A high-valence cation modified polycrystalline o3-type sodium-ion battery layered cathode material and a preparation method thereof

Abstract

The application belongs to the technical field of sodium ion batteries, and relates to a high-valence cation modified polycrystalline O3 type sodium ion battery layered positive electrode material and a preparation method thereof. The battery positive electrode material has a molecular formula of Na(Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ) 1‑x Nb x O2, wherein 0

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, and relates to a high-valent cation-modified polycrystalline O3-type sodium-ion battery layered cathode material and its preparation method. Background Technology

[0002] With the rapid development of the mobile electronic device and electric vehicle industries, the consumption of lithium-ion batteries has increased dramatically, leading to a growing shortage of lithium resources and a rapid rise in lithium prices. The high price of lithium-ion batteries severely hinders their application in large-scale energy storage, where battery cost is a critical factor. In contrast, sodium resources are abundant and have a significant price advantage, effectively addressing the lithium shortage problem. Furthermore, sodium shares similar physical and chemical properties with lithium, allowing for the full utilization of its mature research methods and technologies. Therefore, sodium-ion batteries, with their unique cost advantage, are considered the most promising alternative to lithium-ion batteries in large-scale energy storage systems.

[0003] Layered transition metal oxide (LTMO) cathode materials for sodium-ion batteries are considered among the most promising cathode materials due to their abundant sources, environmental friendliness, simple preparation, and excellent electrochemical performance. Compared to the Na-poor P2 phase, the Na-rich O3 phase layered oxides have a higher sodium content, resulting in a higher specific capacity in the full cell, thus demonstrating their superior commercialization potential. Based on recent research results, O3-type NaNi... 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 (NFM) is considered a promising commercial cathode for SIBs due to its relatively high theoretical capacity and cycle stability, showing great potential for commercial applications. However, in repeated Na... + During the extraction / insertion process, the NFM cathode material undergoes a continuous phase transition from O3hex. to P3hex. to O3′mon. to P3′mon. In Na… + During the extraction process, when the charging cutoff potential exceeds 4.0 V, the capacity decays rapidly and the cycle stability is poor.

[0004] Sodium ion layered oxides mainly have two morphologies: single crystal and polycrystalline. Currently, there are few reports on how to obtain high-performance polycrystalline sodium ion layered cathode materials. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention aims to provide a high-valent cation-modified O3-type sodium-ion battery layered cathode material and its preparation method, through the modification of polycrystalline O3-type NaNi. 1 / 3 Fe 1 / 3 Mn 1 / 3Specific high-valence niobium ion doping is carried out on the O2-layered sodium-ion battery cathode, which can inhibit the phase change that occurs during the charge and discharge process of the material, disrupt the Na + / vacancy order, thereby improving the structural stability and further improving its electrochemical performance.

[0006] The technical solution adopted in this invention is:

[0007] A polycrystalline O3-type layered sodium-ion battery cathode material, the sodium-ion battery cathode material is a polycrystalline O3-type layered sodium-ion battery cathode material, and its molecular formula is Na(Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 ) 1-x Nb x O2, where 0 < x ≤ 0.1. In the polycrystalline O3-type layered sodium-ion battery cathode material, the mesoscopic and / or macroscopic morphology is spherical secondary particles, and the spherical secondary particles are composed of lamellar primary particles.

[0008] Preferably, the value of x is 0.005 to 0.03.

[0009] As a further preference, the value of x is 0.005 to 0.025.

[0010] As an even further preference, the value of x is 0.015 to 0.025, which of course includes the parameter range of 0.019 to 0.021 and parameters such as 0.02.

[0011] Preferably, the particle size of a single secondary particle is 1 to 5 micrometers, preferably 1 to 2 micrometers.

[0012] The preparation method of a polycrystalline O3-type layered sodium-ion battery cathode material in this invention includes the following steps:

[0013] (1) According to the set molar ratio in the molecular formula, grind and mix the polycrystalline raw material with the sodium source and the niobium source evenly to obtain a mixed powder; the polycrystalline raw material is polycrystalline (Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 )CO3;

[0014] (2) Keep the mixed powder at 400 - 600 °C for 4 - 8 h first, and then keep it at 850 - 950 °C for 10 - 20 h to obtain the O3-type layered sodium-ion battery cathode material.

[0015] Preferably, in step (1), the sodium source is sodium acetate, sodium nitrate or sodium carbonate; the niobium source is an oxide of niobium.

[0016] Preferably, the particle size of the polycrystalline raw material is less than or equal to 20 micrometers, preferably 1 - 10 micrometers.

[0017] As a preferred method, polycrystalline (Ni) is prepared by co-precipitation. 1 / 3 Fe 1 / 3 Mn 1 / 3 The specific steps for obtaining the CO3 precursor are as follows: NiSO4, FeSO4, and MnSO4 are dissolved in deionized water in a stoichiometric ratio of 1:1:1 to prepare a 1L solution A with a metal ion concentration of 2 mol / L. Then, a solution B is prepared with a Na2CO3 concentration of 2 mol / L and an NH3·H2O concentration of 0.24 mol / L. Using a peristaltic pump, solutions A and B are simultaneously injected into a 5L reaction vessel containing 1L of deionized water at a feed rate of 1.5 mL / min. The pH value in the reactor is controlled between 7.75 and 7.85 by adjusting the flow rate, and the reactor temperature is 55 ℃. After solution A or B has been added, the reaction product is removed, washed and filtered multiple times with deionized water to remove residual impurities, and then transferred to a vacuum oven and heated to 120 ℃ for 24 hours to obtain polycrystalline (NiSO4)2. 1 / 3 Fe 1 / 3 Mn 1 / 3 CO3 precursor. Of course, commercially available polycrystalline (Ni) 1 / 3 Fe 1 / 3 Mn 1 / 3 CO3 precursors can also be used in this invention.

[0018] Preferably, the sodium source has a particle size of less than or equal to 150 micrometers, and more preferably 50-100 micrometers.

[0019] Preferably, the niobium source has a particle size of 200-500 nanometers.

[0020] Preferably, in step (2), the oxidizing atmosphere is an air atmosphere or an oxygen atmosphere.

[0021] Preferably, in step (2), the mixed powder is first heated from room temperature to 400-600℃ at a heating rate of 1-2℃ / min and kept at that temperature for 4-8 h, and then heated to 850-950℃ at a heating rate of 3-8℃ / min and kept at that temperature for 10-20 h.

[0022] After optimization, the product obtained by this invention can be assembled into a CR2016 button battery. After 200 cycles at 1C, the battery retains a capacity of ≥80%, and after further optimization, it retains a capacity of ≥85%.

[0023] After optimization, the product obtained by this invention can be assembled into a CR2016 button battery. After 100 cycles at 1C, the battery retains a capacity of ≥90.5%, and after further optimization, it retains a capacity of ≥92.5%, which is significantly higher than the prior art.

[0024] The principle of this invention

[0025] For existing polycrystalline O3-type NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 layered cathode materials suffer from poor cycle stability. This invention utilizes Nb... 5+ The introduction of [something] can disrupt the orderly arrangement of metal ions in the transition metal layer of the layered material, thereby suppressing the Na [something] during charging and discharging. + The ordered transformation of vacancies reduces Na + The diffusion barrier; considering the Nb doping in the lattice 5+ Valence state, in order to maintain electroneutrality, some Ni 3+ This reduces the structural distortion and slippage of layered materials during charge and discharge, thus acting as a stabilizer and enhancing structural stability. Compared to single-crystal structures, polycrystalline layered oxides are generally cheaper to prepare and easier to mass-produce. Furthermore, polycrystalline layered oxides can provide higher specific capacity to meet the demands of high-energy-density applications. They also offer advantages in rate performance; by modifying their microstructure through doping, the structural stability of the material can be effectively improved, enhancing cycle life.

[0026] Beneficial effects

[0027] (1) The material prepared after element doping is still pure O3 phase and will not change the structural characteristics of the original material.

[0028] (2) The prepared material can effectively suppress the complex phase transition that occurs in polycrystalline O3 type layered materials during charging and discharging, improve structural stability, and thus improve the electrochemical performance of the material.

[0029] (3) The introduction of Nb disrupts the ordered arrangement in the transition metal layer of the layered material, thereby disrupting the Na + / Empty spaces ordered, reducing Na + Diffusion barrier improves the rate performance of materials.

[0030] (4) The preparation method provided by the present invention is simple, the conditions are easy to control, and it is easy to industrialize. Attached Figure Description

[0031] Figure 1 These are electron scanning micrographs of the cathode materials obtained in Example 1 and Comparative Example 1;

[0032] Figure 2 These are the cycling performance diagrams of the cathode materials obtained in Example 1 and Comparative Example 1 at 1C;

[0033] Figure 3 These are the X-ray diffraction patterns of the cathode materials obtained in Examples 2 and 1;

[0034] Figure 4 These are electron scanning micrographs of the cathode materials obtained in Examples 2 and 1;

[0035] Figure 5 These are the cycling performance diagrams at 1C for the cathode materials obtained in Examples 2 and 1;

[0036] Figure 6 These are rate test graphs of the cathode materials obtained in Example 2 and Example 1;

[0037] Figure 7 This is the X-ray diffraction pattern of the cathode material obtained in Example 3;

[0038] Figure 8 This is a graph showing the cycling performance of the cathode material obtained in Example 3 at 1C.

[0039] Figure 9 This is the X-ray diffraction pattern of the cathode material obtained in Example 4;

[0040] Figure 10 This is a graph showing the cycling performance of the cathode material obtained in Example 4 at 1C.

[0041] Figure 11 This is the X-ray diffraction pattern of the cathode material obtained in Example 5;

[0042] Figure 12 This is a graph showing the cycling performance of the cathode material obtained in Example 5 at 1C.

[0043] Figure 13 These are particle size diagrams of cathode materials with different Nb doping amounts in the examples and comparative examples. Detailed Implementation

[0044] Example 1

[0045] Polycrystalline NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 preparation: The steps are as follows:

[0046] Weigh 1.8098 g of polycrystalline (Ni) 1 / 3 Fe 1 / 3 Mn 1 / 3 Commercially available CO3 powder (particle size 1-10 micrometers) and 1.1185 g Na2CO3 powder (particle size 50-100 micrometers) were ground and crushed in a mortar. The mixture was then stirred at 500 r / min until homogeneous. The homogeneous powder was transferred to a muffle furnace and heated to 450℃ at a rate of 1℃ / min, held for 6 h, then heated to 900℃ at a rate of 5℃ / min and held for 20 h. After cooling to room temperature in the furnace, the polycrystalline O3-type layered oxide sodium-ion battery cathode material NaNi was obtained.1 / 3 Fe 1 / 3 Mn 1 / 3 O2, after grinding, controls the particle size of the material to be between 1 and 2 micrometers.

[0047] Electrochemical performance measurement:

[0048] Using NMP as a medium, the NaNi prepared above was... 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, acetylene black, and PVDF are mixed evenly in a mass ratio of 8:1:1 to form a slurry. This slurry is then evenly coated onto aluminum foil, dried, and cut into positive electrode sheets with a diameter of 12 mm. Sodium metal sheets are used as negative electrodes, glass fiber GF / D is used as a separator, and a 1M NaPF6 PC / FEC (volume ratio of 95:5) solution is used as an electrolyte. The cells are then assembled into CR2016 button cells in an argon-filled glove box.

[0049] Comparative Example 1

[0050] Same as Example 1, except that single-crystal (Ni) crystals are used. 1 / 3 Fe 1 / 3 Mn 1 / 3 CO3 powder (particle size 1-5 micrometers) was used to prepare a single-crystal O3-type NaNi material. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 layered cathode material.

[0051] The batteries assembled in Example 1 and Comparative Example 1 were subjected to charge-discharge cycle tests in the Xinwei Battery Testing System under the same test conditions: voltage range of 2–4.0V and test temperature of 30°C.

[0052] like Figure 1 The image shows scanning electron micrographs of Example 1 and Comparative Example 1. It can be seen from the image that the two exhibit different morphologies. Example 1 consists of spherical secondary particles composed of lamellar primary particles, while Comparative Example 1 shows a large single crystal.

[0053] like Figure 2 As shown, the cycle performance test results of Example 1 and Comparative Example 1 are presented. The initial capacity of the battery in Comparative Example 1 is slightly higher, but the capacity retention rate after 200 cycles at 1C is only 62.45%. In contrast, the capacity retention rate of the battery in Example 1 increases to 67.19% after 200 cycles at 1C, and the cycle performance is significantly improved.

[0054] Example 2

[0055] Polycrystalline Na(Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 )1-x Nb x Preparation of O2 (x = 0.02, in molar ratio): The steps are as follows:

[0056] Same as Example 1, except that: the Nb doping amount of the cathode material is 2%, and the prepared cathode material is polycrystalline Na(Ni) 1 / 3 Fe 1 / 3 Mn 1 / 3 ) 0.98 Nb 0.02 O2. Specifically: Weigh 1.7736 g of polycrystalline (Ni) 1 / 3 Fe 1 / 3 Mn 1 / 3 1.1185 g of Na₂CO₃ powder (particle size 1-10 μm), 1.1185 g of Na₂CO₃ powder (particle size 50-100 μm), and 0.0537 g of niobium pentoxide (particle size 200-500 nm) were ground and crushed in a mortar and stirred evenly at a stirring speed of 500 r / min. The uniformly mixed powder was transferred to a muffle furnace and heated to 450 °C at a heating rate of 1 °C / min, held at that temperature for 6 h, and then heated to 900 °C at a heating rate of 5 °C / min, held at that temperature for 20 h. After cooling to room temperature in the furnace, polycrystalline Na(Ni)₂CO₃ was obtained. 1 / 3 Fe 1 / 3Mn 1 / 3 ) 0.98 Nb 0.02 O2.

[0057] like Figure 3 The X-ray diffraction patterns of the cathode materials in Examples 2 and 1 are shown, demonstrating that Nb doping does not change the original structural characteristics.

[0058] like Figure 4 The images shown are scanning electron micrographs of Examples 2 and 1. It can be seen from the images that both are spherical secondary particles composed of lamellar primary particles, proving that Nb doping does not change the original morphology.

[0059] like Figure 5 As shown, the cycle performance test results of Example 2 and Example 1 are presented. The initial capacity of the battery in Example 1 is slightly higher, but the capacity retention rate after 200 cycles at 1C is only 67.19%. In contrast, the capacity retention rate of the battery in Example 2 increases to 92.81% after 100 cycles at 1C, and to 85.55% after 200 cycles at 1C, indicating a significant improvement in cycle performance.

[0060] like Figure 6 As shown, the results indicate that the capacity of Example 2 is significantly better than that of Example 1 under different rate testing conditions.

[0061] Example 3

[0062] Same as Example 1, except that: the Nb doping amount of the cathode material is 3% (molar ratio), and the prepared cathode material is Na(Ni) 1 / 3 Fe 1 / 3 Mn 1 / 3 ) 0.97 Nb 0.03 O2.

[0063] like Figure 7 As shown in the XRD pattern of Example 3, the cathode material obtained in Example 3 is still in the O3 phase. However, due to the increase in niobium doping, the Na3NbO4 impurity phase appears.

[0064] like Figure 8 The results shown are the cycle performance test results of Example 3. Compared with Example 1, the capacity retention rate of Example 3 is improved, reaching 81.35%, which is similar to that of Example 2. After 100 cycles at 1C, the capacity retention rate of the battery in Example 3 increased to 90.72%.

[0065] The reason for this is that the capacity may be reduced compared to Example 2, possibly due to the increased doping amount and the fact that the doping element is an electrochemically inactive element.

[0066] Example 4

[0067] Same as Example 1, except that: the Nb doping amount of the cathode material is 0.5% (molar ratio), and the prepared cathode material is Na(Ni) 1 / 3 Fe 1 / 3 Mn 1 / 3 ) 0.995 Nb 0.005 O2.

[0068] like Figure 9 As shown in the XRD pattern, the cathode material obtained in Example 4 is still in the O3 phase.

[0069] like Figure 10 As shown, the cycle performance test results of Example 4 are shown. Compared with Example 1, the capacity retention rate of Example 4 is improved, reaching 71.86%.

[0070] Example 5

[0071] Same as Example 1, except that: the Nb doping amount of the cathode material is 0.1% (molar ratio), and the prepared cathode material is Na(Ni) 1 / 3 Fe 1 / 3 Mn 1 / 3 ) 0.99 Nb 0.01 O2.

[0072] like Figure 11 As shown in the XRD pattern of Example 5, the cathode material obtained in Example 5 is still in the O3 phase.

[0073] like Figure 12 As shown, the cycle performance test results of Example 5 show that the capacity retention rate of Example 5 is improved compared to Example 1, reaching 76.95%.

[0074] like Figure 13 The figure shows the particle size distribution of cathode materials with different Nb doping levels. As the Nb doping level increases, D... 50 As the concentration gradually decreases, it can be inferred that the introduction of Nb can refine the grain size.

Claims

1. A method for preparing a polycrystalline O3-type layered sodium-ion battery cathode material, characterized in that: Includes the following steps: (1) According to the molar ratio set in the molecular formula, the polycrystalline raw material is ground and mixed evenly with sodium source and niobium source to obtain a mixed powder; the polycrystalline raw material is polycrystalline (Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 CO3; (2) Place the mixed powder in an oxidizing atmosphere, first keep it at 400-600 °C for 4-8 h, and then keep it at 850-950 °C for 10-20 h to obtain the O3 type layered sodium-ion battery cathode material; The positive electrode material of the sodium-ion battery is a polycrystalline O3-type layered sodium-ion battery positive electrode material, and its molecular formula is Na(Ni 1 / 3Fe 1 / 3 Mn 1 / 3 ) 1-x Nb x O2, where 0 < x ≤ 0.

1. In the polycrystalline O3-type layered sodium-ion battery positive electrode material, the mesoscopic and / or macroscopic morphology is spherical secondary particles, and the spherical secondary particles are composed of lamellar primary particles.

2. The method for preparing a polycrystalline O3-type layered sodium-ion battery cathode material according to claim 1, characterized in that: The value of x ranges from 0.005 to 0.

03.

3. The method for preparing a polycrystalline O3-type layered sodium-ion battery cathode material according to claim 1, characterized in that: The value of x ranges from 0.005 to 0.

025.

4. The method for preparing a polycrystalline O3-type layered sodium-ion battery cathode material according to claim 1, characterized in that: The value of x ranges from 0.015 to 0.

025.

5. The method for preparing a polycrystalline O3-type layered sodium-ion battery cathode material according to claim 1, characterized in that: The particle size of a single secondary particle is 1-5 micrometers.

6. The method for preparing a polycrystalline O3-type layered sodium-ion battery cathode material according to claim 1, characterized in that: The particle size of a single secondary particle is 1-2 micrometers.

7. The method for preparing a polycrystalline O3-type layered sodium-ion battery cathode material according to claim 1, characterized in that: In step (1), the sodium source is sodium acetate, sodium nitrate or sodium carbonate; the niobium source is niobium oxide.

8. The method for preparing a polycrystalline O3-type layered sodium-ion battery cathode material according to claim 1, characterized in that: The particle size of the polycrystalline raw material is less than or equal to 20 micrometers; The sodium source has a particle size of less than or equal to 150 micrometers; The niobium source has a particle size of 200-500 nanometers.

9. The method for preparing a polycrystalline O3-type layered sodium-ion battery cathode material according to claim 1, characterized in that: The particle size of the polycrystalline raw material is 1-10 micrometers; The sodium source has a particle size of 50-100 micrometers.

10. The method for preparing a polycrystalline O3-type layered sodium-ion battery cathode material according to claim 6, characterized in that: In step (2), the oxidizing atmosphere is an air atmosphere or an oxygen atmosphere.

11. The method for preparing a polycrystalline O3-type layered sodium-ion battery cathode material according to claim 6, characterized in that: In step (2), the mixed powder is first heated from room temperature to 400-600 ℃ at a heating rate of 1-2 ℃ / min and kept at that temperature for 4-8 h, and then heated to 850-950 ℃ at a heating rate of 3-8 ℃ / min and kept at that temperature for 10-20 h.

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