O3 type multi-metal doped sodium ion battery positive electrode material and preparation method thereof

Abstract

The invention discloses a nearly spherical O3 type layered oxide sodium-ion battery positive electrode material as well as a preparation method and application thereof. The chemical general formula of the material is NaxNi0.4-y-zCuyCozFe0.2 Mn0. 4O2 (x is greater than or equal to 0.8 and less than or equal to 1, y is greater than or equal to 0.1 and less than or equal to 0.15), the particle diameter is 15-30 microns, the specific surface area is 0.40-0.50 m < 2 > / g, the tap density reaches 3.0-3.3 g / cm < 3 >, and the interlayer spacing is prepared by adopting solid-phase synthesis in a preparation process, and comprises the following steps: mixing a precursor, calcining at high temperature, grinding the precursor by a ball-milling wet method, pressing into a wafer, and carrying out heat treatment in a controllable atmosphere to form a target structure. Due to Cu and Co multi-metal synergistic modification and specific molar ratio design, the prepared material is of a nearly spherical structure and has high tap density and a stable layered framework. Compared with the prior art, the material shows high specific capacity (the first-cycle reversible capacity is 115mAh / g) and excellent cycle stability (the capacity retention rate after 600 cycles is greater than or equal to 85%) in a sodium ion battery, and a new scheme is provided for a high-energy-density sodium battery positive electrode.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of sodium ion battery positive electrode materials, in particular to a near-spherical O3-type layered oxide positive electrode material with a multi-metal synergistic effect and a novel molar ratio and a solid-state synthesis process thereof, which is suitable for a high-energy-density sodium ion battery system. BACKGROUND

[0002] The contradiction between the continuous rise of global energy consumption and the limited reserves of traditional fossil energy forces human society to urgently develop a sustainable clean energy system. Zero-carbon technologies represented by photovoltaic power generation, wind power generation and ocean energy utilization have become an important direction for energy structure transformation, but their inherent uneven temporal and spatial distribution characteristics have put forward urgent demands for supporting energy storage systems. Among various electrochemical energy storage devices, lithium ion batteries have been commercialized and popularized due to their excellent energy density and cycle stability. However, due to the imbalance between supply and demand caused by the uneven geographical distribution of lithium resources and the problem of cost increase, the scientific research community is accelerating the development of new energy storage systems based on sodium ion chemistry. As the sixth most abundant element in the earth's crust (accounting for 2.3-2.8wt%), the geographical balance of the natural reserves of sodium provides a congenital advantage for building a low-cost battery system. The current research and development of sodium ion battery positive electrode materials mainly focuses on three systems: layered metal oxides, polyanion compounds and prussian blue derivatives. Compared with the other two types of materials, the layered oxide positive electrode has significant advantages in theoretical specific capacity and energy density due to its adjustable crystal structure characteristics. Layered oxide positive electrode materials have two structures: P2 type and O3 type. O3-type layered oxides are considered as ideal positive electrode candidate materials for sodium ion batteries due to their high sodium content and reversible capacity. However, traditional O3-type materials are prone to phase transition and irreversible sodium ion deintercalation during charging and discharging, resulting in rapid capacity decay. In addition, the O3-type Na[Ni 0.4 Fe 0.2 Mn 0.4 ]O2(NFM424) prepared by traditional solid-phase method usually presents a laminated shape, which makes the tap density low and is not conducive to commercial application. The application is supported by the Energy Shaanxi Laboratory Science and Technology Project, Project No. "The S&T Program of Energy Shaanxi Laboratory, Grant No. ESLB202402". SUMMARY

[0003] Invention objectives

[0004] The application provides a near-spherical O3-type layered oxide positive electrode material with a multi-metal synergistic effect and a novel molar ratio and a preparation method thereof, which adopts a solid-state synthesis process. The positive electrode material has high tap density and high capacity and stable cycle performance when used in a battery.

[0005] Technical solutions

[0006] The present invention provides the following technical solutions:

[0007] A nearly spherical O3-type layered oxide cathode material for sodium ion batteries, the general chemical formula of which can be expressed as Na x Ni 0.4-y-z Cu y Co z Fe 0.2 Mn 0.4 O2. The value range of the stoichiometric number x of Na is 0.8≤x≤1, the stoichiometric numbers y and z of Cu and Co satisfy 0.1≤y≤0.15 and 0.1≤z≤0.15 respectively, the diameter of the positive electrode material particles is 15-30μm, and the specific surface area is 0.40-0.50m 2 / g, tap density is 3.0-3.3g / cm 3 , the interlayer spacing is

[0008] The chemical formula of the material is specifically one of the following chemical formulas: Na 0.8 Ni 0.2 Cu 0.1 Co 0.1 Fe 0.2 Mn 0.4 O2;

[0009] Na 0.8 Ni 0.13 Cu 0.13 Co 0.13 Fe 0.2 Mn 0.4 O2;Na 0.9 Ni 0.2 Cu 0.1 Co 0.1 Fe 0.2 Mn 0.4 O2;

[0010] Na 0.9 Ni 0.13 Cu 0.13 Co 0.13 Fe 0.2 Mn 0.4 O2;Na Ni 0.2 Cu 0.1 Co 0.1 Fe 0.2 Mn 0.4 O2;

[0011] Nani 0.13 Cu 0.13 Co 0.13Fe 0.2 Mn 0.4 O2.

[0012] The preparation method of the above-mentioned layered oxide positive electrode material is characterized in that: the material preparation process includes: ① Precursor mixing treatment: mixing the precursors of the sodium source and the transition metal source according to the above-mentioned stoichiometric ratio, and subjecting them to ball milling wet grinding to obtain a uniformly mixed powder, which is then pressed into discs; ② High-temperature calcination treatment: heat treating the mixed powder under a controlled atmosphere to form a target layered structure.

[0013] The sodium source is selected from at least one of sodium carbonate, sodium nitrate, sodium acetate or sodium hydroxide, and the transition metal source is selected from oxides, sulfates, carbonates, acetates or nitrates corresponding to the transition metal source.

[0014] The ball milling speed is 200-500 rpm, the time is 3-15 h, and the ball milling medium is ethanol.

[0015] The heating rate in the high temperature treatment is 3 to 6°C / min, the final temperature range is controlled at 950 to 1050°C, and the holding time is controlled at 12 to 17 hours.

[0016] A method for preparing a sodium ion battery positive electrode sheet based on the above-mentioned layered oxide positive electrode material comprises the following steps: weighing the following components by mass: 80 mg of the above-mentioned powdered positive electrode material, 10 mg of Super P, and 10 mg of a binder; dissolving the weighed powdered material, Super P, and binder in N-methylpyrrolidone, grinding for 10 minutes to mix them evenly, and coating them on treated copper foil; placing the coated electrode sheet in a vacuum drying oven at 80° C. and vacuum drying for 10 hours, and then cutting the electrode sheet with a 10 mm mold to obtain the corresponding layered positive electrode material electrode sheet.

[0017] Beneficial effects

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention provides a nearly spherical O3-type layered oxide cathode material with a multi-metal synergistic effect and a novel molar ratio, the general chemical formula of which is Na x Ni 0.4-y- z Cu y Co z Fe 0.2 Mn 0.4 O2, wherein 0.8≤x≤1, 0.1≤y≤0.15, and 0.1≤z≤0.15. The O3-type layered cathode material provided by the present invention exhibits nearly spherical particles and a high tap density. Application of this cathode material in sodium-ion batteries can enable the batteries to exhibit high specific capacity and excellent cycle stability, thus having broad application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Micro-morphology characteristics of the layered cathode material prepared in Example 1 (SEM microstructure)

[0020] Figure 2 Crystal structure analysis of the product of Example 1 (X-ray diffraction spectrum characteristics)

[0021] Figure 3 Electrochemical behavior of the half-cell system assembled based on the electrode of Example 1 (charge-discharge curve)

[0022] Figure 4 Long cycle stability evaluation of the electrode of Example 1 (capacity retention rate evolution) DETAILED DESCRIPTION

[0023] The present application will now be described in detail below with reference to the accompanying drawings and specific embodiments. The present application can be embodied in many different forms and the scope of protection of the present application is not limited to the embodiments mentioned herein.

[0024] The present application provides a near-spherical O3-type layered oxide cathode material with a multi-metal synergistic effect and a new molar ratio and a solid-state synthesis process thereof, and applies the layered oxide cathode material to a sodium ion battery, which exhibits high capacity and stable cycle performance. Specifically, the following embodiments are included:

[0025] Example 1

[0026] NaNi 0.13 Cu 0.13 Co 0.13 Fe 0.2 Mn 0.4 O2 cathode material:

[0027] (1) Precisely weigh sodium carbonate, nickel oxide, copper oxide, manganese dioxide, and diiron trioxide, dicobalt trioxide precursors according to the stoichiometric ratio, and load them into a high-energy ball mill device.

[0028] (2) Perform wet grinding at a speed of 450 revolutions per minute, with anhydrous ethanol as the medium, and obtain a molecularly dispersed slurry after 8 hours of grinding. After vacuum drying at 80°C, a uniformly mixed powder is obtained.

[0029] (3) The uniformly mixed powder is pressed into a 12mm diameter disc under a pressure of 10Mpa

[0030] (4) Then, the disc precursor is transferred to a box-type resistance furnace for heat treatment: the temperature is raised to a target temperature of 1000°C at a rate of 5°C / min, and the lattice is constructed for 15 hours. Finally, the powder is obtained by grinding and sieving.

[0031] (5) The obtained powder material is prepared into a sodium ion battery positive electrode sheet: the following components are weighed by mass fraction: 80 mg of powder positive electrode material, 10 mg of Super P, and 10 mg of binder; after the weighed powder material, Super P, and binder are dissolved in N-methylpyrrolidone, they are ground for 10 minutes to make them uniformly mixed, and then coated on a treated copper foil; the coated electrode sheet is placed in a vacuum drying oven and vacuum dried at 80°C for 10 h, and then the electrode sheet is cut with a 10 mm mold to obtain the corresponding layered positive electrode material electrode sheet.

[0032] The particle diameter of the prepared positive electrode material is 22 pm, the specific surface area is 0.45 m 2 / g, and the tap density is 3.1 g / cm 3 The interlayer spacing is The traditional O3-type NFM424 has a flaky morphology, and the modified NaNi 0.13 Cu 0.13 Co 0.13 Fe 0.2 Mn 0. 4O2 material is changed into an elliptical or near-spherical structure. The anisotropy of the flaky morphology in the cycle process can exacerbate the volume expansion, leading to particle cracking, thereby affecting the electrochemical performance of the material. The tap density of the elliptical or near-spherical particle is higher, and this morphology can make the material more easily densely packed during electrode preparation, which is beneficial to increasing the volumetric energy density of the battery, making the uniformity and fluidity of the electrode material during preparation better, and enabling better ion conduction and improving the transport properties. Due to the high mechanical strength of the spherical structure, it is not easy to break during the cycle, and the structural stability is also better. Therefore, the modified NaNi 0.13 Cu 0.13 Co 0.13 Fe 0.2 Mn 0.4 O2 positive electrode has an initial specific capacity of 114.7 mAh / g under 2C charge and discharge conditions, and a capacity retention rate of 87.7% after 600 cycles. The coulombic efficiency is 92%, and it remains 99.7% in the subsequent cycles.

[0033] Example 2

[0034] The NaNi 0.8 Ni 0.2 Cu 0.1 Co 0.1 Fe 0.2 Mn 0.4 O2 positive electrode material is prepared by a solid-phase synthesis method:

[0035] (1) The sodium nitrate, nickel oxide, copper oxide, manganese dioxide, and iron dioxide precursors are accurately weighed according to the stoichiometry and loaded into a high-energy ball mill.

[0036] (2) Wet milling at 500 rpm for 10 h in ethanol, to obtain a molecularly dispersed slurry, which was dried at 80°C under vacuum to obtain a homogeneous mixed powder.

[0037] (3) The homogeneous mixed powder was pressed into a 12 mm diameter disc at 10 MPa

[0038] (4) The disc precursor was then transferred to a box resistance furnace for heat treatment: the target temperature of 1020°C was reached at a rate of 5°C / min, and the crystal lattice was constructed for 15 h, and finally the powder was obtained by grinding and sieving.

[0039] (5) The obtained powder material was prepared into a sodium-ion battery cathode material, and the following components were weighed by mass fraction: 80 mg of powder cathode material, 10 mg of Super P, and 10 mg of binder; the weighed powder material, Super P and binder were dissolved in N-methyl pyrrolidone, and then ground for 10 min to make them uniformly mixed, and then coated on a treated copper foil; the coated electrode piece was placed in a vacuum drying oven at 80°C for 10 h, and then the electrode piece was cut with a 10 mm mold, to obtain the corresponding layered cathode material electrode piece.

[0040] The prepared cathode material has a particle diameter of 27 pm, a specific surface area of 0.43 m2 / g, a tap density of 3.1 g / cm3, and an interlayer spacing of

[0041] Example 3

[0042] NaNi 0.2 Cu 0.1 Co 0.1 Fe 0.2 Mn 0.4 O2 cathode material:

[0043] (1) Sodium hydroxide, nickel oxide, copper oxide, manganese dioxide, and diiron trioxide and dicobalt trioxide precursors were accurately weighed according to the stoichiometry and loaded into a high-energy ball mill.

[0044] (2) Wet milling at 450 rpm for 15 h in ethanol, to obtain a molecularly dispersed slurry, which was dried at 80°C under vacuum to obtain a homogeneous mixed powder.

[0045] (3) The homogeneous mixed powder was pressed into a 12 mm diameter disc at 15 MPa

[0046] (4) Then the wafer precursor is transferred to a box resistance furnace for heat treatment: the target temperature of 1050℃ is reached at a heating rate of 5℃ / min, calcination is completed for 15 hours to build the crystal lattice, and finally the powder is obtained by grinding and sieving.

[0047] (5) The obtained powder material is prepared into a sodium ion battery positive electrode material, and the following components are weighed by mass fraction: 80 mg of powder positive electrode material, 10 mg of Super P, and 10 mg of binder; after the weighed powder material, Super P and binder are dissolved in N-methyl pyrrolidone, they are ground for 10 minutes to make them uniformly mixed, and then coated on a treated copper foil; the coated electrode sheet is placed in a vacuum drying oven at 80℃ for vacuum drying for 10 hours, and then the electrode sheet is cut with a 10 mm mold to obtain the corresponding layered positive electrode material electrode sheet.

[0048] The particle diameter of the prepared positive electrode material is 23μm, the specific surface area is 0.47m 2 / g, the tap density is 3.0g / cm 3 , and the interlayer spacing is

[0049] Example 4

[0050] Na 0.8 Ni 0.15 Cu 0.13 Co 0.12 Fe 0.2 Mn 0.4 O2 positive electrode material is prepared by a solid phase synthesis method:

[0051] (1) The sodium nitrate, nickel oxide, copper oxide, manganese dioxide, and diiron trioxide and dicobalt trioxide precursors are accurately weighed according to the stoichiometry and loaded into a high-energy ball mill device.

[0052] (2) Wet grinding is carried out at a speed of 450 revolutions per minute, the medium is anhydrous ethanol, and after 15 hours of continuous grinding, a molecularly dispersed slurry is obtained, which is treated by vacuum drying at 80℃ to obtain a uniformly mixed powder.

[0053] (3) The uniformly mixed powder is pressed into a wafer with a diameter of 12mm under a pressure of 12Mpa

[0054] (4) Then the wafer precursor is transferred to a box resistance furnace for heat treatment: the target temperature of 1050℃ is reached at a heating rate of 5℃ / min, calcination is completed for 15 hours to build the crystal lattice, and finally the powder is obtained by grinding and sieving.

[0055] (5) The obtained powder material is prepared into a sodium ion battery positive electrode material. The following components are weighed by mass fraction: 80 mg of the powder positive electrode material, 10 mg of Super P, and 10 mg of a binder. After the weighed powder material, Super P, and binder are dissolved in N-methyl pyrrolidone, they are ground for 10 minutes to make them uniformly mixed, and then coated on a treated copper foil. The coated pole piece is placed in a vacuum drying oven at 80°C for vacuum drying for 10 hours, and then the pole piece is cut with a 10 mm mold to obtain a corresponding layered positive electrode material electrode piece.

[0056] The particle diameter of the prepared positive electrode material is 25 μm, the specific surface area is 0.46 m 2 / g, the tap density is 3.3 g / cm 3 , and the interlayer spacing is

[0057] Example 5

[0058] The NaNi 0.15 Cu 0.13 Co 0.12 Fe 0.2 Mn 0.4 O2 positive electrode material is prepared by a solid phase synthesis method.

[0059] (1) Sodium hydroxide, nickel oxide, copper oxide, manganese dioxide, and diiron trioxide and dicobalt trioxide precursors are accurately weighed according to stoichiometry and loaded into a high-energy ball mill device.

[0060] (2) Wet grinding is performed at a speed of 480 revolutions per minute, with anhydrous ethanol as the medium, for 10 hours to obtain a molecularly dispersed slurry, which is subjected to vacuum drying treatment at 80°C to obtain a uniformly mixed powder.

[0061] (3) The uniformly mixed powder is pressed into a 12 mm diameter disc under a pressure of 20 MPa.

[0062] (4) The disc precursor is then transferred to a box-type resistance furnace for heat treatment: the temperature is raised at a rate of 5°C / min to reach a target temperature of 1030°C, calcination is performed for 15 hours to complete lattice construction, and finally the powder is obtained after grinding and sieving.

[0063] (5) The obtained powder material is prepared into a sodium ion battery positive electrode material. The following components are weighed by mass fraction: 80 mg of the powder positive electrode material, 10 mg of Super P, and 10 mg of a binder. After the weighed powder material, Super P, and binder are dissolved in N-methyl pyrrolidone, they are ground for 10 minutes to make them uniformly mixed, and then coated on a treated copper foil. The coated pole piece is placed in a vacuum drying oven at 80°C for vacuum drying for 10 hours, and then the pole piece is cut with a 10 mm mold to obtain a corresponding layered positive electrode material electrode piece.

[0064] The particle diameter of the prepared positive electrode material is 26 μm, the specific surface area is 0.42 m 2 / g, and the tap density is 3.2 g / cm 3 , and the interlayer spacing is

[0065] From the above experimental data, it can be seen that the traditional O3-type NFM424 has a flaky morphology, and the modified NaNi 0.13 Cu 0.1 3Co 0.13 Fe 0.2 Mn 0.4 O2 material is converted into an elliptical or nearly spherical structure. The anisotropy of the flaky morphology during the cycle process may exacerbate the volume expansion, leading to particle cracking, thereby affecting the electrochemical performance of the material. The tap density of the elliptical or nearly spherical particles is higher, and this morphology can make the material more easily packed during electrode preparation, which is beneficial to increase the volume energy density of the battery, make the uniformity and fluidity of the electrode material during preparation better, and better enable ion conduction, improve the transmission characteristics. Due to the high mechanical strength of the spherical structure, it is not easy to break during the cycle, and the structural stability is also better.

Claims

1. A nearly spherical O3-type sodium ion battery layered oxide cathode material, whose general chemical formula is Na x Ni 0.4-y- z Cu y Co z Fe 0.2 Mn 0.4 O2; among them, The value range of the stoichiometric number x of Na is 0.8≤x≤1, the stoichiometric numbers y and z of Cu and Co satisfy 0.1≤y≤0.15 and 0.1≤z≤0.15 respectively, the diameter of the positive electrode material particles is 15-30 μm, and the specific surface area is 0.40-0.50 m 2 / g, tap density is 3.0-3.3g / cm 3 , the interlayer spacing is 2. The sodium ion battery layered oxide positive electrode material according to claim 1, characterized in that The material is specifically one of the following chemical formulas: Na 0.8 Ni 0.2 Cu 0.1 Co 0.1 Fe 0.2 Mn 0.4 O2; So 0.8 Ni 0.13 Cu 0.13 Co 0.13 Feb 0.2 Mr 0.4 O2;Na 0.9 Ni 0.2 Cu 0.1 Co 0.1 Feb 0.2 Mr 0.4 O2; So 0.9 Ni 0.13 Cu 0.13 Co 0.13 Feb 0.2 Mr 0.4 O2;By Ni 0.2 Cu 0.1 Co 0.1 Feb 0.2 Mr 0.4 O2; Pretty 0.13 Cu 0.13 Co 0.13 Feb 0.2 Mr 0.4 O2。 3. A method for preparing a layered oxide positive electrode material according to claim 1 or 2, characterized in that: The preparation process of the material includes: ① precursor mixing treatment: mixing the precursors of the sodium source and the transition metal source according to the stoichiometric ratio of claim 1 or 2, and subjecting them to ball milling wet grinding to obtain a uniformly mixed powder, which is then pressed into discs; ② high-temperature calcination treatment: heat-treating the mixed powder under a controlled atmosphere to form a target layered structure.

4. The preparation method according to claim 3, characterized in that The sodium source is selected from at least one of sodium carbonate, sodium nitrate, sodium acetate or sodium hydroxide, and the transition metal source is selected from oxides, sulfates, carbonates, acetates or nitrates corresponding to transition metals.

5. The preparation method according to claim 3, characterized in that The ball milling speed is 200-500 rpm, the time is 3-15 h, and the ball milling medium is ethanol.

6. The preparation method according to claim 3, characterized in that The heating rate in the high temperature treatment is 3 to 6°C / min, the final temperature range is controlled at 950 to 1050°C, and the holding time is controlled at 12 to 17 hours.

7. A method for preparing a positive electrode sheet for a sodium ion battery, characterized in that: The following steps are involved: The following components were weighed in parts by mass: 80 mg of the layered oxide positive electrode material according to any one of claims 1 to 2 or the layered oxide positive electrode material prepared by the preparation method according to any one of claims 3 to 6, 10 mg of Super P, and 10 mg of a binder; the weighed positive electrode material, Super P, and binder were dissolved in N-methylpyrrolidone, ground for 10 minutes to mix them evenly, and then coated on the treated copper foil; the coated electrode sheet was placed in a vacuum drying oven and vacuum-dried at 80°C for 10 hours, and then the electrode sheet was cut with a 10 mm mold to obtain a layered positive electrode material electrode sheet.

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