Sodium battery positive electrode material and preparation method thereof, pole piece and battery

Abstract

The invention discloses a sodium battery positive electrode material and a preparation method thereof, a pole piece and a battery, and the preparation method comprises the following steps: S1, introducing a rare metal Y element into the sodium battery positive electrode material NNMO to form Y doping; and S2, introducing an antioxidant into the Y-doped sodium battery positive electrode material NNMO to obtain the modified sodium battery positive electrode material. Through dual modification of bulk phase doping and interface modification, the high-temperature cycling stability and air stability of the sodium-ion battery positive electrode material NNMO are remarkably improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of batteries, in particular to a sodium battery positive electrode material, a preparation method thereof, a pole piece and a battery. BACKGROUND

[0002] With the increasing demand of human society for various energy materials, developing energy storage devices with high stability, high cycle and high safety has become one of the national strategic development directions.

[0003] The working principle of a sodium battery is similar to that of a lithium battery, but the sodium battery has the advantage of more abundant active material sources. Layered oxides as a common sodium ion battery positive electrode material are prone to complex phase changes during high-voltage charging and discharging. This leads to a significant capacity decay of the material under high-temperature cycling conditions. Therefore, how to improve the high-temperature performance through surface modification has become a widely explored direction for researchers.

[0004] The traditional sodium battery layered oxide positive electrode material NNMO currently faces the following key technical bottlenecks: air sensitivity: the material surface is prone to react with moisture or oxygen in the air, leading to structural degradation, and strict humidity and oxygen control is required in industrial production; high-temperature cycle decay: at high temperature, transition metal ion dissolution is accelerated, and the interface side reaction between the electrode and the electrolyte is intensified, ultimately resulting in a generally low cycle capacity retention rate. SUMMARY The purpose of the present application is to provide a sodium battery positive electrode material, a preparation method thereof, a pole piece and a battery, which improve the high-temperature cycle stability and air stability of the sodium ion battery positive electrode material NNMO through a dual modification strategy of bulk doping and interface modification.

[0005] To achieve the above-mentioned purpose, the technical solution provided by the present application is: The first aspect of the present application provides a preparation method of a sodium battery positive electrode material, comprising the following steps: S1: introducing a rare metal Y element into a sodium battery positive electrode material NNMO to form Y doping; S2: introducing an antioxidant into the Y-doped sodium battery positive electrode material NNMO to obtain a modified sodium battery positive electrode material.

[0006] To optimize the above-mentioned technical solution, the specific measures taken also include: Step S1 introduces a rare metal Y element by high-temperature calcination, and the reaction conditions are high-temperature calcination at 580-620 DEG C for 10-15 h, the heating rate is 35-45 DEG C / min, and natural annealing.

[0007] Step S2 introduces an antioxidant by hydrothermal reaction, and the reaction conditions are stirring uniformly in anhydrous ethanol, and then baking at 170-190 DEG C for 14-20 h.

[0008] Further, the antioxidant is di-tert-butyl-p-cresol.

[0009] Preferably, the mass ratio of the sodium battery cathode material NNMO to the Y element is 120-140:1.

[0010] Preferably, the mass ratio of the sodium battery cathode material NNMO to the antioxidant is 490-520:1.

[0011] Step S2 introduces the rare metal Y element by using a Y-containing compound, and the Y-containing compound used is yttrium oxide or yttrium nitrate.

[0012] The second aspect of the present application provides a sodium battery cathode material prepared by the above method.

[0013] The third aspect of the present application provides a pole piece comprising the above sodium battery cathode material.

[0014] The fourth aspect of the present application provides a battery comprising the above pole piece.

[0015] Compared with the prior art, the present application has the following beneficial effects: The present application modifies the sodium battery cathode material layered oxide NNM to improve its air sensitivity and high-temperature cycle life: first, introduce the rare metal Y element coating, not only use its Y-O bond to stabilize the structure, and Y doping makes the Na layer thickness increase, more conducive to Na + transport, while appropriate Y doping also reduces the side reaction between the active material and the electrolyte; then, introduce the antioxidant di-tert-butyl-p-cresol, trace amounts of antioxidant can eliminate free radicals and singlet oxygen on the surface of the active material, prevent the material from absorbing water and getting wet, greatly reduce the interface side reaction, and inhibit the irreversible phase change, so as to realize the stability of the material structure at high temperature. DETAILED DESCRIPTION

[0016] The above content of the present application will be further described in detail in the form of specific embodiments, but it should not be understood that the scope of the above subject matter of the present application is limited to the following examples. Any technology realized based on the above content of the present application belongs to the scope of the present application.

[0017] The experimental methods used in the following examples are conventional methods, and the reagents, methods and equipment used are conventional reagents, methods and equipment in the technical field, unless otherwise specified.

[0018] The present application provides a preparation method of a sodium battery cathode material, comprising the following steps: S1: Introducing rare metal Y element into sodium battery positive electrode material NNMO to form Y-doped; S2: Introducing antioxidant into Y-doped sodium battery positive electrode material NNMO to obtain modified sodium battery positive electrode material.

[0019] Step S1 introduces rare metal Y element by high-temperature calcination. High-temperature calcination is carried out in an inert atmosphere.

[0020] Step S2 introduces antioxidant by hydrothermal reaction.

[0021] In some embodiments, the antioxidant is di-tert-butyl-p-cresol.

[0022] Preferably, the mass ratio of sodium battery positive electrode material NNMO to Y element ranges from 120 to 140:1.

[0023] Preferably, the mass ratio of sodium battery positive electrode material NNMO to antioxidant ranges from 490 to 520:1.

[0024] Step S2 introduces rare metal Y element by Y-containing compound. The Y-containing compound used is yttrium oxide or yttrium nitrate; Y sources containing S / Cl such as yttrium chloride and yttrium sulfate are avoided to prevent residual anions from damaging the interface stability.

[0025] The application also provides a sodium battery positive electrode material prepared by the above method.

[0026] The application also provides a pole piece comprising the above sodium battery positive electrode material.

[0027] The application also provides a battery comprising the above pole piece.

[0028] The technical solutions of the application are further described in detail below in combination with specific embodiments: Embodiment 1: 1. Preparation of modified NNMO material The conventional NNMO (Na 2 / 3 Ni 1 / 3 Mn 2 / 3 O2) powder is uniformly mixed with Y2O3 powder, then treated by ball milling, and placed in a tube furnace filled with nitrogen, and calcined at 600℃ for 12h to obtain intermediate NNMO@Y2O3. Then the intermediate NNMO@Y2O3 is dissolved in anhydrous ethanol with di-tert-butyl-p-cresol, stirred uniformly, and then placed in a blast drying oven and baked at 180℃ for 16h. The modified NNMO material is obtained by filtration, washing, and freeze-drying.

[0029] The high-temperature calcination has a heating rate of 40℃ / min, and is naturally annealed; the mass ratio of the conventional NNMO to Y2O3 powder is 100-105:1 (i.e., the mass ratio of NNMO to Y element is 127-133.3:1), and the mass ratio of the conventional NNMO to di-tert-butyl-p-cresol is 500-510:1.

[0030] 2. Preparation of positive electrode slurry: The positive active material is the modified NNMO material obtained in step 1, the binder is PVDF (KF1100), and the conductive agent is Super P (Swiss Timi Gao); the active material, the binder, and the conductive agent are mixed at a ratio of 80:10:10, and then coated on a 12-um aluminum foil and dried in a vacuum drying oven at 120℃ for 12 h.

[0031] 3. Preparation of negative electrode sheet: The negative active material is a hard carbon material, the binder is LA133 (Yindi Le), and the conductive agent is Super P (Swiss Timi Gao); the active material, the binder, and the conductive agent are mixed at a ratio of 8:1:1, and then coated on a 12-um aluminum foil and dried in a vacuum drying oven at 120℃ for 12 h.

[0032] 4. Assembly of soft-pack battery: The baked electrode sheet is rolled, cut, die-cut, assembled, liquid-injected, formed, and measured to obtain a soft-pack battery.

[0033] 5. Test of high-temperature cycle charge-discharge performance: The soft-pack battery is tested for 200 cycles by a battery test cabinet, with a charge-discharge current of 1C, a charge-discharge voltage of 2.0-4.1V, and a test temperature of 60℃.

[0034] 6. Test of active material moisture: The active material placed for 7 days is tested for moisture by the Karl Fischer method.

[0035] Example 2: This example is basically the same as example 1, except that the mass ratio of the conventional NNMO to Y2O3 powder is 90-95:1 (i.e., the mass ratio of NNMO to Y element is 114.3-120.6:1).

[0036] Example 3: This example is basically the same as example 1, except that the mass ratio of the conventional NNMO to Y2O3 powder is 95-100:1 (i.e., the mass ratio of NNMO to Y element is 120.6-127.0:1).

[0037] Example 4: The embodiment is basically the same as embodiment 1, the difference is that the mass ratio of conventional NNMO and Y2O3 powder is 105~110:1 (i.e. the mass ratio of NNMO and Y element is 133.3~139.7:1).

[0038] Example 5: The embodiment is basically the same as embodiment 1, the difference is that the mass ratio of conventional NNMO and Y2O3 powder is 110~115:1 (i.e. the mass ratio of NNMO and Y element is 139.7~146.0:1).

[0039] Example 6: The embodiment is basically the same as embodiment 1, the difference is that the mass ratio of conventional NNMO and di-tert-butyl-p-cresol is 480~490:1.

[0040] Example 7: The embodiment is basically the same as embodiment 1, the difference is that the mass ratio of conventional NNMO and di-tert-butyl-p-cresol is 490~500:1.

[0041] Example 8: The embodiment is basically the same as embodiment 1, the difference is that the mass ratio of conventional NNMO and di-tert-butyl-p-cresol is 510~520:1.

[0042] Example 9: The embodiment is basically the same as embodiment 1, the difference is that the mass ratio of conventional NNMO and di-tert-butyl-p-cresol is 520~530:1.

[0043] Comparative Example 1: The comparative example is basically the same as embodiment 1, the difference is that there is no Y2O3 introduced in step 1.

[0044] Comparative Example 2: The comparative example is basically the same as embodiment 1, the difference is that there is no di-tert-butyl-p-cresol introduced in step 1.

[0045] Comparative Example 3: The comparative example is basically the same as embodiment 1, the difference is that the conventional NNMO is used as the positive electrode material; the test evaluation results of each embodiment are shown in Table 1. Each of the above embodiments, comparative examples is repeated several times according to the described conditions, and the data in Table 1 is the average value of multiple tests of each example.

[0046] Table 1

[0047] Analysis of test results: The Y doping effect has an important influence on the test results of the application. The NNMO:Y element of example 1 is 127-133:1, which exhibits the best performance. The Na layer expansion effect of the Na + The diffusion coefficient is greatly improved; the Y-O bond stabilizes the phase transition enthalpy, thereby making the corresponding cycle retention rate 90.9% significantly higher than 85.1% of comparative example 1.

[0048] In the antioxidant mechanism of di-tert-butyl-p-cresol, the phenolic hydroxyl group is combined with the oxygen vacancy on the surface of the material to prevent the material from absorbing water and getting wet; the free radical scavenging efficiency has a nonlinear relationship with the addition amount, and reaches saturation adsorption at 500-510:1.

[0049] The Y doping effect and the antioxidant effect of di-tert-butyl-p-cresol form a synergistic effect, and the test effect of example 1 is significantly better than that of comparative example 3; the test shows that Y doping mainly improves the bulk stability, and the antioxidant optimizes the interface chemistry, and the synergistic effect of the two can significantly reduce the high-temperature capacity decay rate.

[0050] The above is only a preferred embodiment of the application, and does not limit the application in any form. Any person skilled in the art can make any simple modification, equivalent replacement and improvement to the above embodiment according to the technical essence of the application without departing from the scope of the technical solution of the application, and all of the above still belong to the protection scope of the technical solution of the application.

Claims

1. A method for preparing a sodium battery cathode material, characterized in that, Includes the following steps: S1: Introduce rare metal Y element into NNMO, the cathode material of sodium battery, to form Y doping; S2: An antioxidant is introduced into the Y-doped sodium battery cathode material NNMO to obtain a modified sodium battery cathode material.

2. The method for preparing the sodium battery cathode material according to claim 1, characterized in that: Step S1 introduces rare metal Y element through high-temperature calcination. The reaction conditions are high-temperature calcination at 580~620℃ for 10~15h, heating rate of 35~45℃ / min, and natural annealing.

3. The method for preparing the sodium battery cathode material according to claim 1, characterized in that: Step S2 introduces the antioxidant through a hydrothermal reaction. The reaction conditions are: after stirring evenly in anhydrous ethanol, baking at 170~190℃ for 14~20h.

4. The method for preparing the sodium battery cathode material according to claim 1, characterized in that: The antioxidant mentioned is di-tert-butyl-p-cresol.

5. The method for preparing the sodium battery cathode material according to claim 1, characterized in that: The mass ratio of NNMO to Y in sodium battery cathode material ranges from 120 to 140:

1.

6. The method for preparing the sodium battery cathode material according to claim 1, characterized in that: The mass ratio of NNMO, the cathode material for sodium batteries, to antioxidants ranges from 490 to 520:

1.

7. The method for preparing the sodium battery cathode material according to claim 1, characterized in that: Step S2 introduces the rare metal element Y through a Y-containing compound, which is either yttrium oxide or yttrium nitrate.

8. A sodium battery cathode material, characterized in that: Prepared using the method described in any one of claims 1 to 7.

9. An electrode sheet, characterized in that: It includes the sodium battery cathode material as described in claim 8.

10. A battery, characterized in that: It includes the electrode sheet as described in claim 9.

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