Preparation method and application of element-doped low-nickel layered oxide sodium ion battery positive electrode material

Abstract

The invention provides a preparation method and application of an element-doped low-nickel layered oxide sodium-ion battery positive electrode material, and belongs to the technical field of sodium-ion battery positive electrode materials. A sodium source, a manganese source, a nickel source and a niobium source are subjected to ball milling and mixing according to a specific molar ratio; the Nb-doped low-nickel layered oxide sodium-ion battery positive electrode material is obtained after high-temperature sintering, the crystallinity of a crystal material can be remarkably enhanced, the structural defects are reduced, and the interlayer spacing is enlarged, so that the comprehensive electrochemical performance of the material serving as the sodium-ion battery positive electrode material is improved; according to the finally prepared element-doped low-nickel layered oxide sodium-ion battery positive electrode material, the reversible discharge specific capacity under the current density of 1.0 A / g is 104.3 mAh / g or above, and the capacity retention rate of 94.4% can still be kept after 200 cycles under the current density of 0.5 A / g.

Description

Technical Field

[0001] This invention belongs to the technical field of sodium-ion battery cathode materials, specifically relating to a method for preparing and applying an element-doped low-nickel layered oxide sodium-ion battery cathode material. Background Technology

[0002] Sodium-ion batteries (SIBs) are becoming increasingly important as an alternative to lithium-ion batteries in grid and large-scale energy storage applications because the elements used in sodium-ion batteries (such as Na, Fe, and Mn) are abundant on Earth. However, a stable and high-capacity cathode is a prerequisite for improving the energy density of SIBs, which urgently needs to be further increased to meet the growing energy storage demands.

[0003] Among the various reported cathode materials, layered transition metal oxides (LTMOs) are ideal candidates because of their tunable composition, reasonable capacity, and easily customizable electrochemical performance by introducing different elements into the host structure. P2-type LTMOs, with their large prismatic residence sites and easy diffusion pathways for sodium ions, generally exhibit better electrochemical performance than O3-type materials, such as P2-Na. 2 / 3 Mn 1 / 2 Ni 1 / 2 O2 is considered an attractive cathode for SIBs due to its abundant and low-cost raw materials, environmental friendliness, and significant theoretical specific capacity (175 mAh / g). However, due to Mn... 3+ The Jahn-Teller lattice distortion caused by this process is typically observed to degrade the cycling performance of this material and the Na + During the deintercalation process, a phase transition occurs under high pressure. However, high-nickel materials are prone to P2-O2 phase transition during charging and discharging, which leads to slippage of the transition metal layer and lattice distortion. Therefore, low-nickel materials are selected when designing materials to reduce the tendency of P2-O2 phase transition.

[0004] Cation doping (e.g., Li) + Mg 2+ Cu 2+ Using Cu (etc.) to prepare cathode materials with superior performance suitable for practical applications is an effective and practical strategy. Studies have found that Cu... 2+ Doping can stabilize the structure and suppress the P2-O2 phase transition. The capacity at 0.1 C is 125.7 mAh / g, and the capacity retention rate after 100 cycles is 79.1% (Journal of Artificial Crystals, 2024, 53 (1): 145-153, 162.). Although this doping method can improve the structural stability, it causes capacity decay at the cost of capacity due to blocking the sodium ion diffusion channel, making it difficult to obtain a cathode material with excellent comprehensive performance. Summary of the Invention

[0005] To address the problems existing in the background technology, this invention proposes a method for preparing element-doped low-nickel layered oxide sodium-ion battery cathode materials, which can effectively improve the structural stability of cathode materials and simultaneously achieve a comprehensive improvement in rate performance, cycle performance, and specific capacity, ultimately obtaining cathode materials with both high capacity and excellent cycle performance.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing an element-doped low-nickel layered oxide sodium-ion battery cathode material includes the following steps: Step 1: Weigh sodium carbonate (Na2CO3), manganese trioxide (Mn2O3), nickel oxide (NiO), and niobium pentoxide (Nb2O5) according to the molar ratio of Na, Mn, Ni, and Nb of 67:83:15:X, mix them evenly, and ball mill them to obtain the precursor material. Step 2: Press the precursor material obtained in Step 1 into a molded material using a tablet press. Then, sinter the molded material at high temperature to obtain the element-doped low-nickel layered oxide sodium-ion battery cathode material.

[0007] Furthermore, in step 1, the value of X ranges from 1 to 5.

[0008] Furthermore, the ball milling time in step 1 is 2-6 hours.

[0009] Furthermore, in step 2, the pressure during the pressing process is 10-20 MPa, and the holding time is 1-5 minutes.

[0010] Furthermore, the sintering atmosphere during the high-temperature sintering process in step 2 is either air or oxygen.

[0011] Furthermore, in step 2, the heating rate during the high-temperature sintering process is 4-6℃ / minute, and the sintering temperature is 900-950℃.

[0012] Furthermore, the holding time during the high-temperature sintering process in step 2 is 8-15 hours.

[0013] Another objective of this invention is to provide an application of an element-doped low-nickel layered oxide sodium-ion battery cathode material, that is, to use the element-doped low-nickel layered oxide sodium-ion battery cathode material prepared by the above-described method in a sodium-ion battery.

[0014] This application has the following beneficial effects: 1. This invention provides a method for preparing a low-nickel layered oxide sodium-ion battery cathode material doped with elements, which improves P2-Na through low-nickel design and Nb doping.2 / 3 Mn 1 / 2 Ni 1 / 2 The structural stability of O2 cathode materials enables a comprehensive improvement in specific capacity, rate capability, and cycle performance. At the same time, its low manufacturing cost and simple preparation process are in line with the concept of green and economical development, and it has broad application prospects in large-scale energy storage and other fields.

[0015] 2. This invention synthesizes a P2-type layered oxide sodium-ion battery cathode material with both high capacity and excellent cycle performance via solid-state sintering. The low-nickel design and trace element doping increase the XRD diffraction peak intensity and reduce broadening, effectively improving the crystallinity and internal stress of the cathode material. Simultaneously, it increases the interlayer spacing, resulting in faster Na+ oxidation. + The cathode material exhibits excellent transport rate and overall electrochemical performance. After 200 cycles at 0.5 A / g, the final cathode material retains 94.4% of its capacity. Furthermore, the low-nickel design and Nb doping produce synergistic effects, significantly improving the reversible discharge capacity of the electrode material. Attached Figure Description

[0016] Figure 1 Scanning electron microscope image of the element-doped low-nickel layered oxide sodium-ion battery cathode material prepared in Example 1; Figure 2 Example 1: X-ray diffraction pattern of element-doped low-nickel layered oxide sodium-ion battery cathode material; Figure 3 X-ray diffraction pattern of element-doped low-nickel layered oxide sodium-ion battery cathode material prepared in Comparative Example 1; Figure 4 Comparison of magnified X-ray diffraction patterns of element-doped low-nickel layered oxide sodium-ion battery cathode materials prepared in Example 1 and Comparative Example 1; Figure 5 Rate performance diagrams of element-doped low-nickel layered oxide sodium-ion battery cathode materials prepared in Example 1 and Comparative Example 1; Figure 6 Cycle performance diagrams of element-doped low-nickel layered oxide sodium-ion battery cathode materials prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0017] The present application will be further described in detail below with reference to the embodiments.

[0018] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0019] Example 1

[0020] A method for preparing an element-doped low-nickel layered oxide sodium-ion battery cathode material includes the following steps: Step 1: Weigh sodium carbonate (Na2CO3), manganese trioxide (Mn2O3), nickel oxide (NiO), and niobium pentoxide (Nb2O5) according to the molar ratio of Na, Mn, Ni, and Nb of 67:83:15:2, mix them evenly, and ball mill them for 4 hours to obtain the precursor material. Step 2: Press the precursor material obtained in Step 1 into a mold using a tablet press. The pressure is 15 MPa and the holding time is 3 minutes to obtain the molded material. Then, the molded material is heated from room temperature to 925 ℃ at a heating rate of 5 ℃ / min for high-temperature sintering. The sintering atmosphere is air and the holding time is 10 h to obtain the element-doped low-nickel layered oxide sodium-ion battery cathode material, denoted as NMNN.

[0021] Example 2

[0022] A method for preparing an element-doped low-nickel layered oxide sodium-ion battery cathode material includes the following steps: Step 1: Weigh sodium carbonate (Na2CO3), manganese trioxide (Mn2O3), nickel oxide (NiO), and niobium pentoxide (Nb2O5) according to the molar ratio of Na, Mn, Ni, and Nb of 67:83:15:5, mix them evenly, and ball mill them for 2 hours to obtain the precursor material. Step 2: Press the precursor material obtained in Step 1 into a mold using a tablet press at a pressure of 10 MPa for 5 minutes to obtain a molded material. Then, heat the molded material from room temperature to 900 ℃ at a heating rate of 4 ℃ / min for high-temperature sintering in an air atmosphere for 15 h to obtain the element-doped low-nickel layered oxide sodium-ion battery cathode material.

[0023] Example 3

[0024] A method for preparing an element-doped low-nickel layered oxide sodium-ion battery cathode material includes the following steps: Step 1: Weigh sodium carbonate (Na2CO3), manganese trioxide (Mn2O3), nickel oxide (NiO), and niobium pentoxide (Nb2O5) according to the molar ratio of Na, Mn, Ni, and Nb of 67:83:15:1, mix them evenly, and ball mill them for 6 hours to obtain the precursor material. Step 2: Press the precursor material obtained in Step 1 into a mold using a tablet press at a pressure of 20 MPa and a holding time of 1 minute to obtain a molded material. Then, heat the molded material from room temperature to 950 ℃ at a heating rate of 6 ℃ / min for high-temperature sintering in an oxygen atmosphere for 8 h to obtain the element-doped low-nickel layered oxide sodium-ion battery cathode material.

[0025] Comparative Example 1 The only difference between this comparative example and Example 1 is that nickel oxide (NiO) and niobium pentoxide (Nb2O5) are not added in the preparation of the precursor materials, as detailed below: A method for preparing an element-doped low-nickel layered oxide sodium-ion battery cathode material includes the following steps: Step 1: Mix sodium carbonate (Na2CO3) and manganese trioxide (Mn2O3) evenly according to the molar ratio of Na to Mn of 67:83, and ball mill them for 4 hours to obtain the precursor material. Step 2: Press the precursor material obtained in Step 1 into a mold using a tablet press at a pressure of 15 MPa for 3 minutes to obtain a molded material. Then, heat the molded material from room temperature to 925 °C at a heating rate of 5 °C / min for high-temperature sintering in an air atmosphere for 10 hours to obtain the element-doped low-nickel layered oxide sodium-ion battery cathode material, denoted as NM.

[0026] Comparative Example 2 The only difference between this comparative example and Example 1 is that nickel oxide (NiO) is not added in the preparation of the precursor material, as follows: A method for preparing an element-doped low-nickel layered oxide sodium-ion battery cathode material includes the following steps: Step 1: Weigh sodium carbonate (Na2CO3), manganese trioxide (Mn2O3), and niobium pentoxide (Nb2O5) according to the molar ratio of Na, Mn, Ni, and Nb of 67:83:2, mix them evenly, and ball mill them for 4 hours to obtain the precursor material. Step 2: Press the precursor material obtained in Step 1 into a mold using a tablet press at a pressure of 15 MPa for 3 minutes to obtain a molded material. Then, heat the molded material from room temperature to 925 °C at a heating rate of 5 °C / min for high-temperature sintering in an air atmosphere for 10 hours to obtain the element-doped low-nickel layered oxide sodium-ion battery cathode material.

[0027] Comparative Example 3 The only difference between this comparative example and Example 1 is that niobium pentoxide (Nb₂O₅) is not added in the preparation of the precursor material, as detailed below: A method for preparing an element-doped low-nickel layered oxide sodium-ion battery cathode material includes the following steps: Step 1: Weigh sodium carbonate (Na2CO3), manganese trioxide (Mn2O3), and nickel oxide (NiO) according to the molar ratio of Na, Mn, Ni, and Nb of 67:83:15, mix them evenly, and ball mill them for 4 hours to obtain the precursor material. Step 2: Press the precursor material obtained in Step 1 into a mold using a tablet press at a pressure of 15 MPa for 3 minutes to obtain a molded material. Then, heat the molded material from room temperature to 925 °C at a heating rate of 5 °C / min for high-temperature sintering in an air atmosphere for 10 hours to obtain the element-doped low-nickel layered oxide sodium-ion battery cathode material.

[0028] Proof of effectiveness The positive electrode materials prepared in Examples 1-3 and Comparative Examples 1-3 were mixed and ground with polyvinylidene fluoride (PVDF) and carbon black at a mass ratio of 8:1:1. After dilution with N-methylpyrrolidone, the mixture was coated onto aluminum foil and dried under vacuum at 75°C for 6 h to prepare circular electrode sheets with a diameter of 12 mm. Using 1 M NaClO4 (EC / DEC = 1:1 volume ratio, 5% FEC) as the electrolyte, a glass fiber membrane as the separator, and a Na metal sheet as the negative electrode, button half-cells were prepared in a glove box for electrochemical performance testing. The voltage window was 1.8-4.4 V. Specific test results are as follows: Figure 5-6 As shown in Table 1: Table 1

[0029] Results Analysis Figure 1 The scanning electron microscope image of the cathode material prepared in Example 1 is shown, which also conforms to the characteristics of a hexagonal crystal material.

[0030] Figure 2 and Figure 3 The X-ray diffraction patterns of the cathode materials prepared in Example 1 and Comparative Example 1 are shown respectively. Both are indexed to the hexagonal space group P63 / mmc, which is a typical P2 type layered material structure.

[0031] Figure 4The image shows magnified X-ray diffraction patterns of the cathode materials prepared in Example 1 and Comparative Example 1 in the 2 theta range of 15-16.2°. It can be clearly observed that the (002) characteristic peak of NMNN in Example 1 has a stronger peak intensity. This indicates that the low-nickel design and Nb doping improve the crystallinity of the cathode material, reducing structural defects during sintering. Furthermore, the (002) characteristic peak of NMNN in Example 1 shifts to a lower angle. According to the Bragg equation, NMNN has a larger interlayer spacing, which is beneficial for Na… + Rapid transport is beneficial for rate performance in electrochemical applications.

[0032] Figure 5 The rate performance graphs of the cathode materials prepared in Example 1 and Comparative Example 1 are shown. In Example 1, the NMNN sample exhibited a reversible discharge specific capacity of 184.1 mAh / g at a current density of 0.05 A / g and still showed a reversible discharge specific capacity of 105.1 mAh / g at a current density of 1.0 A / g, which is at a leading level among this type of material. In Comparative Example 1, the reversible discharge specific capacities of NM at current densities of 0.05 A / g and 1.0 A / g were 152.2 mAh / g and 43.9 mAh / g, respectively. It can be seen that through the combined treatment of low nickel design and Nb doping, the rate performance of NMNN in Example 1 was significantly improved. Furthermore, after cycling performance testing, after 200 cycles at a current density of 0.5 A / g, NMNN in Example 1 still retained 94.4% of its capacity. Figure 6 In contrast, NM in Comparative Example 1 has already experienced performance failure.

[0033] Table 1 shows the reversible discharge specific capacity of the cathode materials prepared in Examples 1-3 and Comparative Examples 1-3 at 1.0 A / g. It can be seen that the element-doped low-nickel layered oxide sodium-ion battery cathode materials (Examples 1-3) provided by the present invention have a high reversible discharge specific capacity, with a reversible discharge specific capacity of over 104.3 mAh / g at a current density of 1.0 A / g. At the same time, analysis of Examples 1 and Comparative Examples 1-3 shows that in the preparation method provided by the present invention, the combined use of low-nickel design and Nb doping can produce synergistic effects and significantly improve the reversible discharge specific capacity of the electrode material.

[0034] The above characterization and testing results confirm that the combined use of low-nickel design and Nb doping can yield a P2-type layered structure with fewer structural defects, while also providing a wider Na+ range. + The transmission channel is beneficial to Na +Rapid diffusion, structural refinement, and optimization have effectively improved the overall performance of element-doped low-nickel layered oxide sodium-ion battery cathode materials, giving them high reversible discharge specific capacity and excellent cycle performance.

[0035] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0036] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing an element-doped low-nickel layered oxide sodium-ion battery cathode material, characterized in that, Includes the following steps: Step 1: Weigh sodium carbonate, manganese trioxide, nickel oxide, and niobium pentoxide according to the molar ratio of Na, Mn, Ni, and Nb as 67:83:15:X, mix them evenly, and then ball mill them to obtain the precursor material. Step 2: Press the precursor material obtained in Step 1 into a molded material using a tablet press. Then, sinter the molded material at high temperature to obtain the element-doped low-nickel layered oxide sodium-ion battery cathode material.

2. The preparation method according to claim 1, characterized in that, In step 1, the value of X ranges from 1 to 5.

3. The preparation method according to claim 1, characterized in that, The ball milling time in step 1 is 2-6 hours.

4. The preparation method according to claim 1, characterized in that, In step 2, the pressure during the pressing process is 10-20 MPa, and the holding time is 1-5 minutes.

5. The preparation method according to claim 1, characterized in that, In step 2, the sintering atmosphere during high-temperature sintering is either air or oxygen.

6. The preparation method according to claim 1, characterized in that, In step 2, during high-temperature sintering, the heating rate is 4-6℃ / minute, and the sintering temperature is 900-950℃.

7. The preparation method according to claim 1, characterized in that, The holding time during high-temperature sintering in step 2 is 8-15 hours.

8. The application of an element-doped low-nickel layered oxide sodium-ion battery cathode material, characterized in that, The element-doped low-nickel layered oxide sodium-ion battery cathode material prepared by any one of the preparation methods described in claims 1-7 is used in sodium-ion batteries.

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