Positive electrode material containing p2-type phase microdomain, sodium-ion battery, and preparation method therefor
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-01-14
- Publication Date
- 2026-08-13
Smart Images
Figure CN2026072563_13082026_PF_FP_ABST
Abstract
Description
Positive electrode material containing P2-type phase microregions, sodium-ion battery and its preparation method Technical Field
[0001] This disclosure relates to a positive electrode material containing P2-type phase microregions, a sodium-ion battery, and a method for preparing the positive electrode material. Background Technology
[0002] In existing applications using O3 as the positive electrode material for sodium-ion batteries, the close-packed structure of O3 limits the ion diffusion efficiency and ion conductivity of sodium ions. Furthermore, the structural transformation of O3 during charge and discharge may lead to decreased structural stability. In addition, O3 has poor air sensitivity and exhibits numerous side reactions with the electrolyte at high voltages, thus resulting in poor interfacial stability when used as a positive electrode material.
[0003] Therefore, how to provide positive electrode materials that can improve sodium ion diffusion capacity and structural stability is a topic that those skilled in the art are actively researching. Summary of the Invention
[0004] Some embodiments of this disclosure provide a positive electrode material comprising P2-type phase microregions, including an O3-type substrate and P2-type phase microregions located on the surface of the O3-type substrate. The O3-type substrate has an O3-type layered structure, comprising O3-type material and oxygen vacancies replacing oxygen elements in the O3-type material, wherein the molecular formula of the O3-type substrate is Na. x MO 2-y □ y □ represents oxygen vacancies, 0.7≤x≤1, 10 -10 ≤y≤0.2, M is one or more of lithium (Li), magnesium (Mg), aluminum (Al), vanadium (V), titanium (Ti), chromium (Cr), iron (Fe), nickel (Ni), cobalt (Co), manganese (Mn), copper (Cu), zinc (Zn), strontium (Sr), zirconium (Zr), lanthanum (La), and bismuth (Bi). The P2-type phase microregions exhibit a P2-type layered structure. By designing oxygen vacancies that can enhance the diffusion rate of sodium ions and the P2-type phase microregions, the electrochemical performance of the cathode electrode material can be improved (e.g., extending the number of usable cycles) and the stability of air storage can be enhanced.
[0005] In some embodiments, oxygen vacancies are located inside, on the outer edge, or in combination thereof, of the O3-type material.
[0006] In some implementations, the O3 type host has a hexagonal crystal system and belongs to space group R-3m.
[0007] In some embodiments, the P2-type phase microregion contains Na xMO2 is a P2 material where 0.5≤x≤0.7 and M is one or more of lithium, magnesium, aluminum, vanadium, titanium, chromium, iron, nickel, cobalt, manganese, copper, zinc, strontium, zirconium, lanthanum, and bismuth.
[0008] In some embodiments, the O3 type body and the P2 type phase microregion are respectively based on the O3 type body. <006> Crystal planes and P2-type phase micro-regions <106> The crystal planes are adjacent to each other.
[0009] In some embodiments, when electron paramagnetic resonance (EPR) is used to determine the concentration of oxygen air in the positive electrode material, the concentration is 1.0 x 10⁻⁶. -7 Moles per liter to 1.0 x 10 -6 Between moles per liter.
[0010] In some implementations, when the positive electrode material is detected using the Galvanostatic Intermittent Titration Technique (GITT), the sodium ion diffusion coefficient of the positive electrode material is 1.0 x 10⁻⁶. -10 square centimeters per second to 1.6 x 10 -9 Between square centimeters per second.
[0011] In some implementations, when the four-point probe method is used to detect the positive electrode material, the electronic conductivity of the positive electrode material is 1.0 x 10⁻⁶. -4 millisiemens / cm to 9.0 x 10 - 3 Between millisiemens per centimeter.
[0012] Some embodiments of this disclosure provide a sodium-ion battery, including: a negative electrode, a positive electrode, a separator, and a sodium-ion battery electrolyte. The positive electrode comprises the aforementioned positive electrode material. The separator is disposed between the negative electrode and the positive electrode.
[0013] Some embodiments of this disclosure provide a method for preparing a positive electrode material, comprising: providing a metal oxide and a sodium-containing compound, wherein the metal in the metal oxide comprises one or more of lithium, magnesium, aluminum, vanadium, titanium, chromium, iron, nickel, cobalt, manganese, copper, zinc, strontium, zirconium, lanthanum, and bismuth; mixing the metal oxide and the sodium-containing compound to obtain a mixture; performing a first heat treatment in an oxygen or air atmosphere to obtain a primary sinter; and performing a second heat treatment on the primary sinter in an inert atmosphere to obtain a secondary sinter, thereby obtaining a positive electrode material, wherein the positive electrode material comprises an O3-type host with oxygen vacancies and P2-type phase microregions located on the surface of the O3-type host. By performing a second sintering with an inert gas, oxygen vacancies and P2-type phase microregions can be formed, which can improve the electrochemical performance (e.g., extend the number of usable cycles) and improve the air storage stability of the prepared positive electrode material.
[0014] In some embodiments, the step of mixing the metal oxide and the sodium-containing compound includes: according to the molecular formula Na of the O3-type material to be generated in the positive electrode material. x MO2 regulates the molar ratio of metal oxides to sodium-containing compounds, ensuring that the molar ratio of metal in the metal oxide to sodium in the sodium-containing compound is consistent with the molecular formula Na. x In MO2, the molar ratio of Na to M is the same, where 0.7 ≤ x ≤ 1, and M is one or more of lithium, magnesium, aluminum, vanadium, titanium, chromium, iron, nickel, cobalt, manganese, copper, zinc, strontium, zirconium, lanthanum, and bismuth.
[0015] In some embodiments, the sodium-containing compound includes sodium carbonate, sodium hydroxide, sodium acetate, sodium fluoride, or combinations thereof.
[0016] In some embodiments, the first heating treatment includes: heating to 600°C to 1000°C for 10 to 20 hours at a heating rate of 1°C / min to 10°C / min; and cooling at a cooling rate of 1°C / min to 3°C / min.
[0017] In some embodiments, after the first heat treatment, the primary sinter is ground and crushed until the particle size of individual particles in the primary sinter is 1 nanometer to 10 micrometers.
[0018] In some embodiments, the inert atmosphere comprises nitrogen, argon, helium, neon, or combinations thereof.
[0019] In some embodiments, the second heating treatment includes: heating to 300°C to 800°C for 2 to 10 hours at a heating rate of 1°C / min to 10°C / min; and cooling at a cooling rate of 1°C / min to 3°C / min.
[0020] In some embodiments, after the second heat treatment, the secondary sintered material is broken up such that the individual particles in the secondary sintered material have a particle size of 1 nanometer to 10 micrometers. Attached Figure Description
[0021] To make the above and other objects, features, advantages and embodiments disclosed herein more apparent and understandable, the accompanying drawings are described below:
[0022] Figure 1 is a flowchart of a method for preparing a positive electrode material according to some embodiments of the present disclosure.
[0023] Figure 2A shows the appearance of the primary sintered product prepared according to point 1 of Example 1 under an electron microscope.
[0024] Figure 2B shows the appearance of the secondary sintered product prepared according to point 1 of Example 1 under an electron microscope.
[0025] Figure 2C shows the appearance of the boundary region between the O3 type host and the P2 type phase microregion in the secondary sintered material prepared according to point 1 of Example 1 under an electron microscope, and the crystal plane types of the O3 type host and the P2 type phase microregion at the boundary region are marked.
[0026] Figure 2D shows the results of the half-cell electrochemical property test performed according to point 2 of Example 1. The materials used for the positive electrode are either the primary sintered material or the secondary sintered material prepared in point 1 of Example 1.
[0027] Figure 3A shows the appearance of the primary sintered product prepared according to point 1 of Example 2 under an electron microscope.
[0028] Figure 3B shows the appearance of the secondary sintered product prepared according to point 1 of Example 2 under an electron microscope.
[0029] Figure 3C shows the results of the half-cell electrochemical property test performed according to point 2 of Example 2. The positive electrode is made of either the primary sintered material or the secondary sintered material prepared in point 1 of Example 2. Detailed Implementation
[0030] The following describes several embodiments of this disclosure with reference to the accompanying drawings. For clarity, many practical details will be described in the following description. However, it should be understood that these practical details should not be used to limit this disclosure. That is, in some embodiments of this disclosure, these practical details are not essential and therefore should not be used to limit this disclosure. In addition, for the sake of simplicity, some conventional structures and components will be shown in the drawings in a simple schematic manner. Furthermore, for the reader's convenience, the dimensions of the components in the drawings are not drawn to scale.
[0031] It should be understood that relative terms such as “down” or “bottom” and “up” or “top” may be used herein to describe the relationship of one element to another, as illustrated in the accompanying drawings. It should be understood that relative terms are intended to include different orientations of the device beyond those shown in the figures. For example, if a device in one of the figures is flipped, an element described as being “down” to other elements will be oriented “up” to other elements. Thus, the exemplary term “down” can include both “down” and “up” orientations, depending on the specific orientation of the figure. Similarly, if a device in one of the figures is flipped, an element described as being “down” or “below” to other elements will be oriented “above” to other elements. Thus, the exemplary term “down” or “below” can include both “up” and “down” orientations.
[0032] This document will first describe a method for preparing a positive electrode material. Specifically, please refer to Figure 1, which shows a flow chart of a method 100 for preparing a positive electrode material containing P2-type phase microregions according to some embodiments of this disclosure, including steps S110 to S140. In step S110, a metal oxide and a sodium-containing compound are provided, wherein the metal in the metal oxide includes one or more of lithium, magnesium, aluminum, vanadium, titanium, chromium, iron, nickel, cobalt, manganese, copper, zinc, strontium, zirconium, lanthanum, and bismuth. In step S120, the metal oxide and the sodium-containing compound are mixed to obtain a mixture. In step S130, a first heat treatment is performed in an oxygen or air atmosphere to obtain a primary sintered product. In step S140, a second heat treatment is performed on the primary sintered product in an inert atmosphere to obtain a secondary sintered product. The above steps will be described sequentially in the following description.
[0033] It is worth emphasizing that in some embodiments of this disclosure, after obtaining a primary sintered material with an O3-type structure through a first heat treatment, a second sintering is performed using an inert gas. This step is designed to further form oxygen vacancies and P2-type phase microregions (P2-type layered structure) in the primary sintered material after the formation of the O3-type body. By forming oxygen vacancies, the migration efficiency and electronic conductivity of sodium ions can be improved, while the P2-type phase microregions can improve the migration efficiency and interface stability of sodium ions, thereby improving the cycle stability of the battery (for example, after multiple cycles, the discharge capacitance and capacity retention can be maintained at a better level).
[0034] It is also worth emphasizing that, compared to the liquid heating method, the solid co-firing method produces sintered materials with O3 as the main component, which can avoid the destruction of the crystal structure in the liquid solution, thereby improving the structural integrity of the finished product.
[0035] In some embodiments, the metal oxide comprises Ni 0.45 Mn 0.4 Cu0.05 Ti 0.1 O x Ni 0.5 Mn 0.5 O x Sodium compounds may be, or combinations thereof. In some embodiments, the sodium-containing compound comprises sodium carbonate, sodium hydroxide, sodium acetate, sodium fluoride, or combinations thereof. Those skilled in the art can select appropriate metal oxides and sodium-containing compounds according to the actual application requirements.
[0036] In some embodiments, step S120, which involves mixing the metal oxide and the sodium-containing compound, includes: [The text abruptly ends here, so the translation stops.] x MO2 regulates the molar ratio of metal oxides to sodium-containing compounds, ensuring that the molar ratio of metal in the metal oxide to sodium in the sodium-containing compound is consistent with the molecular formula Na. x In MO2, the molar ratio of Na to M is the same, where 0.7 ≤ x ≤ 1, and M is one or more of lithium, magnesium, aluminum, vanadium, titanium, chromium, iron, nickel, cobalt, manganese, copper, zinc, strontium, zirconium, lanthanum, and bismuth.
[0037] In some embodiments, in step S130, the first heating treatment includes: heating to 600°C to 1000°C (600°C, 700°C, 800°C, 900°C, 10°C, or any value in the aforementioned range) at a heating rate of 1°C / min to 10°C / min (1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, or any value in the aforementioned range) for 10 hours to 20 hours (10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, or any value in the aforementioned range); and cooling at a cooling rate of 1°C / min to 3°C / min (1°C / min, 2°C / min, 3°C / min, or any value in the aforementioned range). Too rapid a heating rate, too high or too low a heating temperature, too long or too short a heating time, or too fast or too slow a cooling rate may reduce the structural integrity of the sintered material.
[0038] In some embodiments, after the first heat treatment, the primary sinter is ground and crushed until the particle size of individual particles in the primary sinter is 1 nanometer to 10 micrometers (e.g., 1 nanometer, 1 x 10⁻⁶). 2 Nano, 2x10 2 Nano, 3x10 2 Nano, 4x10 2 Nano, 5x10 2 Nano, 6x10 2 Nano, 7x10 2 Nano, 8x10 2Nano, 9x10 2 (Number, 1 micrometer, 5 micrometer, 10 micrometer, or any value within the aforementioned range). By controlling the upper limit of the particle size of the primary sinter applied to the subsequent step S140, the uniformity of the primary sinter, which serves as a reactant, is ensured, thereby improving the structural stability of the sintered positive electrode material.
[0039] In some embodiments, the inert atmosphere includes nitrogen, argon, helium, neon, or combinations thereof. By performing a second sintering in the inert gas, oxygen vacancies can be further generated in or on the surface of the sodium-containing O3 material formed in the first sintering, and a P2 microphase region can be formed on the surface of the sodium-containing O3 material, further improving the electrochemical performance when applied to batteries.
[0040] In some embodiments, in step S140, the second heating treatment includes: heating to 300°C to 800°C (300°C, 400°C, 500°C, 6°C, 7°C, 8°C, 9°C, 10°C, or any value in the aforementioned range) at a heating rate of 1°C / minute to 10°C / minute (1°C / minute, 2°C / minute, 3°C / minute, 4°C / minute, 5°C / minute, 6°C / minute, 7°C / minute, 8°C / minute, 9°C / minute, 10°C / minute, or any value in the aforementioned range) for 2 hours to 10 hours (2 hours, 4 hours, 6 hours, 8 hours, 10 hours, or any value in the aforementioned range); and cooling at a cooling rate of 1°C / minute to 3°C / minute (1°C / minute, 2°C / minute, 3°C / minute, or any value in the aforementioned range). Excessive heating rate, excessively high or low heating temperature, excessively long or short heating time, or excessively fast or slow cooling rate may reduce the structural integrity of the sintered secondary sintered material. For example, the oxygen vacancy content may be lower than expected, P2 phase microregions may fail to form smoothly, or the crystal structure may be damaged—all undesirable structural changes. It is worth emphasizing that by setting an upper temperature limit for the second heating treatment, it is possible to avoid the precipitation of some elements in the material due to decreased solid solubility caused by higher temperatures in an inert atmosphere. Therefore, setting an upper temperature limit can improve the structural integrity of the secondary sintered material.
[0041] In some embodiments, after the second heat treatment step, the secondary sintered material is crushed such that the individual particles in the secondary sintered material have a particle size of 1 nanometer to 10 micrometers (e.g., 1 nanometer, 1 x 10⁻⁶). 2 Nano, 2x10 2 Nano, 3x10 2 Nano, 4x10 2 Nano, 5x10 2 Nano, 6x10 2 Nano, 7x10 2 Nano, 8x102 Nano, 9x10 2 (Number, 1 micrometer, 5 micrometer, 10 micrometer, or any value within the aforementioned range). By controlling the upper limit of the particle size applied to the positive electrode material, the uniformity of the positive electrode material is ensured, structural stability is maintained, and thus the performance stability when applied to a battery is improved.
[0042] In some embodiments, a positive electrode material is obtained by secondary sintering in step S140, wherein the positive electrode material comprises an O3-type substrate with oxygen vacancies and P2-type phase microregions located on the surface of the O3-type substrate. The presence of oxygen vacancies can improve sodium ion diffusion efficiency and electronic conductivity. The P2-type phase microregions, due to their good chemical stability, excellent structural stability, and good air storage stability, can improve the performance of the positive electrode material in batteries (e.g., extending the number of usable cycles) and air storage stability.
[0043] In some embodiments, the O3-type host has an O3-type layered structure, comprising O3-type material and oxygen vacancies replacing oxygen elements in the O3-type material, wherein the molecular formula of the O3-type host is Na. x MO 2- y □ y □ represents oxygen vacancies, 0.7≤x≤1 (0.7, 0.8, 0.9, 1, or any value in the aforementioned range), 10 -10 ≤y≤0.2(10 -10 10 -9 10 -8 10 -7 10 -6 10 -5 10 -4 10 -3 0.01, 0.1, 0.15, 0.2, or any value in the aforementioned range), where M is one or more of lithium, magnesium, aluminum, vanadium, titanium, chromium, iron, nickel, cobalt, manganese, copper, zinc, strontium, zirconium, lanthanum, and bismuth.
[0044] In some embodiments, oxygen vacancies are located inside the O3 type material, at the outer edge (e.g., on the surface of the adjacent P2 type phase microregion of the O3 type body, or on the surface of the O3 type body that is directly exposed to the outside), or a combination thereof.
[0045] In some embodiments, the O3-type material contains NaNi 0.45 Mn 0.4 Cu 0.05 Ti 0.1 O 2-y □ y NaNi 0.5 Mn 0.5 O2-y □ y , or combinations thereof, of which 10 -10 ≤y≤0.2. In some embodiments, the O3 type host has a hexagonal crystal system and belongs to space group R-3m.
[0046] In some embodiments, the P2-type phase microregions are located on the surface of the O3-type matrix and exhibit a P2-type layered structure, wherein the P2-type phase microregions contain Na x MO2 is a P2 material, where 0.5≤x≤0.7 (0.5, 0.6, 0.7, or any value in the aforementioned range), and M is one or more of lithium, magnesium, aluminum, vanadium, titanium, chromium, iron, nickel, cobalt, manganese, copper, zinc, strontium, zirconium, lanthanum, and bismuth.
[0047] In some embodiments, multiple P2-type phase microregions are distributed on a portion of the surface of the O3-type host, and a portion of the surface of the O3-type host is exposed. In some embodiments, the P2-type phase microregions cover the entire surface of the O3-type host. In some embodiments, the O3-type host and the P2-type phase microregions are respectively positioned on the surface of the O3-type host. <006> Crystal planes and P2-type phase micro-regions <106> The crystal planes are adjacent to each other.
[0048] In some embodiments, the positive electrode material provided by some embodiments of this disclosure improves oxygen vacancy concentration, sodium ion diffusion coefficient, and electronic conductivity compared to existing materials.
[0049] In some embodiments, when electron paramagnetic resonance (EPR) is used to determine the concentration of oxygen air in the positive electrode material, the concentration is 1.0 x 10⁻⁶. -7 Moles per liter to 1.0 x 10 -6 Between moles per liter, for example, 1.0 x 10⁻⁶. -7 Moles per liter, 2.0 x 10 -7 Moles per liter, 4.0 x 10 -7 Moles per liter, 6.0 x 10 - 7 Moles per liter, 8.0 x 10 -7 Moles per liter, 1.0 x 10 -6 Moles per liter, or any value within the aforementioned range. In some embodiments, when the positive electrode material is detected using a galvanostatic step titration (GITT) test, the sodium ion diffusion coefficient of the positive electrode material is 1.0 x 10⁻⁶. -10 square centimeters per second to 1.6 x 10 - 9 Between square centimeters per second, for example, 1.0 x 10⁻⁶. -10 square centimeters per second, 2.0 x 10 -10 square centimeters per second, 4.0 x 10- 10 square centimeters per second, 6.0 x 10 -10 square centimeters per second, 8.0 x 10 -10 square centimeters per second, 1.0 x 10 -9 square centimeters per second, 1.6 x 10 -9 Square centimeters per second, or any value within the aforementioned range. In some embodiments, when the four-probe method is used to detect the positive electrode material, the electronic conductivity of the positive electrode material is 1.0 x 10⁻⁶. -4 millisiemens / cm to 9.0 x 10 -3 Between millisiemens per centimeter, for example 1.0 x 10⁻⁶. -4 millisiemens / cm, 2.0 x 10 -4 millisiemens / cm, 4.0 x 10 -4 millisiemens / cm, 6.0 x 10 -4 millisiemens / cm, 8.0 x 10 -4 millisiemens / cm, 1.0 x 10 -3 millisiemens / cm, 3.0 x 10 -3 millisiemens / cm, 6.0 x 10 -3 millisiemens / cm, 9.0 x 10 -3 millisiemens per centimeter, or any value within the aforementioned range.
[0050] Some embodiments of this disclosure also provide a sodium-ion battery, including a negative electrode, a positive electrode, a separator disposed between the negative electrode and the positive electrode, and a sodium-ion battery electrolyte. In some embodiments, the negative electrode may include a negative electrode material layer and a negative electrode current collector, wherein the negative electrode material layer may include, for example, carbon (e.g., hard carbon), metal oxides, alloys, or combinations thereof, and the negative electrode current collector may be, for example, copper foil. In some embodiments, the positive electrode may include a positive electrode material layer and a positive electrode current collector, wherein the positive electrode material layer includes a metal oxide material (see the foregoing description of positive electrode materials for details).
[0051] The features and effects of this disclosure will be described in more detail below with reference to comparative examples and embodiments. It should be understood that, without departing from the scope of this disclosure, the materials used, their content and proportion, processing details, and processing procedures can be appropriately modified based on ordinary knowledge in the art. Therefore, this disclosure should not be interpreted as limiting by the embodiments described below.
[0052] <Example 1> Positive Electrode Material 1
[0053] 1. Preparation of positive electrode materials
[0054] (1) O3 phase mixing: The target molecular formula is set as NaNi 0.45 Mn0.4 Cu 0.05 Ti 0.1 O 2-y □ y (10 - 10 ≤y≤0.2), weigh out the metal oxide (Ni 0.45 Mn 0.4 Cu 0.05 Ti 0.1 O x The metal oxide and sodium-containing compound (sodium carbonate) are mixed in such a way that the molar ratio of metal in the metal oxide to sodium in the sodium-containing compound is 1:1. The metal oxide and sodium-containing compound are then placed in a mixer and mixed evenly to obtain a mixture.
[0055] (2) Primary sintering: The mixture is placed in a box furnace under an oxygen atmosphere and heated to 920°C at a heating rate of 3°C / min for 12 hours, then cooled to room temperature (approximately 25°C) at a cooling rate of 1°C / min to obtain an initial primary sintered material (O3 material) with an O3-type layered structure. Next, the initial primary sintered material is ground and crushed and passed through a 300-mesh sieve (the particle size after sieving is at least less than 10 micrometers) to obtain a primary sintered material (NaNi). 0.45 Mn 0.4 Cu 0.05 Ti 0.1 The appearance of the primary sintered material under an electron microscope (see electron microscope image 210 in Figure 2A) shows a layered structure, with some particles smaller than 5 micrometers in diameter. It is understood that the oxygen sintering used here is to match the synthesis conditions of the selected target molecular formula. Those skilled in the art can select a suitable gas for sintering based on the desired target molecular formula (e.g., air can be used directly if specific elements are included), and the atmospheric conditions during primary sintering are not limited to this.
[0056] (3) Secondary sintering: The mixture is placed in an argon-filled box furnace and heated to 800°C at a heating rate of 5°C / min for 3 hours, then cooled to room temperature (approximately 25°C) at a cooling rate of 3°C / min. This process creates oxygen vacancies within or on the surface of the O3-type matrix formed during the primary sintering, and forms P2 phase microregions on the surface of the O3-type matrix (which is primarily composed of O3-type materials), thus obtaining the initial secondary sintered material. Next, the initial secondary sintered material is subjected to airflow crushing and then passed through a 200-mesh sieve (the particle size after sieving is at least less than 10 micrometers) to obtain the secondary sintered material (molecular formula NaNi). 0.45 Mn 0.4 Cu 0.05 Ti 0.1 O 2-y □ y 10 of them -10≤y≤0.2, where the molecular formula of the original O3-type material without oxygen vacancies is NaNi 0.45 Mn 0.4 Cu 0.05 Ti 0.1 For the electron microscope image 220 in Figure 2B, the O2 structure is shown, with some particles smaller than 10 micrometers in diameter. Further analysis of the secondary sintered material revealed that the O3-type matrix exhibits a hexagonal crystal system, belonging to space group R-3m (space group number 166).
[0057] Meanwhile, Figure 2C shows an electron microscope image (Figure 230) of the boundary region between the O3-type matrix and the P2-type phase micro-region in the secondary sintered material, under an electron microscope. The O3 material of the O3-type matrix at the boundary is... <006> The crystal planes were analyzed and measured, revealing that the particle size at the marked location is approximately 0.263 nanometers. The P2-type phase micro-regions at the interface exhibit P2 material. <106> The crystal planes were measured and revealed, and the particle size at the marked location was approximately 0.149 nanometers.
[0058] 2. Electrical testing of half-cell
[0059] In this experimental example, the positive electrode was either the primary sintered material or the secondary sintered material from point 1 of Example 1, the negative electrode was metallic sodium, a 2032 battery case was selected, and Whatman GF / F glass fiber was used as the separator. A coin cell was assembled in an environment where the water and oxygen content were both below 0.1 ppm, and the electrochemical properties of the charge-discharge rate at a set voltage range of 2 volts to 4.2 volts were tested. For detailed results, please refer to Figure 240 of Figure 2D.
[0060] As shown in Figure 240, compared to using a single-sintered material (sintered only once without inert gas sintering) as the positive electrode material, when a double-sintered material (sintered sequentially with oxygen and inert gas) is used as the positive electrode material, the discharge specific capacitance remains at a higher level. In other words, using a double-sintered material as the positive electrode material can improve the discharge capacitance of the half-cell after several cycles and improve cycle stability.
[0061] <Example 2> Positive Electrode Material 2
[0062] 1. Preparation of positive electrode materials
[0063] (1) O3 phase mixing: The target molecular formula is set as NaNi 0.5 Mn 0.5 O 2-y □ y (10 -10 ≤y≤0.2), weigh out the metal oxide (Ni 0.5 Mn0.5 O x The metal oxide and sodium-containing compound (sodium carbonate) are mixed in such a way that the molar ratio of metal in the metal oxide to sodium in the sodium-containing compound is 1:1. The metal oxide and sodium-containing compound are then placed in a mixer and mixed evenly to obtain a mixture.
[0064] (2) Primary sintering: The mixture was placed in a box furnace under an oxygen atmosphere and heated to 850°C at a heating rate of 5°C / min for 15 hours, then cooled to room temperature (approximately 25°C) at a cooling rate of 2°C / min to obtain an initial primary sintered material (O3 material) with an O3-type layered structure. Next, the initial primary sintered material was ground and crushed and passed through a 300-mesh sieve to obtain a primary sintered material (NaNi). 0.5 Mn 0.5 O2), the appearance of the primary sintered material under an electron microscope, please refer to the electron microscope image 310 in Figure 3A, which shows a layered structure, with individual particles having a diameter of less than 2 to 3 micrometers.
[0065] (3) Secondary sintering: The mixture is placed in an argon-filled box furnace and heated to 800°C at a heating rate of 5°C / min for 3 hours, then cooled to room temperature (approximately 25°C) at a cooling rate of 3°C / min to form oxygen vacancies and P2 phase microregions, obtaining the initial secondary sintered material. Next, the initial secondary sintered material is subjected to airflow crushing and then passed through a 200-mesh sieve (the particle size after screening is at least less than 10 micrometers) to obtain the secondary sintered material (NaNi). 0.5 Mn 0.5 O2 (molecular formula is NaNi) 0.5 Mn 0.5 O 2-y □ y 10 -10 ≤y≤0.2, where the molecular formula of the original O3-type material without oxygen vacancies is NaNi 0.5 Mn 0.5 For the electron microscope field of view, please refer to the electron microscope image 320 in Figure 3B. It shows a layered structure, with individual particles having a diameter of less than 2 to 3 micrometers.
[0066] It is understandable that the structural differences between the secondary sintered products obtained in Examples 1 and 2 lie in the different metal elements and molecular formulas used, but the general structural types of each layer and the main characteristics (P2 phase microregions and oxygen vacancies, etc.) are basically similar.
[0067] 2. Electrical testing of half-cell
[0068] In this experimental example, the positive electrode was either the primary sintered material or the secondary sintered material from point 1 of Example 2, the negative electrode was metallic sodium, a 2032 type battery case was selected, and Whatman GF / F glass fiber was used as the separator. Coin half-cells were assembled in an environment where the water and oxygen content were both below 0.1 ppm, and the electrochemical properties of the charge-discharge rate at a set voltage range of 2 volts to 4.2 volts were tested. For detailed results, please refer to Figure 3C, Figure 330.
[0069] As shown in Figure 330, compared to using a single-sintered material (sintered only once without inert gas sintering) as the positive electrode material, when a double-sintered material (sintered sequentially with oxygen and inert gas) is used as the positive electrode material, the discharge specific capacitance remains at a high level. In other words, using a double-sintered material as the positive electrode material can improve the discharge capacitance of the half-cell after several cycles and improve cycle stability.
[0070] <Comprehensive Performance Evaluation>
[0071] To further analyze the differences between the primary and secondary sintered materials provided in the embodiments of this disclosure, and the differences between the secondary sintered materials provided in the embodiments of this disclosure and the positive electrode materials of commercially available batteries, the following performance integration and comparison are further performed.
[0072] 1. Physicochemical properties of positive electrode materials
[0073] (1) Oxygen vacancy content
[0074] To determine the changes in oxygen vacancy in the sintered products obtained from different sintering steps in each embodiment, the primary and secondary sintered products obtained at point 1 of Example 1, and the primary and secondary sintered products obtained at point 1 of Example 2 were selected as test groups. The spin electron molar concentration in each test group was determined by electron paramagnetic resonance (EPR) to obtain the oxygen vacancy concentration in each test group. The results are summarized in Table 1 below.
[0075] Table 1
[0076] Table 1 shows that, regardless of Example 1 or Example 2, the oxygen vacancy concentration in the secondary sintered product (obtained by inert gas sintering during a second heating process) is at least three times higher than that in the primary sintered product. Therefore, the oxygen vacancy content can be significantly increased by the second inert gas sintering step.
[0077] (2) Sodium ion diffusion coefficient and electronic conductivity
[0078] Since the content of oxygen vacancies theoretically improves the diffusion rate of sodium ions and enhances conductivity, and the presence of P2 phase microregions should also help to improve the diffusion rate of sodium ions and improve interface stability, the sodium ion diffusion coefficient and electronic conductivity of the secondary sintered products of Examples 1 and 2 were further measured.
[0079] Specifically, the sodium ion diffusion coefficient was determined using a Galvanostatic Intermittent Titration Technique (GITT). Electronic conductivity was measured using the Four-Point Probe Method, within a pressure range of 5 x 10⁻⁶. 6 Pa to 65x10 6 The values between Pa were measured.
[0080] The results show that the sodium ion diffusion coefficient of the secondary sintered products of Examples 1 and 2 falls within 1.0 x 10⁻⁶. -10 square centimeters per second to 1.6 x 10 -9 Between square centimeters per second, the electronic conductivity falls within 1.0 x 10^6 cm^2 / s. -4 millisiemens / cm to 9.0 x 10 -3 The efficiency is between millisiemens per centimeter. Compared to existing positive electrode materials, both the sodium ion diffusion coefficient and electronic conductivity are improved.
[0081] 3. Battery performance
[0082] To confirm the primary sinter, secondary sinter, and commercially available electrodes 1 and 2 [NaNi] in the embodiments of this disclosure. 1 / 3 Fe 1 / 3 Mn 1 / 3 The electrical performance differences between O2 are summarized in Table 2. The performance parameters obtained from the half-cell electrical tests performed on each group in point 2 of Example 1 and point 2 of Example 2, as well as the performance parameters obtained from the same half-cell tests performed on commercially available electrode 1 and commercially available electrode 2, are combined together. The commercially available electrode group 1 and commercially available electrode group 2 are the performance parameters obtained by performing the same half-cell electrical tests performed on the half-cells in point 2 of Example 1, respectively, using commercially available electrode 1 or commercially available electrode 2 as the positive electrode. The capacity retention rate is the percentage of charging capacitor to discharging capacitor.
[0083] Table 2
[0084] Table 2 shows that, compared to commercially available electrode group 1 or commercially available electrode group 2, the half-cells prepared by the primary or secondary sintering material of Example 1 or the primary or secondary sintering material of Example 2 exhibit superior electrical performance in terms of capacitance retention rate, discharge capacitance after 100 cycles, and capacitance retention rate.
[0085] Furthermore, an internal comparison of the primary and secondary sintered materials obtained in the same embodiment reveals that, regardless of whether it is Embodiment 1 or Embodiment 2, the secondary sintered material exhibits superior electrical performance (discharge capacitance and capacity retention) after 100 cycles compared to the primary sintered material. In other words, using the secondary sintered material (obtained by further sintering with inert gas after the initial sintering) as the positive electrode material helps improve the cycle stability of the battery.
[0086] Although the present disclosure has been described above with reference to embodiments, it is not intended to limit the present disclosure. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure shall be determined by the appended claims.
[0087]
Symbol Explanation
Claims
1. A positive electrode material comprising P2-type phase microregions, characterized in that, include: The O3-type host has an O3-type layered structure, comprising O3-type material and oxygen vacancies replacing oxygen elements in the O3-type material, wherein the molecular formula of the O3-type host is Na. x MO 2-y □ y □ represents the oxygen vacancy, 0.7≤x≤1, 010 -10 ≤y≤0.2, M is one or more of lithium, magnesium, aluminum, vanadium, titanium, chromium, iron, nickel, cobalt, manganese, copper, zinc, strontium, zirconium, lanthanum, and bismuth; and The P2-type phase microregion is located on the surface of the O3-type main body and has a P2-type layered structure.
2. The positive electrode material according to claim 1, wherein the oxygen vacancy is located inside, outside or in combination thereof in the O3 type material.
3. The positive electrode material according to claim 1, wherein the O3 type matrix has a hexagonal crystal system and belongs to space group R-3m.
4. The positive electrode material according to claim 1, wherein the O3-type material comprises NaNi. 0.45 Mn 0.4 Cu 0.05 Ti 0.1 O 2-y □ y NaNi 0.5 Mn 0.5 O 2-y □ y , or combinations thereof, of which 10 -10 ≤y≤0.
2.
5. The positive electrode material according to claim 1, wherein the P2-type phase microregion contains Na x The P2 material of MO2, wherein 0.5≤x≤0.7, and M is one or more of the following: lithium, magnesium, aluminum, vanadium, titanium, chromium, iron, nickel, cobalt, manganese, copper, zinc, strontium, zirconium, lanthanum, and bismuth.
6. The positive electrode material according to claim 1, wherein the O3-type main body and the P2-type phase microregion are respectively based on the O3-type main body. <006> Crystal planes and the P2-type phase micro-region <106> The crystal planes are adjacent to each other.
7. The positive electrode material according to claim 1, wherein when the positive electrode material is measured by electron paramagnetic resonance, the concentration of oxygen vapor in the positive electrode material is 1.0 x 10⁻⁶. -7 Moles per liter to 1.0 x 10 -6 Between moles per liter.
8. The positive electrode material according to claim 1, wherein when the positive electrode material is detected by a constant current step titration test, the sodium ion diffusion coefficient of the positive electrode material is 1.0 x 10⁻⁶. -10 square centimeters per second to 1.6 x 10 -9 Between square centimeters per second.
9. The positive electrode material according to claim 1, wherein when the positive electrode material is detected using a four-probe method, the electronic conductivity of the positive electrode material is 1.0 x 10⁻⁶. -4 millisiemens / cm to 9.0 x 10 -3 Between millisiemens per centimeter.
10. A sodium-ion battery, characterized in that, include: negative electrode; Positive electrode, comprising the positive electrode material according to claim 1; A separator is disposed between the negative electrode and the positive electrode; and Sodium-ion battery electrolyte.
11. A method for preparing a positive electrode material, characterized in that, include: Provided are metal oxides and sodium-containing compounds, wherein the metal oxide contains one or more of lithium, magnesium, aluminum, vanadium, titanium, chromium, iron, nickel, cobalt, manganese, copper, zinc, strontium, zirconium, lanthanum, and bismuth; and The metal oxide and the sodium-containing compound are mixed to obtain a mixture; In an oxygen or air atmosphere, a first heating treatment is performed to obtain a primary sintered product; as well as In an inert atmosphere, the primary sintered material is subjected to a second heat treatment to obtain a secondary sintered material, thereby obtaining a positive electrode material, wherein the positive electrode material comprises an O3 type body with oxygen vacancies and a P2 type phase microregion located on the surface of the O3 type body.
12. The method for preparing the positive electrode material according to claim 11, wherein the step of mixing the metal oxide and the sodium-containing compound comprises: According to the molecular formula Na of the O3-type material to be generated from this positive electrode material x MO2 is used to adjust the molar ratio of the metal oxide to the sodium-containing compound, such that the molar ratio of the metal in the metal oxide to the sodium in the sodium-containing compound is similar to that of the compound with the molecular formula Na. x In MO2, the molar ratio of Na to M is the same, where 0.7 ≤ x ≤ 1, and M is one or more of the following: lithium, magnesium, aluminum, vanadium, titanium, chromium, iron, nickel, cobalt, manganese, copper, zinc, strontium, zirconium, lanthanum, and bismuth.
13. The method for preparing the positive electrode material according to claim 11, wherein the sodium-containing compound comprises sodium carbonate, sodium hydroxide, sodium acetate, sodium fluoride, or a combination thereof.
14. The method for preparing the positive electrode material according to claim 11, wherein the first heat treatment comprises: Heating at a rate of 1°C / min to 10°C / min to 600°C to 1000°C for 10 to 20 hours; and Cool down at a rate of 1°C / minute to 3°C / minute.
15. The method for preparing the positive electrode material according to claim 11, wherein after the first heat treatment, the method comprises grinding and crushing the primary sintered material until the particle size of individual particles in the primary sintered material is 1 nanometer to 10 micrometers.
16. The method for preparing the positive electrode material according to claim 11, wherein the inert atmosphere comprises nitrogen, argon, helium, neon, or a combination thereof.
17. The method for preparing the positive electrode material according to claim 11, wherein the second heat treatment comprises: Heating at a rate of 1°C / min to 10°C / min to 300°C to 800°C for 2 to 10 hours; and Cool down at a rate of 1°C / minute to 3°C / minute.
18. The method for preparing the positive electrode material according to claim 11, wherein after the second heat treatment, the secondary sintered material is crushed such that the particle size of individual particles in the secondary sintered material is 1 nanometer to 10 micrometers.