CN116903053A - Preparation process of magnesium doped modified nickel-iron-manganese based precursor material - Google Patents

Abstract

The invention discloses a preparation process of a magnesium doped modified nickel-iron-manganese based precursor material, and belongs to the field of electrode material preparation. The invention comprises the following steps: (1) preparing a solution; (2) preparing a reaction base solution; (3) feeding; (4) nucleation; (5) a growth reaction; (6) magnesium doping modification; (7) aging reaction; (8) washing; and (9) drying. According to the invention, the magnesium modified doped nickel-iron-manganese based material is utilized, an intermittent process is adopted to prepare the sodium-electricity precursor, the structure and the morphology of the crystal are accurately regulated and controlled by controlling the solid content, the flow rate, the pH value and other factors of the reactant, and meanwhile, the particle size distribution of the precursor can be well regulated, so that the sodium-electricity precursor material with single particle size is prepared.

Description

Preparation process of magnesium-doped modified nickel-iron-manganese-based precursor material

Technical field

The invention relates to the field of electrode materials, and specifically relates to a preparation process of magnesium-doped modified nickel-iron-manganese-based precursor material.

Background technique

In the context of the "double carbon" era, how to develop new energy materials that are both clean and cheap is the direction of today's development. At present, lithium-ion batteries are the most technologically mature and widely used new energy materials. However, the high price of lithium-ion batteries and the extreme shortage of lithium resources are the most serious problems restricting the development of lithium-ion batteries. In order to solve the above problems of lithium-ion batteries, sodium-ion batteries were born. Sodium-ion batteries are currently the most promising new energy technology. There are many types of sodium-ion batteries, among which layered oxide cathode materials are the main direction of current research. Layered oxide cathode materials are divided into P2 type and O3 type.

At present, methods for preparing sodium electron precursor materials include co-precipitation method, high-temperature solid phase method, sol-gel method, spray drying method, hydrothermal/solvent method, microwave synthesis method, etc. Among them, the co-precipitation method has mature equipment, It is widely used due to its advantages such as easy industrialization. However, in the co-precipitation method, since the Ksp constants of Ni(OH) ₂ , Fe(OH) ₂ , and Mn(OH) ₂ are not of the same order of magnitude, how to achieve co-precipitation is a technical difficulty in this method. This technology The existence of difficulties will lead to the problem that the morphology and particle size distribution of the precursor cannot be well controlled. The morphology deviation and the particle size are partially wide, which will lead to low compaction of the precursor, further reducing the compaction density of the cathode material, thus affecting the electrochemical performance of the battery material.

In addition, in the current process of preparing 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, with As the reaction time prolongs, the viscosity of the slurry system becomes larger and larger, causing the particle size distribution of the precursor to broaden and affecting the overall performance of the product.

At present, researchers have also done relevant research on the preparation of precursors for sodium-ion battery cathode materials. For example, the patent application with publication number CN115924980A discloses a preparation method for a composite phosphate-based iron-based sodium-ion battery layered cathode material precursor. , on the one hand, this preparation method has too many additives, which makes subsequent wastewater treatment more difficult, thereby increasing the cost; on the other hand, the battery capacity of this preparation method is low. For example, the patent application with publication number CN115818737A discloses a nickel-iron-manganese ternary precursor and its preparation method and application. The primary particles of the precursor prepared by this patent are in the shape of flakes, and the secondary particles have poor sphericity, resulting in The tapping of the precursor is low, which affects the electrochemical performance of the cathode material. For example, the patent application with publication number CN 115594233A discloses a quaternary cathode material precursor for sodium ion batteries, its preparation method and application. The patent preparation method uses nickel, iron, manganese and magnesium mixed salts to enter the reactor in parallel flow at the same time for reaction. Due to four The precipitation constants of elements vary greatly, making it difficult to co-precipitate, which makes it difficult to control the morphology and particle size distribution of the precursor, ultimately affecting the physical and chemical properties of the precursor.

Contents of the invention

The purpose of the present invention is to solve the above-mentioned problems existing in the prior art and provide a preparation process for magnesium-doped modified nickel-iron-manganese-based precursor materials. The present invention adopts the basis of adding antioxidants and complexing agents to the reaction bottom liquid. On the surface, nickel, iron, and manganese are used to first carry out nucleation and growth reactions to generate crystal nuclei, and then magnesium salts are introduced to deposit and grow on the surface of the crystal nuclei. This prevents the four elements of nickel, iron, manganese, and magnesium from being difficult to co-precipitate. , On the other hand, the morphology and particle size distribution of the precursor are controllable, and the process has good stability.

The present invention uses magnesium modified doped nickel iron manganese-based materials, adopts a batch process to prepare sodium electricity precursor, and precisely controls the structure and morphology of the crystal by controlling the solid content, flow rate, pH value and other factors of the reactants. At the same time, the particle size distribution of the precursor can be well adjusted, thereby preparing sodium electron precursor materials with a single particle size.

In order to achieve the above objects, the technical solutions of the present invention are as follows:

A preparation process for magnesium-doped modified nickel-iron-manganese-based precursor material, including 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 from soluble nickel salt, soluble iron salt, and soluble manganese salt, and mix soluble magnesium The salt is prepared into a soluble magnesium salt solution; an ammonia water complexing agent with a concentration of 2-5 mol/L is prepared; an alkali solution with a NaOH concentration of 2-5 mol/L is prepared;

(2) Preparation of the reaction bottom liquid: Add deionized water to the reaction kettle, add the prepared alkali solution and ammonia complexing agent to the reaction kettle, and adjust the alkalinity of the system to 3.0-8.0g/L, pH Adjust the value to 10-11.5;

(3) Feed: Flow the mixed salt solution, ammonia complexing agent, and alkali solution into the reaction kettle of step (2) under the protection of _N2 atmosphere and with a rotation speed of 200-400r/min, in which the mixed salt solution is fed The feed flow rate is 5-100ml/h, the feed flow rate of ammonia complexing agent is 0.5-30ml/h, and the feed flow rate of alkali solution is 2-50ml/h;

(4) Nucleation reaction: In the reaction kettle of step (3), control the temperature of the solution at 50-70°C, pH at 10-11.5, alkalinity at 3.0-8.0g/L, and rotation speed at 200-400r/min. The conditions continue to feed the reaction for 0.5-2h to obtain crystal nuclei;

(5) Growth reaction: In the reaction kettle of step (4), adjust the feed flow rate of the mixed salt solution to 7.5-30ml/h, the feed flow rate of the ammonia water complexing agent to 1.0-20ml/h, and the alkali solution The feed flow rate is adjusted to 3-16ml/h, and the temperature of the solution in the reaction kettle is controlled to be 50-70°C, the pH is 10-10.8, the alkalinity is 3.0-8.0g/L, and the rotation speed is 200-400r/min. Continuously feed the reaction for 2-48h to make the crystal nuclei grow;

(6) Magnesium doping modification: Keep the conditions of step (5) and continue to feed, while pumping the soluble magnesium salt solution into the reaction kettle at a flow rate of 7.5-30ml/h, and react for 8-12h to grow the crystal;

(7) Aging reaction: After the crystals in step (6) grow to D50 of 4-5um, add 40-200ml alkali solution to the reaction kettle with a rotation speed of 200-400r/min at a feed flow rate of 20-60ml/h. , after the addition of the alkali solution is completed, continue aging for 8-12 hours at a rotation speed of 200-400r/min and a temperature of 50-70°C;

(8) Washing: Filter the solution in the reaction kettle to obtain the filtered solid, and repeatedly wash the filtered solid with deionized water until the pH value of the washed deionized water is less than 8.2 to obtain washed crystals;

(9) Drying: Dry the washed crystals to obtain a magnesium-doped modified nickel-iron-manganese-based precursor material.

Further, in step (1), prepare a nickel-iron-manganese-magnesium metal salt solution with a total metal ion concentration of 1-3 mol/L according to the molar ratio of x:y:z:1-x-y-z, where 0.1≤x≤0.3, 0.1 ≤y≤0.3, 0.1≤z≤0.3.

Further, in step (1), the soluble nickel salt is NiSO ₄ ·6H ₂ O, and the purity is industrial grade (nickel content is 22.2%); the soluble iron salt is FeSO ₄ ·7H ₂ O (the iron content is 22.2%). 17%), the purity is industrial grade; the soluble manganese salt is MnSO ₄ ·H ₂ O, the purity is industrial grade (manganese content is 32%); the soluble magnesium salt is MgSO ₄ ·7H ₂ O, the purity is industrial grade grade (MgSO ₄ ·7H ₂ O content 93%).

Further, in step (1), the ammonia complexing agent is a mixed solution of ammonia dissolved in water, and the molar concentration is 4 mol/L.

Further, in step (2), deionized water is passed into the reaction kettle, and 1-3‰ of the total mass of soluble nickel salt, soluble iron salt, soluble manganese salt, and soluble magnesium salt is added as a reducing agent. The agent is one of ascorbic acid, sodium ascorbate, and hydrazine hydrate. Add the prepared alkali solution and ammonia complexing agent to the reaction bottom solution, and adjust the alkalinity of the system to 3.0-8.0g/L, and the pH value is 10 -11.5.

Further, in step (2), deionized water is poured into the reaction kettle, and then 1-5‰ of PVP based on the total mass of soluble nickel salt, soluble iron salt, soluble manganese salt, and soluble magnesium salt is added, and finally the prepared The alkali solution and ammonia complexing agent are added to the reaction bottom solution, and the alkalinity of the system is adjusted to 3.0-8.0g/L, and the pH value is 10-11.5.

Further, in step (9), the drying temperature is 100-130°C, and the drying time is 4-6 hours.

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

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.

The invention also provides a cathode material for a sodium-ion battery, which is made of a composite of the magnesium-doped modified nickel-iron-manganese-based precursor material and a sodium-containing material.

The beneficial effects of the present invention are as follows:

In the co-precipitation method for preparing sodium electron precursor materials, since the Ksp constants of Ni(OH) ₂ , Fe(OH) ₂ , and Mn(OH) ₂ are not on the same order of magnitude, how to achieve co-precipitation is a problem of this method. The technical difficulty is that the present invention adds a certain concentration of complexing agent ammonia water to cause Ni ²⁺ , Fe ²⁺ , and Mn ²⁺ to undergo a complex reaction first, and then a precipitation reaction. In this way, coprecipitation occurs by controlling the chemical reaction rate. , the morphology and particle size distribution of the precursor can be well controlled.

In the present invention, while adding reducing agent and dispersing agent PVP to the reaction bottom liquid, magnesium is used to modify and dope nickel-iron-manganese-based materials, and a batch process is used to prepare the sodium electricity precursor. By controlling the solid content and flow rate of the reactants, , pH value and other factors to accurately control the structure and morphology of the crystal, and at the same time, it can well adjust the particle size distribution of the precursor, thereby preparing sodium electron precursor materials with a single particle size.

In the present invention, a certain amount of reducing agent (ascorbic acid, sodium ascorbate, hydrazine hydrate, etc.) is added to the base liquid to prevent the oxidation of ferrous ions and thereby control the crystal form and morphology of the precursor.

As the reaction time prolongs, the viscosity of the slurry system increases. The present invention reduces the surface tension of the slurry system by adding PVP (polyvinylpyrrolidone) to the reaction bottom liquid, thereby strengthening the dispersion of the slurry system, so that Mg _1-xyz Ni _x Fe _y Mn _z (OH) ₂ precursor particle size distribution is controllable.

The present invention modifies nickel-iron-manganese-based materials through magnesium doping, thereby increasing battery capacity and voltage and enhancing battery cycle performance.

Compared with the continuous preparation method, the batch preparation method of the present invention can reduce the amount of solvent used in the reaction, thereby greatly reducing the amount of sewage treatment, thereby saving a lot of costs.

Description of the drawings

Figure 1 is an enlarged view of the Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal nucleus prepared in Example 1 of the present invention;

Figure 2 is an SEM image of the precursor material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ prepared in Example 1 of the present invention;

Figure 3 is a particle size distribution diagram of the precursor material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ prepared in Example 1 of the present invention;

Figure 4 is an SEM image of the precursor material Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ prepared in Comparative Example 1 of the present invention;

Figure 5 is an SEM image of the precursor material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ prepared in Comparative Example 2 of the present invention;

Figure 6 is an SEM image of the precursor material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ prepared in Comparative Example 3 of the present invention;

Figure 7 is an SEM image of the precursor material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ prepared in Comparative Example 4 of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the present 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 here are only used to explain the present invention and are not intended to limit the present invention.

A preparation process for magnesium-doped modified nickel-iron-manganese-based precursor material, including the following steps:

(1) Preparation of solution:

Prepare a nickel-iron-manganese-magnesium metal salt solution with a total metal ion concentration of 1-3 mol/L according to the molar ratio of x:y:z:1-xyz. The 0.1≤x≤0.3, 0.1≤y≤0.3, 0.1≤ z≤0.3; Specifically, soluble nickel salt, soluble iron salt, and soluble manganese salt are prepared into a mixed salt solution, and the soluble magnesium salt is prepared into a soluble magnesium salt solution; the soluble nickel salt is nickel sulfate NiSO ₄ ·6H ₂ O, The purity is industrial grade (nickel content is 22.2%); the soluble iron salt is ferrous sulfate FeSO ₄ ·7H ₂ O (iron content is 17%), and the purity is industrial grade; the soluble manganese salt is manganese sulfate MnSO ₄ ·H ₂ O, the purity is industrial grade (manganese content is 32%); the soluble magnesium salt is magnesium sulfate MgSO ₄ ·7H ₂ O, the purity is industrial grade (MgSO ₄ ·7H ₂ O content is 93%); the details are as follows The sulfate used in the examples is the same as above;

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

Dissolve NaOH in water to form a mixed aqueous solution to prepare an alkali solution with a NaOH concentration of 2-5 mol/L.

(2) Preparation of the reaction bottom liquid: Pour a certain quality of deionized water into a 2-5L reaction kettle, and add soluble salts (i.e. soluble nickel salt, soluble iron salt, soluble manganese salt, soluble magnesium salt) into the reaction kettle (the sum of) 1-3‰ of the total mass of reducing agents (such as one of ascorbic acid, sodium ascorbate, and hydrazine hydrate), on this basis, add soluble salts (i.e., soluble nickel salts, soluble iron salts, soluble manganese salts, soluble The sum of the magnesium salts) is 1-5‰ of the total mass of PVP (polyvinylpyrrolidone). Finally, add the prepared alkali solution and ammonia complexing agent solution to the reaction bottom solution, and adjust the alkalinity of the system to 3.0-8.0 g/L, pH value is 10-11.5.

(3) Feed: The mixed salt solution, ammonia complexing agent solution, and alkali solution prepared in step (1) are flowed together into the reaction of step (2) under the protection of _N2 atmosphere and the rotation speed is 200-400r/min. In the kettle, the feed flow rate of the mixed salt solution is 5-100ml/h, the feed flow rate of the ammonia complexing agent solution is 0.5-30ml/h, and the feed flow rate of the alkali solution is 2-50ml/h.

(4) Nucleation reaction: In the reaction kettle of step (3), control the temperature of the solution at 50-70°C, pH at 10-11.5, alkalinity at 3.0-8.0g/L, and rotation speed at 200-400r/min. The feed reaction was continued for 0.5-2h to obtain _Nix Fe _y Mn _z (OH) ₂ crystal nuclei.

(5) Growth reaction: In the reaction kettle of step (4), adjust the feed flow rate of the mixed salt solution to 7.5-30ml/h, the feed flow rate of the ammonia complexing agent solution to 1.0-20ml/h, and the feed flow rate of the alkali solution. Adjust the flow rate to 3-16ml/h, and control the temperature of the solution in the reactor to be 50-70°C, pH 10-10.8, alkalinity 3.0-8.0g/L, and rotation speed 200-400r/min. The material reacts for 2-48h to grow _Nix Fe _y Mn _z (OH) ₂ crystal nuclei.

(6) Magnesium doping modification: In the reaction kettle of step (5), while reacting according to the feeding conditions of step (5), pump the soluble magnesium salt solution at a flow rate of 7.5-30ml/h to a temperature of 50 In a reaction kettle at -70°C, pH 10-10.8, alkalinity 3.0-8.0g/L, and rotation speed 200-400r/min, react for 8-12h to make Mg _1-xyz Ni _x Fe _y Mn _z (OH ) ₂ Crystal growth.

(7) Aging reaction: After the Mg _1-xyz Ni _x Fe _y Mn _z (OH) ₂ crystals in step (6) grow to D50 at 4-5um, lower the speed to 200 at a flow rate of 20-60ml/h. Add 40-200ml NaOH alkali solution with a concentration of 2-5mol/L into the reaction kettle at -400r/min. After the addition of the alkali solution is completed, continue at a speed of 200-400r/min and a temperature of 50-70°C. Aging 8-12h.

(8) Washing: On the basis of step (7), shut down the reaction kettle, filter the solution in the reaction kettle, and obtain the filtered material Mg _1-xyz Ni _x Fe _y Mn _z (OH) ₂ solid, and filter the filtered material Mg _1-xyz Ni _x Fe _y Mn _z (OH) ₂ solids are washed repeatedly with deionized water 5-10 times until the pH value of the washed deionized water is less than 8.2 before washing is stopped.

(9) Drying: On the basis of step (8), dry the Mg _1-xyz Ni _x Fe _y Mn _z (OH) ₂ crystal at a drying temperature of 100-130°C and a drying time of 4-6h to obtain magnesium-doped Heteromodified nickel-iron-manganese-based precursor material Mg _1-xyz Ni _x Fe _y Mn _z (OH) ₂ .

Example 1

A preparation process for magnesium-doped modified nickel-iron-manganese-based precursor material, including the following steps:

(1) Solution preparation: Prepare magnesium sulfate, nickel sulfate, ferrous sulfate and manganese sulfate in a molar ratio of 0.1:0.3:0.3:0.3 to prepare a nickel-iron-manganese solution with a total metal ion concentration of 2mol/L and a volume of 0.5L. Mix the salt solution and 0.5L magnesium sulfate solution (for later use) to prepare a 4mol/L ammonia complexing agent solution and a 4mol/L NaOH alkali solution.

(2) Preparation of reaction bottom liquid: Pour a certain mass of deionized water into a 3L reaction kettle, add 0.461g of reducing agent ascorbic acid to the reaction kettle, and then add 0.69g of PVP on this basis, and finally add the prepared NaOH alkali solution and ammonia complexing agent solution were added to the reaction bottom solution, and the alkalinity of the system was adjusted to 5.0g/L, and the pH value was 11.2;

(3) Feeding: The nickel-iron-manganese mixed salt solution prepared in step (1) has a feeding flow rate of 6.7ml/h, the ammonia complexing agent solution has a feeding flow rate of 0.7mL/h, and the NaOH alkali solution has a feeding flow rate of 0.7ml/h. The feed flow rate is 2.7ml/h and added to the reaction kettle of step (2) under the protection of _N2 atmosphere and the rotation speed is 300r/min;

(4) Nucleation reaction: In the reaction kettle of step (3), control the temperature of the solution in the reaction kettle at 60°C, pH 11.2, alkalinity 5.0g/L, and rotation speed 300r/min according to steps ( Continue the feeding reaction under the feeding conditions of 3) for 2 hours to obtain Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal nuclei;

(5) Growth reaction: A two-stage process is used to carry out the Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal nucleus growth reaction. The reaction in Section I is carried out first and then the reaction in Section II is carried out; Section I: In the reaction kettle of step (4), adjust The flow rate of the nickel-iron-manganese mixed salt solution is 10ml/h, the flow rate of the NaOH alkali solution is 4ml/h, and the flow rate of the ammonia complexing agent solution is 1.2ml/h. The temperature of the solution in the reaction kettle is controlled at 60°C, the pH is 10.32, and the alkalinity React for 12 hours at a speed of 5.0g/L and a rotation speed of 290r/min; section II: adjust the flow rate of the nickel-iron-manganese mixed salt solution to 30ml/h, the flow rate of the NaOH alkali solution to 8ml/h, and the flow rate of the ammonia complexing agent solution to 2ml /h, control the temperature of the solution in the reactor to react for 24 hours at 60°C, pH 10.20, alkalinity 5.0g/L, and rotation speed 280r/min to nucleate Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ grow;

(6) Mg doping modification: In the reaction kettle of step (5), while reacting according to the feed conditions of section II, pump the magnesium sulfate solution at a flow rate of 9.48ml/h to a temperature of 60°C and a pH of 10.2 , in a reactor with an alkalinity of 5.0g/L and a rotation speed of 280r/min, react for 10 hours to grow Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystals;

(7) Aging reaction: After the Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal in step (6) has grown to D50 at 4-5um, add it to the reaction kettle with a flow rate of 50ml/h and a rotation speed of 200r/min. Add 4 mol/L NaOH alkali solution. After adding the NaOH alkali solution for 2 hours, continue aging for 10 hours at a rotation speed of 200 r/min and a temperature of 50-70°C;

(8) Washing: On the basis of step (7), shut down the reaction kettle, filter the solution in the reaction kettle, and obtain the filtrate Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ solid. Mg _0.1 Ni _0.3 Fe _{The 0.3} Mn _0.3 (OH) ₂ solid is washed repeatedly with deionized water 10 times until the pH value of the washed deionized water is less than 8.2. The washing can be stopped to obtain Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal;

(9) Drying: On the basis of step (8), dry the Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal at a drying temperature of 120°C and a drying time of 4 hours to obtain magnesium-doped modified nickel-iron-manganese. Base precursor material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ .

As shown in Figure 1, it is an enlarged view of the Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal nucleus prepared in Example 1. It can be seen from the figure that the distribution of crystal nuclei is obvious and there is no agglomeration phenomenon;

As shown in Figure 2, it is an SEM image of the precursor material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ prepared in Example 1. It can be seen from the figure that the primary particles of the precursor are thick sheets and the secondary particles are spherical. Good strength, no twins or segregation;

As shown in Figure 3, it is a particle size distribution diagram of the precursor material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ prepared in Example 1. It can be seen from the figure that the particle size distribution is controllable.

Example 2

A preparation process for magnesium-doped modified nickel-iron-manganese-based precursor material, including the following steps:

(1) Solution preparation: Prepare magnesium sulfate, nickel sulfate, ferrous sulfate and manganese sulfate in a molar ratio of 0.15:0.3:0.25:0.3 to prepare a nickel-iron-manganese solution with a total metal ion concentration of 2mol/L and a volume of 0.5L. Mix the salt solution and a magnesium sulfate solution with a volume of 0.5 L (for later use) to prepare a 4 mol/L ammonia complexing agent solution and a 4 mol/L NaOH alkali solution.

(2) Preparation of reaction bottom liquid: Pour a certain mass of deionized water into a 3L reaction kettle, add 0.44g of the reducing agent sodium ascorbate to the reaction kettle, and then add 0.65g of PVP on this basis. Finally, the prepared The NaOH alkali solution and ammonia complexing agent solution were added to the reaction bottom solution, and the alkalinity of the system was adjusted to 5.0g/L, and the pH value was 11.2;

(3) Feeding: Add the nickel-iron-manganese mixed salt solution prepared in step (1) with a feeding flow rate of 6.7ml/h, the ammonia complexing agent solution with a feeding flow rate of 0.69mL/h, and the NaOH alkali solution with a feeding flow rate of 6.7ml/h. The feed flow rate is 2.68ml/h and added to the reaction kettle of step (2) under the protection of _N2 atmosphere and the rotation speed is 300r/min;

(4) Nucleation reaction: In the reaction kettle of step (3), control the temperature of the solution in the reaction kettle to react for 2 hours under the conditions of 60°C, pH 11.2, alkalinity 5.0g/L, and rotation speed 300r/min. Ni _0.3 Fe _0.25 Mn _0.3 (OH) ₂ crystal nuclei are obtained;

(5) Growth reaction: Use a two-stage process to carry out the Ni _0.3 Fe _0.25 Mn _0.3 (OH) ₂ crystal nucleus growth reaction; proceed to section I first: in the reaction kettle of step (4), adjust the flow rate of the nickel iron and manganese mixed salt solution to 10 ml /h, the flow rate of NaOH alkali solution is 3.9ml/h, the flow rate of ammonia complexing agent solution is 1.1ml/h, the temperature of the solution is controlled at 60°C, the pH is 10.32, the alkalinity is 5.0g/L, and the rotation speed is 290r/min. React for 12 hours under the conditions; then proceed to section II: adjust the flow rate of the nickel-iron-manganese mixed salt solution to 30ml/h, the flow rate of the NaOH alkali solution to 7.8ml/h, the flow rate of the ammonia complexing agent solution to 1.9ml/h, and control the temperature of the solution React for 24 hours at 60°C, pH 10.20, alkalinity 5.0g/L, and rotation speed 280r/min to grow Ni _0.3 Fe _0.25 Mn _0.3 (OH) ₂ crystal nuclei;

(6) Mg doping modification: In the reaction kettle of step (5), while reacting according to the feeding conditions of section II, pump the magnesium sulfate solution at a flow rate of 15.06ml/h to a temperature of 60°C and a pH of 10.2 , in a reactor with an alkalinity of 5.0g/L and a rotation speed of 280r/min, react for 10 hours to grow Mg _0.15 Ni _0.3 Fe _0.25 Mn _0.3 (OH) ₂ crystals;

(7) Aging reaction: After the Mg _0.15 Ni _0.3 Fe _0.25 Mn _0.3 (OH) ₂ crystal in step (6) grows to D50 at 4-5um, it is poured into the reaction kettle with a flow rate of 50ml/h and a rotation speed of 200r/min. Add 4 mol/L NaOH alkali solution. After adding the NaOH alkali solution for 2 hours, continue aging for 10 hours at a rotation speed of 200 r/min and a temperature of 50-70°C;

(8) Washing: On the basis of step (7), shut down the reaction kettle, filter the solution in the reaction kettle, and obtain the filtered material Mg _0.15 Ni _0.3 Fe _0.25 Mn _0.3 (OH) ₂ solid. The filtered material Mg _0.15 Wash the Ni _0.3 Fe _0.25 Mn _0.3 (OH) ₂ solid with deionized water repeatedly for 10 times until the pH value of the washed deionized water is less than 8.2 before stopping the washing;

(9) Drying: On the basis of step (8), dry the Mg _0.15 Ni _0.3 Fe _0.25 Mn _0.3 (OH) ₂ crystal at a drying temperature of 120°C and a drying time of 4 hours to obtain magnesium-doped modified nickel iron manganese. Base precursor material Mg _0.15 Ni _0.3 Fe _0.25 Mn _0.3 (OH) ₂ .

Example 3

A preparation process for magnesium-doped modified nickel-iron-manganese-based precursor material, including the following steps:

(1) Solution preparation: Prepare magnesium sulfate, nickel sulfate, ferrous sulfate and manganese sulfate in a molar ratio of 0.2:0.3:0.2:0.3 to prepare a nickel-iron-manganese solution with a total metal ion concentration of 2mol/L and a volume of 0.5L. Mix the salt solution and a magnesium sulfate solution with a volume of 0.5 L (for later use) to prepare a 4 mol/L ammonia complexing agent solution and a 4 mol/L NaOH alkali solution.

(2) Preparation of reaction bottom liquid: Pour a certain mass of deionized water into a 3L reaction kettle, add 0.423g of the reducing agent hydrazine hydrate to the reaction kettle, and then add 0.62g of PVP on this basis. Finally, the mixture will be prepared. The NaOH alkali solution and ammonia complexing agent solution were added to the reaction bottom solution, and the alkalinity of the system was adjusted to 5.0g/L, and the pH value was 11.2;

(3) Feeding: The nickel-iron-manganese mixed salt solution prepared in step (1) has a feeding flow rate of 6.7ml/h, the ammonia complexing agent solution has a feeding flow rate of 0.64mL/h, and the NaOH alkali solution has a feeding flow rate of 0.64mL/h. The feed flow rate is 2.67ml/h and added to the reaction kettle of step (2) under the protection of _N2 atmosphere and the rotation speed is 300r/min;

(4) Nucleation reaction: In the reaction kettle of step (3), control the temperature of the solution to react for 2 hours at 60°C, pH 11.2, alkalinity 5.0g/L, and rotation speed 300r/min to obtain Ni _0.3 Fe _0.2 Mn _0.3 (OH) ₂ crystal nucleus;

(5) Growth reaction: A two-stage process is used to carry out the Ni _0.3 Fe _0.2 Mn _0.3 (OH) ₂ crystal nucleus growth reaction; Section I: In the reaction kettle of step (4), adjust the flow rate of the nickel iron and manganese mixed salt solution to 10 ml/h , the flow rate of NaOH alkali solution is 3.8ml/h, the flow rate of ammonia complexing agent solution is 1ml/h, the temperature of the solution is controlled at 60°C, pH is 10.32, alkalinity is 5.0g/L, and the rotation speed is 290r/min. Reaction 12h; Section II: Adjust the flow rate of the nickel-iron-manganese mixed salt solution to 30ml/h, the flow rate of the NaOH alkali solution to 7.6ml/h, the flow rate of the ammonia complexing agent solution to 1.8ml/h, and control the temperature and pH of the solution at 60°C. React for 24 hours under the conditions of 10.20, alkalinity 5.0g/L, and rotation speed 280r/min to grow Ni _0.3 Fe _0.2 Mn _0.3 (OH) ₂ crystal nuclei;

(6) Mg doping modification: In the reaction kettle of step (5), while feeding and reacting according to section II, pump the magnesium sulfate solution at a flow rate of 21.34ml/h to a temperature of 60°C and a pH of 10.2. In a reaction kettle with an alkalinity of 5.0g/L and a rotation speed of 280r/min, react for 10 hours to grow Mg _0.15 Ni _0.3 Fe _0.25 Mn _0.3 (OH) ₂ crystals;

(7) Aging reaction: After growing the Mg _0.2 Ni _0.3 Fe _0.2 Mn _0.3 (OH) ₂ crystal in step (6) to D50 at 4-5um, move it into a reaction kettle with a flow rate of 50ml/h and a rotation speed of 200r/min. Add 4 mol/L NaOH alkali solution into the solution. After adding the NaOH alkali solution for 2 hours, continue aging for 10 hours at a rotation speed of 200 r/min and a temperature of 50-70°C;

(8) Washing: On the basis of step (7), shut down the reaction kettle, filter the solution in the reaction kettle, and obtain the filtered material Mg _0.2 Ni _0.3 Fe _0.2 Mn _0.3 (OH) ₂ solid. The filtered material Mg _0.2 Wash the Ni _0.3 Fe _0.2 Mn _0.3 (OH) ₂ solid with deionized water repeatedly for 10 times until the pH value of the washed deionized water is less than 8.2 before stopping the washing;

(9) Drying: On the basis of step (8), dry the Mg _0.2 Ni _0.3 Fe _0.2 Mn _0.3 (OH) ₂ crystal at a drying temperature of 120°C and a drying time of 4 hours to obtain magnesium-doped modified nickel-iron-manganese. The base precursor material is Mg _0.2 Ni _0.3 Fe _0.2 Mn _0.3 (OH) ₂ .

Comparative example 1

A preparation process of nickel-iron-manganese-based precursor material, including the following steps:

(1) Solution preparation: Use nickel sulfate, ferrous sulfate and manganese sulfate in a molar ratio of 0.3:0.3:0.3 to prepare a nickel-iron-manganese mixed salt solution with a total metal ion concentration of 2mol/L and a volume of 1L (for backup) , prepare a 4mol/L ammonia complexing agent solution and a 4mol/L NaOH alkali solution.

(2) Preparation of reaction bottom liquid: Pour a certain mass of deionized water into a 3L reaction kettle, add 0.461g of reducing agent ascorbic acid to the reaction kettle, and then add 0.69g of PVP on this basis, and finally add the prepared NaOH alkali solution and ammonia complexing agent solution were added to the reaction bottom solution, and the alkalinity of the system was adjusted to 5.0g/L, and the pH value was 11.2;

(3) Feeding: The nickel-iron-manganese mixed salt solution prepared in step (1) has a feeding flow rate of 6.7ml/h, the ammonia complexing agent solution has a feeding flow rate of 0.7mL/h, and the NaOH alkali solution has a feeding flow rate of 0.7ml/h. The feed flow rate is 2.7ml/h and added to the reaction kettle of step (2) under the protection of _N2 atmosphere and the rotation speed is 300r/min;

(4) Nucleation reaction: In the reaction kettle of step (3), control the temperature of the solution in the reaction kettle at 60°C, pH 11.2, alkalinity 5.0g/L, and rotation speed 300r/min according to steps ( Continue the feeding reaction under the feeding conditions of 3) for 2 hours to obtain Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal nuclei;

(5) Growth reaction: Use a two-stage process to carry out the Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal nucleus growth reaction, first perform section I and then proceed to section II; section I: In the reaction kettle of step (4), adjust the nickel iron The flow rate of the manganese mixed salt solution is 10ml/h, the flow rate of the NaOH alkali solution is 4ml/h, and the flow rate of the ammonia complexing agent solution is 1.2ml/h. The temperature of the solution in the reaction kettle is controlled to be 60°C, the pH is 10.32, and the alkalinity is 5.0 g/L and a rotating speed of 290r/min for 12 hours; section II: adjust the flow rate of the nickel-iron-manganese mixed salt solution to 30ml/h, the flow rate of the NaOH alkali solution to 8ml/h, and the flow rate of the ammonia complexing agent solution to 2ml/h. , control the temperature of the solution in the reaction kettle to react for 24 hours under the conditions of 60°C, pH 10.20, alkalinity 5.0g/L, and rotation speed 280r/min, so that Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal nuclei grow;

(6) Aging reaction: After the Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal in step (5) grows to D50 at 4-5um, add 4 mol to the reaction kettle with a rotation speed of 200r/min at a flow rate of 50ml/h. /L NaOH alkali solution, after adding the NaOH alkali solution for 2 hours, continue aging for 10 hours at a rotation speed of 200 r/min and a temperature of 50-70°C;

(7) Washing: On the basis of step (6), shut down the reaction kettle, filter the solution in the reaction kettle, and obtain the filtered product Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ solid. The filtered product Ni _0.3 Fe _0.3 Wash the Mn _0.3 (OH) ₂ solid with deionized water repeatedly for 10 times until the pH value of the washed deionized water is less than 8.2 before stopping the washing;

(8) Drying: On the basis of step (7), dry the Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal at a drying temperature of 120°C and a drying time of 4 hours to obtain the nickel iron manganese-based precursor material Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ .

This comparative example is based on Example 1 without adding magnesium. As shown in Figure 4, it is an SEM image of the precursor material Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ prepared in Comparative Example 1. It can be seen from the figure that due to the absence of magnesium doping, the magnesium points in the crystal structure are The replacement of nickel-iron-manganese causes the primary particles to become thinner and the crystal orientation to become disordered, causing the morphology of the precursor to deteriorate and the vibration strength to be low.

Comparative example 2

A preparation process for magnesium-doped modified nickel-iron-manganese-based precursor material, including the following steps:

(1) Solution preparation: Prepare magnesium sulfate, nickel sulfate, ferrous sulfate and manganese sulfate in a molar ratio of 0.1:0.3:0.3:0.3 to prepare magnesium, nickel, iron and manganese with a total metal ion concentration of 2mol/L and a volume of 1L. Mix the salt solution (for later use) to prepare a 4mol/L ammonia complexing agent solution and a 4mol/L NaOH alkali solution.

(2) Preparation of reaction bottom liquid: Pour a certain mass of deionized water into a 3L reaction kettle, add 0.461g of reducing agent ascorbic acid to the reaction kettle, and then add 0.69g of PVP on this basis, and finally add the prepared NaOH alkali solution and ammonia complexing agent solution were added to the reaction bottom solution, and the alkalinity of the system was adjusted to 5.0g/L, and the pH value was 11.2;

(3) Feeding: Mix the magnesium, nickel, iron and manganese mixed salt solution prepared in step (1) with a feeding flow rate of 6.7ml/h, the ammonia complexing agent solution with a feeding flow rate of 0.7mL/h, and the NaOH alkali solution. Add it to the reaction kettle of step (2) under _N2 atmosphere protection with a feed flow rate of 2.7ml/h and a rotation speed of 300r/min;

(4) Nucleation reaction: In the reaction kettle of step (3), control the temperature of the solution in the reaction kettle at 60°C, pH 11.2, alkalinity 5.0g/L, and rotation speed 300r/min according to steps ( 3) Continue the feeding reaction for 2 hours under the feeding conditions to obtain Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal nuclei;

(5) Growth reaction: Use a two-stage process to carry out the Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal nucleus growth reaction, first perform section I and then proceed to section II; section I: In the reaction kettle of step (4), adjust The flow rate of the magnesium, nickel, iron and manganese mixed salt solution is 10ml/h, the flow rate of the NaOH alkali solution is 4ml/h, the flow rate of the ammonia complexing agent solution is 1.2ml/h, the temperature of the solution in the reaction kettle is controlled at 60°C, the pH is 10.32, and the alkali React for 12 hours at a concentration of 5.0g/L and a rotation speed of 290r/min; Section II: Adjust the flow rate of the magnesium, nickel, iron and manganese mixed salt solution to 30ml/h, the flow rate of the NaOH alkali solution to 8ml/h, and the flow rate of the ammonia complexing agent solution 2ml/h, control the temperature of the solution in the reaction kettle to react for 24h under the conditions of 60°C, pH 10.20, alkalinity 5.0g/L, and rotation speed 280r/min, so that Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH ) ₂ crystal nucleation growth;

(6) Aging reaction: After the Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal in step (5) grows to D50 at 4-5um, add it to the reaction kettle with a flow rate of 50ml/h and a rotation speed of 200r/min. Add 4 mol/L NaOH alkali solution. After adding the NaOH alkali solution for 2 hours, continue aging for 10 hours at a rotation speed of 200 r/min and a temperature of 50-70°C;

(7) Washing: On the basis of step (6), shut down the reaction kettle, filter the solution in the reaction kettle, and obtain the filtered material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ solid. The filtered material Mg _0.1 Wash the Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ solid with deionized water repeatedly for 10 times until the pH value of the washed deionized water is less than 8.2 before stopping the washing;

(8) Drying: On the basis of step (7), dry the Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal at a drying temperature of 120°C and a drying time of 4 hours to obtain magnesium-doped modified nickel-iron-manganese. Base precursor material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ .

This comparative example is based on Example 1, adding the magnesium doping process to step (1), that is: mixing soluble magnesium salt and other soluble salts into the mixed salt solution. As shown in Figure 5, it is an SEM image of the precursor material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ prepared in Comparative Example 2. It can be seen from the figure that nickel, iron, manganese and magnesium are mixed in four elements for reaction. The difference in precipitation constants is large, making it difficult to form co-precipitation, resulting in segregation on the surface of the crystal structure, thus affecting the electrochemical and physical and chemical properties of the cathode material.

Comparative example 3

A preparation process for magnesium-doped modified nickel-iron-manganese-based precursor material, including the following steps:

(1) Solution preparation: Prepare magnesium sulfate, nickel sulfate, ferrous sulfate and manganese sulfate in a molar ratio of 0.1:0.3:0.3:0.3 to prepare a nickel-iron-manganese solution with a total metal ion concentration of 2mol/L and a volume of 0.5L. Mix the salt solution and 0.5L magnesium sulfate solution (for later use) to prepare a 4mol/L ammonia complexing agent solution and a 4mol/L NaOH alkali solution.

(2) Preparation of reaction bottom liquid: Pour a certain mass of deionized water into a 3L reaction kettle, add 0.461g of reducing agent ascorbic acid to the reaction kettle, and then add 0.69g of PVP on this basis, and finally add the prepared NaOH alkali solution and ammonia complexing agent solution were added to the reaction bottom solution, and the alkalinity of the system was adjusted to 5.0g/L, and the pH value was 11.2;

(3) Feeding: The nickel-iron-manganese mixed salt solution prepared in step (1) has a feeding flow rate of 6.7ml/h, the ammonia complexing agent solution has a feeding flow rate of 0.7mL/h, and the NaOH alkali solution has a feeding flow rate of 0.7ml/h. The feed flow rate is 2.7ml/h and added to the reaction kettle of step (2) under the protection of _N2 atmosphere and the rotation speed is 300r/min;

(4) Nucleation reaction: In the reaction kettle of step (3), control the temperature of the solution in the reaction kettle at 60°C, pH 11.2, alkalinity 5.0g/L, and rotation speed 300r/min according to steps ( Continue the feeding reaction under the feeding conditions of 3) for 2 hours to obtain Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal nuclei;

(5) Growth reaction: Use a one-stage process to carry out Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal nucleus growth reaction: In the reaction kettle of step (4), adjust the flow rate of the nickel iron and manganese mixed salt solution to 20 ml/h, and the NaOH alkali solution The flow rate is 5.8ml/h, the flow rate of ammonia complexing agent solution is 1.5ml/h, and the temperature of the solution in the reaction kettle is controlled at 60°C, pH 10.30, alkalinity 5.0g/L, and rotation speed 290r/min. React for 36 hours to grow Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal nuclei;

(6) Mg doping modification: In the reaction kettle of step (5), while reacting according to the feeding conditions of step (5), pump the magnesium sulfate solution at a flow rate of 9.48ml/h to a temperature of 60°C. In a reaction kettle with a pH of 10.2, an alkalinity of 5.0g/L, and a rotation speed of 280r/min, react for 10 hours to grow Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystals;

(7) Aging reaction: After the Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal in step (6) has grown to D50 at 4-5um, add it to the reaction kettle with a flow rate of 50ml/h and a rotation speed of 200r/min. Add 4 mol/L NaOH alkali solution. After adding the NaOH alkali solution for 2 hours, continue aging for 10 hours at a rotation speed of 200 r/min and a temperature of 50-70°C;

(8) Washing: On the basis of step (7), shut down the reaction kettle, filter the solution in the reaction kettle, and obtain the filtered material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ solid. The filtered material Mg _0.1 Wash the Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ solid with deionized water repeatedly for 10 times until the pH value of the washed deionized water is less than 8.2 before stopping the washing;

(9) Drying: On the basis of step (8), dry the Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal at a drying temperature of 120°C and a drying time of 4 hours to obtain magnesium-doped modified nickel-iron-manganese. Base precursor material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ .

This comparative example is based on Example 1, replacing the two-stage process of step (5) with one-stage process. As shown in Figure 6, it is an SEM image of the precursor material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ prepared in Comparative Example 3. It can be seen from the figure that due to the process change of the salt flow rate during the growth process, the precursor The crystal growth condition becomes worse, resulting in poor sphericity, which affects the overall performance of the cathode material.

Comparative example 4

A preparation process for magnesium-doped modified nickel-iron-manganese-based precursor material, including the following steps:

(1) Solution preparation: Prepare magnesium sulfate, nickel sulfate, ferrous sulfate and manganese sulfate in a molar ratio of 0.1:0.3:0.3:0.3 to prepare a nickel-iron-manganese solution with a total metal ion concentration of 2mol/L and a volume of 0.5L. Mix the salt solution and 0.5L magnesium sulfate solution (for later use) to prepare a 4mol/L ammonia complexing agent solution and a 4mol/L NaOH alkali solution.

(2) Preparation of reaction bottom liquid: Pour a certain mass of deionized water into a 3L reaction kettle, add 0.461g of reducing agent ascorbic acid to the reaction kettle, and then add 0.69g of PVP on this basis, and finally add the prepared NaOH alkali solution and ammonia complexing agent solution were added to the reaction bottom solution, and the alkalinity of the system was adjusted to 5.0g/L, and the pH value was 11.2;

(3) Feeding: The nickel-iron-manganese mixed salt solution prepared in step (1) has a feeding flow rate of 6.7ml/h, the ammonia complexing agent solution has a feeding flow rate of 0.7mL/h, and the NaOH alkali solution has a feeding flow rate of 0.7ml/h. The feed flow rate is 2.7ml/h and added to the reaction kettle of step (2) under the protection of _N2 atmosphere and the rotation speed is 300r/min;

(4) Nucleation reaction: In the reaction kettle of step (3), control the temperature of the solution in the reaction kettle at 60°C, pH 11.2, alkalinity 5.0g/L, and rotation speed 300r/min according to steps ( Continue the feeding reaction under the feeding conditions of 3) for 2 hours to obtain Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal nuclei;

(5) Growth reaction: Use a two-stage process to carry out the Ni _0.3 Fe _0.25 Mn _0.3 (OH) ₂ crystal nucleus growth reaction; proceed to section I first: in the reaction kettle of step (4), adjust the flow rate of the nickel iron and manganese mixed salt solution to 30 ml /h, the flow rate of NaOH alkali solution is 7.8ml/h, the flow rate of ammonia complexing agent solution is 1.9ml/h, the temperature of the solution is controlled at 60°C, the pH is 10.20, the alkalinity is 5.0g/L, and the rotation speed is 280r/min. React for 24 hours under the conditions; then proceed to section II: adjust the flow rate of the nickel-iron-manganese mixed salt solution to 10ml/h, the flow rate of the NaOH alkali solution to 3.9ml/h, the flow rate of the ammonia complexing agent solution to 1.1ml/h, and control the temperature of the solution React for 12 hours at 60°C, pH 10.32, alkalinity 5.0g/L, and rotation speed 290r/min; make Ni _0.3 Fe _0.25 Mn _0.3 (OH) ₂ crystal nuclei grow;

(6) Mg doping modification: In the reaction kettle of step (5), while reacting according to the feeding conditions of step (5), pump the magnesium sulfate solution at a flow rate of 9.482ml/h to a temperature of 60°C. In a reaction kettle with a pH of 10.2, an alkalinity of 5.0g/L, and a rotation speed of 280r/min, react for 10 hours to grow Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystals;

(7) Aging reaction: After the Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal in step (6) has grown to D50 at 4-5um, add it to the reaction kettle with a flow rate of 50ml/h and a rotation speed of 200r/min. Add 4 mol/L NaOH alkali solution. After adding the NaOH alkali solution for 2 hours, continue aging for 10 hours at a rotation speed of 200 r/min and a temperature of 50-70°C;

(8) Washing: On the basis of step (7), shut down the reaction kettle, filter the solution in the reaction kettle, and obtain the filtered material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ solid. The filtered material Mg _0.1 Wash the Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ solid with deionized water repeatedly for 10 times until the pH value of the washed deionized water is less than 8.2 before stopping the washing;

(9) Drying: On the basis of step (8), dry the Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ crystal at a drying temperature of 120°C and a drying time of 4 hours to obtain magnesium-doped modified nickel-iron-manganese. Base precursor material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ .

This comparative example is based on Example 1 and modifies the two-stage process parameters of step (5). As shown in Figure 6, it is an SEM image of the precursor material Mg _0.1 Ni _0.3 Fe _0.3 Mn _0.3 (OH) ₂ prepared in Comparative Example 4. It can be seen from the figure that due to the adjustment of the sequence of stages in the crystal growth process, the reaction The supersaturation in the system first increases and then decreases, which is different from that in Example 1 where the supersaturation is always decreasing, which leads to a nucleation phenomenon during the increase in saturation, resulting in a deterioration of the morphology of the precursor. The overall physical and chemical properties of the precursor are reduced.

The precursor materials prepared in Examples 1-3 and Comparative Examples 1-4 were made into sodium-ion batteries according to the following process and performed performance tests:

Mix the precursor material and sodium carbonate at a molar ratio of 1:1.02, sinter the mixture at 950°C, grind and sieve to obtain the cathode material; mix the cathode material, acetylene black and polyvinylidene fluoride (PVDF) binder according to the Weigh the mass ratio of 8.2:0.8:1. First dissolve the PVDF powder into dimethyl sulfoxide (DMSO) to obtain a binder with a concentration of 8%. Then add the positive electrode material and acetylene black, grind evenly, and apply it on Dry on aluminum foil, drying temperature 85℃, drying time 5h. Use a slicer to cut it into discs with a diameter of 10 mm, and compact it with a tablet press to obtain a positive electrode sheet. Using graphite sheets as the negative electrode, PE as the separator, and 1 mol/L NaPF6 as the electrolyte, a button cell was assembled in a glove box filled with argon. After the assembled button battery is left to stand at room temperature for 8 hours, it is tested in the charge and discharge voltage range of 3.0-4.3V. The first charge and discharge test is performed at 0.1C and 1C rate, and the cycle performance is tested at 1C.

Table 1 Electrochemical performance test results of Examples 1-3 and Comparative Examples 1-4

It can be seen from the data in Table 1 that the sodium-ion battery provided by the embodiment of the present invention has a greater improvement in various electrochemical properties compared with the sodium-ion battery provided by the comparative example. The present invention modifies nickel-iron-manganese-based materials by doping magnesium in appropriate steps, and through appropriate co-precipitation process settings, can significantly increase battery capacity and voltage, and enhance battery cycle performance.

Although the present invention has been disclosed above in terms of preferred embodiments, they are not intended to limit the present invention. Any person skilled in the art can make slight modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall be determined by the claims.

Claims (10)

1. A preparation process of magnesium-doped modified nickel-iron-manganese-based precursor material, which is characterized in that it 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 from soluble nickel salt, soluble iron salt, and soluble manganese salt, and mix soluble magnesium The salt is prepared into a soluble magnesium salt solution; an ammonia water complexing agent with a concentration of 2-5 mol/L is prepared; an alkali solution with a NaOH concentration of 2-5 mol/L is prepared; (2) Preparation of the reaction bottom liquid: Add deionized water to the reaction kettle, add the prepared alkali solution and ammonia complexing agent to the reaction kettle, and adjust the alkalinity of the system to 3.0-8.0g/L, pH Adjust the value to 10-11.5; (3) Feed: Flow the mixed salt solution, ammonia complexing agent, and alkali solution into the reaction kettle of step (2) under the protection of _N2 atmosphere and with a rotation speed of 200-400r/min, in which the mixed salt solution is fed The feed flow rate is 5-100ml/h, the feed flow rate of ammonia complexing agent is 0.5-30ml/h, and the feed flow rate of alkali solution is 2-50ml/h; (4) Nucleation reaction: In the reaction kettle of step (3), control the temperature of the solution at 50-70°C, pH at 10-11.5, alkalinity at 3.0-8.0g/L, and rotation speed at 200-400r/min. The conditions continue to feed the reaction for 0.5-2h to obtain crystal nuclei; (5) Growth reaction: In the reaction kettle of step (4), adjust the feed flow rate of the mixed salt solution to 7.5-30ml/h, the feed flow rate of the ammonia water complexing agent to 1.0-20ml/h, and the alkali solution The feed flow rate is adjusted to 3-16ml/h, and the temperature of the solution in the reaction kettle is controlled to be 50-70°C, the pH is 10-10.8, the alkalinity is 3.0-8.0g/L, and the rotation speed is 200-400r/min. Continuously feed the reaction for 2-48h to make the crystal nuclei grow; (6) Magnesium doping modification: Keep the continuous feeding in step (5), and pump the soluble magnesium salt solution into the reaction kettle at a flow rate of 7.5-30ml/h, and react for 8-12h to grow the crystal; (7) Aging reaction: After the crystals in step (6) grow to D50 of 4-5um, add 40-200ml alkali solution to the reaction kettle with a rotation speed of 200-400r/min at a feed flow rate of 20-60ml/h. , after the addition of the alkali solution is completed, continue aging for 8-12 hours at a rotation speed of 200-400r/min and a temperature of 50-70°C; (8) Washing: Filter the solution in the reaction kettle to obtain the filtered solid, and repeatedly wash the filtered solid with deionized water until the pH value of the washed deionized water is less than 8.2 to obtain washed crystals; (9) Drying: Dry the washed crystals to obtain a magnesium-doped modified nickel-iron-manganese-based precursor material. 2. The preparation process of a magnesium-doped modified nickel-iron-manganese-based precursor material as claimed in claim 1, characterized in that: in step (1), the molar ratio is x:y:z:1-x-y-z Prepare a nickel-iron-manganese-magnesium metal salt solution with a total metal ion concentration of 1-3 mol/L, 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 claimed in claim 1, characterized in that: the soluble nickel salt is NiSO ₄ ·6H ₂ O, and the soluble iron salt is FeSO ₄ ·7H ₂ O, the soluble manganese salt is MnSO ₄ ·H ₂ O, and the soluble magnesium salt is MgSO ₄ ·7H ₂ O. 4. The preparation process of a magnesium-doped modified nickel-iron-manganese-based precursor material as claimed in claim 1, characterized in that: in step (1), the ammonia complexing agent is formed by ammonia dissolved in water. The mixed solution has a molar concentration of 4mol/L. 5. The preparation process of a magnesium-doped modified nickel-iron-manganese-based precursor material as claimed in claim 1, characterized in that: in step (2), deionized water is introduced into the reaction kettle, and then soluble The total mass of nickel salt, soluble iron salt, soluble manganese salt and soluble magnesium salt is 1-3‰ of the reducing agent. The reducing agent is one of ascorbic acid, sodium ascorbate and hydrazine hydrate. Mix the prepared alkali solution and ammonia water. The complexing agent is added to the reaction bottom solution, and the alkalinity of the system is adjusted to 3.0-8.0g/L, and the pH value is 10-11.5. 6. The preparation process of a magnesium-doped modified nickel-iron-manganese-based precursor material as claimed in claim 1, characterized in that: in step (2), deionized water is introduced into the reaction kettle, and then soluble 1-5‰ of PVP based on the total mass of nickel salt, soluble iron salt, soluble manganese salt, and soluble magnesium salt. Finally, add the prepared alkali solution and ammonia complexing agent to the reaction bottom solution, and adjust the alkalinity of the system to 3.0-8.0g/L, pH value is 10-11.5. 7. The preparation process of a magnesium-doped modified nickel-iron-manganese-based precursor material as claimed in claim 1, characterized in that: in step (9), the drying temperature is 100-130°C, and the drying time is 4- 6h. 8. A kind of preparation process of magnesium-doped modified nickel-iron-manganese-based precursor material as claimed in claim 1, characterized in that the growth reaction of step (5) adopts a two-stage process: section 1: in step ( 4) In the reaction kettle, adjust the flow rate of the mixed salt solution to 8-12ml/h, the flow rate of the alkali solution to 3-4ml/h, the flow rate of the ammonia complexing agent to 1.0-1.2ml/h, and control the temperature of the solution in the reaction kettle. React for 10-15 hours at 58-62°C, pH 10.3-10.4, alkalinity 4.5-5.5g/L, and rotation speed 280-300r/min; Section II: Adjust the flow rate of the mixed salt solution to 28-30ml /h, the flow rate of the alkali solution is 7-8ml/h, the flow rate of the ammonia complexing agent is 1.8-2ml/h, the temperature of the solution in the reaction kettle is controlled at 58-60°C, the pH is 10.2-10.3, and the alkalinity is 4.5 React for 22-25h at -5.5g/L and a rotation speed of 280-300r/min to grow crystal nuclei. 9. Magnesium-doped modified nickel-iron-manganese-based precursor material prepared by the preparation process according to any one of claims 1 to 8. 10. A cathode material for a sodium-ion battery, characterized in that the cathode material is made of a composite of the magnesium-doped modified nickel-iron-manganese-based precursor material according to claim 9 and a sodium-containing material.