A two-site doped layered oxide cathode and sodium-ion battery applications
By doping rare earth element yttrium and transition metal zirconium into the cathode material of sodium-ion batteries, the structural stability and air stability problems of O3-type layered oxides during charge and discharge processes were solved, achieving high specific capacity and excellent cycle performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING INST OF TECH
- Filing Date
- 2026-05-18
- Publication Date
- 2026-07-31
AI Technical Summary
O3-type layered oxide sodium-ion battery cathode materials are prone to interlayer slip and irreversible phase transitions during charge and discharge, leading to decreased structural stability and reduced cycle performance. At the same time, their surface is prone to side reactions with air, which limits their application.
The sodium layer and the transition metal layer are doped with rare earth element yttrium (Y) and transition metal element zirconium (Zr), respectively, to form a chemical structure of [Na1-3xYx]TM(1-4y)/3ZryO2. This structure is prepared by high-temperature solid-state method, which suppresses interlayer slip and enhances air stability.
It improves electrochemical cycle stability and air stability, extends the cycle life of the material and battery performance, and maintains high specific capacity.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of sodium-ion battery cathode material technology, specifically relating to a layered oxide cathode material for sodium-ion batteries in which rare earth element yttrium (Y) and transition metal element zirconium (Zr) are doped at two sites in the sodium layer and the transition metal layer, respectively, and the preparation method thereof. Background Technology
[0002] With the widespread application of lithium-ion batteries in digital 3C products, electric vehicles, and other energy storage devices, the limited lithium resource reserves and high raw material costs have gradually become important factors restricting their further development. In contrast, sodium resources are abundant, widely distributed, and inexpensive. Moreover, sodium-ion batteries have similar working principles and structures to lithium-ion batteries, and are therefore considered a highly promising supplementary alternative to lithium-ion batteries, particularly suitable for large-scale energy storage.
[0003] In sodium-ion batteries, the cathode material is a key factor determining battery performance and cost. Among them, layered transition metal oxides are considered the most promising cathode materials for industrialization due to their advantages such as high specific capacity, simple preparation process, and low cost. However, O3-type layered oxides are prone to interlayer slippage and irreversible phase transitions during charge and discharge due to repeated insertion / extraction of sodium ions, leading to decreased structural stability and reduced cycle performance. Simultaneously, their surface is susceptible to side reactions with air, causing deterioration of surface stability and loss of active materials, thus limiting their further application. Therefore, for high-capacity sodium-ion cathode materials, represented by O3-type sodium-ion layered oxide cathode materials, improving their structural stability and air stability during electrochemical processes is crucial for their large-scale industrial application. Summary of the Invention
[0004] The purpose of this invention is to address the aforementioned defects and deficiencies by providing a sodium-ion battery layered oxide in which rare earth element yttrium (Y) and transition metal element zirconium (Zr) are doped at dual sites in the sodium layer and the transition metal layer, respectively. While maintaining the high specific capacity of existing O3-type sodium-ion layered oxides, this invention improves the electrochemical cycle stability and air stability of the sodium-ion battery cathode material.
[0005] Another objective of this invention is to provide a method for preparing a layered oxide cathode material for sodium-ion batteries by doping rare earth element yttrium (Y) and transition metal element zirconium (Zr) at two sites in the sodium layer and the TM layer, respectively.
[0006] Another object of the present invention is to provide a sodium-ion secondary battery comprising the preparation method described above.
[0007] The present invention achieves the above objectives through the following technical solutions:
[0008] According to a first aspect of the present invention, a sodium-ion battery cathode material is provided, wherein the general chemical formula of the sodium-ion battery cathode material is [Na 1-3x Y x ]TM (1-4y) / 3 Zr y O2, wherein the rare earth element yttrium (Y) is the sodium layer dopant, and the transition metal element zirconium (Zr) is the transition metal layer dopant. Other transition metals (TM) in the chemical formula are selected from one or more combinations of Ni, Co, Mn, Fe, Cu, Ti, Mg, Al, Sn, Li, Cr, V, Zn, and Mo; the sum of the oxidation states of the TM is +3. Each TM element forms an octahedral structure with its six nearest-neighbor oxygen atoms, and multiple octahedral structures are arranged with shared edges to form a transition metal layer; Na + Located between every two transition metal layers, forming a space group Layered oxides.
[0009] Preferably, the TM comprises Ni, Fe, and Mn; the rare earth element Y and the transition metal element Zr are respectively doped in the sodium layer and the transition metal layer of the sodium-ion battery layered oxide [Na]. 1-3x Y x ]TM (1-4y) / 3 Zr y O2 (0) <x<0.1, 0<y<0.1)。
[0010] According to a second aspect of the present invention, embodiments of the present invention provide a method for preparing a layered oxide for sodium-ion batteries by doping rare earth element Y and transition metal element Zr in a sodium layer and a transition metal layer, as described in the first aspect, comprising a high-temperature solid-state method I and a high-temperature solid-state method II, the specific methods being as follows:
[0011] High-temperature solid-state method I:
[0012] According to the [Na] 1-3x Y x ]TM (1-4y) / 3 Zr y The stoichiometric ratio of O2 is used to ball-mill and mix sodium, yttrium, zirconium and other transition metal sources in appropriate proportions, compress the mixture into tablets, calcine it at high temperature in air, cool it to room temperature and crush it to obtain the product.
[0013] Furthermore, the sodium source is one or more of sodium carbonate, sodium acetate, sodium hydroxide, sodium nitrate, sodium oxalate, and sodium hydrogen oxalate;
[0014] Preferably, the sodium source is sodium carbonate.
[0015] Furthermore, the yttrium source, zirconium source, and other transition metal elements are one or more of oxides, acetates, sulfates, and nitrates;
[0016] Preferably, the yttrium source, zirconium source, and other transition metal elements are derived from oxides.
[0017] Furthermore, the ball milling time is 4–12 h, the rotation speed is 200–600 r / min, the high-temperature calcination heating rate is 2–10 °C / min, the calcination temperature is 750–1050 °C, and the calcination time is 10–20 h;
[0018] Preferably, the ball milling time is 10 hours, the rotation speed is 300 r / min, the high-temperature calcination heating rate is 5℃ / min, the calcination temperature is 900℃, and the calcination time is 15 hours.
[0019] High-Temperature Solid-State Method II:
[0020] The layered oxide precursor powder, sodium source, yttrium source and zirconium source are mixed evenly to obtain a mixed powder, which is then calcined in air and cooled to room temperature to obtain the product.
[0021] Furthermore, the sodium source is one or more of sodium carbonate, sodium acetate, sodium hydroxide, sodium nitrate, sodium oxalate, and sodium hydrogen oxalate;
[0022] Preferably, the sodium source is sodium carbonate.
[0023] Furthermore, the layered oxide precursor powder is one or more of TM(OH)2, TMCO3, and TMC2O4;
[0024] Preferably, the layered oxide precursor powder is TM(OH)2.
[0025] Furthermore, the yttrium source and the zirconium source are one or more of the following: oxides, acetates, sulfates, and nitrates of yttrium and zirconium.
[0026] Preferably, the yttrium source and the zirconium source are oxides of yttrium and zirconium, respectively.
[0027] Furthermore, the mixing method includes grinding, mechanical mixing, and stirring; the high-temperature calcination heating rate is 2–10 °C / min; the calcination temperature is 700–1000 °C; and the calcination time is 10–20 h.
[0028] Preferably, the mixing method is stirring and mixing, the high-temperature calcination heating rate is 5℃ / min, the calcination temperature is 880℃, and the calcination time is 12h.
[0029] A sodium-ion secondary battery according to a third aspect of the present invention includes any of the sodium-ion battery cathode materials described above.
[0030] The advantages of this invention compared to existing technologies are as follows:
[0031] (1) Y and Zr elements together act as interlayer support, suppressing interlayer slip during the electrochemical process of the material, reducing lattice distortion and irreversible phase transition, thereby improving cycle stability.
[0032] (2) Element Y enhances the interaction between sodium cations and oxygen, reduces the interlayer spacing of sodium layers, and thus improves air stability. Attached Figure Description
[0033] Figure 1 The image shows the X-ray diffraction (XRD) pattern of the cathode material prepared in Example 1.
[0034] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the cathode material prepared in Comparative Example 1.
[0035] Figure 3 The image shows the X-ray diffraction (XRD) pattern of the cathode material prepared in Example 4.
[0036] Figure 4 The image shows the energy dispersive spectroscopy (EDS) spectrum of the cathode material prepared in Example 1.
[0037] Figure 5 This is a charge-discharge curve of the battery assembled in Example 1.
[0038] Figure 6 The charge-discharge curves are for the battery assembled in Comparative Example 1.
[0039] Figure 7 The graph shows the electrochemical cycling performance of the battery assembled in Example 1.
[0040] Figure 8 The graph shows the electrochemical cycling performance of the battery assembled in Comparative Example 1.
[0041] Figure 9 The graph shows the electrochemical cycling performance of the battery assembled in Example 4.
[0042] Figure 10 The graph shows the electrochemical cycling performance of the battery assembled in Example 5.
[0043] Figure 11 The graph shows the electrochemical cycling performance of the battery assembled in Comparative Example 2. Detailed Implementation
[0044] The related technologies of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0045] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0046] Example 1
[0047] According to the high-temperature solid-state method I, based on Na 0.97 Y 0.01 (Ni 0.33 Fe 0.33 Mn 0.33 ) 0.973 Zr 0.02 The stoichiometric ratio of O2 was used to ball-mill sodium carbonate, yttrium oxide, zirconium dioxide, nickel oxide, ferric oxide, and manganese oxide in anhydrous ethanol medium at a speed of 300 r / min for 10 h. The mixture was then filtered, dried, and pressed into tablets. The tablets were then heated to 900 °C in air at a heating rate of 5 °C / min and calcined for 15 h. The tablets were then cooled to room temperature and crushed to obtain the product. Figure 1 for Na 0.97 Y 0.01 (Ni 0.33 Fe 0.33 Mn 0.33 ) 0.973 Zr 0.02 XRD pattern of O2. All diffraction peaks in the XRD pattern can be well assigned to the hexagonal crystal system. The space group indicates that the material synthesized in Example 1 has a pure O3 phase layered structure, with Y and Zr elements completely incorporated into the crystal lattice. Figure 4 for Na 0.97 Y 0.01 (Ni 0.33 Fe 0.33 Mn 0.33 ) 0.973 Zr 0.02 The EDS spectrum of O2 showed that all elements were uniformly distributed, which verified the doping results of XRD.
[0048] The sodium-ion battery layered oxide cathode material prepared above, doped with the rare earth element yttrium (Y) and the transition metal element zirconium (Zr) at two sites in the sodium layer and the transition metal layer respectively, is used in the preparation of sodium-ion batteries.
[0049] The specific steps are as follows: Prepare the Na... 0.97 Y 0.01 (Ni 0.33 Fe 0.33 Mn 0.33 ) 0.973 Zr 0.02O2, Super-P, and the binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 80:10:10. Then, N-methylpyrrolidone (NMP) organic solvent was added, and the mixture was stirred at high speed to form a slurry by adjusting the solid content of the electrode material. The slurry was then uniformly coated onto a thin aluminum foil and placed in a vacuum drying oven. It was then dried overnight at 100°C under vacuum conditions and cut into round pieces for use as positive electrodes.
[0050] The coin cell assembly was performed in an argon-atmospheric glove box, using metallic sodium as the counter electrode and a NaClO4 / EC:PC (v / v = 1:1) + 5% FEC solution as the electrolyte, to assemble CR2032 coin cells. Finally, charge-discharge tests were conducted within a voltage window of 2.0–4.0 V to obtain its electrochemical performance. Its charge-discharge curves and cycle performance are shown below. Figure 5 , Figure 7 As shown, the initial charge specific capacity is 122 mAh / g, the discharge specific capacity is 117 mAh / g, and the initial efficiency is 95.90%. During 200 cycles, the discharge specific capacity decays to 80 mAh / g, and the coulombic efficiency remains stable at nearly 100%.
[0051] Example 2
[0052] Na was prepared according to the high-temperature solid-state method I. 0.985 Y 0.005 (Ni 0.33 Fe 0.33 Mn 0.33 ) 0.987 Zr 0.01 O2. The only difference between this implementation method and Example 1 is the doping amount of rare earth element Y and transition metal element Zr.
[0053] Example 3
[0054] Na was prepared according to the high-temperature solid-state method I. 0.94 Y 0.02 (Ni 0.33 Fe 0.33 Mn 0.33 ) 0.947 Zr 0.04 O2. The only difference between this implementation method and Example 1 is the doping amount of rare earth element Y and transition metal element Zr.
[0055] Comparative Example 1
[0056] NaNi was prepared according to the high-temperature solid-state method I. 0.33 Fe 0.33 Mn 0.33 O2. All diffraction peaks in the XRD pattern can be well assigned to the hexagonal crystal system. The space group indicates that the material synthesized in Comparative Example 1 has a pure O3 phase layered structure. The only difference between this specific implementation and Example 1 is that the doping levels of rare earth element Y and transition metal element Zr are 0. Figure 2 NaNi 0.33 Fe 0.33 Mn 0.33 The XRD pattern of O2, its charge-discharge curves, and cycle performance are as follows: Figure 6 , Figure 8 As shown, the initial charge specific capacity is 127 mAh / g, the discharge specific capacity is 117 mAh / g, and the initial efficiency is 92.13%. During 200 cycles, the discharge specific capacity decays to 61 mAh / g, and the coulombic efficiency remains stable at nearly 100%.
[0057] Example 4
[0058] According to the high-temperature solid-state method II, based on Na 0.97 Y 0.01 (Ni 0.33 Fe 0.33 Mn 0.33 ) 0.973 Zr 0.02 The stoichiometric ratio of O2 is used to adjust the proportions of sodium carbonate, yttrium trioxide, zirconium dioxide, and Ni. 0.33 Fe 0.33 Mn 0.33 (OH)₂ was magnetically stirred at 500 r / min for 6 h in anhydrous ethanol medium, mixed thoroughly, filtered, dried, and then calcined in air at a heating rate of 5 °C / min to 880 °C for 12 h. The product was then cooled to room temperature. All diffraction peaks in the XRD pattern were well assigned to the hexagonal crystal system. The space group indicates that the material synthesized in Example 4 has a pure O3 phase layered structure.
[0059] The specific implementation method differs from Example 1 only in the material preparation method. Figure 3 Na prepared by high-temperature solid-state method II 0.97 Y 0.01 (Ni 0.33 Fe 0.33 Mn 0.33 ) 0.973 Zr 0.02 The XRD pattern of O2 shows its cycling performance as follows: Figure 9 As shown, during 200 cycles, the discharge specific capacity decayed to 81 mAh / g, while the coulombic efficiency remained stable at nearly 100%.
[0060] Example 5
[0061] Na after one week of air exposure 0.97 Y0.01 (Ni 0.33 Fe 0.33 Mn 0.33 ) 0.973 Zr 0.02 O2 is used in the preparation of sodium-ion batteries. The specific preparation steps are the same as in Example 1, Na... 0.97 Y 0.01 (Ni 0.33 Fe 0.33 Mn 0.33 ) 0.973 Zr 0.02 Electrochemical cycling performance of O2 after one week of air exposure is as follows: Figure 10 As shown, during 200 cycles, the discharge specific capacity decayed to 69 mAh / g, while the coulombic efficiency remained stable at nearly 100%.
[0062] Comparative Example 2
[0063] NaNi after being exposed to air for a week 0.33 Fe 0.33 Mn 0.33 O2 was used in the preparation of sodium-ion batteries. The specific preparation steps were the same as in Comparative Example 1, NaNi 0.33 Fe 0.33 Mn 0.33 Electrochemical cycling performance of O2 after one week of air exposure is as follows: Figure 11 As shown, the discharge specific capacity decayed to 57 mAh / g, and the coulombic efficiency fluctuated significantly in some cycles.
[0064] Figure 1-3 XRD patterns of samples prepared by different methods are shown. All samples exhibit clear diffraction peaks characteristic of layered oxides, indicating that the materials have successfully formed the target crystal structure. The double-doped samples did not show obvious impurity phase peaks, indicating that Y and Zr doping did not destroy the main structure. Figure 4 The image shows the EDS elemental distribution of Example 1. Ni, Fe, Mn, Na, and doping elements Y and Zr are uniformly distributed inside the particles, proving that the dual doping elements were successfully introduced and have good dispersion. Figure 5-6 The results show that, compared with Comparative Example 1, the battery assembled in Example 1 has a higher discharge specific capacity and smaller charge-discharge polarization, indicating that Y and Zr dual-site doping helps to improve electrochemical reaction kinetics and structural stability. Figure 7-11Regarding the cycling performance results, Examples 1 and 4 both exhibited superior cycling stability compared to Comparative Example 1. Furthermore, after being air-conditioned for one week, Example 5 showed significantly better capacity retention than Comparative Example 2. In summary, this invention, by introducing the rare earth element Y into the sodium layer and the transition metal element Zr into the transition metal layer, achieves the following: on the one hand, while maintaining a high specific capacity, it reduces the spacing between the O-Na-O layers, thereby improving the material's air stability; on the other hand, relying on the supporting effects of Y and Zr in the sodium layer and transition metal layer, respectively, it suppresses interlayer slippage during electrochemical cycling, delays the O3-P3 phase transition, and enables the material to achieve excellent cycling stability.
[0065] The above descriptions are merely a few embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the protection scope of the present invention.
Claims
1. A layered oxide cathode material for sodium-ion batteries with dual-site doping, characterized in that, The general chemical formula of the layered oxide cathode material, in which rare earth element Y is doped in the sodium layer and transition metal elements are doped in the TM layer, is [Na]. 1-3x Y x ]TM (1-4y) / 3 Zr y O2 (0 < x < 0.1, 0 < y < 0.1), wherein the rare earth element yttrium (Y) is the sodium layer dopant, the transition metal element zirconium (Zr) is the transition metal layer dopant, and other transition metals (TM) in the chemical formula are selected from one or more combinations of Ni, Co, Mn, Fe, Cu, Ti, Mg, Al, Sn, Li, Cr, V, Zn, and Mo. Each TM element forms an octahedral structure with its six nearest-neighbor oxygen atoms, and multiple octahedral structures are arranged with shared edges to form the transition metal layer; Na + Located between every two transition metal layers, forming a space group Layered oxides.
2. A method for preparing the dual-site doped layered oxide cathode material for sodium-ion batteries according to claim 1, characterized in that, High temperature solid phase method I: according to the [Na 1-3x Y x ]TM (1-4y) / 3 Zr y O2stoichiometric ratio, the corresponding proportion of sodium source, yttrium source, zirconium source and other transition metal source ball milling, tabletting, then high temperature calcination in air, cooling to room temperature for crushing to obtain the product.
3. The method for preparing the dual-site doped layered oxide cathode material for sodium-ion batteries according to claim 2, characterized in that, The sodium source is one or more of sodium carbonate, sodium acetate, sodium hydroxide, sodium nitrate, sodium oxalate, and sodium hydrogen oxalate; the yttrium source, zirconium source, and other transition metal sources are one or more of oxides, acetates, sulfates, and nitrates.
4. The method for preparing the dual-site doped layered oxide cathode material for sodium-ion batteries according to claim 2, characterized in that, The ball milling time is 4–12 h, the rotation speed is 200–600 r / min, the high-temperature calcination heating rate is 2–10 °C / min, the calcination temperature is 750–1050 °C, and the calcination time is 10–20 h.
5. A method for preparing the dual-site doped layered oxide cathode material for sodium-ion batteries according to claim 1, characterized in that, High-temperature solid-state method II: The layered oxide precursor powder, sodium source, yttrium source and zirconium source are mixed evenly to obtain a mixed powder, which is then calcined in air and cooled to room temperature to obtain the product.
6. The method for preparing the dual-site doped layered oxide cathode material for sodium-ion batteries according to claim 5, characterized in that, The sodium source is one or more of sodium carbonate, sodium acetate, sodium hydroxide, sodium nitrate, sodium oxalate, and sodium hydrogen oxalate; the layered oxide precursor powder is one or more of TM(OH)2, TMCO3, and TMC2O4; the yttrium source and zirconium source are one or more of yttrium oxides, zirconium acetates, sulfates, and nitrates, respectively.
7. The method for preparing the dual-site doped layered oxide cathode material for sodium-ion batteries according to claim 5, characterized in that, The mixing method includes grinding, mechanical mixing, and stirring. The high-temperature calcination heating rate is 2-10℃ / min, the calcination temperature is 700-1000℃, and the calcination time is 10-20h.
8. The dual-site doped layered oxide cathode material for sodium-ion batteries according to claim 1, characterized in that, The material is a positive electrode active material used in sodium-ion secondary batteries.
9. A positive electrode sheet for a sodium-ion secondary battery, characterized in that, The positive electrode comprises: a current collector, a conductive additive and a binder coated on the current collector, and the dual-site doped sodium-ion battery layered oxide positive electrode material as described in claim 8.
10. A sodium-ion secondary battery, characterized in that... It contains the cathode material as described in any one of claims 1 to 9.