CN111082059A

CN111082059A - V-doped P2 type sodium ion battery positive electrode material and preparation method thereof

Info

Publication number: CN111082059A
Application number: CN201911330034.6A
Authority: CN
Inventors: 杨成浩; 邓强; 郑锋华; 钟文涛
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2019-12-20
Filing date: 2019-12-20
Publication date: 2020-04-28

Abstract

The invention discloses a V-doped P2 type sodium ion battery anode material and a preparation method thereof. The chemical formula of the positive electrode material of the sodium-ion battery is as follows: na (Na)_xMn_aM_bV_cO₂(wherein x, a, b and c are mole numbers, x is more than 0.44 and less than 1, a is more than or equal to 0.4 and less than or equal to 1, b is more than or equal to 0 and less than or equal to 0.4, c is more than 0 and less than or equal to 0.2, and M is one or more of metal ions of Ni, Co, Mg, Al, Zn, Ti, Cu and Fe). The V-doped P2 type sodium ion battery anode material is prepared by preparing a precursor by a simple sol-gel method and performing high-temperature solid-phase sintering reaction. The V-doped P2 type sodium ion battery anode material can inhibit the material from generating irreversible phase transformation, improve the conductivity and the sodium ion diffusion coefficient, and effectively improve the cycle performance, the rate capability and the safety performance of the materialThe method is low in cost, environment-friendly and easy to realize industrial large-scale production.

Description

V-doped P2 type sodium ion battery positive electrode material and preparation method thereof

Technical Field

The invention belongs to the technical field of preparation of sodium ion battery electrode materials, and particularly relates to a V-doped P2 type sodium ion battery positive electrode material and a preparation method thereof.

Background

With the rapid development of lithium ion battery technology in recent years, lithium ion batteries have been applied to various aspects of our lives, including portable devices such as mobile phones and computers, power batteries of new energy vehicles, energy storage devices of wind energy and solar power stations, and the like, and the huge energy demand makes people focus on the research of sodium ion batteries. The layered transition metal oxide is widely noticed as a positive electrode material of a sodium ion battery due to easy synthesis and high electrochemical activity, wherein the positive electrode material of the P2 type sodium ion battery is researched more due to high capacity, but irreversible phase transition can also occur in the circulation process, so that the capacity attenuation is fast, and the application of the positive electrode material of the P2 type sodium ion battery is limited.

The current methods for improving the electrochemical performance of the positive electrode material of the P2 type sodium ion battery mainly comprise surface coating and bulk phase doping. The surface coating is to coat a layer of protective film on the surface of the material, thereby preventing the anode material from directly contacting and reacting with the electrolyte and improving the stability of the material. Bulk doping, i.e. using metal ions (Al)³⁺、Mg²⁺Or Fe²⁺Etc.) to replace partial ions in the body of the anode material, thereby stabilizing the material structure, inhibiting the phase transformation problem and improving the cycle stability performance. In recent years, although there are many patents disclosing the improvement of the performance of the lithium ion battery by V doping, no report is found on the research of the positive electrode material of the P2 type sodium ion battery by V doping.

Disclosure of Invention

The invention aims to provide a V-doped P2 type sodium ion battery anode material and a preparation method thereof, which improve the preparation process of the existing sodium ion battery anode material, can inhibit the irreversible phase transformation of the material, improve the conductivity and the sodium ion diffusion coefficient, effectively improve the cycle performance, the rate capability and the safety performance of the material, and are suitable for industrial application.

The purpose of the invention is realized by the following technical scheme.

The V-doped P2 type sodium ion battery positive electrode material has a chemical formula of Na_xMn_aM_bV_cO₂Wherein x, a, b and c are mole numbers, x is more than 0.44 and less than 1, a is more than or equal to 0.4 and less than or equal to 1, b is more than or equal to 0 and less than or equal to 0.4, c is more than 0 and less than or equal to 0.2, and M is one or more of metal ions of Ni, Co, Mg, Al, Zn, Ti, Cu and Fe.

The preparation method of the V-doped P2 type sodium ion battery positive electrode material comprises the following steps:

1) according to the chemical formula Na_xMn_aM_bV_cO₂Weighing manganese salt, metal M salt and vanadium source according to the molar ratio of Mn, M and V elements, dissolving the manganese salt, the metal M salt and the vanadium source in a proper amount of water, adding 1-5 mol% of excessive sodium salt, stirring and dissolving to prepare a mixed solution;

2) heating and stirring the mixed solution obtained in the step 1), adding an additive, stirring and evaporating to dryness to obtain gel;

3) drying and crushing the gel obtained in the step 2), pre-burning in the air atmosphere, then sintering, and cooling to room temperature to obtain the V-doped P2 type sodium ion battery anode material.

Further, the sodium salt, the manganese salt and the metal M salt in the step 1) are one or more of sulfate, nitrate and acetate.

Further, the vanadium source in the step 1) is one or more of ammonium metavanadate, vanadyl sulfate and vanadyl oxalate.

Further, the additive in the step 2) is one or more of citric acid, glycol and tartaric acid; the dosage of the additive is 20-50% of the mass of the manganese salt, the metal M salt and the vanadium source.

Further, the temperature for evaporating in the step 2) is 80-100 ℃.

Further, the drying in the step 3) is vacuum drying at the temperature of 100-120 ℃.

Further, the pre-sintering in the step 3) is carried out by heating to 400-600 ℃ at a heating rate of 1-5 ℃/min and preserving the heat for 4-6 hours.

Further, in the step 3), the temperature is raised to 900-.

Compared with the prior art, the invention has the following advantages and technical effects:

1. the preparation method disclosed by the invention is simple to operate, low in cost, environment-friendly and easy to realize industrial large-scale production.

2. According to the invention, by using the V-doped P2 type sodium ion battery anode material, irreversible phase transformation of the material can be inhibited, the conductivity and the sodium ion diffusion coefficient are improved, and the cycle performance, the rate capability and the safety performance of the material are effectively improved.

Drawings

FIG. 1 shows the positive electrode material Na of the V-doped P2 type Na-ion battery obtained in example 1 of the present invention_0.65Mn_0.72Ni_0.17Co_0.1V_0.01O₂And XRD pattern of pure NaNCM material in comparative example.

FIG. 2a and FIG. 2b are respectively a positive electrode material Na of the V-doped P2 type Na-ion battery obtained in example 1 of the present invention_0.65Mn_0.72Ni_0.17Co_0.1V_0.01O₂SEM image of pure NaNCM material in comparison example.

FIG. 3a and FIG. 3b show the positive electrode material Na of the V-doped P2 type Na-ion battery obtained in example 1 of the present invention_0.65Mn_0.72Ni_0.17Co_0.1V_0.01O₂The graph is compared with the first charge and discharge curves of the pure NaNCM material in the comparative example at 0.1C and 1C rates respectively.

FIG. 4 shows the positive electrode material Na of the V-doped P2 type Na-ion battery obtained in example 1 of the present invention_0.65Mn_0.72Ni_0.17Co_0.1V_0.01O₂Compare the graph with the cycle performance curve of the pure NaNCM material in the comparative example at 1C rate.

Detailed Description

Specific embodiments of the present invention will be further described below with reference to the following examples and drawings, but the present invention is not limited thereto.

Example 1:

(1) according to the synthesis of 10g of Na_0.65Mn_0.72Ni_0.17Co_0.1V_0.01O₂And weighing manganese nitrate, nickel nitrate, cobalt nitrate and ammonium metavanadate according to the molar ratio of Mn, Ni, Co and V elements, dissolving the manganese nitrate, the nickel nitrate, the cobalt nitrate and the ammonium metavanadate in 200mL of deionized water, adding 1 mol% of excessive sodium nitrate, continuously stirring, weighing 2g of citric acid after metal salts are dissolved, adding the citric acid into the solution, stirring and evaporating at 80 ℃ to dryness, and thus obtaining the gel substance.

(2) Drying the gel obtained in the step (1) at 120 ℃ in vacuum, crushing, heating to 450 ℃ at the heating rate of 1 ℃/min in the air atmosphere for pre-sintering for 6 hours, then heating to 950 ℃ for sintering for 15 hours, and cooling to room temperature to obtain the positive electrode material Na of the V-doped P2 type sodium-ion battery_0.65Mn_0.72Ni_0.17Co_0.1V_0.01O₂。

(3) X-ray powder diffraction (XRD) analysis shows that the obtained product has the same structure with pure NaNCM, has high crystallinity, belongs to P2-type layered structure and has a space group of P6₃And/mmc (as shown in figure 1). It can be seen from the Scanning Electron Microscope (SEM) image that the material has a sheet-like morphology, and the morphology does not change before and after doping (as shown in fig. 2 a).

(4) V-doped P2 type sodium-ion battery positive electrode material Na at 25 DEG C_0.65Mn_0.72Ni_0.17Co_0.1V_0.01O₂The specific first discharge capacity of the capacitor is 156.0mAh/g at the multiplying power of 0.1C and between 1.5 and 4.2V, the specific first discharge capacity of the capacitor is 139.8mAh/g at the multiplying power of 1C (shown in figure 3 a), the specific discharge capacity of the capacitor is 115.3mAh/g after the capacitor is cycled for 100 circles at the multiplying power of 1C, and the capacity retention rate of the capacitor is 85 percent (shown in figure 4). From the above results, it was found that the positive electrode material Na of the V-doped P2 type sodium ion battery was used_0.65Mn_0.72Ni_0.17Co_0.1V_0.01O₂Stable structure, high specific capacity, good cycling stability and excellent electrochemical performance.

Example 2:

(1) according to the synthesis of 10g of Na_0.45Mn_0.66Ni_0.22Fe_0.08V_0.04O₂Manganese sulfate, nickel sulfate, ferric sulfate and vanadyl sulfate are weighed according to the molar ratio of Mn, Ni, Fe and V elements and dissolved in 250mL of deionized water, 2 mol% of excessive sodium sulfate is added, stirring is continuously carried out, after metal salts in the step are dissolved, 3g of tartaric acid is weighed, added into the solution, stirred and evaporated to dryness at 85 ℃, and the gel substance is obtained.

(2) Drying the gel obtained in the step (1) at 115 ℃ in vacuum, crushing, heating to 500 ℃ at the heating rate of 2 ℃/min in the air atmosphere for presintering for 5 hours, then heating to 925 ℃ for sintering for 16 hours, and cooling to room temperature to obtain the Na-doped P2 type sodium ion battery positive electrode material_0.45Mn_0.66Ni_0.22Fe_0.08V_0.04O₂。

(3) Activating at 25 deg.C for three times at 0.1C rate of 1.5-4.2V, performing charge-discharge cycle at 1C rate for 100 times, and doping Na as positive electrode material of P2 type sodium-ion battery with V_0.45Mn_0.66Ni_0.22Fe_0.08V_0.04O₂Stable structure, high specific capacity, good cycling stability and excellent electrochemical performance.

Example 3:

(1) according to the synthesis of 10g of Na_0.67Mn_0.7Ni_0.22V_0.08O₂Weighing manganese acetate, nickel acetate and vanadyl oxalate according to the molar ratio of Mn, Ni and V elements, dissolving the manganese acetate, the nickel acetate and the vanadyl oxalate in 150mL of deionized water, adding 3 mol% of sodium acetate in excess, continuously stirring, weighing 1g of citric acid after the metal salts are dissolved, adding the citric acid into the solution, stirring and evaporating at 90 ℃ to dryness, and obtaining the gel substance.

(2) Drying the gel obtained in the step (1) at 100 ℃ in vacuum, crushing, heating to 600 ℃ at the heating rate of 3 ℃/min in the air atmosphere for presintering for 4 hours, then heating to 900 ℃ for sintering for 18 hours, and cooling to room temperature to obtain the positive electrode material Na of the V-doped P2 type sodium-ion battery_0.67Mn_0.7Ni_0.22V_0.08O₂。

(3) Activating at 25 deg.C for three times at 0.1C rate of 1.5-4.2V, performing charge-discharge cycle at 1C rate for 100 times, and doping Na as positive electrode material of P2 type sodium-ion battery with V_0.67Mn_0.7Ni_0.22V_0.08O₂Stable structure, high specific capacity, good cycling stability and excellent electrochemical performance.

Example 4:

(1) according to the synthesis of 10g of Na_0.67Mn_0.95V_0.05O₂Weighing manganese nitrate and ammonium metavanadate according to the molar ratio of Mn and V elements, respectively dissolving the manganese nitrate and the ammonium metavanadate in 300mL of deionized water, adding 5 mol% of sodium nitrate in excess, continuously stirring, weighing 5g of citric acid after the metal salts are dissolved in the step, adding the citric acid into the solution, stirring and evaporating at 100 ℃ to dryness, and thus obtaining the gel substance.

(2) Drying the gel obtained in the step (1) at 110 ℃ in vacuum, crushing, heating to 400 ℃ at the heating rate of 5 ℃/min in the air atmosphere for presintering for 6 hours, then heating to 1000 ℃ for sintering for 12 hours, and cooling to room temperature to obtain the positive electrode material Na of the V-doped P2 type sodium-ion battery_0.67Mn_0.95V_0.05O₂。

(3) Activating at 25 deg.C for three times at 0.1C rate of 1.5-4.2V, performing charge-discharge cycle at 1C rate for 100 times, and doping Na as positive electrode material of P2 type sodium-ion battery with V_0.67Mn_0.95V_0.05O₂Stable structure, high specific capacity, good cycling stability and excellent electrochemical performance.

Comparative example:

(1) according to the synthesis of 10g of Na_0.65Mn_0.72Ni_0.17Co_0.11O₂Weighing manganese nitrate, nickel nitrate and cobalt nitrate according to the molar ratio of Mn, Ni and Co elements, respectively dissolving the manganese nitrate, the nickel nitrate and the cobalt nitrate in 200mL of deionized water, adding 1 mol% of sodium nitrate in excess, continuously stirring, weighing 2g of citric acid after the metal salts are dissolved, adding the citric acid into the solution, stirring and evaporating at 80 ℃ to dryness, and obtaining the gel substance.

(2) Drying the gel obtained in the step (1) in vacuum at 120 ℃, crushing, and carrying out air atmosphereHeating to 450 ℃ at the heating rate of 1 ℃/min for presintering for 6 hours, then heating to 950 ℃ for sintering for 15 hours, and cooling to room temperature to obtain the positive electrode material Na of the P2 type sodium-ion battery_0.65Mn_0.72Ni_0.17Co_0.11O₂。

(3) X-ray powder diffraction (XRD) analysis shows that the obtained product is a pure-phase NaNCM, belongs to a P2-type lamellar structure, and has a space group of P6₃And/mmc (as shown in figure 1). It can be seen in the Scanning Electron Microscope (SEM) image that the material exhibits a plate-like morphology (as shown in fig. 2 b).

(4) The positive electrode material Na of the P2 type sodium ion battery is used when the charge-discharge cycle is carried out at 25 ℃ and the multiplying power of 0.1C between 1.5V and 4.2V_0.65Mn_0.72Ni_0.17Co_0.11O₂The first discharge specific capacity of (1) was 148.3mAh/g, and the first discharge specific capacity at 1C rate was 134.1mAh/g (as shown in FIG. 3 b). The specific capacity after 100 cycles was 85.7mAh/g and the capacity retention rate was only 64% when charging and discharging were performed at a rate of 1C at 25 deg.C (as shown in FIG. 4).

Claims

1. a V-doped P2 type sodium ion battery positive electrode material, is characterized in that, the chemical formula of described V-doped P2 type sodium ion battery positive electrode material is Na _x Mn _a M _b V _c O ₂ , wherein x, a, b, c are the number of moles, 0.44<x<1, 0.4≤a≤1, 0≤b≤0.4, 0<c≤0.2, M is the metal ion Ni, Co, Mg, Al, Zn, Ti, Cu and Fe one or more of them.

2. the method for preparing a kind of V-doped P2 type sodium ion battery positive electrode material according to claim 1, is characterized in that, comprises the following steps:

1) according to the mol ratio of Mn, M and V elements in chemical _formula Na _x Mn _a M _b V _c O , take by weighing manganese salt, metal M salt and vanadium source and dissolve in water, add sodium salt again, stir and dissolve, and prepare to obtain mixed. solution;

2) heating and stirring the mixed solution of step 1), then adding additives, stirring and evaporating to dryness to obtain gel;

3) The gel obtained in step 2) is dried, crushed, pre-fired in an air atmosphere, then sintered, and then cooled to room temperature to obtain a V-doped P2 type sodium ion battery positive electrode material.

3. preparation method according to claim 2 is characterized in that, sodium salt, manganese salt, metal M salt described in step 1) are one or more in sulfate, nitrate and acetate.

4. preparation method according to claim 2 is characterized in that, the vanadium source described in step 1) is one or more in ammonium metavanadate, vanadyl sulfate, vanadyl oxalate.

5. preparation method according to claim 2, is characterized in that, the additive described in step 2) is one or more in citric acid, ethylene glycol and tartaric acid; The consumption of described additive is manganese salt, metal M 20 to 50% of the mass of the salt and vanadium source.

6 . The preparation method according to claim 2 , wherein the temperature of the evaporation to dryness in step 2) is 80-100° C. 7 .

7. The preparation method according to claim 2, wherein the drying in step 3) is vacuum drying at 100-120°C.

8 . The preparation method according to claim 2 , wherein the pre-firing in step 3) is heated to 400-600° C. at a heating rate of 1-5° C./min, and kept for 4-6 hours. 9 .

9 . The preparation method according to claim 2 , wherein the sintering in step 3) is heated to 900-1000° C. at a heating rate of 1-5° C./min, and kept for 12-18 hours. 10 .

10. The preparation method according to claim 2, characterized in that, in step 1), the sodium salt added is in excess of 1 mol% to 5 mol%.