A manganese-based sodium storage type positive electrode material with a dual-phase structure and a preparation method thereof

Abstract

The application discloses a manganese-based sodium storage type positive electrode material with a dual-phase structure and a preparation method thereof. 0.2 Mn 0.8 O2, has a layered O3 / O'3 dual-phase crystal form. The material is mainly prepared by a solid-phase sintering method, sodium source, lithium source and manganese source powders are uniformly ball milled, tablet molding is first carried out, and high-temperature calcination is then carried out, and the material is a sodium ion battery positive electrode material with a dual-phase structure and high crystallinity. The preparation method of the material is simple, raw material prices are low, and the material is environment-friendly, and the material is expected to be used as a high-stability sodium ion battery positive electrode material.

Description

Technical Field

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

[0002] Sodium-ion batteries (SIBs) have attracted widespread attention from researchers due to their low cost, abundant resources, and energy storage mechanism similar to lithium-ion batteries. For sodium-ion batteries, the cathode material is a key factor determining their electrochemical performance; therefore, the development of cathode materials is crucial for the commercialization of sodium-ion batteries. Currently, extensively studied cathode materials for sodium-ion batteries include layered transition metal oxides, Prussian blue compounds, polyanionic compounds, and organic compounds. Among these, sodium-ion layered metal oxides have been widely studied due to their relative ease of preparation, adjustable voltage range, and high specific capacity. Traditional transition metal layered materials, such as Na... x In TMO2 (x<1, TM represents transition metal ions), only transition metal ion pairs participate in redox reactions during charging and discharging, such as (Mn... 3+ / Mn 4+ (Redox couple). Sodium-rich materials Na... x TMO2 (x>1) differs from this because it can trigger anionic redox reactions (O2) in the transition metal layers. 2- / O n- Sodium-rich manganese-based cathode materials can operate at higher potentials, and the sodium ion insertion / extraction within the structure provides a specific capacity exceeding conventional theoretical values. Therefore, to meet the growing energy storage demands, it is crucial to research inexpensive and high-performance storage cathode materials, and sodium-rich manganese-based substrate materials are among the most promising candidates.

[0003] Although sodium-rich materials offer advantages such as high capacity and high operating potential, two major challenges remain to be addressed: first, maintaining the stability of the layered structure under high-voltage charging conditions is difficult; second, in past research, researchers have attempted to achieve anionic redox reactions in sodium-rich materials using Na+. x The introduction of noble metals such as Ru and Ir into TMO2 materials is not only expensive but also reduces the material's capacity, hindering practical applications. Studies have shown that the presence of a Na-O-Li configuration significantly enhances the anionic redox activity of the material, thus improving its electrochemical performance. Furthermore, the presence of a biphase structure allows it to leverage the advantages of both configurations simultaneously. Therefore, the coexistence of both the Na-O-Li configuration and the biphase structure can effectively improve the material's electrochemical performance. Summary of the Invention

[0004] The purpose of this invention is to provide a manganese-based sodium storage cathode material with high specific capacity and rate capability having a dual-phase structure, and to provide a simple and low-cost preparation method for this material.

[0005] To achieve the above objectives, the chemical formula of the manganese-based sodium-storage cathode material provided by this invention is NaLi. 0.2 Mn 0.8 O2 has an O3 / O'3 dual-phase structure, where the O'3 phase is NaMnO2 and the O3 phase is NaLi. 1 / 3 Mn 2 / 3 In the O2 and O3 phases, Li and Mn elements together form a honeycomb-like superlattice ordered structure within the transition metal layers. Two Li atoms replace two Mn atoms, forming periodically arranged structural units. These repeating structural units constitute the transition metal layers. (NaLi) 1 / 3 Mn 2 / 3 O2 forms a Li-O-Na configuration.

[0006] The preparation method of the manganese-based sodium-storage cathode material of the present invention is as follows: according to NaLi 0.2 Mn 0.8 The stoichiometric ratio of O2 is used to mix Na2O2, Li2O, Mn2O3 and MnO2, grind for 1 to 2 hours, compress into a sheet, and then calcine at 400 to 800°C for 8 to 30 hours under an argon atmosphere. The calcined product is then crushed to obtain a high-capacity manganese-based sodium-storage cathode material with a dual-phase structure.

[0007] In the above-mentioned method for preparing sodium-ion battery cathode material with a dual-phase structure, Na2O2, Li2O, Mn2O3 and MnO2 are preferably mixed in a molar ratio of 1:0.2:0.4:0.8, ground for 1-2 hours, pressed into sheets, calcined at 600-700°C for 8-12 hours under an argon atmosphere, cooled to 300°C and removed, and the calcined product is ground and pulverized to obtain a high-capacity manganese-based sodium-storage cathode material with a dual-phase structure.

[0008] In the above-mentioned method for preparing sodium-ion battery cathode materials with a dual-phase structure, the preferred pressing pressure is 10-20 MPa.

[0009] In the above-mentioned method for preparing sodium-ion battery cathode materials with a dual-phase structure, the preferred calcination heating rate is 5–10 °C / min. -1 .

[0010] In the above-mentioned method for preparing sodium-ion battery cathode materials with a dual-phase structure, the preferred cooling rate is 3–5 °C / min. -1 .

[0011] The beneficial effects of this invention are as follows:

[0012] 1. The material of this invention has a two-phase structure, wherein one phase is NaMnO2(O'3) with a redox couple of (Mn... 3+ / Mn 4 + This provides the material with cationic redox capacity, but due to Mn 3+ The presence of the Jahn-Teller effect causes structural distortion and poor stability in this phase during cycling; the other phase is NaLi. 1 / 3 Mn 2 / 3 O2 (O3 phase) has two advantages. Firstly, Li and Mn elements in the material can jointly form a "honeycomb" superlattice ordered structure within the transition metal layers. This is a regular hexagonal structure where two Li atoms replace two Mn atoms, forming periodically arranged structural units. These repeating structural units constitute the transition metal layers, and this arrangement greatly improves the stability of the crystal structure. Secondly, NaLi 1 / 3 Mn 2 / 3 The presence of O2 can form a Li-O-Na configuration, increasing the number of unhybridized O2p electrons, thereby enabling anionic redox reactions and significantly improving the material's capacity. Due to the presence of this dual-phase structure, the material can trigger anionic / cationic redox reactions, simultaneously improving both its capacity and structural stability.

[0013] 2. This invention prepares NaLi using a one-step solid-state sintering method involving Na2O2, Li2O, Mn2O3, and MnO2. 0.2 Mn 0.8 O2 has a short preparation cycle, simple method, low raw material price, and is environmentally friendly, making it a promising candidate as a cathode material for highly stable sodium-ion batteries. Attached Figure Description

[0014] Figure 1 The manganese-based sodium-storage cathode material NaLi prepared in Examples 1-6 0.2 Mn 0.8 X-ray diffraction pattern of O2.

[0015] Figure 2 The manganese-based sodium-storage cathode material NaLi prepared in Examples 1-6 0.2 Mn 0.8 The peak intensity ratio and peak area ratio of O3(104) and O'3(111) of O2.

[0016] Figure 3 This is the manganese-based sodium-storage cathode material NaLi prepared in Example 4. 0.2 Mn 0.8 Transmission electron microscopy image (a) and fast Fourier transform image (b) of O2.

[0017] Figure 4 The manganese-based sodium-storage cathode material NaLi prepared in Examples 1-6 0.2 Mn 0.8 Charge and discharge curves of O2.

[0018] Figure 5 This is the manganese-based sodium-storage cathode material NaLi prepared in Example 4. 0.2 Mn 0.8 The rate performance curve of O2.

[0019] Figure 6 This is the manganese-based sodium-storage cathode material NaLi prepared in Example 4. 0.2 Mn 0.8 Cyclic performance curve of O2. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to these examples.

[0021] Example 1

[0022] 1.050 g (13.46 mmol) Na₂O₂, 0.077 g (2.57 mmol) Li₂O, 0.810 g (5.13 mmol) Mn₂O₃, and 0.890 g (10.23 mmol) MnO₂ powder were placed in an agate mortar and ground for 1 h. 250 mg of the ground sample was pressed into sheets under 20 MPa pressure and calcined in a tube furnace under an argon atmosphere at a heating rate of 10 °C / min to 400 °C for 10 h. The sheets were then cooled to 300 °C at a cooling rate of 3 °C / min, quickly removed, and placed in an argon-filled glove box to obtain the manganese-based sodium-storage cathode material NaLi. 0.2 Mn 0.8 O2.

[0023] Example 2

[0024] In this embodiment, the temperature was raised to 500°C in a tube furnace under an argon atmosphere at a heating rate of 10°C / min, and then calcined at a constant temperature for 10 hours. Other steps were the same as in Example 1, resulting in the manganese-based sodium-storage cathode material NaLi. 0.2 Mn 0.8 O2.

[0025] Example 3

[0026] In this embodiment, the temperature was raised to 550°C in a tube furnace under an argon atmosphere at a heating rate of 10°C / min, and then calcined at a constant temperature for 10 hours. Other steps were the same as in Example 1, resulting in the manganese-based sodium-storage cathode material NaLi. 0.2 Mn 0.8 O2.

[0027] Example 4

[0028] In this embodiment, the temperature was raised to 600°C in a tube furnace under an argon atmosphere at a heating rate of 10°C / min, and then calcined at a constant temperature for 10 hours. Other steps were the same as in Example 1, resulting in the manganese-based sodium-storage cathode material NaLi. 0.2 Mn 0.8 O2.

[0029] Example 5

[0030] In this embodiment, the temperature was raised to 700°C in a tube furnace under an argon atmosphere at a heating rate of 10°C / min, and then calcined at a constant temperature for 10 hours. Other steps were the same as in Example 1, resulting in the manganese-based sodium-storage cathode material NaLi. 0.2 Mn 0.8 O2.

[0031] Example 6

[0032] In this embodiment, the temperature was raised to 800°C in a tube furnace under an argon atmosphere at a heating rate of 10°C / min, and then calcined at a constant temperature for 10 hours. Other steps were the same as in Example 1, resulting in the manganese-based sodium-storage cathode material NaLi. 0.2 Mn 0.8 O2.

[0033] Figure 1 The manganese-based sodium-storage cathode material NaLi prepared in Examples 1-6 0.2 Mn 0.8 The X-ray diffraction patterns of O2, compared with standard cards (PDF#73-0156 and PDF#54-0887), show that the X-ray diffraction peaks of each prepared material correspond one-to-one with the standard cards, with no impurity peaks appearing, and the materials exhibit high crystallinity; simultaneously, a characteristic peak of a superlattice ordered structure appears at 21°. The XRD patterns demonstrate that this invention has prepared a dual-phase manganese-based material with a superlattice ordered structure.

[0034] Figure 2 Table 1 shows the manganese-based sodium-storage cathode materials NaLi prepared in Examples 1-6. 0.2 Mn 0.8 The peak intensity ratio and peak area ratio of O3(104) and O'3(111) of O2. Combined with... Figure 2 As can be seen from Table 1, I(104) / I(111) and A(104) / A(111) change continuously with the change of preparation temperature. This indicates that the content of O3 phase in the material changes with temperature, and is close to 4:1 to 3:1 at 550 to 700℃.

[0035] Figure 3 This is the manganese-based sodium-storage cathode material NaLi prepared in Example 4.0.2 Mn 0.8 Transmission electron microscopy (TEM) image (a) and fast Fourier transform (FFT) image (b) of O2. The TEM image reveals an O3 / O'3 dual-phase structure with a clearly visible interface. The FFT image identifies hexagonal lattice points belonging to O3 and monoclinic lattice points belonging to O'3, corroborating the TEM results. The combination of these two findings explains the prepared material, NaLi. 0.2 Mn 0.8 O2 belongs to the O3 / O'3 dual-phase material.

[0036] The manganese-based sodium-storage cathode material NaLi prepared in Examples 1-6 above 0.2 Mn 0.8 The performance of O2 was tested using the following method: NaLi was weighed in a glove box at a mass ratio of 8:1:1. 0.2 Mn 0.8 O2, conductive agent acetylene black, and binder polyvinylidene fluoride were placed in a mortar and ground evenly for 1 hour to ensure uniform mixing. 1–2 mL of N-methylpyrrolidone was added to the ground mixture, and grinding continued for 30 minutes to prepare a slurry. The slurry was then evenly coated onto a smooth aluminum foil wiped clean with anhydrous ethanol, with a coating thickness of 0.15–0.2 μm. The coated electrode was placed on a heating plate and dried at 80°C for 10 hours. The electrode was cut into 16 mm diameter circular sheets using a cutting machine and pressed into sheets at 8 MPa using a pressing machine, and the weight of the sheets was measured. Using the dried electrode as the positive electrode and the sodium sheet as the negative electrode, a 2032 coin cell was assembled. The electrolyte was a 1 mol NaClO4 (PC) aqueous solution, and the battery sealing pressure was 13.9 t. After assembly, the battery was left to stand in a glove box for 10 hours. The assembled battery was subjected to constant current charge-discharge testing on a battery testing system, where the current density was set according to different experimental designs and the voltage window was 1.5 to 4.5V.

[0037] Figure 4 The manganese-based sodium-storage cathode material NaLi prepared in Examples 1-6 0.2 Mn 0.8 Table 2 shows the charge-discharge curves of O2, comparing the first-cycle charging capacity and the charging capacity below 3.6V for these six materials. Combining these two figures, it can be seen that all six materials exhibit a long plateau around 3.6V during the first charge, indicating the successful triggering of the anion redox reaction. The capacity below 3.6V is consistently Mn. 3+ / Mn 4+ The content was provided, and the proportions were relatively high at 600℃ and 700℃, at 39.5% and 28.2%, respectively. This demonstrates the material's ability to undergo co-oxidation and reduction by anions and cations.

[0038] Figure 5This is the manganese-based sodium-storage cathode material NaLi prepared in Example 4. 0.2 Mn 0.8 The rate performance curve of O2, as shown in the figure, indicates that the material exhibits performance in the range of 50–200 mA g. -1 At the given current density, the specific capacity decay during the first five charge-discharge cycles is minimal, remaining at 150 mAh g. -1 The figure of around 100 indicates that the addition of lithium can improve the rate performance of the material.

[0039] Figure 6 This is the manganese-based sodium-storage cathode material NaLi prepared in Example 4. 0.2 Mn 0.8 The cycling stability curve of O2 shows that the material operates at a working voltage of 2.0–4.5 V and a capacity of 200 mAh g. -1 It exhibits better cycling stability at lower current densities, with a capacity retention of 60.1% after 100 cycles, indicating that lithium substitution significantly improves the cycling stability of the material.

[0040] Table 1. Materials NaLi prepared in Examples 1-6 0.2 Mn 0.8 The peak intensity ratio and peak area ratio of O3(104) and O'3(111) of O2

[0041]

[0042] Table 2. Materials NaLi prepared in Examples 1-6 0.2 Mn 0.8 Comparison of O2's first-charge capacity and charging capacity below 3.6V

[0043]

Claims

1. A method for preparing a manganese-based sodium-storage cathode material with a dual-phase structure, characterized in that: The chemical formula of this material is NaLi 0.2 Mn 0.8 O2 has an O3 / O'3 dual-phase structure, where the O'3 phase is NaMnO2 and the O3 phase is NaLi. 1 / 3 Mn 2 / 3 In the O2 and O3 phases, Li and Mn elements together form a honeycomb-like superlattice ordered structure within the transition metal layers. Two Li atoms replace two Mn atoms, forming periodically arranged structural units. These repeating structural units constitute the transition metal layers. (NaLi) 1 / 3 Mn 2 / 3 O2 forms a Li-O-Na configuration; The preparation method of the manganese-based sodium-storage cathode material with a dual-phase structure is as follows: according to NaLi 0.2 Mn 0.8 The stoichiometric ratio of O2 is used to mix Na2O2, Li2O, Mn2O3 and MnO2, grind for 1-2 h, compress into a sheet, and then calcine at 400-800 °C for 8-30 h under an argon atmosphere. The calcined product is then crushed to obtain a high-capacity manganese-based sodium-storage cathode material with a two-phase structure.

2. The method for preparing the manganese-based sodium-storage cathode material with a dual-phase structure according to claim 1, characterized in that: Na2O2, Li2O, Mn2O3 and MnO2 were mixed in a molar ratio of 1:0.2:0.4:0.8, ground for 1-2 h, pressed into tablets, and then calcined at 600-700 °C for 8-12 h under an argon atmosphere. After cooling to 300 °C, the calcined product was removed and ground to obtain a high-capacity manganese-based sodium-storage cathode material with a two-phase structure.

3. The method for preparing a manganese-based sodium-storage cathode material with a dual-phase structure according to claim 1 or 2, characterized in that: The pressure of the tablet is 10-20 MPa.

4. The method for preparing a manganese-based sodium-storage cathode material with a dual-phase structure according to claim 1 or 2, characterized in that: The heating rate for calcination is 5–10 °C / min. -1 .

5. The method for preparing the manganese-based sodium-storage cathode material with a dual-phase structure according to claim 2, characterized in that: The cooling rate is 3–5 °C / min. -1 .

6. A manganese-based sodium-storage cathode material with a dual-phase structure, characterized in that: It is prepared by the preparation method described in claim 1.

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