Preparation method of sodium ion positive electrode material and application thereof

Abstract

The application provides a preparation method of a sodium ion positive electrode material, comprising the following steps: uniformly mixing positive electrode material precursors Ni 1 / 3Fe 1 / 3 Mn 1 / 3 (OH)2, a sodium source compound, copper oxide and iron oxide to obtain a mixture; and sintering, crushing and screening the mixture under certain conditions to obtain the sodium ion positive electrode material. The sodium ion positive electrode material prepared by the preparation method has obvious single crystal morphology and high crystallinity, and has high compaction density and cycle performance. The preparation method has a simple process flow and is suitable for large-scale industrial production. The application further provides a sodium ion positive electrode material prepared by the preparation method and a sodium ion battery comprising the sodium ion positive electrode material.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a method for preparing a sodium-ion cathode material, the sodium-ion cathode material, and a sodium-ion battery. Background Technology

[0002] As the highest-performing rechargeable battery currently available, lithium-ion batteries were first commercialized in the 1990s. After years of research, lithium-ion batteries have developed a mature technology. However, due to the limited abundance of lithium in the Earth's crust, lithium-ion batteries cannot support the growing energy storage market. Sodium-ion batteries operate on a similar principle to lithium-ion batteries, and sodium salts are abundant and easy to mine, giving them a greater advantage for large-scale applications in the energy storage field.

[0003] Sodium cathode materials are the source of energy density in sodium-ion batteries. Researchers have found that during the preparation process of sodium cathode materials obtained by sintering precursors, two issues arise: firstly, the sintering temperature needs to be no lower than 1000℃ for a sufficient reaction to obtain the sodium cathode material; secondly, if the sintering temperature is too high, the final sintered sodium cathode material will have a single crystal morphology, mostly a lamellar structure. This leads to energy waste and increased production costs due to the high temperature; furthermore, the resulting lamellar sodium cathode material undergoes structural changes or phase transitions, resulting in a decline in battery cycle performance.

[0004] In existing technologies, some researchers have added CuO as a sintering aid to sodium-ion battery cathode material precursors. Generally, the amount of CuO added exceeds 2% of the molar amount of the precursor to achieve the desired sintering effect and successfully lower the sintering temperature to no higher than 1000℃. However, while this excessive addition of CuO improves the sintering effect, it also leads to the formation of impurity phases, resulting in a decrease in the electrical properties of the obtained sodium-ion battery cathode material. Summary of the Invention

[0005] In view of the above, the present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a method for preparing sodium-ion cathode materials and their applications. The preparation method provided by the present invention can prepare low-sulfur, low-impurity sodium-ion cathode materials, and further meets the requirements for preparing low-impurity ferric hydrogen phosphate and sodium-ion cathode materials, thereby improving the utilization rate of battery materials. At the same time, the preparation method has a simple process flow and is suitable for large-scale industrial production applications.

[0006] Therefore, in a first aspect, embodiments of the present invention provide a method for preparing a sodium-ion cathode material, the method comprising:

[0007] S10. According to a certain proportion, Ni, the precursor of the cathode material, is added...1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2, sodium source compound, copper oxide and iron oxide are uniformly mixed to obtain a mixture;

[0008] S20. The mixture is sintered, pulverized and sieved under certain conditions to obtain the sodium ion cathode material.

[0009] Preferably, the sodium source compound includes at least one of sodium carbonate, sodium hydroxide, sodium phosphate, and sodium chloride.

[0010] Preferably, the molar ratio of copper oxide to the cathode material precursor in the mixture is less than 0.02:1.

[0011] Preferably, the molar ratio of copper oxide to the cathode material precursor in the mixture is less than 0.008:1; and / or, the molar ratio of iron oxide to the cathode material precursor in the mixture is less than 0.008:1; and / or, the molar ratio of the sodium source compound to the cathode material precursor is (0.87-1.04):1.

[0012] Preferably, the particle size D50 of the cathode material precursor is between 3 μm and 7 μm; and / or,

[0013] The mixture is mixed in a high-speed mixer for 30-60 minutes at a speed of 600-900 rpm.

[0014] Preferably, the preparation method further includes:

[0015] S5. A mixed salt solution of Ni, Fe, and Mn, a sodium hydroxide solution, and an ammonia solution are mixed in a certain proportion and subjected to a co-precipitation reaction to obtain a precipitate intermediate. The precipitate intermediate is then washed, dried, and sieved to obtain the sodium ion cathode material precursor Ni. x Fe y Mn z (OH)2.

[0016] Preferably, the molar ratio of Ni, Fe, and Mn in the mixed salt solution is 1:1:1; the total molar concentration of Ni, Fe, and Mn in the mixed salt solution is 1.8 mol / L to 2.5 mol / L; and / or,

[0017] The sodium hydroxide solution has a mass fraction of 20%-40%; and / or,

[0018] The molar concentration of the ammonia solution is between 1.5 mol / L and 8 mol / L; and / or,

[0019] The coprecipitation reaction is carried out under an inert atmosphere; and / or,

[0020] The pH of the coprecipitation reaction mixture is between 9 and 11, and the reaction temperature is between 40°C and 60°C; and / or,

[0021] The stirring speed for the coprecipitation reaction is between 200 r / min and 800 r / min.

[0022] Preferably, the washing, drying, and sieving steps specifically include:

[0023] The precipitate intermediate was washed three times with 0 mol / L-1 mol / L sodium hydroxide solution, then washed with pure water until the conductivity was ≤30 μS / cm; dried to obtain Ni. x Fe y Mn z (OH)2, the dried material is sieved through a 200-350 mesh sieve to obtain the cathode material precursor.

[0024] Secondly, the present invention also provides a sodium ion cathode material, which is prepared according to the preparation method described in the first aspect above.

[0025] Thirdly, embodiments of the present invention also provide a sodium-ion battery, the sodium-ion battery comprising the sodium-ion cathode material provided in the second aspect above.

[0026] The method for preparing sodium-ion cathode material provided in this invention involves adding copper oxide and iron oxide during a single sintering process. The synergistic fluxing effect of copper oxide and iron oxide promotes the formation of single crystals, significantly reducing the molar amount of added CuO. The synergistic effect of copper and iron greatly lowers the sintering temperature. Furthermore, the addition of trivalent iron can replace Ni, reducing the formation of impurity phases caused by trivalent nickel due to charge balance. This results in a single-crystal sodium-ion cathode material with a clearly defined single-crystal morphology, high crystallinity, and high compaction density and cycle performance. In addition, this preparation method is simple, efficient, requires no high-end equipment or expensive reagents, uses inexpensive and readily available raw materials, and does not involve toxic or harmful raw materials, making it suitable for large-scale industrial production. Attached Figure Description

[0027] Figure 1 This is a flowchart of a method for preparing a sodium-ion cathode material according to an embodiment of the present invention;

[0028] Figure 2 This is a SEM image of the sodium-ion cathode material prepared in Example 1 of the present invention;

[0029] Figure 3The image shows the XRD pattern of the sodium-ion cathode material prepared in Example 1 of this invention.

[0030] Figure 4 This is a SEM image of the sodium ion cathode material prepared in Comparative Example 1 of the present invention;

[0031] Figure 5 This is a SEM image of the sodium ion cathode material prepared in Comparative Example 2 of the present invention;

[0032] Figure 6 The image shows the XRD pattern of the sodium ion cathode material prepared in Comparative Example 3 of this invention. Detailed Implementation

[0033] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0034] The following disclosure provides numerous different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. Additionally, examples of various specific processes and materials are provided in this invention; however, those skilled in the art will recognize the applicability of other processes and / or the use of other materials.

[0035] Please refer to Figure 1 The purpose of this invention is to provide a method for preparing sodium ion cathode materials, specifically for preparing single-crystal, impurity-free O3-type cathode materials with the chemical formula Na. a Ni x Fe y Mn z Cu b O2, wherein a: 0.67-1.1, x: 0-0.35, y: 0-0.35, z: 0-0.35, b: 0-0.01, x+y+z+b=1, preferably, a: 0.8-1.03, x: 0.30-0.35, y: 0.32-0.35, z: 0.30-0.35, b: 0-0.008.

[0036] The preparation method includes:

[0037] S10. According to a certain proportion, Ni, the precursor of the cathode material, is added...1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2, sodium source compound, copper oxide and iron oxide are uniformly mixed to obtain a mixture;

[0038] S20. The mixture is sintered, pulverized and sieved under certain conditions to obtain the sodium ion cathode material.

[0039] Among them, the nickel-iron-manganese hydroxide Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2 can be prepared by wet co-precipitation or purchased externally.

[0040] Furthermore, the sodium source compound includes at least one of sodium carbonate, sodium hydroxide, sodium phosphate, and sodium chloride.

[0041] Furthermore, the molar ratio of copper oxide to the cathode material precursor in the mixture is less than 0.02:1.

[0042] Furthermore, the molar ratio of copper oxide to the cathode material precursor in the mixture is less than 0.008:1. The molar ratio of iron oxide to the cathode material precursor in the mixture is less than 0.008:1. The molar ratio of the sodium source compound to the cathode material precursor is (0.87-1.04):1.

[0043] Furthermore, the particle size D50 of the cathode material precursor is between 3 μm and 7 μm. The mixture is mixed in a high-speed mixer for 30 min to 60 min at a mixing speed of 600 rpm to 900 rpm.

[0044] Furthermore, the preparation method also includes a precursor Ni. 1 / 3 Fe 1 / 3 Mn 1 / 3 The preparation of (OH)2 specifically includes:

[0045] S5. A mixed salt solution of Ni, Fe, and Mn, a sodium hydroxide solution, and an ammonia solution are mixed in a certain proportion and subjected to a co-precipitation reaction to obtain a precipitate intermediate. The precipitate intermediate is then washed, dried, and sieved to obtain the sodium ion cathode material precursor Ni. x Fe y Mn z (OH)2.

[0046] Further, the molar ratio of Ni, Fe, and Mn in the mixed salt solution is 1:1:1; the total molar concentration of Ni, Fe, and Mn in the mixed salt solution is 1.8 mol / L to 2.5 mol / L. The mass fraction of the sodium hydroxide solution is 20%-40%. The molar concentration of the ammonia solution is 1.5 mol / L-8 mol / L. The coprecipitation reaction is carried out under an inert atmosphere. The pH of the coprecipitation reaction mixture is 9-11, and the reaction temperature is 40℃-60℃. The stirring speed of the coprecipitation reaction is 200 r / min-800 r / min.

[0047] Furthermore, the washing, drying, and sieving steps specifically include:

[0048] The precipitate intermediate was washed three times with 0 mol / L-1 mol / L sodium hydroxide solution, then washed with pure water until the conductivity was ≤30 μS / cm; dried to obtain Ni. x Fe y Mn z (OH)2, the dried material is sieved through a 200-350 mesh sieve to obtain the cathode material precursor.

[0049] One embodiment of the present invention can be implemented by the following steps.

[0050] Ni, Fe, and Mn salt solutions were prepared according to a Ni:Fe:Mn molar ratio of 1:1:1, wherein the total molar concentration of Ni, Fe, and Mn was 1.8–2.5 mol / L.

[0051] Prepare a sodium hydroxide solution with a mass fraction of 20-40%, and an ammonia solution with a concentration of 1.5-8 mol / L;

[0052] Salt solution, sodium hydroxide solution, and ammonia solution are added to the reaction apparatus in parallel streams. An inert gas is introduced, pH 1: 9-11, temperature 40-60℃, and rotation speed 200-800 r / min to carry out the first coprecipitation reaction; the reaction is stopped when D50 reaches 3-7 μm.

[0053] Wash three times with 0-1 mol / L sodium hydroxide solution, then wash with pure water until the conductivity is ≤30 μS / cm; dry to obtain Ni. 1 / 3Fe 1 / 3 Mn 1 / 3 (OH)2, the dried material is sieved through a 200-350 mesh sieve. The sieved material is the nickel-iron-manganese hydroxide precursor. The obtained precursor is a spherical or near-spherical precursor.

[0054] The precursor, sodium source, copper oxide and iron oxide are weighed in a certain proportion and then added to a high-speed mixer. The mixture is then mixed at a certain speed and for a certain time. After the materials are evenly mixed, the materials are taken out.

[0055] Sintering: The resulting uniformly mixed material is sintered in a box furnace under certain temperature conditions. During the sintering process, the temperature and atmosphere uniformity are controlled.

[0056] Crushing: The material obtained from sintering is crushed by a roller mill to obtain powder.

[0057] Sieving: The crushed material is sieved to obtain monocrystalline sodium ion layered cathode material.

[0058] Secondly, the present invention also provides a sodium ion cathode material, which is prepared according to the preparation method described in the first aspect above.

[0059] Thirdly, embodiments of the present invention also provide a sodium-ion battery, the sodium-ion battery comprising the sodium-ion cathode material provided in the second aspect above.

[0060] This scheme achieves the formation of single crystals at a temperature not exceeding 1000℃ by adding copper oxide and iron oxide in a single sintering process. The synergistic fluxing effect of copper oxide and iron oxide promotes the formation of single crystals and obtains pure-phase O3-type sodium ion cathode material. Due to the significant reduction in the amount of copper added, and the fact that the addition of trivalent iron can replace Ni, the formation of trivalent nickel due to charge balance is reduced.

[0061] In this scheme, copper oxide can be used as a flux and a dopant, thereby improving the air stability and electrochemical performance of sodium-ion cathode materials; at the same time, iron oxide serves as both a flux and a dopant, and as an electrochemically active element, it also improves electrochemical performance.

[0062] The following detailed description, with reference to specific embodiments, further illustrates the specific process and effects of the preparation method of the sodium-ion cathode material of the present invention, but does not limit the scope of protection of the present invention. The cathode material precursor or commercially available precursor Ni is prepared by the aforementioned method. 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2 is further applied in different embodiments.

[0063] Example 1

[0064] A method for preparing a sodium-ion cathode material includes the following steps:

[0065] 1. Mix and sinter iron oxide, copper oxide, precursor and sodium source. Add sodium source to precursor in a 1:1 molar ratio. The amount of iron oxide added is 0.05% of the molar amount of precursor, and the amount of copper oxide added is 0.05% of the molar amount of precursor. Then mix in a high-speed mixer at 750 rpm for 60 min.

[0066] 2. The mixture obtained in step 1 is loaded into a cordierite-mullite sagger and placed in a box furnace. The temperature is increased to 500℃ at 3℃ / min and held for 2 hours. Then the temperature is increased to 800℃ at 3℃ / min and held for 4 hours. Finally, the temperature is increased to 970℃ at 3℃ / min and held for 12 hours. The sintering atmosphere is air. After cooling and removing from the furnace, the mixture is crushed by a roller mill to obtain powder material.

[0067] Figure 2 This is a SEM image of the sodium ion cathode material prepared in Example 1. The SEM image shows that the sodium ion cathode material particles are single crystal particles with high crystallinity.

[0068] The prepared sodium-ion cathode material was analyzed using XRD, and the results are as follows: Figure 3 As shown, the synthesized sodium ion cathode material has a single phase, high purity, and no impurity peaks.

[0069] Example 2

[0070] The amount of iron oxide added was 0.08% of the molar amount of the precursor, and the amount of copper oxide added was 0.05% of the molar amount of the precursor. Other conditions were the same as in Example 1.

[0071] Example 3

[0072] The amount of iron oxide added was 0.08% of the molar amount of the precursor, the amount of copper oxide added was 0.08% of the molar amount of the precursor, and other conditions were the same as in Example 1.

[0073] Comparative Example 1

[0074] No iron oxide or copper oxide was added, and all other conditions were the same as in Example 1.

[0075] Figure 4 The image shows a SEM image of the sodium ion cathode material prepared in Comparative Example 1. The SEM image shows that the sodium ion cathode material particles are polycrystalline and have poor morphology.

[0076] Comparative Example 2

[0077] No iron oxide was added, and the amount of copper oxide added was 0.05% of the molar amount of the precursor. Other conditions were the same as in Example 1.

[0078] Figure 5The image shows the SEM image of the sodium ion cathode material prepared in Comparative Example 2. The SEM image shows that the sodium ion cathode material particles are a large number of aggregated single crystal particles, and the material morphology is poor.

[0079] Comparative Example 3

[0080] No iron oxide was added, and the amount of copper oxide added was 5.6% of the molar amount of the precursor. Other conditions were the same as in Example 1.

[0081] The prepared sodium-ion cathode material was analyzed using XRD, and the results are as follows: Figure 6 As shown, comparative analysis with the standard card revealed that the prepared sodium ion cathode material has a single crystal morphology, but its XRD results showed the presence of NiO impurity phase.

[0082] Relevant tests and analyses were conducted on the examples and comparative examples. Specifically, SEM was performed on the sodium-ion layered cathode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2, and the test results are as follows: Figure 2 , Figure 4 and Figure 5 As shown, in Comparative Examples 1-2, the cathode material consisted of polycrystalline particles or a large number of aggregated single-crystal particles. In contrast, the sodium-ion layered cathode material in Example 1 consisted entirely of single-crystal particles, exhibiting primary particle dispersion, high crystallinity, and a pure phase. This indicates that the addition of iron oxide can facilitate melting and promote the formation of single crystals. Comparative Example 3 showed a single-crystal morphology, but its XRD results revealed the presence of a NiO impurity phase. This suggests that excessive CuO leads to the formation of the NiO impurity phase, while the addition of iron oxide effectively inhibited its formation.

[0083] Furthermore, using sodium sheets as the negative electrode, CR2025 button batteries were prepared from the above samples. The 0.1C discharge capacity was tested within the voltage range of 2.0-4.0V. The specific data are shown in Table 1. It can be seen that the sodium-ion positive electrode materials prepared by the schemes of Examples 1-3 have better capacity than the comparative examples at 4.0V, and their cycle performance is also better.

[0084] Table 1. Residual alkali and electrochemical results

[0085] Serial Number Initial discharge capacity (mAh / g) 1C 50-cycle capacity retention rate (%) Example 1 142.77 94.1 Example 2 141.61 94.7 Example 3 141.35 93.9 Comparative Example 1 139.30 83.3 Comparative Example 2 139.66 85.6 Comparative Example 3 135.25 89.2

[0086] The method for preparing sodium-ion cathode material provided in this invention involves adding copper oxide and iron oxide during a single sintering process. The synergistic fluxing effect of copper oxide and iron oxide promotes the formation of single crystals, significantly reducing the molar amount of added CuO. The synergistic effect of copper and iron greatly lowers the sintering temperature. Furthermore, the addition of trivalent iron can replace Ni, reducing the formation of impurity phases caused by trivalent nickel due to charge balance. This results in a single-crystal sodium-ion cathode material with a clearly defined single-crystal morphology, high crystallinity, and high compaction density and cycle performance. In addition, this preparation method is simple, efficient, requires no high-end equipment or expensive reagents, uses inexpensive and readily available raw materials, and does not involve toxic or harmful raw materials, making it suitable for large-scale industrial production.

[0087] 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.

[0088] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing a sodium-ion cathode material, characterized in that, The preparation method includes: S10. According to a certain proportion, Ni, the precursor of the cathode material, is added... 1 / 3 Fe 1 / 3 Mn 1 / 3 (OH)2, sodium source compound, copper oxide and iron oxide are uniformly mixed to obtain a mixture; the sodium source compound includes sodium chloride, the molar ratio of copper oxide to the positive electrode material precursor in the mixture is less than 0.008:1, and the molar ratio of iron oxide to the positive electrode material precursor in the mixture is less than 0.008:

1. S20. The mixture is sintered, pulverized and sieved under certain conditions to obtain the sodium ion cathode material.

2. The method for preparing the sodium-ion cathode material according to claim 1, characterized in that, And / or, the molar ratio of the sodium source compound to the cathode material precursor is (0.87-1.04):

1.

3. The method for preparing the sodium-ion cathode material according to claim 1, characterized in that, The particle size D50 of the cathode material precursor is 3μm-7μm; and / or the mixing time of the mixture in the high-speed mixer is 30min-60min, and the mixing speed is 600rpm-900rpm.

4. The method for preparing the sodium-ion cathode material according to claim 1, characterized in that, Also includes: S5. A mixed salt solution of Ni, Fe, and Mn, a sodium hydroxide solution, and an ammonia solution are mixed in a certain proportion and subjected to a co-precipitation reaction to obtain a precipitate intermediate. The precipitate intermediate is then washed, dried, and sieved to obtain the sodium ion cathode material precursor Ni. x Fe y Mn z (OH)2.

5. The method for preparing the sodium-ion cathode material according to claim 4, characterized in that, The molar ratio of Ni, Fe, and Mn in the mixed salt solution is 1:1:1; the total molar concentration of Ni, Fe, and Mn in the mixed salt solution is 1.8 mol / L to 2.5 mol / L; and / or, the mass fraction of the sodium hydroxide solution is 20% to 40%; and / or, the molar concentration of the ammonia solution is 1.5 mol / L to 8 mol / L; and / or, the coprecipitation reaction is carried out under an inert atmosphere; and / or, the pH of the coprecipitation reaction mixture is 9 to 11, and the reaction temperature is 40℃ to 60℃; and / or, the stirring speed of the coprecipitation reaction is 200 r / min to 800 r / min.

6. The method for preparing the sodium-ion cathode material according to claim 5, characterized in that, The washing, drying, and sieving steps specifically include: washing the precipitated intermediate three times with 0 mol / L-1 mol / L sodium hydroxide alkali, then washing with pure water until the conductivity is ≤30 μS / cm; drying to obtain Ni. x Fe y Mn z (OH)2, the dried material is sieved through a 200-350 mesh sieve to obtain the cathode material precursor.

7. A sodium-ion cathode material, characterized in that, The sodium ion cathode material is prepared by the method according to any one of claims 1-6.

8. A sodium-ion battery, characterized in that, The sodium-ion battery includes: the sodium-ion cathode material according to claim 7.

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