Preparation method and application of oxygen positive electrode material of high-voltage long-circulation sodium-ion battery layer

Abstract

The invention belongs to the technical field of sodium-ion batteries, and particularly relates to a preparation method and application of a high-voltage long-circulation sodium-ion battery layer oxygen positive electrode material. Transition metal elements in a specific proportion are doped, then a nano material in a certain proportion is coated through special ball milling treatment, and the layered oxide positive electrode material with good crystallinity is finally obtained through sintering treatment. The layered oxygen positive electrode material synthesized by the preparation method provided by the invention has excellent electrochemical performance in a high-voltage range, can effectively inhibit the structural collapse of the material in the charging and discharging process, and successfully solves the problem that the capacity of the battery in the high-voltage range is declined in a cliff manner.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion batteries, and in particular relates to a method for preparing a layered oxygen positive electrode material for a high-voltage long-cycle sodium ion battery and an application thereof. Background Art

[0002] Sodium-ion batteries have gradually become the first choice for large-scale energy storage technology due to their abundant sodium resource reserves. Sodium-ion batteries have a similar working mechanism to lithium-ion batteries, but the larger ionic radius of sodium ions causes significant changes in electrode materials before and after cycling, resulting in a cliff-like drop in battery capacity during long cycles. Therefore, many scientific researchers are committed to improving the cycle performance of sodium-ion batteries so that sodium-ion batteries can be industrialized on a large scale as soon as possible.

[0003] Layered transition metal oxide materials for sodium ion batteries are divided into two structures, P and O, according to the coordination type of sodium ions and oxygen and the stacking mode of oxygen. "P" refers to the triangular prism coordination environment and "O" refers to the octahedral coordination environment. Among them, the O phase material has a higher specific capacity in the high voltage range, but its complex phase change during the charge and discharge process seriously affects its cycle performance. Therefore, in order for the sodium ion battery layered oxide positive electrode material to exert high capacity in the high voltage range while having excellent cycle performance, it is necessary to provide a sodium ion battery layered oxide positive electrode material and a preparation method thereof. Summary of the invention

[0004] The object of the present invention is to provide a sodium ion battery layer oxygen positive electrode material which still has excellent electrochemical performance in a high voltage range.

[0005] The present invention provides a method for preparing a layered oxygen positive electrode material for a sodium ion battery, the method comprising the following steps: S1, mixing the sodium-containing compound, the nickel-iron-manganese precursor, and the M-containing compound to obtain a first mixed material; S2, sintering the first mixed material for the first time, and then crushing, pulverizing and screening the first time to obtain a primary sintered material; S3, ball-milling and mixing the coating material and the primary sintered material to obtain a second mixed material; S4, sintering the second mixed material for the second time, and then crushing, pulverizing and screening for the second time to obtain a chemical formula of Na a Ni b Fe c Mn d M eO2 layer oxygen positive electrode material, wherein M is one or more of Ca, Ti, Cu, Zr, Zn, Mg and Al, a, b, c, d, e are the molar ratios of the corresponding elements in the material, 0.85≤a≤1, 0.2≤b≤0.5, 0.2≤c≤0.5, 0.2≤d≤0.5, 0.01≤e≤0.2, wherein b+c+d=1; The sodium-containing compound is sodium carbonate or sodium bicarbonate; The M-containing compound includes oxides containing Ca, Ti, Cu, Zr, Zn, Mg, and Al and / or hydroxides containing Ca, Ti, Cu, Zr, Zn, Mg, and Al; The coating material is nano-titanic acid; the mass of the coating layer is 0.2wt% to 1wt% of the mass of the primary sintered material.

[0006] Preferably, the molar ratio of the sodium-containing compound, the nickel-iron-manganese precursor, and the M-containing compound is 0.85~1:1:0.01~0.2.

[0007] Preferably, in step S2, the first sintering is performed in a dry air atmosphere; the humidity of the dry air atmosphere is 0% to 30%, and the air intake flow rate is 10 L / min to 30 L / min.

[0008] Preferably, in step S2, the conditions for the first sintering are: heating to 600°C~800°C at a heating rate of 2°C / min~5°C / min and keeping warm for 4h~10h, then heating to 900°C~1000°C at a heating rate of 2°C / min~5°C / min and keeping warm for 8h~14h, and then cooling to room temperature at a cooling rate of 2°C / min.

[0009] Preferably, in step S2, the mesh size of the sieve for the first screening is 400 meshes.

[0010] Preferably, the ball-to-material ratio used in the ball milling mixing process is 2:1-3:1, the diameter of the large ball is 20mm-26mm, the diameter of the medium ball is 10mm-15mm, the diameter of the small ball is 5mm-9mm, the ball milling speed is 200r / min-800r / min, and the ball milling time is 3h-6h.

[0011] Preferably, in step S4, the second sintering is performed in a dry air atmosphere; the humidity of the dry air atmosphere is 0% to 30%, and the air intake flow rate is 10 L / min to 30 L / min.

[0012] Preferably, in step S4, the conditions for the second sintering are: heating to 900°C~1000°C at a heating rate of 2°C / min~5°C / min, keeping the temperature for 5h~8h, and then cooling to room temperature at a cooling rate of 2°C / min.

[0013] Preferably, in step S4, the mesh size of the second screening is 300 meshes.

[0014] The present invention also provides the application of the method described in the above technical solution in the preparation of sodium ion batteries.

[0015] Beneficial effects of the present invention: 1. The specific proportion of transition metal element doping in the present invention inhibits the complex phase change of the positive electrode material in the high voltage range, further improves the charge and discharge specific capacity of the positive electrode material, and successfully solves the problem of structural collapse of the material during the charge and discharge process, resulting in a cliff-like drop in the capacity of the battery in the high voltage range.

[0016] 2. Nano-titanic acid has a tiny structure and strong ion exchange capacity. The present invention uses nano-titanic acid as a coating material to neutralize residual alkali substances on the surface of the layered oxide material, and controls the thickness of the coating layer by adjusting the ball milling time and the coating ratio. While effectively reducing the impurity elements on the surface of the material, the ion transfer rate is improved, so that the synthesized sodium ion battery layered oxide material has higher capacity, rate performance and cycle performance.

[0017] 3. The present invention synthesizes the sodium ion battery layered oxide positive electrode material by a solid phase method, the synthesis process is simple, the cost is low, and it is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 This is a SEM image of the positive electrode material prepared in Example 1; Figure 2 It is a comparison diagram of the first week charge and discharge curves of the positive electrode materials prepared in each embodiment and each comparative example; Figure 3 It is a comparison chart of the rate performance of the positive electrode materials prepared in each embodiment and each comparative example; Figure 4 The figure is a comparison chart of the cycle performance of the positive electrode materials prepared in each embodiment and each comparative example. DETAILED DESCRIPTION

[0020] The present invention provides a method for preparing a layered oxygen positive electrode material for a sodium ion battery, the method comprising the following steps: S1, mixing the sodium-containing compound, the nickel-iron-manganese precursor, and the M-containing compound to obtain a first mixed material; S2, sintering the first mixed material for the first time, and then crushing, pulverizing and screening the first time to obtain a primary sintered material; S3, ball-milling and mixing the coating material and the primary sintered material to obtain a second mixed material; S4, sintering the second mixed material for the second time, and then crushing, pulverizing and screening for the second time to obtain a chemical formula of Na a Ni b Fe c Mn d M e O2 layer oxygen positive electrode material, wherein M is one or more of Ca, Ti, Cu, Zr, Zn, Mg and Al, a, b, c, d, e are the molar ratios of the corresponding elements in the material, 0.85≤a≤1, 0.2≤b≤0.5, 0.2≤c≤0.5, 0.2≤d≤0.5, 0.01≤e≤0.2, wherein b+c+d=1; The sodium-containing compound is sodium carbonate or sodium bicarbonate; the M-containing compound includes oxides containing Ca, Ti, Cu, Zr, Zn, Mg, and Al and / or hydroxides containing Ca, Ti, Cu, Zr, Zn, Mg, and Al; the coating material is nano-titanic acid; the mass of the coating layer is 0.2-1wt% of the mass of the primary sintered material.

[0021] The present invention firstly mixes a sodium-containing compound, a nickel-iron-manganese precursor and an M-containing compound uniformly to obtain a first mixed material.

[0022] In the present invention, the molar ratio of the sodium-containing compound, the nickel-iron-manganese precursor, and the M-containing compound is preferably 0.85-1:1:0.01-0.2, and more preferably 0.9:1:0.05 or 0.9:1:0.07.

[0023] After obtaining the first mixed material, the present invention performs a first sintering on the first mixed material, and then performs crushing, pulverizing and first screening to obtain a primary sintered material.

[0024] In the present invention, the first sintering is preferably carried out in a dry air atmosphere; the humidity of the dry air atmosphere is preferably 0%~30%; the air intake flow rate is preferably 10L / min~30L / min, more preferably 20L / min; the conditions for the first sintering of the present invention are preferably: heating to 600℃~800℃ at a heating rate of 2℃ / min~5℃ / min and keeping warm for 4h~10h, then heating to 900℃~1000℃ at a heating rate of 2℃ / min~5℃ / min and keeping warm for 8h~14h, and then cooling to room temperature at a cooling rate of 2℃ / min; in a preferred embodiment of the present invention, the conditions for the first sintering are preferably: heating to 600℃ at a heating rate of 3.5℃ / min and keeping warm for 8h, then heating to 900℃ at a heating rate of 2℃ / min and keeping warm for 10h, and finally cooling to room temperature at a cooling rate of 2℃ / min.

[0025] The mesh number of the first sieving of the present invention is preferably 400 meshes; the particle size of the primary sintered material obtained after the first sieving is preferably 4μm to 8μm. Before the pulverization, the present invention cools the material to room temperature, which is beneficial to maintain the stability of the material and prevent the material from oxidizing at high temperature. In addition, after cooling to room temperature, the hardness and brittleness of the material will change, which is beneficial to obtain finer and more uniform powder particles.

[0026] The present invention ball-mills the coating material and the primary sintering material to obtain a second mixed material.

[0027] In the present invention, the ball-to-material ratio used in the ball milling mixing process is preferably 2:1~3:1, the diameter of the large ball is preferably 20mm~26mm, the diameter of the medium ball is preferably 10mm~15mm, and the diameter of the small ball is preferably 5mm~9mm; the ball milling speed is preferably 200r / min~800r / min, and more preferably 250r / min~350r / min; the ball milling time is preferably 3h~6h, and more preferably 3h or 6h.

[0028] After obtaining the second mixed material, the present invention performs a second sintering on the second mixed material, and then performs crushing, pulverizing and a second screening process to obtain a chemical formula of Na a Ni b Fe c Mn d M e O2 layer oxygen cathode material.

[0029] In the present invention, the second sintering is preferably carried out in a dry air atmosphere; the humidity of the dry air atmosphere is preferably 0% to 30%; the air intake flow rate is preferably 10L / min to 30L / min, and more preferably 20L / min. The present invention performs sintering in dry air, which can effectively reduce side reactions and improve the air stability of the material; adjusting the cooling rate helps to obtain a better crystal structure and a higher degree of crystallinity, thereby improving the structural stability of the material.

[0030] The conditions for the second sintering of the present invention are preferably: heating to 900°C~1000°C at a heating rate of 2°C / min~5°C / min, keeping warm for 5h~8h, and then cooling to room temperature at a cooling rate of 2°C / min; in a preferred embodiment of the present invention, the conditions for the second sintering are preferably: heating to 925°C at a heating rate of 2.5°C / min, keeping warm for 6h, and then cooling to room temperature at a cooling rate of 2°C / min. The mesh number of the second screening of the present invention is preferably 300 meshes.

[0031] The layered oxygen positive electrode material prepared by the method provided by the present invention has a particle size D50 of 4 μm to 8 μm, a pH value of ≤12, a water content of ≤500 ppm, and a specific surface area of ​​0.5 m 2 / g~1.2m 2 / g. The examples show that it has excellent electrochemical properties in a high voltage range, can effectively inhibit the structural collapse of the material during the charge and discharge process, and successfully solves the problem of a cliff-like drop in battery capacity in a high voltage range.

[0032] The present invention also provides the application of the method described in the above technical solution in the preparation of sodium ion batteries.

[0033] In order to further illustrate the present invention, the preparation method and application of a high-voltage long-cycle sodium ion battery layer oxygen positive electrode material provided by the present invention are described in detail below in combination with the accompanying drawings and examples, but they should not be understood as limiting the scope of protection of the present invention.

[0034] Example 1 The chemical formula is Na 0.9 Ni 0.33 Fe 0.34 Mn 0.33 Zn 0.03 Cu 0.02 The layered oxide positive electrode material of sodium ion battery of O2, the coating material is nano-titanic acid, the mass ratio of the coating material to the primary sintering material is 0.5wt%, and the specific preparation method is as follows: (1) Raw material preparation: Place the raw materials in an agate mortar according to the mass ratio of nickel iron manganese precursor: sodium carbonate: zinc oxide: copper oxide = 1:0.54:0.03:0.02, and add 20 mL of anhydrous ethanol to the agate mortar for wet grinding. After grinding to a dry powder state, add 20 mL of anhydrous ethanol again for wet grinding and grind to a dry powder state.

[0035] (2) Primary sintering treatment: The mixed materials are placed in a box furnace for primary sintering, and the temperature is raised to 600°C at a heating rate of 3.5°C / min and kept at this temperature for 8 hours, and then raised to 900°C at a heating rate of 2°C / min and kept at this temperature for 10 hours, and finally cooled to room temperature at a cooling rate of 2°C / min to obtain a primary sintered material. During the sintering process, dry air is continuously introduced into the box furnace, the ventilation flow rate is set to 20L / min, and the humidity of the dry air is less than 30%.

[0036] (3) Crushing treatment: The primary sintered material is crushed and pulverized into a material with a particle size of D50 = 6 μm ± 0.5 μm.

[0037] (4) Ball milling: Place nano-titanic acid and primary sintered material into a ball mill in a certain proportion. The mass of nano-titanic acid is 0.5 wt% of the mass of primary sintered material. Ball milling is performed at 350 rpm for 3 h. The ball-to-material ratio used in the ball milling process is 2:1. The diameter of the large ball is 20.6 mm, the diameter of the medium ball is 15 mm, and the diameter of the small ball is 7.8 mm.

[0038] (5) Secondary sintering: The ball-milled and evenly mixed materials are placed in a box furnace for secondary sintering. The temperature is raised to 925°C at a heating rate of 2.5°C / min and kept at this temperature for 6 hours, and then cooled to room temperature at a cooling rate of 2°C / min. During the sintering process, dry air is continuously introduced into the box furnace, the ventilation flow rate is set to 20L / min, and the humidity of the dry air is less than 30%.

[0039] (6) Crushing treatment: The sintered material is crushed and crushed into a material with a particle size of D50 = 6 μm ± 0.5 μm, thereby obtaining a sodium ion battery layered oxide positive electrode material, the SEM image of which is shown in FIG. Figure 1 shown.

[0040] Example 2 The chemical formula is Na 0.9 Ni 0.33 Fe 0.34 Mn 0.33 Zn 0.03 Mg 0.04The sodium ion battery layered oxide positive electrode material of O2, the coating material is nano-titanic acid, the mass ratio of the coating material to the primary sintered material is 0.5wt%, and the specific preparation method is the same as that of Example 1, the only difference is that in step (1), the corresponding element materials are replaced according to the mass ratio of nickel iron manganese precursor: sodium carbonate: zinc oxide: magnesium oxide = 1:0.54:0.03:0.02.

[0041] Example 3 The same as Example 1, the only difference is that the mass ratio of the coating material to the primary sintered material in step (4) is different. The mass of the coating material in this embodiment is 0.2wt% of the mass of the primary sintered material. The preparation method of the sodium ion battery positive electrode material in this embodiment is the same as that in Example 1. During the preparation process, a certain amount of coating material can be weighed according to the ratio.

[0042] Example 4 The same as Example 1, the only difference is that in step (3), the ball milling speed is 250 r / min and the ball milling time is 6 h.

[0043] Comparative Example 1 The same as Example 1, the only difference is that the mass ratio of the coating material to the primary sintering material in step (4) is different. In this embodiment, the mass of the coating material is 0.1wt% of the mass of the primary sintering material.

[0044] Comparative Example 2 The same as Example 1, the only difference is that the mass ratio of the coating material to the primary sintering material in step (4) is different. In this embodiment, the mass of the coating material is 1.5wt% of the mass of the primary sintering material.

[0045] Comparative Example 3 The same as Example 1, the only difference is that the ball milling speed in step (3) is 100 r / min, the ball-to-material ratio used in the ball milling process is 1:1, and the ball milling time is 3 h. The remaining preparation steps in the material preparation process are the same as in Example 1.

[0046] Comparative Example 4 The same as Example 1, the only difference is that the ball milling speed in step (3) is 900 r / min, the ball-to-material ratio used in the ball milling process is 1:1, and the ball milling time is 2 h. The remaining preparation steps in the material preparation process are the same as in Example 1.

[0047] Test Example 1 Button cell assembly: The sodium ion battery layer oxygen cathode material obtained above was assembled into a button cell, and the active material, conductive carbon black and PVDF were mixed in a mass ratio of 9.4:0.3:0.3, and N-methylpyrrolidone solution was added to prepare an active material slurry, and then the slurry was evenly coated on an aluminum foil, vacuum dried at 110°C for 8h, and the cathode electrode sheet used was obtained by rolling and cutting. The metal sodium sheet was used as the counter electrode and the glass fiber was used as the diaphragm. The button cell was assembled in an argon-filled glove box, and the electrochemical performance test was carried out under the following conditions. The results are shown in Tables 1 and Figure 2~Figure 4 As shown; wherein the first week charge and discharge curves of the sodium ion battery positive electrode materials of Example 1 and Comparative Example 1 are as shown Figure 2 As shown, the rate performance is as follows Figure 3 As shown, the cycle performance is as follows Figure 4 shown.

[0048] Charge and discharge voltage range: 2V~4.1V; First week charge and discharge rate: 0.1C; Charge and discharge cycle rate: 1C; Charge and discharge cycle number: 50 cycles; Charging and discharging test environment: temperature is 25℃, humidity is 10%.

[0049] Table 1 Electrochemical performance test data of layered transition metal oxide cathode materials for sodium ion batteries It can be seen from the test results in Table 1 that compared with Examples 1 to 4, the materials prepared in Comparative Examples 1 to 4 have lower first-week charge and discharge specific capacity, discharge specific capacity at 1C rate, discharge specific capacity at 5C rate, and capacity retention rate after 50 cycles at 1C rate in the voltage range of 2V to 4.1V. The materials in Examples 1 to 4 have better electrochemical properties in the voltage range of 2V to 4.1V.

[0050] It can be seen from the above embodiments that by doping a certain proportion of transition metal elements during the preparation process, the internal crystal structure of the positive electrode material can be regulated, and the complex phase change of the material within the high voltage range can be inhibited, thereby making it have a higher specific capacity and cycle stability; at the same time, nano-titanic acid is used as the coating material, and a certain thickness of nano-titanic acid is coated on the surface of the primary sintered material by a suitable ball milling method, which stabilizes the structure of the material, reduces the residual alkali on the surface of the material, protects the electrolyte from erosion of the material and improves the ion transfer rate, so that it has excellent electrochemical properties.

[0051] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high voltage and long cycle sodium ion battery layer oxygen positive electrode material, characterized in that: The method comprises the following steps: S1, mixing the sodium-containing compound, the nickel-iron-manganese precursor, and the M-containing compound to obtain a first mixed material; S2, sintering the first mixed material for the first time, and then crushing, pulverizing and screening the first time to obtain a primary sintered material; S3, ball-milling and mixing the coating material and the primary sintered material to obtain a second mixed material; S4, sintering the second mixed material for the second time, and then crushing, pulverizing and screening for the second time to obtain a chemical formula of Na a Ni b Fe c Mn d M e O2 layer oxygen positive electrode material, wherein M is one or more of Ca, Ti, Cu, Zr, Zn, Mg and Al, a, b, c, d, e are the molar ratios of the corresponding elements in the material, 0.85≤a≤1, 0.2≤b≤0.5, 0.2≤c≤0.5, 0.2≤d≤0.5, 0.01≤e≤0.2, wherein b+c+d=1; The sodium-containing compound is sodium carbonate or sodium bicarbonate; The M-containing compound includes oxides containing Ca, Ti, Cu, Zr, Zn, Mg, and Al and / or hydroxides containing Ca, Ti, Cu, Zr, Zn, Mg, and Al; The coating material is nano-titanic acid; the mass of the coating layer is 0.2wt% to 1wt% of the mass of the primary sintered material.

2. The method according to claim 1, characterized in that The molar ratio of the sodium-containing compound, the nickel-iron-manganese precursor, and the M-containing compound is 0.85-1:1:0.01-0.

2.

3. The method according to claim 1, characterized in that In step S2, the first sintering is performed in a dry air atmosphere; the humidity of the dry air atmosphere is 0% to 30%, and the air intake flow rate is 10 L / min to 30 L / min.

4. The method according to claim 1, characterized in that: In step S2, the conditions for the first sintering are: heating to 600°C~800°C at a heating rate of 2°C / min~5°C / min and keeping warm for 4h~10h, then heating to 900°C~1000°C at a heating rate of 2°C / min~5°C / min and keeping warm for 8h~14h, and then cooling to room temperature at a cooling rate of 2°C / min.

5. The method according to claim 1, characterized in that In step S2, the mesh size of the first screening is 400 meshes.

6. The method according to claim 1, characterized in that The ball-to-material ratio used in the ball milling mixing process is 2:1-3:1, the diameter of the large ball is 20mm-26mm, the diameter of the medium ball is 10mm-15mm, the diameter of the small ball is 5mm-9mm, the ball milling speed is 200r / min-800r / min, and the ball milling time is 3h-6h.

7. The method according to claim 1, characterized in that In step S4, the second sintering is performed in a dry air atmosphere; the humidity of the dry air atmosphere is 0% to 30%, and the air intake flow rate is 10 L / min to 30 L / min.

8. The method according to claim 1, characterized in that In step S4, the conditions for the second sintering are: heating to 900°C~1000°C at a heating rate of 2°C / min~5°C / min, keeping the temperature for 5h~8h, and then cooling to room temperature at a cooling rate of 2°C / min.

9. The method according to claim 1, characterized in that: In step S4, the mesh size of the second screening is 300 meshes.

10. Use of the method according to any one of claims 1 to 9 in the preparation of sodium ion batteries.

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