A Mo, V, Al co-doped double-core-shell structure ternary precursor and a preparation method thereof

Abstract

The application discloses a kind of by Mo, V, Al co-doped binuclear shell structure ternary precursor and preparation method thereof, belong to lithium ion battery material technical field.The precursor is with nickel cobalt manganese as main body, from inside to outside it is binuclear shell layer structure successively for inner core, intermediate layer, outer layer;The inner core is nickel cobalt manganese molybdenum vanadium doped structure, intermediate layer is nickel cobalt manganese molybdenum vanadium aluminum doped structure, outer layer is nickel cobalt manganese molybdenum aluminum doped structure.The preparation method is: three kinds of independent solution containing Mo, V, Al are respectively prepared, and control three element concentration equal;In the process of coprecipitation reaction, three-stage time-feeding strategy is used, realizes the gradient distribution of Mo, V, Al element in particle diameter direction, constructs binuclear shell structure.The application realizes the synergistic modification of inner core strengthening, intermediate layer stress relaxation, outer layer densification by element partition doping and structure gradient design, and the obtained precursor has good sphericity, high density, uniform grain, and excellent batch stability.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material precursor preparation technology, specifically relating to a ternary precursor with a dual core-shell structure co-doped by Mo, V, and Al and its preparation method. Background Technology

[0002] Ternary nickel-cobalt-manganese precursors are core raw materials for lithium-ion battery cathode materials (such as NCM and NCA series). Their structural integrity, particle density, grain uniformity, and doping modification effects directly determine the powder processing performance, sintering compatibility, and batch consistency of finished products. As the lithium battery industry continues to raise its quality control requirements for high-nickel ternary materials, conventional ordinary ternary precursors can no longer meet high-end mass production standards.

[0003] Traditional ternary precursors commonly suffer from bulk problems during large-scale co-precipitation preparation, such as uneven primary grain size, poor sphericity of secondary particles, loose internal packing, high porosity, and low powder tap density. Meanwhile, conventional modification methods often involve simultaneous homogeneous doping with single or dual elements, resulting in random distribution of dopant ions throughout the particle. This makes it impossible to achieve differentiated functional control based on structural strengthening requirements at different radial positions of the particles, leading to stress concentration within the particles, weak interfacial bonding strength, large fluctuations in batch production, and low yield.

[0004] Although Mo, V, and Al are three functional dopants, each with the potential to regulate grain growth, the industry currently lacks a precise three-element gradient layering doping process that can be industrialized. This makes it impossible to simultaneously achieve integrated regulation of core strengthening, middle layer stress relief, and outer layer densification, which restricts the stable mass production of high-end high-nickel ternary precursors.

[0005] Therefore, it is desirable to provide a ternary precursor with a dual-core-shell structure co-doped by Mo, V, and Al and its preparation method, which can solve the above-mentioned technical problems. Summary of the Invention

[0006] The first objective of this invention is to provide a ternary precursor with a dual-core-shell structure co-doped by Mo, V, and Al, overcoming the shortcomings of the prior art.

[0007] To achieve the above-mentioned objectives, this invention provides a ternary precursor with a dual-core-shell structure co-doped with Mo, V, and Al. The precursor is mainly composed of nickel, cobalt, and manganese, with Mo, V, and Al as doping elements. It has a binuclear shell structure, consisting of a core, an intermediate layer, and an outer layer from the inside out. The core is a nickel-cobalt-manganese-molybdenum-vanadium quaternary doped structure, the middle layer is a nickel-cobalt-manganese-molybdenum-vanadium-aluminum pentagonal doped structure, and the outer layer is a nickel-cobalt-manganese-molybdenum-aluminum quaternary doped structure. The concentrations of the three elements Mo, V, and Al in the corresponding doping solutions are equal, and the total doping amount of the three elements does not exceed 2% of the total mass of the precursor.

[0008] Specifically, the molar ratio of nickel, cobalt, and manganese is (5~9):(0.5~2):(0.5~3).

[0009] Specifically, the molar ratio of nickel, cobalt, and manganese is 8:1:1, 6:2:2, or 5:2:3.

[0010] Specifically, the concentrations of the three elements Mo, V, and Al are all 0.01~0.05 mol / L, and the total doping amount of the three elements is 0.5%~2% based on the total mass of the precursor.

[0011] The second objective of this invention is to provide a method for preparing a Mo, V, and Al co-doped ternary precursor with a dual core-shell structure, comprising the following steps: S1. Prepare three salt solutions: S1.1 Preparation of Solution 1: Dissolve the nickel source, cobalt source, and manganese source in deionized water according to a preset molar ratio, then add the molybdenum source and stir until completely dissolved to obtain solution 1 containing nickel, cobalt, manganese, and molybdenum; the nickel source, cobalt source, manganese source, and molybdenum source are each independently selected from their water-soluble salts, preferably sulfates, nitrates, or chlorides; S1.2 Preparation of Solution 2: Dissolve the vanadium source in deionized water, add dilute sulfuric acid to adjust the pH to 2-3, and stir until completely clear to obtain vanadium-containing solution 2; the vanadium source is selected from ammonium metavanadate, sodium vanadate or potassium vanadate; S1.3, Prepare solution 3: Dissolve the aluminum source in deionized water and stir until completely dissolved to obtain aluminum-containing solution 3; the aluminum source is selected from aluminum sulfate, aluminum nitrate or aluminum chloride; Wherein, the concentrations of Mo in solution 1, V in solution 2, and Al in solution 3 are equal; S2, staged feed co-precipitation reaction: Add deionized water to the reactor, introduce protective gas, adjust the temperature to 50~60℃, start stirring, adjust the pH of the reaction system to 10.0~11.0, and the ammonia concentration to 0.5~1.0mol / L; Solution 1 is continuously fed throughout the process at a constant feed rate; the total reaction time is 12-24 hours, divided into three stages: S2.1, First stage: Only solution 1 and solution 2 are introduced, and solution 1 and solution 2 are fed at the same time. The feeding time is 25%~35% of the total reaction time, forming a nickel-cobalt-manganese-molybdenum-vanadium doped core; S2.2, Second stage: Solution 1, Solution 2 and Solution 3 are introduced simultaneously, and the feeding time is 30% to 40% of the total reaction time, forming a nickel-cobalt-manganese-molybdenum-vanadium-aluminum doped intermediate layer outside the core. S2.3, Third stage: Only solution 1 and solution 3 are introduced, and solution 1 and solution 3 are fed at the same time. The feeding time is 25% to 35% of the total reaction time, and a nickel-cobalt-manganese-molybdenum-aluminum doped outer layer is formed outside the intermediate layer. The feed rates of solution 2 and solution 3 at their respective stages are controlled independently, with the feed rate range being 5~10 mL / min. S3, Post-processing: After the reaction was completed, the resulting precipitate was washed, dried, and pulverized to obtain the ternary precursor with a dual core-shell structure co-doped by Mo, V, and Al.

[0012] Specifically, in step S1.2, the dilute sulfuric acid is used to adjust the pH to 2.5.

[0013] Specifically, in step S2, the stirring rate is 300~500 r / min, and the feed rate of solution 1 is 5~10 mL / min.

[0014] Specifically, in step S3, the washing is performed until the pH of the washing solution is 7.0, and the drying is performed at 80~100℃ for 12~24h.

[0015] The present invention provides a Mo, V, and Al co-doped binuclear-shell ternary precursor and its preparation method, which have the following advantages over the prior art: (1) This invention constructs a dual-core shell three-layer composite structure with Mo / V / Al gradient distribution for the first time by precisely segmented sequential feeding, realizing the partitioned synergistic modification of the core strengthening framework, the middle layer slowing down stress, and the outer layer dense protection, breaking through the technical limitations of traditional homogeneous doping without functional partitioning. (2) The three doping elements are precisely matched in equal concentration and the total doping amount is strictly controlled to be less than 2%. This not only effectively refines the primary grains and improves the particle packing density, but also avoids abnormal grain growth and micro-defects induced by high doping. The resulting powder has complete spherical shape, good flowability and high mechanical strength. (3) The present invention has strong process compatibility. Relying on conventional co-precipitation reaction equipment, only the liquid preparation logic and segmented feeding sequence are optimized. No additional production line modification is required. Mass production stability is high, batch fluctuation is small, and industrialization implementation cost is low. (4) The prepared precursor has high density, uniform grains, and complete structure, and has good matching with the solid-state sintering of lithium source, which is suitable for the large-scale mass production processing needs of high-end high-nickel ternary cathode. Attached Figure Description

[0016] Figure 1 The image shows a scanning electron microscope image of the precursor powder prepared in Example 1. Figure 2 The image shows a scanning electron microscope image of the precursor powder prepared in Example 2. Figure 3 This is a scanning electron microscope image of the precursor powder prepared in Example 3. Detailed Implementation

[0017] The specific embodiments of the present invention will be described in further detail below. Example 1

[0018] A ternary precursor with a dual-core-shell structure co-doped by Mo, V, and Al has a core of nickel-cobalt-manganese-molybdenum-vanadium, an intermediate layer of nickel-cobalt-manganese-molybdenum-vanadium-aluminum, and an outer layer of nickel-cobalt-manganese-molybdenum-aluminum; Ni:Co:Mn=8:1:1 (molar ratio), the concentrations of Mo, V, and Al are all 0.02 mol / L, and the total doping amount is 1.0% (based on the total mass of the precursor).

[0019] Its preparation method includes the following steps: Step 1: Prepare three salt solutions 1.1 Solution 1: Dissolve nickel sulfate, cobalt sulfate, and manganese sulfate in deionized water at a molar ratio of 8:1:1, add a predetermined amount of ammonium molybdate, and stir until completely dissolved. Control the concentration of Mo in solution 1 to be 0.02 mol / L and the total metal ion concentration to be 1.8 mol / L. 1.2 Solution 2: Dissolve ammonium metavanadate in deionized water, add a small amount of dilute sulfuric acid to adjust the pH to 2.5, stir until completely clear, and control the concentration of element V in solution 2 to be 0.02 mol / L; 1.3 Solution 3: Dissolve aluminum sulfate in deionized water and stir until completely dissolved, controlling the Al element concentration in solution 3 to be 0.02 mol / L; Step 2: Staged feed co-precipitation reaction Add 2L of deionized water to a 5L reactor, purge with nitrogen for protection, adjust the temperature of the constant temperature water bath to 55℃, turn on the mechanical stirrer at a stirring rate of 400r / min, adjust the pH of the reaction system to 10.5 with sodium hydroxide solution, and adjust the ammonia concentration to 0.8mol / L with ammonia water; continuously feed solution 1 throughout the process at a feed rate of 8mL / min, and the total reaction time is 18h; 2.1 First stage: Solution 1 and Solution 2 are introduced, with a feeding time of 6 hours, to form a nickel-cobalt-manganese-molybdenum-vanadium core; 2.2 Second stage: Solution 1, Solution 2 and Solution 3 are introduced simultaneously for 7 hours to form a nickel-cobalt-manganese-molybdenum-vanadium-aluminum intermediate layer; 2.3 Third stage: Introduce solutions 1 and 3 for 5 hours to form a nickel-cobalt-manganese-molybdenum-aluminum outer layer; Step 3: Post-processing After the reaction was completed, stirring was continued for 30 minutes, vacuum filtration was performed, and the precipitate was washed with deionized water until the pH of the washing solution was 7.0. The precipitate was then placed in a forced-air drying oven and dried at 90°C for 18 hours. After pulverization, the target precursor was obtained. Example 2

[0020] A ternary precursor with a dual-core-shell structure co-doped by Mo, V, and Al has a core of nickel-cobalt-manganese-molybdenum-vanadium, an intermediate layer of nickel-cobalt-manganese-molybdenum-vanadium-aluminum, and an outer layer of nickel-cobalt-manganese-molybdenum-aluminum; Ni:Co:Mn=6:2:2 (molar ratio), the concentrations of Mo, V, and Al are all 0.03 mol / L, and the total doping amount is 1.5% (based on the total mass of the precursor).

[0021] Its preparation method is basically the same as that in Example 1, except that: In step 1, the concentrations of Mo, V, and Al in solutions 1, 2, and 3 are all 0.03 mol / L. In step 2, the total reaction time is 20 h, the first stage feeding time is 5 h, the second stage feeding time is 8 h, the third stage feeding time is 7 h, the reaction temperature is 50 ℃, the stirring rate is 350 r / min, the pH is 10.0, the ammonia concentration is 0.6 mol / L, and the feeding rate of solution 1 is 7 mL / min. Example 3

[0022] A ternary precursor with a dual-core-shell structure co-doped by Mo, V, and Al has a core of nickel-cobalt-manganese-molybdenum-vanadium, an intermediate layer of nickel-cobalt-manganese-molybdenum-vanadium-aluminum, and an outer layer of nickel-cobalt-manganese-molybdenum-aluminum; Ni:Co:Mn=5:2:3 (molar ratio); the concentrations of Mo, V, and Al are all 0.01 mol / L; and the total doping amount is 0.8% (based on the total mass of the precursor).

[0023] Its preparation method is basically the same as that in Example 1, except that: In step 1, the concentrations of Mo, V, and Al in solutions 1, 2, and 3 are all 0.01 mol / L. In step 2, the total reaction time is 15 h, the first stage feeding time is 5 h, the second stage feeding time is 5 h, the third stage feeding time is 5 h, the reaction temperature is 60 ℃, the stirring rate is 450 r / min, the pH is 11.0, the ammonia concentration is 0.9 mol / L, and the feeding rate of solution 1 is 9 mL / min. Comparative Example 1 (Random Feed Duration)

[0024] The raw material ratio, salt solution concentration, reaction temperature, pH, stirring speed, and total reaction time of this comparative example are completely consistent with those of Example 1. The only difference is that it does not follow the three-stage feeding time ratio range defined by this invention, but arbitrarily extends the feeding time of the first stage, significantly compresses the transition growth time of the second stage, and reduces the outer layer coating time of the third stage. The remaining post-processing steps are exactly the same, and a comparative precursor sample is prepared. Comparative Example 2 (Traditional One-Step Co-doping)

[0025] In this comparative example, Mo salt, V salt, and Al salt were all mixed with nickel-cobalt-manganese main salt in advance to prepare a single mixed salt solution. The traditional one-step synchronous co-precipitation feeding method was adopted. All reaction environment parameters, total doping amount, and post-processing process were completely consistent with those in Example 1, and a conventional three-element homogeneous doped comparative precursor was prepared. Comparative Example 3 (non-equal concentration, high total doping amount)

[0026] The difference between this comparative example and Example 1 is that the concentrations of Mo, V, and Al are not equal (Mo 0.02 mol / L, V 0.04 mol / L, Al 0.01 mol / L), and the total doping amount is 3.0% (based on the total mass of the precursor). The same three-stage feeding method as in Example 1 was used, and all other parameters were the same. The resulting precursor particles exhibited generally poor sphericity, uneven primary grain size, and a tap density of only 1.98 g / cm³, with numerous internal pores. This indicates that equal concentration matching and control of the total doping amount are crucial for obtaining a superior structure. Performance testing

[0027] The precursor powders of each embodiment and comparative sample were subjected to routine physicochemical characterization, and the results are shown in Table 1: Table 1 shows the routine physicochemical characterization of precursor powders for Examples 1-3 and Comparative Examples 1-3.

[0028] Test results show that: Figures 1-3 As shown in Table 1, the precursors prepared in Examples 1-3 of this invention exhibit excellent spherical integrity, fine and uniform primary grains, high tap density (2.28~2.36 g / cm³), no loose pores or only trace pores, clear three-layer gradient structure, and excellent batch consistency. In contrast, Comparative Example 1 failed to achieve enhanced partitioning due to disrupted segmented sequential doping; Comparative Example 2 used traditional synchronous doping; and Comparative Example 3 had inconsistent element concentrations and exceeded the total doping limit (3.0%), resulting in a significant decrease in overall performance (tap densities of only 2.05, 1.96, and 1.98 g / cm³, respectively, with loose or porous internal particles and blurred or missing layered structures).

[0029] The mechanism lies in the unique roles of the three doping elements: Mo, V, and Al. Mo refines primary grains and promotes particle densification; V helps control grain orientation and morphology; and Al enhances lattice stability and inhibits microcrack propagation. This invention achieves a gradient distribution of the three elements radially across the particles through independent preparation at equal concentrations and precise three-stage sequential feeding: Mo / V co-doping in the core constructs a high-strength framework structure; Mo / V / Al co-doping in the middle layer effectively buffers stress transmitted from the inside out; and Mo / Al co-doping in the outer layer provides dense surface protection. This zonal synergistic design avoids the interface stress concentration and structural defects caused by the indiscriminate distribution of elements in traditional homogeneous doping, while controlling the total doping amount to within 2%. This leverages the modification advantages of each element while preventing abnormal grain growth and microscopic defects caused by excessive doping. Comparative analysis demonstrates that this invention, through independent preparation of the three salts at equal concentrations coupled with precise three-stage sequential feeding, is the core key to improving the overall quality of the precursor.

[0030] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A ternary precursor with a dual-core-shell structure co-doped by Mo, V, and Al, characterized in that: The precursor is mainly composed of nickel, cobalt, and manganese, with Mo, V, and Al as doping elements. It has a binuclear shell structure, consisting of a core, an intermediate layer, and an outer layer from the inside out. The core is a nickel-cobalt-manganese-molybdenum-vanadium quaternary doped structure, the middle layer is a nickel-cobalt-manganese-molybdenum-vanadium-aluminum pentagonal doped structure, and the outer layer is a nickel-cobalt-manganese-molybdenum-aluminum quaternary doped structure. The concentrations of the three elements Mo, V, and Al in the corresponding doping solutions are equal, and the total doping amount of the three elements does not exceed 2% of the total mass of the precursor.

2. The ternary precursor with a dual-core-shell structure co-doped by Mo, V, and Al according to claim 1, characterized in that, The molar ratio of nickel, cobalt, and manganese is (5~9):(0.5~2):(0.5~3).

3. The ternary precursor with a dual-core-shell structure co-doped by Mo, V, and Al as described in claim 2, characterized in that, The molar ratio of nickel, cobalt, and manganese is 8:1:1, 6:2:2, or 5:2:

3.

4. The ternary precursor with a dual-core-shell structure co-doped by Mo, V, and Al as described in claim 1, characterized in that, The concentrations of the three elements Mo, V, and Al are all 0.01~0.05 mol / L, and the total doping amount of the three elements is 0.5%~2% based on the total mass of the precursor.

5. A method for preparing a ternary precursor with a dual-core-shell structure co-doped by Mo, V, and Al, characterized in that, Includes the following steps: S1. Prepare three salt solutions: S1.1 Preparation of Solution 1: Dissolve the nickel source, cobalt source, and manganese source in deionized water according to a preset molar ratio, then add the molybdenum source and stir until completely dissolved to obtain solution 1 containing nickel, cobalt, manganese, and molybdenum; the nickel source, cobalt source, manganese source, and molybdenum source are each independently selected from their water-soluble salts, preferably sulfates, nitrates, or chlorides; S1.2 Preparation of Solution 2: Dissolve the vanadium source in deionized water, add dilute sulfuric acid to adjust the pH to 2-3, and stir until completely clear to obtain vanadium-containing solution 2; the vanadium source is selected from ammonium metavanadate, sodium vanadate or potassium vanadate; S1.3, Prepare solution 3: Dissolve the aluminum source in deionized water and stir until completely dissolved to obtain aluminum-containing solution 3; the aluminum source is selected from aluminum sulfate, aluminum nitrate or aluminum chloride; Wherein, the concentrations of Mo in solution 1, V in solution 2, and Al in solution 3 are equal; S2, staged feed co-precipitation reaction: Add deionized water to the reactor, introduce protective gas, adjust the temperature to 50~60℃, start stirring, adjust the pH of the reaction system to 10.0~11.0, and the ammonia concentration to 0.5~1.0mol / L; Solution 1 is continuously fed throughout the process at a constant feed rate; the total reaction time is 12-24 hours, divided into three stages: S2.1, First stage: Only solution 1 and solution 2 are introduced, and solution 1 and solution 2 are fed at the same time. The feeding time is 25%~35% of the total reaction time, forming a nickel-cobalt-manganese-molybdenum-vanadium doped core; S2.2, Second stage: Solution 1, Solution 2 and Solution 3 are introduced simultaneously, and the feeding time is 30% to 40% of the total reaction time, forming a nickel-cobalt-manganese-molybdenum-vanadium-aluminum doped intermediate layer outside the core. S2.3, Third stage: Only solution 1 and solution 3 are introduced, and solution 1 and solution 3 are fed at the same time. The feeding time is 25% to 35% of the total reaction time, and a nickel-cobalt-manganese-molybdenum-aluminum doped outer layer is formed outside the intermediate layer. S3, Post-processing: After the reaction was completed, the resulting precipitate was washed, dried, and pulverized to obtain the ternary precursor with a dual core-shell structure co-doped by Mo, V, and Al.

6. The method for preparing a Mo, V, and Al co-doped ternary precursor with a dual core-shell structure as described in claim 5, characterized in that, In step S1.2, the dilute sulfuric acid is used to adjust the pH to 2.

5.

7. The method for preparing a Mo, V, and Al co-doped ternary precursor with a dual-core-shell structure as described in claim 5, characterized in that, In step S2, the stirring rate is 300~500 r / min, the feed rate of solution 1 is 5~10 mL / min, and the feed rates of solution 2 and solution 3 in the corresponding stages are controlled independently, with the feed rate range being 5~10 mL / min.

8. The method for preparing a Mo, V, and Al co-doped ternary precursor with a dual core-shell structure as described in claim 5, characterized in that, In step S3, the washing is performed until the pH of the washing solution reaches 7.0, and the drying is performed at 80~100℃ for 12~24h.

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