Preparation method of O3 type layered sodium ion battery positive electrode material with specific stoichiometric ratio

Abstract

The application provides a preparation method of a specific stoichiometric ratio of O3 type layered sodium ion battery positive electrode material. By finely controlling the ratio of Ni, Fe and Mn, the main redox activity is controlled in a specific electric pair range, the structure stability and the electrochemical performance can be improved, and the phase transition can be effectively inhibited. The performance improvement is attributed to the favorable electronic structure given by the specific component ratio, which promotes the Mn 3+ / Mn 4+ and Fe 2+ / Fe 3+ redox couples to participate in cooperation, thereby expanding the charge compensation window and improving the structure stability. The precursor material is obtained by a simple coprecipitation method, and the obtained material has good consistency and low cost after further high-temperature calcination. The prepared sodium ion battery positive electrode material has excellent performance and is suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to a method for preparing a layered sodium-ion battery cathode material of O3 type with a specific stoichiometric ratio, belonging to the field of sodium-ion battery technology. Background Technology

[0002] The global transition to renewable energy and the rapid development of the electric vehicle market have created unprecedented demand for efficient, large-scale electrochemical energy storage systems. For a long time, lithium-ion batteries have dominated due to their mature applications in portable electronic devices and grid energy storage. However, the scarcity and uneven geographical distribution of global lithium and cobalt resources have led to increasingly severe supply chain security and geopolitical risks, prompting the industry to actively seek more sustainable and economical alternatives. Against this backdrop, sodium-ion batteries, with their abundant and widely distributed sodium resources and low cost, are considered one of the most promising technologies for partially replacing or supplementing lithium-ion batteries in large-scale energy storage applications. Furthermore, the two technologies are highly compatible in terms of intercalation chemistry and battery processes, facilitating a smooth technology transition and industrial integration. Among the many sodium-ion battery cathode materials, layered oxide cathodes show great potential due to their high theoretical capacity, relatively high operating voltage, and relatively simple synthesis process. Based on the coordination environment of sodium ions (octahedral or prismatic sites) and the oxygen layer stacking method, layered oxides are mainly divided into two types: O3 and P2. P2-type materials typically exhibit superior rate performance and structural stability, while O3-type materials, due to their higher initial sodium content, often demonstrate higher actual specific capacity and are therefore more favored for commercial applications.

[0003] Among O3-type layered cathode materials, the nickel-iron-manganese ternary system has become a research hotspot due to its good overall performance and controllable raw material costs. In recent years, this system has been extensively explored. Despite its advantages, its practical application is still limited by several inherent defects: irreversible phase transitions during deep sodium removal, slow sodium ion diffusion kinetics, poor rate performance, and capacity decay and decreased cycle stability due to transition metal dissolution during cycling. Currently, two main strategies are used to alleviate these problems: one is to suppress electrode-electrolyte side reactions through surface modification; the other is to perform intrinsic modification through bulk doping or compositional control. While doping and coating are effective, they also increase the complexity of material preparation. In contrast, finely controlling the stoichiometry of transition metals such as nickel, iron, and manganese to optimize the crystal structure and electronic properties of the material is considered a more direct and economical way to improve intrinsic performance. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for preparing O3-type layered sodium-ion battery cathode material with a specific stoichiometric ratio.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A specific stoichiometric O3-type layered sodium-ion battery cathode material, characterized in that: the material is prepared by the following method, the steps of which are as follows: Nickel sulfate, ferrous sulfate, and manganese sulfate were dissolved in deionized water in a stoichiometric ratio of x:y:1-xy (where x and y satisfy 0 < x < 1, 0 < y < 1, and x + y < 1). Ascorbic acid was added to the solution as an antioxidant, and the mixture was stirred until completely dissolved to obtain a homogeneous solution I.

[0006] Sodium hydroxide in stoichiometric proportions is dissolved in deionized water containing ammonia. The pH of the solution is stabilized at 11 by adjusting the amount of ammonia added, thus obtaining solution II.

[0007] Solution I and Solution II are simultaneously pumped into the reaction tank through feed pipes. During the pumping process, the mixed solution in the reaction tank is continuously mechanically stirred, and the reaction temperature is maintained at 60°C.

[0008] After all solutions I and II are pumped into the reaction tank, the mixture is stirred and reacted for 3 hours at 60°C to obtain the reaction mixture, i.e., solution III.

[0009] Solution III was subjected to solid-liquid separation, the solid product was collected, and washed with deionized water until neutral. Then, it was vacuum dried at 100°C to obtain the precursor material.

[0010] The above-mentioned precursor material was ground and mixed with sodium carbonate at a stoichiometric ratio of 2:1.05, and then calcined in air. After cooling, a specific stoichiometric ratio of O3-type layered sodium-ion battery cathode material was obtained.

[0011] Preferably, in step (1), the concentration of the mixed solution I is 2.0 mol / L.

[0012] Preferably, in step (2), the concentration of sodium hydroxide in solution II is 10.0 mol / L, and the amount of sodium hydroxide is 2, which is the precipitant in the reaction.

[0013] Preferably, in step (2), the concentration of ammonia in solution II is 1.5 mol / L, which is a complexing agent in the reaction.

[0014] Preferably, in step (3), the pumping speed of solution I and solution II into the reaction tank is 1:1, and the mechanical stirring speed is 500~1000 r / min.

[0015] Preferably, in step (6), the calcination temperature is 800℃~950℃ and the annealing time is 8h~15h.

[0016] A sodium-ion battery, wherein the positive electrode material of the battery adopts the O3-type layered sodium-ion battery positive electrode material with a specific stoichiometric ratio as described in this invention. Beneficial effects

[0017] This invention provides a method for preparing O3-type layered sodium-ion battery cathode materials with a specific stoichiometric ratio. By precisely controlling the ratio of Ni, Fe, and Mn, the main redox activities are controlled within a specific redox pair range, which synergistically improves structural stability and electrochemical performance, and effectively suppresses phase transitions. The performance improvement is attributed to the favorable electronic structure conferred by the specific component ratio, which promotes Mn... 3+ / Mn 4+ with Fe 2+ / Fe 3+ The synergistic participation of redox couples expands the charge compensation window and enhances structural stability.

[0018] The present invention provides a method for preparing O3-type layered sodium-ion battery cathode material with a specific stoichiometric ratio. The precursor material is obtained through a simple co-precipitation method, and after further high-temperature calcination, the resulting material has good consistency and low cost. The prepared sodium-ion battery cathode material has excellent performance and is suitable for large-scale production. Attached Figure Description

[0019] Figure 1 This is a diagram of the synthesis steps in Example 1.

[0020] Figure 2 The image shows the energy dispersive spectroscopy (EDS) spectrum of the cathode material prepared in Example 1.

[0021] Figure 3 Cyclic data at 1.0C current density for batteries assembled using the cathode materials prepared in Examples 1 and 2.

[0022] Figure 4 Rate maps of batteries assembled from the cathode materials prepared in Examples 1 and 2 at different current densities. Detailed Implementation

[0023] To better clarify and understand the objectives, process solutions, and advantages of this invention, the technical solutions and implementation methods of this invention will be further described clearly, completely, and in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the embodiments described in this invention are implemented under the premise of the technical solutions of this invention, providing detailed implementation methods and specific operating procedures, but are only some embodiments of this invention, not all embodiments. The specific implementation methods described are limited to illustrating and explaining this invention and do not limit this invention. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] Unless otherwise specified, the experimental methods and conditions used in the embodiments of this invention are conventional methods and conditions. The materials, reagents, and instruments used in the embodiments, unless otherwise specified, can be obtained commercially or prepared by conventional methods. The reaction conditions described in the invention can all achieve the reactions and obtain the desired products. Due to space limitations, some embodiments are listed below to further illustrate the advantages of the technical solution of this invention.

[0025] In the following embodiments or comparative examples: Assembly of button cell: At room temperature, the working electrode is first prepared by mixing the materials prepared in the examples or comparative examples with binder and conductive agent in a ratio of 8:1:1 to prepare a uniform slurry; then, the slurry is uniformly coated onto aluminum foil with a scraper and dried under vacuum at 100°C for 12 hours to obtain the working electrode; finally, the aluminum foil coated with the sample is pressed into a small disc with a diameter of 1.1 cm using a punching machine as the positive electrode, sodium sheet as the negative electrode material, and 1.0 M NaPF6 carbonate electrolyte to prepare a button half cell.

[0026] The Blue Electric system is used to detect electrochemical performance, with a test voltage range of 2 V-4 V, a test temperature of 30℃, and a test current density of 0.1C-5.0C (1.0C=130 mA / g). Example 1

[0027] A certain amount of raw materials NiSO4·6H2O, FeSO4·7H2O, and MnSO4·H2O were weighed out in a molar ratio of 4 / 9:1 / 18:1 / 2 and prepared into 150 mL of a 2.0 mol / L salt solution. 1.6 g of VC (ascorbic acid) was added to the salt solution to prevent oxidation, yielding solution I. 60 mL of a 10 mol / L NaOH solution was prepared as a precipitant, and a 1.5 mol / L ammonia solution was prepared as a complexing agent. The solutions were then mixed to obtain solution II. Solutions I and II were then simultaneously pumped into the reaction tank at a 1:1 ratio through separate feed lines. During the pumping process, the mixed solutions in the reaction tank were continuously mechanically stirred at 600 r / min, and the reaction temperature was maintained at 60℃. After all solutions I and II were pumped into the reaction tank, the reaction was continued to be stirred at 60°C for 3 hours to obtain the reaction mixture, i.e., solution III. Solution III was subjected to solid-liquid separation, the solid product was collected, and washed with deionized water until neutral. Then, it was vacuum dried at 100°C to obtain the precursor material. The above precursor material was then ground and mixed with sodium carbonate at a stoichiometric ratio of 2:1.05, and then calcined at 870°C for 12 hours in air atmosphere. After cooling, the O3-type layered sodium-ion battery cathode material NaNi of Example 1 was obtained. 4 / 9 Fe 1 / 18 Mn 1 / 2 O2. The material preparation process is as follows: Figure 1 As shown.

[0028] The energy spectrum of the O3-type layered sodium-ion battery cathode material with a specific stoichiometric ratio obtained in Example 1 is shown below. Figure 2 As shown, the results indicate that the cathode material contains a uniform distribution of Na, Ni, Fe, Mn, and O elements.

[0029] The cycle performance and rate capability of the assembled battery are as follows: Figure 3 and Figure 4 As shown. Example 2

[0030] After adjusting the stoichiometric ratio of NiSO4·6H2O, FeSO4·7H2O, and MnSO4·H2O to 1 / 2:1 / 6:1 / 3, the NaNi of Example 2 with a specific ratio can be obtained by following the steps of Example 1. 1 / 2 Fe 1 / 6 Mn 1 / 3 The performance of the positive electrode material obtained after O2 is assembled into a battery is as follows: Figure 3 and Figure 4 As shown. Example 3

[0031] After adjusting the stoichiometric ratio of NiSO4·6H2O, FeSO4·7H2O, and MnSO4·H2O to 4 / 9:1 / 6:7 / 18, the NaNi of Example 3 with a specific ratio can be obtained by following the steps of Example 1. 4 / 9 Fe 1 / 6 Mn 7 / 18 The performance of the positive electrode material obtained after O2 is assembled into a battery is as follows: Figure 3 and Figure 4 As shown.

Claims

1. A specific stoichiometric O3-type layered sodium-ion battery cathode material, characterized in that: The material is prepared by the following method, the steps of which are as follows: (1) Dissolve nickel sulfate, ferrous sulfate and manganese sulfate in deionized water in a stoichiometric ratio of x:y:1-xy (where x and y satisfy 0<x<1, 0<y<1 and x+y<1), and add ascorbic acid as an antioxidant to the solution. Stir until completely dissolved to obtain a homogeneous solution I. (2) Dissolve sodium hydroxide in stoichiometric ratio in deionized water containing ammonia, and stabilize the pH of the solution at 11 by adjusting the amount of ammonia added to obtain solution II; (3) Solution I and solution II are simultaneously pumped into the reaction tank through the feed pipeline. During the pumping process, the mixed solution in the reaction tank is continuously mechanically stirred, and the reaction temperature is maintained at 60°C. (4) After all solutions I and II are pumped into the reaction tank, the reaction is stirred for 3 hours at 60°C to obtain the reaction mixture, i.e., solution III. (5) Solid-liquid separation was performed on solution III, the solid product was collected and washed with deionized water until neutral, and then vacuum dried at 100°C to obtain the precursor material; (6) The above precursor material and sodium carbonate are ground and mixed at a stoichiometric ratio of 2:1.05, then calcined in air atmosphere, and cooled to obtain O3 type layered sodium ion battery cathode material with a specific stoichiometric ratio.

2. The O3-type layered sodium-ion battery cathode material with a specific stoichiometric ratio as described in claim 1, characterized in that: In step (1), the concentration of the mixed solution I is 2.0 mol / L.

3. The O3-type layered sodium-ion battery cathode material with a specific stoichiometric ratio as described in claim 1, characterized in that: In step (2), the concentration of sodium hydroxide in solution II is 10.0 mol / L, and the amount of sodium hydroxide is 2, which is the precipitant in the reaction.

4. The O3-type layered sodium-ion battery cathode material with a specific stoichiometric ratio as described in claim 1, characterized in that: In step (2), the concentration of ammonia in solution II is 1.5 mol / L, which is a complexing agent in the reaction.

5. The O3-type layered sodium-ion battery cathode material with a specific stoichiometric ratio as described in claim 1, characterized in that: In step (3), the pumping speed of solution I and solution II into the reaction tank is 1:1, and the mechanical stirring speed is 500~1000 r / min.

6. The O3-type layered sodium-ion battery cathode material with a specific stoichiometric ratio as described in claim 1, characterized in that: In step (6), the calcination temperature is 800℃~950℃ and the annealing time is 8h~15h.

7. A sodium-ion battery, characterized in that: The positive electrode material of the battery is any one of the O3-type layered sodium-ion battery positive electrode materials with a specific stoichiometric ratio as described in this invention.

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