A high-rate performance Cu-doped iron-manganese base layer oxide cathode material for sodium-ion batteries and its preparation method

Abstract

This invention provides a high-rate-performance Cu-doped iron-manganese-based layered oxide cathode material for sodium-ion batteries and its preparation method, relating to the field of sodium-ion battery cathode material preparation. This cathode material is prepared by Cu... 2+ Single-element doping of P2-type iron-manganese base oxide Na 0.67 Fe 0.5 Mn 0.5 O2 is modified to produce Na 0.67 Fe 0.47 Mn 0.5 Cu 0.03 O2. This material is prepared using a simple and efficient solid-state sintering method. By introducing an appropriate amount of Cu into the transition metal layer, the interlayer structural stability of the material is enhanced, effectively improving its rate performance and cycle stability. Simultaneously, Cu doping optimizes sodium ion diffusion kinetics, increasing cycle capacity. The raw materials used in this invention are inexpensive, the preparation process is simple, and the resulting cathode material exhibits high crystallinity, uniform particle distribution, and excellent electrochemical performance, showing promising application prospects in the field of sodium-ion battery cathode materials for large-scale energy storage.

Description

Technical Field

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

[0002] With the continuous advancement of social development and industrialization, human demand for energy continues to grow. Every major transformation in energy utilization has driven advancements in science and technology and industrial levels. In recent years, renewable energy sources such as solar, wind, tidal, and geothermal energy have received widespread attention due to their advantages of being green and low-carbon. However, these energy sources are easily affected by climate and geographical conditions in practical applications, resulting in issues such as output fluctuations and intermittency. Therefore, they require supporting high-efficiency energy storage systems to ensure a stable energy supply.

[0003] Among numerous energy storage technologies, sodium-ion batteries are considered an important candidate system for large-scale energy storage due to their similar sodium insertion / extraction mechanism to lithium-ion batteries, as well as the advantages of abundant sodium resources and low acquisition costs. Currently, sodium-ion battery cathode materials mainly include layered oxides, polyanionic compounds, and Prussian blue analogues, with layered oxides becoming a research focus due to their high theoretical capacity and excellent electrochemical performance. Based on the oxygen layer stacking mode and the position of sodium ions, layered oxides are generally classified into P-type and O-type structures. Among them, P2-type layered materials exhibit better rate performance and ion transport kinetics because sodium ions are located in a triangular prism coordination environment, resulting in a shorter ion migration path and a lower Na⁺ diffusion barrier. P2-type iron-manganese layered oxides... 0.67 Fe 0.5 Mn 0.5 O2 has attracted widespread attention due to its low raw material cost, environmental friendliness, and high theoretical specific capacity. However, this material is prone to irreversible phase structure evolution and Fe-related structural distortions during high-voltage cycling, leading to capacity decay and decreased cycling stability.

[0004] To address the aforementioned issues, researchers typically employ strategies such as elemental doping, surface coating, and micro / nanostructure manipulation to enhance the structural stability of materials. Among these, elemental doping can effectively modulate the electronic structure of crystals, enhance interlayer interactions, and suppress unfavorable phase transitions and structural collapse, thereby improving the cycling performance of materials while maintaining high capacity. Summary of the Invention

[0005] The purpose of this invention is to solve at least one of the above-mentioned technical problems by means of transition metal layer doping, and to provide a low-cost, easy-to-prepare sodium-ion battery cathode material with high capacity retention.

[0006] This invention first provides a high-rate performance Cu-doped iron-manganese-based layered oxide cathode material for sodium-ion batteries and its preparation method. This cathode material is based on Na… 0.67 Fe 0.5 Mn 0.5 O2 transition metal layer element sites doped with Cu 2+ The positive electrode material is obtained through modification, and its chemical formula is Na. 0.67 Fe 0.5-x Mn 0.5 Cu x O2 (x=0.03).

[0007] This invention also provides a method for preparing the above-mentioned sodium-ion battery cathode material, which is prepared by solid-state sintering and includes the following steps:

[0008] (1) Weigh out the sodium source, manganese source, iron source and copper source according to the molar ratio, put them into a mortar and grind by hand for 0.3~1h, then put them into a ball mill jar and add a dispersant and ball mill at 200~600r / min for 2~6h to obtain a uniformly dispersed mixture, and dry for 2~8h to obtain the precursor;

[0009] (2) The precursor is placed in a tube furnace for precalcination.

[0010] (3) The pre-calcined powder is placed in a tube furnace for recalcination to obtain sodium-ion battery cathode material.

[0011] As a further aspect of the present invention: the sodium source mentioned in step (1) is selected from one or more of sodium carbonate, sodium nitrate, sodium acetate, sodium oxalate, and sodium hydroxide;

[0012] The manganese source is selected from one or more of manganese dioxide, manganese trioxide, manganese nitrate, manganese oxalate, and manganese sulfate;

[0013] The iron source is selected from one or more of iron oxide, ferric nitrate, and ferric sulfate;

[0014] The copper source is selected from one or more of copper oxide, copper nitrate, and copper sulfate;

[0015] As a further aspect of the present invention: the dispersant in step (1) is acetone or anhydrous ethanol.

[0016] As a further aspect of the present invention: in step (2), the high-temperature pre-calcination experimental conditions are: calcination temperature 300~600℃, heating rate 3~10℃ / min, calcination time 10~24h, and the protective atmosphere includes, but is not limited to, air atmosphere, argon atmosphere, oxygen atmosphere, helium atmosphere, and nitrogen atmosphere.

[0017] As a further aspect of the present invention: in step (3), the high-temperature calcination experimental conditions are: calcination temperature 800~1200℃, heating rate 3~10℃ / min, calcination time 10~24h, and the protective atmosphere includes, but is not limited to, air atmosphere, argon atmosphere, oxygen atmosphere, helium atmosphere, and nitrogen atmosphere.

[0018] This invention also provides a method for preparing a sodium-ion battery positive electrode sheet with single-point doping modification, comprising the following steps:

[0019] (1) Grind the active positive electrode material, conductive additive and binder evenly in a mass ratio of 8:1:1, 7:2:1 or 75:15:10;

[0020] (2) Add N-methylpyrrolidone to the powder in step (1) and mix it with the active material at a ratio of 1 / 1 to 1.5 (g / ml). Stir on a magnetic stirrer for 0.5-8 hours to obtain a slurry.

[0021] (3) The slurry is evenly coated onto the aluminum foil using a coater to a thickness of 100-400 μm;

[0022] (4) Dry in a vacuum drying oven at 80~120℃ for 8~12h;

[0023] (5) Cut the electrode sheet into a round piece to obtain the positive electrode of the battery.

[0024] Application of the positive electrode material in sodium-ion batteries

[0025] The positive electrode material plays a role in improving capacity retention and cycle stability in the application described.

[0026] The beneficial effects of this invention are reflected in:

[0027] (1) By replacing part of the Fe element in the matrix with electrochemically inactive copper element, the structural stability is increased during the sodium ion insertion / extraction process, the rate performance and cycle stability are improved, and the performance of sodium ion battery is improved.

[0028] (2) The cathode material prepared by the present invention has high crystallinity, uniform particle distribution and smooth surface.

[0029] (3) The raw materials used in this invention are inexpensive and the preparation process is simple and efficient, which is of great significance in promoting the large-scale production of sodium-ion batteries. Attached Figure Description

[0030] Figure 1 The X-ray diffraction (XRD) pattern of the sodium-ion battery cathode material obtained in the embodiments of the present invention;

[0031] Figure 2This is a scanning electron microscope (SEM) morphology image of the sodium-ion battery cathode material obtained in the embodiments of the present invention;

[0032] Figure 3 This is a comparison chart of the rate performance of sodium-ion battery cathode materials obtained in the embodiments and comparative examples of the present invention;

[0033] Figure 4 This is a cycling performance diagram of the target product obtained in the embodiment of the present invention after 150 cycles at a 1C rate. Specific implementation methods

[0034] The following description, in conjunction with embodiments, illustrates the layered oxide cathode material for suppressing high-voltage phase transition sodium ions and its preparation method. The scope of protection of this invention is not limited by the following embodiments. Example

[0035] Steps: Prepare Na by solid-state sintering 0.67 Fe 0.47 Mn 0.5 Cu 0.03 O2 cathode material

[0036] (1) Weigh 1.8641g of anhydrous sodium carbonate (5% excess to compensate for high temperature loss), 1.8764g of ferric oxide, 0.1193g of copper oxide, and 1.9735g of manganese oxide according to the molar ratio, place them in an agate ball mill jar, add anhydrous ethanol as a dispersant, and spheroidize them on a ball mill at a speed of 350r / min for 3h.

[0037] (2) The ball-milled dispersion was dried in a drying oven at 110°C for 12 hours, and then pressed into sheets under a pressure of 6 MPa and transferred to a crucible;

[0038] (3) Place the crucible in a tube furnace and sinter it in an air atmosphere. The temperature is increased to 500°C at 5°C / min, held for 6 hours, and then cooled to 200°C before being removed.

[0039] (4) Place the crucible into a tube furnace and sinter it again in an air atmosphere. The temperature is increased to 900°C at 5°C / min, held for 12 hours, and then cooled to 200°C to obtain the positive electrode material of the battery.

[0040] Step 2: Preparation of Na 0.67 Fe 0.47 Mn 0.5 Cu 0.03 O2 positive electrode plate

[0041] (1) The above-prepared positive electrode material, Super P, and polyvinylidene fluoride are mixed in a mass ratio of 8:1:1. The mixture is hand-ground until uniform. N-methylpyrrolidone is added, and the mass-volume ratio of the mixed powder to it is 1:1.2. The mixture is stirred on a magnetic stirrer for 30 minutes to form a slurry. The slurry is coated on aluminum foil with a thickness of 100 μm. Then it is placed in a vacuum drying oven and dried at 120°C for 10 hours to obtain an electrode sheet.

[0042] (2) Using sodium metal as the negative electrode, the 2032 button cell was assembled. The entire assembly process was carried out in a glove box filled with argon gas. The assembly sequence was: negative electrode shell, sodium metal, glass fiber separator (GF / D), electrolyte (1M NaClO4 in EC:DC=1:1 vol%), positive electrode plate (14mm), gasket, spring ring, and positive electrode shell.

[0043] Comparative example:

[0044] Molecular formula Na 0.67 Fe 0.5 Mn 0.5 The preparation process of the O2 sodium-ion battery cathode material is exactly the same as in the example. The preparation process of the electrode sheet, as well as the battery assembly and testing process, are also the same as in the example.

[0045] The above description is an embodiment of the present invention and is not intended to limit the product form and style of the present invention. Any substitutions and improvements made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-rate performance Cu-doped iron-manganese base layer oxide cathode material for sodium-ion batteries and its preparation method, characterized in that: This cathode material is for Na 0.67 Fe 0.5 Mn 0.5 O2 transition metal site doping Cu 2+ The positive electrode material is obtained through modification, and its chemical formula is Na. 0.67 Fe 0.5-x Mn 0.5 Cu x O2 (x=0.03).

2. A method for preparing the sodium-ion battery cathode material as described in claim 1, characterized in that, The preparation is carried out by solid-state sintering, including the following steps: (1) Weigh out sodium source, manganese source, iron source and copper source according to the molar ratio, put them into a ball mill jar and add dispersant. Ball mill at 200~500r / min for 2~6h to obtain a uniformly dispersed mixture. Dry for 4~12h to obtain the precursor. (2) The precursor is placed in a tube furnace for pre-calcination; (3) The pre-calcined powder is placed in a tube furnace for recalcination to obtain sodium-ion battery cathode material.

3. The preparation method according to claim 2, characterized in that: The sodium source mentioned in step (1) is selected from one or more of sodium carbonate, sodium nitrate, sodium acetate, sodium oxalate, and sodium hydroxide; The manganese source is selected from one or more of manganese dioxide, manganese trioxide, manganese nitrate, manganese oxalate, and manganese sulfate; The iron source is selected from one or more of iron oxide, ferric nitrate, and ferric sulfate; The copper source is selected from one or more of copper oxide, copper nitrate, and copper sulfate.

4. The preparation method according to claim 2, characterized in that: The dispersant in step (1) is acetone or anhydrous ethanol.

5. The preparation method according to claim 2, characterized in that: In step (2), the high-temperature calcination experimental conditions are: calcination temperature 300~600℃, heating rate 3~10℃ / min, calcination time 10~24h, and protective atmosphere including but not limited to air atmosphere, argon atmosphere, oxygen atmosphere, helium atmosphere, and nitrogen atmosphere.

6. The preparation method according to claim 2, characterized in that: In step (3), the high-temperature calcination experimental conditions are: calcination temperature 800~1200℃, heating rate 3~10℃ / min, calcination time 10~24h, and protective atmosphere including but not limited to air atmosphere, argon atmosphere, oxygen atmosphere, helium atmosphere, and nitrogen atmosphere.

7. A method for preparing a sodium-ion battery positive electrode with single-point doping modification, characterized by the following steps: (1) Grind the active positive electrode material, conductive additive and binder evenly in a mass ratio of 8:1:1, 7:2:1 or 75:15:10; (2) Add N-methylpyrrolidone to the powder in step (1), and mix the powder with it at a mass-to-volume ratio of 1:1~1.5 (g / ml). Stir on a magnetic stirrer for 0.5-8h to obtain a slurry. (3) The slurry is evenly coated onto the aluminum foil using a coater to a thickness of 100-400 μm; (4) Dry in a vacuum drying oven at 80~120℃ for 8~12h; (5) Cut the electrode into a round piece to obtain the positive electrode of the battery.

8. The preparation method according to claim 7, characterized in that: The binder in step (1) is one or more of polyvinylidene fluoride, polyacrylic acid, sodium carboxymethyl cellulose, and sodium alginate, and the conductive agent is one or more of Super P, carbon black, and Ketjen black.

9. The application of the cathode material according to claim 1 in a sodium-ion battery.

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