A precursor of a sodium-ion battery positive electrode material, a preparation method and application thereof

Abstract

The application discloses a kind of precursor of sodium ion battery positive electrode material and its preparation method and application, belong to sodium ion battery technical field, the application first uses AB2O4 (A=Ni, Mg, Cu, B=Fe, Mn) This spinel material as the precursor of sodium ion battery layered positive electrode, and using the precursor has prepared layered positive electrode material.The precursor is prepared by high-temperature solid-phase method and molten salt method, the precursor obtained has the morphology of spheroid or octahedron;The precursor is mixed with sodium source, and the positive electrode material is obtained by high-temperature sintering in air or oxygen atmosphere, the morphology of precursor is retained, and the compaction density, cycle performance and rate performance of positive electrode material are significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, specifically relating to a precursor of a sodium-ion battery cathode material, its preparation method, and its application. Background Technology

[0002] To alleviate over-reliance on scarce lithium resources and ensure energy security, sodium-ion batteries are becoming an excellent alternative to lithium-ion batteries in low-speed vehicles and energy storage. The main advantages of sodium-ion batteries are the abundant availability of sodium in the Earth's crust, better low-temperature performance, and improved safety. However, the poor cycle performance, low compaction density, and insufficient rate capability of sodium-ion battery cathodes limit their application in fast charging.

[0003] Currently, the performance control methods for sodium-ion battery cathode materials can be broadly categorized into composition design, surface coating, and precursor design.

[0004] 1. Ingredient Design

[0005] By adjusting the composition, elemental doping, and high-entropy effect of the cathode material, lattice distortion can be suppressed and reversible phase transitions induced, thereby improving the structural stability and electrochemical performance of the material. The disadvantages of this method include the need for precise preparation processes and atmosphere control, the frequent inclusion of expensive and rare metal dopants, and the potential for impurity phases to cause performance variations between batches.

[0006] 2. Surface coating

[0007] By uniformly distributing a coating on the cathode surface, the main improvement is in the cathode material's cycle performance and air stability. However, this method typically requires harsh physical or chemical conditions and cannot optimize intrinsic material performance degradation, such as ion migration and irreversible phase transitions. Furthermore, surface coatings are generally detrimental to the material's rate performance, reducing its fast-charging capabilities.

[0008] 3. Precursor design

[0009] By optimizing the types of precursors and the preparation process, uniform distribution and morphology control of cathode material elements can be achieved. An ideal cathode precursor needs to meet the following conditions: uniform distribution of each transition metal element; easy storage and transportation, and not easily deteriorated; and the method should be able to achieve large-scale preparation.

[0010] Currently, common precursors are mixed oxides or co-precipitates, such as metal oxides, metal hydroxides, and metal oxalates. These precursors achieve uniform elemental distribution through physical methods like crushing and ball milling, or chemical methods like co-precipitation. However, most of these precursors have loose structures, resulting in polycrystalline cathode materials with numerous pores, low compaction density, and insufficient volumetric energy density. Furthermore, polycrystalline cathodes exhibit severe side reactions with the electrolyte, leading to rapid capacity decay during cycling and poor rate performance. Summary of the Invention

[0011] This invention provides a precursor for a sodium-ion battery cathode material, its preparation method, and its application. The provided precursor can improve the compaction density of the material, and by controlling the morphology of the cathode material, the cycle performance and rate performance can be optimized.

[0012] To achieve the above objectives, the present invention adopts the following technical solution:

[0013] A precursor for a sodium-ion battery cathode material, wherein the precursor adopts a spinel-type structure with Fd-3m space group, has a dense spherical or octahedral single crystal structure, and its chemical formula is AB2O4, wherein A is one or more of Ni, Mg, and Cu, and B is one or two of Fe and Mn; wherein A is +2 valence and B is +3 valence; the precursor is preferably NiFeMnO4.

[0014] The precursor of the above-mentioned sodium-ion battery cathode material includes the following steps: mixing a variety of transition metal oxides in a certain proportion, wherein the molar ratio of type A elements to type B elements is 1:2, and grinding them thoroughly; placing the pulverized oxides in an air atmosphere, heating them to 1100~1200℃, keeping them at that temperature for 3~12h, and then naturally cooling them to room temperature, followed by pulverization to obtain a spinel-type precursor.

[0015] Preferably, the spinel-type precursor can be subjected to molten salt treatment to give the precursor a uniform octahedral morphology and reduce particle agglomeration. Specifically, the process includes the following steps: thoroughly grinding and pulverizing the spinel-type precursor prepared above; adding a certain proportion of NaCl as a flux salt, with a NaCl to spinel molar ratio greater than 1:6 and less than 1:3; placing it in an air atmosphere, heating to 801~900℃, holding at that temperature for 6~12h, then naturally cooling to room temperature; pulverizing; and washing with water 2~5 times to obtain the molten salt-treated spinel-type precursor.

[0016] The precursor prepared above can be used to prepare sodium-ion battery cathode materials. The preparation process includes the following steps: Na2O2 and the spinel-type precursor obtained above are mixed in a molar ratio of 1.575:1, placed in a corundum crucible and placed in a muffle furnace in an air atmosphere, heated to 900°C at a heating rate of 5°C / min and held for 12 hours, and then naturally cooled to 200°C to obtain a layered cathode material with an octahedral single crystal morphology.

[0017] Beneficial Effects: This invention provides a precursor for sodium-ion battery cathode materials, its preparation method, and its application. Compared with existing technologies, it has the following advantages: This invention is the first to use AB2O4 (A=Ni, Mg, Cu, B=Fe, Mn), a spinel-type material, as a precursor for layered cathodes in sodium-ion batteries, and uses this precursor to prepare layered cathodes. The spinel-type precursor prepared by this invention has a stable structure and can be stored in air for a long time. By using the precursor of this invention to control the morphology of the cathode material, it can exhibit a spherical or octahedral single crystal morphology different from conventional precursors, thereby optimizing cycle performance and rate performance. When this cathode is assembled with sodium metal into a half-cell, the capacity is 131.8 mAh / g at 1C rate, with a capacity retention of 80.9% after 200 cycles; the capacity is 109.1 mAh / g at 5C rate, with a capacity retention of 73.8% after 300 cycles. Furthermore, the compaction density of the cathode material was significantly improved, ranging from 1.73 to 1.93 g / cm³. 3 The concentration was significantly higher than that of the control sample, which ranged from 1.23 to 1.29 g / cm³. 3 Moreover, the preparation method is simple, requiring only high-temperature solid-state method and molten salt method, making it suitable for large-scale production. Attached Figure Description

[0018] Figure 1 This is an X-ray diffraction (XRD) pattern of the spinel precursor NiFeMnO4 in an embodiment of the present invention;

[0019] Figure 2 The positive electrode material in this embodiment of the invention is NaNi. 1 / 3 Fe 1 / 3 Mn 1 / 3 X-ray diffraction (XRD) pattern of O2;

[0020] Figure 3 In this embodiment of the invention, the spinel precursor NiFeMnO4 (left) and the corresponding cathode material NaNi 1 / 3 Fe 1 / 3Mn 1 / 3 SEM image of O2 (right);

[0021] Figure 4 The graph shows the cycling performance of the synthesized materials in Example 1 and the comparative example at 1C.

[0022] Figure 5 The graph shows the cycling performance of the material synthesized in Example 1 at 5C.

[0023] Figure 6 The graph shows the cycling performance of the synthesized materials in Example 2 and the comparative example at 1C.

[0024] Figure 7 The graph shows the cycling performance of the synthetic materials of Example 3 and the comparative example at 1C.

[0025] Figure 8 Cu in Example 4 1 / 3 Ni 2 / 3 FeMnO4 and NaCu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 X-ray diffraction pattern of O2;

[0026] Figure 9 NaNi, the cathode material in the comparative example 1 / 3 Fe 1 / 3 Mn 1 / 3 SEM image of O2. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments:

[0028] Unless otherwise specified, all reagents and materials used below are commercially available.

[0029] Example 1

[0030] NiO was mixed with Fe2O3 and Mn2O3 in a molar ratio of 2:1:1 and ball-milled at 400 rpm for 3 hours using a planetary ball mill. The powder was then pressed into tablets at 10 MPa using a tablet press, placed in a corundum crucible, and placed in a muffle furnace under an air atmosphere. The temperature was increased to 1100℃ at a heating rate of 5℃ / min and held for 12 hours. After cooling to room temperature, spinel A without molten salt treatment was obtained.

[0031] NaCl and spinel A were hand-milled at a molar ratio of 1:3 for 10 min. The mixed powder was then placed in a corundum crucible and placed in a muffle furnace. The temperature was increased to 825°C at a heating rate of 5°C / min and held for 6 h. After naturally cooling to room temperature, the powder was pulverized and washed three times with water to obtain spinel-type precursor B after molten salt treatment.

[0032] Sodium source Na2O2 was mixed with the above-mentioned precursor B at a molar ratio of 1.575:1, placed in a corundum crucible and put into a muffle furnace in an air atmosphere, heated to 900°C at a heating rate of 5°C / min and held for 12 hours, and then naturally cooled to 200°C to obtain the cathode material prepared from the spinel type precursor.

[0033] Method for preparing positive electrode sheet of sodium-ion battery: The positive electrode material prepared using the spinel type precursor is uniformly mixed with conductive agent acetylene black (Super P) and binder polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1. The mixture is prepared into a slurry with N-methylpyrrolidone (NMP), uniformly coated on aluminum foil, vacuum dried at 110℃ for 12h, cooled and cut into sheets for later use.

[0034] Method for preparing a sodium-ion half-cell: The sodium-ion battery is assembled from the above-mentioned positive electrode, sodium negative electrode, electrolyte and separator paper between the positive and negative electrodes.

[0035] Electrochemical performance test results: Cycling performance at 1C rate is as follows Figure 4 As shown, the initial capacity at 1C is 123.5 mAh / g, and the capacity retention rate after 200 cycles is 80.6%; the cycling performance at 5C is as follows... Figure 5 As shown, the initial capacity of the 5C is 109.1 mAh / g, and the capacity retention rate is 73.8% after 300 cycles.

[0036] Compaction density test method and results: The obtained positive electrode sheet was compacted by roller pressing, and then the thickness of the electrode sheet was measured using a micrometer screw gauge. The thickness of the positive electrode material was obtained by subtracting the thickness of the aluminum foil. The compaction density was calculated using the mass of the active material, the electrode sheet thickness, and the electrode sheet area. Multiple electrodes were measured and calculated, and the compaction density of the positive electrode material was found to be 1.73~1.93 g / cm³. 3 .

[0037] Example 2

[0038] The only difference from Example 1 is that the holding temperature T in the muffle furnace during the preparation of spinel A without molten salt treatment is 1150°C.

[0039] Electrochemical performance test results: Cycling performance at 1C rate is as follows Figure 6 As shown, the initial capacity of 1C is 131.8mAh / g, and the capacity retention rate is 80.9% after 200 cycles.

[0040] Example 3

[0041] The only difference from Example 1 is that the holding temperature T in the muffle furnace during the preparation of spinel A without molten salt treatment is 1150°C, and the sodium source used in the preparation of the cathode material is Na2CO3.

[0042] Electrochemical performance test results: Cycling performance at 1C rate is as follows Figure 7 As shown, the initial capacity of 1C is 126.6mAh / g, and the capacity retention rate is 79.9% after 200 cycles.

[0043] X-ray diffraction (XRD) was used to analyze the precursor NiFeMnO4 synthesized in Example 1 and the cathode NaNi prepared therefrom. 1 / 3 Fe 1 / 3 Mn 1 / 3 The phase composition of O2 was determined by recording diffraction patterns through stepwise 2θ scans from 10° to 80° at room temperature. The X-ray diffraction pattern of the synthesized NiFeMnO4 is shown below. Figure 1 (Left), exhibiting the same characteristic peaks as the corresponding PDF card, indicates that it has a spinel-type structure in the Fd-3m space group. After being exposed to air for 150 days, its phase remained unchanged. Figure 1 (Right) As shown. The cathode material NaNi prepared using this spinel-type precursor. 1 / 3 Fe 1 / 3 Mn 1 / 3 The X-ray diffraction pattern of O2 is as follows: Figure 2 As shown, the results indicate that it is an O3 phase layered cathode material of the R-3m space group, meaning that NaNi was successfully obtained. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 material.

[0044] The precursor NiFeMnO4 and the cathode material NaNi prepared therefrom in Example 1 were observed using scanning electron microscopy (SEM). 1 / 3 Fe 1 / 3 Mn 1 / 3 The microstructure of O2 was captured using an accelerating voltage of 15kV, and the results are as follows. Figure 3 As shown, the positive electrode NaNi prepared using NiFeMnO4 precursor is shown. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 has a similar octahedral morphology to the precursor, with a particle size of 1~4μm, indicating that the cathode retains the characteristic morphology of the precursor, thus forming an octahedral single crystal, which is beneficial to improving the compaction density.

[0045] Example 4

[0046] This example only provides a reference for the expansion of material elements. The difference from Example 1 is that in step 1 of this example, the oxides ball-milled are CuO, NiO, Fe2O3, and Mn2O3 in a molar ratio of 2:4:3:3; the sintering temperature in the muffle furnace is changed to 900℃; and the sodium source used in the preparation of the cathode material is Na2CO3. The synthesized Cu... 1 / 3 Ni 2 / 3 FeMnO4 and NaCu 1 / 9 Ni 2 / 9 Fe 1 / 3 Mn 1 / 3 The X-ray diffraction pattern of O2 is as follows: Figure 8 As shown, all are corresponding pure phases, illustrating the elemental extensibility of this synthesis method.

[0047] Comparative Example

[0048] In this example, the precursor is a ball-milled metal oxide, rather than the spinel-type precursor of the previous example. NiO, Fe2O3, and Mn2O3 were ball-milled and mixed according to the proportions of Example 3, and then directly mixed with the same proportion of Na2CO3 without high-temperature solid-state processing or molten salt treatment. The cathode material was then prepared under the same sintering atmosphere and conditions as in Example 1 to obtain the comparative cathode material, whose composition was also NaNi. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, the positive SEM results of this comparative example are as follows Figure 9 As shown. The electrode preparation, battery assembly, and compaction density testing methods are the same as in Example 1. The initial capacity at 1C rate is 124.4 mAh / g, and the capacity retention rate after 200 cycles is 49.6%. The compaction density is 1.23~1.29 g / cm³. 2 .

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A precursor of a sodium-ion battery cathode material, characterized in that, The precursor adopts a spinel-type structure with space group Fd-3m, possessing a dense, spherical or octahedral single-crystal structure. The precursor has the chemical formula AB₂O₄, where A is one or more of Ni, Mg, and Cu, and B is one or two of Fe and Mn. A is in a +2 valence and B is in a +3 valence. The preparation process of the precursor includes the following steps: mixing multiple transition metal oxides in a certain proportion, wherein the molar ratio of element A to element B is 1:2, and thoroughly grinding and pulverizing them; placing the pulverized oxides in air... A spinel-type precursor is obtained through a high-temperature solid-state reaction in an atmosphere. The spinel-type precursor is then subjected to molten salt treatment. The spinel-type precursor obtained by the high-temperature solid-state reaction is thoroughly ground and pulverized, and a certain proportion of NaCl is added as a flux salt. The molar ratio of NaCl to spinel is greater than 1:6 and less than 1:

3. The precursor is placed in an air atmosphere, heated to 801~900℃, kept at that temperature for 6~12h, and then naturally cooled to room temperature. It is then pulverized and washed with water 2~5 times to obtain the molten salt-treated spinel-type precursor, which is the precursor of the sodium-ion battery cathode material.

2. The precursor of the sodium-ion battery cathode material according to claim 1, characterized in that, The precursor is NiFeMnO4.

3. The precursor of the sodium-ion battery cathode material according to claim 1, characterized in that, The high-temperature solid-phase reaction temperature is 1100~1200℃, and the time is 3~12h.

4. Use of the precursor of the sodium-ion battery cathode material according to any one of claims 1 to 3, characterized in that, The precursor is used to prepare the cathode material for sodium-ion batteries. The preparation process includes the following steps: mixing sodium source and spinel-type precursor in proportion, heating to 900°C in air at a heating rate of 5°C / min and holding for 12 hours, and then naturally cooling to 200°C to obtain the cathode material.

5. Use of a precursor of a sodium-ion battery cathode material according to claim 4, characterized in that, The sodium source and spinel-type precursor are mixed in a molar ratio of 1.575:

1.

6. Use of a precursor of a sodium-ion battery cathode material according to claim 4 or 5, characterized in that, The sodium source is Na2O2 or Na2CO3.

7. The use of the precursor of the sodium-ion battery cathode material according to claim 4, characterized in that, The cathode material has an octahedral single crystal morphology and is an O3 phase layered cathode material of space group R-3m.

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