Sodium-ion battery layered transition metal oxide and preparation method and application

Abstract

The application discloses a sodium ion battery layered transition metal oxide and a preparation method and application thereof, and a chemical formula of the sodium ion battery layered transition metal oxide is NaMna-b-c-d-e-fO2 a Ni b Fe c Li d Ti e Cu f O2, wherein a, b, c, d, e and f represent proportions of respective metal elements. The application aims to develop a layered transition metal oxide positive electrode material suitable for long-life sodium ion batteries through a high-entropy doping method, and improve the capacity and cycle stability of the layered oxide. The cycle stability of the material is excellent, and the capacity is in a medium-to-high level. In addition, a high-temperature calcination method for preparing the material is simple in operation, easy to prepare, green and environment-friendly, and can be applied to a large-scale product production process.

Description

Technical Field

[0001] This application relates to a layered transition metal oxide for sodium-ion batteries, its preparation method, and its application, belonging to the field of sodium-ion battery cathode technology. Background Technology

[0002] In the current field of energy storage, sodium-ion batteries have become a research hotspot due to their significant advantages in cost, wide resource distribution, and environmental friendliness. Given the abundant reserves of sodium in the Earth's crust and its relatively low extraction cost, sodium-ion batteries are considered a promising energy storage technology, particularly for large-scale energy storage systems. Furthermore, compared to lithium-ion batteries, sodium-ion batteries exhibit superior environmental compatibility in terms of material recycling and reuse.

[0003] Among various cathode materials for sodium-ion batteries, layered transition metal oxides have attracted much attention due to their unique structural characteristics and superior electrochemical performance. These materials typically exhibit a layered structure, allowing sodium ions to rapidly intercalate and deintercalate within the interlayer channels, thus supporting the battery's charge and discharge processes. This structural feature of layered transition metal oxide cathode materials not only facilitates the rapid migration of sodium ions but also improves the battery's charge-discharge efficiency and cycle stability, providing a significant impetus for the advancement of sodium-ion battery technology.

[0004] Despite the great potential of layered transition metal oxide cathode materials in sodium-ion battery applications, challenges remain, including energy density, cycle stability, cost, and sodium-ion transport efficiency. Therefore, continuous scientific research and technological innovation are crucial for improving the performance of these materials. Summary of the Invention

[0005] The purpose of this invention is to improve the energy storage performance of layered transition metal oxides in sodium-ion batteries, including material capacity and cycle stability. Drawing on the preparation methods of layered oxide cathode materials for lithium-ion batteries, this invention provides a method for preparing ultra-stable layered transition metal oxides for sodium-ion batteries. The prepared sodium-based layered transition metal oxides exhibit excellent cycle stability. Furthermore, this method is simple to operate, easy to prepare, and environmentally friendly, making it suitable for large-scale production processes.

[0006] According to the first aspect of this application, a layered transition metal oxide for sodium-ion batteries is provided, the chemical formula of which is: NaMn a Ni b Fe c Li d Ti e Cu f O2,

[0007] Where a, b, c, d, e, and f represent the proportions of each metallic element;

[0008] 0.4≤a≤0.6, 0.25≤b≤0.45, 0.01≤c≤0.1, 0≤d≤0.1, 0≤e≤0.1, 0≤f≤0.1, and a+b+c+d+e+f=1.

[0009] Optionally, 0.45≤a≤0.55, 0.28≤b≤0.4, 0.03≤c≤0.08, 0≤d≤0.08, 0≤e≤0.08, 0≤f≤0.08, and a+b+c+d+e+f=1.

[0010] Optionally, the particle size of the layered transition metal oxide in the sodium-ion battery is 0.5–3 μm.

[0011] According to a second aspect of this application, a method for preparing the above-described layered transition metal oxide for sodium-ion batteries is provided, the method comprising:

[0012] According to the chemical formula, a mixture containing sodium salt, manganese salt, nickel salt, iron salt, lithium salt, titanium salt, and copper salt is ball-milled and calcined to obtain the layered transition metal oxide of the sodium-ion battery.

[0013] Optionally, the sodium source is selected from at least one of sodium carbonate, sodium hydroxide, and sodium bicarbonate.

[0014] Optionally, the manganese source is selected from at least one of manganese dioxide, manganese tetroxide, and manganese dioxide.

[0015] Optionally, the nickel source is selected from at least one of nickel oxide and nickel hydroxide.

[0016] Optionally, the iron source is selected from at least one of ferric oxide and ferric oxide.

[0017] Optionally, the lithium source is selected from at least one of lithium carbonate and lithium hydroxide.

[0018] Optionally, the titanium source is titanium dioxide.

[0019] Optionally, the copper source is selected from at least one of copper oxide, copper hydroxide, and cuprous oxide.

[0020] Optionally, the calcination temperature is 800–1000°C, and the calcination time is 10–20 h.

[0021] Optionally, the calcination temperature is independently selected from any value of 800℃, 820℃, 850℃, 900℃, 950℃, 980℃, 1000℃ or a range between any two of the above.

[0022] Optionally, the calcination time is independently selected from any value of 10h, 12h, 14h, 15h, 16h, 18h, 20h or a range between any two of the above.

[0023] Optionally, the calcination temperature is 850–980°C, and the calcination time is 12–16 hours.

[0024] Preferably, the layered transition metal oxide achieves optimal performance after calcination at 950°C for 15 hours.

[0025] Optionally, the rotational speed of the ball mill is 400-1000 r, and the milling time is 6-12 h.

[0026] Optionally, the rotational speed of the ball mill is independently selected from any value among 400r, 500r, 600r, 800r, and 1000r, or a range between any two of the above.

[0027] Preferably, the ball mill rotates at a speed of 400-1000 r, with one hour clockwise and one hour counterclockwise.

[0028] According to a third aspect of this application, a layered transition metal oxide cathode material for sodium-ion batteries is provided, the layered transition metal oxide cathode material for sodium-ion batteries comprising an active material, carbon nanotubes, and PVDF;

[0029] The active material is selected from the layered transition metal oxides for sodium-ion batteries described above.

[0030] Optionally, the mass ratio of the active material, carbon nanotubes, and PVDF is 7:2:1 to 9:0.5:0.5.

[0031] Optionally, the mass ratio of the active material, carbon nanotubes, and PVDF is independently selected from any value among 9:0.5:0.5, 8:1:1, 7:2:1, or any range between the two.

[0032] Optionally, the carbon nanotubes are conductive carbon black.

[0033] According to a fourth aspect of this application, an application of the above-described layered transition metal oxide cathode material for sodium-ion batteries is provided.

[0034] As an optional implementation, this application is achieved through the following technical solution:

[0035] A method for preparing layered transition metal oxides includes the following steps:

[0036] The raw materials are prepared according to the formula of the layered transition metal oxide composition. After mixing the various raw materials with a ball mill, they are calcined in a muffle furnace at 800-1000℃ for 10-20 hours. After the furnace temperature drops to 100℃, the sample is taken out immediately and stored in a glove box to obtain the target sample.

[0037] The prepared sample was a powder, and the particle size was approximately 2 μm as determined by scanning electron microscopy.

[0038] Preferably, the product is removed immediately after the furnace temperature drops to 100°C and stored in a glove box to prevent the oxides from absorbing water and affecting performance.

[0039] A method for preparing a layered transition metal oxide slurry for ultra-stable sodium-ion batteries is disclosed. The positive electrode slurry is prepared according to the ratio of active material: carbon nanotubes: PVDF = 8:1:1. It is then vacuum dried at 120℃ for 12 hours.

[0040] This invention draws upon the preparation method of layered transition metal oxide cathode materials in lithium-ion batteries, and designs and prepares layered transition metal oxide cathode materials for sodium-ion batteries according to the high entropy principle, enabling them to exhibit good capacity and excellent cycle stability during sodium storage: (1) It retains the main components and proportions in layered transition metal oxides, and the structure of layered oxides is not changed after the introduction of various other elements; (2) Due to the introduction of more elements into the material, and the different roles of each element, specifically manifested as: Ni 2+ Cu 2+ Fe 3+ It possesses electrochemical activity and can provide capacity to materials; Mn 4+ and Ti 4+ It can stabilize the structure and suppress phase transitions; Cu 2+ and Fe 3+ It helps to increase the average voltage; Li + It can trigger the redox reaction of anions, leading to an increase in the voltage range and capacity of the cathode material.

[0041] The purpose of this invention is to develop a layered transition metal oxide cathode material suitable for long-life sodium-ion batteries through high-entropy doping, thereby improving the capacity and cycle stability of layered oxides. This type of material exhibits excellent cycle stability and a medium-to-high capacity. Furthermore, the high-temperature calcination method used to prepare this material is simple, easy to prepare, and environmentally friendly, making it suitable for large-scale production processes.

[0042] The beneficial effects that this application can produce include:

[0043] The layered transition metal oxide for sodium-ion batteries provided in this application exhibits superior capacity and excellent cycle stability during electrochemical cycling compared to existing sodium-based layered transition metal oxides, thus promoting the application of layered transition metal oxides in sodium-ion batteries. Furthermore, its preparation process is simple and environmentally friendly, making it suitable for large-scale production processes. Attached Figure Description

[0044] Figure 1 The images show the XRD patterns of each sample (NM, NMF, NMFL, NMFLT, and NMFLTC) in Example 1 of this application, where NM represents NaNi. a Mn b O2, NMF: NaNi a Mn b Fe c O2, NMFL: NaNi a Mn b Fe c Li d O2, NMFLT:NaNi a Mn b Fe c Li d Ti e O2, NMFLTC: NaNi a Mn b Fe c Li d Ti e Cu f O2.

[0045] Figure 2 The images are SEM images of the samples (NM, NMF, NMFL, NMFLT and NMFLTC) in Example 1 of this application.

[0046] Figure 3 EDS diagrams of each sample (NM, NMF, NMFL, NMFLT, and NMFLTC) in Example 1 of this application.

[0047] Figure 4 The charge-discharge curves of each sample (NM, NMF, NMFL, and NMFLT) in Example 3 of this application are shown at 0.1C.

[0048] Figure 5 The charge-discharge curves of each sample (NM, NMF, NMFL, and NMFLT) in Example 3 of this application are shown at 0.3C.

[0049] Figure 6This is a comparison of the cycle stability of each sample (NM, NMF, NMFL, NMFLT and NMFLTC) in Example 4 of this application at 0.1C, 0.3C and 1C.

[0050] Figure 7 The data provided are the charge / discharge curves and cycle stability data of the NMFLTC in this application at cutoff voltages of 4.1V and 4.2V. Detailed Implementation

[0051] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0052] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0053] This application uses the Xinwei Battery Testing System to conduct constant current charge-discharge tests (cutoff voltage 2.0-4.0V, current 0.1C, 0.3C and 1C, where 1C = 120mAh g). -1 The morphology of the samples was observed using a ZEISS scanning electron microscope; XRD of the samples was tested using a Bruker D8 microscope (Germany).

[0054] In this application, NM is NaNi a Mn b O2;

[0055] NMF is NaNi a Mn b Fe c O2;

[0056] NMFL is NaNi a Mn b Fe c Li d O2;

[0057] NMFLT is NaNi a Mn b Fe c Li d Ti e O2;

[0058] NMFLTC is NaNi a Mn b Fe c Li d Ti e Cu f O2.

[0059] Example 1

[0060] The preparation of layered transition metal oxides NM, NMF, NMFL, NMFLT and NMFLTC by high temperature calcination includes the following steps: (1) Na2CO3, NiO, Mn3O4, Fe2O3, Li2CO3, TiO2 and CuO are mixed according to the oxide expression, and then the raw materials are mixed using a ball mill.

[0061] Taking the preparation of NMFLTC as an example, the following ingredients were ball-milled at a speed of 800 r for 1.669 g Na2CO3, 0.672 g NiO, 1.144 g Mn3O4, 0.119 g Fe2O3, 0.055 g Li2CO3, 0.119 g TiO2 and 0.119 g CuO, for 1 hour clockwise and 1 hour counterclockwise.

[0062] (2) After the ball milling powder is compressed into tablets (pressure 15MPa), it is transferred to a crucible and calcined at 950℃ in a muffle furnace for 15 hours.

[0063] (3) After the furnace temperature drops to 100°C, the sample is immediately removed and transferred to a glove box. After grinding, it is ready for subsequent use to obtain the layered transition metal oxide for sodium-ion batteries, namely NaMn. a Ni b Fe c Li d Ti e Cu f O2 (a: 0.5, b: 0.3, c: 0.05; d: 0.05; e: 0.05; f: 0.05), with a particle size of 0.5 μm.

[0064] Taking the preparation of NMFLT as an example, the following ingredients were ball-milled at a speed of 800 r for 1.669 g Na2CO3, 0.672 g NiO, 1.144 g Mn3O4, 0.239 g Fe2O3, 0.055 g Li2CO3, 0.119 g TiO2 and 0 g CuO for 1 hour clockwise and 1 hour counterclockwise.

[0065] (2) After the ball milling powder is compressed into tablets (pressure 15MPa), it is transferred to a crucible and calcined at 950℃ in a muffle furnace for 15 hours.

[0066] (3) After the furnace temperature drops to 100°C, the sample is immediately removed and transferred to a glove box. After grinding, it is ready for subsequent use to obtain the layered transition metal oxide for sodium-ion batteries, namely NaMn. a Ni b Fe c Li d Ti e Cu fO2 (a: 0.5, b: 0.3, c: 0.1; d: 0.05; e: 0.05; f: 0), with a particle size of 3 μm.

[0067] Taking the preparation of NMFL as an example, the following ingredients were used: 1.669g Na2CO3, 0.672g NiO, 1.144g Mn3O4, 0.359g Fe2O3, 0.055g Li2CO3, 0g TiO2 and 0g CuO. The ball milling speed was 800r, and the milling was performed clockwise and counterclockwise for 1 hour each.

[0068] (2) After the ball milling powder is compressed into tablets (pressure 15MPa), it is transferred to a crucible and calcined at 950℃ in a muffle furnace for 15 hours.

[0069] (3) After the furnace temperature drops to 100°C, the sample is immediately removed and transferred to a glove box. After grinding, it is ready for subsequent use to obtain the layered transition metal oxide for sodium-ion batteries, namely NaMn. a Ni b Fe c Li d Ti e Cu f O2 (a: 0.5, b: 0.3, c: 0.15; d: 0.05; e: 0; f: 0), with a particle size of 1.5 μm.

[0070] like Figure 1 As shown, from Figure 1 As can be seen, the five samples prepared by this method have the typical structure of layered transition metal oxides, and metal doping does not affect the crystal structure of the material.

[0071] like Figure 2 As shown, from Figure 2 As can be seen, the five samples prepared by this method have similar structural morphologies. Under the same preparation temperature and time, metal doping does not affect the morphology of the material.

[0072] like Figure 3 As shown, from Figure 3 The data shows that the elements are evenly distributed in each sample, indicating that the metal doping has successfully entered the interior of the layered transition metal oxide.

[0073] Example 2

[0074] The specific steps for preparing electrodes for assembling sodium-ion batteries are as follows:

[0075] (1) The sodium-ion battery layered transition metal oxide, i.e. the active material, prepared in Example 1, was weighed according to the mass ratio of 400mg active material: 50mg carbon nanotubes: 50mg PVDF = 8:1:1. The mixture was then ground in a glove box. After 30 minutes, 700μl of NMP solvent was added. After grinding for another 3 hours, the slurry was uniformly coated onto aluminum foil using a 150μm scraper.

[0076] (2) The aluminum foil coated with slurry was transferred to a vacuum drying oven and dried at 120°C for 12 hours to obtain the layered transition metal oxide cathode material for sodium-ion batteries.

[0077] Example 3

[0078] The specific steps for assembling and testing the button battery are as follows:

[0079] Assemble the electrode in the following order: positive electrode shell, positive electrode plate, separator, sodium plate, gasket, spring plate, and negative electrode shell. Add 100 μL of electrolyte (1.0 M NaPF6 EC:DMC solution + 5% FEC). After standing for 12 hours, cycle charge-discharge testing can be performed. Figure 4 , 5 As shown, from Figure 4 , 5 It can be seen that under cycling conditions (0.1C and 0.3C), the incorporation of iron, lithium and copper can provide capacity to the material, while the incorporation of titanium does not contribute much to the capacity, but can effectively suppress phase transition and increase the cycling stability of the material.

[0080] Example 4

[0081] Battery testing was performed using a constant current charge-discharge system. The specific steps are as follows:

[0082] Set the charge / discharge program as follows: rest for 30 seconds, charge at 0.1, 0.3, or 1C, rest for 30 seconds, charge at 0.1, 0.3, or 1C, and return to step one if the cycle is less than 500 times to complete the battery cycle charge / discharge test.

[0083] like Figure 6 As shown, from Figure 6 The results show the cycling stability of each sample at 0.1C, 0.3C, and 1C. NMFLTC exhibits the best cycling stability at all current densities. For example, at 0.3C, NMFLTC retains 71% capacity retention after 600 cycles.

[0084] like Figure 7 As shown, from Figure 7As can be seen, NMFLTC still has a high capacity retention rate under higher cutoff voltage conditions. This is due to the fact that the incorporation of lithium triggers the redox reaction of anions, which increases the voltage range of the material.

[0085] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A layered transition metal oxide for sodium-ion batteries, characterized in that, The chemical formula of the layered transition metal oxide in the sodium-ion battery is: NaMn a Ni b Fe c Li d Ti e Cu f O2, Where a, b, c, d, e, and f represent the proportions of each metallic element; 0.4 ≤ a ≤ 0.6, 0.25 ≤ b ≤ 0.45, 0.01 ≤ c ≤ 0.1, 0 < d ≤ 0.1, 0 < e ≤ 0.1, 0 < f ≤ 0.1, and a + b + c + d + e + f = 1.

2. The layered transition metal oxide for sodium-ion batteries according to claim 1, characterized in that, 0.45 ≤ a ≤ 0.55, 0.28 ≤ b ≤ 0.4, 0.03 ≤ c ≤ 0.08, 0 < d ≤ 0.08, 0 < e ≤ 0.08, 0 < f ≤ 0.08, and a + b + c + d + e + f = 1.

3. The layered transition metal oxide for sodium-ion batteries according to claim 1, characterized in that, The particle size of the layered transition metal oxide in the sodium-ion battery is 0.5 ~ 3 μm.

4. The method for preparing the layered transition metal oxide for sodium-ion batteries according to any one of claims 1 to 3, characterized in that, The preparation method includes: According to the chemical formula, a mixture containing sodium salt, manganese salt, nickel salt, iron salt, lithium salt, titanium salt, and copper salt is ball-milled and calcined to obtain the layered transition metal oxide of the sodium-ion battery.

5. The preparation method according to claim 4, characterized in that, The sodium salt is selected from at least one of sodium carbonate, sodium hydroxide, and sodium bicarbonate; The manganese salt is selected from at least one of manganese dioxide, manganese tetroxide, and manganese dioxide. The nickel salt is selected from at least one of nickel oxide and nickel hydroxide; The iron salt is selected from at least one of ferric oxide and ferric oxide; The lithium salt is selected from at least one of lithium carbonate and lithium hydroxide; The titanium salt is titanium dioxide; The copper salt is selected from at least one of copper oxide, copper hydroxide, and cuprous oxide.

6. The preparation method according to claim 4, characterized in that, The calcination temperature is 800~1000℃, and the calcination time is 10~20h.

7. The preparation method according to claim 4, characterized in that, The ball mill operates at a speed of 400-1000 rpm for 6-12 hours.

8. A layered transition metal oxide cathode material for sodium-ion batteries, characterized in that, The sodium-ion battery layered transition metal oxide cathode material includes active material, carbon nanotubes, and PVDF; The active material is selected from the layered transition metal oxides for sodium-ion batteries according to any one of claims 1 to 3.

9. The layered transition metal oxide cathode material for sodium-ion batteries according to claim 8, characterized in that, The mass ratio of the active material, carbon nanotubes, and PVDF is 7:2:1 to 9:0.5:0.

5. The carbon nanotubes are conductive carbon black.

10. The application of the sodium-ion battery layered transition metal oxide cathode material according to any one of claims 8 to 9 in sodium-ion batteries.

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