A precursor of a cathode material for a sodium-ion battery, a preparation method thereof, and applications

Abstract

The present invention discloses a precursor of a sodium-ion battery cathode material, a preparation method thereof and an application. The precursor of the sodium-ion battery cathode material includes a layered hydroxide precursor and a coating layer coated on at least a part of the surface of the layered hydroxide precursor; wherein, the coating layer is a Co-doped YTiTaO6 material or a Co-doped YTiTaO6 composite SrRuO3 material. In the present invention, Co is used to dope the YTiTaO6 material; the doping of Co can introduce more free electrons into the lattice without destroying the crystal structure of YTiTaO6, thereby significantly improving the conductivity of YTiTaO6; therefore, when the Co-doped YTiTaO6 material is used as the coating layer of the precursor of the sodium-ion battery cathode material, the electrochemical performance of the sodium-ion battery can be effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium-ion batteries, and particularly relates to a precursor of a cathode material for a sodium-ion battery, a preparation method thereof, and an application thereof. Background Art

[0002] In the field of energy storage, sodium-ion batteries have gradually become an important alternative to lithium-ion batteries due to their abundant raw materials, low cost, and environmental friendliness. The cathode material of a sodium-ion battery is a key factor affecting the battery performance. Currently, the commonly used cathode materials for sodium-ion batteries mainly include layered oxides, polyanion compounds, and Prussian blue compounds, etc. Among them, layered oxides are the most studied type in the current cathode materials for sodium-ion batteries due to their simple synthesis and excellent performance. However, the existing layered oxide materials generally have problems such as insufficient conductivity, unstable structure, and poor corrosion resistance, resulting in defects such as low specific capacity, poor cycle stability, and short service life in the sodium-ion batteries prepared therefrom. Summary of the Invention

[0003] The purpose of the present invention is to provide a precursor of a cathode material for a sodium-ion battery with good conductivity and stable structure, a preparation method thereof, and an application thereof.

[0004] In the first aspect, the present invention provides a precursor of a cathode material for a sodium-ion battery, and adopts the following technical solution:

[0005] A precursor of a cathode material for a sodium-ion battery, comprising a layered hydroxide precursor and a coating layer coated on at least a part of the surface of the layered hydroxide precursor; wherein, the coating layer is Co-doped YTiTaO 6 material or Co-doped YTiTaO 6 composite SrRuO 3 material.

[0006] Preferably, in the Co-doped YTiTaO 6 , the molar ratio of Y, Ti, Co, and Ta is 1:1 - 0.75x:x:1, and 0.01 ≤ x ≤ 0.1.

[0007] Preferably, in the Co-doped YTiTaO 6 composite SrRuO 3 material, the mass ratio of Co-doped YTiTaO 6 to SrRuO 3 is (1~3):(1~3).

[0008] Preferably, the mass of the coating layer is 1~20% of the mass of the layered hydroxide precursor.

[0009] Preferably, the layered hydroxide precursor is one of nickel-iron-copper-manganese layered hydroxide, copper-iron-manganese layered hydroxide, nickel-manganese-copper layered hydroxide, and nickel-zinc-iron-manganese layered hydroxide.

[0010] More preferably, the layered hydroxide is nickel-iron-manganese layered hydroxide or copper-iron-manganese layered hydroxide

[0011] Even more preferably, the layered hydroxide precursor is Ni x Fe y Mn z (OH) 2 , where 0.3 ≤ x ≤ 0.8, 0 < y ≤ 0.4, 0 < z ≤ 0.4, and x + y + z = 1; or Cu a Fe b Mn c (OH) 2 , where 0.1 ≤ a ≤ 0.5, 0 ≤ b ≤ 0.4, 0 ≤ c ≤ 0.6, and a + b + c = 1.

[0012] In a second aspect, the present invention provides a method for preparing a precursor of a cathode material for a sodium-ion battery, comprising the following steps:

[0013] S1: Take a yttrium source, a titanium source, a cobalt source, a tantalum source, and a complexing agent, add them to water, stir evenly, heat to evaporate to dryness, and further dry to obtain a powder; pre-burn the powder, and then raise the temperature for calcination to obtain Co-doped YTiTaO 6 powder;

[0014] S2: Disperse the Co-doped YTiTaO 6 powder or a mixed powder composed of the Co-doped YTiTaO 6 powder and SrRuO 3 powder in an alcohol solvent to obtain a dispersion; disperse the layered hydroxide precursor in the dispersion, stir to evaporate to dryness to obtain a solid; after drying the solid, heat it under a protective atmosphere and keep it warm to obtain a precursor of a cathode material for a sodium-ion battery.

[0015] Preferably, in step S1, the yttrium source is one or more of yttrium nitrate, yttrium chloride, and yttrium acetate;

[0016] the titanium source is one or more of tetrabutyl titanate, titanium nitrate, titanium sulfate, and titanium oxysulfate;

[0017] the cobalt source is one or more of cobalt nitrate, cobalt sulfate, cobalt chloride, and cobalt acetate;

[0018] the tantalum source is one or more of ethoxytantalum, ammonium tantalate, and sodium tantalate;

[0019] The yttrium source, titanium source, cobalt source, and tantalum source are added according to a molar ratio of Y, Ti, Co, and Ta of 1:1 - 0.75x:x:1, where 0.01 ≤ x ≤ 0.1.

[0020] Preferably, in the step S1, the complexing agent is one or more of citric acid, urea, and polyethylene glycol, and the molar ratio of the complexing agent to the total molar number of Y, Ti, Co, and Ta ions in the yttrium source, titanium source, cobalt source, and tantalum source is 1 - 2:1.

[0021] Preferably, in the step S1, the heating and evaporation - drying temperature is 80 - 100 °C; the drying temperature is 80 - 150 °C, and the drying time is 8 - 12 h.

[0022] Preferably, in the step S1, the pre - calcination temperature is 400 - 600 °C, and the pre - calcination time is 5 - 8 h; the calcination temperature is 900 - 1300 °C, and the calcination time is 8 - 12 h.

[0023] Preferably, in the step S2, the addition amount of the Co - doped YTiTaO 6 powder is 1 - 10 wt% of the addition amount of the layered hydroxide precursor; the addition amount of the SrRuO 3 powder is 1 - 10 wt% of the addition amount of the layered hydroxide precursor.

[0024] Preferably, in the step S2, the alcohol solvent is anhydrous ethanol.

[0025] Preferably, in the step S2, the stirring and evaporation - drying temperature is 80 - 150 °C; the drying temperature is 100 - 120 °C, and the drying time is 8 - 12 h.

[0026] Preferably, in the step S2, the heat - preservation temperature is 200 - 400 °C, and the heat - preservation time is 0.5 - 5 h.

[0027] In the third aspect, the present invention provides a cathode material for a sodium - ion battery, which is prepared by sintering after mixing the aforementioned cathode material precursor for a sodium - ion battery with a sodium source.

[0028] Preferably, the sodium source is one or more of sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium acetate, and sodium oxalate, and more preferably sodium carbonate.

[0029] Preferably, the sodium - mixing ratio of the cathode material precursor for a sodium - ion battery to the sodium source is 1 - 1.1.

[0030] The sodium - mixing ratio is the ratio of the molar number of Na to the total molar number of metal elements in the cathode material precursor for a sodium - ion battery; that is, if the cathode material precursor for a sodium - ion battery is Ni x Fe y Mn z (OH)2 , the mixing sodium ratio is the ratio of the number of moles of Na to the total number of moles of Ni, Fe, and Mn.

[0031] Preferably, the sintering temperature is 700 - 950 °C and the sintering time is 15 - 28 h.

[0032] Fourthly, the present invention provides a sodium-ion battery, including the aforementioned sodium-ion battery cathode material.

[0033] Advantages of the present invention:

[0034] 1) YTiTaO 6 has excellent structural stability and corrosion resistance. Coating it on the sodium battery material precursor can reduce the decomposition and structural damage of the cathode material during cycling and avoid the corrosion of the cathode material by the electrolyte. However, YTiTaO 6 has poor conductivity. Therefore, when used as the coating layer of the sodium-ion battery cathode material precursor, the improvement of the electrochemical performance of the sodium-ion battery is very limited. In the present invention, Co is used to dope the YTiTaO 6 material; the doping of Co can introduce more free electrons into the crystal lattice without destroying the YTiTaO 6 crystal structure, thereby significantly improving the conductivity of YTiTaO 6 ; therefore, when the Co-doped YTiTaO 6 material is used as the coating layer of the sodium-ion battery cathode material precursor, the electrochemical performance of the sodium-ion battery can be effectively improved.

[0035] 2) In the present invention, the Co-doped YTiTaO 6 composite SrRuO 3 material is used as the coating layer of the sodium-ion battery cathode material precursor, mainly because the Co-doped YTiTaO 6 has excellent conductivity and structural stability, which can significantly improve the overall conductivity of the battery material, while SrRuO 3 can be used as a conductive strengthening layer to further optimize the electronic conductivity of the battery, form an effective conductive network, promote the rapid migration of sodium ions, and provide a stable reaction interface, thereby improving the stability and electrochemical performance of the sodium-ion battery as a whole. Compared with the single YTiTaO 6 or SrRuO 3 material, the composite coating solves the problem of insufficient electrochemical activity that may exist in the single coating.

[0036] 3) In the present invention, the Co-doped YTiTaO 6 composite SrRuO 3The material can form a good bonding interface with the layered hydroxide precursor during the heat treatment process, avoid the common phase separation problem, and ensure the stability of the cathode material during charge and discharge. Therefore, Co-doped YTiTaO 6 composite SrRuO 3 In the material, the Co-doped YTiTaO 6 and SrRuO 3 have a synergistic effect, which can significantly improve the overall performance of the sodium-ion battery and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 SEM image of the cathode material prepared in Example 1.

[0038] Figure 2 Electrochemical performance graphs of the batteries assembled with the cathode materials prepared in Examples 1 to 4 and Comparative Examples 1 to 3.

[0039] Figure 3 Electrochemical performance graphs of the batteries assembled with the cathode materials prepared in Examples 5 to 8.

[0040] Figure 4 Electrochemical performance graphs of the batteries assembled with the cathode materials prepared in Example 1, Example 9 and Example 10. DETAILED DESCRIPTION OF THE INVENTION

[0041] For the convenience of understanding the present invention, the present invention will be described more comprehensively and in detail below in conjunction with the accompanying drawings of the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0042] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the present invention can be obtained through the market or can be prepared by existing methods.

[0043] Preparation Example 1 Preparation of Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2

[0044] Add pure water to the reactor to 1 / 2 of its volume, then introduce a complexing agent of 6.5 g / L ammonia water and a precipitating agent of 4.5 mol / L sodium hydroxide to prepare a bottom solution with a pH of 12. Then introduce nitrogen to make the oxygen concentration in the reactor below 0.5%. Weigh nickel sulfate hexahydrate, ferrous sulfate heptahydrate, and manganese sulfate tetrahydrate according to the molar ratio of Ni:Fe:Mn of 1:1:1 and mix them with water for dissolution. The total metal ion concentration is 3.6 mol / L to obtain a metal salt solution. Continuously introduce the metal salt solution, 4.5 mol / L sodium hydroxide, and 6.5 g / L ammonia water into the reactor for coprecipitation reaction until the synthesized particle size reaches 5 μm, then stop the reaction; control the temperature at 60 °C, the pH at 11 - 12, and the stirring rate at 500 rpm throughout the reaction process. Filter, wash the reaction product precursor slurry, and dry it at 130 °C for 10 h to obtain Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 。

[0045] Preparation Example 2 for preparing Cu 0.2 Fe 0.3 Mn 0.5 (OH) 2

[0046] Add pure water to the reactor to 1 / 2 of its volume, then introduce a complexing agent of 6.5 g / L ammonia water and a precipitating agent of 4.5 mol / L sodium hydroxide to prepare a bottom solution with a pH of 11. Then introduce nitrogen to make the oxygen concentration in the reactor below 0.5%. Weigh copper sulfate, ferric sulfate, and manganese sulfate according to the molar ratio of Cu:Fe:Mn of 0.2:0.3:0.5 and mix them with water for dissolution. The total metal ion concentration is 3.0 mol / L to obtain a metal salt solution. Continuously introduce the metal salt solution, 4.5 mol / L sodium hydroxide, and 6.5 g / L ammonia water into the reactor for coprecipitation reaction until the synthesized particle size reaches 5 μm, then stop the reaction; control the temperature at 60 °C, the pH at 11 - 12, and the stirring rate at 350 rpm throughout the reaction process. Filter, wash the reaction product precursor slurry, and dry it at 130 °C for 12 h to obtain the prepared Cu 0.2 Fe 0.3 Mn 0.5 (OH) 2 。

[0047] Example 1

[0048] In this example, the layered hydroxide precursor in the cathode material precursor of the sodium-ion battery is Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 prepared in Preparation Example 1; the coating layer is Co-doped YTiTaO 6 composite SrRuO3 Material

[0049] In this embodiment, a method for preparing a precursor of a sodium-ion battery cathode material includes the following steps:

[0050] S1: Mix yttrium nitrate, tetrabutyl titanate, cobalt nitrate, tantalum ethoxide, and citric acid in water and stir evenly to obtain a mixed solution, where: yttrium nitrate, tetrabutyl titanate, cobalt nitrate, and tantalum ethoxide are added according to the molar ratio of Y, Ti, Co, Ta of 1:0.97:0.04:1; the molar ratio of citric acid to the total molar number of Y, Ti, Co, Ta in yttrium nitrate, tetrabutyl titanate, cobalt nitrate, and tantalum ethoxide is 1.4:1. Stir and evaporate the mixed solution to dryness at 120 °C, and dry it at 130 °C for 10 h to obtain a powder. Then, place the powder in a muffle furnace and pre-calcine it at 500 °C for 6 h, and then raise the temperature to 1200 °C and calcine it for 12 h; obtain Co-doped YTiTaO 6 powder

[0051] S2: Add the Co-doped YTiTaO 6 powder and SrRuO 3 powder into absolute ethanol, stir and ultrasonicate for 2 h to obtain a dispersion; add the Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 prepared in Preparation Example 1 to the dispersion, continue to stir and ultrasonicate for 3 h, then stir and evaporate to dryness at 120 °C, and dry it in an oven at 150 °C for 10 h to obtain a solid. Heat the solid to 300 °C under a protective atmosphere and keep it warm for 4 h to obtain a Co-doped YTiTaO 6 composite SrRuO 3 coated sodium battery cathode material precursor. Wherein: the addition amounts of the Co-doped YTiTaO 6 powder and the SrRuO 3 powder are both 5 wt% of the addition amount of Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 added

[0052] Preparation of sodium-ion battery cathode material: Mix the Co-doped YTiTaO 6 composite SrRuO 3 coated sodium battery cathode material precursor and anhydrous sodium carbonate according to a sodium mixing ratio of 1.05, mix evenly, and then sinter in a muffle furnace at 900 °C for 20 h to obtain the cathode material Co-doped YTiTaO 6 composite SrRuO 3 coated NaNi 1 / 3 Fe 1 / 3 Mn1 / 3 O 2 。

[0053] The SEM image of the positive electrode material prepared in this example is as shown in Figure 1 Figure [0000394]. The primary particles of the positive electrode material are flaky, and the overall shape is spherical-like. The coating layer is tightly coated on the surface of the material, and there is no agglomeration phenomenon.

[0054] Example 2

[0055] It is basically the same as Example 1, except that the coating layer is Co-doped YTiTaO 6 , without SrRuO 3 ; that is, SrRuO 3 powder is not added in step (2), and the addition amount of Co-doped YTiTaO 6 powder is 10 wt% of the addition amount of Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 ; The prepared precursor is: Co-doped YTiTaO 6 -coated Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 , and the positive electrode material is Co-doped YTiTaO 6 -coated NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 。

[0056] Comparative Example 1

[0057] Directly use Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 prepared in Preparation Example 1 as the precursor without coating; according to the preparation method of the positive electrode material of the sodium-ion battery in Example 1, the precursor and sodium carbonate are mixed evenly and then sintered to prepare the positive electrode material NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 。

[0058] Comparative Example 2

[0059] The difference from Example 2 is that the coating layer is YTiTaO 6 ; The preparation method of the corresponding YTiTaO 6 is as follows:

[0060] Yttrium nitrate, tetrabutyl titanate, tantalum ethoxide, and citric acid were stirred and mixed evenly in water to obtain a mixed solution, where: yttrium nitrate, tetrabutyl titanate, and tantalum ethoxide were added according to a molar ratio of Y, Ti, Ta of 1:1:1; the molar ratio of citric acid to the total molar amount of Y, Ti, Ta in yttrium nitrate, tetrabutyl titanate, and tantalum ethoxide was 1.4:1. The mixed solution was stirred and evaporated to dryness at 120 °C and dried at 130 °C for 10 h to obtain a powder. Then the powder was placed in a muffle furnace and pre-calcined at 500 °C for 6 h, and then heated to 1200 °C and calcined for 12 h; to obtain YTiTaO 6 powder. The dried powder was placed in a muffle furnace at 800 °C and calcined for 15 h to obtain YTiTaO 6 powder.

[0061] The rest of the preparation method was the same as that of Example 2, and the corresponding precursor prepared was YTiTaO 6 coated Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 , and the cathode material was YTiTaO 6 coated NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 .

[0062] Comparative Example 3

[0063] was basically the same as Example 1, except that SrRuO 3 was directly used as the coating layer; that is, Co-doped YTiTaO 6 powder was not added in step (2), and the addition amount of SrRuO 3 powder was 10 wt% of the addition amount of Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 ; the corresponding precursor prepared was SrRuO 3 coated Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 , and the cathode material was SrRuO 3 coated NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 .

[0064] Example 3

[0065] was basically the same as Example 1, except that Co-doped YTiTaO 6During the preparation of the powder, yttrium nitrate, tetrabutyl titanate, cobalt nitrate, and tantalum ethoxide were added according to the molar ratio of Y, Ti, Co, and Ta of 1:0.9925:0.01:1.

[0066] Example 4

[0067] Basically the same as Example 1, except that in the preparation of the Co-doped YTiTaO 6 powder, yttrium nitrate, tetrabutyl titanate, cobalt nitrate, and tantalum ethoxide were added according to the molar ratio of Y, Ti, Co, and Ta of 1:0.925:0.1:1.

[0068] Example 5

[0069] Basically the same as Example 1, except that the layered hydroxide precursor was Cu 0.2 Fe 0.3 Mn 0.5 (OH) 2 prepared in Preparation Example 2, and the obtained precursor was: Co-doped YTiTaO 6 composite SrRuO 3 coated Cu 0.2 Fe 0.3 Mn 0.5 (OH) 2 , and the cathode material was Co-doped YTiTaO 6 composite SrRuO 3 coated NaCu 0.2 Fe 0.3 Mn 0.5 O 2 .

[0070] Example 6

[0071] Basically the same as Example 5, except that the coating layer was Co-doped YTiTaO 6 , without SrRuO 3 ; that is, SrRuO 3 powder was not added in step (2), and the addition amount of Co-doped YTiTaO 6 powder was 10 wt% of the addition amount of Cu 0.2 Fe 0.3 Mn 0.5 (OH) 2 ; the prepared precursor was: Co-doped YTiTaO 6 coated Cu 0.2 Fe 0.3 Mn 0.5 (OH) 2 , and the cathode material was Co-doped YTiTaO 6 coated NaCu0.2 Fe 0.3 Mn 0.5 O 2 。

[0072] Example 7

[0073] It is basically the same as Example 5, except that the addition amount of Co-doped YTiTaO 6 powder is 7.5 wt% of the addition amount of Cu 0.2 Fe 0.3 Mn 0.5 (OH) 2 ; the addition amount of SrRuO 3 powder is 2.5 wt% of the addition amount of Cu 0.2 Fe 0.3 Mn 0.5 (OH) 2 .

[0074] Example 8

[0075] It is basically the same as Example 5, except that the addition amount of Co-doped YTiTaO 6 powder is 2.5 wt% of the addition amount of Cu 0.2 Fe 0.3 Mn 0.5 (OH) 2 ; the addition amount of SrRuO 3 powder is 7.5 wt% of the addition amount of Cu 0.2 Fe 0.3 Mn 0.5 (OH) 2 .

[0076] Example 9

[0077] In this example, the layered hydroxide precursor in the precursor of the sodium-ion battery cathode material is Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 prepared in Preparation Example 1; the coating layer is a Co-doped YTiTaO 6 composite SrRuO 3 material.

[0078] The preparation method of the precursor of the sodium-ion battery cathode material in this example includes the following steps:

[0079] S1: Mix yttrium chloride, titanium sulfate, cobalt chloride, ammonium tantalate and urea evenly in water to obtain a mixed solution, where: yttrium chloride, titanium sulfate, cobalt chloride, ammonium tantalate are added according to the molar ratio of Y, Ti, Co, Ta being 1:0.955:0.06:1; the molar ratio of urea to the total molar amount of Y, Ti, Co, Ta in yttrium chloride, titanium sulfate, cobalt chloride, ammonium tantalate is 1.1:1. Stir and evaporate the mixed solution to dryness at 120 °C, and dry it at 130 °C for 10 h to obtain a powder. Then place the powder in a muffle furnace and pre-calcine it at 400 °C for 8 h, and then raise the temperature to 900 °C and calcine it for 16 h; obtain Co-doped YTiTaO 6 powder.

[0080] S2: Add the Co-doped YTiTaO 6 powder and SrRuO 3 powder into absolute ethanol, stir and ultrasonicate for 1.5 h to obtain a dispersion; add the Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 prepared in Preparation Example 1 to the dispersion, continue to stir and ultrasonicate for 2 h, then stir and evaporate to dryness at 120 °C, and dry it in an oven at 150 °C for 10 h to obtain a solid. Heat the solid to 400 °C under a protective atmosphere and keep it warm for 4 h to obtain a Co-doped YTiTaO 6 composite SrRuO 3 coated sodium-ion battery cathode material precursor. Wherein: the addition amounts of the Co-doped YTiTaO 6 powder and the SrRuO 3 powder are both 2 wt% of the addition amount of Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 .

[0081] Preparation of the sodium-ion battery cathode material: Mix the Co-doped YTiTaO 6 composite SrRuO 3 coated sodium-ion battery cathode material precursor and anhydrous sodium carbonate according to a sodium mixing ratio of 1.1, mix evenly, and then sinter in a muffle furnace at 800 °C for 22 h to obtain the cathode material Co-doped YTiTaO 6 composite SrRuO 3 coated NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 .

[0082] Example 10

[0083] In this embodiment, the layered hydroxide precursor in the cathode material precursor of the sodium-ion battery is the Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 prepared in Preparation Example 1; the coating layer is Co-doped YTiTaO 6 composite SrRuO 3 material.

[0084] The preparation method of the cathode material precursor of the sodium-ion battery in this embodiment includes the following steps:

[0085] S1: Mix yttrium acetate, titanium oxysulfate, cobalt acetate, sodium tantalate, and citric acid evenly in water to obtain a mixed solution, where: yttrium acetate, titanium oxysulfate, cobalt acetate, and sodium tantalate are added according to the molar ratio of Y, Ti, Co, Ta of 1:0.94:0.08:1; the molar ratio of citric acid to the total molar number of Y, Ti, Co, Ta in yttrium acetate, titanium oxysulfate, cobalt acetate, and sodium tantalate is 1.7:1. Stir and evaporate the mixed solution to dryness at 120 °C, and dry it at 150 °C for 8 h to obtain a powder. Then, place the powder in a muffle furnace and pre-burn it at 600 °C for 5 h, and then heat it up to 1300 °C and calcine it for 8 h; obtain Co-doped YTiTaO 6 powder.

[0086] S2: Add the Co-doped YTiTaO 6 powder and SrRuO 3 powder prepared in step S1 into absolute ethanol, stir and ultrasonicate for 1.0 h to obtain a dispersion; add the Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 prepared in Preparation Example 1 to the dispersion, continue to stir and ultrasonicate for 4 h, then stir and evaporate to dryness at 120 °C, and dry it in an oven at 150 °C for 10 h to obtain a solid. Heat the solid to 200 °C under a protective atmosphere and keep it warm for 5 h to obtain the Co-doped YTiTaO 6 composite SrRuO 3 coated cathode material precursor of the sodium battery. Wherein: the addition amounts of the Co-doped YTiTaO 6 powder and the SrRuO 3 powder are both 8 wt% of the addition amount of Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH) 2 .

[0087] Preparation of the cathode material of the sodium-ion battery: Co-doped YTiTaO 6 composite SrRuO 3The coated sodium-ion battery cathode material precursor and anhydrous sodium carbonate are mixed evenly at a sodium mixing ratio of 1.05, and then sintered in a muffle furnace at 950 °C for 18 h to obtain the cathode material Co-doped YTiTaO 6 Composite SrRuO 3 Coated NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 。

[0088] The cathode materials prepared in Examples 1-10 and Comparative Examples 1-3 are assembled into batteries. According to the mass ratio of cathode material: conductive graphite: PVDF of 8:1:1, they are weighed and ground, and then an appropriate amount of N-methylpyrrolidone (NMP) is added dropwise and ground and stirred continuously to form a uniform slurry. The slurry is evenly coated on the aluminum foil with a mold, the coating thickness is 200 μm, and it is placed in a drying oven at 90 °C for 10 h, and then cut into circular pieces with a diameter of 12 mm. Using the circular piece as the positive electrode and the sodium piece as the negative electrode, the electrolyte includes a solvent and NaPF 6 ,where the concentration of NaPF 6 is 1 mol / L, and the solvent of the electrolyte is a mixed solvent of EC, DEC, and DMC with a volume ratio equal to 1:1:1. The batteries are assembled in a glove box according to the button cell assembly sequence.

[0089] The performance of the above-assembled batteries is tested. The assembled batteries that have been left standing overnight are placed in a LAND2001CT battery test chamber for charge-discharge testing, and the testing is carried out under the conditions of 25 °C, 1C, and a cycling voltage of 2-4V for 50 cycles.

[0090] Figure 2 It is a data graph of the cycle stability and discharge specific capacity of the batteries assembled with the cathode materials prepared in Examples 1-4 and Comparative Examples 1-3. As can be seen from the figure, compared with the batteries assembled with the cathode material in Comparative Example 1, the cycle stability and discharge specific capacity of the batteries assembled with the coated and modified cathode materials have both increased to a certain extent; the cathode material prepared in Example 2 has further improved cycle stability and discharge specific capacity compared with the uncoated cathode material of Co-doped YTiTaO 6 in Comparative Example 2. The cathode material with Co-doped YTiTaO 6 composite SrRuO 3 as the coating layer in Example 1 has much better cycle stability and discharge specific capacity compared with the cathode material with Co-doped YTiTaO 6 as the coating layer (Example 2) and the cathode material with SrRuO 3 as the coating layer (Comparative Example 3). In Examples 3 and 4, the doping amount of Co is mainly changed, and its performance has a certain fluctuation compared with Example 1, but still has good cycle stability and discharge specific capacity.

[0091] Figure 3 Data graph of the cycle stability and discharge specific capacity after assembling the cathode materials prepared in Examples 5 to 8 into batteries. It can be seen from the figure that when the cathode active material is NaCu 0.2 Fe 0.3 Mn 0.5 O 2 , and Co-doped YTiTaO 6 is used as the composite SrRuO 3 as the coating layer, its cycle stability and discharge specific capacity are still improved to a certain extent compared with the cathode material coated with Co-doped YTiTaO 6 (Example 6). In Examples 7 and 8, the proportions of Co-doped YTiTaO 6 powder and SrRuO 3 powder in the coating layer are adjusted. It can be seen that when the content ratio of Co-doped YTiTaO 6 powder increases in Example 7, its performance will slightly decrease compared with Example 5. When the content ratio of SrRuO 3 powder increases in Example 8, its performance will also decrease to a certain extent; but overall, Examples 7 and 8 still have good cycle stability and discharge specific capacity.

[0092] Figure 4 Data graph of the cycle stability and discharge specific capacity after assembling the cathode materials prepared in Examples 9 and 10 into batteries. It can be seen from the figure that when certain changes occur in the coating amount and preparation process parameters, etc., its performance will have a certain fluctuation, but still has good cycle stability and discharge specific capacity.

[0093] The above examples are only to illustrate the technical concept and characteristics of the present invention, and their purpose is to enable those familiar with this technology to understand the content of the present invention and implement it accordingly, and cannot be used to limit the protection scope of the present invention. All equivalent changes or doping made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A sodium ion battery cathode material precursor, characterized in that: It comprises a layered hydroxide precursor and a coating layer coated on at least a part of the surface of the layered hydroxide precursor; wherein the coating layer is a Co-doped YTiTaO6 material or a Co-doped YTiTaO6 composite SrRuO3 material; In the Co-doped YTiTaO6, the molar ratio of Y, Ti, Co and Ta is 1:1-0.75x:x:1, 0.01≤x≤0.1; in the Co-doped YTiTaO6 composite SrRuO3 material, the mass ratio of Co-doped YTiTaO6 to SrRuO3 is (1~3):(1~3).

2. The sodium ion battery cathode material precursor according to claim 1, characterized in that: The mass of the coating layer is 1-20% of the mass of the layered hydroxide precursor.

3. The sodium ion battery positive electrode material precursor according to claim 1, characterized in that: The layered hydroxide precursor is one of nickel-iron-manganese layered hydroxide, nickel-iron-copper-manganese layered hydroxide, copper-iron-manganese layered hydroxide, nickel-manganese-copper layered hydroxide, and nickel-zinc-iron-manganese layered hydroxide.

4. A method for preparing a sodium ion battery cathode material precursor according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: adding yttrium source, titanium source, cobalt source, tantalum source and complexing agent into water, stirring evenly, heating and evaporating to dryness, and further drying to obtain powder; pre-burning the powder, and then heating and calcining to obtain Co-doped YTiTaO6 powder; S2: Dispersing Co-doped YTiTaO6 powder or a mixed powder consisting of Co-doped YTiTaO6 powder and SrRuO3 powder in an alcohol solvent to obtain a dispersion; dispersing a layered hydroxide precursor in the dispersion, stirring and evaporating to obtain a solid; after the solid is dried, heating and then keeping warm under a protective atmosphere to obtain a precursor of a positive electrode material for a sodium ion battery.

5. The method for preparing a precursor of a positive electrode material for a sodium ion battery according to claim 4, characterized in that: In step S1, the yttrium source is one or more of yttrium nitrate, yttrium chloride, and yttrium acetate; The titanium source is one or more of butyl titanate, titanium nitrate, titanium sulfate, and titanyl sulfate; The cobalt source is one or more of cobalt nitrate, cobalt sulfate, cobalt chloride and cobalt acetate; The tantalum source is one or more of ethoxy tantalum, ammonium tantalate, and sodium tantalate; The yttrium source, titanium source, cobalt source and tantalum source are added according to the molar ratio of Y, Ti, Co and Ta being 1:1-0.75x:x:1, 0.01≤x≤0.1; The complexing agent is one or more of citric acid, urea, and polyethylene glycol, and the ratio of the molar number of the complexing agent to the total molar number of Y, Ti, Co, and Ta ions in the yttrium source, titanium source, cobalt source, and tantalum source is 1-2:

1.

6. The method for preparing a precursor of a positive electrode material for a sodium ion battery according to claim 4, characterized in that: In step S1, the pre-sintering temperature is 400-600°C, and the pre-sintering time is 5-8 hours; the calcining temperature is 900-1300°C, and the calcining time is 8-12 hours; In step S2, the insulation temperature is 200-400° C., and the insulation time is 0.5-5 h.

7. A sodium ion battery positive electrode material, characterized in that: The positive electrode material for a sodium ion battery is prepared by mixing the positive electrode material precursor of any one of claims 1 to 3 with a sodium source and then sintering the mixture.

8. A sodium ion battery, characterized in that: It includes the sodium ion battery positive electrode material according to claim 7.

Images