A modified sodium-ion battery cathode material, its preparation method and application

Abstract

This invention provides a modified sodium-ion battery cathode material, its preparation method, and its application. The preparation method includes the following steps: (1) heating a sodium source, an aluminum source, and a silicon source respectively to obtain a sodium source vapor-phase precursor, an aluminum source vapor-phase precursor, and a silicon source vapor-phase precursor; (2) placing the sodium-ion cathode material in a reactor, and sequentially introducing the sodium source vapor-phase precursor, the aluminum source vapor-phase precursor, and the silicon source vapor-phase precursor, followed by introducing water vapor; (3) repeating step (2) n times to obtain the modified sodium-ion battery cathode material. This invention achieves uniform coating of a specific thickness of the sodium-ion battery cathode material based on atomic layer deposition technology. The coating process is simpler, and the coating effect is better and more uniform. Moreover, the coated sodium aluminum silicate can assist in the intercalation and deintercalation of sodium ions at the interface. After coating, the interface of the cathode material can be optimized, and the cycle stability of the sodium-ion battery can be improved.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion batteries, and relates to a modified sodium-ion battery cathode material, its preparation method, and its application. Background Technology

[0002] Compared to lithium-ion batteries, sodium-ion batteries have significant advantages in terms of resource abundance and cost. Sodium ions, the primary charge carrier in sodium-ion batteries, have a crustal abundance of approximately 2.36%, far exceeding the 0.002% abundance of lithium ions. This means sodium-ion resources are abundant, and their price is stable and low, about 1 / 50th the price of battery-grade lithium carbonate. Furthermore, sodium-ion batteries exhibit relatively stable electrochemical performance and are safer to use, making them a promising alternative to lithium-ion batteries.

[0003] However, sodium-ion batteries have a lower energy density. Because sodium has an atomic mass 3.3 times that of lithium, the energy density of sodium-ion batteries is only about 50% of that of lithium-ion batteries. Currently, the energy density of a single sodium-ion battery cell is only 120 Wh / kg, significantly lower than the 180 Wh / kg of lithium iron phosphate batteries and the 240 Wh / kg of ternary lithium batteries. Furthermore, because the ionic radius of sodium ions is 1.3 times that of lithium ions, extraction / intercalation is more difficult. The current maximum cycle life of sodium-ion batteries is approximately 1500 cycles, significantly lower than that of lithium iron phosphate and ternary lithium batteries. Currently, sodium-ion batteries have not yet reached the same level as lithium-ion batteries in terms of cycle stability and energy density, and further performance improvements are needed through modification methods such as doping and coating.

[0004] The cathode material of sodium-ion batteries is a key factor determining battery performance, and coating modification of the cathode material can effectively improve electrochemical performance. Since sodium-ion battery cathode materials are highly sensitive to moisture, contact with water can easily cause structural damage. Furthermore, considering the poor coating effect of liquid-phase coating methods, atomic layer deposition (ALD) technology can serve as an effective way to solve these problems. ALD involves in-situ coating the material surface layer by layer in a gaseous atmosphere, allowing for controllable coating thickness and high density and uniformity.

[0005] CN115132987A discloses a method for preparing a multilayer coated sodium-ion battery cathode material, comprising the following steps: S1. Mixing transition metal oxide particles and polyanionic compound particles uniformly in a first dispersion medium to obtain a first slurry; spray-drying the first slurry to obtain first particles; S2. Mixing the first particles and organic carbon source uniformly in a second dispersion medium to obtain a second slurry; spray-drying the second slurry to obtain second particles; S3. Carbonizing the second particles under an inert atmosphere to obtain a multilayer coated sodium-ion battery cathode material.

[0006] CN107248574A discloses a method for preparing carbon-coated sodium-ion battery cathode material. The method involves doping the cathode material with rare earth metals. The band gap of the rare earth metal element -O is smaller than that of VO, making it easier for electrons to be excited from the valence band to the conduction band, which is beneficial for promoting electron conduction.

[0007] Ordinary coatings such as oxide nitrides can isolate the battery from external moisture and electrolyte corrosion, but they sacrifice the battery's rate performance due to their poor electrical and sodium conductivity. Summary of the Invention

[0008] The purpose of this invention is to provide a modified sodium-ion battery cathode material, its preparation method, and its application. This invention achieves uniform coating of a specific thickness on the cathode material of sodium-ion batteries based on atomic layer deposition technology. The coating process is simpler, and the coating effect is better and more uniform. Moreover, the coated sodium aluminum silicate can assist in the intercalation and deintercalation of sodium ions at the interface. After coating, the interface of the cathode material can be optimized, and the cycle stability of sodium-ion batteries can be improved.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a modified sodium-ion battery cathode material, the method comprising the following steps:

[0011] (1) The sodium source, aluminum source and silicon source are heated respectively to obtain sodium source gas phase precursor, aluminum source gas phase precursor and silicon source gas phase precursor;

[0012] (2) Place the sodium ion cathode material in the reactor, and sequentially introduce sodium source gas phase precursor, aluminum source gas phase precursor and silicon source gas phase precursor, and then introduce water vapor.

[0013] (3) Repeat step (2) n times to obtain the modified sodium-ion battery cathode material, where n≥2.

[0014] This invention utilizes atomic layer deposition (ALD) technology to uniformly coat the surface of sodium aluminum silicate (PAC) material in a sodium-ion battery. This coating possesses certain electrical and sodium conductivity properties, providing mechanical protection for the CAC material and preventing a series of side reactions caused by contact between the material and moisture in the air and the electrolyte. Compared to traditional oxide coatings, PAC itself has high ionic conductivity and does not hinder sodium ion insertion / extraction, effectively improving the cycle stability of sodium-ion batteries.

[0015] Preferably, the sodium source in step (1) includes sodium tert-butoxide and / or sodium acetoacetate.

[0016] Preferably, the aluminum source includes trimethylaluminum and / or dimethylaluminum isopropoxide.

[0017] Preferably, the silicon source comprises tetraethoxysilane.

[0018] Preferably, the temperature of the reactor in step (2) is 220 to 250°C, for example: 220°C, 225°C, 230°C, 240°C or 250°C.

[0019] Preferably, the time for introducing the sodium source gaseous precursor in step (2) is 1.5 to 2.2 s, for example: 1.5 s, 1.6 s, 1.8 s, 2 s or 2.2 s.

[0020] Preferably, after introducing the sodium source gaseous precursor, nitrogen gas is introduced for purging for 20-40 seconds, for example: 20 seconds, 25 seconds, 30 seconds, 35 seconds, or 40 seconds.

[0021] Preferably, the flow rate of the nitrogen gas is 80-100 mL / min, for example: 80 mL / min, 85 mL / min, 90 mL / min, 95 mL / min or 100 mL / min, etc.

[0022] Preferably, the time for introducing the aluminum source vapor precursor in step (2) is 1.5 to 2.2 s, for example: 1.5 s, 1.6 s, 1.8 s, 2 s or 2.2 s.

[0023] Preferably, after introducing the aluminum source gas phase precursor, nitrogen gas is introduced for purging for 20-40 seconds, for example: 20 seconds, 25 seconds, 30 seconds, 35 seconds, or 40 seconds.

[0024] Preferably, the flow rate of the nitrogen gas is 80-100 mL / min, for example: 80 mL / min, 85 mL / min, 90 mL / min, 95 mL / min or 100 mL / min, etc.

[0025] Preferably, the time for introducing the silicon source vapor precursor in step (2) is 2 to 3 seconds, for example: 2 seconds, 2.2 seconds, 2.5 seconds, 2.8 seconds or 3 seconds.

[0026] Preferably, after introducing the silicon source gas phase precursor, nitrogen gas is introduced for purging for 20-40 seconds, for example: 20 seconds, 25 seconds, 30 seconds, 35 seconds, or 40 seconds.

[0027] Preferably, the flow rate of the nitrogen gas is 80-100 mL / min, for example: 80 mL / min, 85 mL / min, 90 mL / min, 95 mL / min or 100 mL / min, etc.

[0028] Preferably, the time for introducing water vapor in step (2) is 2.5 to 3.5 seconds, for example: 2.5 seconds, 2.8 seconds, 3 seconds, 3.2 seconds or 3.5 seconds.

[0029] Preferably, after introducing water vapor, nitrogen gas is introduced to purge for 20-40 seconds, for example: 20 seconds, 25 seconds, 30 seconds, 35 seconds, or 40 seconds.

[0030] Preferably, the flow rate of the nitrogen gas is 80-100 mL / min, for example: 80 mL / min, 85 mL / min, 90 mL / min, 95 mL / min or 100 mL / min, etc.

[0031] In a second aspect, the present invention provides a modified sodium-ion battery cathode material, which is prepared by the method described in the first aspect.

[0032] Thirdly, the present invention provides a positive electrode sheet comprising the modified sodium-ion battery positive electrode material as described in the second aspect.

[0033] Fourthly, the present invention provides a lithium-ion battery comprising a positive electrode as described in the third aspect.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The atomic layer deposition technology described in this invention has a high degree of automation, a simple process flow, and is green and pollution-free for the coating process of cathode materials. It has a low coating temperature and good coating effect, and overcomes the damage of solvent to sodium-ion battery cathode materials in the traditional liquid phase coating process.

[0036] (2) The present invention uses sodium aluminum silicate as a coating layer. Compared with ordinary oxide coating layers, it can supplement sodium in the positive electrode material of sodium-ion battery. At the same time, sodium aluminum silicate is coated on the surface of the material, and its ionic conductivity is high. It will not affect the insertion and extraction of sodium ions in the material itself, and has the effect of improving the cycle stability of the battery.

[0037] (3) After 100 cycles, the modified sodium-ion battery cathode material of the present invention retains a capacity of more than 83.61%, and the energy density at 5C rate can reach more than 135mAh / g. Detailed Implementation

[0038] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0039] Example 1

[0040] This embodiment provides a modified sodium-ion battery cathode material, and the preparation method of the modified sodium-ion battery cathode material is as follows:

[0041] (1) Sodium tert-butoxide, trimethylaluminum and tetraethoxysilane were heated to obtain sodium tert-butoxide gas phase precursor, trimethylaluminum gas phase precursor and tetraethoxysilane gas phase precursor respectively.

[0042] (2) Place the sodium-ion battery cathode material sample into the sample tray, evacuate the vacuum, heat the ALD reaction chamber to 230°C, first introduce sodium tert-butoxide gaseous precursor into the reaction chamber for 2s, then purge with nitrogen for 30s, then introduce trimethylaluminum for 2s, purge with nitrogen for 30s, then introduce tetraethoxysilane gaseous precursor for 2.5s, purge with nitrogen for 30s, and finally introduce water for 3s and purge with nitrogen for 30s.

[0043] (3) Repeat step (2) four times to obtain the modified sodium-ion battery cathode material.

[0044] Example 2

[0045] This embodiment provides a modified sodium-ion battery cathode material, and the preparation method of the modified sodium-ion battery cathode material is as follows:

[0046] (1) Sodium acetoacetate, dimethyl aluminum isopropoxide and tetraethoxysilane were heated to obtain sodium tert-butoxide gas phase precursor, dimethyl aluminum isopropoxide gas phase precursor and tetraethoxysilane gas phase precursor respectively.

[0047] (2) Place the sodium-ion battery cathode material sample into the sample tray, evacuate the vacuum, heat the ALD reaction chamber to 225°C, first introduce sodium tert-butoxide gaseous precursor into the reaction chamber for 2.2s, then purge with nitrogen for 30s, then introduce dimethyl aluminum isopropoxide for 2.2s, purge with nitrogen for 30s, then introduce tetraethoxysilane gaseous precursor for 2.7s, purge with nitrogen for 30s, and finally introduce water for 3s and purge with nitrogen for 30s.

[0048] (3) Repeat step (2) three times to obtain the modified sodium-ion battery cathode material.

[0049] Example 3

[0050] The only difference between this embodiment and Embodiment 1 is that the sodium source gaseous precursor is introduced for a period of time and the temperature of the ALD reaction chamber is 200°C. All other conditions and parameters are exactly the same as in Embodiment 1.

[0051] Example 4

[0052] The only difference between this embodiment and Embodiment 1 is that the sodium source gaseous precursor is introduced for a period of time and the temperature of the ALD reaction chamber is 300°C. All other conditions and parameters are exactly the same as in Embodiment 1.

[0053] Comparative Example 1

[0054] The only difference between this comparative example and Example 1 is that the sodium-ion battery cathode material is directly mixed, ground, and coated with sodium aluminum silicate in a solid phase. All other conditions and parameters are exactly the same as in Example 1.

[0055] Performance testing:

[0056] The test method for cycle performance is as follows: At a temperature of 25°C, the battery is first charged at a constant current of 0.1C to a voltage of 4.0V, then charged at a constant voltage and discharged at a constant current of 0.1C to a voltage of 2.0V. Next, it is charged at a constant current of 0.5C to a voltage of 4.0V, and then discharged at a constant current of 0.5C to a voltage of 2.0V. This constitutes one charge-discharge cycle. The battery is cycled 100 times using the above method, and the discharge capacity after 100 cycles is measured to obtain the capacity retention rate.

[0057] The rate performance test method is as follows: at a temperature of 25℃, the battery capacity density at a 5C rate is tested, and the average value is taken after 5 cycles. The rate performance of the cathode material is evaluated by the capacity density value that the battery can achieve under high rate conditions. The test results are shown in Table 1.

[0058] Table 1

[0059]

[0060] As can be seen from Table 1, and from Examples 1-2, the modified sodium-ion battery cathode material of the present invention retains a capacity of over 83.61% after 100 cycles, and its energy density at 5C rate can reach over 135mAh / g.

[0061] A comparison of Examples 1 and 3-4 shows that during the preparation of the modified sodium-ion battery cathode material of the present invention, the temperature of the reactor affects the performance of the modified sodium-ion battery cathode material. Controlling the reactor temperature at 220-250°C results in better performance of the modified sodium-ion battery cathode material. If the reactor temperature is too low, the precursor source is prone to condensation, which fails to achieve the deposition purpose. If the reactor temperature is too high, the deposited coating is prone to thermal decomposition.

[0062] As can be seen from the comparison between Example 1 and Comparative Example 1, the present invention achieves uniform coating of a specific thickness of the cathode material of sodium-ion battery based on atomic layer deposition technology. The coating process is simpler, the coating effect is better and more uniform, and the coated sodium aluminum silicate can assist the intercalation and deintercalation of sodium ions at the interface. After coating, the interface of the cathode material can be optimized and the cycle stability of sodium-ion battery can be improved.

[0063] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a modified sodium-ion battery cathode material, characterized in that, The preparation method includes the following steps: (1) The sodium source, aluminum source and silicon source are heated respectively to obtain sodium source gas phase precursor, aluminum source gas phase precursor and silicon source gas phase precursor; (2) Place the sodium ion cathode material in the reactor, and sequentially introduce sodium source gas phase precursor, aluminum source gas phase precursor and silicon source gas phase precursor, and then introduce water vapor; the temperature of the reactor in step (2) is 220~250℃; (3) Repeat step (2) n times to obtain the modified sodium-ion battery cathode material, where n≥2; The modified sodium-ion battery cathode material is uniformly coated with a sodium aluminum silicate coating; the coated sodium aluminum silicate coating assists in the intercalation and deintercalation of sodium ions at the interface; after 100 cycles, the modified sodium-ion battery cathode material retains a capacity of over 83.61%, and its capacity density at 5C rate can reach over 135mAh / g.

2. The preparation method according to claim 1, characterized in that, The sodium source in step (1) includes sodium tert-butoxide and / or sodium acetoacetate.

3. The preparation method according to claim 1, characterized in that, The aluminum source includes trimethylaluminum and / or dimethylaluminum isopropoxide.

4. The preparation method according to claim 1, characterized in that, The silicon source includes tetraethoxysilane.

5. The preparation method according to claim 1, characterized in that, The time for introducing the sodium source gaseous precursor in step (2) is 1.5~2.2s.

6. The preparation method according to claim 5, characterized in that, After introducing the sodium source gaseous precursor, nitrogen gas is introduced for purging for 20-40 seconds.

7. The preparation method according to claim 6, characterized in that, The flow rate of the nitrogen gas is 80~100 mL / min.

8. The preparation method according to claim 1, characterized in that, The time for introducing the aluminum source vapor precursor in step (2) is 1.5~2.2s.

9. The preparation method according to claim 8, characterized in that, After introducing the aluminum source gaseous precursor, nitrogen gas is introduced for purging for 20-40 seconds.

10. The preparation method according to claim 9, characterized in that, The flow rate of the nitrogen gas is 80~100 mL / min.

11. The preparation method according to claim 1, characterized in that, The time for introducing the silicon source vapor precursor in step (2) is 2~3s.

12. The preparation method according to claim 11, characterized in that, After introducing the silicon source vapor precursor, nitrogen gas is introduced for purging for 20-40 seconds.

13. The preparation method according to claim 12, characterized in that, The flow rate of the nitrogen gas is 80~100 mL / min.

14. The preparation method according to claim 1, characterized in that, The time for introducing water vapor in step (2) is 2.5~3.5s.

15. The preparation method according to claim 14, characterized in that, After introducing water vapor, nitrogen gas is introduced for purging for 20-40 seconds.

16. The preparation method according to claim 15, characterized in that, The flow rate of the nitrogen gas is 80~100 mL / min.

17. A modified sodium-ion battery cathode material, characterized in that, The modified sodium-ion battery cathode material is prepared by the method described in any one of claims 1-16.

18. A positive electrode plate, characterized in that, The positive electrode comprises the modified sodium-ion battery positive electrode material as described in claim 17.

19. A sodium-ion battery, characterized in that, The sodium-ion battery includes the positive electrode as described in claim 18.

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