Manganese-based sodium-ion battery cathode material that suppresses the Jahn-Teller effect and its manufacturing method

Abstract

To provide a positive electrode material for a manganese-based sodium ion battery that suppresses Jahn-Teller effect, and a method for manufacturing the same.SOLUTION: With a positive electrode material for a manganese-based sodium ion battery that suppresses Jahn-Teller effect, a titanium dioxide thin film is deposited on a surface of the positive electrode material for the manganese-based sodium ion battery using a high-power output magnetron sputtering technique, and thereafter a nitrogen-doped graphite carbon thin film is deposited using a medium-frequency magnetron sputtering technique. The titanium dioxide coating layer provides a frame structure, effectively separates an electrode material from an electrolyte, prevents the material from being dissolved in the electrolyte and causing irreversible loss, effectively suppresses the Jahn-Teller effect, and improves stability of a material structure. A nitrogen-doped graphite carbon coating layer can comprehensively improve electrochemical properties of the material in order to effectively improve conductivity performance of an anode material.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a manganese-based sodium ion battery positive electrode material, specifically to a manganese-based sodium ion battery positive electrode material that suppresses the Jahn-Teller effect and a manufacturing method thereof, which belong to the technical fields of composite materials and battery materials. [Background technology]

[0002] With the widespread application of fossil energy, environmental pollution and energy crisis have become the two major world problems at present, and the development of new energy devices based on electrochemistry is of great importance to reduce environmental pollution and solve the energy crisis. Due to the scarcity of lithium reserves and the abundance of sodium reserves in the earth's crust, sodium-ion batteries (SIBs) arouse the interest of more and more industrial sectors / researchers to replace lithium batteries (LIBs) as energy storage devices. In the earth's crust, manganese resources are abundant and the cost is low, and manganese-based materials have made great progress as positive electrode materials for sodium-ion batteries. Here, sodium manganese oxide positive electrode materials NaxMnO2 with different sodium contents (x) show interesting battery performance and attract widespread attention. However, in most layered (x>0.5) and tunnel-type (x<0.5) manganese oxides, during the charge / discharge process, after Mn4+ is reduced to Mn3+, the Jahn-Teller effect by Mn3+ ions significantly distorts the local crystal lattice structure and reduces the electrochemical stability.

[0003] In order to solve the above problems, Patent Document 1 discloses a modified sodium ion battery positive electrode material and its manufacturing method and use, in which pyrophosphate-sodium phosphate is used as a core material for the sodium ion battery positive electrode material, and a carbon coating layer and an ALPO4 coating layer are provided on the surface of the core material to form an egg yolk-shell structure. Patent Document 2 discloses a modified sodium ion battery positive electrode material and its manufacturing method and use, which includes the steps of (1) adding a titanium source compound, an aluminum source compound, and a β-diketone stabilizer to a solvent and dissolving them sufficiently to obtain a solution A, (2) dissolving a sodium-containing compound in deionized water to obtain a soluble alkaline solution, adding the solution A to the soluble alkaline solution to obtain a solution B, (3) adding a sodium ion battery positive electrode material to the solution B, stirring sufficiently, and drying to obtain a mixed powder, and (4) heat-treating, pulverizing, and sieving the obtained mixed powder to obtain a coated sodium ion battery positive electrode material. However, in the above solutions, impurities are easily introduced during the formation of the coating layer under the conditions of liquid phase reaction, and the coating layer has weak bonding strength and the thickness cannot be controlled, which greatly limits the improvement of the stability of the material structure. Furthermore, the manufacturing process of the above solutions is complicated, making it difficult to achieve industrial production. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] China patent CN115224265A [Patent Document 2] China patent CN115295790A Summary of the Invention [Problem to be solved by the invention]

[0005] In response to the above technical problems, the present invention provides a manganese-based sodium ion battery positive electrode material that suppresses the Jahn-Teller effect, and a method for producing the same. [Means for solving the problem]

[0006] The manganese-based sodium ion battery positive electrode material suppressing the Jahn-Teller effect according to the present invention is firstly prepared by depositing a titanium dioxide thin film on the surface of the manganese-based sodium ion battery positive electrode material using high-power magnetron sputtering technology, and then depositing a nitrogen-doped graphite carbon thin film using intermediate frequency magnetron sputtering technology. The specific manufacturing process is as follows: (1) placing the NaxMnO2 electrode powder on a rotating tool rack in a vacuum coating chamber of a magnetron sputtering apparatus after drying, and adjusting the target interval to evacuate to 10-4 PA, where NaxMnO2 includes a tunnel oxide when x<0.5 and a layered P2 structure oxide when x>0.5, and drying the NaxMnO2 electrode powder in an oven at 110°C under vacuum for 120 min; Argon gas is introduced, the chamber working pressure is adjusted to 1.1 Pa, and high-power magnetron sputtering technology is adopted to sputter the titanium dioxide target to deposit titanium dioxide thin film. The duty ratio of the high-power power supply is 0.1, the current of the titanium dioxide target is 0.8-1A, the output power is 400-500W, and the thickness of the titanium dioxide thin film is 8nm. (3) introducing nitrogen gas, adjusting the flow ratio of argon gas to nitrogen gas to be 5:1 to 2:1, maintaining the chamber working pressure at 1.1 Pa, and depositing the nitrogen-doped graphite carbon thin film by adopting intermediate frequency magnetron sputtering technology, wherein the duty ratio of the intermediate frequency power supply is 0.6, the current of the graphite target is 1 A, the output power is 600 W, and the thickness of the obtained nitrogen-doped graphite carbon thin film is 9 nm.

[0007] The structure schematic diagram of the manganese-based sodium ion battery positive electrode material suppressing the Jahn-Teller effect prepared by the present invention is shown. The titanium dioxide coating layer provides a frame structure and improves the stability of the material structure, and the nitrogen-doped graphite carbon coating layer can effectively improve the conductive performance of the positive electrode material. At the same time, the titanium dioxide and carbon coating layers can prevent direct contact between the electrolyte and the active material, stabilize the electron transfer rate at the solid / liquid interface, and improve the ion diffusion rate, thereby comprehensively improving the electrochemical properties of the material. The prepared manganese-based sodium ion battery positive electrode material is assembled into a sodium ion half cell, and in the electrolyte (1.0MNaClO4 in PC:FEC=95:5 Vol%), good rate characteristics and excellent cycle stability are shown. Effect of the Invention

[0008] The present invention has the following advantageous effects compared to the prior art. The present invention deposits a titanium dioxide thin film coating layer on the surface of the manganese-based sodium ion battery positive electrode material, which can effectively separate the material from the electrolyte, avoid the material dissolving in the electrolyte causing irreversible loss, effectively inhibit the Jahn-Teller effect, and ensure the thermal stability of the material; furthermore, by depositing a nitrogen-doped graphitic carbon thin film, the conductive performance of the positive electrode material is effectively improved. At the same time, the nitrogen doping increases the active sites and promotes the transfer of sodium ions, thereby comprehensively improving the electrochemical properties of the material. 2. The manufacturing process of the present invention is not related to the conditions of liquid phase reaction, and can effectively avoid the introduction of impurities. The manufactured thin film has excellent bonding strength, the experimental process is highly controllable, the efficiency is high, the pollution is small, and it has wide market applicability. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing the structure of a manganese-based sodium ion battery positive electrode material for suppressing the Jahn-Teller effect produced in the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the preparation and performance of the manganese-based sodium ion battery positive electrode material suppressing the Jahn-Teller effect according to the present invention will be described in detail with reference to specific examples.

[0011] Example 1 (1) Experimental conditions for thin film deposition: The NaxMnO2 (x≦1) electrode powder was dried in an oven under vacuum conditions at 110°C for 120 min, then placed on the rotating tool rack in the vacuum coating chamber of the magnetron sputtering device, the target interval was adjusted, the device was evacuated to 10~4 Pa, and the rotating tool rack and sputtering target were started. (2) Preparation of titanium dioxide thin film: Argon gas was introduced, the chamber working pressure was adjusted to 1.1 Pa, and high-power magnetron sputtering technology was adopted to sputter the titanium dioxide target to deposit the titanium dioxide thin film: the duty ratio of the high-power power supply was 0.1, the titanium dioxide target current was 1 A, the output power was 500 W, and the thickness of the titanium dioxide thin film was 8 nm. (3) Preparation of nitrogen-doped graphite carbon thin film: Nitrogen gas was introduced, the flow ratio of argon gas to nitrogen gas was adjusted to 5:1, the chamber pressure was maintained at 1.1 Pa, and the graphite target was sputtered by intermediate frequency magnetron sputtering technology to deposit the nitrogen-doped graphite carbon thin film: the duty ratio of the intermediate frequency power supply was 0.1, the graphite target current was 1 A, the output power was 600 W, and the thickness of the nitrogen-doped graphite carbon thin film was 9 nm. (4) When assembled into a sodium ion half cell, the initial discharge specific capacities reached 111.5mAh / g, 108.5mAh / g, 105.1mAh / g and 101.3mAh / g or more at current densities of 0.1C, 0.5C, 1C and 2C in an electrolyte (1.0M NaClO4 in PC:FEC=95:5 Vol%), respectively, and showed good rate characteristics. After 100 cycles at a current density of 0.1C, the specific capacity reached 99.3mAh / g or more, showing excellent cycle stability.

[0012] Example 2 (1) Experimental conditions for thin film deposition: The NaxMnO2 (x≦1) electrode powder was dried in an oven under vacuum conditions at 110°C for 120 min, then placed on the rotating tool rack in the vacuum coating chamber of the magnetron sputtering device, the target interval was adjusted, the device was evacuated to 10~4 Pa, and the rotating tool rack and sputtering target were started. (2) Preparation of titanium dioxide thin film: Argon gas was introduced, the chamber working pressure was adjusted to 1.1 Pa, and high-power magnetron sputtering technology was used to sputter titanium dioxide to deposit titanium dioxide thin film. The duty ratio of the high-power power supply was 0.1, the titanium dioxide target current was 0.8 A, the output power was 400 W, and the thickness of the titanium dioxide thin film was 8 nm. (3) Preparation of nitrogen-doped graphite carbon thin film: Nitrogen gas was introduced, the air flow ratio of argon gas and nitrogen gas was adjusted to 2:1, the chamber air pressure was kept at 1.1 Pa, and the graphite target was sputtered by adopting intermediate frequency magnetron sputtering technology: the intermediate frequency power supply duty ratio was 0.1, the graphite target current was 1A, the output power was 600W, and the thickness of the nitrogen-doped graphite carbon thin film was 9nm. (4) When assembled into a sodium ion half cell, the initial discharge specific capacities reached 109.9mAh / g, 106.5mAh / g, 102.1mAh / g, and over 99.5mAh / g at current densities of 0.1C, 0.5C, 1C, and 2C in an electrolyte (1.0M NaClO4 in PC:FEC=95:5 vol%), respectively, demonstrating good rate characteristics. After 100 cycles at a current density of 0.1C, the specific capacity reached over 101.2mAh / g, demonstrating excellent cycle stability.

[0013] Example 3 (1) Experimental conditions for thin film deposition: The NaxMnO2 (x≦1) electrode powder was dried in an oven under vacuum conditions at 110°C for 120 min, then placed on the rotating tool rack in the vacuum coating chamber of the magnetron sputtering device, the target interval was adjusted, the device was evacuated to 10~4 Pa, and the rotating tool rack and sputtering target were started. (2) Preparation of titanium dioxide thin film: Argon gas was introduced, the chamber working pressure was adjusted to 1.1 Pa, and high-power magnetron sputtering technology was used to sputter the titanium dioxide target to deposit titanium dioxide thin film. The duty ratio of the high-power power supply was 0.1, the titanium dioxide target current was 0.9 A, the output power was 450 W, and the thickness of the titanium dioxide thin film was 8 nm. (3) Preparation of nitrogen-doped graphite carbon thin film: Nitrogen gas was introduced, the argon gas and nitrogen gas air flow ratio was adjusted to 3:1, the chamber air pressure was kept at 1.1 Pa, and the graphite target was sputtered by intermediate frequency magnetron sputtering technology to deposit nitrogen-doped graphite carbon thin film: the intermediate frequency power supply duty ratio was 0.1, the graphite target current was 1A, the output power was 600W, and the thickness of the nitrogen-doped graphite carbon thin film was 9nm. (4) When assembled into a sodium-ion half cell, the initial discharge specific capacities reached 113.1mAh / g, 107.5mAh / g, 103.1mAh / g, and 101.5mAh / g or more at current densities of 0.1C, 0.5C, 1C, and 2C in an electrolyte (1.0M NaClO4 in PC:FEC=95:5 vol%), respectively, demonstrating good rate characteristics. After 100 cycles at a current density of 0.1C, the specific capacity reached 105.2mAh / g or more, demonstrating excellent cycle stability.

[0014] Comparative Example: A NaxMnO2 (x≦1) cathode raw material without surface coating was prepared as a sodium ion half cell. In the electrolyte (1.0M NaClO4 in PC:FEC=95:5 Vol%), the initial discharge specific capacity can reach 70.1mAh / g, 62.3mAh / g, 57.3mAh / g and 50.5mAh / g at current densities of 0.1C, 0.5C, 1C and 2C, respectively. After 100 cycles at a current density of 0.1C, the specific capacity was 43.1mAh / g.

Claims

1. A method for producing a manganese-based sodium ion battery positive electrode material that suppresses the Jahn-Teller effect, comprising: first, depositing a titanium dioxide thin film on a surface of the manganese-based sodium ion battery positive electrode material using a high-power magnetron sputtering technique that utilizes a high-power power source; and then depositing a nitrogen-doped graphitic carbon thin film using an intermediate frequency magnetron sputtering technique that utilizes an intermediate frequency power source.

2. (1) drying the NaxMnO2 electrode powder, placing it on a rotating tool rack in a vacuum coating chamber of a magnetron sputtering device, adjusting the target interval, and evacuating to 10-4 PA; (2) introducing argon gas, adjusting the chamber working air pressure to 1.1 Pa, and employing the high-power magnetron sputtering technology to sputter the titanium dioxide target to deposit a titanium dioxide thin film; and (3) introducing nitrogen gas, adjusting the flow rate ratio of argon gas to nitrogen gas to be 5:1 to 2:1, and maintaining the chamber working pressure at 1.1 Pa; and depositing the nitrogen-doped graphitic carbon thin film by using the intermediate frequency magnetron sputtering technology.

3. 3. The method for producing a manganese-based sodium ion battery positive electrode material for suppressing the Jahn-Teller effect according to claim 2, wherein in step (1), the NaxMnO2 is a tunnel oxide when x<0.5, and is a layered P2 structure oxide when x>0.

5.

4. 3. The method for producing a manganese-based sodium ion battery positive electrode material suppressing the Jahn-Teller effect according to claim 2, characterized in that in step (1), the drying is performed in an oven at 110° C. under vacuum for 120 minutes.

5. The method for producing a manganese-based sodium ion battery positive electrode material suppressing the Jahn-Teller effect according to claim 3, characterized in that in step (2), the duty ratio of the high-output power supply is 0.1, the current of the titanium dioxide target is 0.8-1 A, and the output power is 400-500 W.

6. 3. The method for producing a manganese-based sodium ion battery positive electrode material for suppressing the Jahn-Teller effect according to claim 2, wherein in step (2), the thickness of the titanium dioxide thin film is 8 nm.

7. The method for producing a manganese-based sodium ion battery positive electrode material for suppressing the Jahn-Teller effect according to claim 2, characterized in that in step (3), the flow ratio of the argon gas to the nitrogen gas is 5:1 to 2:

1.

8. 3. The method for producing a manganese-based sodium ion battery positive electrode material for suppressing the Jahn-Teller effect according to claim 2, wherein in step (3), the duty ratio of the intermediate frequency power supply is 0.6, the current of the graphite target is 1 A, and the output power is 600 W.

9. 3. The method for producing a manganese-based sodium ion battery positive electrode material for suppressing the Jahn-Teller effect according to claim 2, wherein the nitrogen-doped graphitic carbon thin film obtained in step (3) has a thickness of 9 nm.

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