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

Abstract

The present application provides a modified sodium-ion cathode material, a preparation method thereof and an application. The preparation method includes the following steps: (1) mixing an oxide and a sodium source, adding a pore-forming agent solution, and pressing to obtain a bulk precursor; (2) performing a sintering treatment on the bulk precursor to obtain a porous network structure intermediate; (3) performing a coating and modification treatment on the porous network structure intermediate to obtain the modified sodium-ion cathode material. The present application uses the method of coating and modifying the porous network intermediate of the sodium-ion cathode material, which has beneficial effects on the production capacity of the sodium-ion battery cathode material, the reaction uniformity and sufficiency, the diversity of the coating scheme and the coating uniformity.

Description

Technical Field

[0001] This application belongs to the technical field of sodium-ion batteries, such as a modified sodium-ion cathode material, its preparation method and application. Background Art

[0002] With the advent of the bottleneck period in the development of lithium-ion battery technology and the constraint problem of lithium resources, the cost of lithium secondary batteries is very high, which limits their application in the field of large-scale power storage. Sodium-ion batteries are secondary batteries that mainly rely on the movement of sodium ions between the positive and negative electrodes to work, similar to the working principle of lithium-ion batteries. Sodium elements are abundant and widely distributed on the earth, which can meet the challenges of resource supply, and its cost-effective advantages are very prominent. Among them, sodium-ion layered cathode materials not only have cost advantages, but also excellent energy density, thermal stability, low-temperature resistance, fast charge and discharge, etc., and are favored by the market.

[0003] The raw materials used for sodium-ion cathode materials have a low apparent density, resulting in problems such as a high stacking thickness of raw materials, a low loading amount in the crucible, and insufficient reaction during sintering, which is not conducive to commercial application.

[0004] CN115132987A discloses a preparation method of a multi-layer coated sodium-ion battery cathode material, including the following steps: S1. Mix transition metal oxide particles and polyanion compound particles evenly in a first dispersion medium to obtain a first slurry; spray-dry the first slurry to obtain first particles; S2. Mix the first particles and organic carbon source evenly in a second dispersion medium to obtain a second slurry; spray-dry the second slurry to obtain second particles; S3. Carbonize the second particles under an inert atmosphere to obtain a multi-layer coated sodium-ion battery cathode material.

[0005] CN113644268A discloses a sodium-ion battery layered cathode material and its preparation: ball-mill and mix a sodium source material and an M source material under the protection of an inert gas to form a powder, and calcine at a high temperature to form a Na x MO2 layered material, then grind it into a composite powder, stir and mix the composite powder with a doped coating salt solution under heating until the solvent completely evaporates to obtain a coated and doped powder, and then calcine the obtained coated and doped powder and cool it to obtain the sodium-ion battery layered cathode material.

[0006] At present, the coating method also has great limitations. Especially, sodium-ion cathode materials are very sensitive to water, and the liquid phase method is often not suitable for the coating experiment of sodium-ion cathode materials. Therefore, it is urgent to study more coating methods. Summary of the Invention

[0007] The following is an overview of the subject matter described in detail in this article. This overview is not intended to limit the scope of protection of the claims.

[0008] The present application provides a modified sodium-ion cathode material, a preparation method thereof, and an application thereof. By using the method of coating and modifying a porous network intermediate of the sodium-ion cathode material, it has beneficial effects on the production capacity of the sodium-ion battery cathode material, the reaction uniformity and sufficiency, the diversity of coating schemes, and the coating uniformity.

[0009] To achieve the purpose of this application, the following technical solutions are adopted in this application:

[0010] In a first aspect, an embodiment of the present application provides a preparation method of a modified sodium-ion cathode material, and the preparation method includes the following steps:

[0011] (1) Mix an oxide and a sodium source, add a pore-forming agent solution, and press into tablets to obtain a block-shaped precursor.

[0012] (2) Perform a sintering treatment on the block-shaped precursor to obtain a porous network structure intermediate.

[0013] (3) Perform a coating and modification treatment on the porous network structure intermediate to obtain the modified sodium-ion cathode material.

[0014] In the preparation method of the embodiment of the present application, in the porous network inside the block of the sodium-ion battery cathode material, the block is a precursor with a die shape prepared by powder pressing; the porous network is formed by the pore-forming agent reacting into gas at high temperature to form a three-dimensional channel inside the material block; finally, a phosphate-modified sodium-ion cathode material is prepared by performing a gas-phase deposition reaction or a liquid-phase reaction in the pores.

[0015] The porous network intermediate of the sodium-ion cathode material prepared in the embodiment of the present application has a porous structure, which is conducive to the discharge of waste and the entry of oxygen during the sintering process. In industrial production, it can be affected to a certain extent by the thickness of the charging bowl, which helps to improve production capacity and reduce costs. At the same time, the smooth flow of gas also helps the sufficiency of the material reaction and improves the crystallinity. In addition, the good voids also help the entry of gas and liquid, so that the gas-phase deposition method and the micro-container liquid-phase reaction method can be combined, and the criss-crossing pores are used as templates to form a network-shaped coating layer; the size of the network-shaped coating layer can be regulated by the porosity of the porous intermediate, and the direct contact size between the electrolyte and the cathode material can be controlled, thereby inhibiting the decomposition of the electrolyte on the surface of the cathode particle material, stabilizing the internal structure of the multi-layer cathode particles, and improving the stability of the material. Therefore, the sacrificial sodium phosphate is selected as the coating material in the embodiment of the present application to make up for the consumption of sodium by the first SEI film and improve the first-cycle capacity of the material.

[0016] In one embodiment, the oxide in step (1) includes any one or at least two combinations of nickel oxide, manganese oxide, iron oxide, or copper oxide.

[0017] In one embodiment, the sodium source includes any one or a combination of at least two of sodium carbonate, sodium hydroxide, sodium oxide, or sodium peroxide.

[0018] In one embodiment, the pore-forming agent in the pore-forming agent solution in step (1) includes starch and / or pulverized coal.

[0019] In one embodiment, the mass of the pore-forming agent is 1-25% of the total mass of the oxide and the sodium source, such as: 1%, 2%, 5%, 10%, 15%, or 25%, etc., and preferably 3-20%.

[0020] In one embodiment, the thickness of the massive precursor is 0.8-1.5 cm, such as: 0.8 cm, 0.9 cm, 1 cm, 1.2 cm, or 1.5 cm, etc.

[0021] In one embodiment, the temperature of the sintering treatment in step (ii) is 850-1000 °C, such as: 850 °C, 900 °C, 920 °C, 950 °C, or 1000 °C, etc., and preferably 900-970 °C.

[0022] In one embodiment, the time of the sintering treatment is 8-24 h, such as: 8 h, 10 h, 12, 15 h, or 24 h, etc., and preferably 13-20 h.

[0023] In one embodiment, the atmosphere of the sintering treatment includes air and / or oxygen, and preferably air.

[0024] In one embodiment, the porosity of the porous network structure intermediate in step (ii) is 10-50%, such as: 10%, 20%, 30%, 40%, or 50%, etc., and preferably 20-40%.

[0025] In one embodiment, the coating and modification treatment in step (iii) includes vapor deposition reaction coating and / or liquid phase reaction coating.

[0026] In one embodiment, the vapor deposition reaction coating includes placing the porous network structure intermediate in a reaction furnace and depositing phosphate in the pores of the porous network intermediate by vapor deposition to obtain a phosphate-modified sodium ion cathode material.

[0027] In one embodiment, the vapor deposition method includes using phosphoric acid as a precursor, nitrogen and / or argon as a carrier gas, and depositing at a deposition temperature of 100-500 °C (such as: 100 °C, 200 °C, 300 °C, 400 °C, or 500 °C, etc.) for 3-12 h (such as: 3 h, 4 h, 6 h, 8 h, or 12 h, etc.).

[0028] In one embodiment, the concentration of the phosphoric acid > 3 mol / L.

[0029] In one embodiment, the deposition rate is controlled by controlling the carrier gas flow rate, and the carrier gas flow rate is 0.5 to 10 m 3 / h, for example: 0.5 m 3 / h, 1 m 3 / h, 2 m 3 / h, 5 m 3 / h or 10 m 3 / h, etc.

[0030] In one embodiment, the liquid-phase reaction coating includes: dipping a porous network intermediate in phosphoric acid to obtain a reaction precursor with phosphoric acid adsorbed in the pores, and sintering the reaction precursor to obtain a phosphate-modified sodium-ion cathode material.

[0031] In one embodiment, the concentration of the phosphoric acid > 5 mol / L.

[0032] In one embodiment, the dipping time is 0.5 to 3 min, for example: 0.5 min, 1 min, 2 min, 2.5 min or 3 min, etc.

[0033] In one embodiment, the sintering temperature is 100 to 500 °C, for example: 100 °C, 200 °C, 300 °C, 400 °C or 500 °C, etc.

[0034] In one embodiment, the sintering time is 3 to 12 h, for example: 3 h, 4 h, 6 h, 8 h or 12 h, etc.

[0035] In one embodiment, the sintering atmosphere includes nitrogen and / or argon.

[0036] In a second aspect, an embodiment of the present application provides a modified sodium-ion cathode material, and the modified sodium-ion cathode material is prepared by the method described in the first aspect.

[0037] In a third aspect, an embodiment of the present application provides a positive electrode sheet, and the positive electrode sheet includes the modified sodium-ion cathode material described in the second aspect.

[0038] In a fourth aspect, an embodiment of the present application provides a sodium-ion battery, and the sodium-ion battery includes the positive electrode sheet described in the third aspect.

[0039] Compared with the related art, the present application has the following beneficial effects:

[0040] (1) The porous network intermediate of the sodium ion positive electrode material prepared in the present application has a porous structure, which is conducive to the discharge of waste and the entry of oxygen during the sintering process. In industrial production, it can be unaffected by the thickness of the pot to a certain extent, which helps to increase production capacity and reduce costs. At the same time, the smooth flow of gas also helps the sufficiency of the material reaction and improves the crystallinity. In addition, good gaps also facilitate the entry of gas and liquid, so that the criss-crossing pores can be used as a template to form a mesh coating layer by combining the vapor deposition method and the micro-container liquid phase reaction method; the size of the mesh coating layer can be regulated by the porosity of the porous intermediate, and the direct contact size between the electrolyte and the positive electrode material can be controlled, thereby inhibiting the decomposition of the electrolyte on the surface of the positive electrode particle material, stabilizing the internal structure of the multi-layer positive electrode particles, and improving the stability of the material. Therefore, the present application selects sacrificial sodium phosphate as the coating material to make up for the consumption of sodium by the first SEI film and improve the first-cycle capacity of the material.

[0041] (2) The sodium ion battery made from the modified sodium ion positive electrode material described in this application has a first-cycle discharge capacity of more than 154.6 mAh / g, and a capacity retention rate of more than 94.3% after 100 cycles at 1C.

[0042] Still other aspects will be apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0043] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only to help understand the present application and should not be regarded as specific limitations of the present application.

[0044] Example 1

[0045] This embodiment provides a modified sodium ion positive electrode material. The preparation method of the modified sodium ion positive electrode material is as follows:

[0046] (1) Nickel oxide, manganese trioxide, ferric oxide, copper oxide, and sodium carbonate were mixed in a molar ratio of Ni, Fe, Mn, Cu, and Na of 0.20:0.10:0.68:0.02:0.9, and recorded as mixture A. Starch was dissolved in deionized water to prepare a 40 wt% starch aqueous solution, recorded as solution B. 20 g of mixture A was placed in a mortar, and 2 g of solution B was added dropwise and ground for 1 h to fully mix A and B, recorded as mixture C. Mixture C was placed in a mold and a porous network intermediate precursor D was prepared using a powder tabletting machine. The thickness of D was about 1 cm.

[0047] (2) The bulk precursor D is placed in a crucible and sintered at 900°C for 10 h in an air atmosphere. The starch in the bulk volatilizes and decomposes to form gas, forming pores in the bulk to obtain an intermediate E with a porous network.

[0048] (3) E was placed in a chemical vapor furnace, phosphoric acid was used as a precursor, nitrogen was used as a carrier gas, the deposition temperature was 150 ° C, the deposition time was 2 h, and the phosphate-modified sodium ion positive electrode material F was obtained. F was ground and crushed to obtain a chemical formula of Na 0.9 Ni 0.20 Fe 0.10 Cu 0.02 Mn 0.68 Modified sodium ion cathode material of O2@Na3PO4, where @ means coating.

[0049] Example 2

[0050] This embodiment provides a modified sodium ion positive electrode material. The preparation method of the modified sodium ion positive electrode material is as follows:

[0051] (1) Nickel oxide, manganese trioxide, ferric oxide, copper oxide, and sodium carbonate were mixed in a molar ratio of Ni, Fe, Mn, Cu, and Na of 0.20:0.10:0.68:0.02:0.9, and recorded as mixture A. Starch was dissolved in deionized water to prepare a 40 wt% starch aqueous solution, recorded as solution B. 20 g of mixture A was placed in a mortar, and 2 g of solution B was added dropwise and ground for 1 h to fully mix A and B, recorded as mixture C. Mixture C was placed in a mold and a porous network intermediate precursor D was prepared using a powder tabletting machine. The thickness of D was about 1 cm.

[0052] (2) The block precursor D was placed in a crucible and sintered at 900 ° C for 10 h in an air atmosphere. The starch in the block volatilized and decomposed to form gas, forming pores in the block to obtain a porous network intermediate E. E was immersed in phosphoric acid for 1 min, then taken out and dried in a nitrogen atmosphere at 150 ° C for 2 h to obtain a phosphate-modified sodium ion positive electrode material F. F was ground and pulverized to obtain a chemical formula of Na 0.9 Ni 0.20 Fe 0.10 Cu 0.02 Mn 0.68 Modified sodium ion cathode material of O2@Na3PO4, where @ means coating.

[0053] Example 3

[0054] The only difference between this embodiment and embodiment 1 is that the thickness of the block precursor is 0.5 cm, and other conditions and parameters are exactly the same as those in embodiment 1.

[0055] Example 4

[0056] The only difference between this embodiment and embodiment 1 is that the thickness of the block precursor is 2 cm, and other conditions and parameters are exactly the same as those in embodiment 1.

[0057] Example 5

[0058] The difference between this example and Example 1 is only that the sintering temperature in step (2) is 850 °C, and other conditions and parameters are exactly the same as those in Example 1.

[0059] Example 6

[0060] The difference between this example and Example 1 is only that the sintering temperature in step (2) is 1000 °C, and other conditions and parameters are exactly the same as those in Example 1.

[0061] Comparative Example 1

[0062] The difference between this comparative example and Example 1 is only that no coating modification treatment is carried out, and other conditions and parameters are exactly the same as those in Example 1.

[0063] Comparative Example 2

[0064] The difference between this comparative example and Example 1 is only that no pore-forming agent is added and no tablet pressing treatment is carried out, and other conditions and parameters are exactly the same as those in Example 1.

[0065] Performance Test:

[0066] The positive electrode materials obtained in Examples 1-6 and Comparative Examples 1-2 are mixed with a binder and conductive carbon black in a ratio of 90:5:5, NMP solvent is added and stirred, coated on a current collector and dried and roll-pressed to obtain a positive electrode sheet. The positive electrode sheet and a sodium sheet negative electrode sheet are made into a sodium-ion battery, and performance tests are carried out at 1.5-2.4 V. The test results are shown in Table 1:

[0067] Table 1

[0068] Initial cycle discharge capacity / mAh / g Capacity retention rate after 100 cycles at 1C / % Example 1 155.1 94.3 Example 2 154.6 94.7 Example 3 155.2 94.3 Example 4 154.4 93.5 Example 5 151.1 92.9 Example 6 152.9 93.8 Comparative Example 1 150.3 92.3 Comparative Example 2 147.8 88.6

[0069] As can be seen from Table 1, from Examples 1-2, it can be obtained that the first-cycle discharge capacity of the sodium-ion battery prepared from the modified sodium-ion positive electrode material of the present application can reach more than 154.6 mAh / g, and the capacity retention rate after 100 cycles at 1C can reach more than 94.3%. The method of coating and modifying the porous network intermediate of the sodium-ion positive electrode material of the present application is feasible, and both vapor deposition and liquid-phase micro-reaction can achieve the effect. At the same time, the selection of sodium phosphate coating has the effect of improving the first-cycle capacity.

[0070] By comparing Example 1 with Examples 3-4, it can be seen that during the preparation of the modified sodium ion positive electrode material described in the present application, the thickness of the block precursor will affect its performance. By controlling the thickness of the block precursor to 0.8 to 1.5 cm, the performance of the modified sodium ion positive electrode material is better. If the block precursor is too thick, the good gas flowability during the sintering process may gradually decrease, affecting the material performance; if it is too thin, although it has little effect on the performance, the tableting process is more difficult, and it is also not conducive to increasing the output.

[0071] By comparing Example 1 with Examples 5-6, it can be seen that in the preparation process of the modified sodium ion positive electrode material described in the present application, the temperature of the sintering treatment in step (2) affects its performance. The sintering treatment temperature is controlled at 900-970°C, and the performance of the modified sodium ion positive electrode material is better. If the sintering treatment temperature is too high, it will cause energy waste and increase costs, and the single crystal particles will be too large, which is not conducive to capacity utilization. If the treatment temperature is too low, it will lead to insufficient sintering, low crystallinity, and reduced performance.

[0072] By comparing Example 1 and Comparative Example 1, it can be seen that the present application uses sacrificial sodium salt sodium phosphate as the coating material to compensate for the consumption of sodium by the initial SEI film, thereby increasing the first-cycle capacity of the material. At the same time, it also consumes the residual alkali on the surface of the positive electrode material, reduces polarization, and improves the cycle performance of the material.

[0073] By comparison of Example 1 and Comparative Example 2, it can be seen that the porous network intermediate of the sodium ion positive electrode material prepared in the present application has a porous structure, which is conducive to the discharge of waste and the entry of oxygen during the sintering process. In industrial production, it can be unaffected by the thickness of the pot to a certain extent, which helps to increase production capacity and reduce costs. At the same time, the smooth flow of gas also helps to fully react with the material and improve the crystallinity.

Claims

1. A preparation method of a modified sodium ion cathode material, the preparation method comprising the following steps: (1) Mix an oxide and a sodium source, add a pore-forming agent solution, and press to obtain a blocky precursor; (2) Perform a sintering treatment on the blocky precursor to obtain a porous network structure intermediate; (3) Perform a coating modification treatment on the porous network structure intermediate to obtain the modified sodium ion cathode material; The mass of the pore-forming agent is 1-25% of the total mass of the oxide and the sodium source.

2. The preparation method according to claim 1, wherein, The oxide in step (1) includes any one or a combination of at least two of nickel oxide, manganese oxide, iron oxide, or copper oxide.

3. The preparation method according to claim 1, wherein, The sodium source includes any one or a combination of at least two of sodium carbonate, sodium hydroxide, sodium oxide, or sodium peroxide.

4. The preparation method according to claim 1, wherein, The pore-forming agent in the pore-forming agent solution in step (1) includes starch and / or pulverized coal.

5. The preparation method according to claim 1, wherein, The mass of the pore-forming agent is 3-20%.

6. The preparation method according to claim 1, wherein, The thickness of the blocky precursor is 0.8-1.5 cm.

7. The preparation method according to claim 1, wherein, The temperature of the sintering treatment in step (2) is 850-1000 °C.

8. The preparation method according to claim 1, wherein, The temperature of the sintering treatment in step (2) is 900-970 °C.

9. The preparation method according to claim 1, wherein, The time of the sintering treatment is 8-24 h.

10. The preparation method according to claim 9, wherein, The time of the sintering treatment is 13-20 h.

11. The preparation method according to claim 1, wherein, The atmosphere of the sintering treatment includes air and / or oxygen.

12. The preparation method according to claim 11, wherein, The atmosphere of the sintering treatment is air.

13. The preparation method according to claim 1, wherein, The porosity of the porous network structure intermediate in step (2) is 10-50%.

14. The preparation method according to claim 13, wherein, The porosity of the porous network structure intermediate in step (2) is 20-40%.

15. The preparation method according to claim 1, wherein, The coating modification treatment in step (3) includes vapor deposition reaction coating and / or liquid phase reaction coating.

16. The preparation method according to claim 15, wherein, The vapor deposition reaction coating includes placing the porous network structure intermediate in a reaction furnace and depositing phosphate in the pores of the porous network intermediate by vapor deposition to obtain a phosphate-modified sodium ion cathode material.

17. The preparation method according to claim 16, wherein, The vapor deposition method includes using phosphoric acid as a precursor, nitrogen and / or argon as a carrier gas, and depositing for 3-12 h at a deposition temperature of 100-500 °C.

18. The preparation method according to claim 17, wherein, The concentration of the phosphoric acid > 3 mol / L.

19. The preparation method according to claim 17, wherein, The deposition rate is controlled by controlling the carrier gas flow rate, and the carrier gas flow rate is 0.5 to 10 m 3 / h.

20. The preparation method according to claim 15, wherein, The liquid phase reaction coating includes: immersing and hanging the porous network intermediate in phosphoric acid to obtain a reaction precursor with phosphoric acid adsorbed in the pores, and sintering the reaction precursor to obtain a phosphate-modified sodium ion cathode material.

21. The preparation method according to claim 20, wherein, The concentration of the phosphoric acid > 5 mol / L.

22. The preparation method according to claim 20, wherein, The time of the immersion and hanging is 0.5-3 min.

23. The preparation method according to claim 20, wherein, The temperature of the sintering is 100-500 °C.

24. The preparation method according to claim 20, wherein, The time of the sintering is 3-12 h.

25. The preparation method according to claim 20, wherein, The atmosphere of the sintering includes nitrogen and / or argon.

26. A modified sodium ion cathode material, the modified sodium ion cathode material being prepared by the method according to any one of claims 1-25.

27. A positive electrode sheet, the positive electrode sheet comprising the modified sodium ion cathode material according to claim 26.

28. A sodium ion battery, the sodium ion battery comprising the positive electrode sheet according to claim 27.