High-entropy transition metal layered oxides, positive electrode materials, batteries, and methods of making the same

Abstract

The application discloses a high-entropy transition metal layered oxide, a positive electrode material, a battery and a preparation method thereof, and belongs to the technical field of sodium ion batteries. The application adopts a transition metal doping method to prepare a high-entropy positive electrode material, so as to improve and enhance the poor cycle stability and electrode material interface side reaction of a sodium ion battery made of sodium nickel manganese oxide as a positive electrode material, and to enhance the electrochemical performance of the sodium ion battery made of sodium nickel manganese oxide as a positive electrode material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium ion batteries, in particular to a high-entropy transition metal layered oxide, a positive electrode material, a battery and a preparation method thereof. BACKGROUND

[0002] With the vigorous development of global economy, finding new green energy to replace fossil energy has increasingly become the focus of attention. Lithium ion batteries, as energy storage and conversion elements, play an important role in the field of new energy. However, the limited resources and increasing prices limit the further application of lithium ion batteries in large-scale energy storage systems. Compared with lithium resources, sodium resources have the natural advantages of wide distribution and relatively low price, so sodium ion batteries have more potential for sustainable development.

[0003] However, due to the instability of sodium metal materials, the development of battery electrode materials is still the focus of the industry. In addition, compared with lithium ions, sodium ions have a larger radius, and the volume of the electrode material changes greatly during the embedding / extraction of sodium ions in the electrode material, resulting in lower specific capacity and poorer cycle stability of sodium ion batteries.

[0004] Chinese patent CN115020681A discloses a carbon-coated sodium iron sulfate positive electrode material and a preparation method thereof. The carbon-coated sodium iron sulfate positive electrode material includes an active sodium iron sulfate material and a carbon-based coating material. The carbon-based coating material uses one of carbon nanotubes, carbon fibers, reduced graphene oxide, graphene, conductive carbon black and activated carbon, and the mass ratio of the carbon-based coating material is 0.01-20%. This patent overcomes the problems of low sodium storage capacity and poor cycle stability of the sodium ion battery polyanion-type iron-based sulfate positive electrode material, but it uses acidic and alkaline solutions, which increases the danger and cost of the preparation process, has safety hazards and is not conducive to large-scale production.

[0005] In summary, there is a need to develop a method that can improve the specific capacity and cycle stability of sodium ion batteries. SUMMARY

[0006] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a high-entropy transition metal layered oxide, a positive electrode material, a battery and a preparation method thereof. A high-entropy positive electrode material is prepared by doping transition metals to improve the poor cycle stability and electrode material interface side reaction problems of sodium ion batteries made of nickel-manganese sodium acid as a positive electrode material, and to improve the electrochemical performance of sodium ion batteries made of nickel-manganese sodium acid as a positive electrode material.

[0007] The technical scheme of the present application is:

[0008] In a first aspect, the present application provides a preparation method of high-entropy transition metal layered oxide, comprising the following steps:

[0009] S1 dissolving a sodium source, a nickel source, a manganese source, a zinc source, a copper source and a titanium source in an organic solvent, and then performing ball milling treatment to obtain a slurry, and drying the slurry to obtain a precursor;

[0010] S2 performing annealing treatment on the precursor in an air atmosphere, and cooling to room temperature to obtain the high-entropy transition metal layered oxide.

[0011] Preferably, in step S1, the sodium source is one or both of sodium carbonate and sodium acetate; the zinc source is zinc oxide; the nickel source is one or more of nickel protoxide, nickel sesquioxide and nickel trioxide; the copper source is copper oxide; the manganese source is one or both of manganese dioxide and manganese sesquioxide; and the titanium source is titanium dioxide.

[0012] Preferably, in step S1, the rotation speed of the ball milling treatment is 400-600 rpm, the ball milling time is 10-15 h, the ball milling beads used in the ball milling treatment are zirconium oxide beads, stainless steel balls or agate balls, and the mass ratio of the ball milling beads to the slurry is 1:1.

[0013] Preferably, in step S1, the drying temperature is 60-80℃, and the drying time is 6-10 h.

[0014] Preferably, in step S2, the annealing treatment is: heating to 900-1000℃ at a heating rate of 2-5℃ / min, and the holding time is 15-20 h.

[0015] In a second aspect, the present application provides a high-entropy transition metal layered oxide prepared by the above preparation method, and the chemical general formula of the high-entropy transition metal layered oxide is Na x (Zn y Ni z Mn a Cu b Ti 1-y-z-a-b )O2, wherein 0.5≤x<1, 0.04≤y≤0.06, 0.2≤z≤0.4, 0.5≤a≤0.7, and 0.04≤b≤0.08.

[0016] In a third aspect, the present application provides a sodium-ion positive electrode material comprising the above high-entropy transition metal layered oxide, and the positive electrode material comprises an aluminum foil and a coating layer, and the coating layer is a mixture of carbon black, polyvinylidene fluoride and the high-entropy transition metal layered oxide.

[0017] In a fourth aspect, the application provides a preparation method of the sodium-ion positive electrode material, which comprises the following steps: mixing high-entropy transition metal layered oxide, carbon black and polyvinylidene fluoride in a mass ratio of 8:1:1 in N-methylpyrrolidone to obtain a mixture; and coating the mixture on an aluminum foil, and drying in vacuum to obtain the sodium-ion positive electrode material.

[0018] In a fifth aspect, the application further provides a sodium-ion battery comprising the sodium-ion positive electrode material.

[0019] Preferably, the sodium-ion battery has the sodium-ion positive electrode material as the positive electrode, has metallic sodium as the negative electrode, has an electrolyte comprising a solute and an organic solvent, has sodium perchlorate or NaPF6 as the solute, has one or more of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC) and fluoroethylene carbonate (FEC) as the organic solvent, and has a molar concentration of the solute in the electrolyte of 0.1-5 mol / L.

[0020] Compared with the prior art, the application has the following beneficial effects:

[0021] 1. The application adopts a transition metal doping method to prepare a high-entropy positive electrode material, so as to improve the poor cycle stability and electrode material interface side reaction of a sodium-ion battery made of sodium nickel manganese oxide as a positive electrode material, and improve the electrochemical performance of the sodium-ion battery made of sodium nickel manganese oxide as a positive electrode material.

[0022] 2. In the high-entropy transition metal layered oxide positive electrode material prepared by the application, zinc ions are doped into alkali metal layers, which effectively inhibits the sliding of transition metal layers after deep sodium extraction, and maintains a good sodium ion insertion path, so that the capacity is high and the cycle performance is stable during charging and discharging.

[0023] 3. The five doped transition metals form a high-entropy structure, and the synergistic effect of multiple transition metal elements improves the Fermi level of lattice oxygen, so that the capacity of reversible participation in oxidation and reduction is improved.

[0024] 4. The application adopts a high-temperature solid-phase method, which has low raw material cost, simple and easy-to-operate synthesis process, standardized operation, is convenient for large-scale industrial production, and has high practicality. In addition, the annealing treatment is carried out in an air atmosphere, which can avoid the consumption of a large amount of expensive high-purity nitrogen gas during sintering, and the use of air atmosphere can greatly reduce the preparation cost of the positive active material. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 FIG. 1 is an X-ray diffraction pattern of the high-entropy transition metal layered oxide prepared in Example 1 of the application.

[0026] Figure 2is the charge-discharge curve of the high-entropy transition metal layered oxide prepared in Example 1 of the present application at a current density of 0.1C (1C = 170mA·g -1 ).

[0027] Figure 3 is the cycle performance graph of the high-entropy transition metal layered oxide prepared in Example 1 of the present application at a current density of 1C (1C = 170mA·g -1 ).

[0028] Figure 4 is the cycle performance graph of the high-entropy transition metal layered oxide prepared in Example 1 of the present application at a current density of 10C (1C = 170mA·g -1 ). DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions of the present application will be described clearly and completely below in conjunction with the embodiments of the present application.

[0030] Example 1

[0031] Sodium carbonate, zinc oxide, nickel oxide, copper oxide, manganese dioxide and titanium dioxide with a molar ratio of 0.67:0.05:0.22:0.06:0.66:0.01 were dissolved in anhydrous ethanol and placed in a ball mill jar for thorough grinding. The rotation speed of the ball milling treatment was 400rpm, the ball milling time was 15h, and zirconium oxide beads were used as the ball milling beads. The mass ratio of the ball milling beads to the total mass of the raw materials was 1:1. The sodium carbonate was in excess by 5% to make up for the loss during high-temperature calcination. The ground slurry was dried in a forced air drying oven at 60℃ for 10h to obtain a precursor. The precursor was then pressed into a round sheet using a mold and placed in a muffle furnace for calcination in an air atmosphere at a heating rate of 2℃ / min to 900℃ for 20h to obtain a high-entropy transition metal layered oxide with a chemical formula of Na 0.67 Zn 0.05 Ni 0.22 Cu 0.06 Mn 0.66 Ti 0.01 O2.

[0032] The X-ray diffraction pattern of the high-entropy transition metal layered oxide prepared in Example 1 is shown in Figure 1 As can be seen from the figure, the high-entropy transition metal layered oxide prepared in Example 1 is a pure-phase P2-type layered structure. The first five cycles of charge-discharge performance of the high-entropy transition metal layered oxide prepared in Example 1 at a current density of 0.1C (1C = 170mA·g -1 ) is shown in Figure 2As shown in the figure, it can be seen from the figure that the high-entropy transition metal layered oxide prepared in Example 1 has very high initial charge and discharge efficiency. The 100-cycle cycle performance graph of the high-entropy transition metal layered oxide prepared in Example 1 at a current density of 1C (1C = 170mA·g -1 ) is as shown in Figure 3 As shown in the figure, it can be seen from the figure that the high-entropy transition metal layered oxide prepared in Example 1 has very high initial charge and discharge efficiency. The 100-cycle cycle performance graph of the high-entropy transition metal layered oxide prepared in Example 1 at a current density of 1C (1C = 170mA·g -1 ) is as shown in Figure 3 As shown in the figure, it can be seen from the figure that the high-entropy transition metal layered oxide prepared in Example 1 has very high initial charge and discharge efficiency. The 100-cycle cycle performance graph of the high-entropy transition metal layered oxide prepared in Example 1 at a current density of 1C (1C = 170mA·g -1 ) is as shown in Figure 4 As shown in the figure, it can be seen from the figure that the high-entropy transition metal layered oxide prepared in Example 1 has very high initial charge and discharge efficiency. The 100-cycle cycle performance graph of the high-entropy transition metal layered oxide prepared in Example 1 at a current density of 1C (1C = 170mA·g -1 ) is as shown in Figure 4 As shown in the figure, it can be seen from the figure that the high-entropy transition metal layered oxide prepared in Example 1 has very high initial charge and discharge efficiency. The 100-cycle cycle performance graph of the high-entropy transition metal layered oxide prepared in Example 1 at a current density of 1C (1C = 170mA·g -1 ) is as shown in

[0033] Example 2

[0034] Sodium carbonate, zinc oxide, nickel oxide, copper oxide, manganese dioxide and titanium dioxide with a molar ratio of 0.33:0.05:0.22:0.06:0.65:0.02 were dissolved in anhydrous ethanol and placed in a ball mill jar for thorough grinding. The rotation speed of the ball milling treatment was 500 rpm, the ball milling time was 12 h, the ball milling beads used were zirconia beads, and the mass ratio of the ball milling beads to the total mass of the raw materials was 1:1. The sodium carbonate was in excess by 5% to make up for the loss during high-temperature calcination. The ground slurry was dried in a forced air drying oven at 70°C for 8 h to obtain a precursor. The precursor was then pressed into a round disc using a mold and placed in a muffle furnace for calcination in an air atmosphere at a heating rate of 4°C / min to 950°C for 18 h to obtain a high-entropy transition metal layered oxide with a chemical formula of Na 0.67 Zn 0.05 Ni 0.22 Cu 0.06 Mn 0.65 Ti 0.02 O2.

[0035] Example 3

[0036] sodium carbonate, zinc oxide, nickel oxide, copper oxide, manganese dioxide and titanium dioxide in a molar ratio of 0.33:0.05:0.22:0.06:0.64:0.03 were dissolved in anhydrous ethanol, and were placed in a ball mill tank for grinding. The rotation speed of the ball milling treatment was 600 rpm, the ball milling time was 10 h, the zirconium oxide beads were used as the ball milling beads, the mass ratio of the ball milling beads to the total mass of the raw materials was 1:1, and the sodium carbonate was in excess by 5% to compensate for the loss in the high-temperature calcination process. The ground slurry was dried in a forced air drying oven at 80 °C for 6 h to obtain a precursor. The precursor was pressed into a round sheet using a mold, and was calcined in a muffle furnace in an air atmosphere at a temperature increasing rate of 5 °C / min to 1000 °C for 15 h to obtain a high-entropy transition metal layered oxide with a chemical formula of Na 0.6 7Zn 0.05 Ni 0.22 Cu 0.06 Mn 0.64 Ti 0.03 O2.

[0037] Example 4

[0038] sodium carbonate, zinc oxide, nickel oxide, copper oxide, manganese dioxide and titanium dioxide in a molar ratio of 0.33:0.05:0.22:0.06:0.66:0.01 were dissolved in anhydrous ethanol, and were placed in a ball mill tank for grinding. The rotation speed of the ball milling treatment was 450 rpm, the ball milling time was 12 h, the zirconium oxide beads were used as the ball milling beads, the mass ratio of the ball milling beads to the total mass of the raw materials was 1:1, and the sodium carbonate was in excess by 5% to compensate for the loss in the high-temperature calcination process. The ground slurry was dried in a forced air drying oven at 60 °C for 10 h to obtain a precursor. The precursor was pressed into a round sheet using a mold, and was calcined in a muffle furnace in an air atmosphere at a temperature increasing rate of 5 °C / min to 950 °C for 15 h to obtain a high-entropy transition metal layered oxide with a chemical formula of Na 0.67 Zn 0.05 Ni 0.22 Cu 0.06 Mn 0.66 Ti 0.01 O2.

[0039] Example 5

[0040] Sodium carbonate, zinc oxide, nickel oxide, copper oxide, manganese dioxide and titanium dioxide with a molar ratio of 0.33:0.05:0.22:0.06:0.66:0.01 were dissolved in anhydrous ethanol, and were placed in a ball mill tank for sufficient grinding. The rotation speed of the ball milling treatment was 600 rpm, the ball milling time was 11 h, the ball milling beads used were zirconia beads, the mass ratio of the ball milling beads to the total mass of the raw materials was 1:1, and the sodium carbonate was in excess by 5% to make up for the loss in the high-temperature calcination process. The ground slurry was dried in a forced air drying oven at 80°C for 8 h to obtain a precursor. The precursor was pressed into a round sheet using a mold, and was calcined in a muffle furnace in an air atmosphere at a heating rate of 5°C / min to 900°C for 19 h to obtain a high-entropy transition metal layered oxide with a chemical formula of Na 0.67 Zn 0.05 Ni 0.22 Cu 0.06 Mn 0.66 Ti 0.01 O2.

[0041] Example 6

[0042] Sodium carbonate, zinc oxide, nickel oxide, copper oxide, manganese dioxide and titanium dioxide with a molar ratio of 0.33:0.05:0.22:0.06:0.66:0.01 were dissolved in anhydrous ethanol, and were placed in a ball mill tank for sufficient grinding. The rotation speed of the ball milling treatment was 600 rpm, the ball milling time was 11 h, the ball milling beads used were zirconia beads, the mass ratio of the ball milling beads to the total mass of the raw materials was 1:1, and the sodium carbonate was in excess by 5% to make up for the loss in the high-temperature calcination process. The ground slurry was dried in a forced air drying oven at 80°C for 8 h to obtain a precursor. The precursor was pressed into a round sheet using a mold, and was calcined in a muffle furnace in an air atmosphere at a heating rate of 5°C / min to 900°C for 19 h to obtain a high-entropy transition metal layered oxide with a chemical formula of Na 0.67 Zn 0.05 Ni 0.22 Cu 0.06 Mn 0.66 Ti 0.01 O2.

[0043] Comparative Example 1

[0044] The difference from Example 1 is that no zinc oxide is added, and the chemical formula of the transition metal layered oxide prepared is Na 0.67 Ni 0.22 Cu 0.06 Mn 0.66 Ti 0.06 O2.

[0045] Comparative Example 2

[0046] The difference from Example 1 is that no titanium dioxide is added, and the chemical general formula of the prepared transition metal layered oxide is Na 0.67 Zn 0.05 Ni 0.22 Cu 0.06 Mn 0.667 O2.

[0047] Comparative Example 3

[0048] The difference from Example 1 is that no copper oxide is added, and the chemical general formula of the prepared transition metal layered oxide is Na 0.67 Zn 0.05 Ni 0.28 Mn 0.66 Ti 0.01 O2.

[0049] The high-entropy transition metal layered oxide prepared in Examples 1-6 and Comparative Examples 1-3 is mixed with carbon black and polyvinylidene fluoride at a mass ratio of 8:1:1 in N-methylpyrrolidone to obtain a coating layer, and the coating layer is coated on an aluminum foil to obtain a sodium ion positive electrode material after vacuum drying. The sodium ion battery is assembled by taking the positive electrode material as the positive electrode, taking metallic sodium as the negative electrode, and taking an electrolyte including a solute and an organic solvent, the solute being NaPF6 and the organic solvent being ethylene carbonate (EC) and dimethyl carbonate (DMC), wherein the volume ratio of EC to DMC is 1:1, and the molar concentration of the solute in the electrolyte is 1 mol / L.

[0050] The sodium ion batteries of Examples 1 and Comparative Examples 1-3 are tested for performance, and their charge-discharge performance at a current density of 10C (1C = 170mA·g -1 ) is tested, and the test results are shown in Table 1:

[0051] Table 1

[0052] [CATALOGUE] 10 initial charge-discharge specific capacity at a current density of 0.1 C (mAh.g -1 ​ Example 1 90 Comparative Example 1 60 Comparative Example 2 66.25 Comparative Example 3 74.3

[0053] The sodium ion batteries of Examples 1-6 and Comparative Examples 1-3 are tested for performance, and their cycle performance at a current density of 10C (1C = 170mA·g -1 ) for 500 cycles is tested, and the test results are shown in Table 2:

[0054] Table 2

[0055] Capacity retention rate (%) at 10C for 500 cycles Example 1 99.8 Example 2 95 Example 3 94 Example 4 94 Example 5 96 Example 6 93 Comparative Example 1 85 Comparative Example 2 88 Comparative Example 3 86

[0056] As can be seen from Table 1-2, the initial charge-discharge specific capacity and cycle performance of the sodium ion battery of Comparative Example 1-3 are lower than those of Examples 1-6, because Zn can play a supporting role in the sodium metal layer, is not detached and embedded in the charge-discharge process, can stabilize the overall structure, and improve the cycle performance; Cu and Ti can replace the TM site in the TMO6 octahedron of the transition metal layer, disrupt the order of Ni / Mn, form a strong covalent bond with lattice oxygen, and play a role in stabilizing lattice oxygen and crystal structure.

Claims

1. A method for preparing a high-entropy transition metal layered oxide, characterized in that, The method comprises the following steps: S1: dissolving a sodium source, a nickel source, a manganese source, a zinc source, a copper source and a titanium source in an organic solvent, and then performing ball milling to obtain a slurry, and drying the slurry to obtain a precursor; S2 anneals the precursor in an air atmosphere, and after cooling to room temperature, a high-entropy transition metal layered oxide is obtained, which has a chemical general formula of Na x (Zn y Ni z Mn a Cu b Ti 1-y-z-a-b )O2, wherein 0.5≤x<1, 0.04≤y≤0.06, 0.2≤z≤0.4, 0.5≤a≤0.7, 0.04≤b≤0.

08.

2. The method of producing a high-entropy transition metal layered oxide according to claim 1, wherein In step S1, the sodium source is one or both of sodium carbonate and sodium acetate; the zinc source is zinc oxide; the nickel source is one or more of nickel protoxide, nickel sesquioxide and nickel trioxide; the copper source is copper oxide; the manganese source is one or both of manganese dioxide and manganese sesquioxide; and the titanium source is titanium dioxide.

3. The method of producing a high-entropy transition metal layered oxide according to claim 1, wherein In step S1, the rotation speed of the ball milling is 400-600 rpm, the ball milling time is 10-15 h, and the mass ratio of the ball milling beads to the slurry is 1:

1.

4. The method of producing a high-entropy transition metal layered oxide according to claim 1, wherein In step S1, the drying temperature is 60-80℃, and the drying time is 6-10 h.

5. The method of producing a high-entropy transition metal layered oxide according to claim 1, wherein In step S2, the annealing treatment is performed at a temperature rising rate of 2-5℃ / min to a temperature of 900-1000℃, and the holding time is 15-20 h.

6. A sodium-ion cathode material comprising a high-entropy transition metal layered oxide prepared by the method for preparing a high-entropy transition metal layered oxide according to any one of claims 1 to 5, characterized in that The positive electrode material comprises an aluminum foil and a coating layer, and the coating layer is a mixture of carbon black, polyvinylidene fluoride and high-entropy transition metal layered oxide.

7. The method for preparing the sodium-ion cathode material as described in claim 6, characterized in that, The high-entropy transition metal layered oxide, the carbon black and the polyvinylidene fluoride are mixed in N-methylpyrrolidone at a mass ratio of 8:1:1 to obtain a mixture, the mixture is coated on an aluminum foil, and the sodium ion positive electrode material is obtained after vacuum drying.

8. A sodium ion battery comprising the sodium ion positive electrode material of claim 6.

9. The sodium-ion battery of claim 8, wherein, The sodium ion battery uses the sodium ion positive electrode material of claim 7 as the positive electrode, uses metallic sodium as the negative electrode, and uses an electrolyte comprising a solute and an organic solvent, wherein the solute is sodium perchlorate or NaPF6, the organic solvent is one or more of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate and fluoroethylene carbonate, and the molar concentration of the solute in the electrolyte is 0.1-5 mol / L.

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