A preparation process for magnesium-doped modified nickel-iron-manganese-based precursor materials

Abstract

This invention discloses a preparation process for magnesium-doped modified nickel-iron-manganese-based precursor materials, belonging to the field of electrode material preparation. The invention includes the following steps: (1) solution preparation; (2) preparation of the reaction substrate; (3) feeding; (4) nucleation reaction; (5) growth reaction; (6) magnesium doping modification; (7) aging reaction; (8) washing; and (9) drying. This invention utilizes magnesium-modified doped nickel-iron-manganese-based materials and employs an intermittent process to prepare sodium electrode precursors. By controlling factors such as the solid content, flow rate, and pH value of the reactants, the structure and morphology of the crystals can be precisely controlled. Simultaneously, the particle size distribution of the precursor can be well adjusted, thereby preparing sodium electrode precursor materials with uniform particle size.

Description

Technical Field

[0001] This invention relates to the field of electrode materials, specifically to a preparation process for a magnesium-doped modified nickel-iron-manganese-based precursor material. Background Technology

[0002] In the context of a "dual-carbon" era, developing clean and inexpensive new energy materials is the current direction of development. Currently, lithium-ion batteries are the most technologically mature and widely used new energy materials; however, their high price and extreme scarcity of lithium resources are the most serious problems restricting their development. To address these issues, sodium-ion batteries have emerged, and they represent the most promising new energy technology. Sodium-ion batteries come in many varieties, with layered oxide cathode materials being the main focus of current research. Layered oxide cathode materials are divided into P2 type and O3 type.

[0003] Currently, methods for preparing sodium battery precursor materials include co-precipitation, high-temperature solid-state methods, sol-gel methods, spray drying, hydrothermal / solvent methods, and microwave synthesis. Among these, co-precipitation is widely used due to its advantages such as mature equipment and ease of industrialization. However, in co-precipitation, the Ksp constants of Ni(OH)₂, Fe(OH)₂, and Mn(OH)₂ are not on the same order of magnitude. Therefore, achieving co-precipitation is a technical challenge, leading to difficulties in controlling the morphology and particle size distribution of the precursor. Morphological deviations and wide particle sizes result in lower tap density of the precursor, further reducing the compaction density of the cathode material and thus affecting the electrochemical performance of the battery material.

[0004] In addition, during the preparation of nickel-iron-manganese-based precursors, on the one hand, ferrous ions are easily oxidized, making it difficult to control the crystal form and morphology, resulting in low battery capacity and voltage and poor cycle performance; on the other hand, as the reaction time increases, the viscosity of the slurry system increases, leading to a wider particle size distribution of the precursor, which affects the overall performance of the product.

[0005] Researchers have also conducted studies on the preparation of precursors for sodium-ion battery cathode materials. For example, patent application CN115924980A discloses a method for preparing a layered cathode material precursor for iron-based sodium-ion batteries using composite phosphate. However, this method has two drawbacks: firstly, the excessive amount of additives increases the difficulty of subsequent wastewater treatment, thus increasing costs; secondly, the battery capacity prepared using this method is relatively low. For instance, patent application CN115818737A discloses a nickel-iron-manganese ternary precursor, its preparation method, and its application. The precursor prepared by this patent has primary particles that are sheet-like, and secondary particles with poor sphericity, resulting in low tap density of the precursor and affecting the electrochemical performance of the cathode material. For example, patent application CN 115594233A discloses a precursor of a quaternary cathode material for sodium-ion batteries, its preparation method and application. The preparation method of this patent uses a mixed salt of nickel, iron, manganese and magnesium to be simultaneously and concurrently introduced into the reactor for reaction. Due to the large difference in precipitation constants of the four elements, it is difficult to achieve co-precipitation, which makes it difficult to control the morphology and particle size distribution of the precursor, ultimately affecting the physicochemical properties of the precursor. Summary of the Invention

[0006] The purpose of this invention is to solve the above-mentioned problems existing in the prior art and to provide a preparation process for magnesium-doped modified nickel-iron-manganese-based precursor materials. This invention adopts a process of adding antioxidants and complexing agents to the reaction substrate, using nickel-iron-manganese to first carry out nucleation and growth reactions to generate crystal nuclei, and then introducing magnesium salts to deposit and grow on the surface of the crystal nuclei. This not only prevents the four elements of nickel, iron, manganese and magnesium from being difficult to achieve co-precipitation, but also allows for controllable morphology and particle size distribution of the precursor, and the process has good stability.

[0007] This invention utilizes magnesium-modified doped nickel-iron-manganese-based materials and employs an intermittent process to prepare sodium-electric precursors. By controlling factors such as the solid content, flow rate, and pH value of the reactants, the structure and morphology of the crystals can be precisely regulated. At the same time, the particle size distribution of the precursor can be well adjusted, thereby preparing sodium-electric precursor materials with uniform particle size.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] A process for preparing a magnesium-doped modified nickel-iron-manganese-based precursor material includes the following steps:

[0010] (1) Solution preparation: Prepare a nickel-iron-manganese-magnesium metal salt solution with a total metal ion concentration of 1-3 mol / L. Specifically, prepare a mixed salt solution by preparing soluble nickel salt, soluble iron salt, and soluble manganese salt, and prepare a soluble magnesium salt solution by preparing a soluble magnesium salt solution; prepare an ammonia complexing agent with a concentration of 2-5 mol / L; prepare an alkaline solution with a NaOH concentration of 2-5 mol / L.

[0011] (2) Preparation of reaction base solution: Add deionized water to the reaction vessel, add the prepared alkaline solution and ammonia complexing agent to the reaction vessel, adjust the alkalinity of the system to 3.0-8.0 g / L, and adjust the pH value to 10-11.5;

[0012] (3) Feeding: The mixed salt solution, ammonia complexing agent, and alkaline solution are fed into the reactor of step (2) under N2 atmosphere protection and at a speed of 200-400 r / min. The feed flow rate of the mixed salt solution is 5-100 ml / h, the feed flow rate of the ammonia complexing agent is 0.5-30 ml / h, and the feed flow rate of the alkaline solution is 2-50 ml / h.

[0013] (4) Nucleation reaction: In the reaction vessel of step (3), the solution temperature is controlled at 50-70℃, pH is 10-11.5, alkalinity is 3.0-8.0g / L, and rotation speed is 200-400r / min. The reaction is continuously fed for 0.5-2h to obtain crystal nuclei.

[0014] (5) Growth reaction: In the reactor of step (4), the feed flow rate of the mixed salt solution is adjusted to 7.5-30 ml / h, the feed flow rate of the ammonia complexing agent is adjusted to 1.0-20 ml / h, and the feed flow rate of the alkaline solution is adjusted to 3-16 ml / h. The temperature of the solution in the reactor is controlled at 50-70℃, pH is 10-10.8, alkalinity is 3.0-8.0 g / L, and rotation speed is 200-400 r / min. The reaction is carried out for 2-48 hours to allow the crystal nuclei to grow.

[0015] (6) Magnesium doping modification: While maintaining the conditions of step (5), the soluble magnesium salt solution is pumped into the reactor at a flow rate of 7.5-30 ml / h and reacted for 8-12 h to allow crystal growth.

[0016] (7) Aging reaction: After the crystals from step (6) have grown to a D50 of 4-5 μm, add 40-200 ml of alkaline solution to the reactor at a feed flow rate of 20-60 ml / h and a rotation speed of 200-400 r / min. After the alkaline solution is added, continue aging for 8-12 h at a rotation speed of 200-400 r / min and a temperature of 50-70 °C.

[0017] (8) Washing: Filter the solution in the reactor to obtain the filter solid. Wash the filter solid repeatedly with deionized water until the pH value of the washing deionized water is less than 8.2 to obtain the washed crystals.

[0018] (9) Drying: The washed crystals are dried to obtain magnesium-doped modified nickel-iron-manganese-based precursor materials.

[0019] Furthermore, in step (1), a nickel-iron-manganese-magnesium metal salt solution with a total metal ion concentration of 1-3 mol / L is prepared according to the molar ratio of x:y:z:1-xyz, where 0.1≤x≤0.3, 0.1≤y≤0.3, and 0.1≤z≤0.3.

[0020] Furthermore, in step (1), the soluble nickel salt is NiSO4·6H2O with industrial grade purity (nickel content of 22.2%); the soluble iron salt is FeSO4·7H2O (iron content of 17%) with industrial grade purity; the soluble manganese salt is MnSO4·H2O with industrial grade purity (manganese content of 32%); and the soluble magnesium salt is MgSO4·7H2O with industrial grade purity (MgSO4·7H2O content of 93%).

[0021] Furthermore, in step (1), the ammonia complexing agent is a mixed solution formed by dissolving ammonia in water, with a molar concentration of 4 mol / L.

[0022] Furthermore, in step (2), deionized water is introduced into the reaction vessel, and then a reducing agent of 1-3‰ of the total mass of soluble nickel salt, soluble iron salt, soluble manganese salt, and soluble magnesium salt is added. The reducing agent is one of ascorbic acid, sodium ascorbate, and hydrazine hydrate. The prepared alkaline solution and ammonia complexing agent are added to the reaction base liquid to adjust the alkalinity of the system to 3.0-8.0 g / L and the pH value to 10-11.5.

[0023] Furthermore, in step (2), deionized water is introduced into the reactor, and then 1-5‰ of the total mass of soluble nickel salt, soluble iron salt, soluble manganese salt, and soluble magnesium salt of PVP is added. Finally, the prepared alkaline solution and ammonia complexing agent are added to the reaction base liquid to adjust the alkalinity of the system to 3.0-8.0 g / L and the pH value to 10-11.5.

[0024] Furthermore, in step (9), the drying temperature is 100-130℃ and the drying time is 4-6h.

[0025] Furthermore, the growth reaction in step (5) is carried out using a two-stage process: Stage I: In the reactor of step (4), the flow rate of the mixed salt solution is adjusted to 8-12 ml / h, the flow rate of the alkali solution is 3-4 ml / h, and the flow rate of the ammonia complexing agent is 1.0-1.2 ml / h. The temperature of the solution in the reactor is controlled at 58-62℃, the pH is 10.3-10.4, the alkalinity is 4.5-5.5 g / L, and the rotation speed is 280-300 r / min. Under the conditions of n, react for 10-15 hours; Section II: Adjust the flow rate of the mixed salt solution to 28-30 ml / h, the flow rate of the alkali solution to 7-8 ml / h, and the flow rate of the ammonia complexing agent to 1.8-2 ml / h. Control the temperature of the solution in the reactor to 58-60℃, pH to 10.2-10.3, alkalinity to 4.5-5.5 g / L, and rotation speed to 280-300 r / min, and react for 22-25 hours to allow crystal nuclei to grow.

[0026] Another object of the present invention is to provide a magnesium-doped modified nickel-iron-manganese-based precursor material prepared by the above preparation method.

[0027] The present invention also provides a positive electrode material for a sodium-ion battery, wherein the positive electrode material is made by combining the magnesium-doped modified nickel-iron-manganese-based precursor material with a sodium-containing material.

[0028] The beneficial effects of this invention are as follows:

[0029] In the coprecipitation method for preparing sodium-ion battery precursor materials, the Ksp constants of Ni(OH)₂, Fe(OH)₂, and Mn(OH)₂ are not on the same order of magnitude. Therefore, achieving coprecipitation is a technical challenge in this method. This invention addresses this challenge by adding a certain concentration of ammonia as a complexing agent to achieve coprecipitation of Ni(OH)₂. 2+ Fe 2+ Mn 2+ The complexation reaction occurs first, followed by the precipitation reaction. By controlling the chemical reaction rate to induce co-precipitation, the morphology and particle size distribution of the precursor can be well controlled.

[0030] This invention adds a reducing agent and a dispersant (PVP) to the reaction substrate, and uses magnesium-modified doped nickel-iron-manganese-based materials to prepare sodium-electric precursors using an intermittent process. By controlling factors such as the solid content, flow rate, and pH value of the reactants, the structure and morphology of the crystals can be precisely controlled. At the same time, the particle size distribution of the precursor can be well adjusted, thereby preparing sodium-electric precursor materials with uniform particle size.

[0031] The present invention adds a certain amount of reducing agent (ascorbic acid, sodium ascorbate, hydrazine hydrate, etc.) to the base solution to prevent the oxidation of ferrous ions, thereby controlling the crystal form and morphology of the precursor.

[0032] As the reaction time increases, the viscosity of the slurry system rises. This invention reduces the surface tension of the slurry system by adding PVP (polyvinylpyrrolidone) to the reaction substrate, thereby enhancing the dispersibility of the slurry system and making Mg... 1-x-y-z Ni x Fe y Mn z The particle size distribution of (OH)2 precursor is controllable.

[0033] This invention improves battery capacity and voltage, and enhances battery cycle performance by modifying nickel-iron-manganese-based materials with magnesium doping.

[0034] Compared with continuous preparation methods, the batch preparation method of the present invention can reduce the amount of solvent used in the reaction, thereby greatly reducing the amount of wastewater to be treated, and thus saving a lot of costs. Attached Figure Description

[0035] Figure 1 Ni obtained in Example 1 of this invention 0.3 Fe 0.3 Mn 0.3 Magnified image of (OH)2 crystal nuclei;

[0036] Figure 2 The precursor material Mg obtained in Example 1 of this invention 0.1 Ni 0.3 Fe 0.3 Mn 0.3 SEM image of (OH)2;

[0037] Figure 3 The precursor material Mg obtained in Example 1 of this invention 0.1 Ni 0.3 Fe 0.3 Mn 0.3 Particle size distribution diagram of (OH)2;

[0038] Figure 4 Ni is the precursor material prepared in Comparative Example 1 of this invention. 0.3 Fe 0.3 Mn 0.3 SEM image of (OH)2;

[0039] Figure 5 The precursor material Mg prepared in Comparative Example 2 of this invention 0.1 Ni 0.3 Fe 0.3 Mn 0.3 SEM image of (OH)2;

[0040] Figure 6 The precursor material Mg prepared in Comparative Example 3 of this invention is... 0.1 Ni 0.3 Fe0.3 Mn 0.3 SEM image of (OH)2;

[0041] Figure 7 The precursor material Mg prepared in Comparative Example 4 of this invention 0.1 Ni 0.3 Fe 0.3 Mn 0.3 SEM image of (OH)2. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0043] A process for preparing a magnesium-doped modified nickel-iron-manganese-based precursor material includes the following steps:

[0044] (1) Solution preparation:

[0045] A nickel-iron-manganese-magnesium metal salt solution with a total metal ion concentration of 1-3 mol / L is prepared according to a molar ratio of x:y:z:1-xyz, wherein 0.1≤x≤0.3, 0.1≤y≤0.3, and 0.1≤z≤0.3. Specifically, a mixed salt solution is prepared from soluble nickel salt, soluble iron salt, and soluble manganese salt, and a soluble magnesium salt solution is prepared from soluble magnesium salt. The soluble nickel salt is nickel sulfate (NiSO4·6H2O) with an industrial purity. The soluble iron salt is ferrous sulfate (FeSO4·7H2O) with an iron content of 17% and an industrial grade purity; the soluble manganese salt is manganese sulfate (MnSO4·H2O) with an industrial grade purity (manganese content of 32%); the soluble magnesium salt is magnesium sulfate (MgSO4·7H2O) with an industrial grade purity (MgSO4·7H2O content of 93%); the sulfates used in the following specific embodiments are the same as those described above.

[0046] Prepare an ammonia complexing agent solution with a concentration of 2-5 mol / L by dissolving ammonia in water to form a mixed aqueous solution;

[0047] Prepare an alkaline solution with a NaOH concentration of 2-5 mol / L by dissolving NaOH in water to form a mixed aqueous solution.

[0048] (2) Preparation of the reaction base solution: Pass a certain mass of deionized water into a 2-5L reactor. Add a reducing agent (such as one of ascorbic acid, sodium ascorbate, or hydrazine hydrate) at a mass of 1-3‰ of the total mass of soluble salts (i.e., the sum of soluble nickel salts, soluble iron salts, soluble manganese salts, and soluble magnesium salts). Then add PVP (polyvinylpyrrolidone) at a mass of 1-5‰ of the total mass of soluble salts (i.e., the sum of soluble nickel salts, soluble iron salts, soluble manganese salts, and soluble magnesium salts). Finally, add the prepared alkaline solution and ammonia complexing agent solution to the reaction base solution to adjust the alkalinity of the system to 3.0-8.0 g / L and the pH value to 10-11.5.

[0049] (3) Feeding: The mixed salt solution, ammonia complexing agent solution and alkaline solution prepared in step (1) are fed into the reactor of step (2) under N2 atmosphere protection and at a speed of 200-400 r / min. The feed flow rate of the mixed salt solution is 5-100 ml / h, the feed flow rate of the ammonia complexing agent solution is 0.5-30 ml / h, and the feed flow rate of the alkaline solution is 2-50 ml / h.

[0050] (4) Nucleation reaction: In the reactor of step (3), the solution temperature is controlled at 50-70℃, pH is 10-11.5, alkalinity is 3.0-8.0 g / L, and rotation speed is 200-400 r / min. The reaction is continuously fed for 0.5-2 h to obtain Ni. x Fe y Mn z (OH)2 crystal nuclei.

[0051] (5) Growth reaction: In the reactor of step (4), the feed flow rate of the mixed salt solution is adjusted to 7.5-30 ml / h, the feed flow rate of the ammonia complexing agent solution is adjusted to 1.0-20 ml / h, and the feed flow rate of the alkali solution is adjusted to 3-16 ml / h. The temperature of the solution in the reactor is controlled at 50-70℃, pH is 10-10.8, alkalinity is 3.0-8.0 g / L, and rotation speed is 200-400 r / min. The reaction is carried out continuously for 2-48 hours to allow Ni to grow. x Fe y Mn z (OH)2 crystal nucleus growth.

[0052] (6) Magnesium doping modification: In the reactor of step (5), while reacting according to the feeding conditions of step (5), a soluble magnesium salt solution is pumped at a flow rate of 7.5-30 ml / h into the reactor at a temperature of 50-70℃, pH of 10-10.8, alkalinity of 3.0-8.0 g / L, and rotation speed of 200-400 r / min. The reaction is carried out for 8-12 h to allow Mg to be doped and modified. 1-x-y-z Ni x Fe y Mnz (OH)2 crystal growth.

[0053] (7) Aging reaction: Mg to be processed in step (6) 1-x-y-z Ni x Fe y Mn z After the (OH)2 crystals grow to a D50 of 4-5 μm, add 40-200 ml of 2-5 mol / L NaOH alkaline solution to the reactor at a flow rate of 20-60 ml / h and a rotation speed of 200-400 r / min. After the alkaline solution is added, continue aging for 8-12 h at a rotation speed of 200-400 r / min and a temperature of 50-70 °C.

[0054] (8) Washing: Based on step (7), shut down the reactor and filter the solution in the reactor to obtain Mg. 1-x-y-z Ni x Fe y Mn z (OH)2 solid, filter Mg 1-x-y-z Ni x Fe y Mn z The (OH)2 solid should be washed repeatedly with deionized water 5-10 times until the pH value of the washing deionized water is less than 8.2 before washing can be stopped.

[0055] (9) Drying: Based on step (8), Mg 1-x-y-z Ni x Fe y Mn z (OH)₂ crystals were dried at 100-130℃ for 4-6 hours to obtain magnesium-doped modified nickel-iron-manganese-based precursor material Mg. 1-x-y-z Ni x Fe y Mn z (OH)2.

[0056] Example 1

[0057] A process for preparing a magnesium-doped modified nickel-iron-manganese-based precursor material includes the following steps:

[0058] (1) Solution preparation: Prepare a mixed salt solution of nickel, iron and manganese with a total metal ion concentration of 2 mol / L and a volume of 0.5 L, and a magnesium sulfate solution with a volume of 0.5 L (for later use) by mixing magnesium sulfate, nickel sulfate, ferrous sulfate and manganese sulfate in a molar ratio of 0.1:0.3:0.3:0.3. Prepare a 4 mol / L ammonia complexing agent solution and a 4 mol / L NaOH alkaline solution.

[0059] (2) Preparation of reaction base solution: A certain mass of deionized water was introduced into a 3L reactor. 0.461g of reducing agent ascorbic acid was added to the reactor. On this basis, 0.69g of PVP was added. Finally, the prepared NaOH alkaline solution and ammonia complexing agent solution were added to the reaction base solution to adjust the alkalinity of the system to 5.0g / L and the pH value to 11.2.

[0060] (3) Feeding: The nickel-iron-manganese mixed salt solution prepared in step (1) is added to the reactor in step (2) under N2 atmosphere protection and rotating at 300 r / min at a feed flow rate of 6.7 ml / h, the ammonia complexing agent solution is added to a feed flow rate of 0.7 mL / h, and the NaOH alkaline solution is added to a feed flow rate of 2.7 ml / h.

[0061] (4) Nucleation reaction: In the reactor of step (3), the temperature of the solution in the reactor is controlled at 60℃, pH is 11.2, alkalinity is 5.0 g / L, and rotation speed is 300 r / min. The reaction is carried out continuously under the feeding conditions of step (3) for 2 hours to obtain Ni. 0.3 Fe 0.3 Mn 0.3 (OH)2 crystal nuclei;

[0062] (5) Growth reaction: Ni is grown using a two-stage process. 0.3 Fe 0.3 Mn 0.3 The (OH)2 nucleus growth reaction is carried out first in section I and then in section II. Section I: In the reactor of step (4), the flow rate of the nickel-iron-manganese mixed salt solution is adjusted to 10 ml / h, the flow rate of the NaOH alkaline solution is 4 ml / h, and the flow rate of the ammonia complexing agent solution is 1.2 ml / h. The temperature of the solution in the reactor is controlled at 60℃, pH is 10.32, alkalinity is 5.0 g / L, and the rotation speed is 290 r / min for 12 h. Section II: The flow rate of the nickel-iron-manganese mixed salt solution is adjusted to 30 ml / h, the flow rate of the NaOH alkaline solution is 8 ml / h, and the flow rate of the ammonia complexing agent solution is 2 ml / h. The temperature of the solution in the reactor is controlled at 60℃, pH is 10.20, alkalinity is 5.0 g / L, and the rotation speed is 280 r / min for 24 h, so that Ni 0.3 Fe 0.3 Mn 0.3 (OH)₂ crystal nucleation growth;

[0063] (6) Mg doping modification: In the reactor of step (5), while reacting according to the feeding conditions of section II, magnesium sulfate solution is pumped into the reactor at a flow rate of 9.48 ml / h at a temperature of 60℃, pH of 10.2, alkalinity of 5.0 g / L, and rotation speed of 280 r / min. The reaction is carried out for 10 h to allow Mg doping modification. 0.1 Ni0.3 Fe 0.3 Mn 0.3 (OH)₂ crystal growth;

[0064] (7) Aging reaction: Mg to be processed in step (6) 0.1 Ni 0.3 Fe 0.3 Mn 0.3 After the (OH)2 crystals grow to a D50 of 4-5 μm, a 4 mol / L NaOH alkaline solution is added to the reactor at a flow rate of 50 ml / h and a rotation speed of 200 r / min. After 2 h of adding the NaOH alkaline solution, the reactor is aged for another 10 h at a rotation speed of 200 r / min and a temperature of 50-70 °C.

[0065] (8) Washing: Based on step (7), shut down the reactor and filter the solution in the reactor to obtain Mg. 0.1 Ni 0.3 Fe 0.3 Mn 0.3 (OH)2 solid, Mg 0.1 Ni 0.3 Fe 0.3 Mn 0.3 The (OH)₂ solid was washed repeatedly with deionized water 10 times until the pH of the washing deionized water was less than 8.2, at which point the washing could be stopped to obtain Mg. 0.1 Ni 0.3 Fe 0.3 Mn 0.3 (OH)2 crystals;

[0066] (9) Drying: Based on step (8), Mg 0.1 Ni 0.3 Fe 0.3 Mn 0.3 (OH)₂ crystals were dried at 120℃ for 4 hours to obtain magnesium-doped modified nickel-iron-manganese-based precursor material Mg. 0.1 Ni 0.3 Fe 0.3 Mn 0.3 (OH)2.

[0067] like Figure 1 As shown, this is the Ni prepared in Example 1. 0.3 Fe 0.3 Mn 0.3 The magnified image of (OH)2 crystal nuclei shows that the crystal nuclei are clearly distributed and there is no agglomeration.

[0068] like Figure 2 As shown, the precursor material Mg prepared in Example 1 is shown. 0.1 Ni 0.3Fe 0.3 Mn 0.3 The SEM image of (OH)2 shows that the primary precursor particles are thick plates, and the secondary particles have good sphericity, with no twinning or segregation.

[0069] like Figure 3 As shown, the precursor material Mg prepared in Example 1 is shown. 0.1 Ni 0.3 Fe 0.3 Mn 0.3 The particle size distribution diagram of (OH)2 shows that the particle size distribution is controllable.

[0070] Example 2

[0071] A process for preparing a magnesium-doped modified nickel-iron-manganese-based precursor material includes the following steps:

[0072] (1) Solution preparation: Prepare a mixed salt solution of nickel, iron and manganese with a total metal ion concentration of 2 mol / L and a volume of 0.5 L, and a magnesium sulfate solution with a volume of 0.5 L (for later use) by mixing magnesium sulfate, nickel sulfate, ferrous sulfate and manganese sulfate in a molar ratio of 0.15:0.3:0.25:0.3. Prepare a 4 mol / L ammonia complexing agent solution and a 4 mol / L NaOH alkaline solution.

[0073] (2) Preparation of reaction base solution: A certain mass of deionized water was introduced into a 3L reaction vessel. 0.44g of reducing agent sodium ascorbate was added to the reaction vessel. On this basis, 0.65g of PVP was added. Finally, the prepared NaOH alkaline solution and ammonia complexing agent solution were added to the reaction base solution to adjust the alkalinity of the system to 5.0g / L and the pH value to 11.2.

[0074] (3) Feeding: The nickel-iron-manganese mixed salt solution prepared in step (1) is added to the reactor of step (2) under N2 atmosphere protection and rotating at 300 r / min at a feed flow rate of 6.7 ml / h, the ammonia complexing agent solution is added to a feed flow rate of 0.69 mL / h, and the NaOH alkaline solution is added to a feed flow rate of 2.68 ml / h.

[0075] (4) Nucleation reaction: In the reactor of step (3), the temperature of the solution in the reactor is controlled at 60℃, pH is 11.2, alkalinity is 5.0 g / L, and rotation speed is 300 r / min for 2 h to obtain Ni. 0.3 Fe 0.25 Mn 0.3 (OH)2 crystal nuclei;

[0076] (5) Growth reaction: Ni is grown using a two-stage process. 0.3 Fe 0.25 Mn 0.3(OH)2 nucleus growth reaction; first, proceed to section I: in the reactor of step (4), adjust the flow rate of the nickel-iron-manganese mixed salt solution to 10 ml / h, the flow rate of the NaOH alkaline solution to 3.9 ml / h, and the flow rate of the ammonia complexing agent solution to 1.1 ml / h, and control the solution temperature at 60℃, pH at 10.32, alkalinity at 5.0 g / L, and rotation speed at 290 r / min for 12 h; then proceed to section II: adjust the flow rate of the nickel-iron-manganese mixed salt solution to 30 ml / h, the flow rate of the NaOH alkaline solution to 7.8 ml / h, and the flow rate of the ammonia complexing agent solution to 1.9 ml / h, and control the solution temperature at 60℃, pH at 10.20, alkalinity at 5.0 g / L, and rotation speed at 280 r / min for 24 h, so that Ni 0.3 Fe 0.25 Mn 0.3 (OH)₂ crystal nucleation growth;

[0077] (6) Mg doping modification: In the reactor of step (5), while reacting according to the feeding conditions of section II, magnesium sulfate solution is pumped into the reactor at a flow rate of 15.06 ml / h at a temperature of 60℃, pH of 10.2, alkalinity of 5.0 g / L, and rotation speed of 280 r / min. The reaction is carried out for 10 h to allow Mg doping modification. 0.15 Ni 0.3 Fe 0.25 Mn 0.3 (OH)₂ crystal growth;

[0078] (7) Aging reaction: Mg from step (6) 0.15 Ni 0.3 Fe 0.25 Mn 0.3 After the (OH)2 crystals grow to a D50 of 4-5 μm, a 4 mol / L NaOH alkaline solution is added to the reactor at a flow rate of 50 ml / h and a rotation speed of 200 r / min. After 2 h of adding the NaOH alkaline solution, the reactor is aged for another 10 h at a rotation speed of 200 r / min and a temperature of 50-70 °C.

[0079] (8) Washing: Based on step (7), shut down the reactor and filter the solution in the reactor to obtain Mg. 0.15 Ni 0.3 Fe 0.25 Mn 0.3 (OH)2 solid, filter Mg 0.15 Ni 0.3 Fe 0.25 Mn 0.3 The (OH)2 solid was washed repeatedly with deionized water 10 times until the pH value of the washing deionized water was less than 8.2 before washing was stopped.

[0080] (9) Drying: Based on step (8), Mg 0.15 Ni 0.3 Fe 0.25 Mn 0.3 (OH)₂ crystals were dried at 120℃ for 4 hours to obtain magnesium-doped modified nickel-iron-manganese-based precursor material Mg. 0.15 Ni 0.3 Fe 0.25 Mn 0.3 (OH)2.

[0081] Example 3

[0082] A process for preparing a magnesium-doped modified nickel-iron-manganese-based precursor material includes the following steps:

[0083] (1) Solution preparation: Prepare a mixed salt solution of nickel, iron and manganese with a total metal ion concentration of 2 mol / L and a volume of 0.5 L, and a magnesium sulfate solution with a volume of 0.5 L (for later use) by mixing magnesium sulfate, nickel sulfate, ferrous sulfate and manganese sulfate in a molar ratio of 0.2:0.3:0.2:0.3. Prepare a 4 mol / L ammonia complexing agent solution and a 4 mol / L NaOH alkaline solution.

[0084] (2) Preparation of reaction base solution: A certain mass of deionized water was introduced into a 3L reactor. 0.423g of reducing agent hydrazine hydrate was added to the reactor. On this basis, 0.62g of PVP was added. Finally, the prepared NaOH alkaline solution and ammonia complexing agent solution were added to the reaction base solution to adjust the alkalinity of the system to 5.0g / L and the pH value to 11.2.

[0085] (3) Feeding: The nickel-iron-manganese mixed salt solution prepared in step (1) is added at a feed flow rate of 6.7 ml / h, the ammonia complexing agent solution at a feed flow rate of 0.64 mL / h, and the NaOH alkaline solution at a feed flow rate of 2.67 ml / h to the reactor in step (2) under N2 atmosphere protection and at a rotation speed of 300 r / min.

[0086] (4) Nucleation reaction: In the reactor of step (3), the solution temperature was controlled at 60℃, pH at 11.2, alkalinity at 5.0 g / L, and rotation speed at 300 r / min for 2 h to obtain Ni. 0.3 Fe 0.2 Mn 0.3 (OH)2 crystal nuclei;

[0087] (5) Growth reaction: Ni is grown using a two-stage process. 0.3 Fe 0.2 Mn 0.3(OH)2 nucleation reaction; Section I: In the reactor of step (4), adjust the flow rate of the nickel-iron-manganese mixed salt solution to 10 ml / h, the flow rate of the NaOH alkaline solution to 3.8 ml / h, and the flow rate of the ammonia complexing agent solution to 1 ml / h, and control the solution temperature at 60℃, pH 10.32, alkalinity 5.0 g / L, and rotation speed 290 r / min for 12 h; Section II: Adjust the flow rate of the nickel-iron-manganese mixed salt solution to 30 ml / h, the flow rate of the NaOH alkaline solution to 7.6 ml / h, and the flow rate of the ammonia complexing agent solution to 1.8 ml / h, and control the solution temperature at 60℃, pH 10.20, alkalinity 5.0 g / L, and rotation speed 280 r / min for 24 h, so that Ni 0.3 Fe 0.2 Mn 0.3 (OH)₂ crystal nucleation growth;

[0088] (6) Mg doping modification: In the reactor of step (5), while the reaction is being carried out according to section II, magnesium sulfate solution is pumped into the reactor at a temperature of 60℃, pH of 10.2, alkalinity of 5.0 g / L, and rotation speed of 280 r / min at a flow rate of 21.34 ml / h. The reaction is carried out for 10 h to allow Mg doping modification. 0.15 Ni 0.3 Fe 0.25 Mn 0.3 (OH)₂ crystal growth;

[0089] (7) Aging reaction: The Mg from step (6) 0.2 Ni 0.3 Fe 0.2 Mn 0.3 After the (OH)2 crystals grow to a D50 of 4-5 μm, a 4 mol / L NaOH alkaline solution is added to the reactor at a flow rate of 50 ml / h and a rotation speed of 200 r / min. After 2 h of adding the NaOH alkaline solution, the reactor is aged for another 10 h at a rotation speed of 200 r / min and a temperature of 50-70 °C.

[0090] (8) Washing: Based on step (7), shut down the reactor and filter the solution in the reactor to obtain Mg. 0.2 Ni 0.3 Fe 0.2 Mn 0.3 (OH)2 solid, filter Mg 0.2 Ni 0.3 Fe 0.2 Mn 0.3 The (OH)2 solid was washed repeatedly with deionized water 10 times until the pH value of the washing deionized water was less than 8.2 before washing was stopped.

[0091] (9) Drying: Based on step (8), Mg 0.2 Ni 0.3 Fe 0.2 Mn 0.3 (OH)₂ crystals were dried at 120℃ for 4 hours to obtain magnesium-doped modified nickel-iron-manganese-based precursor material Mg. 0.2 Ni 0.3 Fe 0.2 Mn 0.3 (OH)2.

[0092] Comparative Example 1

[0093] A process for preparing a nickel-iron-manganese-based precursor material includes the following steps:

[0094] (1) Solution preparation: Prepare a nickel-iron-manganese mixed salt solution (for later use) with a total metal ion concentration of 2 mol / L and a volume of 1 L by mixing nickel sulfate, ferrous sulfate and manganese sulfate in a molar ratio of 0.3:0.3:0.3. Prepare a 4 mol / L ammonia complexing agent solution and a 4 mol / L NaOH alkaline solution.

[0095] (2) Preparation of reaction base solution: A certain mass of deionized water was introduced into a 3L reactor. 0.461g of reducing agent ascorbic acid was added to the reactor. On this basis, 0.69g of PVP was added. Finally, the prepared NaOH alkaline solution and ammonia complexing agent solution were added to the reaction base solution to adjust the alkalinity of the system to 5.0g / L and the pH value to 11.2.

[0096] (3) Feeding: The nickel-iron-manganese mixed salt solution prepared in step (1) is added to the reactor in step (2) under N2 atmosphere protection and rotating at 300 r / min at a feed flow rate of 6.7 ml / h, the ammonia complexing agent solution is added to a feed flow rate of 0.7 mL / h, and the NaOH alkaline solution is added to a feed flow rate of 2.7 ml / h.

[0097] (4) Nucleation reaction: In the reactor of step (3), the temperature of the solution in the reactor is controlled at 60℃, pH is 11.2, alkalinity is 5.0 g / L, and rotation speed is 300 r / min. The reaction is carried out continuously under the feeding conditions of step (3) for 2 hours to obtain Ni. 0.3 Fe 0.3 Mn 0.3 (OH)2 crystal nuclei;

[0098] (5) Growth reaction: Ni is grown using a two-stage process. 0.3 Fe 0.3 Mn 0.3The (OH)2 nucleation reaction is carried out in Section I first, followed by Section II. Section I: In the reactor of step (4), the flow rate of the nickel-iron-manganese mixed salt solution is adjusted to 10 ml / h, the flow rate of the NaOH alkaline solution is 4 ml / h, and the flow rate of the ammonia complexing agent solution is 1.2 ml / h. The temperature of the solution in the reactor is controlled at 60℃, pH is 10.32, alkalinity is 5.0 g / L, and the rotation speed is 290 r / min for 12 h. Section II: The flow rate of the nickel-iron-manganese mixed salt solution is adjusted to 30 ml / h, the flow rate of the NaOH alkaline solution is 8 ml / h, and the flow rate of the ammonia complexing agent solution is 2 ml / h. The temperature of the solution in the reactor is controlled at 60℃, pH is 10.20, alkalinity is 5.0 g / L, and the rotation speed is 280 r / min for 24 h, so that Ni 0.3 Fe 0.3 Mn 0.3 (OH)₂ crystal nucleation growth;

[0099] (6) Aging reaction: Ni to be processed in step (5) 0.3 Fe 0.3 Mn 0.3 After the (OH)2 crystals grow to a D50 of 4-5 μm, a 4 mol / L NaOH alkaline solution is added to the reactor at a flow rate of 50 ml / h and a rotation speed of 200 r / min. After 2 h of adding the NaOH alkaline solution, the reactor is aged for another 10 h at a rotation speed of 200 r / min and a temperature of 50-70 °C.

[0100] (7) Washing: Based on step (6), shut down the reactor and filter the solution in the reactor to obtain the filtrate Ni. 0.3 Fe 0.3 Mn 0.3 (OH)2 solid, filter material Ni 0.3 Fe 0.3 Mn 0.3 The (OH)2 solid was washed repeatedly with deionized water 10 times until the pH value of the washing deionized water was less than 8.2 before washing was stopped.

[0101] (8) Drying: Based on step (7), Ni 0.3 Fe 0.3 Mn 0.3 (OH)₂ crystals were dried at 120℃ for 4 hours to obtain the nickel-iron-manganese-based precursor material Ni. 0.3 Fe 0.3 Mn 0.3 (OH)2.

[0102] This comparative example is based on Example 1, but without the addition of magnesium. Figure 4 As shown, Ni is the precursor material prepared in Comparative Example 1.0.3 Fe 0.3 Mn 0.3 The SEM image of (OH)2 shows that, due to the absence of magnesium doping, the magnesium sites in the crystal structure are replaced by nickel, iron, and manganese, resulting in thinner primary particles, disordered crystal orientation, poorer precursor morphology, and lower tap.

[0103] Comparative Example 2

[0104] A process for preparing a magnesium-doped modified nickel-iron-manganese-based precursor material includes the following steps:

[0105] (1) Solution preparation: Prepare a magnesium-nickel-iron-manganese mixed salt solution (for later use) with a total metal ion concentration of 2 mol / L and a volume of 1 L by mixing magnesium sulfate, nickel sulfate, ferrous sulfate and manganese sulfate in a molar ratio of 0.1:0.3:0.3:0.3. Prepare a 4 mol / L ammonia complexing agent solution and a 4 mol / L NaOH alkaline solution.

[0106] (2) Preparation of reaction base solution: A certain mass of deionized water was introduced into a 3L reactor. 0.461g of reducing agent ascorbic acid was added to the reactor. On this basis, 0.69g of PVP was added. Finally, the prepared NaOH alkaline solution and ammonia complexing agent solution were added to the reaction base solution to adjust the alkalinity of the system to 5.0g / L and the pH value to 11.2.

[0107] (3) Feeding: The magnesium-nickel-iron-manganese mixed salt solution prepared in step (1) is added to the reactor in step (2) under N2 atmosphere protection and rotating at 300 r / min at a feed flow rate of 6.7 ml / h, the ammonia complexing agent solution is added to a feed flow rate of 0.7 mL / h, and the NaOH alkaline solution is added to a feed flow rate of 2.7 ml / h.

[0108] (4) Nucleation reaction: In the reactor of step (3), the temperature of the solution in the reactor is controlled at 60℃, pH is 11.2, alkalinity is 5.0 g / L, and rotation speed is 300 r / min. The reaction is carried out continuously under the feeding conditions of step (3) for 2 hours to obtain Mg 0.1 Ni 0.3 Fe 0.3 Mn 0.3 (OH)2 crystal nuclei;

[0109] (5) Growth reaction: A two-stage process is used for Mg growth. 0.1 Ni 0.3 Fe 0.3 Mn 0.3The (OH)2 nucleation reaction is carried out in Section I first, followed by Section II. Section I: In the reactor of step (4), the flow rate of the magnesium-nickel-iron-manganese mixed salt solution is adjusted to 10 ml / h, the flow rate of the NaOH alkaline solution is 4 ml / h, and the flow rate of the ammonia complexing agent solution is 1.2 ml / h. The temperature of the solution in the reactor is controlled at 60℃, pH is 10.32, alkalinity is 5.0 g / L, and the rotation speed is 290 r / min for 12 h. Section II: The flow rate of the magnesium-nickel-iron-manganese mixed salt solution is adjusted to 30 ml / h, the flow rate of the NaOH alkaline solution is 8 ml / h, and the flow rate of the ammonia complexing agent solution is 2 ml / h. The temperature of the solution in the reactor is controlled at 60℃, pH is 10.20, alkalinity is 5.0 g / L, and the rotation speed is 280 r / min for 24 h, so that Mg 0.1 Ni 0.3 Fe 0.3 Mn 0.3 (OH)₂ crystal nucleation growth;

[0110] (6) Aging reaction: Mg to be processed in step (5) 0.1 Ni 0.3 Fe 0.3 Mn 0.3 After the (OH)2 crystals grow to a D50 of 4-5 μm, a 4 mol / L NaOH alkaline solution is added to the reactor at a flow rate of 50 ml / h and a rotation speed of 200 r / min. After 2 h of adding the NaOH alkaline solution, the reactor is aged for another 10 h at a rotation speed of 200 r / min and a temperature of 50-70 °C.

[0111] (7) Washing: Based on step (6), shut down the reactor and filter the solution in the reactor to obtain Mg. 0.1 Ni 0.3 Fe 0.3 Mn 0.3 (OH)2 solid, filter Mg 0.1 Ni 0.3 Fe 0.3 Mn 0.3 The (OH)2 solid was washed repeatedly with deionized water 10 times until the pH value of the washing deionized water was less than 8.2 before washing was stopped.

[0112] (8) Drying: Based on step (7), Mg 0.1 Ni 0.3 Fe 0.3 Mn 0.3 (OH)₂ crystals were dried at 120℃ for 4 hours to obtain magnesium-doped modified nickel-iron-manganese-based precursor material Mg. 0.1 Ni 0.3 Fe 0.3 Mn0.3 (OH)2.

[0113] This comparative example is based on Example 1, but with the addition of a magnesium doping step to step (1), namely: mixing the soluble magnesium salt with other soluble salts into a mixed salt solution. Figure 5 As shown, the precursor material Mg prepared in Comparative Example 2 is shown. 0.1 Ni 0.3 Fe 0.3 Mn 0.3 The SEM image of (OH)2 shows that when nickel, iron, manganese, and magnesium are mixed together for reaction, the precipitation constants of the four elements differ greatly, making it difficult to form co-precipitates. This results in segregation on the surface of the crystal structure, which affects the electrochemical and physicochemical properties of the cathode material.

[0114] Comparative Example 3

[0115] A process for preparing a magnesium-doped modified nickel-iron-manganese-based precursor material includes the following steps:

[0116] (1) Solution preparation: Prepare a mixed salt solution of nickel, iron and manganese with a total metal ion concentration of 2 mol / L and a volume of 0.5 L, and a magnesium sulfate solution with a volume of 0.5 L (for later use) by mixing magnesium sulfate, nickel sulfate, ferrous sulfate and manganese sulfate in a molar ratio of 0.1:0.3:0.3:0.3. Prepare a 4 mol / L ammonia complexing agent solution and a 4 mol / L NaOH alkaline solution.

[0117] (2) Preparation of reaction base solution: A certain mass of deionized water was introduced into a 3L reactor. 0.461g of reducing agent ascorbic acid was added to the reactor. On this basis, 0.69g of PVP was added. Finally, the prepared NaOH alkaline solution and ammonia complexing agent solution were added to the reaction base solution to adjust the alkalinity of the system to 5.0g / L and the pH value to 11.2.

[0118] (3) Feeding: The nickel-iron-manganese mixed salt solution prepared in step (1) is added to the reactor in step (2) under N2 atmosphere protection and rotating at 300 r / min at a feed flow rate of 6.7 ml / h, the ammonia complexing agent solution is added to a feed flow rate of 0.7 mL / h, and the NaOH alkaline solution is added to a feed flow rate of 2.7 ml / h.

[0119] (4) Nucleation reaction: In the reactor of step (3), the temperature of the solution in the reactor is controlled at 60℃, pH is 11.2, alkalinity is 5.0 g / L, and rotation speed is 300 r / min. The reaction is carried out continuously under the feeding conditions of step (3) for 2 hours to obtain Ni. 0.3 Fe 0.3 Mn 0.3 (OH)2 crystal nuclei;

[0120] (5) Growth reaction: Ni is grown using a single-stage process. 0.3 Fe 0.3 Mn 0.3 (OH)₂ nucleation reaction: In step (4), the flow rate of the nickel-iron-manganese mixed salt solution was adjusted to 20 ml / h, the flow rate of the NaOH alkaline solution was 5.8 ml / h, and the flow rate of the ammonia complexing agent solution was 1.5 ml / h. The temperature of the solution in the reactor was controlled at 60℃, pH at 10.30, alkalinity at 5.0 g / L, and rotation speed at 290 r / min for 36 h to allow Ni to grow. 0.3 Fe 0.3 Mn 0.3 (OH)₂ crystal nucleation growth;

[0121] (6) Mg doping modification: In the reactor of step (5), while reacting according to the feeding conditions of step (5), magnesium sulfate solution is pumped into the reactor at a flow rate of 9.48 ml / h at a temperature of 60℃, pH of 10.2, alkalinity of 5.0 g / L, and rotation speed of 280 r / min. The reaction is carried out for 10 h to allow Mg doping modification. 0.1 Ni 0.3 Fe 0.3 Mn 0.3 (OH)₂ crystal growth;

[0122] (7) Aging reaction: Mg to be processed in step (6) 0.1 Ni 0.3 Fe 0.3 Mn 0.3 After the (OH)2 crystals grow to a D50 of 4-5 μm, a 4 mol / L NaOH alkaline solution is added to the reactor at a flow rate of 50 ml / h and a rotation speed of 200 r / min. After 2 h of adding the NaOH alkaline solution, the reactor is aged for another 10 h at a rotation speed of 200 r / min and a temperature of 50-70 °C.

[0123] (8) Washing: Based on step (7), shut down the reactor and filter the solution in the reactor to obtain Mg. 0.1 Ni 0.3 Fe 0.3 Mn 0.3 (OH)2 solid, filter Mg 0.1 Ni 0.3 Fe 0.3 Mn 0.3 The (OH)2 solid was washed repeatedly with deionized water 10 times until the pH value of the washing deionized water was less than 8.2 before washing was stopped.

[0124] (9) Drying: Based on step (8), Mg 0.1 Ni 0.3 Fe 0.3Mn 0.3 (OH)₂ crystals were dried at 120℃ for 4 hours to obtain magnesium-doped modified nickel-iron-manganese-based precursor material Mg. 0.1 Ni 0.3 Fe 0.3 Mn 0.3 (OH)2.

[0125] This comparative example is based on Example 1, but the two-stage process in step (5) is replaced with a single-stage process. For example... Figure 6 As shown, the precursor material Mg prepared in Comparative Example 3 is shown. 0.1 Ni 0.3 Fe 0.3 Mn 0.3 The SEM image of (OH)2 shows that the change in salt flow rate during the growth process led to a deterioration in the crystal growth of the precursor, resulting in a decrease in sphericity and thus affecting the overall performance of the cathode material.

[0126] Comparative Example 4

[0127] A process for preparing a magnesium-doped modified nickel-iron-manganese-based precursor material includes the following steps:

[0128] (1) Solution preparation: Prepare a mixed salt solution of nickel, iron and manganese with a total metal ion concentration of 2 mol / L and a volume of 0.5 L, and a magnesium sulfate solution with a volume of 0.5 L (for later use) by mixing magnesium sulfate, nickel sulfate, ferrous sulfate and manganese sulfate in a molar ratio of 0.1:0.3:0.3:0.3. Prepare a 4 mol / L ammonia complexing agent solution and a 4 mol / L NaOH alkaline solution.

[0129] (2) Preparation of reaction base solution: A certain mass of deionized water was introduced into a 3L reactor. 0.461g of reducing agent ascorbic acid was added to the reactor. On this basis, 0.69g of PVP was added. Finally, the prepared NaOH alkaline solution and ammonia complexing agent solution were added to the reaction base solution to adjust the alkalinity of the system to 5.0g / L and the pH value to 11.2.

[0130] (3) Feeding: The nickel-iron-manganese mixed salt solution prepared in step (1) is added to the reactor in step (2) under N2 atmosphere protection and rotating at 300 r / min at a feed flow rate of 6.7 ml / h, the ammonia complexing agent solution is added to a feed flow rate of 0.7 mL / h, and the NaOH alkaline solution is added to a feed flow rate of 2.7 ml / h.

[0131] (4) Nucleation reaction: In the reactor of step (3), the temperature of the solution in the reactor is controlled at 60℃, pH is 11.2, alkalinity is 5.0 g / L, and rotation speed is 300 r / min. The reaction is carried out continuously under the feeding conditions of step (3) for 2 hours to obtain Ni.0.3 Fe 0.3 Mn 0.3 (OH)2 crystal nuclei;

[0132] (5) Growth reaction: Ni is grown using a two-stage process. 0.3 Fe 0.25 Mn 0.3 (OH)2 nucleus growth reaction; first, proceed to section I: in the reactor of step (4), adjust the flow rate of the nickel-iron-manganese mixed salt solution to 30 ml / h, the flow rate of the NaOH alkaline solution to 7.8 ml / h, and the flow rate of the ammonia complexing agent solution to 1.9 ml / h, and control the solution temperature at 60℃, pH at 10.20, alkalinity at 5.0 g / L, and rotation speed at 280 r / min for 24 h; then proceed to section II: adjust the flow rate of the nickel-iron-manganese mixed salt solution to 10 ml / h, the flow rate of the NaOH alkaline solution to 3.9 ml / h, and the flow rate of the ammonia complexing agent solution to 1.1 ml / h, and control the solution temperature at 60℃, pH at 10.32, alkalinity at 5.0 g / L, and rotation speed at 290 r / min for 12 h; so that Ni 0.3 Fe 0.25 Mn 0.3 (OH)₂ crystal nucleation growth;

[0133] (6) Mg doping modification: In the reactor of step (5), while reacting according to the feeding conditions of step (5), magnesium sulfate solution is pumped into the reactor at a flow rate of 9.482 ml / h at a temperature of 60℃, pH of 10.2, alkalinity of 5.0 g / L, and rotation speed of 280 r / min. The reaction is carried out for 10 h to allow Mg doping modification. 0.1 Ni 0.3 Fe 0.3 Mn 0.3 (OH)₂ crystal growth;

[0134] (7) Aging reaction: Mg to be processed in step (6) 0.1 Ni 0.3 Fe 0.3 Mn 0.3 After the (OH)2 crystals grow to a D50 of 4-5 μm, a 4 mol / L NaOH alkaline solution is added to the reactor at a flow rate of 50 ml / h and a rotation speed of 200 r / min. After 2 h of adding the NaOH alkaline solution, the reactor is aged for another 10 h at a rotation speed of 200 r / min and a temperature of 50-70 °C.

[0135] (8) Washing: Based on step (7), shut down the reactor and filter the solution in the reactor to obtain Mg. 0.1 Ni 0.3 Fe 0.3 Mn 0.3(OH)2 solid, filter Mg 0.1 Ni 0.3 Fe 0.3 Mn 0.3 The (OH)2 solid was washed repeatedly with deionized water 10 times until the pH value of the washing deionized water was less than 8.2 before washing was stopped.

[0136] (9) Drying: Based on step (8), Mg 0.1 Ni 0.3 Fe 0.3 Mn 0.3 (OH)₂ crystals were dried at 120℃ for 4 hours to obtain magnesium-doped modified nickel-iron-manganese-based precursor material Mg. 0.1 Ni 0.3 Fe 0.3 Mn 0.3 (OH)2.

[0137] This comparative example is based on Example 1, with modifications to the two process parameters in step (5). For example... Figure 6 As shown, the precursor material Mg prepared in Comparative Example 4 is shown. 0.1 Ni 0.3 Fe 0.3 Mn 0.3 The SEM image of (OH)2 shows that, due to the adjustment of the process sequence in the crystal growth process, the supersaturation in the reaction system first increases and then decreases, which is different from the state where the supersaturation in Example 1 is in a state of continuous decrease. As a result, nucleation occurs during the process of increasing saturation, which leads to a deterioration in the morphology of the precursor and a reduction in the overall physicochemical properties of the precursor.

[0138] The precursor materials prepared in Examples 1-3 and Comparative Examples 1-4 were used to make sodium-ion batteries and their performance was tested according to the following process:

[0139] The precursor material was mixed with sodium carbonate at a molar ratio of 1:1.02, and the mixture was sintered at 950℃. After grinding and sieving, the positive electrode material was obtained. The positive electrode material, acetylene black, and polyvinylidene fluoride (PVDF) binder were weighed at a mass ratio of 8.2:0.8:1. The PVDF powder was first dissolved in dimethyl sulfoxide (DMSO) to prepare an 8% concentration binder. Then, the positive electrode material and acetylene black were added to the binder and ground evenly. The binder was then coated onto aluminum foil and dried at 85℃ for 5 hours. The foil was then cut into 10mm diameter discs using a slicing machine and pressed using a tablet press to obtain the positive electrode sheet. Using graphite sheets as the negative electrode, PE as the separator, and 1mol / L NaPF6 as the electrolyte, a coin cell was assembled in an argon-filled glove box. After the assembled coin cells were left to stand at room temperature for 8 hours, they were tested in the range of 3.0-4.3V charge and discharge voltage. The first charge and discharge test was conducted at 0.1C and 1C rates, and the cycle performance was tested at 1C.

[0140] Table 1. Electrochemical performance test results of Examples 1-3 and Comparative Examples 1-4

[0141]

[0142] As shown in Table 1, the sodium-ion battery provided in this embodiment of the invention exhibits significant improvements in various electrochemical performance aspects compared to the sodium-ion battery provided in the comparative example. This invention, by modifying the nickel-iron-manganese-based material with magnesium doping at appropriate steps and through a suitable co-precipitation process, can significantly improve battery capacity and voltage, and enhance battery cycle performance.

[0143] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be defined by the claims.

Claims

1. A process for the preparation of a magnesium doped modified nickel-iron-manganese based precursor material, characterized in that, Includes the following steps: (1) Solution preparation: Prepare a nickel-iron-manganese-magnesium metal salt solution with a total metal ion concentration of 1-3 mol / L. Specifically, prepare a mixed salt solution by preparing soluble nickel salt, soluble iron salt, and soluble manganese salt, and prepare a soluble magnesium salt solution by preparing a soluble magnesium salt solution; prepare an ammonia complexing agent with a concentration of 2-5 mol / L; and prepare an alkaline solution with a NaOH concentration of 2-5 mol / L. (2) Preparation of reaction base solution: Add deionized water to the reaction vessel, add the prepared alkaline solution and ammonia complexing agent to the reaction vessel, adjust the alkalinity of the system to 3.0-8.0 g / L, and adjust the pH value to 10-11.5; (3) Feeding: The mixed salt solution, ammonia complexing agent and alkaline solution are fed into the reactor of step (2) under N2 atmosphere protection and at a speed of 200-400 r / min. The feed flow rate of the mixed salt solution is 5-100 ml / h, the feed flow rate of the ammonia complexing agent is 0.5-30 ml / h and the feed flow rate of the alkaline solution is 2-50 ml / h. (4) Nucleation reaction: In the reaction vessel of step (3), the solution temperature is controlled at 50-70℃, pH is 10-11.5, alkalinity is 3.0-8.0g / L, and rotation speed is 200-400r / min. The reaction is continuously fed for 0.5-2h to obtain crystal nuclei. (5) Growth reaction: In the reactor of step (4), the feed flow rate of the mixed salt solution is adjusted to 7.5-30 ml / h, the feed flow rate of the ammonia complexing agent is adjusted to 1.0-20 ml / h, and the feed flow rate of the alkaline solution is adjusted to 3-16 ml / h. The temperature of the solution in the reactor is controlled at 50-70℃, the pH is 10-10.8, the alkalinity is 3.0-8.0 g / L, and the rotation speed is 200-400 r / min. Under the conditions of continuous feeding and reaction for 2-48 hours, crystal nuclei grow; the growth reaction is carried out in two stages: Stage I: In the reactor of step (4), the flow rate of the mixed salt solution is adjusted to 8-12 ml / h, the flow rate of the alkali solution is 3-4 ml / h, the flow rate of the ammonia complexing agent is 1.0-1.2 ml / h, and the temperature of the solution in the reactor is controlled at 58-62℃, pH at 10.3-10.4, alkalinity at 4.5-5.5 g / L, and rotation speed at 280-300 r / min. Under the following conditions, the reaction proceeds for 10-15 hours; Section II: Adjust the flow rate of the mixed salt solution to 28-30 ml / h, the flow rate of the alkali solution to 7-8 ml / h, and the flow rate of the ammonia complexing agent to 1.8-2 ml / h. Control the temperature of the solution in the reactor at 58-60℃, pH at 10.2-10.3, alkalinity at 4.5-5.5 g / L, and rotation speed at 280-300 r / min, and react for 22-25 hours to allow crystal nuclei to grow; during the crystal growth reaction, the supersaturation is in a decreasing state; (6) Magnesium doping modification: While maintaining the continuous feeding in step (5), a soluble magnesium salt solution is pumped into the reactor at a flow rate of 7.5-30 ml / h, and the reaction is carried out for 8-12 hours to allow crystal growth; (7) Aging reaction: After the crystals from step (6) have grown to a D50 of 4-5 μm, add 40-200 ml of alkaline solution to the reactor with a rotation speed of 200-400 r / min at a feed flow rate of 20-60 ml / h. After the alkaline solution is added, continue aging for 8-12 h at a rotation speed of 200-400 r / min and a temperature of 50-70 °C. (8) Washing: Filter the solution in the reactor to obtain the solid filter material. Wash the solid filter material repeatedly with deionized water until the pH value of the washing deionized water is less than 8.2 to obtain the washed crystals. (9) Drying: The washed crystals are dried to obtain magnesium-doped modified nickel-iron-manganese-based precursor materials.

2. The process for preparing a magnesium-doped modified nickel-iron-manganese-based precursor material according to claim 1, characterized in that: In step (1), a nickel-iron-manganese-magnesium metal salt solution with a total metal ion concentration of 1-3 mol / L is prepared according to the molar ratio of x:y:z:1-xyz, where 0.1≤x≤0.3, 0.1≤y≤0.3, and 0.1≤z≤0.

3.

3. The preparation process of a magnesium-doped modified nickel-iron-manganese-based precursor material as described in claim 1, characterized in that: The soluble nickel salt is NiSO4·6H2O, the soluble iron salt is FeSO4·7H2O, the soluble manganese salt is MnSO4·H2O, and the soluble magnesium salt is MgSO4·7H2O.

4. The preparation process of a magnesium-doped modified nickel-iron-manganese-based precursor material as described in claim 1, characterized in that: In step (1), the ammonia complexing agent is a mixed solution formed by dissolving ammonia in water, with a molar concentration of 4 mol / L.

5. The preparation process of a magnesium-doped modified nickel-iron-manganese-based precursor material as described in claim 1, characterized in that: In step (2), deionized water is introduced into the reaction vessel, and then a reducing agent of 1-3‰ of the total mass of soluble nickel salt, soluble iron salt, soluble manganese salt and soluble magnesium salt is added. The reducing agent is one of ascorbic acid, sodium ascorbate and hydrazine hydrate. The prepared alkaline solution and ammonia complexing agent are added to the reaction base liquid to adjust the alkalinity of the system to 3.0-8.0 g / L and the pH value to 10-11.

5.

6. The preparation process of a magnesium-doped modified nickel-iron-manganese-based precursor material as described in claim 1, characterized in that: In step (2), deionized water is introduced into the reactor, and then 1-5‰ of the total mass of soluble nickel salt, soluble iron salt, soluble manganese salt and soluble magnesium salt PVP is added. Finally, the prepared alkaline solution and ammonia complexing agent are added to the reaction base liquid to adjust the alkalinity of the system to 3.0-8.0 g / L and the pH value to 10-11.

5.

7. The preparation process of a magnesium-doped modified nickel-iron-manganese-based precursor material as described in claim 1, characterized in that: In step (9), the drying temperature is 100-130℃ and the drying time is 4-6h.

8. Magnesium-doped modified nickel-iron-manganese-based precursor material prepared by the preparation process described in any one of claims 1 to 7.

9. A positive electrode material for a sodium-ion battery, characterized in that: The cathode material is made by combining the magnesium-doped modified nickel-iron-manganese-based precursor material as described in claim 8 with a sodium-containing material.

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