Layered oxide positive electrode material of sodium ion battery and preparation method of layered oxide positive electrode material

Abstract

The invention relates to the technical field of preparation of sodium-ion battery positive electrode materials, in particular to a sodium-ion battery layered oxide positive electrode material and a preparation method thereof. The preparation method comprises the following steps: S1, adsorbing copper and iron through manganese dioxide; s2, drying and calcining the substance obtained in the step S1; s3, activating a substance in the step S2, and treating the substance through 3-carboxyl propyl trimethoxy silane; s4, treating substances in the step S3 with sodium carbonate, potassium carbonate and sodium fluoride, and evaporating; s5, carrying out tabletting treatment on the solid mixture obtained in the step S4; and S6, calcining the solid mixture subjected to tabletting treatment in the step S5 to obtain the layered oxide positive electrode material of the sodium-ion battery. According to the prepared positive electrode material, potassium ions and fluorine ions are uniformly doped, and the reversible capacity retention rate of the prepared battery is high.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of cathode materials for sodium-ion batteries, and specifically to a layered oxide cathode material for sodium-ion batteries and a preparation method thereof. Background Art

[0002] As a supplementary technology to lithium-ion batteries, sodium-ion batteries are suitable for mid- to low-end energy storage scenarios due to their rich resources and low cost advantages. Their working principle is similar to that of lithium batteries, and charge and discharge are achieved through the insertion and extraction of sodium ions. The cathode material system mainly includes three categories: layered oxides, Prussian blue compounds, and polyanionic compounds. Among them, layered oxides have become the mainstream route due to their outstanding comprehensive performance, but still face challenges such as high-voltage phase transformation, slow ion diffusion kinetics, Jahn-Teller effect, and poor air stability.

[0003] Ion doping is an effective strategy to suppress phase transformation, involving three doping sites: sodium site, transition metal site, and oxygen site. When performing ion doping, it is necessary to evenly dope the ions through grinding. However, sometimes due to the small amount of doped ions, it is difficult to evenly dope the small amount of ions into the material, resulting in blocked charge transport, increased polarization, accelerated capacity decay, and reduced reversible capacity retention rate after battery cycling. Summary of the Invention

[0004] The purpose of the present invention is to provide a layered oxide cathode material for sodium-ion batteries and a preparation method thereof to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions: A preparation method of a layered oxide cathode material for sodium-ion batteries, comprising the following steps: S1. Disperse manganese dioxide in a deionized aqueous solution of iron salt and copper salt and soak for 1 - 3 h, then add tannic acid and citric acid, and then add sodium hydroxide solution to adjust the pH to 12, and continuously react for 1 - 2 h to obtain a precipitate; S2. Filter and separate the precipitate obtained in step S1, then vacuum dry at 40°C and then calcine at 450°C for 0.5 - 1 h; S3. Soak the precipitate calcined in step S2 in hydrogen peroxide with a mass fraction of 30% for 0.2 - 0.5 h for activation, then filter, and add the product to an ethanol solution of 3 - carboxypropyltrimethoxysilane and reflux at 85°C for 5 - 8 h; S4. Filter and separate the precipitate treated in step S3, wash it with sufficient ethanol, then vacuum dry at 40°C, and then continue to put it into a deionized aqueous solution containing sodium carbonate, potassium carbonate, and sodium fluoride, and evaporate completely at 75°C to obtain a solid mixture; S5. Press the solid mixture obtained in step S4 into tablets. S6. Calcinate the solid mixture after being pressed in step S5 at 800 - 900 °C for 10 - 16 h to obtain the layered oxide cathode material for sodium-ion batteries.

[0006] Furthermore, the manganese dioxide in step S1 is mesoporous manganese dioxide; the iron salt and copper salt used in step S1 are ferric nitrate and copper nitrate respectively, and the molar ratio among the copper salt, iron salt and manganese dioxide is 0.27:0.13:0.6.

[0007] Furthermore, the molar ratio among tannic acid, citric acid and manganese dioxide in step S1 is 1:(1.5 - 2.4):(22 - 48), and the concentration of the sodium hydroxide solution is 0.5 mol / L.

[0008] Furthermore, the concentration of hydrogen peroxide in step S3 is 30 wt%, and the mass fraction of 3 - carboxypropyltrimethoxysilane is 5 wt%.

[0009] Furthermore, the molar ratio among sodium carbonate, potassium carbonate, sodium fluoride and the manganese dioxide in step S1 in step S4 is 0.66:0.01:0.1:0.6.

[0010] Furthermore, the pressure for pressing the tablets in step S5 is 10 - 15 MPa, and the pressing time is 30 - 60 s.

[0011] A layered oxide cathode material for sodium-ion batteries is prepared by the above-mentioned preparation method of the layered oxide cathode material for sodium-ion batteries.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. With the extremely strong adsorption effect of manganese dioxide on iron ions and copper ions, copper oxide and iron oxide are synthesized in the pores of manganese dioxide. When synthesizing iron oxide and copper oxide, through the action of the complexing agent, it is beneficial to form rough and porous surfaces on the formed copper oxide and iron oxide. 2. In the present invention, manganese dioxide, as the main material with the largest usage amount, serves as a loading platform. It combines with iron oxide and copper oxide successively, and then after activation and treatment with 3 - carboxypropyltrimethoxysilane, it is easy to uniformly combine with potassium ions and fluoride ions. The doping of potassium ions and fluoride ions is uniform, and the cycle stability of the battery made of the prepared cathode material is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is the process flow chart of the present invention; Figure 2 is the XRD pattern of the cathode material prepared in Example 1 of the present invention; Figure 3 SEM image of the cathode material prepared in Example 1 of the present invention; Figure 4 Charge-discharge curves of the battery assembled with the cathode material prepared in Example 1 of the present invention in the first five cycles at a current density of 0.1C; Figure 5 Cycling performance graph of the battery assembled with the cathode material prepared in Example 1 of the present invention in the first 50 cycles at a current density of 0.1C; Figure 6 XRD pattern of the cathode material prepared in Comparative Example 1 of the present invention; Figure 7 Charge-discharge curves of the battery assembled with the cathode material prepared in Comparative Example 1 of the present invention in the first five cycles at a current density of 0.1C; Figure 8 Cycling performance graph of the battery assembled with the cathode material prepared in Comparative Example 1 of the present invention in the first 50 cycles at a current density of 0.1C; Figure 9 XRD pattern of the cathode material prepared in Comparative Example 2 of the present invention; Figure 10 Charge-discharge curves of the battery assembled with the cathode material prepared in Comparative Example 2 of the present invention in the first five cycles at a current density of 0.1C; Figure 11 Cycling performance graph of the battery assembled with the cathode material prepared in Comparative Example 2 of the present invention in the first 50 cycles at a current density of 0.1C; Figure 12 XRD pattern of the cathode material prepared in Comparative Example 3 of the present invention; Figure 13 Charge-discharge curves of the battery assembled with the cathode material prepared in Comparative Example 3 of the present invention in the first five cycles at a current density of 0.1C; Figure 14 Cycling performance graph of the battery assembled with the cathode material prepared in Comparative Example 3 of the present invention in the first 50 cycles at a current density of 0.1C. Detailed implementation manners

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0015] Please refer to Figures 1 to 14 , the present invention provides: Example 1 A preparation method of a layered oxide cathode material for a sodium-ion battery, comprising the following steps: S1. Disperse 0.06 mol of manganese dioxide into a deionized aqueous solution of iron salt (iron nitrate) and copper salt (copper nitrate) and soak for 2 h. The amount of deionized water used is 35 ml, and the amounts of copper nitrate and iron nitrate used are 0.027 mol and 0.013 mol respectively. The manganese dioxide is mesoporous manganese dioxide. Then add 0.002 mol of tannic acid and 0.0036 mol of citric acid. After that, dropwise add a sodium hydroxide solution with a concentration of 0.5 mol / L to adjust the pH to 12, and continuously react for 1.5 h to obtain a precipitate; S2. After filtering and separating the precipitate obtained in step S1, vacuum dry it at 40 °C and then calcine it at 450 °C for 0.8 h; S3. First, soak the precipitate calcined in step S2 in 40 ml of hydrogen peroxide with a concentration of 30 wt% for 0.4 h for activation, then filter it. The product is then added to 30 ml of an ethanol solution of 3 - carboxypropyltrimethoxysilane with a concentration of 5 wt% and refluxed at 85 °C for 7 h; S4. After filtering and separating the precipitate treated in step S3 and washing it with sufficient ethanol, vacuum dry it at 40 °C and then continue to put it into a deionized aqueous solution containing 0.066 mol of sodium carbonate, 0.001 mol of potassium carbonate and 0.01 mol of sodium fluoride. The amount of deionized water used is 50 ml, and evaporate it completely at 75 °C to obtain a solid mixture; S5. Perform tabletting on the solid mixture obtained in step S4. The tabletting pressure is 12 MPa and the tabletting time is 50 s; S6. Calcinate the solid mixture treated by tabletting in step S5 at 850 °C for 14 h to obtain a sodium - ion battery layered oxide cathode material.

[0016] Example 2 A preparation method of a sodium - ion battery layered oxide cathode material, comprising the following steps: S1. Disperse 0.06 mol of manganese dioxide into a deionized aqueous solution of iron nitrate and copper nitrate and soak for 1 h. The amount of deionized water used is 35 ml, and the amounts of copper nitrate and iron nitrate used are 0.027 mol and 0.013 mol respectively. The manganese dioxide is mesoporous manganese dioxide. Then add 0.0027 mol of tannic acid and 0.0041 mol of citric acid. After that, dropwise add a sodium hydroxide solution with a concentration of 0.5 mol / L to adjust the pH to 12, and continuously react for 1 h to obtain a precipitate; S2. After filtering and separating the precipitate obtained in step S1, vacuum dry it at 40 °C and then calcine it at 450 °C for 0.5 h; S3. Immerse the precipitate calcined in step S2 into 40 ml of 30 wt% hydrogen peroxide solution for 0.2 h for activation, then filter. Add the product into 30 ml of ethanol solution containing 5 wt% 3 - carboxypropyltrimethoxysilane and reflux at 85 °C for 5 h; S4. Filter and separate the precipitate treated in step S3, wash it with sufficient ethanol, then dry it in vacuum at 40 °C and continue to put it into a deionized water solution containing 0.066 mol of sodium carbonate, 0.001 mol of potassium carbonate and 0.01 mol of sodium fluoride. The amount of deionized water used is 50 ml, and evaporate it completely at 75 °C to obtain a solid mixture; S5. Press the solid mixture obtained in step S4, with the pressing pressure of 10 MPa and the pressing time of 30 s; S6. Calcinate the solid mixture treated by pressing in step S5 at 800 °C for 10 h to obtain the layered oxide cathode material for sodium - ion battery.

[0017] Example 3 A preparation method of a layered oxide cathode material for sodium - ion battery, comprising the following steps: S1. Disperse 0.06 mol of manganese dioxide into a deionized water solution of iron nitrate and copper nitrate and soak for 3 h. The amount of deionized water used is 35 ml, and the amounts of copper nitrate and iron nitrate used are 0.027 mol and 0.013 mol respectively. The manganese dioxide is mesoporous manganese dioxide. Then add 0.00125 mol of tannic acid and 0.003 mol of citric acid, and then dropwise add a sodium hydroxide solution with a concentration of 0.5 mol / L to adjust the pH to 12 and continuously react for 2 h to obtain a precipitate; S2. Filter and separate the precipitate obtained in step S1, dry it in vacuum at 40 °C and then calcine it at 450 °C for 1 h; S3. Immerse the precipitate calcined in step S2 into 40 ml of 30 wt% hydrogen peroxide solution for 0.5 h for activation, then filter. Add the product into 30 ml of ethanol solution containing 5 wt% 3 - carboxypropyltrimethoxysilane and reflux at 85 °C for 8 h; S4. Filter and separate the precipitate treated in step S3, wash it with sufficient ethanol, then dry it in vacuum at 40 °C and continue to put it into a deionized water solution containing 0.066 mol of sodium carbonate, 0.001 mol of potassium carbonate and 0.01 mol of sodium fluoride. The amount of deionized water used is 50 ml, and evaporate it completely at 75 °C to obtain a solid mixture; S5. Press the solid mixture obtained in step S4, with the pressing pressure of 15 MPa and the pressing time of 60 s; S6. The solid mixture obtained after the tabletting treatment in step S5 is calcined at 900 °C for 16 h to obtain a sodium-ion battery layered oxide cathode material.

[0018] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the addition of tannic acid and citric acid in step S1 is cancelled, and the remaining steps are exactly the same as those in Example 1.

[0019] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that step S3 is completely cancelled, and the remaining steps are exactly the same as those in Example 1.

[0020] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that copper oxide, iron oxide, manganese dioxide, potassium carbonate, sodium carbonate and sodium fluoride are ground together for 5 h, and then tabletting and calcination operations are carried out to obtain a sodium-ion battery layered oxide cathode material. The molar amount of copper oxide used is the same as that of copper nitrate in Example 1, and the molar amount of iron oxide used is the same as that of iron nitrate in Example 1.

[0021] Figure 2 is the XRD pattern of the sodium-ion battery layered oxide cathode material obtained in Example 1. Each characteristic diffraction peak is clearly visible, all of which conform to the space group P63 / mmc, and there are no extra diffraction peaks in the XRD pattern, indicating that the cathode material is a P2 pure phase.

[0022] Figure 3 is the SEM image of the obtained sodium-ion battery layered oxide cathode material. Figure 3 The results show that the cathode material powder obtained in Example 1 of the present invention presents a mixed morphological feature of leaf-shaped, rod-shaped and rough and porous surface. The coexistence of multiple morphologies may balance the ion transport efficiency and structural stability of the material through a synergistic effect.

[0023] A total of 6 groups of sodium-ion battery layered oxide cathode materials were prepared through Examples 1-3 and Comparative Examples 1-3 above. These 6 groups of sodium-ion battery layered oxide cathode materials were respectively mixed with a conductive additive (Super P) and a binder (polyvinylidene fluoride) according to a mass ratio of 7:2:1, and an appropriate amount of solvent N-methylpyrrolidone (NMP) was added. After stirring evenly, it was coated on an aluminum foil and dried in a vacuum oven at 70 °C for 12 h, and then punched into a positive electrode sheet with a diameter of 12 mm. A CR2032 button battery was assembled in an argon glove box, where the electrolyte was a mixed solution of propylene carbonate (PC) containing 1 M NaClO4 and 5% fluoroethylene carbonate (FEC), the sodium metal sheet was used as the negative electrode, and glass fiber GF / F (Whatman) was used as the separator.

[0024] The above-mentioned button battery was subjected to charge-discharge tests at room temperature on a Neware battery test system.

[0025] Figure 4 It is the charge-discharge curve diagram of the first five cycles of the obtained button battery at a current density of 0.1C; Figure 4 The results in show that the cathode material prepared in Example 1 has first charge and discharge capacities of 147.27 mAh / g and 136.1 mAh / g respectively within the test voltage range of 1.5 - 4.5 V (vs. Na + / Na). Figure 5 It is the cycle performance diagram of the first 50 cycles of the sodium-ion battery assembled with the cathode material prepared in Example 1 at a current density of 0.1C. As can be seen from Figure 5 it, the reversible capacity retention rate of the material after 50 cycles is as high as 98.52%, indicating its excellent electrochemical reversibility.

[0026] Figure 6 It is the XRD pattern of the layered oxide cathode material of the sodium-ion battery obtained in Comparative Example 1. Each characteristic diffraction peak is clearly visible and all conform to the space group P63 / mmc, indicating that the cathode material is of the P2 phase. Figure 7 It is the charge-discharge curve diagram of the first five cycles of the obtained button battery at a current density of 0.1C; the cathode material obtained in Comparative Example 1 has first charge and discharge capacities of 169.27 mAh / g and 165.1 mAh / g respectively within the test voltage range of 1.5 - 4.5 V (vs. Na + / Na). Figure 8 It is the cycle performance diagram of the first 50 cycles of the sodium-ion battery assembled with the cathode material prepared in Comparative Example 1 at a current density of 0.1C. The results show that the reversible capacity retention rate of the material after 50 cycles is 64.16%, indicating that its cycle stability is poorer than that of Example 1.

[0027] Figure 9 It is the XRD pattern of the layered oxide cathode material of the sodium-ion battery obtained in Comparative Example 2. Each characteristic diffraction peak is clearly visible and all conform to the space group P63 / mmc, indicating that the cathode material is of the P2 phase. Figure 10 It is the charge-discharge curve diagram of the first five cycles of the obtained button battery at a current density of 0.1C; as shown in the appendix Figure 10 it, the cathode material obtained in Comparative Example 2 has first charge and discharge capacities of 174.63 mAh / g and 172.7 mAh / g respectively within the test voltage range of 1.5 - 4.5 V (vs. Na + / Na). Figure 11Cycling performance graph of the sodium-ion battery assembled with the cathode material prepared in Comparative Example 2 at a current density of 0.1C. The results show that the reversible capacity retention rate after 50 cycles of the material is 60.55%, and the cycling stability is poorer than that of Example 1.

[0028] Figure 12 XRD pattern of the layered oxide cathode material of the sodium-ion battery obtained in Comparative Example 3. Each characteristic diffraction peak is clearly visible, all conforming to the space group P63 / mmc, and there are no extra diffraction peaks in the XRD pattern, indicating that the cathode material is a pure P2 phase. Figure 13 Charge-discharge curves of the obtained button battery in the first five cycles at a current density of 0.1C; as Figure 13 shown, the initial charge and discharge capacities of the cathode material obtained in Comparative Example 3 are 197.71 mAh / g and 186.55 mAh / g respectively in the test voltage range of 1.5 - 4.5 V (vs. Na + / Na). Figure 14 Cycling performance graph of the sodium-ion battery assembled with the cathode material prepared in Comparative Example 3 at a current density of 0.1C. The results show that the reversible capacity retention rate after 50 cycles of the material is 59.94%, and the cycling stability is poorer than that of Example 1.

[0029] It can be seen from the data of Example 1 and Comparative Examples 1 - 3 above that the cycling stability of Example 1 has been greatly improved compared with Comparative Examples 1 - 3.

[0030] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a layered oxide cathode material for a sodium-ion battery, characterized in that It includes the following steps: S1. Disperse manganese dioxide into the deionized aqueous solution of iron salt and copper salt and soak for 1 - 3 h, then add tannic acid and citric acid, and then add sodium hydroxide solution to adjust the pH to 12, and continuously react for 1 - 2 h to obtain a precipitate; S2. Filter and separate the precipitate obtained in step S1, then vacuum dry at 40 °C and then calcine at 450 °C for 0.5 - 1 h; S3. Soak the precipitate calcined in step S2 in hydrogen peroxide with a mass fraction of 30% for 0.2 - 0.5 h for activation, then filter, and add the product to the ethanol solution of 3 - carboxypropyltrimethoxysilane and reflux at 85 °C for 5 - 8 h; S4. Filter and separate the precipitate treated in step S3, wash it with sufficient ethanol, then vacuum dry at 40 °C and then continue to put it into the deionized aqueous solution containing sodium carbonate, potassium carbonate and sodium fluoride, and evaporate completely at 75 °C to obtain a solid mixture; S5. Perform tabletting treatment on the solid mixture obtained in step S4; S6. Calcinate the solid mixture after tabletting treatment in step S5 at 800 - 900 °C for 10 - 16 h to obtain a sodium-ion battery layered oxide cathode material.

2. The preparation method of the layered oxide cathode material for a sodium ion battery according to claim 1, characterized in that, The manganese dioxide in step S1 is mesoporous manganese dioxide; the iron salt and copper salt used in step S1 are ferric nitrate and copper nitrate respectively, and the molar ratio of copper salt, iron salt and manganese dioxide is 0.27:0.13:0.

6.

3. The preparation method of the layered oxide cathode material for a sodium ion battery according to claim 1, characterized in that, In step S1, the molar ratio of tannic acid, citric acid and manganese dioxide is 1:(1.5 - 2.4):(22 - 48), and the concentration of the sodium hydroxide solution is 0.5 mol / L.

4. The preparation method of the layered oxide cathode material for a sodium-ion battery according to claim 1, characterized in that, In step S3, the concentration of hydrogen peroxide is 30 wt%, and the mass fraction of 3 - carboxypropyltrimethoxysilane is 5 wt%.

5. The preparation method of the layered oxide cathode material for a sodium ion battery according to claim 1, characterized in that, In step S4, the molar ratio of sodium carbonate, potassium carbonate, sodium fluoride and manganese dioxide in step S1 is 0.66:0.01:0.1:0.

6.

6. The preparation method of the layered oxide cathode material for a sodium ion battery according to claim 1, wherein, In step S5, the pressure for tabletting is 10 - 15 MPa, and the tabletting time is 30 - 60 s.

7. A layered oxide cathode material for a sodium-ion battery, characterized in that, It is prepared by the preparation method of the sodium-ion battery layered oxide cathode material as described in any one of claims 1 - 6.

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