Bimetal oxide coated sodium ion layered oxide material and preparation method thereof

Abstract

The invention discloses a bimetallic oxide coated sodium ion layered oxide material and a preparation method thereof in the field of chemical power sources, the chemical expression of the material is NaxNiaMnbMcO2 at bimetallic oxide, and the preparation method comprises the following steps: uniformly mixing a sodium source, a precursor and a transition source, then carrying out primary sintering, cooling and crushing to obtain a primary sintered product; and uniformly mixing the primary sintered product with the bimetallic oxide, and then carrying out secondary sintering, cooling and crushing to obtain the bimetallic oxide coated sodium ion layered oxide material. The preparation method has the beneficial effects that the coating process is simplified, and the preparation method is suitable for large-scale production. The surface of the material is provided with a double-metal oxide coating layer, and the coating layer can effectively improve the conductivity of the material, reduce impedance and restrain the problems of corrosion of electrolyte to the surface of the material, interface side reaction and the like. The cycling stability and the rate capability of the battery can be effectively improved, and meanwhile, the self capacity is not influenced.

Description

Technical Field

[0001] The invention relates to the field of chemical power sources, and in particular to a sodium ion layered oxide material coated with a bimetallic oxide and a preparation method thereof. Background Art

[0002] Rechargeable lithium batteries are currently widely used in personal life, social production and national armed forces (such as convenient electronic devices, electric vehicles, large energy storage systems, handheld devices, missiles, satellites, etc.), which has greatly changed our lives and times. However, the reserves of lithium resources are small and unevenly distributed, with more than 60% of the exploitable lithium resources located in remote areas, and the high cost cannot meet the needs of electric vehicles and energy storage systems. Therefore, concerns about the availability of lithium sources have triggered research interest in developing new energy storage technologies using earth-abundant elements.

[0003] The concept of sodium-ion batteries was proposed in the 1970s and 1980s with the development of graphite / / LiCoO2 batteries, but because they were inferior to lithium-ion batteries in all aspects, they were quickly shelved after being proposed. In recent years, due to the lack of lithium resources and the development of large-scale energy storage systems, the abundant sodium resources have once again attracted people's attention. The widespread application of mobile energy storage systems in various electric devices has increased the demand and use of lithium-ion batteries. Therefore, the advantages of sodium resources, moderate energy density and electrochemical properties have attracted the research of sodium-ion batteries. On the other hand, sodium-ion batteries show competitive advantages in fixed energy storage systems, which rely primarily on high power density, long cycle life and low operating costs.

[0004] Among the cathode materials for sodium-ion batteries, layered metal oxides have the advantages of compact crystal structure, low cost, and easy synthesis, and are a promising class of cathode materials. However, they are currently facing some problems. First, there are changes in the bulk structure and interlayer spacing caused by inevitable structural phase changes. Secondly, the diffusion kinetics are slow due to the large radius of sodium ions. Finally, there is the problem of interface degradation of layered oxide cathode materials. Side reactions of the electrolyte and dissolution of metals have reduced the electrochemical performance of layered oxides as cathode materials. Therefore, how to improve their electrochemical performance is of great significance for practical applications. Surface coating is a relatively common modification method that strengthens the surface structure, inhibits side reactions, prevents the dissolution of transition metal ions, etc., improves the stability of the interface between the cathode material and the electrolyte, and thus improves the electrochemical performance. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a sodium ion layered oxide material coated with a bimetallic oxide and a preparation method thereof, and the present invention is achieved through the following technical solutions.

[0006] Sodium-ion layered oxide material coated with double metal oxide, the chemical formula of the material is NaxNiaMnbMcO2@double metal oxide, where NaxNiaMnbMcO2 is sodium-ion layered oxide, Na is sodium source, NiaMnb is precursor, M is transition source, M is at least one of transition metals Co, Cu, Fe, Ti, Mg, Zr, Y, W, Sr, V, Al, 2 / 3≤x≤1, 0<a, b, c<1, and the double metal oxide is uniformly coated on the surface of the sodium-ion layered oxide.

[0007] Preferably, x is 2 / 3 or 1, 0.33≤a<1, 0.33≤b<1, 0<c≤0.33.

[0008] Preferably, the molar ratio of the double metal oxide to the whole material is 0.01%-0.2%.

[0009] Preferably, the coating thickness of the double metal oxide is 10-50nm.

[0010] Preparation method of sodium-ion layered oxide material coated with double metal oxide, the method includes the following steps:

[0011] (1) Feed and mix sodium source, precursor and transition source according to stoichiometric ratio to obtain a uniform mixture, where the sodium source is in excess of 1%-10%;

[0012] (2) Place the mixture obtained in step (1) in an oxygen atmosphere furnace for sintering;

[0013] (3) After crushing the sintered product of step (2), add double metal oxide and conduct secondary sintering, the temperature is 400-800°C, and the heat preservation time is 5-10h;

[0014] (4) Crush and sieve the sintered product of step (3) to obtain sodium-ion layered oxide material coated with double metal oxide, and this material can be used as the positive electrode material of sodium-ion battery.

[0015] Preferably, the sodium source in step (1) is one of sodium oxide, sodium hydroxide, sodium bicarbonate and sodium carbonate; the precursor is one of hydroxide and oxide; the transition source is one or more of oxide, hydroxide, carbonate and acetate.

[0016] Preferably, in step (2), the sintering temperature is 800-1000°C, the heating rate is 1-10min / °C, and the heat preservation time is 24-48h.

[0017] Preferably, in step (3), the double metal oxide is one or several of antimony tin oxide, indium tin oxide, cesium tungsten oxide and cadmium tin oxide.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. The method for preparing the positive electrode of the present invention is solid-phase coating, which simplifies the coating process, has a simple synthesis method, high production efficiency. At the same time, the raw materials used in the present invention are easily available, non-toxic, and low in cost. The production process does not require the protection of special processes and is suitable for large-scale production.

[0020] 2. The material prepared by the present invention has a double-metal oxide coating layer on its surface. This coating layer can effectively improve the conductivity of the material, reduce the impedance, and inhibit problems such as the corrosion of the electrolyte on the material surface and interfacial side reactions.

[0021] 3. The surface coating strategy of the sodium-ion layered oxide of the present invention can effectively improve the cycle stability and rate performance of the battery, while not affecting its own capacity, providing a new research idea for the industrialization of sodium-ion batteries. Specific Embodiments

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] A sodium-ion layered oxide material coated with a double-metal oxide, the chemical formula of the material is NaxNiaMnbMcO2@double-metal oxide, where NaxNiaMnbMcO2 is a sodium-ion layered oxide, Na is a sodium source, NiaMnb is a precursor, M is a transition source, and M is at least one of transition metals Co, Cu, Fe, Ti, Mg, Zr, Y, W, Sr, V, Al. 2 / 3 ≤ x ≤ 1, 0 < a, b, c < 1. The double-metal oxide is uniformly coated on the surface of the sodium-ion layered oxide. When x is 2 / 3, it indicates that the sodium-ion layered oxide is in a P2-phase structure; when x is 1, it indicates that the sodium-ion layered oxide is in an O3-phase structure. x is 2 / 3 or 1, 0.33 ≤ a < 1, 0.33 ≤ b < 1, 0 < c ≤ 0.33. The molar ratio of the double-metal oxide to the whole material is 0.01% - 0.2%, and the coating thickness of the double-metal oxide is 10 - 50 nm.

[0024] This application uses a sodium-ion layered oxide as a matrix and coats a double-metal oxide on the surface of the matrix. When x is 2 / 3, it indicates that the sodium-ion layered oxide is in a P2-phase structure; when x is 1, it indicates that the sodium-ion layered oxide is in an O3-phase structure.

[0025] A method for preparing a sodium-ion layered oxide material coated with a double-metal oxide, the method comprising the following steps:

[0026] (1) mixing a sodium source, a precursor and a transition source according to a stoichiometric ratio to obtain a uniform mixture, wherein the sodium source is in excess of 1% to 10%;

[0027] In the above synthesis steps, the sodium source is one of sodium oxide, sodium hydroxide, sodium bicarbonate and sodium carbonate; the precursor is one of hydroxide and oxide; and the transition source is one or more of oxide, hydroxide, carbonate and acetate.

[0028] (2) placing the mixture obtained in step (1) in an oxygen atmosphere furnace for sintering;

[0029] In the above synthesis steps, the sintering temperature is 800-1000°C, the heating rate is 1-10min / °C, and the insulation time is 24-48h.

[0030] (3) After the sintered product of step (2) is crushed, a bimetallic oxide is added and a second sintering is performed at a temperature of 400-800° C. and a holding time of 5-10 h;

[0031] In the above synthesis steps, the bimetallic oxide is one or more of antimony tin oxide (ATO), indium tin oxide (ITO), cesium tungsten oxide (CTO-1) and cadmium tin oxide (CTO-2).

[0032] Bimetallic oxides are semiconductor conductive materials with good conductivity, stable chemical properties, small particle size, and uniform composition. Compared with single transition metal oxides, they have better conductivity. As a coating layer for sodium ion layered oxides, they can significantly improve the electronic conductivity of the overall material, while preventing further erosion by the electrolyte, reducing the occurrence of interfacial side reactions, and improving cycle stability.

[0033] (4) crushing and sieving the sintered product of step (3) to obtain a sodium ion layered oxide material coated with a bimetallic oxide, which can be used as a positive electrode material for a sodium ion battery.

[0034] The present invention has the following specific embodiments.

[0035] Example 1

[0036] Preparation of P2-Na0.67Ni0.33Mn0.33Zr0.33O2@bimetallic oxide layered cathode material

[0037] (1) Weigh 0.33 mol of sodium carbonate, 0.33 mol of nickel-manganese precursor, 0.33 mol of zirconium oxide, and 0.33 mol of manganese oxide in a mortar and grind them evenly.

[0038] (2) The mixture obtained in step (1) is placed in a porcelain boat, pressed and cut into pieces, and then placed in a muffle furnace for calcination at a heating rate of 5°C / min. After heating to 950°C, the mixture is kept warm for 15 hours and cooled to room temperature to obtain P2-Na0.67Ni0.33Mn0.33Zr0.33O2 sodium ion layered oxide.

[0039] (3) Weigh an appropriate amount of the above-mentioned P2-Na0.67Ni0.33Mn0.33Zr0.33O2 sodium ion layered oxide, add 1wt% antimony tin oxide (ATO), mix in a mixer for 40 minutes, set the speed to 1200r / min, and place in a muffle furnace for calcination at a heating rate of 5°C / min. After heating to 500°C, keep warm for 10 hours, and cool to room temperature to obtain P2-Na0.67Ni0.33Mn0.33Zr0.33O2@ATO bimetallic oxide-coated sodium ion layered oxide material.

[0040] The obtained P2-Na0.67Ni0.33Mn0.33Zr0.33O2@ATO bimetallic oxide-coated sodium ion layered oxide material, conductive additive SP, and binder PVDF are mixed and dissolved in NMP in a mass ratio of 8:1:1, and a uniform slurry is obtained after stirring. The slurry is then evenly coated on the surface of the aluminum foil with a 200μm scraper, dried, and sliced ​​to obtain the desired electrode sheet.

[0041] Example 2

[0042] The operation steps are the same as those in Example 1, except that the coating material is changed to 0.5 wt % antimony tin oxide (ATO).

[0043] Example 3

[0044] The operation steps are the same as those in Example 1, except that the coating material is changed to 2 wt % antimony tin oxide (ATO).

[0045] Example 4

[0046] The operation steps are the same as those in Example 1, except that the coating material is changed to 3 wt % antimony tin oxide (ATO).

[0047] Example 5

[0048] The operation steps are the same as those in Example 1, except that the coating material is changed to 1 wt % indium tin oxide (ITO).

[0049] Example 6

[0050] The operation steps are the same as those in Example 1, except that the coating material is changed to 1 wt % cesium tungsten oxide (CTO-1).

[0051] Example 7

[0052] The operation steps are the same as those in Example 1, except that the coating material is changed to 1 wt % cadmium tin oxide (CTO-2).

[0053] Comparative Example 1

[0054] The operation steps are the same as steps (1) and (2) of Example 1, and the electrode sheet is directly made using P2-Na0.67Ni0.33Mn0.33Zr0.33O2 sodium ion layered oxide.

[0055] Application Examples

[0056] Electrochemical performance test

[0057] Electrochemical performance test: button cells were assembled with the pole pieces obtained in Examples 1-7 and Comparative Example 1 as positive electrodes, glass fiber as separators, metal sodium sheets as negative electrodes, and 1 mol / L NaClO4 (PC+5% FEC) as electrolyte. The cells were first activated for 3 cycles at a current density of 10 mA / g, and then charged and discharged at a current density of 100 mA / g. The electrochemical performance of the button cells corresponding to the materials in the examples of the present invention and the comparative examples was tested, and the results are shown in the table below.

[0058]

[0059] From the test results in the above table, it can be seen that after the sodium ion layered oxide is coated with a bimetallic oxide, although the first cycle discharge capacity of the battery is slightly reduced, the capacity retention rate after 200 cycles is significantly improved. For example, in Example 1, the 200 cycle capacity retention rate is 93%, while the 200 cycle capacity retention rate of the uncoated original positive electrode material comparative example 1 is 88%.

[0060] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. Sodium ion layered oxide materials coated with bimetallic oxides, It is characterized in that The chemical formula of the material is NaxNiaMnbMcO 2 @double metal oxide, where NaxNiaMnbMcO 2 is a sodium ion layered oxide, Na is the sodium source, NiaMnb is the precursor, M is the transition source, M is at least one of the transition metals Co, Cu, Fe, Ti, Mg, Zr, Y, W, Sr, V, Al, 2 / 3 ≤ x ≤ 1, 0 < a, b, c < 1, and the double metal oxide is uniformly coated on the surface of the sodium ion layered oxide.

2. The sodium ion layered oxide material coated with a bimetallic oxide according to claim 1, It is characterized in that x is 2 / 3 or 1, 0.33≤a<1, 0.33≤b<1, 0 <c≤0.33。 3. The sodium ion layered oxide material coated with a bimetallic oxide according to claim 1, It is characterized in that The molar ratio of the bimetallic oxide to the overall material is 0.01%-0.2%.

4. The sodium ion layered oxide material coated with a bimetallic oxide according to claim 1, It is characterized in that The coating thickness of the bimetallic oxide is 10-50 nm.

5. A method for preparing a sodium ion layered oxide material coated with a bimetallic oxide according to any one of claims 1 to 4, It is characterized in that The method comprises the following steps: (1) mixing a sodium source, a precursor and a transition source according to a stoichiometric ratio to obtain a uniform mixture, wherein the sodium source is in excess of 1% to 10%; (2) placing the mixture obtained in step (1) in an oxygen atmosphere furnace for sintering; (3) After the sintered product of step (2) is crushed, a bimetallic oxide is added and a second sintering is performed at a temperature of 400-800° C. and a holding time of 5-10 h; (4) crushing and sieving the sintered product of step (3) to obtain a sodium ion layered oxide material coated with a bimetallic oxide, which can be used as a positive electrode material for a sodium ion battery.

6. The method for preparing the bimetallic oxide-coated sodium ion layered oxide material according to claim 5, It is characterized in that The sodium source in step (1) is one of sodium oxide, sodium hydroxide, sodium bicarbonate and sodium carbonate; the precursor is one of hydroxide and oxide; and the transition source is one or more of oxide, hydroxide, carbonate and acetate.

7. The method for preparing the bimetallic oxide-coated sodium ion layered oxide material according to claim 5, It is characterized in that In the step (2), the sintering temperature is 800-1000° C., the heating rate is 1-10 min / ° C., and the insulation time is 24-48 h.

8. The method for preparing the bimetallic oxide-coated sodium ion layered oxide material according to claim 5, It is characterized in that In the step (3), the bimetallic oxide is one or more of antimony tin oxide, indium tin oxide, cesium tungsten oxide and cadmium tin oxide.

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