CN115417393A - A kind of spherical sodium manganese zirconium phosphate/carbon composite material and its preparation method and application - Google Patents

Abstract

A spherical sodium manganese zirconium phosphate/carbon composite material and its preparation method and application, the material chemical formula is: Na ₃ MnZr(PO ₄ ) ₃ /C, and its preparation method is as follows: sodium source, phosphorus source, manganese source, zirconium The carbon source and the carbon source are stirred and dispersed into a uniform solution according to a certain stoichiometric ratio to obtain a mixed solution; the mixed solution is spray-dried to rapidly evaporate the water to obtain a precursor; the precursor is roasted in a protective atmosphere to obtain a secondary particle shape It is a spherical sodium manganese zirconium phosphate/carbon composite material. The material is applied to the positive electrode material of the sodium ion battery, and exhibits higher discharge voltage, discharge specific capacity and better cycle stability. The synthesis method is simple in operation and short in process flow.

Description

A kind of spherical sodium manganese zirconium phosphate/carbon composite material and its preparation method and application

technical field

The invention relates to the technical field of preparation of positive electrode materials for sodium ion batteries, in particular to a spherical sodium manganese zirconium phosphate/carbon composite material and its preparation method and application.

Background technique

Sodium-ion batteries use sodium, which is abundant and widely distributed, as the load ion, so it has an outstanding advantage in terms of raw material prices, which is conducive to reducing the cost of electrochemical energy storage. The general molecular formula of NASICON type phosphate cathode material is Na ₃ M ₂ (PO ₄ ) ₃ , where M can be selected from divalent, trivalent and tetravalent ions of V, Fe, Mn, Ti, Zr and other elements. Among such materials, Na ₃ V ₂ (PO ₄ ) ₃ has higher discharge voltage and longer cycle life, but vanadium is more polluting to the environment, which is not conducive to industrialization. The raw material cost of Na ₃ Fe ₂ (PO ₄ ) ₃ is relatively low, but the discharge voltage of iron-based materials is low, which puts them at a disadvantage in the competition of energy density. In contrast, in manganese-based NASICON-type phosphate Na ₃ MnM(PO ₄ ) ₃ (M is a tetravalent transition metal ion), Mn can realize two-electron transfer, that is, use Mn ²⁺ /Mn ⁴⁺ redox couple The electrochemical reaction is carried out, which enables it to have a higher discharge voltage when the capacity is comparable to that of Na ₃ V ₂ (PO ₄ ) ₃ and other materials. The content of zirconium in the earth's crust is 0.025%, which is more than the total amount of common metals such as copper, lead and zinc. From the perspective of resources, Na ₃ MnZr(PO ₄ ) ₃ has good development potential. However, the electronic conductivity of Na ₃ MnZr(PO ₄ ) ₃ is relatively low, and the high discharge voltage easily causes the decomposition of the electrolyte, thus affecting the cycle stability of the material. Improving the electrochemical performance of Na ₃ MnZr(PO ₄ ) ₃ requires the introduction of conductive carbon by appropriate synthesis methods to improve electronic conductivity, and at the same time, the design of secondary particle morphology inhibits the electrolyte from flowing in Na ₃ MnZr(PO ₄ ) under high voltage. ₃ Decomposition of the surface.

Contents of the invention

In view of the above-mentioned problems, the present invention provides spherical sodium manganese zirconium phosphate/carbon composite material, the purpose of which is to obtain manganese phosphate with high charge and discharge capacity, good cycle stability and rate performance with simple operation and short process flow. Sodium zirconium/carbon composite cathode material.

To achieve the above object, the technical solution of the present invention is to provide a spherical sodium manganese zirconium phosphate/carbon composite material, the chemical formula of which is: Na ₃ MnZr(PO ₄ ) ₃ /C. Na ₃ MnZr(PO ₄ ) ₃ has a rhombohedral NASICON crystal structure; the carbon in the composite material is amorphous carbon, and the carbon layer is coated on the surface of the primary particle of Na ₃ MnZr(PO ₄ ) ₃ ; the morphology of the secondary particle of the composite material Spherical.

The spherical manganese zirconium phosphate sodium/carbon composite material is prepared from sodium salt, manganese salt, zirconium salt, phosphate and carbon source, wherein the sodium salt and phosphate used can be the same substance, and the spherical manganese phosphate The preparation method of zirconium sodium/carbon composite material comprises the steps:

(1) Sodium salt, manganese salt, zirconium salt, phosphate and carbon source of stoichiometric ratio are dissolved in a certain amount of water, and dispersed by continuous stirring to form a uniform mixed solution;

(2) The resulting mixed solution is put into a spray drying tower for spray drying, so that the water is rapidly evaporated to obtain a precursor;

(3) Put the above-mentioned precursor in a heating furnace, and roast it under the condition of passing a protective gas to obtain a spherical sodium manganese zirconium phosphate/carbon composite material.

Among the raw materials, the sodium salt is selected from one or more combinations of sodium acetate, sodium dihydrogen phosphate and sodium citrate; the manganese salt is manganese acetate; the zirconium salt is selected from zirconium acetate, One or a combination of zirconium acetylacetonate, zirconium citrate, zirconium propionate, zirconium methacrylate; the phosphate is selected from sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium phosphate, ammonium dihydrogen phosphate , diammonium hydrogen phosphate, ammonium phosphate, or a combination of several; the carbon source is selected from one or a combination of citric acid, sucrose, and glucose.

The feed inlet temperature of the spray drying tower is 120-300°C.

In the preparation method of the spherical sodium manganese zirconium phosphate/carbon composite material, the protective gas is one of nitrogen, argon, nitrogen-hydrogen mixed gas, and argon-hydrogen mixed gas, and the roasting temperature is 600-800°C. The time is 4-12h.

In the preparation method of the spherical sodium manganese zirconium phosphate/carbon composite material, the carbon content in the obtained spherical manganese zirconium sodium phosphate/carbon composite material can be regulated by changing the amount of carbon source added in the raw material, and the carbon content in the composite material It is 1-10wt%.

The application of the spherical sodium manganese zirconium phosphate/carbon composite material as a positive electrode material in a sodium ion battery.

The beneficial effects of the present invention are:

1) forming spherical manganese-zirconium-zirconium-phosphate and carbon composites through spray drying, which is conducive to forming an interconnected carbon coating on the surface of manganese-zirconium-sodium phosphate particles and improving the electron conductance of manganese-zirconium-sodium phosphate particles;

2) The dense spherical secondary particle morphology is conducive to inhibiting the decomposition of the electrolyte at high voltage, and is also conducive to improving the compaction density of the material.

3) The preparation method is simple to operate, the reaction conditions are easy to control, and the process flow is short.

Description of drawings

Fig. 1 is an X-ray diffraction pattern of Na ₃ MnZr(PO ₄ ) ₃ /C prepared in Example 1 of the present invention;

Figure 2 is an SEM image of Na ₃ MnZr(PO ₄ ) ₃ /C prepared in Example 1 of the present invention;

Fig. 3 is the charge-discharge curve of Na ₃ MnZr(PO ₄ ) ₃ /C prepared in Example 1 of the present invention at a rate of 0.1C;

Figure 4 shows the long-term cycle performance of a sodium ion half-cell at a rate of 2C when Na ₃ MnZr(PO ₄ ) ₃ /C prepared in Example 1 of the present invention is used as the positive electrode material;

Fig. 5 is an X-ray diffraction pattern of Na ₃ MnZr(PO ₄ ) ₃ /C prepared in Example 2 of the present invention;

Fig. 6 is an SEM image of Na ₃ MnZr(PO ₄ ) ₃ /C prepared in Example 2 of the present invention;

Fig. 7 is the charge-discharge curve of Na ₃ MnZr(PO ₄ ) ₃ /C prepared in Example 2 of the present invention at a rate of 0.1C;

Fig. 8 shows the long-term cycle performance of the sodium ion half-cell at 2C rate when Na ₃ MnZr(PO ₄ ) ₃ /C prepared in Example 2 of the present invention is used as the positive electrode material.

detailed description

The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments.

Example 1

This embodiment is an example of the preparation method of the spherical sodium manganese zirconium phosphate/carbon composite material of the present invention, comprising the following steps:

2.340 g of 0.015 mol NaH ₂ PO ₄ ·2H ₂ O, 1.225 g of 0.005 mol Mn(CH ₃ COO) ₂ ·4H ₂ O, 2.458 g of 0.005 mol Zr(C ₅ H ₈ O ₂ ) ₄ and 1.801 g 0.010mol of C ₆ H ₁₂ O ₆ was dissolved in 20 mL of deionized water, heated and stirred at room temperature to obtain a uniform mixed solution. The obtained mixed solution was spray-dried, and the temperature of the inlet of the spray-drying tower was controlled to be 160° C. to obtain a precursor. The above spray-dried precursor was calcined at 750° C. for 12 hours in a tube furnace filled with argon to obtain a spherical Na ₃ MnZr(PO ₄ ) ₃ /C composite material. The XRD pattern of the obtained Na ₃ MnZr(PO ₄ ) ₃ /C is shown in Figure 1 , and the diffraction peaks in Figure 1 are all attributed to Na ₃ MnZr(PO ₄ ) ₃ . The SEM image of the obtained Na ₃ MnZr(PO ₄ ) ₃ /C is shown in Figure 2. The secondary particles of the material are formed by the aggregation of many primary particles, and the secondary particles are spherical in shape with a particle size of 1-4 μm.

Mix Na ₃ MnZr(PO ₄ ) ₃ /C, acetylene black, and PVDF in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1, and coat the resulting slurry on an aluminum foil with a diameter of 16mm , and then vacuum-dried the aluminum foil at 80° C. to prepare a positive electrode sheet. In an argon atmosphere glove box, with metallic sodium as the negative electrode, 1mol L ^-1 NaClO ₄ /propylene carbonate (PC):fluoroethylene carbonate (FEC) (volume ratio 95:5) as the electrolyte, Whatman GF/ D glass fiber is assembled into a button battery (CR2025) for the separator. Figure 3 shows the charge-discharge curves of Na ₃ MnZr(PO ₄ ) ₃ /C at a current density of 0.1C, and the first-cycle charge-discharge specific capacities are 102.4mAh g ^-1 and 98.7mAh g ^-1 , respectively. Figure 4 shows the discharge specific capacity-cycle number diagram of Na ₃ MnZr(PO ₄ ) ₃ /C at 2C rate, and the first discharge specific capacity shown in Figure 4 is 77.0mAh g ^-1 after 1000 cycles The capacity retention rate is 86.4%.

Example 2

This embodiment is another example of the preparation method of the spherical sodium manganese zirconium phosphate/carbon composite material of the present invention, comprising the following steps:

2.340 g of 0.015 mol NaH ₂ PO ₄ 2H ₂ O, 1.225 g of 0.005 mol Mn(CH ₃ COO) ₂ 4H ₂ O, 1.637 g of 0.005 mol Zr(CH ₃ COO) ₄ and 2.702 g of 0.015 mol C ₆ H ₁₂ O ₆ was dissolved in 20 mL of deionized water, heated and stirred at room temperature to obtain a uniform mixed solution. The obtained mixed solution was spray-dried, and the temperature of the inlet of the spray-drying tower was controlled to be 200° C. to obtain a precursor. The above spray-dried precursor was calcined at 750° C. for 8 hours in a tube furnace filled with argon to obtain a spherical Na ₃ MnZr(PO ₄ ) ₃ /C composite material. The XRD pattern of the obtained Na ₃ MnZr(PO ₄ ) ₃ /C is shown in FIG. 5 , and the diffraction peaks in the figure all belong to Na ₃ MnZr(PO ₄ ) ₃ . The SEM image of the obtained Na ₃ MnZr(PO ₄ ) ₃ /C is shown in Figure 6. The secondary particles of the material are formed by the aggregation of many primary particles, and the secondary particles are spherical in shape with a particle size of 1-4 μm.

Mix Na ₃ MnZr(PO ₄ ) ₃ /C, acetylene black, and PVDF in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1, and coat the resulting slurry on an aluminum foil with a diameter of 16mm , and then vacuum-dried the aluminum foil at 80° C. to prepare a positive electrode sheet. In an argon atmosphere glove box, with metal sodium as the negative electrode, 1mol/L NaClO ₄ /propylene carbonate (PC): fluoroethylene carbonate (FEC) (volume ratio 95:5) as the electrolyte, Whatman GF/D The glass fiber is used as the diaphragm to assemble the button cell (CR2025). Figure 7 shows the charge-discharge curves of Na ₃ MnZr(PO ₄ ) ₃ /C at a current density of 0.1C. Under this condition, the first cycle charge-discharge specific capacities of the material are 103.0mAh g ^-1 and 99.2mAh g -1 respectively ^{. 1} . Figure 8 shows the discharge specific capacity-cycle number diagram of Na ₃ MnZr(PO ₄ ) ₃ /C at 2C rate, the figure shows that the discharge specific capacity in the first cycle is 76.5mAh g ^-1 and after 1000 cycles The capacity retention rate was 84.4%.

Example 3

This embodiment is another example of the preparation method of the spherical sodium manganese zirconium phosphate/carbon composite material of the present invention, comprising the following steps:

2.340 g of 0.015 mol NaH ₂ PO ₄ 2H ₂ O, 1.225 g of 0.005 mol Mn(CH ₃ COO) ₂ 4H ₂ O, 1.918 g of 0.005 mol Zr(CH ₃ CH ₂ COO) ₄ and 2.396 g of 0.007mol of C ₁₂ H ₂₂ O ₁₁ was dissolved in 20 mL of deionized water, heated and stirred at room temperature to obtain a uniform mixed solution. The obtained mixed solution was spray-dried, and the temperature of the inlet of the spray-drying tower was controlled to be 160° C. to obtain a precursor. The above spray-dried precursor was calcined at 700° C. for 10 h in a tube furnace filled with argon to obtain a spherical Na ₃ MnZr(PO ₄ ) ₃ /C composite material.

Mix Na ₃ MnZr(PO ₄ ) ₃ /C, acetylene black, and PVDF in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1, and coat the resulting slurry on an aluminum foil with a diameter of 16mm , and then vacuum-dried the aluminum foil at 80° C. to prepare a positive electrode sheet. In an argon atmosphere glove box, with metallic sodium as the negative electrode, 1mol L ^-1 NaClO ₄ /propylene carbonate (PC):fluoroethylene carbonate (FEC) (volume ratio 95:5) as the electrolyte, Whatman GF/ D glass fiber is assembled into a button battery (CR2025) for the separator. The first-cycle charge-discharge specific capacities of Na ₃ MnZr(PO ₄ ) ₃ /C at a current density of 0.1C are 102.9mAh g ^-1 and 99.0mAh g ^-1 , respectively. The discharge specific capacity of Na ₃ MnZr(PO ₄ ) ₃ /C at 2C rate is 76.8mAh g ^-1 in the first cycle, and the capacity retention rate after 1000 cycles is 85.2%.

Example 4

This embodiment is the 4th example of the preparation method of the spherical sodium manganese zirconium phosphate/carbon composite material of the present invention, comprising the following steps:

2.340 g of 0.015 mol NaH ₂ PO ₄ ·2H ₂ O, 1.225 g of 0.005 mol Mn(CH ₃ COO) ₂ ·4H ₂ O, 1.673 g of 0.005 mol Zr(CH ₃ COO) ₄ and 3.074 g of 14 mmol C ₆ H ₈ O ₇ was dissolved in 20 mL of deionized water, heated and stirred at room temperature to obtain a uniform mixed solution. The obtained mixed solution was spray-dried, and the temperature of the feed inlet of the spray-drying tower was controlled to be 180° C. to obtain a precursor. The above spray-dried precursor was calcined at 770° C. for 6 h in a tube furnace filled with argon to obtain a spherical Na ₃ MnZr(PO ₄ ) ₃ /C composite material.

Mix Na ₃ MnZr(PO ₄ ) ₃ /C, acetylene black, and PVDF in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1, and coat the resulting slurry on an aluminum foil with a diameter of 16mm , and then vacuum-dried the aluminum foil at 80° C. to prepare a positive electrode sheet. In an argon atmosphere glove box, with metallic sodium as the negative electrode, 1mol L ^-1 NaClO ₄ /propylene carbonate (PC):fluoroethylene carbonate (FEC) (volume ratio 95:5) as the electrolyte, Whatman GF/ D glass fiber is assembled into a button battery (CR2025) for the separator. The first-cycle charge-discharge specific capacities of Na ₃ MnZr(PO ₄ ) ₃ /C at a current density of 0.1C are 102.3mAh g ^-1 and 98.9mAh g ^-1 , respectively. The discharge specific capacity of Na ₃ MnZr(PO ₄ ) ₃ /C at 2C rate is 76.0mAh g ^-1 in the first cycle, and the capacity retention rate after 1000 cycles is 83.0%.

Table 1 Electrochemical properties of spherical Na ₃ MnZr(PO ₄ ) ₃ /C materials prepared under different technical conditions

From the composition and electrochemical performance data of spherical sodium manganese zirconium phosphate/carbon composites under different technical conditions in Table 1, it can be seen that changing the type and molar ratio of raw materials can adjust the carbon concentration in Na ₃ MnZr(PO ₄ ) ₃ /C composites. (C), increasing the carbon content will reduce the discharge capacity of the material under low-rate charge-discharge conditions, but it is beneficial to improve the discharge capacity and cycle stability of Na ₃ MnZr(PO ₄ ) ₃ under high-rate charge-discharge conditions sex.

Claims (8)

1. The spherical sodium zirconium phosphate/carbon composite material is characterized in that the chemical formula of the sodium zirconium phosphate/carbon composite material is Na ₃ MnZr(PO ₄ ) ₃ /C；Na ₃ MnZr(PO ₄ ) ₃ Has a rhombohedral NASICON-type crystal structure; the carbon in the composite material is amorphous carbon, and the carbon layer is coated with Na ₃ MnZr(PO ₄ ) ₃ The surface of the primary particles; the shape of the secondary particles of the composite material is spherical.

2. The spherical manganese zirconium sodium phosphate/carbon composite material according to claim 1, characterized in that the material is prepared by using sodium, salt, manganese salt, zirconium salt, phosphate and carbon source as raw materials, wherein the sodium salt and the phosphate are selected from the same substance.

3. The spherical sodium zirconium manganese phosphate/carbon composite material according to claim 1, wherein the sodium salt is selected from one or a combination of sodium acetate, sodium dihydrogen phosphate and sodium citrate; the manganese salt is manganese acetate; the zirconium salt is selected from one or the combination of two of zirconium acetate, zirconium acetylacetonate, zirconium citrate, zirconium propionate and zirconium methacrylate; the phosphate is selected from one or a combination of more of sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate and ammonium phosphate; the carbon source is one or a combination of several of citric acid, sucrose and glucose.

4. The method for preparing the spherical sodium zirconium manganese phosphate/carbon composite material according to claim 1, characterized by comprising the following steps:

(1) Adding sodium salt, manganese salt, zirconium salt, phosphate and a carbon source into a certain amount of water according to the stoichiometric ratio of the chemical formula, and continuously stirring and dispersing the mixture into a uniform solution to obtain a mixed solution;

(2) Carrying out spray drying on the obtained mixed solution to quickly evaporate water to obtain a precursor;

(3) And roasting the obtained precursor in a heating furnace filled with protective gas to obtain the spherical manganese zirconium sodium phosphate/carbon composite material.

5. The method of claim 4, wherein the spray-dried spray-drying tower has a feed inlet temperature of 120 to 300 ℃.

6. The method of claim 4, wherein the protective gas is one of nitrogen, argon, a mixture of nitrogen and hydrogen, and a mixture of argon and hydrogen, the calcination temperature is 600-800 ℃, and the calcination time is 4-12h.

7. The preparation method according to claim 4, wherein the carbon content in the obtained spherical sodium zirconium manganese phosphate/carbon composite material can be regulated and controlled by changing the adding amount of the carbon source in the raw materials, and the carbon content in the composite material is 1-10wt%.

8. The use of a spherical sodium zirconium manganese phosphate/carbon composite material according to claim 1 in a sodium ion battery, wherein the spherical sodium zirconium manganese phosphate/carbon composite material is used as a positive electrode material for a sodium ion battery.

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