sodium ions are irreversibly lost, resulting in a decrease in the capacity and cycle life of the battery, etc. The purpose of the present invention is to provide a new sodium supplement for sodium ion batteries and a preparation method and application thereof. The sodium supplement for sodium ion batteries adopts multiple hydrothermal methods to finally react with the positive electrode material to generate a positive electrode sheet containing needle-shaped products, which provides a new way to solve the problems of poor cycle stability and irreversible loss of sodium ions in the positive electrode materials of the existing sodium ion batteries, and to improve the electrochemical performance of sodium ion batteries.

[0006] In order to achieve the above technical objectives, the technical solution provided by the present invention is:

[0007] A needle-shaped sodium zirconium phosphate sodium supplement, wherein the chemical formula of the needle-shaped sodium zirconium phosphate is Na 2 Zr(PO 4 ) 2 , length is 200~500nm, diameter is 1~20nm.

[0008] A method for preparing needle-shaped sodium zirconium phosphate comprises the following steps:

[0009] 1) mixing a phosphorus source, a zirconium source and deionized water for a first hydrothermal reaction to obtain a precursor;

[0010] 2) Then, the precursor, sodium source and deionized water are mixed for a second hydrothermal reaction to obtain polygonal sheet sodium zirconium phosphate; the chemical formula of the sodium zirconium phosphate is Na 2 Zr(PO 4 ) 2 .

[0011] 3) Mixing polygonal sheet-shaped sodium zirconium phosphate, positive electrode material and solvent to obtain slurry, coating the slurry into electrode sheets, and drying to obtain the product.

[0012] In step 1), the solid-liquid ratio of phosphorus source, zirconium source and deionized water is 1:5-1:10 g / L, and the first hydrothermal reaction is carried out at 150-200° C. for 12-24 hours to obtain a precursor.

[0013] In step 2), the solid-liquid ratio of the precursor, the sodium source, and the deionized water is 1:5 to 1:10 g / L, and a second hydrothermal reaction is carried out at 80 to 120° C. for 12 to 24 hours to obtain polygonal sheet-like sodium zirconium phosphate.

[0014] Step 3) The polygonal sheet sodium zirconium phosphate and the positive electrode material are stirred and mixed in an N-methylpyrrolidone solution at a ratio of 1:100 to 1:10, with a rotation speed of 200 to 500 r / min, a mixing time of 4 to 10 hours, and a solid-liquid ratio of 1:2 to 1:7 g / L. The slurry is then coated on aluminum foil to form a pole piece with a thickness of 0.28 mm, and a third reaction is carried out in a vacuum drying oven at 80 to 120° C. for 10 to 15 hours to obtain the product.

[0015] The above step 3) finally obtains a positive electrode sheet containing a needle-shaped product, wherein the needle-shaped product is a sodium supplement sodium zirconium phosphate, and the needle-shaped product is produced during the preparation process of the positive electrode sheet.

[0016] The sodium source of the present invention comprises at least one of sodium acetate and sodium hydroxide, the phosphorus source comprises phosphoric acid, and the zirconium source comprises zirconium nitrate or its hydrate.

[0017] Preferably, the solid-liquid ratio of the first hydrothermal reaction is 1:5-1:8 g / L, the temperature is 160-180° C., and the reaction time is 12-16 h to obtain a precursor;

[0018] Preferably, the solid-liquid ratio of the second hydrothermal reaction is 1:5-1:8 g / L, the temperature is 100-110° C., and the reaction time is 12-16 h to obtain polygonal sheet-like sodium zirconium phosphate.

[0019] Preferably, the ratio of polygonal sheet sodium zirconium phosphate to positive electrode material is 1:30-1:10, the rotation speed is 200-300 r / min, the mixing time is 4-8 h, and the solid-liquid ratio of the reaction is 1:3-1:5 g / L;

[0020] Preferably, the vacuum drying temperature is 100-110° C. and the reaction time is 12-16 h.

[0021] The positive electrode material of the present invention includes: O3 type sodium ion positive electrode material Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O 2 The present invention also provides an application of the needle-shaped sodium zirconium phosphate sodium supplement for sodium supplementation in sodium ion batteries.

[0022] The present invention provides a sodium zirconium phosphate sodium supplement with a needle-like morphology, which can be better compounded with the positive electrode material during synthesis. The present invention optimizes the sodium zirconium phosphate sodium supplement into a specific needle-like structure, which can be more evenly compounded with the positive electrode material of the sodium ion battery, and the sodium supplement effect is better. While supplementing sodium, a zirconium hydrogen phosphate coating layer can be formed to improve the sodium ion diffusion channel and environmental components, thereby improving the structural stability of the material during the cycle and effectively inhibiting phase change. The rate performance and cycle performance of the positive electrode material of the sodium ion battery are greatly improved, which is conducive to large-scale promotion and application.

[0023] Beneficial effects:

[0024] (1) Compared with other complex synthesis methods, the present invention adopts a simple hydrothermal method, which has low production cost, mature industrial technology and better industrial compatibility.

[0025] (2) The technical solution of the present invention can optimize the morphology and structure of the sodium zirconium phosphate sodium supplement, and effectively improve the sodium ion diffusion performance and electrochemical performance of the sodium ion battery. It alleviates the problems of structural collapse caused by long-term complex phase changes in the positive electrode materials of the current sodium ion battery, and the side reactions caused by excessive contact with the electrolyte, thereby extending the service life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a SEM image of the polygonal flake sodium zirconium phosphate in Example 1 of the present invention;

[0027] Figure 2 This is a SEM image of the positive electrode of the battery in Comparative Example 1 of the present invention before charge and discharge cycles;

[0028] Figure 3 This is a SEM image of the positive electrode of the battery in Example 1 of the present invention before charge and discharge cycles;

[0029] Figure 4This is a SEM image of the positive electrode of the battery after charge and discharge cycles in Example 1 of the present invention;

[0030] Figure 5 The charge and discharge cycle diagram of the battery of Example 1 of the present invention and Comparative Example 1 at a rate of 5C (1C = 130 mA / g);

[0031] Figure 6 The charge and discharge cycle diagram of the battery of Example 1 of the present invention and Comparative Example 1 at a rate of 0.2C (1C = 130 mA / g);

[0032] Figure 7 The first cycle charge and discharge curves of the batteries of Example 1 and Comparative Example 1 of the present invention at a rate of 0.2C (1C=130mA / g) are shown. DETAILED DESCRIPTION

[0033] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0034] Example 1

[0035] The chemical formula of the O3 type sodium ion positive electrode material used in this embodiment is: Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O 2 , the chemical formula of needle-shaped sodium zirconium phosphate sodium supplement is: Na 2 Zr(PO 4 ) 2 . The specific preparation method is as follows: phosphoric acid and zirconium nitrate pentahydrate are mixed in a molar ratio of 1:2, and then added to a stainless steel reactor lined with polytetrafluoroethylene with deionized water, with a solid-liquid ratio of 1:5 g / L, and a first hydrothermal reaction is carried out at 180°C for 18 hours to obtain a precursor. The precursor, sodium acetate, and sodium hydroxide are mixed in a mass ratio of 0.50:2.05:0.10, and then added to a stainless steel reactor lined with polytetrafluoroethylene with deionized water, with a solid-liquid ratio of 1:5 g / L, and a second hydrothermal reaction is carried out at 100°C for 12 hours to obtain polygonal flake sodium zirconium phosphate (see Figure 1 ). Then polygonal sheet sodium zirconium phosphate and Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O 2The mixture was stirred and mixed in N-methylpyrrolidone solution at a mass ratio of 1:20, with a speed of 300r / min, a mixing time of 6h, and a solid-liquid ratio of 1:4g / L. The slurry was then coated on aluminum foil to form a 0.28mm thick pole piece, and reacted at 100°C in a vacuum drying oven for 10h to obtain a positive pole piece. The composite material exhibited good electrochemical performance in sodium ion batteries, with the first discharge capacities of 0.2C, 1C and 5C being 129.3mAh / g, 106.2mAh / g and 87.4mAh / g. The capacity retention rates of the battery after 50 and 100 charge and discharge cycles at a rate of 0.2C were 99.20% and 96.25%, respectively. When the rate was increased to 5C, the capacity retention rates after 100 and 500 charge and discharge cycles were 93.34% and 81.09%, respectively. Figure 3 and Figure 4 The SEM images of the positive electrode of the battery in this embodiment before and after the charge and discharge cycle are shown in Figure 2. Figure 3 Needle-shaped products appeared before the mesocycle, and after the cycle Figure 4 The needle-shaped product disappeared.

[0036] Example 2

[0037] The chemical formula of the sodium ion positive electrode material of this embodiment is: Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O 2 , the chemical formula of needle-shaped sodium zirconium phosphate sodium supplement is: Na 2 Zr(PO 4 ) 2 . The specific preparation method is as follows: phosphoric acid and zirconium nitrate pentahydrate are mixed in a molar ratio of 1:2, and added together with deionized water into a stainless steel reactor with a polytetrafluoroethylene lining, with a solid-liquid ratio of 1:8 g / L, and the first hydrothermal reaction is carried out at 160°C for 12 hours to obtain a precursor. The precursor, sodium acetate, and sodium hydroxide are mixed in a mass ratio of 0.50:2.05:0.10, and added together with deionized water into a stainless steel reactor with a polytetrafluoroethylene lining, with a solid-liquid ratio of 1:5 g / L, and the second hydrothermal reaction is carried out at 100°C for 12 hours to obtain polygonal sodium zirconium phosphate. Then the polygonal sodium zirconium phosphate and Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O 2The mixture was stirred and mixed in N-methylpyrrolidone solution at a mass ratio of 1:20, with a speed of 300r / min, a mixing time of 6h, and a solid-liquid ratio of 1:4g / L. The slurry was then coated on aluminum foil to form a pole piece with a thickness of 0.28mm, and reacted in a vacuum drying oven at 100°C for 10h to obtain a positive pole piece. The composite material exhibited good electrochemical performance in sodium ion batteries, with the first discharge capacities of 0.2C, 1C and 5C being 124.3mAh / g, 100.2mAh / g and 80.3mAh / g. The capacity retention rates of the battery after 50 and 100 charge and discharge cycles at a rate of 0.2C were 95.0% and 93.29%, respectively. When the rate was increased to 5C, the capacity retention rates after 100 and 500 charge and discharge cycles were 91.67% and 77.25%, respectively.

[0038] Example 3

[0039] The chemical formula of the O3 type sodium ion positive electrode material of this embodiment is: Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O 2 , the chemical formula of needle-shaped sodium zirconium phosphate sodium supplement is: Na 2 Zr(PO 4 ) 2 . The specific preparation method is as follows: phosphoric acid and zirconium nitrate pentahydrate are mixed in a molar ratio of 1:2, and added together with deionized water into a stainless steel reactor with a polytetrafluoroethylene lining, with a solid-liquid ratio of 1:5 g / L, and the first hydrothermal reaction is carried out at 180°C for 18 hours to obtain a precursor. The precursor, sodium acetate, and sodium hydroxide are mixed in a mass ratio of 0.50:2.05:0.10, and added together with deionized water into a stainless steel reactor with a polytetrafluoroethylene lining, with a solid-liquid ratio of 1:8 g / L, and the second hydrothermal reaction is carried out at 110°C for 16 hours to obtain polygonal sodium zirconium phosphate. Then the polygonal sodium zirconium phosphate and Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O 2The mixture was stirred and mixed in N-methylpyrrolidone solution at a mass ratio of 1:20, with a speed of 300r / min, a mixing time of 6h, and a solid-liquid ratio of 1:4g / L. The slurry was then coated on aluminum foil to form a pole piece with a thickness of 0.28mm, and reacted in a vacuum drying oven at 100°C for 10h to obtain a positive pole piece. The composite material exhibited good electrochemical performance in sodium ion batteries, with the first discharge capacities of 0.2C, 1C and 5C being 125.3mAh / g, 102.2mAh / g and 81.4mAh / g. The capacity retention rates of the battery after 50 and 100 charge and discharge cycles at a rate of 0.2C were 96.4% and 94.53%, respectively. When the rate was increased to 5C, the capacity retention rates after 100 and 500 charge and discharge cycles were 92.17% and 79.57%, respectively.

[0040] Example 4

[0041] The chemical formula of the O3 type sodium ion positive electrode material of this embodiment is: Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O 2 , the chemical formula of needle-shaped sodium zirconium phosphate sodium supplement is: Na 2 Zr(PO 4 ) 2 . The specific preparation method is as follows: phosphoric acid and zirconium nitrate pentahydrate are mixed in a molar ratio of 1:2, and added together with deionized water into a stainless steel reactor with a polytetrafluoroethylene lining, with a solid-liquid ratio of 1:5 g / L, and the first hydrothermal reaction is carried out at 180°C for 18 hours to obtain a precursor. The precursor, sodium acetate, and sodium hydroxide are mixed in a mass ratio of 0.50:2.05:0.10, and added together with deionized water into a stainless steel reactor with a polytetrafluoroethylene lining, with a solid-liquid ratio of 1:5 g / L, and the second hydrothermal reaction is carried out at 100°C for 12 hours to obtain polygonal sodium zirconium phosphate. Then the polygonal sodium zirconium phosphate and Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O 2The mixture was stirred and mixed in N-methylpyrrolidone solution at a mass ratio of 1:30, with a speed of 200r / min, a mixing time of 4h, and a solid-liquid ratio of 1:4g / L. The slurry was then coated on aluminum foil to form a pole piece with a thickness of 0.28mm, and reacted in a vacuum drying oven at 100°C for 10h to obtain a positive pole piece. The composite material exhibited good electrochemical performance in sodium ion batteries, with the first discharge capacities of 0.2C, 1C and 5C being 126.6mAh / g, 103.7mAh / g and 86.5mAh / g. The capacity retention rates of the battery after 50 and 100 charge and discharge cycles at a rate of 0.2C were 95.36% and 93.44%, respectively. When the rate was increased to 5C, the capacity retention rates after 100 and 500 charge and discharge cycles were 91.99% and 78.94%, respectively.

[0042] Example 5

[0043] The chemical formula of the O3 type sodium ion positive electrode material of this embodiment is: Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O 2 , the chemical formula of needle-shaped sodium zirconium phosphate sodium supplement is: Na 2 Zr(PO 4 ) 2 . The specific preparation method is as follows: phosphoric acid and zirconium nitrate pentahydrate are mixed in a molar ratio of 1:2, and added together with deionized water into a stainless steel reactor with a polytetrafluoroethylene lining, with a solid-liquid ratio of 1:5 g / L, and the first hydrothermal reaction is carried out at 180°C for 18 hours to obtain a precursor. The precursor, sodium acetate, and sodium hydroxide are mixed in a mass ratio of 0.50:2.05:0.10, and added together with deionized water into a stainless steel reactor with a polytetrafluoroethylene lining, with a solid-liquid ratio of 1:5 g / L, and the second hydrothermal reaction is carried out at 100°C for 12 hours to obtain polygonal sodium zirconium phosphate. Then the polygonal sodium zirconium phosphate and Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O 2The mixture was stirred and mixed in N-methylpyrrolidone solution at a mass ratio of 1:20, with a speed of 300r / min, a mixing time of 6h, and a solid-liquid ratio of 1:5g / L. The slurry was then coated on aluminum foil to form a pole piece with a thickness of 0.28mm, and reacted in a vacuum drying oven at 110°C for 16h to obtain a positive pole piece. The composite material exhibited good electrochemical performance in sodium ion batteries, with the first discharge capacities of 0.2C, 1C and 5C being 124.7mAh / g, 101.8mAh / g and 81.6mAh / g. The capacity retention rates of the battery after 50 and 100 charge and discharge cycles at a rate of 0.2C were 97.1% and 94.65%, respectively. When the rate was increased to 5C, the capacity retention rates after 100 and 500 charge and discharge cycles were 92.33% and 80.34%, respectively.

[0044] Example 6

[0045] The chemical formula of the O3 type sodium ion positive electrode material of this embodiment is: Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O 2 , the chemical formula of needle-shaped sodium zirconium phosphate sodium supplement is: Na 2 Zr(PO 4 ) 2 . The specific preparation method is as follows: phosphoric acid and zirconium nitrate pentahydrate are mixed in a molar ratio of 1:2, and added together with deionized water into a stainless steel reactor with a polytetrafluoroethylene lining, with a solid-liquid ratio of 1:8 g / L, and the first hydrothermal reaction is carried out at 160°C for 12 hours to obtain a precursor. The precursor, sodium acetate, and sodium hydroxide are mixed in a mass ratio of 0.50:2.05:0.10, and added together with deionized water into a stainless steel reactor with a polytetrafluoroethylene lining, with a solid-liquid ratio of 1:8 g / L, and the second hydrothermal reaction is carried out at 110°C for 16 hours to obtain polygonal sodium zirconium phosphate. Then the polygonal sodium zirconium phosphate and Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O 2The mixture was stirred and mixed in N-methylpyrrolidone solution at a mass ratio of 1:30, with a speed of 200r / min, a mixing time of 8h, and a solid-liquid ratio of 1:4g / L. The slurry was then coated on aluminum foil to form a 0.28mm thick pole piece, and reacted in a vacuum drying oven at 110°C for 16h to obtain a positive pole piece. The composite material exhibited good electrochemical performance in sodium ion batteries, with the first discharge capacities of 0.2C, 1C and 5C being 128.9mAh / g, 104.9mAh / g and 84.7mAh / g. The capacity retention rates of the battery after 50 and 100 charge and discharge cycles at a rate of 0.2C were 98.21% and 94.85%, respectively. When the rate was increased to 5C, the capacity retention rates after 100 and 500 charge and discharge cycles were 93.05% and 80.84%, respectively.

[0046] Comparative Example 1

[0047] This comparative example is Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O 2 Materials (see Figure 2 ) was used to make the positive electrode sheet. Tests found that its first discharge capacity at 0.2C, 1C and 5C was 122.1mAh / g, 89.4mAh / g and 67.3mAh / g. The battery retained 50.00% and 22.79% of its capacity after 50 and 100 charge and discharge cycles at 0.2C rate, respectively. When the rate was increased to 5C, the capacity retention rates after 100 and 500 charge and discharge cycles were 78.56% and 45.77%, respectively. The electrochemical performance is significantly lower than that of the material after adding the sodium supplement, indicating that needle-shaped sodium zirconium phosphate has a significant effect on improving the material performance.

[0048] Comparative Example 2

[0049] The chemical formula of the sodium ion positive electrode material used in this comparative example is: Na 0.9 [Cu 0.22 Fe 0.30 Mn 0.48 ]O 2 , the chemical formula of sodium zirconium phosphate sodium supplement is: Na 2 Zr(PO 4 ) 2. The specific preparation method is as follows: After phosphoric acid and zirconium nitrate pentahydrate are mixed in a molar ratio of 1:2, they are added together with deionized water into a stainless steel reactor with a polytetrafluoroethylene lining, and the solid-liquid ratio is 1:5g / L. The first hydrothermal reaction is carried out at 180°C for 18 hours to obtain a precursor. After the precursor, sodium acetate and sodium hydroxide are mixed in a mass ratio of 0.50:2.05:0.10, they are added together with deionized water into a stainless steel reactor with a polytetrafluoroethylene lining, and the solid-liquid ratio is 1:5g / L. The second hydrothermal reaction is carried out at 100°C for 12 hours to obtain polygonal sodium zirconium phosphate. Then the polygonal sodium zirconium phosphate and Na 0.9 [Cu 0.22 Fe 0.30 Mn 0.48 ]O 2 The mixture was stirred and mixed in N-methylpyrrolidone solution at a mass ratio of 1:20, with a rotation speed of 300 r / min, a mixing time of 6 h, and a solid-liquid ratio of 1:4 g / L. The slurry was then coated on aluminum foil to form an electrode with a thickness of 0.28 mm, and reacted in a vacuum drying oven at 100 ° C for 10 h to obtain Na doped with a sodium supplement. 0.9 [Cu 0.22 Fe 0.30 Mn 0.48 ]O 2 Positive electrode sheet. The composite material does not produce needle-shaped products. The electrochemical performance in sodium ion batteries: the first discharge capacity of 0.2C, 1C and 5C is 103.6mAh / g, 71.2mAh / g and 50.1mAh / g. The battery has a capacity retention rate of 92.36% and 83.15% after 50 and 100 charge and discharge cycles at a rate of 0.2C, respectively. When the rate is increased to 5C, the capacity retention rate after 100 and 500 charge and discharge cycles is 92.34% and 79.71%, respectively.

[0050] Comparative Example 3

[0051] This comparative example is Na without adding sodium zirconium phosphate sodium supplement 0.9 [Cu 0.22 Fe 0.30 Mn 0.48 ]O 2 The positive electrode sheet made of the material. The test found that its first discharge capacity at 0.2C, 1C and 5C was 93.0mAh / g, 63.7mAh / g and 43.0mAh / g. The battery retained 87.19% and 80.80% of its capacity after 50 and 100 charge and discharge cycles at 0.2C rate, and when the rate was increased to 5C, the capacity retention rate after 100 and 500 charge and discharge cycles was 90.55% and 77.64%, respectively. The electrochemical performance is significantly lower than that of the material after adding the sodium supplement, indicating that sodium zirconium phosphate has a significant effect on improving the material performance.

[0052] In summary, the needle-shaped sodium zirconium phosphate sodium supplementer for O3-type sodium ion positive electrode materials based on the hydrothermal method and the preparation method thereof of the present invention have significant advantages and provide an effective way for the development of high-performance sodium ion battery sodium supplementers.

Claims

1. A needle-shaped sodium zirconium phosphate sodium supplement, characterized in that: The needle-shaped sodium zirconium phosphate has a chemical formula of Na2Zr(PO4)2, a length of 200-500nm, and a diameter of 1-20nm.

2. A method for preparing needle-shaped sodium zirconium phosphate, characterized in that: The following steps are involved: 1) mixing a phosphorus source, a zirconium source and deionized water for a first hydrothermal reaction to obtain a precursor; 2) Then, the precursor, the sodium source and the deionized water are mixed for a second hydrothermal reaction to obtain polygonal sodium zirconium phosphate; the chemical formula of the sodium zirconium phosphate is Na2Zr(PO4)2; 3) Mixing polygonal sheet-shaped sodium zirconium phosphate, positive electrode material and solvent to obtain slurry, coating the slurry into electrode sheets, and drying to obtain the product.

3. The preparation method according to claim 2, characterized in that: In step 1), the solid-liquid ratio of phosphorus source, zirconium source and deionized water is 1:5-1:10 g / L, and the first hydrothermal reaction is carried out at 150-200° C. for 12-24 hours to obtain a precursor.

4. The preparation method according to claim 2, characterized in that: In step 2), the solid-liquid ratio of the precursor, the sodium source, and the deionized water is 1:5 to 1:10 g / L, and a second hydrothermal reaction is carried out at 80 to 120° C. for 12 to 24 hours to obtain polygonal sheet-like sodium zirconium phosphate.

5. The preparation method according to claim 2, characterized in that: Step 3) The polygonal sheet sodium zirconium phosphate and the positive electrode material are stirred and mixed in an N-methylpyrrolidone solution at a mass ratio of 1:100 to 1:10, with a rotation speed of 200 to 500 r / min, a mixing time of 4 to 10 hours, and a solid-liquid ratio of 1:2 to 1:7 g / L. The slurry is then coated on aluminum foil to form a pole piece with a thickness of 0.28 mm, and a third reaction is carried out in a vacuum drying oven at 80 to 120° C. for 10 to 15 hours to obtain the product.

6. The preparation method according to any one of claims 2 to 5, characterized in that: The sodium source includes at least one of sodium acetate and sodium hydroxide, the phosphorus source includes phosphoric acid, and the zirconium source includes zirconium nitrate or its hydrate.

7. The preparation method according to any one of claims 2 to 5, characterized in that: The solid-liquid ratio of the first hydrothermal reaction is 1:5-1:8 g / L, the temperature is 160-180° C., and the reaction time is 12-16 h to obtain a precursor; The solid-liquid ratio of the second hydrothermal reaction is 1:5-1:8 g / L, the temperature is 100-110° C., and the reaction time is 12-16 hours to obtain polygonal flake sodium zirconium phosphate.

8. The preparation method according to any one of claims 2 to 5, characterized in that: The ratio of polygonal sheet sodium zirconium phosphate to positive electrode material is 1:30-1:10, the rotation speed is 200-300 r / min, the mixing time is 4-8 hours, and the solid-liquid ratio of the reaction is 1:3-1:5 g / L; The vacuum drying temperature is 100-110°C, and the reaction time is 12-16h.

9. The preparation method according to any one of claims 2 to 5, characterized in that: The positive electrode material includes: O3 type sodium ion positive electrode material Na[Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ]O2.

10. The use of the needle-shaped sodium zirconium phosphate sodium supplement according to claim 1, or the needle-shaped sodium zirconium phosphate sodium supplement prepared by the method according to any one of claims 2 to 9, characterized in that: Used to replenish sodium in sodium-ion batteries.

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