High-capacity sodium ion battery positive electrode material based on P2-O3 composite phase as well as preparation method and application of high-capacity sodium ion battery positive electrode material

Abstract

The invention belongs to the technical field of electrochemical energy storage materials, and discloses a high-capacity sodium ion battery positive electrode material based on a P2-O3 composite phase and a preparation method and application thereof. The chemical general formula of the positive electrode material is Na [mu] Li [v] Mg [gamma] Ni [x] Mn [z] TMyO2, wherein [mu] is greater than or equal to 0.75 and less than or equal to 0.85, [v] is greater than or equal to 0.05 and less than or equal to 0.15, [gamma] is greater than or equal to 0.01 and less than or equal to 0.10, x is greater than or equal to 0.20 and less than or equal to 0.30, z is greater than or equal to 0.55 and less than or equal to 0.70, y is greater than or equal to 0.005 and less than or equal to 0.05, and [v] + [gamma] + x + z + y And TM is a combination of at least two elements selected from 3d, 4d and 5d transition metal elements and / or lanthanide series metal elements. The material has a composite crystal structure in which a P2 phase and an O3 phase coexist. The high-capacity sodium-ion battery positive electrode material based on the P2-O3 composite phase has relatively high specific capacity and good cycling stability, and can be used for a sodium-ion battery.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage materials technology, and specifically relates to a high-capacity sodium-ion battery cathode material based on the synergistic effect of multiple components of sodium-lithium-magnesium-nickel-manganese-transition metals, a P2-O3 composite phase, its preparation method, and its application. Background Technology

[0002] With the global energy structure transformation, efficient, safe, and low-cost energy storage technologies have become a key bottleneck restricting the large-scale utilization of renewable energy. While lithium-ion batteries have achieved great success in portable electronic devices and electric vehicles, the uneven geographical distribution of lithium resources and their continuously rising costs severely limit their application prospects in large-scale energy storage. Sodium-ion batteries, due to the abundant and widely distributed nature of sodium resources, their low cost, and their electrochemical mechanism being highly similar to that of lithium-ion batteries, are considered one of the most promising alternative technologies for large-scale energy storage.

[0003] In sodium-ion batteries, the cathode material is the core factor determining the battery's energy density, cycle life, and cost. Currently, the most researched cathode materials for sodium-ion batteries mainly include three systems: Prussian blue analogues, polyanionic compounds, and layered transition metal oxides. Among these, layered oxides (Na...)... x TMO2 (TM is a transition metal) has attracted much attention due to its advantages such as high specific capacity, good ionic conductivity, and simple preparation process. According to Na... + Based on differences in site occupancy and oxygen stacking mechanisms, layered oxides can be mainly classified into types such as P2, P3, O2, and O3. In P2 type materials, Na... + Located at a triangular prism site, it has continuous two-dimensional ion diffusion channels and a low ion diffusion energy barrier, exhibiting excellent rate performance and good air stability, and has become an important research direction for cathode materials of sodium-ion batteries.

[0004] However, P2-type cathode materials still face significant challenges in practical applications. First, when the charging voltage exceeds 4.0 V, the material undergoes complex phase transitions, including the P2-O2 phase transition, interlayer slip, and transition metal migration, leading to crystal structure collapse and rapid capacity decay. Second, the material is prone to Jahn-Teller distortion in a deeply desodium-free state, particularly in Mn. 3+ When present, it causes structural distortion and performance degradation. Furthermore, under high voltage, the side reactions between the electrolyte and electrode materials intensify, significantly increasing the interfacial impedance and further limiting its high-voltage application potential. To improve the structural stability of P2-type materials, researchers have adopted various strategies. Transition metal layer doping is one effective method, among which Li... +Doping has been shown to create "Li-O-TM" local coordination environments, which not only help stabilize the crystal structure but also activate redox reactions of lattice oxygen, providing additional capacity. However, single Li doping is often insufficient to completely suppress structural evolution under high voltage, and excessive Li doping can lead to a decrease in the initial coulombic efficiency. Mg 2+ As an inactive "pillar" element, doping with it can effectively widen the interlayer spacing and suppress interlayer slip during charging and discharging, but its capacity improvement is limited when used alone. Doping with transition metal elements, such as Ti, Cu, Zn, and Ru, can stabilize the crystal framework by adjusting the electronic structure and enhancing metal-oxygen bonding, but the synergistic mechanism of different transition metal elements is still unclear.

[0005] In recent years, anionic redox reactions (especially the redox reaction of lattice oxygen) have provided a new approach to breaking through the capacity limits of cathode materials. In lithium-ion battery lithium-manganese-based cathode materials, specific capacity far exceeding the traditional theoretical limit can be obtained by activating the oxygen redox reaction. This concept has also shown great potential in the field of sodium-ion batteries. However, anionic redox reactions are often accompanied by problems such as irreversible oxygen evolution, voltage hysteresis, and structural degradation, which seriously restrict their practical application. How to achieve stable and reversible anionic redox reactions has become a research challenge and hot topic in this field. On the other hand, single P2 phase or O3 phase materials each have their inherent defects. The P2 phase has high ionic conductivity but low sodium content, while the O3 phase has high sodium content but a large ion migration barrier. Recent studies have shown that constructing P2-O3 composite phase materials can effectively combine the advantages of both. The O3 phase region provides high capacity and structural support, the P2 phase region ensures rapid ion transport, and the interface between the two phases can also suppress global harmful phase transitions. However, the formation of the P2-O3 composite phase is extremely sensitive to sodium content, element ratio, and preparation process. Achieving controllable synthesis and elucidating its synergistic stabilization mechanism remains a major challenge.

[0006] Most existing technologies are limited to single structural control strategies, lacking a systematic understanding of the structure-property relationships among material components, structures, and properties, particularly regarding the synergistic effects of multi-component doping and composite phase structures. Therefore, developing a novel sodium-ion battery cathode material that can controllably construct a P2-O3 composite phase through precise component design and activate stable anion redox reactions is crucial for promoting the application of sodium-ion batteries in large-scale energy storage. This requires understanding the synergistic mechanisms of elements, especially Na, Li, Mg, Ni, Mn, and specific transition metal combinations, at the atomic scale; elucidating the stabilizing effect of composite phase structures on anion redox reactions; establishing scalable fabrication processes; and ultimately achieving an optimal balance between high specific capacity and long-term cycle stability. Summary of the Invention

[0007] To overcome the technical bottlenecks of existing P2-type sodium-ion battery cathode materials, such as structural instability at high voltage, rapid capacity decay, and specific capacity limitation due to transition metal cation redox reactions, the primary objective of this invention is to provide a high-capacity sodium-ion battery cathode material based on a P2-O3 composite phase that can activate stable anion redox reactions. By precisely controlling the elemental ratios and sintering process parameters, the controllable construction of the P2-O3 composite phase structure and the effective regulation of the anion redox reaction are achieved, enabling it to maintain high specific capacity while possessing excellent cycle stability.

[0008] Another objective of this invention is to provide a method for preparing the above-mentioned high-capacity sodium-ion battery cathode material based on the P2-O3 composite phase.

[0009] Another objective of this invention is to provide the application of the above-mentioned high-capacity sodium-ion battery cathode material based on the P2-O3 composite phase.

[0010] The objective of this invention is achieved through the following solution: A high-capacity sodium-ion battery cathode material based on a P2-O3 composite phase, with the general chemical formula: Na μ Li ν Mg γ Ni x Mn z TM y O2, wherein 0.75≤μ≤0.85, 0.05≤ν≤0.15, 0.01≤γ≤0.1, 0.20≤x≤0.30, 0.55≤z≤0.70, 0.005≤y≤0.05, and 0.95≤ν+γ+x+z+y≤1.05; TM is a combination of at least two elements selected from 3d, 4d and 5d transition metals and / or lanthanides.

[0011] The material has a composite crystal structure in which P2 and O3 phases coexist, and its XRD pattern shows discrete P2 (002) and O3 (003) characteristic diffraction peaks in the range of 15°-17° (2θ). The relative contents of the P2 and O3 phases can be controlled within a certain range by adjusting the elemental ratio and sintering process parameters, and the two-phase quantitative data can be obtained by XRD. To avoid redundancy in the figures, the XRD data of each embodiment are summarized in [the table / document / etc.]. Figure 14 Table 1 summarizes the two-phase mass fractions and goodness-of-fit indices for each embodiment. The refined fitting spectrum of the representative sample (Example 1) is shown in [Table 1]. Figure 7 .

[0012] Preferably, the dopant element TM comprises at least one of TM1 and TM2, wherein TM1 is a first transition metal element, and TM2 is a second transition metal element and / or a lanthanide or actinide element, wherein TM1 is selected from at least one of Ti, Fe, Co, Cu, and Zn; and TM2 is selected from at least one of Zr, Nb, Mo, Ru, Rh, Pd, W, La, and Ce. More preferably, the molar ratio of TM1 to TM2 is from 10:1 to 1:2.

[0013] The P2-O3 composite phase formation mechanism: By precisely controlling the sodium content μ within the range of 0.75-0.85, preferably μ=0.80±0.02, ideal thermodynamic and kinetic conditions are provided for the coexistence of the P2 and O3 phases. Within this sodium content range, the material can spontaneously form a composite structure of P2 and O3 phases under the sintering process window. In this composite structure, the O3 phase region provides a high sodium content and a stable structural framework, while the P2 phase region constructs a rapid two-dimensional sodium ion migration channel. The interface between the two phases can effectively suppress global phase transitions and lattice stress accumulation during the charging and discharging process.

[0014] Anion redox activation and stabilization mechanism: The introduction of Li (ν=0.05-0.15) forms a special Li-O-TM local coordination environment in the transition metal layer. Under this environment, the 2s orbital of Li hybridizes with the 2p orbital of O, generating non-bonded O 2p orbitals near the Fermi level. This significantly reduces the oxidation potential of oxygen, preferentially exciting O in the 4.2-4.5V voltage range. 2- →O n- A reversible redox reaction (0 < n < 2) provides an additional capacity contribution. Further preferably, based on the above TM1 / TM2, the selection of the TM element employs a combination strategy, preferably including a combination of transition metal elements with d0 electronic configurations and transition metal elements with d5-d9 electronic configurations. Preferably, the transition metal element with d0 electronic configuration is Ti. 4+ Zr 4+ Or Mo 6+ At least one of the following, wherein the transition metal element having a d5-d8 electronic configuration is Fe. 3+ Co 3+ Cu 2+ Ru 4+ At least one of the following. The former stabilizes the crystal framework by forming strongly covalent TM-O bonds, while the latter regulates the charge transfer process through the hybridization of unpaired d electrons with oxygen p orbitals, together improving the reversibility of anionic redox reactions.

[0015] Structural stabilization and enhancement mechanism: Mg 2+As an inactive dopant element (γ=0.01-0.1), it plays a supporting role in the transition metal layer due to its stable electronic configuration and appropriate ionic radius (0.72 Å). The Mg-O bond energy is as high as 363 kJ / mol, which can effectively suppress interlayer slip and transition metal migration during charge and discharge processes, especially suppressing the harmful transformation from P2 to O2 phase under high voltage.

[0016] The material contains Li in its crystal structure. + The local coordination environment formed by [LiO6] octahedrons and [TMO6] octahedrons is a superlattice structure formed by connecting [LiO6] octahedrons and [TMO6] octahedrons through shared edges or shared vertices.

[0017] A method for preparing the above-mentioned high-capacity sodium-ion battery cathode material based on the P2-O3 composite phase includes the following steps: (1) Raw material pretreatment: Sodium source, lithium source, magnesium source, nickel source, manganese source and TM source are ball-milled respectively to control the average particle size of each raw material within the range of 0.5-5μm; (2) Ball milling: Weigh each raw material according to the stoichiometric ratio of the chemical formula, and mix them by ball milling under a protective atmosphere; (3) Calcination treatment: The mixed precursor is heated and calcined in a pure oxygen atmosphere, and then cooled to room temperature to obtain the cathode material.

[0018] The sodium source mentioned in step (1) is at least one of Na2CO3, NaOH, and NaNO3; The lithium source mentioned in step (1) is at least one of LiOH·H2O, Li2CO3, and Li2C4O4·2H2O; The magnesium source mentioned in step (1) is at least one of MgO, Mg(OH)2, and MgCO3; The nickel source mentioned in step (1) is at least one of NiO and Ni(OH)2; The manganese source mentioned in step (1) is at least one of MnO2, Mn2O3, and Mn3O4; The TM source mentioned in step (1) is an oxide of TM.

[0019] In step (1), the sodium source is weighed according to the target stoichiometric ratio, preferably in excess of 1-5% to compensate for sodium volatilization loss at high temperature.

[0020] The ball milling process described in step (2) involves ball milling at a speed of 300-3000 rpm for 5-15 hours, with a ball-to-material ratio of 10:1 to 30:1.

[0021] The protective atmosphere mentioned in step (2) refers to the process being carried out under an Ar and / or N2 atmosphere.

[0022] The heating and calcination mentioned in step (3) refers to heating to 880℃-1000℃ at a heating rate of 1-5℃ / min and holding for 8-24 hours; more preferably, the atmospheric pressure is maintained at 0.95-1.2 standard atmospheres during the calcination process, and a continuous oxygen supply method is adopted with an oxygen flow rate of 100-200mL / min.

[0023] Preferably, in the heating and calcination of step (3), the temperature is first raised to 500-600℃ at a rate of 1-5℃ / min and held for 2-5 h to remove volatile components, and then the temperature is raised to 880℃-1000℃ at a rate of 1-5℃ / min and held for 8-24 hours; more preferably, in the heating and calcination of step (3), the temperature is first raised to 500-600℃ at a rate of 3-5℃ / min and held for 2-3 h to remove volatile components, and then the temperature is raised to 900-1000℃ (preferably 950℃) at a rate of 1-2℃ / min and held for 8-24 hours to promote the formation of the P2-O3 composite phase.

[0024] The cooling to room temperature mentioned in step (3) refers to cooling to room temperature at a cooling rate of 0.5-7℃ / min (preferably 0.5-2℃ / min) to eliminate internal stress and obtain a thermodynamically stable crystal structure.

[0025] The above-mentioned high-capacity sodium-ion battery cathode material based on the P2-O3 composite phase is applied in sodium-ion batteries. The material of this invention is particularly suitable for the manufacture of sodium-ion batteries with high energy density and long cycle life, and can be widely used in large-scale energy storage systems, electric vehicle power batteries, and portable electronic devices.

[0026] A sodium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode comprises the aforementioned high-capacity sodium-ion battery positive electrode material based on a P2-O3 composite phase, a conductive agent, and a binder, wherein the mass ratio of the positive electrode material, the conductive agent, and the binder is 80-90:5-15:3-10; the compaction density of the positive electrode is 2.8-3.5 g / cm³. 3 .

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects: This invention relates to a high-capacity sodium-ion battery cathode material based on a P2–O3 composite phase. In Examples 1–6, it exhibits high specific capacity and good cycle stability: at a 0.1C rate, the first-cycle charging specific capacity ranges from 152.5 to 225 mAh / g, with Example 1 reaching 225 mAh / g, Example 5 reaching 198.6 mAh / g, and Example 3 reaching 183.5 mAh / g; the first-cycle / first-cycle coulombic efficiency is greater than 80%, with Example 4 achieving an efficiency as high as 87.82%.

[0028] In terms of cycling performance, after 60–100 cycles at a 1C rate, the capacity retention rate remains above 80%. For example, the capacity retention rate of Example 1 after 100 cycles is 80.3%, that of Example 2 after 60 cycles is 81.3%, and that of Example 6 after 100 cycles is 87.0%, indicating that the material of the present invention has good cycling stability. Attached Figure Description

[0029] Figure 1 The voltage-capacity curve is obtained from the first charge-discharge test under 0.1C conditions after the materials of Comparative Example 1 were assembled into a positive electrode / sodium metal half-cell.

[0030] Figure 2 After the materials of Comparative Example 1 were assembled into a positive electrode / sodium metal half-cell, a 200-cycle test was conducted under 1C rate conditions. After the cycle was completed, the battery was disassembled, the positive electrode sheet was removed, and the sample was cleaned and dried with dimethyl carbonate (DMC) before X-ray diffraction (XRD) testing was performed to obtain the spectrum.

[0031] Figure 3 The images show the scanning electron microscope (SEM) morphology comparison of the positive electrode before and after cycling (after being cleaned and dried by DMC) of the material in Comparative Example 1 after being assembled into a positive electrode / sodium metal half-cell and cycled at 1C rate. The comparison images before cycling were taken at 20,000X and 40,000X magnification, and the comparison images after cycling were taken at 50,000X and 80,000X magnification.

[0032] Figure 4 The voltage-capacity curve and the corresponding first-cycle differential capacity (dQ / dV) curve are obtained after the materials of Example 1 are assembled into a positive electrode / sodium metal half-cell and the first-cycle charge-discharge test is performed under 0.1C rate.

[0033] Figure 5 The graph shows the cycle specific capacity obtained after the materials of Example 1 were assembled into a positive electrode / sodium metal half-cell and subjected to 100 cycles of testing at a 1C rate.

[0034] Figure 6 The images show a comparison of the morphology of the positive electrode before and after cycling (after being cleaned and dried by DMC) of the positive electrode before and after cycling, respectively, after the materials of Example 1 were assembled into a positive electrode / sodium metal half-cell and cycled at 1C rate. The comparison images before cycling were taken at 40,000X magnification, and the comparison images after cycling were taken at 30,000X and 40,000X magnification, respectively.

[0035] Figure 7The figure shows the fitting results obtained by Rietveld refinement based on the P2 phase and O3 phase two-phase structure model of the material in Example 1.

[0036] Figure 8 The voltage-capacity curve (a) obtained after the materials of Example 2 were assembled into a positive electrode / sodium metal half-cell and subjected to the first charge-discharge test at a rate of 0.1C, and the cycle specific capacity curve (b) obtained after the materials of Example 2 were assembled into a positive electrode / sodium metal half-cell and subjected to a 60-cycle test at a rate of 1C.

[0037] Figure 9 The voltage-capacity curve is obtained from the first charge-discharge test under 0.1C conditions after the materials of Example 3 were assembled into a positive electrode / sodium metal half-cell.

[0038] Figure 10 The voltage-capacity curve (a) obtained after the materials of Example 4 were assembled into a positive electrode / sodium metal half-cell and subjected to the first charge-discharge test at a rate of 0.1C, and the cycle efficiency curve (b) obtained after the materials of Example 4 were assembled into a positive electrode / sodium metal half-cell and subjected to a 200-cycle test at a rate of 1C.

[0039] Figure 11 The images show the results of scanning electron microscopy (SEM) characterization of the cathode material obtained by sintering in Example 4, taken at magnifications of 1000X and 5000X.

[0040] Figure 12 The voltage-capacity curve is obtained from the first charge-discharge test under 0.1C conditions after the materials of Example 5 were assembled into a positive electrode / sodium metal half-cell.

[0041] Figure 13 The voltage-capacity curve (a) obtained after the materials of Example 6 were assembled into a positive electrode / sodium metal half-cell and subjected to the first charge-discharge test at a rate of 0.1C, and the cycle specific capacity curve (b) obtained after the materials of Example 6 were assembled into a positive electrode / sodium metal half-cell and subjected to a 200-cycle test at a rate of 1C.

[0042] Figure 14 The XRD test data summary diagram (3D stacked waterfall plot) of the materials in Examples 2-10 is used to compare and display the characteristic diffraction peak information of P2 (002) and O3 (003) in the 15°–17° (2θ) range of each example. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0044] Unless otherwise specified, all reagents used in the examples are commercially available.

[0045] In the examples, the sodium-nickel-manganese-based positive electrode used a degassing slurry, with polyvinylidene fluoride (PVDF) as the binder, Super P as the conductive agent, and N-methylpyrrolidone (NMP) as the solvent. The positive electrode material (i.e., the sodium-nickel-manganese-based positive electrode material prepared in Comparative Example 1 and Examples 1-10) had a PVDF:Super P ratio of 8:1:1 (mass ratio), with 0.1 g of PVDF added, corresponding to 2.5 mL of NMP. The degassing slurry time was 40 minutes. After sintering, the resulting sodium-nickel-manganese positive electrode slurry was coated onto aluminum foil with a coating thickness of 70 µm. The slurry was first dried in an 80°C forced-air drying oven for 30 minutes, then dried in a 120°C vacuum drying oven for 12 hours. After being rolled three times using a roller press, the slurry was cut into 14 mm electrode sheets for later use.

[0046] The sodium-nickel-manganese-based positive electrode / sodium half-cell assembled in the embodiment uses a 2032 model battery case, the diameter of the positive electrode plate is 12 mm, the diameter of the sodium plate is kept consistent with the steel gasket (15.6 mm), the amount of electrolyte used is 140 µL, the electrolyte used is 1M NaClO4 in EC:DEC=1:1 (vol%) with 5% FEC (wt%), and the separator used is GF / D model glass fiber with a diameter of 16 mm.

[0047] In the embodiment, the assembled battery was subjected to constant current charge-discharge test using a Blue Electric tester to evaluate cycle stability. The constant current charge-discharge cycle stability voltage test range of the sodium nickel manganese-based cathode / sodium half-cell was 2.0V-4.5V. The first three cycles were activated using 0.1C, and the long cycle test was performed using 1C. In the embodiments, the sodium-nickel-manganese-based positive electrode sheet tested by scanning electron microscopy was obtained by disassembling the positive electrode sheet that had not been cycled and the positive electrode / sodium battery that had been cycled to a certain number of cycles. The electrode was removed, cleaned, dried and sealed for characterization. Before use, the positive electrode sheet was stored in a centrifuge tube in a glove box and the mouth of the centrifuge tube was sealed with sealing glue. 1 / 4 of the electrode sheet was used for testing, and the microstructure of the sodium-nickel-manganese-based positive electrode sheet was tested by scanning electron microscopy.

[0048] To illustrate the electrochemical performance of the materials of this invention, examples 1–6 were selected for electrochemical testing and are shown in the accompanying figures; the remaining examples are used to demonstrate different component / doping combinations within the general formula and process window of this invention, and their composite structure with coexisting P2 and O3 phases was mainly verified by XRD (see Figure 14 (Table 1).

[0049] Comparative Example 1 Material composition: Na 0.8 Ni 0.3 Mn 0.7 O2 Detailed description of preparation method: (1) Raw material weighing and proportioning: The comparative sample was prepared using the traditional solid-state method. Sodium, nickel, and manganese sources were weighed according to the target stoichiometric ratio. The sodium source could be Na2CO3, the nickel source could be NiO, and the manganese source could be MnO2 or Mn2O3. To compensate for sodium volatilization during high-temperature sintering, the sodium source could be added in excess of 1–5 mol% of the theoretical amount. Each raw material was ball-milled to control the average particle size of each raw material within the range of 0.5–5 μm. No Li, Mg, or TM dopants were added to this comparative sample.

[0050] (2) Simple mechanical mixing (without ball milling): Place the raw materials weighed in step (1) into an agate mortar for simple mechanical mixing and grinding to make the powder uniformly mixed; the mixing and grinding time is 30–60 min. The mixing process does not involve planetary ball milling or high-energy ball milling. The mixed powder is placed in a ceramic crucible (it can be covered but the gas exchange gap is retained) and sintered.

[0051] (3) Sintering in a pure oxygen atmosphere: The crucible containing the powder is placed in a tube furnace and sintered in a pure oxygen atmosphere at a pressure of 0.95-1.05 atm. Continuous oxygen supply can be used, with an oxygen flow rate of 100 mL / min. The sintering program is as follows: the temperature is increased from room temperature to 900℃ at a heating rate of 2℃ / min, and held at 900℃ for 12 h. After the holding period, the cooling rate is controlled at 2℃ / min. The sintered product is then removed, ground, and sieved to obtain the final powder sample.

[0052] Detailed Performance Data: Electrochemical testing shows that within a voltage window of 2.0-4.5 V and a 0.1C rate, the material's first-cycle charge capacity is only 140.6 mAh / g, and its discharge specific capacity is only 91.0 mAh / g, far lower than those of the embodiments of this invention. In 1C cycling tests, the capacity retention rate after 100 cycles is only 72.3%. Detailed analysis of the battery's first-cycle voltage-discharge specific capacity diagram reveals that the high-voltage plateau above 4.3V contributes very little to the capacity during cycling, and the plateau is relatively short. Figure 1After 200 battery cycles, the electrode was removed, cleaned with DMC, and subjected to XRD analysis, which showed that the material underwent a significant irreversible phase transition from P2 to O2. Figure 2 Furthermore, the presence of numerous cracks in the particles indicates a severe lack of structural stability. Figure 3 ).

[0053] Example 1 Material composition: Na 0.80 Li 0.10 Mg 0.03 Ni 0.25 Mn 0.59 Ti 0.01 La 0.02 O2 Detailed description of preparation method: (1) Raw material weighing and proportioning: The samples of the examples were prepared using the high-temperature solid-state method. Sodium, lithium, nickel, manganese, magnesium, titanium, and lanthanum sources were accurately weighed according to the target stoichiometric ratio. The sodium source could be Na2CO3, the lithium source could be LiOH·H2O, the nickel source could be NiO, the manganese source could be MnO2, the titanium source could be TiO2, and the lanthanum source could be La2O3. To compensate for sodium volatilization during high-temperature sintering, the sodium source could be added in excess of 1–5 mol% of the theoretical amount. Each raw material was ball-milled to control the average particle size of each material within the range of 0.5–5 μm.

[0054] (2) Preparation of precursor by ball milling: The raw materials weighed in step (1) are first pre-mixed in an agate mortar for 30 minutes, and then transferred to a high-energy ball mill jar. Agate beads with a diameter of 3 mm-10 mm are used for milling. The ball mill jar is an agate jar with argon as the protective atmosphere. The ball milling speed is controlled at 500 rpm and the milling time is 10 hours. The ball-to-material ratio is maintained at 20:1. The uniformly mixed precursor is placed in a ceramic crucible (a lid can be added but a gas exchange gap should be maintained) for sintering.

[0055] (3) Sintering in a pure oxygen atmosphere: The crucible containing the precursor is placed in a tube furnace and sintered in a pure oxygen atmosphere at a pressure of 0.95-1.05 atm. Continuous oxygen supply can be used, with an oxygen flow rate of 100 mL / min. The sintering procedure is as follows: the temperature is increased from room temperature to 500℃ at a rate of 2℃ / min, held for 3 hours, then increased to 900℃ at a rate of 2℃ / min, held at 900℃ for 12 hours, and then cooled to room temperature at a rate of 1℃ / min after the holding period. The sintered product is then removed, ground, and sieved to obtain the final powder sample.

[0056] Detailed performance data: Electrochemical testing shows that within a voltage window of 2.0-4.5 V and a 0.1C rate, the first-week charging capacity reaches 225 mAh / g, of which approximately 58 mAh / g is contributed by anion redox reactions, as confirmed by differential capacity curve analysis. The first-week discharge efficiency is 88% (first-cycle charge / discharge and dQ / dV). Figure 4 After 100 cycles at 1C rate, the capacity retention is as high as 80.3% (cycles). Figure 5 Furthermore, the average voltage decay rate during cycling is only 0.0012 V / cycle. Refined XRD analysis shows that the material can be well fitted by a two-phase model of P2 and O3 phases, indicating that the sample forms a P2 / O3 coexisting composite phase structure (representative refined fitting results are shown in...). Figure 7 The mass fractions of the two phases are shown in Table 1. Combined with its cyclic specific capacity curve and post-cycle SEM characterization results ( Figure 6 As can be seen, the material exhibits good cycling stability and morphological stability during electrochemical cycling.

[0057] Example 2 Material composition: Na 0.78 Li 0.08 Mg 0.05 Ni 0.28 Mn 0.58 Ti 0.02 Zr 0.01 O2 Detailed description of preparation method: (1) Raw material weighing and proportioning: The samples of the examples were prepared using the high-temperature solid-state method. Sodium, nickel, lithium, manganese, magnesium, titanium, and zirconium sources were accurately weighed according to the target stoichiometric ratio. The sodium source could be Na2CO3, the lithium source could be LiOH·H2O, the nickel source could be NiO, the manganese source could be MnO2, the titanium source could be TiO2, and the zirconium source could be ZrO2. To compensate for sodium volatilization during high-temperature sintering, the sodium source could be added in excess of 1–5 mol% of the theoretical amount. Each raw material was ball-milled to control the average particle size of each material within the range of 0.5–5 μm.

[0058] (2) Preparation of precursor by ball milling: The raw materials weighed in step (1) are first pre-mixed in an agate mortar for 30 minutes, and then transferred to a high-energy ball mill jar. Agate beads with a diameter of 3 mm-10 mm are used for milling. The ball mill jar is an agate jar with argon as the protective atmosphere. The ball milling speed is controlled at 500 rpm and the milling time is 10 hours. The ball-to-material ratio is maintained at 20:1. The uniformly mixed precursor is placed in a ceramic crucible (a lid can be added but a gas exchange gap should be maintained) for sintering.

[0059] (3) Sintering in a pure oxygen atmosphere: The crucible containing the precursor is placed in a tube furnace and sintered in a pure oxygen atmosphere at a pressure of 0.95-1.05 atm. Continuous oxygen supply can be used, with an oxygen flow rate of 200 mL / min. The sintering program is as follows: a slow heating program is used, heating to 930℃ at a rate of 1℃ / min, holding for 18 hours, and then cooling to room temperature at a rate of 7℃ / min. After removing the sintered product, it is ground and sieved to obtain the final powder sample.

[0060] Detailed Performance Data: To verify the electrochemical effect of the technical solution of this invention, this application uses a representative sample, Example 1, for systematic electrochemical characterization and provides corresponding figures; the test conditions and electrode preparation methods are detailed in the Example section. Example 2 is a specific implementation of different component / doping combinations within the general formula and process window of this invention, all of which can be derived from... Figure 14 The XRD peak patterns shown confirm the formation of a composite structure with both P2 and O3 phases, and the relative contents of the two phases can be quantitatively obtained by XRD according to the method described in Table 1. Figure 14 As shown, the XRD pattern of the sample in this embodiment shows characteristic diffraction peaks of P2 (002) and O3 (003) in the 15°–17° (2θ) range, exhibiting discrete peak shapes, indicating the formation of a P2 / O3 co-existing composite phase structure. Regarding the electrochemical performance of Example 2, at a voltage window of 2.0–4.5 V and a rate of 0.1C, the first-week charging capacity reached 152.5 mAh / g (… Figure 8 (a)); at a 1C rate, the capacity retention after 60 long cycles is 81.3% ( Figure 8 (b)

[0061] Example 3 Material composition: Na 0.82 Li 0.12 Mg 0.01 Ni 0.22 Mn 0.62 Cu 0.02 Ru 0.01 O2 Detailed description of preparation method: (1) Raw material weighing and proportioning: The samples of the examples were prepared using the high-temperature solid-state method. Sodium, nickel, lithium, manganese, magnesium, copper, and ruthenium sources were accurately weighed according to the target stoichiometric ratio. The sodium source can be Na2CO3, the lithium source can be LiOH·H2O, the nickel source can be NiO, the manganese source can be MnO2, the copper source can be nano-CuO, and the ruthenium source can be RuO2. To compensate for sodium volatilization during high-temperature sintering, the sodium source can be added in excess of 1–5 mol% of the theoretical amount. The raw materials were ball-milled to control the average particle size of each raw material within the range of 0.5–5 μm.

[0062] (2) Preparation of precursor by ball milling: The raw materials weighed in step (1) are first pre-mixed in an agate mortar for 30 minutes, and then transferred to a high-energy ball mill jar. Agate beads with a diameter of 3 mm-10 mm are used for milling. The ball mill jar is an agate jar with argon as the protective atmosphere. The ball milling speed is controlled at 500 rpm and the milling time is 10 hours. The ball-to-material ratio is maintained at 20:1. The uniformly mixed precursor is placed in a ceramic crucible (a lid can be added but a gas exchange gap should be maintained) for sintering.

[0063] (3) Sintering in a pure oxygen atmosphere: The crucible containing the precursor is placed in a tube furnace and sintered in a pure oxygen atmosphere at a pressure of 0.95-1.05 atm. Continuous oxygen supply can be used, with an oxygen flow rate of 120 mL / min. The sintering procedure is as follows: An optimized three-stage heating sintering process is adopted. First, the temperature is rapidly increased to 550℃ at 5℃ / min to remove volatile components and held for 2 hours. Then, the temperature is slowly increased to 940℃ at 1℃ / min for crystal growth and held for 16 hours. Finally, the temperature is cooled to room temperature at a controlled rate of 1℃ / min. After the sintered product is removed, it is ground and sieved to obtain the final powder sample.

[0064] Detailed Performance Data: To verify the electrochemical effect of the technical solution of this invention, this application uses a representative sample, Example 1, for systematic electrochemical characterization and provides corresponding figures; the test conditions and electrode preparation methods are detailed in the Example section. Example 3 is a specific implementation of different component / doping combinations within the general formula and process window of this invention, all of which can be derived from... Figure 14 The XRD peak patterns shown confirm the formation of a composite structure with both P2 and O3 phases, and the relative contents of the two phases can be quantitatively obtained by XRD according to the method described in Table 1. Figure 14 As shown, the XRD pattern of the sample in this embodiment shows characteristic diffraction peaks of P2 (002) and O3 (003) in the 15°–17° (2θ) range, exhibiting discrete peak shapes, indicating the formation of a P2 / O3 co-existing composite phase structure. Regarding the electrochemical performance of Example 3, under a voltage window of 2.0–4.5 V and a rate of 0.1C, the first-week charge capacity reached 183.5 mAh / g, and the discharge specific capacity reached 136.9 mAh / g. Figure 9 ).

[0065] Example 4 Material composition: Na 0.75 Li 0.05 Mg 0.08 Ni 0.30 Mn 0.55 Ti 0.03 Mo 0.02 O2 Detailed description of preparation method: (1) Raw material weighing and proportioning: The samples of the examples were prepared using the high-temperature solid-state method. Sodium, nickel, lithium, manganese, magnesium, titanium, and molybdenum sources were accurately weighed according to the target stoichiometric ratio. The sodium source could be Na2CO3, the lithium source could be LiOH·H2O, the nickel source could be NiO, the manganese source could be MnO2, the titanium source could be TiO2, and the molybdenum source could be MoO3. To compensate for sodium volatilization during high-temperature sintering, the sodium source could be added in excess of 1–5 mol% of the theoretical amount. Each raw material was ball-milled to control the average particle size of each material within the range of 0.5–5 μm.

[0066] (2) Preparation of precursor by ball milling: The raw materials weighed in step (1) are first pre-mixed in an agate mortar for 30 minutes, and then transferred to a high-energy ball mill jar. Agate beads with a diameter of 3 mm-10 mm are used for milling. The ball mill jar is an agate jar with argon as the protective atmosphere. The ball milling speed is controlled at 500 rpm and the milling time is 10 hours. The ball-to-material ratio is maintained at 20:1. The uniformly mixed precursor is placed in a ceramic crucible (a lid can be added but a gas exchange gap should be maintained) for sintering.

[0067] (3) Sintering in a pure oxygen atmosphere: The crucible containing the precursor is placed in a tube furnace and sintered in a pure oxygen atmosphere at a pressure of 0.95-1.05 atm. Continuous oxygen supply can be used, with an oxygen flow rate of 150 mL / min. The sintering procedure is as follows: the temperature is increased to 980℃ at a rate of 1.5℃ / min, held for 12 hours for a high-temperature solid-phase reaction, and then cooled to room temperature at a rate of 5℃ / min. After removing the sintered product, it is ground and sieved to obtain the final powder sample.

[0068] Detailed Performance Data: To verify the electrochemical effect of the technical solution of this invention, this application uses a representative sample, Example 1, for systematic electrochemical characterization and provides corresponding figures; the test conditions and electrode preparation methods are detailed in the Example section. Example 4 is a specific implementation of different component / doping combinations within the general formula and process window of this invention, all of which can be derived from... Figure 14 The XRD peak patterns shown confirm the formation of a composite structure with both P2 and O3 phases, and the relative contents of the two phases can be quantitatively obtained by XRD according to the method described in Table 1. Figure 14 As shown, the XRD pattern of the sample in this embodiment shows characteristic diffraction peaks of P2 (002) and O3 (003) in the 15°–17° (2θ) range, exhibiting discrete peak shapes, indicating the formation of a P2 / O3 co-existing composite phase structure. Regarding the electrochemical performance of Example 4, at a voltage window of 2.0–4.5 V and a rate of 0.1C, the first-week charging capacity reached 164.2 mAh / g, and the discharge specific capacity reached 143.4 mAh / g. Figure 10 (a)), and the first-cycle charge-discharge coulombic efficiency reached 87.82% ( Figure 10(b)); At a 1C multiplier, the efficiency remained stable after 200 long cycles. Figure 10 (b)). SEM characterization tests were performed on the successfully sintered sample, revealing that the particles in Example 4 were uniformly distributed, with regular grain morphology and minimal adhesion. Figure 11 ).

[0069] Example 5 Material composition: Na 0.80 Li 0.10 Mg 0.03 Ni 0.25 Mn 0.59 Zn 0.01 Nb 0.02 O2 Detailed description of preparation method: (1) Raw material weighing and proportioning: The samples for the examples were prepared using the high-temperature solid-state method. Sodium, nickel, lithium, manganese, magnesium, zinc, and niobium sources were accurately weighed according to the target stoichiometric ratio. The sodium source could be Na2CO3, the lithium source could be LiOH·H2O, the nickel source could be NiO, the manganese source could be MnO2, the zinc source could be ZnO, and the niobium source could be Nb2O5. To compensate for sodium volatilization during high-temperature sintering, the sodium source could be added in excess of 1–5 mol% of the theoretical amount. Each raw material was ball-milled to control the average particle size within the range of 0.5–5 μm.

[0070] (2) Preparation of precursor by ball milling: The raw materials weighed in step (1) are first pre-mixed in an agate mortar for 30 minutes, and then transferred to a high-energy ball mill jar. Agate beads with a diameter of 3 mm-10 mm are used for milling. The ball mill jar is an agate jar with argon as the protective atmosphere. The ball milling speed is controlled at 500 rpm and the milling time is 10 hours. The ball-to-material ratio is maintained at 20:1. The uniformly mixed precursor is placed in a ceramic crucible (a lid can be added but a gas exchange gap should be maintained) for sintering.

[0071] (3) Sintering in a pure oxygen atmosphere: The crucible containing the precursor is placed in a tube furnace and sintered in a pure oxygen atmosphere at a pressure of 0.95-1.05 atm. Continuous oxygen supply can be used, with an oxygen flow rate of 120 mL / min. The sintering procedure is as follows: sintering at 950℃ for 14 hours, with a heating rate controlled at 2℃ / min, to carry out a high-temperature solid-phase reaction, followed by cooling to room temperature at a rate of 5℃ / min. After removing the sintered product, it is ground and sieved to obtain the final powder sample.

[0072] Detailed Performance Data: To verify the electrochemical effect of the technical solution of this invention, this application uses a representative sample, Example 1, for systematic electrochemical characterization and provides corresponding figures; the test conditions and electrode preparation methods are detailed in the Example section. Example 5 is a specific implementation of different component / doping combinations within the general formula and process window of this invention, all of which can be derived from... Figure 14 The XRD peak patterns shown confirm the formation of a composite structure with both P2 and O3 phases, and the relative contents of the two phases can be quantitatively obtained by XRD according to the method described in Table 1. Figure 14 As shown, the XRD pattern of the sample in this embodiment shows characteristic diffraction peaks of P2 (002) and O3 (003) in the 15°–17° (2θ) range, exhibiting discrete peak shapes, indicating the formation of a P2 / O3 co-existing composite phase structure. Regarding the electrochemical performance of Example 5, within a voltage window of 2.0–4.5 V and a rate of 0.1C, the first-week charge capacity reached 198.6 mAh / g, and the discharge specific capacity reached 140.4 mAh / g. Figure 12 ).

[0073] Example 6 Material composition: Na 0.78 Li 0.09 Mg 0.06 Ni 0.26 Mn 0.56 Fe 0.02 Rh 0.01 O2 Detailed description of preparation method: (1) Raw material weighing and proportioning: The samples of the examples were prepared using the high-temperature solid-state method. Sodium, nickel, lithium, manganese, magnesium, iron, and rhodium sources were accurately weighed according to the target stoichiometric ratio. The sodium source could be Na2CO3, the lithium source could be LiOH·H2O, the nickel source could be NiO, the manganese source could be MnO2, the iron source could be Fe2O3, and the rhodium source could be Rh2O3. To compensate for sodium volatilization during high-temperature sintering, the sodium source could be added in excess of 1–5 mol% of the theoretical amount. Each raw material was ball-milled to control the average particle size of each material within the range of 0.5–5 μm.

[0074] (2) Preparation of precursor by ball milling: The raw materials weighed in step (1) are first pre-mixed in an agate mortar for 30 minutes, and then transferred to a high-energy ball mill jar. Agate beads with a diameter of 3 mm-10 mm are used for milling. The ball mill jar is an agate jar with argon as the protective atmosphere. The ball milling speed is controlled at 500 rpm and the milling time is 10 hours. The ball-to-material ratio is maintained at 20:1. The uniformly mixed precursor is placed in a ceramic crucible (a lid can be added but a gas exchange gap should be maintained) for sintering.

[0075] (3) Sintering in a pure oxygen atmosphere: The crucible containing the precursor is placed in a tube furnace and sintered in a pure oxygen atmosphere at a pressure of 0.95-1.05 atm. Continuous oxygen supply can be used, with an oxygen flow rate of 180 mL / min. The sintering procedure is as follows: A three-stage sintering process is adopted. First, the temperature is raised to 500℃ at a rate of 2℃ / min for pretreatment and held for 3 hours to remove bound water and carbonate ions. Then, the temperature is raised to 950℃ at a rate of 1℃ / min for main sintering and held for 18 hours. Subsequently, the temperature is lowered to room temperature at a rate of 5℃ / min. After the sintered product is removed, it is ground and sieved to obtain the final powder sample.

[0076] Detailed Performance Data: To verify the electrochemical effect of the technical solution of this invention, this application uses a representative sample, Example 1, for systematic electrochemical characterization and provides corresponding figures; the test conditions and electrode preparation methods are detailed in the Example section. Example 6 is a specific implementation of different component / doping combinations within the general formula and process window of this invention, all of which can be derived from... Figure 14 The XRD peak patterns shown confirm the formation of a composite structure with both P2 and O3 phases, and the relative contents of the two phases can be quantitatively obtained by XRD according to the method described in Table 1. Figure 14 As shown, the XRD pattern of the sample in this embodiment shows characteristic diffraction peaks of P2 (002) and O3 (003) in the 15°–17° (2θ) range, exhibiting discrete peak shapes, indicating the formation of a P2 / O3 co-existing composite phase structure. Regarding the electrochemical performance of Example 6, within a voltage window of 2.0–4.5 V and a rate of 0.1C, the first-week charge capacity reached 170.4 mAh / g, and the discharge specific capacity reached 129.7 mAh / g. Figure 13 (a)); at a 1C multiplier, the capacity retention rate after 100 cycles is 87.0%, and after 200 long cycles, the capacity retention rate is 67.1% ( Figure 13 (b)

[0077] Example 7 Material composition: Na 0.80 Li 0.12 Mg 0.02 Ni 0.24 Mn 0.59 Co 0.01 Pd 0.02 O2 Detailed description of preparation method: (1) Raw material weighing and proportioning: The samples of the examples were prepared using the high-temperature solid-state method. Sodium, nickel, lithium, manganese, magnesium, cobalt, and palladium sources were accurately weighed according to the target stoichiometric ratio. The sodium source could be Na2CO3, the lithium source could be LiOH·H2O, the nickel source could be NiO, the manganese source could be MnO2, the cobalt source could be Co2O3, and the palladium source could be PdO. To compensate for sodium volatilization during high-temperature sintering, the sodium source could be added in excess of 1–5 mol% of the theoretical amount. Each raw material was ball-milled to control the average particle size of each material within the range of 0.5–5 μm.

[0078] (2) Preparation of precursor by ball milling: The raw materials weighed in step (1) are first pre-mixed in an agate mortar for 30 minutes, and then transferred to a high-energy ball mill jar. Agate beads with a diameter of 3 mm-10 mm are used for milling. The ball mill jar is an agate jar with argon as the protective atmosphere. The ball milling speed is controlled at 200 rpm, the milling time is 8 hours, and the ball-to-material ratio is maintained at 20:1. The uniformly mixed precursor is placed in a ceramic crucible (a lid can be added but a gas exchange gap is maintained) for sintering.

[0079] (3) Sintering in a pure oxygen atmosphere: The crucible containing the precursor is placed in a tube furnace and sintered in a pure oxygen atmosphere at a pressure of 0.95-1.05 atm. Continuous oxygen supply can be used, with an oxygen flow rate of 100 mL / min. The sintering procedure is as follows: the temperature is increased to 960℃ at a heating rate of 1.5℃ / min, held for 16 hours for a high-temperature solid-phase reaction, and then slowly cooled to room temperature (0.5℃ / min) to eliminate internal stress. After removing the sintered product, it is ground and sieved to obtain the final powder sample.

[0080] Example 7 illustrates specific implementations of different component / doping combinations within the general formula and process window of this invention, all of which can be derived from... Figure 14 The XRD peak patterns shown confirm the formation of a composite structure with both P2 and O3 phases, and the relative contents of the two phases can be quantitatively obtained by XRD according to the method described in Table 1. Figure 14 As shown, the XRD pattern of the sample in this embodiment shows characteristic diffraction peaks of P2 (002) and O3 (003) in the 15°–17° (2θ) range and exhibits discrete peak shapes, indicating the formation of a P2 / O3 symbiotic composite phase structure.

[0081] Example 8 Material composition: Na 0.82 Li 0.07 Mg 0.04 Ni 0.27 Mn 0.58 Cu 0.01 Ce 0.01 O2 Detailed description of preparation method: (1) Raw material weighing and proportioning: The samples of the examples were prepared using the high-temperature solid-state method. Sodium, nickel, lithium, manganese, magnesium, copper, and cerium sources were accurately weighed according to the target stoichiometric ratio. The sodium source can be Na2CO3, the lithium source can be LiOH·H2O, the nickel source can be NiO, the manganese source can be MnO2, the copper source can be nano-CuO, and the cerium source can be Ce2O3. To compensate for sodium volatilization during high-temperature sintering, the sodium source can be added in excess of 1–5 mol% of the theoretical amount. Each raw material was ball-milled to control the average particle size of each raw material within the range of 0.5–5 μm.

[0082] (2) Preparation of precursor by ball milling: The raw materials weighed in step (1) are first premixed in an agate mortar for 30 minutes, and then transferred to a high-energy ball mill jar. Agate beads with a diameter of 3 mm-10 mm are used for milling. The ball mill jar is an agate jar with argon as the protective atmosphere. The ball milling speed is controlled at 500 rpm and the milling time is 15 hours. The ball-to-material ratio is maintained at 20:1. The uniformly mixed precursor is placed in a ceramic crucible (a lid can be added but a gas exchange gap should be maintained) for sintering.

[0083] (3) Sintering in a pure oxygen atmosphere: The crucible containing the precursor is placed in a tube furnace and sintered in a pure oxygen atmosphere at a pressure of 0.95-1.05 atm. Continuous oxygen supply can be used, with an oxygen flow rate of 150 mL / min. The sintering procedure is as follows: the temperature is precisely controlled to rise to 925℃ at a heating rate of 1℃ / min, held at that temperature for 20 hours for a high-temperature solid-phase reaction, and then cooled to room temperature at a rate of 5℃ / min. After removing the sintered product, it is ground and sieved to obtain the final powder sample.

[0084] Example 8 illustrates specific implementations of different component / doping combinations within the general formula and process window of this invention, all of which can be derived from... Figure 14 The XRD peak patterns shown confirm the formation of a composite structure with both P2 and O3 phases, and the relative contents of the two phases can be quantitatively obtained by XRD according to the method described in Table 1. Figure 14 As shown, the XRD pattern of the sample in this embodiment shows characteristic diffraction peaks of P2 (002) and O3 (003) in the 15°–17° (2θ) range and exhibits discrete peak shapes, indicating the formation of a P2 / O3 symbiotic composite phase structure.

[0085] Example 9 Material composition: Na 0.78 Li 0.15 Mg 0.01 Ni 0.23 Mn 0.60 Zr 0.01 W 0.02 O2 Detailed description of preparation method: (1) Raw material weighing and proportioning: The samples for the examples were prepared using the high-temperature solid-state method. Sodium, nickel, lithium, manganese, magnesium, zirconium, and tungsten sources were accurately weighed according to the target stoichiometric ratio. The sodium source could be Na2CO3, the lithium source could be LiOH·H2O, the nickel source could be NiO, the manganese source could be MnO2, the zirconium source could be ZrO2, and the tungsten source could be WO3. To compensate for sodium volatilization during high-temperature sintering, the sodium source could be added in excess of 1–5 mol% of the theoretical amount. Each raw material was ball-milled to control the average particle size within the range of 0.5–5 μm.

[0086] (2) Preparation of precursor by ball milling: The raw materials weighed in step (1) are first pre-mixed in an agate mortar for 30 minutes, and then transferred to a high-energy ball mill jar. Agate beads with a diameter of 3 mm-10 mm are used for milling. The ball mill jar is an agate jar with argon as the protective atmosphere. The ball milling speed is controlled at 500 rpm and the milling time is 10 hours. The ball-to-material ratio is maintained at 20:1. The uniformly mixed precursor is placed in a ceramic crucible (a lid can be added but a gas exchange gap should be maintained) for sintering.

[0087] (3) Sintering in a pure oxygen atmosphere: The crucible containing the precursor is placed in a tube furnace and sintered in a pure oxygen atmosphere at a pressure of 0.95-1.05 atm; continuous oxygen supply can be used, with an oxygen flow rate of 150 mL / min. The sintering procedure is as follows: a unique slow sintering process is adopted, with the temperature raised to 945℃ at an ultra-slow heating rate of 0.5℃ / min, and held for 24 hours to ensure the formation of a complete composite phase structure, followed by cooling to room temperature at 3℃ / min. After removing the sintered product, it is ground and sieved to obtain the final powder sample.

[0088] Example 9 illustrates specific implementations of different component / doping combinations within the general formula and process window of this invention, all of which can be derived from... Figure 14 The XRD peak patterns shown confirm the formation of a composite structure with both P2 and O3 phases, and the relative contents of the two phases can be quantitatively obtained by XRD according to the method described in Table 1. Figure 14 As shown, the XRD pattern of the sample in this embodiment shows characteristic diffraction peaks of P2 (002) and O3 (003) in the 15°–17° (2θ) range and exhibits discrete peak shapes, indicating the formation of a P2 / O3 symbiotic composite phase structure.

[0089] Example 10 Material composition: Na 0.80 Li 0.10 Mg 0.03 Ni 0.25 Mn 0.59 Ti 0.01 La 0.02 O2 Detailed description of preparation method: (1) Raw material weighing and proportioning: The samples of the examples were prepared using the high-temperature solid-state method. Sodium, nickel, lithium, manganese, magnesium, titanium, and lanthanum sources were accurately weighed according to the target stoichiometric ratio. The sodium source could be Na2CO3, the lithium source could be LiOH·H2O, the nickel source could be NiO, the manganese source could be MnO2, the titanium source could be TiO2, and the lanthanum source could be La2O3. To compensate for sodium volatilization during high-temperature sintering, the sodium source could be added in excess of 1–5 mol% of the theoretical amount. Each raw material was ball-milled to control the average particle size of each material within the range of 0.5–5 μm.

[0090] (2) Preparation of precursor by ball milling: The raw materials weighed in step (1) are first pre-mixed in an agate mortar for 30 minutes, and then transferred to a high-energy ball mill jar. Agate beads with a diameter of 3 mm-10 mm are used for milling. The ball mill jar is an agate jar with argon as the protective atmosphere. The ball milling speed is controlled at 500 rpm and the milling time is 10 hours. The ball-to-material ratio is maintained at 20:1. The uniformly mixed precursor is placed in a ceramic crucible (a lid can be added but a gas exchange gap should be maintained) for sintering.

[0091] (3) Sintering in a pure oxygen atmosphere: The crucible containing the precursor is placed in a tube furnace and sintered in a pure oxygen atmosphere at a pressure of 0.95-1.05 atm. Continuous oxygen supply can be used, with an oxygen flow rate of 140 mL / min. The sintering procedure is as follows: the temperature is increased to 950℃ at a heating rate of 1.5℃ / min, held for 15 hours for high-temperature solid-phase reaction, and cooled to room temperature at a cooling rate of 1℃ / min. After removing the sintered product, it is ground and sieved to obtain the final powder sample.

[0092] Example 10 is a specific implementation of different component / doping combinations within the general formula and process window of the present invention, all of which can be derived from... Figure 14 The XRD peak patterns shown confirm the formation of a composite structure with both P2 and O3 phases, and the relative contents of the two phases can be quantitatively obtained by XRD according to the method described in Table 1. Figure 14 As shown, the XRD pattern of the sample in this embodiment shows characteristic diffraction peaks of P2 (002) and O3 (003) in the 15°–17° (2θ) range and exhibits discrete peak shapes, indicating the formation of a P2 / O3 symbiotic composite phase structure.

[0093] Table 1

[0094] Note: wR and GOF are Rietveld refinement goodness-of-fit indices, which are only refined and given for representative samples (Example 1); for other examples, the coexistence characteristics of two phases are evaluated by XRD peak position and peak separation fitting.

[0095] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A sodium-ion battery cathode material based on a P2-O3 composite phase, characterized in that, The general chemical formula of the cathode material is Na. μ Li ν Mg γ Ni x Mn z TM y O2, wherein: 0.75≤μ≤0.85, 0.05≤ν≤0.15, 0.01≤γ≤0.10, 0.20≤x≤0.30, 0.55≤z≤0.70, 0.005≤y≤0.05, and 0.95≤ν+γ+x+z+y≤1.05; TM is a combination of at least two elements selected from 3d transition metals, 4d transition metals, 5d transition metals, and lanthanides.

2. The sodium-ion battery cathode material based on the P2-O3 composite phase according to claim 1, characterized in that, μ is 0.75–0.85; ν is 0.08–0.12; and γ is 0.02–0.

08.

3. The sodium-ion battery cathode material based on the P2-O3 composite phase according to claim 1, characterized in that, The doping element TM includes at least one of TM1 and TM2, wherein TM1 is a first transition metal element, and TM2 is a second transition metal element and / or a lanthanide or actinide element, wherein TM1 is selected from at least one of Ti, Fe, Co, Cu, and Zn; and TM2 is selected from at least one of Zr, Nb, Mo, Ru, Rh, Pd, W, La, and Ce.

4. The sodium-ion battery cathode material based on the P2-O3 composite phase according to claim 3, characterized in that, When the dopant element TM includes TM1 and TM2, the molar ratio of TM1 to TM2 is 10:1 to 1:

2.

5. A method for preparing a sodium-ion battery cathode material based on a P2-O3 composite phase according to any one of claims 1-4, characterized in that... Includes the following steps: (1) Raw material pretreatment: Sodium source, lithium source, magnesium source, nickel source, manganese source and TM source are ball-milled respectively to control the average particle size of each raw material within the range of 0.5-5μm; (2) Ball milling: Weigh each raw material according to the stoichiometric ratio of the chemical formula, and mix them by ball milling under a protective atmosphere; (3) Calcination treatment: The mixed precursor is heated and calcined in a pure oxygen atmosphere, and then cooled to room temperature to obtain the cathode material.

6. The method for preparing sodium-ion battery cathode material based on P2-O3 composite phase according to claim 5, characterized in that: The sodium source mentioned in step (1) is at least one of Na2CO3, NaOH, and NaNO3; The lithium source mentioned in step (1) is at least one of LiOH·H2O, Li2CO3, and Li2C4O4·2H2O; The magnesium source mentioned in step (1) is at least one of MgO, Mg(OH)2, and MgCO3; The nickel source mentioned in step (1) is at least one of NiO and Ni(OH)2; The manganese source mentioned in step (1) is at least one of MnO2, Mn2O3, and Mn3O4; The TM source mentioned in step (1) is an oxide of TM; The ball milling mixture described in step (2) is ball milling at a speed of 300-3000 rpm for 5-15 hours, with a ball-to-material ratio of 10:1 to 30:1; The protective atmosphere mentioned in step (2) refers to the process being carried out under an Ar and / or N2 atmosphere.

7. The method for preparing sodium-ion battery cathode material based on P2-O3 composite phase according to claim 5, characterized in that: The heating and calcination mentioned in step (3) refers to heating to 880℃-1000℃ at a heating rate of 1-5℃ / min and holding for 8-24 hours; during the calcination process, the atmospheric pressure is maintained at 0.95-1.2 standard atmospheres, and continuous oxygen is used with an oxygen flow rate of 100-200mL / min. The cooling to room temperature mentioned in step (3) refers to cooling to room temperature at a cooling rate of 0.5-7℃ / min.

8. The method for preparing sodium-ion battery cathode material based on P2-O3 composite phase according to claim 5, characterized in that: In step (3), the heating and calcination process is first raised to 500-600℃ at a rate of 1-5℃ / min and held for 2-5 hours to remove volatile components. Then, the temperature is raised to 880℃-1000℃ at a rate of 1-5℃ / min and held for 8-24 hours.

9. The application of the sodium-ion battery cathode material based on the P2-O3 composite phase according to any one of claims 1-4 in sodium-ion batteries.

10. A sodium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that... The positive electrode comprises the high-capacity sodium-ion battery positive electrode material based on the P2-O3 composite phase as described in any one of claims 1-4, a conductive agent, and a binder, wherein the mass ratio of the positive electrode material, the conductive agent, and the binder is 80-90:5-15:3-10.

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