Sodium ion positive electrode material for customizing ordering degree of transition metal layer and preparation method of sodium ion positive electrode material
By precisely controlling the lithium doping amount to regulate the degree of order/disorder in the TM layer, a sodium-ion battery cathode material with TM ordered and TM disordered phases was prepared. This solved the contradiction between cycle stability and reversible capacity in P2 phase materials, achieved a balance between high capacity and long cycle life, and improved the electrochemical performance of the material.
Patent Information
- Application Number
- CN202511639134.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-10
- Publication Date
- 2026-02-13
AI Technical Summary
There is a contradiction between the ordered structure of the TM layer and the electrochemical performance of existing P2 phase sodium-ion battery cathode materials, resulting in poor cycle stability, low reversible capacity, and poor rate performance.
By precisely controlling the amount of lithium doping, the degree of order/disorder in the TM layer can be continuously regulated, and a composite structure in which the TM ordered phase and the TM disordered phase coexist can be prepared. Combined with mechanical mixing and high-temperature calcination, a sodium-ion battery cathode material with high reversible capacity, excellent cycle stability and good rate performance can be obtained.
The optimal balance between high capacity and long cycle life of sodium-ion battery cathode materials has been achieved. The ordered TM phase provides structural stability, while the disordered TM phase provides ion migration channels and active sites, thereby improving the overall electrochemical performance of the material.
Smart Images
Figure CN121528903A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of key electrode materials technology for sodium-ion batteries, specifically to a layered oxide cathode material, and particularly to a method for controllably preparing an ordered / disordered structure of a transition metal layer (TM layer) by precisely controlling the amount of lithium doping, and the resulting high-performance sodium-ion battery cathode material. Background Technology
[0002] Sodium-ion batteries have become a key research focus in the post-lithium-ion battery era due to their cost advantages and promising applications in large-scale energy storage. Among numerous cathode material systems, sodium-rich P2-type layered oxides are favored for their high capacity and high ionic conductivity. However, the electrochemical performance of P2 phase materials is profoundly influenced by the atomic arrangement within their transition metal (TM) layers, i.e., their ordered or disordered structure. Typically, in Ni / Mn-based materials, Ni... 2+ and Mn 4+ Due to differences in valence state and ionic radius, ordered superlattice structures tend to form within the TM layer. While this ordered structure helps improve the cycling stability of the material, it often leads to lower reversible capacity and poor rate performance because it restricts the diffusion path of sodium ions and may trigger irreversible phase transitions. Conversely, a completely disordered TM layer structure may provide more sodium ion diffusion channels and higher initial capacity, but the lack of long-range ordered support makes the material more prone to structural collapse during cycling, resulting in rapid capacity decay and poor cycle life.
[0003] Therefore, precisely controlling the degree of order / disorder in the TM layer to find the optimal balance between high capacity and long cycle life is a key scientific problem and technical challenge that urgently needs to be solved in this field. While existing doping strategies (such as Li, Mg, and Cu doping) are widely used to stabilize structures, their mechanisms are often broadly attributed to "suppressing phase transitions" or "stabilizing the crystal lattice." There is a lack of clear, in-depth, and guiding understanding of how doping affects and controls the arrangement of TM ions (i.e., the degree of ordering) at the atomic level, and the structure-property relationship between this control and the final electrochemical performance. In particular, how lithium doping gradually and continuously alters the microstructure of the TM layer, thereby triggering the evolution of macroscopic phase structures (such as P2 and P3 phases), remains a research gap.
[0004] In view of this, the inventors, through in-depth research, discovered that in Na 0.85 Li x M 1-x In the O2 system, the amount of lithium (Li) doping (x value) is the key switch to regulate the degree of ordering of the TM layer and can trigger a series of chain reactions.
[0005] This invention discovers that the symbiotic structure of ordered and disordered TM phases can produce a synergistic enhancement effect: the ordered TM phase, acting as a robust "skeleton," ensures excellent structural stability and long cycle life; while the disordered TM phase provides abundant ion migration channels and active sites, contributing high capacity and good rate performance. This ingenious balance in microstructure enables the material to achieve ultra-long cycle stability while possessing high capacity.
[0006] Currently, there are no patents or literature reports on how to continuously control the degree of order / disorder in the TM layer by precisely controlling the amount of lithium doping, and ultimately obtain the optimal overall electrochemical performance. This invention is based on this profound discovery. Summary of the Invention
[0007] Based on the aforementioned background technology, this invention aims to resolve the contradiction between the ordered TM layer and electrochemical performance in existing P2 phase sodium-ion battery cathode materials. Specifically, it seeks to overcome the technical challenges of poor cycle stability caused by a completely disordered TM layer, and low reversible capacity and poor rate performance caused by a completely ordered TM layer.
[0008] The purpose of this invention is to provide a sodium-ion battery cathode material and its preparation method. This method can achieve continuous and controllable preparation of the degree of order / disorder in the transition metal layer of the material by precisely controlling the amount of lithium doping, thereby obtaining a cathode material with high reversible capacity, excellent cycle stability and good rate performance.
[0009] A sodium-ion cathode material, characterized in that it has the general formula Na 0.85 Li x M 1-x O2; it uses lithium to treat Na 0.85 MO2 is obtained by substituting some transition metal atoms, resulting in a P2, P2 / P3, or P3 phase; it is obtained by using fluorine to replace Na. 0.67 The composite phase having a P-phase / tunneling phase is obtained by substituting some oxygen atoms in MO2; wherein M represents a transition metal, and x is less than 0.3 and greater than 0. The above M is selected from at least one of Ni, Fe, Cu, Co, Cr, Zn, Ti, V, Nb, and Mn.
[0010] The present invention also provides a method for preparing the above-mentioned sodium ion cathode material, which involves mixing a transition metal source precursor, a sodium source, and a fluorine source, and calcining them at 800°C to 1000°C for 12 to 18 hours in an oxygen-containing atmosphere.
[0011] The transition metal source precursor is selected from at least one of transition metal hydroxides, transition metal salts, and transition metal oxides, and the transition metal element is selected from at least one of Ni, Fe, Cu, Co, Cr, Zn, Ti, V, Nb, and Mn. The transition metal source precursor is preferably a manganese salt or manganese oxide; when it is a manganese salt, it is selected from at least one of manganese carbonates, acetates, nitrates, chlorides, sulfates, borates, or phosphates; when it is a manganese oxide, it is selected from at least one of manganese oxide, manganese trioxide, manganese dioxide, and manganese tetroxide.
[0012] The sodium source is selected from at least one of sodium carbonate, sodium bicarbonate, sodium sulfate, sodium nitrate, sodium phosphate, sodium fluoride, sodium iodide, sodium oxalate, and sodium hydroxide.
[0013] The lithium source is selected from at least one of lithium fluoride, lithium carbonate, lithium oxide, lithium nitrate, lithium acetate, and lithium sulfate.
[0014] The molar ratio of sodium ions in the sodium source, transition metal elements in the transition metal source precursor, and fluoride ions in the lithium source is 0.85:0.75~1:0~0.25.
[0015] The oxygen-containing atmosphere is either an oxygen atmosphere or an air atmosphere, with an oxygen atmosphere being preferred. The main mixing methods include: mechanical mixing, solid-state reaction, hydrothermal, sol-gel, precipitation, and deposition. Among these, solid-state reaction is the simplest and most convenient method for synthesis, and is most suitable for commercialization. However, current solid-state reaction methods for surface coating are often combined with sol-gel or precipitation methods, or involve secondary sintering. The entire process is relatively cumbersome and prone to uneven and weak coating. Therefore, mechanical mixing is preferred, especially ball milling.
[0016] The present invention also provides a battery in which the positive electrode material includes the sodium ion positive electrode material described above, or a sodium ion positive electrode material prepared using the above-described method for preparing sodium ion positive electrode material.
[0017] Beneficial Effects: This invention discovers that the symbiotic structure of the ordered and disordered TM phases can produce a synergistic enhancement effect: the ordered TM phase, acting as a robust "skeleton," ensures excellent structural stability and long cycle life; while the disordered TM phase provides abundant ion migration channels and active sites, contributing high capacity and good rate performance. This ingenious balance in microstructure enables the material to achieve ultra-long cycle stability while possessing high capacity. Attached Figure Description
[0018] Figure 1 The XRD patterns are of the samples prepared in Examples 1, 2, 3, 4, 5 and Comparative Example 1 of this invention.
[0019] Figure 2The first charge-discharge curves of the samples prepared in Examples 1, 2 and Comparative Example 1 at a current density of 20 mA / g are shown.
[0020] Figure 3 Long cycle diagrams of 200 cycles at a current density of 100 mA / g for samples prepared in Examples 1, 2 and Comparative Example 1;
[0021] Figure 4 Rate performance graphs of samples prepared in Examples 1, 2, and Comparative Example 1 at different current densities;
[0022] Figure 5 The images show SEM images and mappings of the samples prepared in Examples 1, 2, and Comparative Example 1 of this invention. Detailed Implementation
[0023] The invention will now be described in further detail with reference to the accompanying drawings and examples, but the invention is not limited to these examples.
[0024] In the following examples, the transition metal source precursors are Mn2O3 (manganese source), NiO (nickel source), Na2CO3 (sodium source), and Li2CO3 (lithium source); the masses of the manganese, nickel, lithium, and sodium sources are in accordance with the layered transition metal oxide Na... 0.85 Li x Mn 0.75- x Ni 0.25 The mixture is prepared according to the stoichiometric ratio of O2.
[0025] Example 1
[0026] 0.3 mol of Mn₂O₃, 0.25 mol of NiO, 0.425 mol of Na₂CO₃, and 0.075 mol of Li₂CO₃ (molar ratio Na:Li:Ni:Mn = 0.85:0.15:0.25:0.6) (with Na source in excess of 5%) were ball-milled (400 r / min, 6 h) until homogeneous. The mixture was then heated at 1000 °C for 15 h under an oxygen atmosphere and cooled to obtain 1 mol of composite phase fluorinated transition metal oxide powder Na. 0.85 Li 0.15 Mn 0.6 Ni 0.25 O2.
[0027] Example 2
[0028] 0.32 mol of Mn₂O₃, 0.25 mol of NiO, 0.425 mol of Na₂CO₃, and 0.055 mol of Li₂CO₃ (molar ratio Na:Li:Ni:Mn = 0.85:0.11:0.25:0.64) (with Na source in excess of 5%) were ball-milled (400 r / min, 6 h) until homogeneous. The mixture was then heated at 1000 °C for 15 h under an oxygen atmosphere and cooled to obtain 1 mol of composite phase fluorinated transition metal oxide powder Na. 0.85 Li 0.11 Mn 0.64 Ni 0.25 O2.
[0029] Example 3
[0030] 0.35 mol of Mn₂O₃, 0.25 mol of NiO, 0.425 mol of Na₂CO₃, and 0.025 mol of Li₂CO₃ (molar ratio Na:Li:Ni:Mn = 0.85:0.05:0.25:0.7) (with Na source in excess of 5%) were mixed thoroughly and then heated at 1000 °C for 15 h in an oxygen atmosphere. After cooling, 1 mol of composite phase fluorinated transition metal oxide powder Na was actually obtained. 0.85 Li 0.05 Mn 0.7 Ni 0.25 O2.
[0031] Example 4
[0032] 0.275 mol of Mn₂O₃, 0.25 mol of NiO, 0.425 mol of Na₂CO₃, and 0.1 mol of Li₂CO₃ (molar ratio Na:Li:Ni:Mn = 0.85:0.2:0.25:0.55) (with Na source in 5% excess) were mixed thoroughly and then heated at 1000 °C for 15 h in an oxygen atmosphere. After cooling, 1 mol of composite phase fluorinated transition metal oxide powder Na was actually obtained. 0.85 Li 0.2 Mn 0.55 Ni 0.25 O2.
[0033] Example 5
[0034] 0.25 mol of Mn₂O₃, 0.25 mol of NiO, 0.425 mol of Na₂CO₃, and 0.125 mol of Li₂CO₃ (molar ratio Na:Li:Ni:Mn = 0.85:0.25:0.25:0.5) (with Na source in 5% excess) were mixed thoroughly and then heated at 1000℃ for 15 h in an oxygen atmosphere. After cooling, 1 mol of composite phase fluorinated transition metal oxide powder Na was actually obtained. 0.85 Li 0.2 Mn 0.55 Ni 0.25 O2.
[0035] Comparative Example
[0036] 0.425 mol of Na₂CO₃, 0.375 mol of Mn₂O₃, and 0.25 mol of NiO (molar ratio Na:Ni:Mn = 0.85:0.25:0.75) (with Na source in excess of 5%) were ball-milled (400 r / min, 6 h). After being mixed evenly, the mixture was heated at 1000 °C for 15 h in an oxygen atmosphere and then cooled to obtain 1 mol of layered transition metal oxide powder Na. 0.85 Ni 0.25 Mn 0.75 O2.
[0037] Performance testing
[0038] XRD
[0039] XRD tests were performed on the materials obtained in Examples 1-5 and the comparative examples, and the results are as follows: Figure 1 As shown.
[0040] from Figure 1 As can be seen from the examples, Examples 1 and 4 are P2 / P3 composite phases with different degrees of superlattice, where P2 is a TM ordered phase and P3 is a TM disordered phase. Examples 2 and 3 are P2 phases with different degrees of superlattice, and Example 5 is a TM disordered P3 phase. This proves that the bulk phase of the cathode material obtained by the method of the present invention is mainly P phase. Furthermore, as the mass of the lithium source increases, the material gradually transitions from a completely TM disordered P2 phase to a TM ordered P2 phase, then to a composite of ordered P2 and disordered P3, and finally to a TM disordered P3 phase.
[0041] The comparative sample consists of the P phase, and based on the comparison between Comparative Example 1 and Examples 1-4, it can be demonstrated that lithium successfully entered the material.
[0042] SEM
[0043] SEM was performed on the materials obtained in Examples 1 and 2 and Comparative Example 1, and the results are as follows: Figure 5 As shown, Figure 5a represents a comparative SEM and mapping image. Figure 5 b represents the SEM and mapping images from Example 1. Figure 5 c represents the SEM and mapping images from Example 2.
[0044] As can be seen from the SEM images, the samples in the comparative example and the embodiment both have irregular plate-like morphology and uniform elemental distribution.
[0045] As can be seen from the above, this invention successfully synthesized P-type sodium-electric layered transition metal oxides with varying degrees of TM ordering through lithium introduction.
[0046] Electrode preparation and electrochemical performance testing
[0047] The prepared positive electrode material was uniformly mixed with superconducting carbon black (SuperP) and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1, dissolved in N-methylpyrrolidone (NMP), and coated onto the surface of aluminum foil. Then, it was heated to 80°C. ℃ A layered transition metal oxide electrode can be obtained by drying in a vacuum oven for 10 hours.
[0048] A layered transition metal oxide electrode was used as the positive electrode, a sodium metal sheet as the negative electrode, and 1.0 mol / L NaClO4 / propylene carbonate as the electrolyte. A half-cell was assembled in a glove box under argon atmosphere. The electrochemical performance of the layered transition metal oxide electrode material, including specific capacity, cycle stability, and rate performance, was tested in the range of 2–4.3 V. The test results are as follows: Figure 2 , 3 As shown in Figure 4.
[0049] Combined with the diagram Figure 2 , 3 As can be seen from Figure 4, when the material changes from TM to fully TM ordered, the cycling stability and rate performance of the material are significantly improved. However, at the same time, the capacity is reduced along with some of the phases. After further adjusting the material and introducing some disordered phases into the material, the capacity of the material is significantly improved at a certain ratio, thus achieving high cycling stability while maintaining capacity.
[0050] This invention, by controlling the amount of lithium introduced and precisely regulating the ordered arrangement of Li / Ni / Mn atoms in the transition metal (TM) layer, successfully prepared a unique microstructure in which an ordered P2 phase and a disordered P3 phase coexist in the TM layer. This structure resolves the inherent contradiction between poor cycle performance caused by complete disorder in the TM layer and low capacity caused by complete order in the TM layer in P2 phase materials. The ordered TM P2 phase acts as a stable framework, ensuring excellent cycle life, while the disordered TM P3 phase provides abundant ion migration channels and active sites, contributing to high capacity and good rate performance. The synergistic effect of the two phases enables the material to possess high specific capacity, long cycle stability, and excellent rate performance. The preparation method of this invention is simple and reproducible, providing a new approach for the design of high-performance sodium-ion battery cathode materials.
[0051] Unless otherwise specified, all technologies mentioned above refer to existing technologies.
[0052] Based on the above-described ideal examples of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the technical concept of the invention. The technical scope of this invention is not limited to the contents of the specification.
Claims
1. A sodium-ion cathode material, characterized in that, The general formula is Na 0.85 Li x M 1-x O2; it uses lithium to treat Na 0.85 MO2 is obtained by substituting some transition metal atoms, and has P2, P2 / P3 or P3 phases; where M represents a transition metal, and x is less than 0.3 and greater than 0.
2. The sodium-ion cathode material according to claim 1, characterized in that, The M is selected from at least one of Ni, Fe, Cu, Co, Cr, Zn, Ti, V, Nb, and Mn.
3. The method for preparing the sodium-ion cathode material according to claim 1 or 2, characterized in that, The transition metal source precursor, sodium source, and lithium source are mixed and calcined at 800℃~1000℃ for 12h~18h in an oxygen-containing atmosphere to obtain the product.
4. The method for preparing the sodium-ion cathode material according to claim 3, characterized in that, The transition metal source precursor is selected from at least one of transition metal hydroxides, transition metal salts, or transition metal oxides, and the transition metal element is selected from at least one of Ni, Fe, Cu, Co, Cr, Zn, Ti, V, Nb, and Mn.
5. The method for preparing the sodium-ion cathode material according to claim 3, characterized in that, The sodium source is selected from at least one of sodium carbonate, sodium bicarbonate, sodium sulfate, sodium nitrate, sodium phosphate, sodium fluoride, and sodium hydroxide.
6. The method for preparing the sodium-ion cathode material according to claim 3, characterized in that, The lithium source is selected from at least one of lithium fluoride, lithium carbonate, lithium oxide, lithium nitrate, lithium acetate, and lithium sulfate.
7. The method for preparing the sodium-ion cathode material according to claim 3, characterized in that, The molar ratio of sodium ions in the sodium source, transition metal elements in the transition metal source precursor, and fluoride ions in the lithium source is 0.85:0.75~1:0~0.
25.
8. The method for preparing the sodium-ion cathode material according to claim 3, characterized in that, The oxygen-containing atmosphere is either an oxygen atmosphere or an air atmosphere, and the mixing method is ball milling.
9. A battery, characterized in that, The positive electrode material in the battery includes the sodium-ion positive electrode material as described in claim 1 or 2, or the sodium-ion positive electrode material prepared by the method for preparing the sodium-ion positive electrode material according to any one of claims 3-8.