O3 phase sodium-ion battery layered oxide cathode material, preparation method and application thereof

Abstract

This invention belongs to the technical field of sodium-ion battery cathode materials. Specifically, it relates to an O3-phase layered oxide cathode material for sodium-ion batteries, its preparation method, and its applications. The chemical formula of the O3-phase layered oxide cathode material for sodium-ion batteries provided in this invention is Na. a Ni b Fe c Mn d M1 e M2 f O 2 , where 0.8≤ a ≤0.88, 0.25≤ b ≤0.35, 0.05≤ c ≤0.15, 0.30≤ d ≤0.45, 0.05≤ e ≤0.10, 0.15≤ f ≤0.30, M1 is Li, M2 is Ti. This chemical formula for the cathode material was prepared using a synergistic innovative method involving nickel carbonylation, Li / Ti co-doping, and segmented calcination. This resulted in a comprehensive improvement in the cathode material's high capacity, high rate capability, long cycle life, wide temperature range, and high voltage resistance, achieving a first-cycle discharge capacity of 130.78 mAh·g at 0.05C. ‑1 At 10C rate, the capacity is 98.33mAh·g. ‑1 .

Description

Technical Field

[0001] This invention belongs to the technical field of sodium-ion battery cathode materials, and specifically relates to an O3 phase sodium-ion battery layered oxide cathode material, its preparation method, and its application. Background Technology

[0002] Sustainable energy is a key solution to addressing global climate change and environmental issues. Against the backdrop of the energy structure transitioning from fossil fuels to renewable energy, developing efficient electrochemical energy storage technologies has become a strategic requirement for large-scale renewable energy storage. Currently, lithium-ion batteries are considered one of the most promising energy storage systems due to their high energy density, long cycle life, and mature industrialization technology. However, the scarcity of lithium resources, their uneven geographical distribution, and the resulting high costs and safety concerns severely restrict their application in large-scale energy storage.

[0003] Sodium-ion batteries, as an emerging energy storage system, benefit from abundant sodium resources (2.36% of the Earth's crust), low raw material costs (sodium carbonate is about 1 / 30 the price of lithium carbonate), excellent high and low temperature performance, and the availability of sodium. + With Li + Similar physicochemical properties demonstrate enormous development potential. Among the three key components of sodium-ion batteries, the cathode material has a decisive influence on battery performance. Current research mainly focuses on three systems: layered transition metal oxides, polyanionic compounds, and Prussian blue analogues. Among these, layered transition metal oxides have a high theoretical capacity (>200 mAh·g). -1 Suitable operating voltage (2.5V vs. ~3.5V vs. Na) + With its advantages such as Na+ and ease of large-scale preparation, it is considered one of the most promising cathode materials for industrialization.

[0004] Layered transition metal oxide cathode based on Na +The coordination environment of these materials is mainly divided into two structures: P2 type and O3 type. Although P2 type materials have good cycle stability, their inherent low Na content (stoichiometric ratio x≤0.7) leads to problems such as low initial charge capacity and insufficient first-cycle coulombic efficiency (<80%), which limits their practical application in full cells. In contrast, O3 type layered oxides have the following advantages: higher initial Na content (x>0.8), which can provide higher reversible capacity; a higher operating voltage platform (average 3.2V vs. 2.7V for P2 type), which is conducive to improving energy density; and a more stable charge-discharge curve, which is convenient for battery management system design. However, O3 type materials still face multiple challenges in practical applications: low ionic conductivity leads to poor rate performance; complex phase transitions (such as O3→O3'→P3) occur during charge and discharge, causing structural degradation; interfacial side reactions between electrodes and electrolytes also significantly affect their cycle stability; and performance degradation is severe over a wide temperature range, making it difficult to meet the needs of multiple application scenarios.

[0005] To address the above issues, researchers have developed various effective modification strategies in recent years, such as element doping, surface coating, microstructure design, and multiphase composites. However, the following key drawbacks still exist: (1) Limitations in nickel source selection: Existing technologies generally use conventional nickel sources such as nickel oxide and nickel carbonate, which have low reactivity, wide particle size distribution, and are prone to agglomeration, resulting in low crystallinity and uneven element distribution. There are local component segregation and inactive regions, which limit the number of sodium ion storage sites and transport efficiency. Furthermore, they cannot form effective synergy with doped elements, making it difficult to achieve high capacity, long cycle life, and wide temperature range performance. (2) Poor adaptability to wide temperature range: Existing modification technologies have not systematically optimized key issues such as ion diffusion and interface reactions under high and low temperature environments. The problems of high ion diffusion barriers at low temperatures and intensified interface side reactions at high temperatures have not been effectively solved, making it difficult to meet the needs of multiple application scenarios. (3) Insufficient high voltage resistance: Under high voltage, the lattice oxygen activity of existing materials is easily enhanced, the dissolution of transition metals is intensified, and the interface side reactions are significant, resulting in rapid capacity decay and poor cycle stability. Summary of the Invention

[0006] To address the shortcomings of the existing technologies, the present invention aims to provide an O3-phase sodium-ion battery layered oxide cathode material, its preparation method, and its application. This invention prepares an O3-phase sodium-ion battery layered oxide cathode material with uniform crystallization, stable structure, and high utilization of active sites, thus solving multiple problems such as sluggish kinetics, harmful phase transitions, and interface instability.

[0007] To address the aforementioned technical problems, this invention provides a method for preparing an O3-phase sodium-ion battery layered oxide cathode material, comprising the following steps: Weigh sodium carbonate, nickel carbonyl, ferric oxide, manganese dioxide, lithium carbonate, and titanium dioxide according to the stoichiometric ratios in their chemical formulas, ensuring a 5%–10% excess of sodium carbonate (to compensate for sodium volatilization at high temperatures) and a 5%–10% excess of lithium carbonate (to ensure Li…). + (After thorough doping), the dispersant is completely removed by ball milling, drying and grinding; the dried block precursor is finely ground in an agate mortar to ensure close contact of particles during the tableting process, thus obtaining the raw material to be processed; After the raw material to be processed is tableted, a blank to be processed is obtained. By controlling the tableting pressure and holding time, a blank with moderate density is formed, which ensures the mass transfer efficiency in the high-temperature reaction and avoids the reaction being too incomplete due to the blank being too dense. The raw material to be processed is heated to 400℃~500℃ in air at a heating rate of 2℃ / min~5℃ / min for the first calcination and held for 4h~6h. The purpose is to remove residual moisture and impurities from the raw material, and at the same time promote the initial reaction of sodium carbonate with other precursors, avoiding structural collapse caused by violent reaction at high temperature. Then, the temperature is raised to 800℃~1000℃ at a heating rate of 2℃ / min~5℃ / min for the second calcination and held for 10h~20h. After calcination, the temperature is first cooled to 100℃~300℃ at a heating rate of 2℃ / min~5℃ / min, and then naturally cooled to room temperature in an argon atmosphere. After crushing and sieving, the O3 phase sodium ion battery layered oxide cathode material is obtained.

[0008] Preferably, the purity of sodium carbonate is ≥99.5%, the particle size of nickel carbonyl is 20nm~50nm, the purity of nickel carbonyl is ≥99.9%, the purity of ferric oxide is ≥99.0%, the purity of manganese dioxide is ≥99.0%, the purity of titanium dioxide is ≥99.0%, anhydrous ethanol (purity ≥99.7%) is used as the dispersant during ball milling, the ball-to-material ratio is 10~15:1, the rotation speed is 300~450r / min, the ball milling time is 10h~15h, and the raw material to be processed is obtained by sieving through a 200-mesh sieve with a particle size of 50~100μm.

[0009] Preferably, the amount of raw material to be processed during tableting is 300mg to 500mg, the tableting pressure is 10MPa to 25MPa, the tableting time is 5min to 15min, and the resulting tablet diameter is 12mm. By controlling the tableting pressure and holding time, a green body with moderate density is formed, which ensures the mass transfer efficiency in the high-temperature reaction and avoids the reaction being too incomplete due to the green body being too dense.

[0010] This invention provides a method for preparing O3-phase sodium-ion battery layered oxide cathode material, which yields the O3-phase sodium-ion battery layered oxide cathode material.

[0011] Preferably, the chemical formula is Na. a Nib Fe c Mn d M1 e M2 f O 2 , where 0.8≤ a ≤0.88, 0.25≤ b ≤0.35, 0.05≤ c ≤0.15, 0.30≤ d ≤0.45, 0.05≤ e ≤0.10, 0.15≤ f ≤0.30, M1 is Li, M2 is Ti.

[0012] Preferably, the layered oxide cathode material for O3-phase sodium-ion batteries has an initial discharge capacity ≥130 mAh·g at a rate of 0.05C within a voltage range of 2.0V to 4.2V. -1 Capacity at 10C rate ≥ 98mAh・g -1 .

[0013] Preferably, the O3-phase sodium-ion battery layered oxide cathode material retains a capacity of ≥82% after 1200 cycles at -20℃ and 1C; ≥81% after 700 cycles at 60℃ and 10C; ≥80% after 1100 cycles at 10C; and ≥79% after 1000 cycles at 2.0V to 4.2V.

[0014] Application of an O3-phase layered oxide cathode material in sodium-ion batteries.

[0015] A positive electrode sheet comprising an O3 phase sodium-ion battery layered oxide positive electrode material.

[0016] A sodium-ion battery includes a negative electrode, an electrolyte, and a positive electrode.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention presents a method for preparing layered oxide cathode materials for O3-phase sodium-ion batteries. This method employs a synergistic innovation of carbonyl nickel co-doping with Li / Ti and segmented calcination, achieving comprehensive improvements in the high capacity, high rate capability, long cycle life, wide temperature range, and high voltage resistance of the O3-phase sodium-ion battery layered oxide cathode material. This is because the high-specific-surface-area nano-sized carbonyl nickel particles have narrow particle size distribution, are not prone to agglomeration, and have high reactivity. During high-temperature sintering, they can rapidly undergo solid-phase reactions with Fe2O3, MnO2, TiO2, Li2CO3, and Na2CO3 precursors to form a uniform oxide solid solution. This improves the distribution of various metal elements and avoids the component segregation and inactive regions caused by the large particle size and low activity of conventional nickel sources. This increases the number of sodium-ion storage sites and transport efficiency. Simultaneously, Li / Ti co-doping enhances the stability of the transition metal-oxygen bond, suppresses lattice oxygen loss, and further improves interface stability. Moreover, Li... + With a small radius (approximately 0.076 nm), it can be embedded in the gaps between layered structures, expanding the Na... + Migration pathways, reducing migration energy barriers; Ti 4+ With a radius similar to that of transition metal ions (approximately 0.061 nm), it can replace some transition metal sites, forming a pillar effect, suppressing interlayer slip and the O3→O3'→P3 phase transition, and solving the problem of intensified interfacial side reactions at high temperatures. The synergistic effect of these two factors achieves simultaneous optimization of structural stability and ion transport kinetics. Furthermore, the O3-phase sodium-ion battery layered oxide cathode material prepared with carbonyl nickel has a denser and smoother surface, a smaller specific surface area, and a reduced contact area with the electrolyte, which can suppress interfacial side reactions and transition metal dissolution, reduce capacity decay, and improve cycle stability. Simultaneously, the segmented calcination process provided in this invention removes impurities and moisture in the low-temperature pre-calcination stage, avoiding structural defects caused by violent reactions at high temperatures; the high-temperature sintering stage ensures complete crystallization of the layered structure; and the gradient cooling stage alleviates lattice stress and reduces crystal defects, further improving the structural stability and cycle life of the material.

[0018] The O3-phase sodium-ion battery layered oxide cathode material prepared by this invention exhibits excellent comprehensive performance over a wide temperature range (-20℃~60℃) and high voltage (2.0V~4.2V), breaking through the application limitations of existing materials. Specifically, within a voltage range of 2.0V~4.2V, the first-cycle discharge capacity at a 0.05C rate is ≥130mAh・g. -1 Capacity at 10C rate ≥ 98mAh・g -1 After 1100 cycles at 10°C, the capacity retention rate is ≥80%; after 1200 cycles at -20°C and 1°C, the capacity retention rate is ≥82%; after 700 cycles at 60°C and 10°C, the capacity retention rate is ≥81%. Attached Figure Description

[0019] Figure 1The first charge-discharge curves (left) and rate performance (right) of LT-NFM prepared in Example 1 and NFM prepared in Comparative Example 1 are shown.

[0020] Figure 2 The graph shows the cycling performance of LT-NFM prepared in Example 1 and NFM prepared in Comparative Example 1 at 10C.

[0021] Figure 3 The graph shows the cycling performance of LT-NFM prepared in Example 1 and NFM prepared in Comparative Example 1 at 60°C and 10°C.

[0022] Figure 4 The graph shows the cycling performance of LT-NFM prepared in Example 1 at -20°C and 1°C.

[0023] Figure 5 The graph shows the cycling performance of LT-NFM prepared in Example 1 of this invention and NFM prepared in Comparative Example 1 at 10C within a voltage range of 2.0V to 4.2V.

[0024] Figure 6 The GITT curves (left) of LT-NFM prepared in Example 1 of the present invention and NFM prepared in Comparative Example 1 and the calculated sodium ion diffusion coefficient (right) are shown in the voltage range of 2.0V to 4.0V.

[0025] Figure 7 The variable speed CV curve (left) and pseudocapacitive contribution (right) of the LT-NFM prepared in Example 1 of this invention in the voltage range of 2.0V to 4.0V are shown.

[0026] Figure 8 The graphs show the variable speed CV curves (left) and pseudocapacitive contribution (right) of the NFM prepared in Comparative Example 1 of this invention within the voltage range of 2.0V to 4.0V.

[0027] Figure 9 The diagram shows the air stability of LT-NFM prepared in Example 1 and NFM prepared in Comparative Example 1.

[0028] Figure 10 The image shown is an XRD refinement image of LT-NFM prepared in Example 1 of this invention.

[0029] Figure 11 The first charge-discharge curves (left) and rate performance (right) of LT-NFM prepared in Example 1 and LT-FMNO prepared in Comparative Example 2 are shown.

[0030] Figure 12 Cyclic performance at 10C for LT-NFM prepared in Example 1 and LT-FMNO prepared in Comparative Example 2. Detailed Implementation

[0031] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0032] To address the shortcomings of the existing technologies, the present invention aims to provide an O3-phase sodium-ion battery layered oxide cathode material, its preparation method, and its application. This invention prepares an O3-phase sodium-ion battery layered oxide cathode material with uniform crystallization, stable structure, and high utilization of active sites, thus solving multiple problems such as sluggish kinetics, harmful phase transitions, and interface instability.

[0033] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in Examples 1 to 5, preferred embodiments are described to avoid redundancy. However, this invention is not limited to these, but can be implemented in other ways within the scope of the technical solutions defined in the appended claims. All raw materials, reagents, instruments, and equipment used in the following embodiments of this invention can be purchased commercially or prepared using existing methods.

[0034] The following detailed description, in conjunction with embodiments of the present invention and accompanying drawings, provides a clear and complete illustration of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] The formulas for the layered oxide cathode materials of O3-phase sodium-ion batteries prepared in the following examples are all Na a Ni b Fe c Mn d M1 e M2 f O 2 , where 0.8≤ a ≤0.88, 0.25≤ b ≤0.35, 0.05≤ c ≤0.15, 0.30≤ d ≤0.45, 0.05≤ e ≤0.10, 0.15≤ f≤0.30, M1 is Li, M2 is Ti.

[0036] Example 1 The chemical formula of a layered oxide cathode material for O3-phase sodium-ion batteries is Na. 0.86 Ni 0.32 Li 0.08 Fe 0.1 Mn 0.3 Ti 0.2 O 2 .

[0037] The preparation method of this O3 phase sodium-ion battery layered oxide cathode material includes the following steps: Sodium carbonate, nickel carbonyl, ferric oxide, manganese dioxide, lithium carbonate, and titanium dioxide were used as raw materials and vacuum dried at 120°C for 8 hours to remove adsorbed water. Then, each raw material was precisely weighed according to the stoichiometric ratio of the chemical formula, with sodium carbonate in 7% excess (to compensate for sodium volatilization at high temperature) and lithium carbonate in 5% excess to ensure the Li... + The carbonyl nickel was fully doped with a particle size of 20nm~50nm. The weighed raw material was added to a planetary ball mill, with anhydrous ethanol as the dispersant, a ball-to-material ratio of 10:1, a rotation speed of 400r / min, and a ball milling time of 12h to obtain a ball mill slurry. The ball milled slurry was then dried in an 80℃ forced-air drying oven for 12h and passed through a 200-mesh sieve to obtain the raw material to be processed with a particle size of 50μm~100μm.

[0038] The raw material to be processed was used in a tableting mold with an inner diameter of 12 mm. Each filling amount was 400 mg, and a pressure of 20 MPa was applied. The mixture was pressed for 10 minutes to obtain the blank to be processed.

[0039] The blank to be processed is subjected to two-stage sintering. In the low-temperature pre-sintering, the temperature is raised to 450°C at a rate of 2°C / min in air atmosphere and held for 6 hours. In the high-temperature sintering, the temperature is raised to 900°C at a rate of 3°C / min and held for 15 hours. After calcination, gradient cooling is performed. First, the temperature is lowered to 300°C at a rate of 5°C / min, and then the material is placed in an argon atmosphere to cool naturally to room temperature. The cooled bulk material is then crushed and passed through a 200-mesh sieve to obtain O3 phase sodium-ion battery layered oxide cathode material, denoted as LT-NFM.

[0040] Example 2 The chemical formula of a layered oxide cathode material for O3-phase sodium-ion batteries is Na. 0.86 Ni 0.32 Li 0.08 Fe 0.1 Mn 0.3 Ti 0.2 O 2 .

[0041] The preparation method of this O3 phase sodium-ion battery layered oxide cathode material includes the following steps: Sodium carbonate, nickel carbonyl, ferric oxide, manganese dioxide, lithium carbonate, and titanium dioxide were used as raw materials and vacuum dried at 120°C for 8 hours to remove adsorbed water. Then, each raw material was precisely weighed according to the stoichiometric ratio of the chemical formula, with sodium carbonate in excess by 5% (to compensate for sodium volatilization at high temperature) and lithium carbonate in excess by 8% to ensure the Li... + The carbonyl nickel was fully doped with a particle size of 20nm~50nm. The weighed raw material was added to a planetary ball mill with anhydrous ethanol as the dispersant, a ball-to-material ratio of 12:1, a rotation speed of 450r / min, and a ball milling time of 10h to obtain a ball mill slurry. The ball milled slurry was then dried in an 80℃ forced-air drying oven for 12h and passed through a 200-mesh sieve to obtain the raw material to be processed with a particle size of 50μm~100μm.

[0042] The raw material to be processed was used in a tableting mold with an inner diameter of 12 mm. Each filling amount was 300 mg, and a pressure of 10 MPa was applied. The mixture was pressed for 5 minutes to obtain the blank to be processed.

[0043] The blank to be processed is subjected to two-stage sintering. In the low-temperature pre-sintering, the temperature is raised to 400℃ at a rate of 3℃ / min in air atmosphere and held for 4 hours. In the high-temperature sintering, the temperature is raised to 800℃ at a rate of 2℃ / min and held for 10 hours. After calcination, gradient cooling is performed. First, the temperature is lowered to 100℃ at a rate of 2℃ / min, and then the material is placed in an argon atmosphere to cool naturally to room temperature. The cooled bulk material is then crushed and passed through a 200-mesh sieve to obtain O3 phase sodium-ion battery layered oxide cathode material, denoted as LT-NFM.

[0044] Example 3 The chemical formula of a layered oxide cathode material for O3-phase sodium-ion batteries is Na. 0.86 Ni 0.32 Li 0.08 Fe 0.1 Mn 0.3 Ti 0.2 O 2 .

[0045] The preparation method of this O3 phase sodium-ion battery layered oxide cathode material includes the following steps: Sodium carbonate, nickel carbonyl, ferric oxide, manganese dioxide, lithium carbonate, and titanium dioxide were used as raw materials and vacuum dried at 120°C for 8 hours to remove adsorbed water. Then, each raw material was precisely weighed according to the stoichiometric ratio of the chemical formula, with sodium carbonate in 10% excess (to compensate for sodium volatilization at high temperature) and lithium carbonate in 10% excess to ensure the Li... +The carbonyl nickel was fully doped with a particle size of 20nm~50nm. The weighed raw material was added to a planetary ball mill, anhydrous ethanol was used as the dispersant, the ball-to-material ratio was 15:1, the rotation speed was 300r / min, and the ball milling time was 15h to obtain a ball mill slurry. Then the ball milled slurry was dried in an 80℃ forced-air drying oven for 12h to obtain the raw material to be processed.

[0046] The raw material to be processed was used in a tableting mold with an inner diameter of 12 mm. Each filling amount was 500 mg, and a pressure of 25 MPa was applied. The mixture was pressed for 15 minutes to obtain the blank to be processed.

[0047] The blank to be processed is subjected to two-stage sintering. In the low-temperature pre-sintering, the temperature is raised to 500°C at a rate of 5°C / min in air atmosphere and held for 3 hours. In the high-temperature sintering, the temperature is raised to 1000°C at a rate of 5°C / min and held for 20 hours. After calcination, gradient cooling is performed. First, the temperature is lowered to 200°C at a rate of 3°C / min, and then the material is placed in an argon atmosphere to cool naturally to room temperature. The cooled bulk material is then crushed and passed through a 200-mesh sieve to obtain O3 phase sodium-ion battery layered oxide cathode material, denoted as LT-NFM.

[0048] Example 4 The chemical formula of a layered oxide cathode material for O3-phase sodium-ion batteries is Na. 0.80 Ni 0.25 Li 0.05 Fe 0.05 Mn 0. 4 Ti 0.15 O 2 .

[0049] The preparation method of this O3 phase sodium-ion battery layered oxide cathode material includes the following steps: Sodium carbonate, nickel carbonyl, ferric oxide, manganese dioxide, lithium carbonate, and titanium dioxide were used as raw materials and vacuum dried at 120°C for 8 hours to remove adsorbed water. Then, each raw material was precisely weighed according to the stoichiometric ratio of the chemical formula, with sodium carbonate in 7% excess (to compensate for sodium volatilization at high temperature) and lithium carbonate in 5% excess to ensure the Li... + The carbonyl nickel was fully doped with a particle size of 20nm~50nm. The weighed raw material was added to a planetary ball mill, anhydrous ethanol was used as the dispersant, the ball-to-material ratio was 10:1, the rotation speed was 400r / min, and the ball milling time was 12h to obtain a ball mill slurry. Then the ball milled slurry was dried in an 80℃ forced-air drying oven for 12h to obtain the raw material to be processed.

[0050] The raw material to be processed was used in a tableting mold with an inner diameter of 12 mm. Each filling amount was 400 mg, and a pressure of 20 MPa was applied. The mixture was pressed for 10 minutes to obtain the blank to be processed.

[0051] The blank to be processed was sintered in two stages. In the low-temperature pre-sintering stage, the temperature was raised to 450°C at a rate of 2°C / min in air atmosphere and held for 6 hours. In the high-temperature sintering stage, the temperature was raised to 900°C at a rate of 3°C / min and held for 15 hours. After calcination, gradient cooling was performed. First, the temperature was lowered to 300°C at a rate of 5°C / min, and then the material was placed in an argon atmosphere to cool naturally to room temperature. The cooled bulk material was then crushed and passed through a 200-mesh sieve to obtain the O3 phase sodium-ion battery layered oxide cathode material, denoted as LT-NFM-1.

[0052] Example 5 The chemical formula of a layered oxide cathode material for O3-phase sodium-ion batteries is Na. 0.88 Ni 0.35 Li 0.10 Fe 0.15 Mn 0.4 5 Ti 0.3 O 2 .

[0053] The preparation method of this O3 phase sodium-ion battery layered oxide cathode material includes the following steps: Sodium carbonate, nickel carbonyl, ferric oxide, manganese dioxide, lithium carbonate, and titanium dioxide were used as raw materials and vacuum dried at 120°C for 8 hours to remove adsorbed water. Then, each raw material was precisely weighed according to the stoichiometric ratio of the chemical formula, with sodium carbonate in 7% excess (to compensate for sodium volatilization at high temperature) and lithium carbonate in 5% excess to ensure the Li... + The carbonyl nickel was fully doped with a particle size of 20nm~50nm. The weighed raw material was added to a planetary ball mill, anhydrous ethanol was used as the dispersant, the ball-to-material ratio was 10:1, the rotation speed was 400r / min, and the ball milling time was 12h to obtain a ball mill slurry. Then the ball milled slurry was dried in an 80℃ forced-air drying oven for 12h to obtain the raw material to be processed.

[0054] The raw material to be processed was used in a tableting mold with an inner diameter of 12 mm. Each filling amount was 400 mg, and a pressure of 20 MPa was applied. The mixture was pressed for 10 minutes to obtain the blank to be processed.

[0055] The blank to be processed was sintered in two stages. In the low-temperature pre-sintering stage, the temperature was raised to 450°C at a rate of 2°C / min in air and held for 6 hours. In the high-temperature sintering stage, the temperature was raised to 900°C at a rate of 3°C / min and held for 15 hours. After calcination, gradient cooling was performed. First, the temperature was lowered to 300°C at a rate of 5°C / min, and then the material was placed in an argon atmosphere to cool naturally to room temperature. The cooled bulk material was then crushed and passed through a 200-mesh sieve to obtain the O3 phase sodium-ion battery layered oxide cathode material, denoted as LT-NFM-2.

[0056] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the O3-phase sodium-ion battery layered oxide cathode material prepared in Comparative Example 1 was not Li / Ti co-doped. Its chemical formula is: Na 0.86 Ni 0.4 Fe 0.1 Mn 0.5 O 2 .

[0057] The preparation method of this O3 phase sodium-ion battery layered oxide cathode material includes the following steps: Sodium carbonate, nickel carbonyl, ferric oxide, and manganese dioxide were used as raw materials and vacuum dried at 120°C for 8 hours to remove adsorbed water. Then, each raw material was precisely weighed according to the stoichiometric ratio of the chemical formula, with sodium carbonate in 7% excess (to compensate for sodium volatilization at high temperature) and lithium carbonate in 5% excess to ensure Li... + The carbonyl nickel was fully doped with a particle size of 20nm~50nm. The weighed raw material was added to a planetary ball mill, anhydrous ethanol was used as the dispersant, the ball-to-material ratio was 10:1, the rotation speed was 400r / min, and the ball milling time was 12h to obtain a ball mill slurry. Then the ball milled slurry was dried in an 80℃ forced-air drying oven for 12h to obtain the raw material to be processed.

[0058] The raw material to be processed was used in a tableting mold with an inner diameter of 12 mm. Each filling amount was 400 mg, and a pressure of 20 MPa was applied. The mixture was pressed for 10 minutes to obtain the blank to be processed.

[0059] The blank to be processed is subjected to two-stage sintering. In the low-temperature pre-sintering, the temperature is raised to 450°C at a rate of 2°C / min in air atmosphere and held for 6 hours. In the high-temperature sintering, the temperature is raised to 900°C at a rate of 3°C / min and held for 15 hours. After calcination, gradient cooling is performed. First, the temperature is lowered to 300°C at a rate of 5°C / min, and then the material is placed in an argon atmosphere to cool naturally to room temperature. The cooled bulk material is then crushed and passed through a 200-mesh sieve to obtain layered oxide cathode material, denoted as NFM.

[0060] Comparative Example 2 The only difference between Comparative Example 1 and Example 1 is that nickel carbonyl is replaced with nickel oxide, the chemical formula of which is: Na 0.86 Ni 0.32 Li 0.08 Fe 0.1 Mn 0.3 Ti 0.2 O 2 .

[0061] The preparation method of this O3 phase sodium-ion battery layered oxide cathode material includes the following steps: Sodium carbonate, nickel oxide, ferric oxide, and manganese dioxide were used as raw materials and vacuum dried at 120℃ for 8 hours to remove adsorbed water. Then, each raw material was precisely weighed according to the stoichiometric ratio of the chemical formula, with sodium carbonate in 7% excess (to compensate for sodium volatilization at high temperature) and lithium carbonate in 5% excess to ensure Li... + The carbonyl nickel was fully doped with a particle size of 1μm~5μm. The weighed raw material was added to a planetary ball mill, anhydrous ethanol was used as the dispersant, the ball-to-material ratio was 10:1, the rotation speed was 400r / min, and the ball milling time was 12h to obtain a ball mill slurry. Then the ball milled slurry was dried in an 80℃ forced-air drying oven for 12h to obtain the raw material to be processed.

[0062] The raw material to be processed was used in a tableting mold with an inner diameter of 12 mm. Each filling amount was 400 mg, and a pressure of 20 MPa was applied. The mixture was pressed for 10 minutes to obtain the blank to be processed.

[0063] The blank to be processed is subjected to two-stage sintering. In the low-temperature pre-sintering, the temperature is raised to 450°C at a rate of 2°C / min in air atmosphere and held for 6 hours. In the high-temperature sintering, the temperature is raised to 900°C at a rate of 3°C / min and held for 15 hours. After calcination, gradient cooling is performed. First, the temperature is lowered to 300°C at a rate of 5°C / min, and then the material is placed in an argon atmosphere to cool naturally to room temperature. The cooled bulk material is then crushed and passed through a 200-mesh sieve to obtain the battery layered oxide cathode material, denoted as LT-FMNO.

[0064] All of the above Examples 1 to 5 were able to prepare O3-phase sodium-ion battery layered oxide cathode materials. The effectiveness of the preferred O3-phase sodium-ion battery layered oxide cathode material LT-NFM prepared in Example 1, the battery layered oxide cathode material NFM prepared in Comparative Example 1, and the battery layered oxide cathode material LT-FMNO prepared in Comparative Example 2 was verified.

[0065] Experimental verification (1) Structural confirmation Figure 10 The XRD refinement image of LT-NFM prepared in Example 1 of this invention is obtained by... Figure 10 It can be seen that the sample exhibits characteristic diffraction peaks at 2θ = 16–17°, 34–36°, 40–42°, and 61–63°, corresponding to the (003), (101), (104), and (110) crystal planes, respectively, consistent with the layered oxide structure of the α-NaFeO2 type O3 phase. The sharp diffraction peaks and the absence of obvious impurities indicate that the material has high crystallinity and high purity. The intensity ratio of the (003) to (104) diffraction peaks, I(003) / I(104) > 1, proves that the material is a pure phase O3 type layered structure with regular layer arrangement, which is conducive to the rapid and reversible insertion and extraction of sodium ions.

[0066] (2) Performance verification Figure 1 The first-cycle charge-discharge curves (left) and rate performance (right) of LT-NFM prepared in Example 1 and NFM prepared in Comparative Example 1 are shown. Figure 1 It can be seen that the LT-NFM prepared in Example 1 has a first-cycle discharge capacity of 130.78 mAh·g at a rate of 0.05C. -1 The first-cycle coulombic efficiency was 101.95%; the NFM prepared in Comparative Example 1, under the same test conditions (0.05C rate), had a first-cycle discharge capacity of 125.12 mAh·g. -1 The first-cycle coulombic efficiency was 118.37%. In comparison, the LT-NFM prepared in Example 1 exhibits superior sodium storage capacity and electrochemical reversibility.

[0067] Figure 2 The graph shows the cycling performance of LT-NFM prepared in Example 1 and NFM prepared in Comparative Example 1 at 10C. Figure 2 It can be seen that the LT-NFM prepared in Example 1 retains 80.23% capacity after 1100 cycles at 10C; while the NFM prepared in Comparative Example 1 only retains 57.23% capacity under the same test conditions (10C rate, 1100 cycles). The comparison shows that the LT-NFM prepared in Example 1 has significantly better cycle stability than the NFM prepared in Comparative Example 1, with a 40.19% improvement in capacity retention after 1100 cycles. This superior cycle performance indicates that the O3-type layered structure of the LT-NFM prepared in Example 1 maintains good integrity during long-term high-rate charge-discharge processes, effectively suppressing side reactions such as structural collapse and transition metal ion dissolution during sodium ion insertion / extraction, resulting in better interfacial stability and extended cycle life. This further proves that the LT-NFM prepared in Example 1 possesses superior structural stability and electrochemical reliability.

[0068] Figure 3 The graph shows the cycling performance of LT-NFM prepared in Example 1 and NFM prepared in Comparative Example 1 at 60°C and 10°C. As shown in Figure 3, after 700 cycles at 60°C and 10°C, the capacity retention of LT-NFM prepared in Example 1 still reaches 81.13%; while the capacity retention of NFM prepared in Comparative Example 1 is only 39.99% under the same test conditions (60°C, 10°C, 700 cycles). This excellent high-temperature cycling performance further proves that LT-NFM prepared in Example 1 possesses excellent structural stability and superior high-temperature electrochemical reliability, making it more suitable for practical applications under high-temperature conditions.

[0069] Figure 4The cycling performance of LT-NFM prepared in Example 1 at -20°C and 1°C is shown in the graph. Figure 4 It can be seen that the LT-NFM prepared in Example 1 still maintains a capacity retention of 82.71% after 1200 cycles at -20℃ and 1C rate. This excellent low-temperature cycling performance indicates that the LT-NFM prepared in Example 1 can effectively suppress the collapse of the O3-type layered structure and the occurrence of interfacial side reactions during long-term charge-discharge at -20℃. Even when the sodium ion diffusion rate decreases due to low temperature, it can still maintain good structural integrity and interfacial stability, reducing capacity decay. Compared with traditional O3-phase layered oxide cathode materials, the LT-NFM prepared in Example 1 has significantly improved low-temperature electrochemical reliability, effectively solving the technical pain points of short low-temperature cycle life and rapid capacity decay of traditional materials, and is more suitable for practical application requirements under low-temperature conditions.

[0070] Figure 5 The graph shows the cycling performance of the LT-NFM prepared in Example 1 of this invention and the NFM prepared in Comparative Example 1 at 10C within a voltage range of 2.0V to 4.2V. (The graph is presented in the original text.) Figure 5 It can be seen that the LT-NFM prepared in Example 1 retains a capacity of 79.76% after 1000 cycles at 2.0-4.2V and 10C rate; while the NFM prepared in Comparative Example 1 only retains a capacity of 35.8% under the same test conditions (2.0V~4.2V, 10C rate, 1000 cycles). The comparison shows that the LT-NFM prepared in Example 1 has significantly better high-voltage cycling stability than the comparative example, solving the technical pain points of short cycle life and rapid capacity decay under high voltage in traditional O3 phase layered oxide cathode materials, and providing strong support for improving the energy density of sodium-ion batteries.

[0071] Figure 6 The left image shows the GITT curves (left) of LT-NFM prepared in Example 1 and NFM prepared in Comparative Example 1, both within a voltage range of 2.0V to 4.0V, and the right image shows the calculated sodium ion diffusion coefficient. (The image is presented in the original text.) Figure 6 It can be seen that the sodium ion diffusion coefficient of the LT-NFM prepared in Example 1 is in the range of 1.6 × 10⁻⁶. -14 ~9.03×10 -13 cm²·s -1 The sodium ion diffusion coefficient of NFM prepared in Comparative Example 1 ranged from 1.6 × 10⁻⁶. -15 ~1.74×10 -13 cm²·s -1The comparison shows that the sodium ion diffusion coefficient of the LT-NFM prepared in Example 1 is generally higher, and the diffusion coefficient fluctuation is more gradual. A higher sodium ion diffusion coefficient means a faster sodium ion transport rate within the material, effectively reducing polarization during charge and discharge, and providing kinetic support for the material's excellent rate performance. The more gradual diffusion coefficient fluctuation indicates that the O3-type layered structure of the LT-NFM prepared in Example 1 is more stable during sodium ion insertion / extraction, without significant structural distortion, and can continuously provide a stable channel for sodium ion transport. This is one of the important reasons why its cycle stability (especially high-voltage cycle stability) is superior to that of the NFM prepared in Comparative Example 1. Compared to the NFM prepared in Comparative Example 1, the LT-NFM prepared in Example 1 exhibits better sodium ion transport kinetics, further confirming the rationality of its structural design and its excellent electrochemical performance.

[0072] Figure 7 The variable speed CV curve (left) and pseudocapacitive contribution (right) of the LT-NFM prepared in Example 1 of this invention in the voltage range of 2.0V to 4.0V are shown.

[0073] Figure 8 The left image shows the variable-speed CV curve and the right image shows the pseudocapacitive contribution of the NFM prepared in Comparative Example 1 of this invention within a voltage range of 2.0V to 4.0V. Figure 7 and Figure 8 It can be seen that, using variable-speed cyclic voltammetry (CV) testing, the LT-NFM prepared in Example 1 and the NFM prepared in Comparative Example 1 were tested at different scan rates. The sodium-ion storage mechanism was analyzed using the power function relationship i=aνᵇ (where i is the peak current, ν is the scan rate, and a and b are fitting constants). Combined with the pseudocapacitance contribution map, the contribution ratio of pseudocapacitance to the total capacity was quantified. The pseudocapacitance effect can significantly improve the rate performance and cycle stability of the material, which is an important performance characteristic of high-power battery materials. The test results show that the b values ​​of both the LT-NFM prepared in Example 1 and the NFM prepared in Comparative Example 1 are between 0.5 and 1.0, indicating that the sodium-ion storage process of the material is a hybrid mechanism of "diffusion control + pseudocapacitance control". Moreover, within the full scan rate range, the pseudocapacitance contribution ratio of the LT-NFM prepared in Example 1 is higher than that of the NFM prepared in Comparative Example 1. Further analysis of the pseudocapacitance contribution map shows that at high scan rates (0.6 mV·s), the pseudocapacitance contribution ratio of the LT-NFM prepared in Example 1 is higher than that of the NFM prepared in Comparative Example 1. -1At this rate, the pseudocapacitive contribution of the LT-NFM prepared in Example 1 reached 96.93%, significantly higher than the 93.55% of the NFM prepared in Comparative Example 1. These results indicate that the LT-NFM prepared in Example 1 exhibits a more significant pseudocapacitive effect. The higher pseudocapacitive contribution ratio accelerates the rapid adsorption / desorption process of sodium ions, effectively compensating for the kinetic limitations of the diffusion control process at high rates, and providing crucial support for the material's excellent high-rate performance.

[0074] Figure 9 The image shows the air stability of LT-NFM prepared in Example 1 of this invention and NFM prepared in Comparative Example 1. (The image is obtained through...) Figure 9 It can be seen that the LT-NFM prepared in Example 1 exhibited a capacity loss of only 7.5% after 7 days of storage; while the NFM prepared in Comparative Example 1 showed a capacity loss as high as 48.3% under the same storage conditions. This comparison demonstrates that the air stability of the LT-NFM prepared in Example 1 is significantly superior to that of the NFM prepared in Comparative Example 1. This excellent air stability indicates that the LT-NFM prepared in Example 1 can effectively inhibit the reaction between moisture and carbon dioxide in the air and the material, preventing the destruction of the O3-type layered structure and the formation of surface byproducts, thereby reducing capacity decay. Compared to the NFM prepared in Comparative Example 1, the LT-NFM prepared in Example 1 has stronger resistance to air erosion, which can reduce performance loss during battery production and storage, simplify the production process, reduce storage costs, and further enhance the practical application value of the LT-NFM prepared in Example 1. Combined with the excellent electrochemical performance described above, this highlights the comprehensive advantages of the experimental materials.

[0075] Figure 11 The first-cycle charge-discharge curves (left) and rate performance (right) of LT-NFM prepared in Example 1 and LT-FMNO prepared in Comparative Example 2 are shown. Figure 11 It can be seen that the LT-NFM prepared in Example 1 has a first-cycle discharge capacity of 130.78 mAh·g at a rate of 0.05C. -1 The first-cycle coulombic efficiency was 101.95%; the LT-FMNO prepared in Comparative Example 2, under the same test conditions (0.05C rate), had a first-cycle discharge capacity of 114.9 mAh·g. -1 The first-cycle coulombic efficiency was 92.66%. In comparison, the LT-NFM prepared in Example 1 exhibits superior sodium storage capacity and electrochemical reversibility.

[0076] Figure 12 This is a cycling performance graph at 10C for LT-NFM prepared in Example 1 and LT-FMNO prepared in Comparative Example 2. Figure 12It can be seen that the LT-NFM prepared in Example 1 still retains 80.23% capacity after 1100 cycles at 10C rate; while the LT-FMNO prepared in Comparative Example 2 only retains 78.88% capacity under the same test conditions (10C rate, 1100 cycles).

[0077] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing an O3-phase sodium-ion battery layered oxide cathode material, characterized in that, Includes the following steps: Weigh sodium carbonate, nickel carbonyl, ferric oxide, manganese dioxide, lithium carbonate, and titanium dioxide after vacuum heating and drying according to the stoichiometric ratio in the chemical formula, ensuring that sodium carbonate is in excess by 5% to 10% and lithium carbonate is in excess by 5% to 10%. After ball milling, drying, and grinding, the raw material to be processed is obtained, wherein the particle size of nickel carbonyl is 20nm to 50nm. The raw material to be processed is compressed into tablets to obtain the preform to be processed; The blank to be processed is heated to 400℃~500℃ in air at a heating rate of 2℃ / min~5℃ / min for the first calcination and held for 4h~6h. Then, it is heated to 800℃~1000℃ at a heating rate of 2℃ / min~5℃ / min for the second calcination and held for 10h~20h. After calcination, it is first cooled to 100℃~300℃ at a heating rate of 2℃ / min~5℃ / min, and then naturally cooled to room temperature in an argon atmosphere. After crushing and sieving, the O3 phase sodium-ion battery layered oxide cathode material is obtained.

2. The method for preparing the O3-phase sodium-ion battery layered oxide cathode material according to claim 1, characterized in that, The purity of sodium carbonate is ≥99.5%, nickel carbonyl is ≥99.9%, ferric oxide is ≥99.0%, manganese dioxide is ≥99.0%, and titanium dioxide is ≥99.0%. Anhydrous ethanol is used as the dispersant during ball milling, the ball-to-material ratio is 10~15:1, the rotation speed is 300~450 r / min, and the ball milling time is 10h~15h. The raw material to be processed is obtained by sieving after ball milling with a particle size of 50μm~100μm.

3. The method for preparing the O3-phase sodium-ion battery layered oxide cathode material according to claim 1, characterized in that, The amount of raw material to be processed during tableting is 300mg to 500mg, the tableting pressure is 10MPa to 25MPa, the tableting time is 5min to 15min, and the resulting tablet diameter is 12mm.

4. The O3-phase sodium-ion battery layered oxide cathode material prepared by the method for preparing O3-phase sodium-ion battery layered oxide cathode material according to any one of claims 1 to 3.

5. The O3-phase sodium-ion battery layered oxide cathode material according to claim 4, characterized in that, The chemical formula is Na. a Ni b Fe c Mn d M1 e M2 f O 2 , where 0.8≤ a ≤0.88, 0.25≤ b ≤0.35, 0.05≤ c ≤0.15, 0.30≤ d ≤0.45, 0.05≤ e ≤0.10, 0.15≤ f ≤0.30, M1 is Li, M2 is Ti.

6. The O3-phase sodium-ion battery layered oxide cathode material according to claim 4, characterized in that, O3-phase sodium-ion battery layered oxide cathode material exhibits an initial discharge capacity ≥130 mAh·g at a 0.05C rate within a voltage range of 2.0V to 4.2V. -1 Capacity at 10C rate ≥ 98mAh・g -1 .

7. The O3-phase sodium-ion battery layered oxide cathode material according to claim 4, characterized in that, The O3-phase sodium-ion battery layered oxide cathode material retains ≥82% capacity after 1200 cycles at -20℃ and 1C; ≥81% capacity after 700 cycles at 60℃ and 10C; ≥80% capacity after 1100 cycles at 10C; and ≥79% capacity after 1000 cycles at 2.0V~4.2V.

8. The application of the O3 phase sodium-ion battery layered oxide cathode material according to any one of claims 4 to 7 in sodium-ion batteries.

9. A positive electrode sheet, characterized in that, Including the O3 phase sodium-ion battery layered oxide cathode material as described in any one of claims 4 to 7.

10. A sodium-ion battery, characterized in that, It includes a negative electrode, an electrolyte, and a positive electrode as described in claim 9.

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