CN114068906B - Deposition type sodium iron phosphate positive electrode material and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of sodium-ion batteries, and discloses a deposition-type iron phosphate sodium cathode material and its preparation method and application. Its chemical formula is NaFePO ₄ ‑xB ₂ O ₃ @A, x=0.001‑0.3; A is Zn, At least one of nano oxides of Fe, Cu, Ni, Mn, Co, Cr, Ti, Al, Mo, Zr or Ag elements. The battery prepared by the deposition type sodium iron phosphate positive electrode material of the present invention has short sodium ion diffusion distance and faster transmission rate during charge and discharge; boron oxide and nano oxide in the deposition type sodium iron phosphate positive electrode material; boron oxide can reduce the charging and discharging process The degree of change in the structure can improve the conductivity of the sodium iron phosphate cathode material and improve the electrochemical performance; nano-oxides can effectively inhibit the shuttle effect in the sodium iron phosphate cathode material, and correspondingly improve the recycling of the sodium iron phosphate cathode material performance.

Description

A kind of deposition type ferric phosphate positive electrode material and its preparation method and application

technical field

The invention belongs to the technical field of sodium ion batteries, and in particular relates to a deposition type ferric phosphate positive electrode material and a preparation method and application thereof.

Background technique

The materials of sodium-ion batteries and lithium-ion batteries have similar structures. Compared with lithium-ion batteries, sodium-ion batteries have unique advantages in terms of resources, safety, and cycle life. Therefore, sodium-ion batteries will be a reasonable alternative to lithium-ion batteries. Solutions, especially in the direction of non-mobile battery applications, such as battery storage power stations, charging stations in service areas, etc., but replacing lithium-ion with sodium-ion batteries is not a small problem.

In view of the larger mass and radius of sodium ions, higher standard potential and lower electronegativity, the voltage of sodium ion batteries is lower than that of corresponding lithium ions, so that the quality and energy density of sodium ion batteries are not as good as lithium ion batteries, which restricts its Become the main factor to replace lithium-ion batteries. One of the key parts to improve the performance of sodium-ion batteries is the cathode material, which is the core element that directly affects the electrochemical performance of sodium-ion batteries.

At present, among the electrode materials of sodium ion batteries studied, the structure of the sodium iron phosphate cathode material is not easy to change, so during charging and discharging, the sodium ion deintercalation process is limited by the lattice structure, lattice expansion and collapse. Small, so the stability and cycle performance of the battery are higher; at the same time, the sodium iron phosphate cathode material has a specific regular space shape, so the effect of increasing the energy density by depositing oxides is more obvious.

Therefore, there is an urgent need to provide a method for preparing a deposition-type sodium iron phosphate cathode material, which provides the basis and technical support for the preparation of high-performance sodium-ion batteries and the practical application of sodium-ion batteries.

Contents of the invention

The present invention aims to solve at least one of the technical problems in the above-mentioned prior art. For this reason, the present invention proposes a deposited type iron phosphate positive electrode material and its preparation method and application. The deposited type iron phosphate positive electrode material has good recycling performance.

To achieve the above object, the present invention adopts the following technical solutions:

A depositional type iron phosphate anode material, the chemical formula is NaFePO ₄ -xB ₂ O ₃ @A, x=0.001-0.3; said A is Zn, Fe, Cu, Ni, Mn, Co, Cr, Ti, Al , Mo, Zr or at least one of nano-oxides of Ag elements.

A method for preparing a deposition type iron phosphate anode material, comprising the following steps:

(1) Mix sodium source, phosphorus source, ferrous source, boron source and complexing agent, react, add alkali to adjust pH, separate solid and liquid, take liquid phase and concentrate to obtain gel;

(2) heat-treating and ball-milling the gel to obtain sodium iron phosphate NaFePO ₄ -xB ₂ O ₃ , x=0.001-0.3;

(3) A is purged the sodium iron phosphate NaFePO _4-x B ₂ O ₃ in the form of gas to obtain a deposition type sodium iron phosphate; the A is Zn, Fe, Cu, Ni, Mn, Co, Cr, Ti , at least one of nano-oxides of Al, Mo, Zr or Ag elements.

Preferably, in step (1), the sodium source is at least one of sodium hydroxide, sodium formate, sodium acetate, sodium oxalate, sodium phosphate, sodium borate or sodium citrate.

Preferably, in step (1), the phosphorus source is at least one of phosphoric acid, sodium phosphate, ferric phosphate, ferrous phosphate, ammonium phosphate, ammonium dihydrogen phosphate, ferric phosphate or ammonium hydrogen phosphate.

Preferably, in step (1), the boron source is at least one of boron oxide, boric acid, sodium borate or iron borate.

Preferably, in step (1), the ferrous source is at least one of ferrous hydroxide, ferrous phosphate, ferrous oxalate or ferrous acetate.

Preferably, in step (1), the complex in the complexing agent is at least one of citric acid, oxalic acid or lactic acid.

Preferably, in step (1), the molar ratio of sodium, phosphate, iron, and boron in the sodium source, phosphorus source, ferrous source, and boron source is (0.01-110): (0.01-120): (0.01 -110): (0.001-30).

Preferably, in step (1), the mass percentage of the complex in the complexing agent is 0.1-40w%.

Preferably, in step (2), the alkali is at least one of sodium hydroxide, ferrous hydroxide, and ammonia water.

Preferably, in step (2), the atmosphere of the ball mill is an inert atmosphere.

Further preferably, the inert atmosphere is at least one of argon, helium, neon or xenon.

Preferably, in step (3), the gas flow for purging is 30-200 mL/min.

A battery, comprising the deposition type ferric phosphate positive electrode material.

Compared with the prior art, the beneficial effects of the present invention are as follows:

1. The sodium ion diffusion distance is short and the transmission rate is faster when the battery prepared by the deposition type sodium iron phosphate cathode material of the present invention is charged and discharged; boron oxide and nano oxide in the deposition type sodium iron phosphate cathode material; The degree of structural change during the discharge process improves the conductivity of the sodium iron phosphate cathode material and improves the electrochemical performance; nano-oxides can effectively inhibit the shuttle effect existing in the sodium iron phosphate cathode material, and correspondingly improve the performance of the sodium iron phosphate cathode material. Recycling performance.

2. In the preparation method of the present invention, the NaFePO ₄ -xB ₂ O ₃ positive electrode material prepared by introducing boron oxide is prepared into a battery with short diffusion distance and faster transmission rate of sodium ions during charging and discharging; in Fig. 2, NaFePO _4-3.86 The substrate surface of B ₂ O ₃ @ZnO obtains a dense film of about 15nm, which improves the Coulombic efficiency of the sodium iron phosphate cathode material, which is close to 100%.

3. the present invention uses nano-oxide to deposit sodium iron phosphate, because nano-oxide not only has higher electrical conductivity and high chemical stability, and with respect to nickel, cobalt, manganese etc., part metal (such as Al, Zn , Cu, Fe, Ti) reserves are large, and the prepared nano-oxides have a large amount of preparation and are non-toxic, so it has a positive role in promoting the improvement of sodium iron phosphate cathode materials and is conducive to the commercial application of sodium iron phosphate cathode materials.

Description of drawings

Fig. 1 is the flowchart of embodiment 1 of the present invention;

Fig. 2 is a TEM image of the ZnO deposition type sodium iron phosphate prepared in Example 1 of the present invention.

Detailed ways

The conception and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments, so as to fully understand the purpose, features and effects of the present invention. Apparently, the described embodiments are only some of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative efforts belong to The protection scope of the present invention.

Example 1

The chemical formula of the deposited sodium iron phosphate cathode material in this embodiment is NaFePO ₄ -0.14B ₂ O ₃ @ZnO.

The preparation method of the deposition type sodium iron phosphate cathode material of the present embodiment, the specific steps are as follows:

(1) Synthetic gel: Dissolve 65g sodium hydroxide, 173g ammonium dihydrogen phosphate, and 8.7g boric acid respectively, mix them again, add 215.9g ferrous oxalate, the molar ratio of sodium, phosphoric acid, ferrous and boron is 1.63: 1.5:1.5:0.14, add 5.17w% 0.8L citric acid solution, and control the temperature at about 55°C, add ammonia dropwise and stir to control the pH at 8.38, mix, age for 6h and 4min, remove the slag, and obtain a gel .

(2) Heat treatment: Heating the gel in a He atmosphere at 530°C for 7h4min, then ball milling in a He atmosphere with a ball mill for 8h26min to obtain sodium iron phosphate NaFePO ₄ -0.14B ₂ O ₃ .

(3) ZnO deposition: put 80gNaFePO ₄ -0.14B ₂ O ₃ into the deposition reactor, fill with N ₂ to exhaust, heat to 60°C, pass in N ₂ -H ₂ at 60mL/min for purging, 0.97g nano ZnO was loaded by He and reacted for 57min. The synthesized ZnO was washed with NaFePO ₄ -0.14B ₂ O ₃ and dried at 80°C for 2h to obtain ZnO deposited NaFePO ₄ -0.14B ₂ O ₃ @ZnO.

Fig. 2 is a TEM image of NaFePO ₄ -0.14B ₂ O ₃ @ZnO prepared in Example 1 of the present invention.

Example 2

The chemical formula of the deposited sodium iron phosphate cathode material in this embodiment is NaFePO ₄ -0.23B ₂ O ₃ @ZnO.

The preparation method of the deposition type sodium iron phosphate cathode material of the present embodiment, the specific steps are as follows:

(1) Synthetic gel: Dissolve 88g sodium hydroxide, 242g ammonium dihydrogen phosphate, and 12.2g boric acid respectively, then mix, add 302.2g ferrous oxalate, the molar ratio of sodium, phosphoric acid, ferrous and boron is 2.21: 2.1:2.1:0.23, add 6.20w% 1L citric acid solution, and control the temperature at about 55°C, add ammonia dropwise and stir to control the pH at 8.37, mix, age for 6h4min, remove slag, and obtain a gel.

(2) Heat treatment: heat the gel in a He atmosphere at 560°C for 6h30min, and then use a ball mill for 8h19min in a He atmosphere to obtain sodium iron phosphate NaFePO ₄ -0.23B ₂ O ₃ .

(3) ZnO deposition: put 80gNaFePO ₄ -0.23B ₂ O ₃ into the deposition reactor, fill with N _{2 and} exhaust, heat to 65°C, and purge with N ₂ -H ₂ at 75mL/min, 1.22g nano ZnO was loaded by He and reacted for 62min. The synthesized ZnO was washed with NaFePO ₄ -0.23B ₂ O ₃ and dried at 80°C for 2h to obtain ZnO deposited NaFePO ₄ -0.23B ₂ O ₃ @ZnO.

Example 3

The chemical formula of the deposited sodium iron phosphate cathode material in this embodiment is NaFePO ₄ -0.05B ₂ O ₃ @CuO.

The preparation method of the deposition type sodium iron phosphate cathode material of the present embodiment, the specific steps are as follows:

(1) Synthetic gel: Dissolve 27g sodium citrate, 34.5g ammonium dihydrogen phosphate, and 4.9g boric acid respectively, then mix, add 43.2g ferrous oxalate, the molar ratio of sodium, phosphoric acid, ferrous and boron is 0.315 : 0.3: 0.3: 0.05, add 1L of oxalic acid solution with a mass fraction of 4.03w%, and control the temperature at about 55°C, add ammonia dropwise and stir to control the pH at 8.72, mix, age for 6h4min, remove slag, and obtain a gel .

(2) Heat treatment: Heating the gel in a He atmosphere at 480°C for 8.0h44min, and then ball milling in a He atmosphere for 8h34min to obtain sodium iron phosphate NaFePO ₄ -0.05B ₂ O ₃ .

(3) CuO deposition: put 100gNaFePO ₄ -0.05B ₂ O ₃ into the deposition reactor, fill with N ₂ to exhaust, heat to 60°C, and purge with N ₂ -H ₂ at 75mL/min, 0.79g nano CuO was loaded by He and reacted for 61min. The synthesized CuO was deposited with NaFePO ₄ -0.05B ₂ O ₃ and washed with NaFePO 4 -0.05B 2 O 3 , and dried at 80°C for 2h to obtain CuO-deposited NaFePO ₄ -0.05B ₂ O ₃ @CuO.

Example 4

The chemical formula of the deposited sodium iron phosphate cathode material in this embodiment is NaFePO ₄ -0.16B ₂ O ₃ @CuO.

The preparation method of the deposition type sodium iron phosphate cathode material of the present embodiment, the specific steps are as follows:

(1) Synthesis of gel: Dissolve 108g of sodium citrate, 138g of ammonium dihydrogen phosphate, and 15.7g of boric acid respectively, then mix, add 172g of ferrous oxalate, and the molar ratio of sodium, phosphoric acid, ferrous and boron is 1.26:1.2 : 1.2: 0.16, add 1L of oxalic acid solution with a mass fraction of 5.49w%, and control the temperature at about 60°C, add ammonia dropwise and stir to control the pH at 8.57, mix, age for 6h4min, remove slag, and obtain a gel.

(2) Heat treatment: heat the gel in a He atmosphere at 440°C for 10h12min, and then use a ball mill for 8h17min in a He atmosphere to obtain sodium iron phosphate NaFePO ₄ -0.16B ₂ O ₃ .

(3) CuO deposition: put 100gNaFePO ₄ -0.16B ₂ O ₃ into the deposition reactor, fill with N ₂ to exhaust, heat to 65°C, and purge with N ₂ -H ₂ at 80mL/min, 1.27g nano CuO was loaded by He and reacted for 66 minutes. The synthesized CuO was deposited with NaFePO ₄ -0.16B ₂ O ₃ and washed with NaFePO 4 -0.16B 2 O 3 , and dried at 80°C for 2 hours to obtain CuO deposited NaFePO ₄ -0.16B ₂ O ₃ @CuO.

Comparative example 1

The preparation method of the sodium iron phosphate cathode material of this comparative example, concrete steps are as follows:

The difference from Example 1 is that in step (1), 63g of sodium hydroxide and 173g of ammonium dihydrogen phosphate are dissolved respectively, and then mixed, and 215.9g of ferrous oxalate is added, and the molar ratio of sodium, phosphoric acid, and ferrous is 1.58:1.5 : 1.5, adding 5.17w% 0.8L citric acid solution, finally obtained NaFePO ₄ .

Comparative example 2

The preparation method of the sodium iron phosphate cathode material of this comparative example, concrete steps are as follows:

(1) Synthetic gel: Dissolve 65g sodium hydroxide, 173g ammonium dihydrogen phosphate, and 8.7g boric acid respectively, mix them again, add 215.9g ferrous oxalate, the molar ratio of sodium, phosphoric acid, ferrous and boron is 1.63: 1.5:1.5:0.14, add 5.17w% 0.8L citric acid solution, and control the temperature at about 55°C, add ammonia dropwise and stir to control the pH at 8.38, mix, age for 6h4min, remove slag, and obtain a gel.

(2) Heat treatment: Heating the gel in a He atmosphere at 530°C for 7h17min, and then ball milling in a He atmosphere with a ball mill for 8h to obtain sodium iron phosphate NaFePO ₄ -0.14B ₂ O ₃ .

Test example:

Dissolve the positive electrode material, carbon black conductive agent and polytetrafluoroethylene in Example 1-4 and Comparative Example 1-2 in deionized water at a mass ratio of 80:15:5 to form a slurry, and then coat A pole piece was prepared on the current collector, and the pole piece was dried in a drying oven at 65°C for 8h36min. The sodium flake was used as the counter electrode, the electrolyte was 1.2 mol/L NaClO ₄ , and Celgard2400 was used as the diaphragm, and the battery was assembled in a vacuum glove box under an argon atmosphere. The cycle performance is tested with an electrochemical workstation, the current density of the test is 250mA g ^-1 , the charge and discharge range is 2.5-3.0V, and the test is performed at a rate of 0.5C.

Table 1 embodiment 1-4 and comparative example 1-2 data

It can be seen from Table 1 that after 300 cycles, the Coulombic efficiencies of Examples 1 and 3 can reach 99.9, and the first discharge specific capacities of Examples 1-4 are as high as 114.5mAh·g ^-1 , 118.9mAh·g ^-1 , 115.4mAh·g ^-1 , 117.8mAh·g ^-1 , while the discharge specific capacities of Comparative Example 1 and Comparative Example 2 are 90.6mAh·g ^-1 and 92.3mAh·g ^-1 , which are much smaller than the examples of the present invention.

The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned embodiments, and within the scope of knowledge of those of ordinary skill in the art, various modifications can be made without departing from the spirit of the present invention. Variety. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other if there is no conflict.

Claims (10)

1. A deposition type sodium iron phosphate positive electrode material is characterized in that the chemical formula of the deposition type sodium iron phosphate positive electrode material is NaFePO ₄ -xB ₂ O ₃ @ a, x=0.001-0.3; the A is at least one of Zn, fe, cu, ni, mn, co, cr, ti, al, mo, zr or nano oxides of Ag element; the precipitated sodium iron phosphate is prepared by precipitating sodium iron phosphate using a nano oxide.

2. The method for preparing the deposition type sodium iron phosphate anode material as claimed in claim 1, which is characterized by comprising the following steps:

(1) Mixing a sodium source, a phosphorus source, a ferrous source, a boron source and a complexing agent, reacting, adding alkali to adjust pH, performing solid-liquid separation, and concentrating a liquid phase to obtain a gel;

(2) Performing heat treatment and ball milling on the gel to obtain sodium iron phosphate NaFePO ₄ -xB ₂ O ₃ ，x＝0.001-0.3；

(3) Purging A as a gas of the sodium iron phosphate NaFePO ₄ -xB ₂ O ₃ Obtaining deposition type sodium iron phosphate; the A is at least one of Zn, fe, cu, ni, mn, co, cr, ti, al, mo, zr or nano oxides of Ag element.

3. The method according to claim 2, wherein in the step (1), the sodium source is at least one of sodium hydroxide, sodium formate, sodium acetate, sodium oxalate, sodium phosphate, sodium borate, or sodium citrate.

4. The method according to claim 2, wherein in the step (1), the phosphorus source is at least one of phosphoric acid, sodium phosphate, iron phosphate, ferrous phosphate, ammonium phosphate, monoammonium phosphate, iron phosphate, or diammonium phosphate.

5. The method of claim 2, wherein in step (1), the boron source is at least one of boron oxide, boric acid, sodium borate, or iron borate.

6. The method of claim 2, wherein in step (1), the ferrous source is at least one of ferrous hydroxide, ferrous phosphate, ferrous oxalate, or ferrous acetate.

7. The method according to claim 2, wherein in the step (1), the molar ratio of sodium, phosphate, iron and boron in the sodium source, phosphorus source, ferrous source and boron source is (0.01-110): (0.01-120): (0.01-110): (0.001-30).

8. The method of claim 2, wherein in step (1), the complex in the complexing agent is at least one of citric acid, oxalic acid, or lactic acid.

9. The method according to claim 2, wherein in the step (3), the loading amount of A is NaFePO ₄ -xB ₂ O ₃ 0.0001-0.1% by mass.

10. A battery comprising the deposited sodium iron phosphate positive electrode material of claim 1.

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