Preparation and application of high-performance hollow-oxide sodium-ion battery cathode material

Abstract

The application provides preparation and application of a high-performance hollow oxide sodium ion battery positive electrode material, and further provides a sodium-rich hollow oxide material, which is a sodium-rich oxide material with a hollow structure.The material has super-high specific capacity when used as a sodium ion battery positive electrode material, has the advantages of low cost, simple operation, safety and environmental protection, and avoids problems such as difficulty in removing crystal water of traditional Prussian blue materials, low volume energy density, and easy leakage of cyanide when the battery is in thermal runaway.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion batteries, specifically relating to the preparation and application of a high-performance hollow oxide sodium-ion battery cathode material. Background Technology

[0002] With the continuous expansion of the new energy and internet industries, the demand for energy storage devices is increasing daily. Currently, lithium-ion batteries, the most widely used type, are constrained by factors such as lithium ore reserves and cost, leading to an urgent search for alternatives. Among these, sodium-ion batteries have emerged as a viable option due to their advantages, including abundant raw material reserves, low price, and similar manufacturing processes to lithium batteries.

[0003] Among the many components, the cathode material has a significant impact on the battery's capacity and cycle performance. Currently, the mainstream materials under research include transition metal oxides, polyanionic compounds, and Prussian blue analogues. Prussian blue analogues, in particular, have attracted widespread attention due to their low raw material and production costs. However, because of the differences between lithium and sodium in atomic radius and electronegativity, sodium-ion batteries face more complex phase transitions than lithium-ion batteries, placing higher demands on electrode materials, especially cathode materials. Currently, the main problems limiting the commercial application of Prussian blue analogues are as follows:

[0004] On the one hand, Prussian blue materials obtained by the most commonly used simple co-precipitation method always suffer from severe lattice structure defects, mainly manifested as water molecules occupying [Fe(CN)6] vacancies, thus forming interstitial water that is difficult to remove. These water molecules fill the [Fe(CN)6] vacancies and connect with metal ions in the framework structure. This situation not only leads to structural defects that severely affect the physical properties of the material, but also results in a large amount of crystallization water in the interstitial lattice, significantly reducing the electrochemical performance of the material.

[0005] On the other hand, since Prussian blue analogues (PBAs) have a cyano backbone, there is a safety risk of cyanide leakage during electrochemical cycling; at the same time, PBAs have a low volumetric energy density, which limits their application in portable and power batteries.

[0006] To address the aforementioned shortcomings, scientists have proposed several improvement methods. For example, Chinese patent CN117747797A (2024) discloses a method for ultrafast preparation of layered oxide cathode materials for sodium-ion batteries based on Prussian blue analogues. This method utilizes Prussian blue analogues as precursors, calcining them at high temperatures to generate nanoparticle-like oxide cathode materials. This method effectively improves the material's tap density and avoids the risk of cyanide leakage. However, the oxide cathode materials produced by this method have similar structures and properties to ordinary layered oxide cathode materials, and their potential remains to be explored.

[0007] Compared to solid solid structures, hollow nanostructures possess a larger specific surface area and higher loading capacity due to their additional internal space, making them promising candidates for energy-related applications such as lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and hybrid supercapacitors (HSCs). In particular, the abundant electrochemical active sites and large contact area between the electrode and electrolyte in hollow structures provide space for electrochemical and diffusion reactions in the electrode material, while the thin shell permeated by the electrolyte significantly reduces the diffusion paths of ions and electrons. Furthermore, the hollow interior can effectively mitigate structural strain caused by repeated ion insertion / extraction processes and accommodate potential volume changes. These structural advantages of hollow nanostructures will greatly improve the electrochemical performance of electrodes. However, how to prepare them simply and effectively, and understanding the evolution mechanism of their internal structure, remains a challenge. Summary of the Invention

[0008] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, one objective of this invention is to propose a method for preparing and applying a high-performance hollow sodium oxide (PBAs) cathode material for sodium-ion batteries. This method employs air annealing to treat the synthesized PBAs in a single step, using oxygen from the air to replace cyanide ions. Under the influence of oxygen, the PBAs transform from their original cubic structure to a cubic hollow structure, resulting in a significant improvement in the material's specific capacity.

[0009] According to embodiments of the present invention, a method for preparing high-performance oxide cathode materials based on sodium-rich Prussian white materials and its application are disclosed, belonging to the field of sodium-ion battery electrode materials. Specifically, firstly, a solution of M transition metal ion chelate is mixed with a sodium ferrocyanide solution by a co-precipitation method to generate Na x MFe(CN)6 precipitation followed by gradient sintering yields a hollow layered oxide cathode material. When used as a cathode material in sodium-ion batteries, this material exhibits ultra-high specific capacity and boasts advantages such as low cost, simple operation, safety, and environmental friendliness. It avoids the problems of traditional Prussian blue materials, such as difficulty in removing crystal water, low volumetric energy density, and easy cyanide leakage during battery thermal runaway.

[0010] In one aspect, this invention proposes a sodium-rich hollow oxide material. According to embodiments of the invention, the sodium-rich hollow oxide material is a sodium-rich oxide material with a hollow structure. When used as a cathode material for sodium-ion batteries, this material exhibits ultra-high specific capacity and has advantages such as low cost, simple operation, safety, and environmental friendliness, avoiding problems such as the difficulty in removing crystal water, low volumetric energy density, and easy leakage of cyanide during battery thermal runaway associated with traditional Prussian blue materials.

[0011] According to embodiments of the present invention, the above-mentioned sodium-rich hollow oxide material may further include at least one of the following additional technical features:

[0012] According to an embodiment of the present invention, the sodium-rich hollow oxide material is a sodium-rich oxide material with a square hollow structure on the surface of sheet-like stacking.

[0013] According to an embodiment of the present invention, the diameter of the hollow structure is 500 nm to 2 μm.

[0014] According to an embodiment of the present invention, the shell thickness of the hollow structure is 100-300 nm.

[0015] According to an embodiment of the present invention, the sodium-rich hollow oxide material has the general formula Na. m MO n In the formula, M is selected from at least one of Co, Mn, Ni, Fe, and Cu, 1 < m ≤ 2, and 1 < n ≤ 2.

[0016] In another aspect, the present invention also provides a method for preparing sodium-rich hollow oxide materials. According to an embodiment of the present invention, the method includes:

[0017] S1: Dissolve the divalent transition metal M salt, NaCl, and chelating agent in deionized water to obtain solution A; dissolve sodium ferrocyanide in deionized water to obtain solution B;

[0018] S2: Mix solution B with solution A to obtain Na. m MFe(CN)6(NMHCF) precursor materials;

[0019] S3: The Na m The MFe(CN)6 precursor material was annealed in air to obtain sodium-rich hollow oxide material (H-NMFO);

[0020] M is selected from at least one of Co, Mn, Ni, Fe, and Cu, and 1 < m ≤ 2.

[0021] According to embodiments of the present invention, the above method may further include at least one of the following additional technical features:

[0022] According to an embodiment of the present invention, the molar ratio of the transition metal M salt to the chelating agent in solution A is 1:(1-2).

[0023] According to an embodiment of the present invention, the molar ratio of the transition metal M salt to the chelating agent in solution A is 1:1.

[0024] According to an embodiment of the present invention, the amount of NaCl in solution A is 14-32g per 100mL of water.

[0025] According to an embodiment of the present invention, the amount of NaCl in solution A is 14g per 100mL of water.

[0026] According to an embodiment of the present invention, the amount of sodium ferrocyanide in solution B is 1 to 4 times that of the divalent transition metal M salt in solution A.

[0027] According to an embodiment of the present invention, the amount of sodium ferrocyanide in solution B is 1 times that of the divalent transition metal M salt in solution A.

[0028] According to an embodiment of the present invention, the divalent transition metal M salt in solution A is manganese chloride.

[0029] According to an embodiment of the present invention, the chelating agent in solution A is sodium citrate, EDTA, or IDHA.

[0030] According to an embodiment of the present invention, the chelating agent in solution A is IDHA.

[0031] According to an embodiment of the present invention, the mixing process is performed in the following manner:

[0032] Solution B was added dropwise to solution A, and then heated to obtain a solution containing Na. m MFe(CN)6 contains Na m A suspension of MFe(CN)6(NMHCF) precipitate was washed and vacuum dried to obtain Na. m MFe(CN)6 precursor material.

[0033] According to an embodiment of the present invention, the temperature of the heat treatment is 20 to 80°C.

[0034] According to an embodiment of the present invention, the temperature of the heat treatment is 40°C.

[0035] According to an embodiment of the present invention, the heat treatment time is 5 to 12 hours.

[0036] According to an embodiment of the present invention, the heat treatment time is 5 hours.

[0037] According to an embodiment of the present invention, the dripping rate is 1 to 10 mL / min.

[0038] According to an embodiment of the present invention, the dripping rate is 1 mL / min.

[0039] According to an embodiment of the present invention, the temperature of the vacuum drying process is 20–150°C.

[0040] According to an embodiment of the present invention, the temperature of the vacuum drying process is 120°C.

[0041] According to an embodiment of the present invention, the annealing process is gradient annealing.

[0042] According to an embodiment of the present invention, the annealing process is to first anneal at 200-300°C for 0-6 hours, and then anneal at 550-800°C for 1-12 hours.

[0043] According to an embodiment of the present invention, the annealing process is to first anneal at 250°C for 3 hours, and then anneal at 700°C for 6 hours.

[0044] According to an embodiment of the present invention, the heating and cooling rates in the annealing process are 0-10℃ / min.

[0045] According to an embodiment of the present invention, the heating and cooling rates in the annealing process are 5°C / min.

[0046] In another aspect, the present invention also provides a sodium-rich hollow oxide material. According to an embodiment of the present invention, the sodium-rich hollow oxide material is prepared by the method described above.

[0047] In another aspect, the present invention also provides a battery cathode material. According to an embodiment of the present invention, the battery cathode material comprises the sodium-rich hollow oxide material described above.

[0048] In another aspect, the present invention also provides a battery. According to an embodiment of the invention, the battery comprises the aforementioned battery positive electrode material.

[0049] According to an embodiment of the present invention, the battery is a lithium battery or a sodium-ion battery.

[0050] According to embodiments of the present invention, the H-NMFO material provided by the present invention uses a Prussian blue analogue as a precursor, and produces an oxide with a sodium-rich hollow structure through simple air calcination. The residual skeletal carbon in the precursor NMHCF is beneficial for improving conductivity, and the introduction of the precursor NMHCF effectively calibrates the morphology and size of H-NMFO. Furthermore, the present invention designs a gradient sintering process at two temperatures, separating the structural water removal and subsequent stages, thus controllably synthesizing a cubic hollow oxide with a uniform morphology. The experimental preparation method provided by the present invention has the advantages of simple preparation method, easy operation, low raw material cost, abundant yield, and environmental friendliness. When the H-NMFO hollow material prepared by the present invention is used as a positive electrode material for sodium-ion batteries, it has a maximum specific capacity of 192 mAh / g, which is sufficient to match most negative electrode materials to prepare sodium-ion batteries with high energy density. Attached Figure Description

[0051] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0052] Figure 1 The image shows the SEM image of the H-NMFO-1 material in Example 1. It can be seen that the sample has a distinct square hollow structure with a surface of sheet-like stacking.

[0053] Figure 2 The SEM image of the H-NMFO-2 material in Example 2 shows that the sample after only calcination at 250℃ has a cubic structure with tightly packed spherical particles on the surface.

[0054] Figure 3 The SEM image of H-NMFO-3 material in Example 3 shows that the sample annealed directly at 700℃ has an agglomerated and broken particle structure.

[0055] Figure 4 The image shows the SEM image of the NMHCF material in Comparative Example 1, which has a standard cubic structure.

[0056] Figure 5 The image shows the SEM image of the NMFO material in Comparative Example 2, which consists of sheet-like hexagonal particles.

[0057] Figure 6 The electrochemical cycle diagrams are for Example 1, Comparative Example 1, and Comparative Example 2. Detailed Implementation

[0058] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0059] Example 1

[0060] The preparation of a sodium-rich hollow oxide cathode material (H-NMO) includes the following steps:

[0061] Step 1: Dissolve 1.5 mmol manganese chloride and 1.5 mmol IDHA in 100 mL of deionized water to obtain solution A; dissolve 1.5 mmol sodium ferrocyanide in 100 mL of deionized water to obtain solution B.

[0062] Step 2: Add solution B dropwise to solution A using a peristaltic pump at a rate of 1 mL / min, heat and stir at 80°C for 5 hours to obtain a solution containing Na. m The suspension of MFe(CN)6 (NMHCF) precipitate was washed three times by centrifugation with deionized water and anhydrous ethanol, and then dried under vacuum at 120°C for 18 h to obtain the NMHCF precursor material.

[0063] Step 3: The NMHCF precursor material is heated to 250℃ in air at a rate of 5℃ / min and held for 3 hours. Then, the temperature is increased to 700℃ and held for 6 hours to obtain sodium-rich hollow oxide cathode material (H-NMFO-1).

[0064] Example 2

[0065] The only difference between Example 2 and Example 1 is the annealing method of the NMHCF precursor material. The precursor material is heated to 250°C at 5°C / min in air and held for 3 hours to obtain sodium-rich hollow oxide cathode material (H-NMFO-2).

[0066] Example 3

[0067] The only difference between Example 3 and Example 1 is the annealing method of the NMHCF precursor material. The precursor material is heated to 700°C at 5°C / min in an air atmosphere and held for 6 hours to obtain sodium-rich hollow oxide cathode material (H-NMFO-3).

[0068] Comparative Example 1

[0069] The only difference between the method used in this comparative example for preparing sodium-ion battery cathode materials and Example 1 is that step three is omitted, resulting in the pure-phase manganese-based Prussian white material NMHCF.

[0070] Comparative Example 2

[0071] The method used in this comparative example for preparing sodium-ion battery cathode materials is the traditional method for preparing layered oxide cathode materials for sodium-ion batteries. First, following the NaFe... 0.5 Mn 0.5 Weigh out 5 mmol of sodium acetate, manganese acetate, ferric nitrate solids and 1.2 g of citric acid and dissolve them together in 80 ml of water. Adjust the pH of the solution to 7-8 with concentrated ammonia. Stir and heat at 80 °C for 3 h to evaporate. Transfer the resulting gel to a crucible and heat it to 350 °C at 5 °C / min in air atmosphere. Hold the temperature for 5 h and continue heating to 900 °C for 12 h to obtain the layered oxide cathode material NMFO.

[0072] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0073] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A sodium-rich hollow oxide material, characterized in that, The sodium-rich hollow oxide material is a sodium-rich oxide material with a hollow structure.

2. The sodium-rich hollow oxide material according to claim 1, characterized in that, The sodium-rich hollow oxide material is a sodium-rich oxide material with a square hollow structure whose surface is composed of stacked sheets; Optionally, the diameter of the hollow structure is 500 nm to 2 μm; Optionally, the shell thickness of the hollow structure is 100–300 nm; Optionally, the sodium-rich hollow oxide material has the general formula Na. m MO n In the formula, M is selected from at least one of Co, Mn, Ni, Fe, and Cu, 1 < m ≤ 2, and 1 < n ≤ 2.

3. A method for preparing sodium-rich hollow oxide materials, characterized in that, include: S1: Dissolve the divalent transition metal M salt, NaCl, and chelating agent in deionized water to obtain solution A; Sodium ferrocyanide was dissolved in deionized water to obtain solution B; S2: Mix solution B with solution A to obtain Na. m MFe(CN)6 precursor materials; S3: The Na m MFe(CN)6 precursor material was annealed in air to obtain sodium-rich hollow oxide material. M is selected from at least one of Co, Mn, Ni, Fe, and Cu, and 1 < m ≤ 2.

4. The method according to claim 3, characterized in that, The molar ratio of the transition metal M salt to the chelating agent in solution A is 1:(1-2); Preferably, the molar ratio of the transition metal M salt to the chelating agent in solution A is 1:1; Optionally, the amount of NaCl in solution A is 14-32g per 100mL of water; Preferably, the amount of NaCl in solution A is 14g per 100mL of water; Optionally, the amount of sodium ferrocyanide in solution B is 1 to 4 times that of the divalent transition metal M salt in solution A; preferably, the amount of sodium ferrocyanide in solution B is 1 time that of the divalent transition metal M salt in solution A; optionally, the divalent transition metal M salt in solution A is manganese chloride.

5. The method according to claim 3, characterized in that, The chelating agents in solution A are sodium citrate, EDTA, and IDHA. Preferably, the chelating agent in solution A is IDHA.

6. The method according to claim 3, characterized in that, The mixing process is carried out as follows: solution B is added dropwise to solution A, and then heated to obtain a solution containing Na. m MFe(CN)6 contains Na m A suspension of MFe(CN)6(NMHCF) precipitate was washed and vacuum dried to obtain Na. m MFe(CN)6 precursor materials; Optionally, the temperature of the heat treatment is 20–80°C; Preferably, the temperature of the heat treatment is 40°C; Optionally, the heat treatment time is 5 to 12 hours; Preferably, the heat treatment time is 5 hours; Optionally, the dripping rate is 1 to 10 mL / min; Preferably, the dripping rate is 1 mL / min; Optionally, the temperature of the vacuum drying process is 20–150°C; Preferably, the temperature of the vacuum drying process is 120°C.

7. The method according to claim 3, characterized in that, The annealing process is gradient annealing; Optionally, the annealing treatment is to first anneal at 200-300°C for 0-6 hours, and then anneal at 550-800°C for 1-12 hours; preferably, the annealing treatment is to first anneal at 250°C for 3 hours, and then anneal at 700°C for 6 hours. Optionally, the heating and cooling rates during the annealing process are 0-10°C / min; Preferably, the heating and cooling rates during the annealing process are 5°C / min.

8. A sodium-rich hollow oxide material, characterized in that, The sodium-rich hollow oxide material is prepared by the method described in any one of claims 3-7.

9. A battery positive electrode material, characterized in that, The positive electrode material of the battery includes the sodium-rich hollow oxide material as described in any one of claims 1, 2 or 8.

10. A battery, characterized in that, The battery includes the positive electrode material as described in claim 9.

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