Ultra-high tap density small particle manganese-rich precursor and method of making same

Abstract

This invention discloses an ultra-high tap density small-particle manganese-rich precursor, comprising a core and a shell. The core region consists of tightly packed, thin-plate-like structures, referred to as a primary particle dense packing structure. The shell region consists of tightly packed, thin-plate-like structures, with uniformly packed, thin-plate-like structures forming spherical or near-spherical secondary particles. This invention also discloses a method for preparing the ultra-high tap density small-particle manganese-rich precursor, comprising the following steps: Step 1, a nucleation stabilization period, preparing a reaction system; Step 2, a pH surge dense core formation period, preparing a core structure, forming a primary particle core structure with tightly packed, thin-plate-like structures; Step 3, an ultra-long slope segmented oxidation shell growth period, completing the morphological growth of the shell, and obtaining an ultra-high tap density small-particle manganese-rich precursor. This invention belongs to the field of lithium-ion / sodium-ion battery cathode material technology, solving the problem in existing technologies where small particles, ultra-high tap density, and high specific surface area are difficult to achieve simultaneously.

Description

Technical Field

[0001] This invention belongs to the field of cathode material technology for lithium-ion batteries / sodium-ion batteries, and relates to an ultra-high tap small particle manganese-rich precursor. This invention also relates to a method for preparing the ultra-high tap small particle manganese-rich precursor. Background Technology

[0002] Manganese-rich precursor (chemical formula Ni) a Mn b (OH)₂, b≥0.50, or containing trace amounts of Co and doping elements) is a core intermediate for manufacturing lithium-rich manganese-based cathode materials (Li-rich layered oxide) and P₂ / O₃-type sodium-ion battery layered oxide cathode materials. Studies have shown that lithium-ion / sodium-ion battery cathode materials largely inherit the structure of the precursor. The physicochemical parameters of the precursor, such as particle size, tap density, and specific surface area, directly determine the tap density, capacity utilization, and cycle stability of the cathode material. Small-particle (D₅₀ < 5 μm) manganese-rich precursors have significant application value in high-power-density batteries due to their shorter ion diffusion paths, higher sintering activity, and superior electrochemical kinetics performance. However, existing technologies face two major contradictions in the preparation of small-particle manganese-rich precursors: First, the smaller the particle size, the larger the particle packing voids and the lower the tap density. Typically, the TD of manganese-rich precursors with D50 < 5 μm is difficult to exceed 1.5 g / cm³. Second, there is an inherent contradiction between high specific surface area (loose and porous) and high tap density (dense packing), which is difficult to balance in actual production and restricts the overall performance of small-particle finished products.

[0003] The limitations of the existing main technical routes are as follows: (a) Although the carbonate co-precipitation process can obtain better sphericity, carbonates are easily broken under high pressure in real time, and Ni precipitation is incomplete, resulting in a large loss of raw materials; (b) The hydroxide process + organic complexing agent (such as EDTA) can refine the primary particles, but the organic complexing agent increases the cost of wastewater treatment, which is not conducive to large-scale production; (c) The oxidation process that introduces oxygen-containing gas (air or O2) throughout the process is difficult to control precisely, resulting in uneven morphology of primary particles, and the continuous oxidation at the end of the reaction destroys the good morphology that has been formed; (d) Increasing the ammonia value and increasing the feed flow rate can adjust the morphology of primary particles and improve the compaction, but the effect on improving the compaction density of ultra-small particles (D50 < 3 μm) is limited.

[0004] In summary, there is currently no technical solution that can simultaneously achieve the synergistic optimization of small particles (D50=2~4μm), ultra-high tap density (dense packing TD≥1.5g / cm³), and suitable specific surface area (loose and porous, 15~40m² / g). Summary of the Invention

[0005] The purpose of this invention is to provide a manganese-rich precursor with ultra-high tap density and small particles, which solves the problem in the prior art that it is difficult to achieve both small particle size and ultra-high tap density and high specific surface area.

[0006] Another objective of this invention is to provide a method for preparing the ultra-high tapped small particle manganese-rich precursor, which solves the problem that there is an inherent contradiction between high specific surface area and high tapped density, making it difficult to achieve both in actual production.

[0007] The technical solution adopted in this invention is an ultra-high tapped small particle manganese-rich precursor, comprising a core and a shell. The core region is densely packed in fine plates, which is called a primary particle dense packing structure. The shell region is densely packed in thin plates, and the uniform fine plate packing constitutes spherical or near-spherical secondary particles.

[0008] Another technical solution adopted in this invention is a method for preparing ultra-high tapped small particle manganese-rich precursors, which is implemented according to the following steps: Step 1: Nucleation stabilization period, preparation of the reaction system; Step 2: During the pH surge and dense core formation period, a core structure is prepared, forming a primary particle core structure with fine, densely packed lamellar structures; Step 3: The ultra-long slope segmented oxidation shell growth period completes the morphological growth of the shell, and produces a manganese-rich precursor with ultra-high tap density small particles.

[0009] The beneficial effect of this invention is that, by integrating two technical routes, it innovates a three-stage pH-programmed combined segmented hydrogen peroxide controlled oxidation synergistic process for preparation: Step 1 is the nucleation and stabilization period, in which co-precipitation nucleation occurs under inert atmosphere (nitrogen) protection and high pH (11.5-12.5) conditions. After D50 drops to its minimum value, the reaction is stabilized for 3-6 hours to ensure uniform dispersion of crystal nuclei; Step 2 is the pH-surge dense nucleus formation period, in which the pH is rapidly increased by 0.3-0.8 units, and the reaction is maintained at a high supersaturation of 0.1. For 5–2 hours, a dense, lamellar core structure is formed from primary particles. Step 3 is the ultra-long slope segmented oxidation shell growth period, during which the pH is slowly decreased at a rate of 0.05–0.20 pH units / h, while hydrogen peroxide is simultaneously introduced in stages using a high-precision metering pump (3%–10% oxidation degree in the first stage and 5%–20% in the second stage) for controlled oxidation, refining the outer primary particles, increasing the sample's specific surface area, and switching to pure nitrogen protection 8–12 hours before the end of the reaction to eliminate residual oxidative activity and stabilize the final morphology. Specifically, this process includes the following advantages: (1) The pH-increased dense core process is organically combined with the segmented hydrogen peroxide controlled oxidation process to achieve a particle size D50 of 2-4 μm, a tap density TD ≥ 1.5 g / cm³, and a specific surface area of ​​15-40 m² / g. The three indicators are coordinated and balanced, breaking through the technical bottleneck of the industry. (2) The high density of the core guides the dense stacking of primary particles to ensure the tap density, and the external growth adopts staged oxidation to form a high specific surface area to ensure the capacity. (3) The final stage switches to pure nitrogen protection strategy to eliminate residual oxidation activity, stabilize the final morphology, and significantly improve the batch stability of finished products. (4) No organic complexing agent is required. The process is green and low-cost, and suitable for industrial scale-up. (5) The segmented oxidation and ultra-long pH slope are controlled in synergy to suppress the agglomeration during the nucleation period, reduce the number of granules, optimize the sphericity of secondary particles, and achieve uniform particle size distribution ((D90-D10) / D50≤0.65). Attached Figure Description

[0010] Figure 1a This is a microscopic image of the dense kernel of Embodiment 1 of the method of the present invention; Figure 1b This is a microscopic image of the dense packing of particles in Example 1 of the method of the present invention; Figure 1c This is a microscopic image of the secondary particle sphericity in Example 1 of the method of the present invention; Figure 2a This is a microscopic image of the dense kernel of Embodiment 2 of the method of the present invention; Figure 2b This is a microscopic image of the dense packing of particles in Example 2 of the method of the present invention; Figure 3a This is a microscopic image of the dense kernel in Embodiment 3 of the method of the present invention; Figure 3b This is a microscopic image of the dense packing of particles in Example 3 of the method of the present invention; Figure 4a This is a microscopic image of the dense kernel of Embodiment 4 of the method of the present invention; Figure 4b This is a microscopic image of the dense packing of particles in Example 4 of the method of the present invention; Figure 5a This is a microscopic image of the loose kernel of Comparative Example 1; Figure 5b This is a microscopic image of the loosely packed particles in Comparative Example 1. Figure 6a This is a microscopic image of the dense packing of particles in Comparative Example 2; Figure 6b This is a microscopic image of the secondary particles of *Gynostemma pentaphyllum* in Comparative Example 2. Figure 7a This is a microscopic image of the loose particle packing in Comparative Example 3; Figure 7b This is a microscopic image of the secondary particles of *Gynostemma pentaphyllum* in Comparative Example 3. Detailed Implementation

[0011] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0012] This invention employs a three-stage pH program control strategy combined with segmented hydrogen peroxide controllable oxidation technology. On one hand, it provides an ultra-high tap density small-particle manganese-rich precursor with a dense core-shell structure: a densely packed core (formed under a high supersaturation pH surge environment, where primary particles are tightly packed in a thin sheet-like manner) and a thin, sheet-like shell uniformly covered by primary particles (formed by segmented hydrogen peroxide controllable oxidation). On the other hand, it also provides a method for preparing this manganese-rich precursor, the core of which lies in a three-stage synergistic process: Step 1, the nucleation and stabilization period (inert atmosphere, high pH nucleation followed by heat stabilization for 3-6 hours) → Step 2, the pH surge dense core formation period (pH rapidly increases by 0.3-0.8 units, forming a dense sheet-like core under high supersaturation) → Step 3, the ultra-long pH slope segmented oxidation shell growth period (pH slowly decreases by 0.05-0.20 units / hour, hydrogen peroxide is precisely introduced in segments to form a porous structure, and pure nitrogen protection is switched for the last 8-12 hours).

[0013] The ultra-high tap density small particle manganese-rich precursor of the present invention includes a core and a shell. The core region is densely packed in fine plates, and the interior is called a primary particle dense packing structure. The shell region is densely packed in thin plates, and the uniform fine plate packing constitutes spherical or near-spherical secondary particles.

[0014] The general chemical formula of the manganese-rich precursor is Ni. a Mn b (OH)2, where a+b=1, 0.20≤a≤0.50, 0.50≤b≤0.80; or, the general chemical formula of the manganese-rich precursor is NixCoyMnzMw(OH)2, where x+y+z=1, 0.15≤x≤0.50, 0≤y≤0.20, 0.50≤z≤0.80, 0≤w≤0.10, and component M is selected from at least one of Ti, Mg, Al, W, Mo, Nb, Zr, Y, P, B, F, Cl, Br.

[0015] The particle size distribution of the manganese-rich precursor satisfies: (D90-D10) / D50≤0.65; The particle size D50 of the manganese-rich precursor satisfies: 2μm≤D50≤4μm; The tap density TD of the manganese-rich precursor satisfies: TD ≥ 1.5 g / cm³; The specific surface area (BET) of the manganese-rich precursor satisfies: 15 m² / g ≤ BET ≤ 40 m² / g.

[0016] The preparation method of the ultra-high tap density small particle manganese-rich precursor of the present invention is carried out according to the following steps: Step 1: Nucleation and stabilization period, preparation of the reaction system. 1.1) Prepare a mixed salt solution of nickel-manganese or nickel-cobalt-manganese using metal salts, and simultaneously prepare the bottom liquid of the reaction vessel; The nickel salt shall be selected from at least one of nickel sulfate, nickel chloride, and nickel nitrate; The manganese salt is selected from at least one of manganese sulfate, manganese chloride, and manganese nitrate. The cobalt salt is selected from at least one of cobalt sulfate, cobalt chloride, and cobalt nitrate; The aforementioned nickel, cobalt, and manganese salts are configured in various combinations using nickel / cobalt / manganese molar ratios.

[0017] The molar ratio of nickel salt, manganese salt and / or cobalt salt in the mixed salt solution is adjusted according to the precursor chemical formula, and the total concentration of the mixed salt solution is 0.5-2.5 mol / L, preferably 1.5-2.0 mol / L; The base solution is a mixed solution of deionized water and sodium hydroxide, with a pH of 11.5–12.5, preferably 11.8–12.0; the volume of the base solution accounts for 50%–70% of the effective volume of the reactor, and no ammonia water needs to be added when preparing the base solution; 1.2) The prepared mixed salt solution, complexing agent, and precipitant were added to the bottom liquid of the reaction vessel at the same time. Under the protection of an inert atmosphere, co-precipitation nucleation was carried out at a pH of 11.5 to 12.5. The mixture was stirred continuously until the particle size D50 dropped to the minimum value. The reaction was then stabilized for 3 to 6 hours to obtain the reaction system. The complexing agent is an inorganic complexing agent, with an ammonia concentration of 0.01–0.30 mol / L, preferably 0.05–0.20 mol / L; The precipitant is selected from sodium hydroxide solution and / or potassium hydroxide solution, with a solution concentration of 5-15 mol / L, preferably 8-10 mol / L; The stirring speed during the nucleation stage is 600–900 r / min, preferably 700–850 r / min, and the stirring temperature is 40–70℃. The duration of the nucleation period (the stabilization time after D50 drops to its minimum value) is 3–6 h, preferably 4 h.

[0018] Step 2: During the pH surge and dense core formation phase, the core structure was prepared. The reaction system is further processed in the reactor of step 1, and the pH of the reaction system is rapidly increased by 0.3 to 0.8 units within 0.5 to 1.0 h, preferably 0.4 to 0.6. The reaction is maintained at high supersaturation for 0.15 to 2 h, preferably 1 h, to form a primary particle core structure in the form of fine sheet-like dense stacking. In step 2, an inert gas is introduced throughout the process for protection, and no oxidant is introduced.

[0019] Step 3: The segmented oxidation growth period of the ultra-long slope completes the morphological growth of the shell. 3.1) Slowly reduce the pH at a rate of 0.05–0.20 pH units / h, preferably 0.08–0.15 pH units / h; simultaneously use a high-precision metering pump to introduce hydrogen peroxide in stages for controlled oxidation (hydrogen peroxide oxidation degree is 3%–20%), and gradually increase the hydrogen peroxide feed flow rate; the hydrogen peroxide oxidation degree is 3%–10% in the early stage of particle growth (when D50 < target D50 × 0.6) and 5%–20% in the later stage (when D50 ≥ target D50 × 0.6), forming a gradient distribution of oxidation degree that gradually increases from the inside to the outside.

[0020] The oxidation degree of hydrogen peroxide is defined as the molar amount of H2O2 in hydrogen peroxide per unit time and the molar amount of Mn entering the system in the same time. 2+ The molar ratio is expressed as a percentage; the hydrogen peroxide concentration is 1% to 10% wt, preferably 3% to 6% wt; The hydrogen peroxide feed is controlled by a high-precision metering pump, with flow fluctuations ≤ ±5%; the D50 change trend is monitored by a laser particle size analyzer, which serves as the basis for switching conditions at each stage.

[0021] 3.2) Reduce the stirring speed according to the growth particle size stage. The stirring speed range during the shell growth period is 400-600 r / min. Stop the hydrogen peroxide feeding 8-12 hours before the end of the reaction and switch to pure nitrogen protection until the end of the reaction to stabilize the final morphology. Stop feeding when D50 reaches the target particle size (2-4 μm) to obtain a manganese-rich precursor with ultra-high tap density small particles.

[0022] In addition, in step 3, the feed flow rate is increased slowly in an incremental manner, with an increase of 10% to 25% every 1 hour; the final amount of metal salt solution introduced in 1 hour is 3% to 10% of the effective volume of the reactor; the reaction temperature is maintained at 40℃ to 70℃ throughout the process; the overall duration of step 3 is 50 to 100 hours; the nitrogen switching point at the end of step 3 is 8 to 12 hours before the end of the reaction, preferably 10 hours; the nitrogen flow rate at the end of step 3 is 200 to 600 mL / min.

[0023] Step 4: This also includes a post-processing stage, in which alkaline washing, water washing, and drying are performed to obtain the finished product of ultra-high tap density small-particle manganese-rich precursor. After the reaction is complete, the obtained precursor slurry is alkali washed 1 to 3 times with an alkaline solution of 0.5 to 3.0 mol / L, and then washed 1 to 3 times with water at 50℃ to 100℃ until the impurities Na < 100 ppm and S < 1000 ppm in the filtered material; then it is dried by forced air at 80℃ to 120℃ for 8 to 24 hours to obtain the finished product of ultra-high tap density small particle manganese-rich precursor.

[0024] Example 1 The baseline scheme has the following composition ratio: Ni:Mn = 35:65, and the target D50 = 2.5 μm.

[0025] Preparatory steps, solution preparation: Weigh nickel sulfate and manganese sulfate according to the Ni:Mn molar ratio of 35:65 and dissolve them in deionized water to prepare a mixed salt solution A with a total concentration of 2.0 mol / L; prepare a 10 mol / L sodium hydroxide solution as a precipitant; prepare 5 wt% hydrogen peroxide (feeded by a high-precision metering pump); prepare a 4 mol / L ammonia solution as a complexing agent to prepare high-purity nitrogen gas (nitrogen purity of 99.99%).

[0026] Step 1, Nucleation Stabilization Period: Add deionized water and sodium hydroxide solution to a 50L effective volume reactor to prepare a base solution with pH=12.0 (the volume of the base solution is approximately 60% of the effective volume), and heat to 60℃; continuously purge nitrogen gas (500mL / min) into the reactor for protection; add mixed salt solution A to the prepared base solution at a fixed flow rate (3.0% of the effective volume per hour), purge with prepared ammonia water to control the ammonia concentration in the reactor at 0.2mol / L, purge with sodium hydroxide to strictly control pH=12.0±0.1, stir at 800r / min, maintain the temperature at 60℃, and do not purge with hydrogen peroxide throughout the process; after the online particle size analyzer detects that D50 has dropped to the minimum value (approximately 1.30μm), maintain the above conditions for another 5 hours to ensure sufficient and uniform number of crystal nuclei.

[0027] Step 2, pH surge and dense nucleus formation period: After the stable nucleation in Step 1, the flow rate of sodium hydroxide is rapidly increased within 1 hour, causing the pH of the system to rise rapidly from 12.0 to 12.5 (an increase of 0.5), and the reaction is continued at pH=12.5±0.05 for another hour. In this high supersaturation stage, the primary particles are densely packed in a fine sheet-like manner under the strong nucleation drive, forming a compact secondary spherical nucleus. During this stage, nitrogen gas is continued to be introduced for protection, and hydrogen peroxide is not introduced.

[0028] Step 3, Segmented Oxidation Shell Growth Period on an Ultra-Long Slope: Slowly decrease the pH from 12.5 to 11.3 at a rate of 0.10 pH units / h (approximately 12 hours); simultaneously start hydrogen peroxide feeding. The oxidation control strategy is as follows: In the initial stage (D50 < 1.8 μm, i.e., the stage where particles grow to less than 60% of the target particle size), the oxidation degree is controlled at 3%–10%; in the later stage (1.8 μm ≤ D50 to the nitrogen switching node), the oxidation degree is increased to 5%–20%, making the primary shell particles have a thin, sheet-like morphology to prevent the primary particles from gradually accumulating and thickening; the feed flow rate is slowly increased at a rate of 15% per hour, with the final hourly feed rate being 6% of the effective volume; after the particle size D50 > 2.0 μm, the stirring speed is reduced to 600 r / min, and the stirring speed is reduced by 100 r / min for every 0.5 μm increase in D50 thereafter; based on the particle size growth trend (hourly growth rate), it is estimated that the target D50 is 3.0 μm away. When it takes about 10 hours for the slurry to reach a diameter of 3.0 μm, immediately stop feeding hydrogen peroxide and switch to pure nitrogen protection (500 mL / min) to eliminate residual oxidizing activity and stabilize the morphology of the formed thin-film primary particles; continue feeding until D50 = 3.0 μm and then stop, and let the slurry age for 1 hour under nitrogen protection.

[0029] Step 4, Post-processing: The slurry is washed twice with a 2 mol / L sodium hydroxide solution and twice with water at 80℃. After filtration, it is dried at 100℃ for 12 hours to obtain the finished product of ultra-high tap density small particle manganese-rich precursor (denoted as E1).

[0030] Physicochemical performance testing: The precursor product was tested to have a particle size D50 of 2.48 μm and a specific surface area of ​​38.15 m². 2 / g, tap density is 1.58g / cm³ 3 The morphological characterization image is shown in the SEM image. Figure 1a , Figure 1b and Figure 1c The images show the dense core, dense primary particle packing, and secondary particle sphericity. It is evident that the dense packing of the precursor core promotes the dense primary particle packing of the finished product, while the secondary particle sphericity is good at low magnification.

[0031] Example 2 Composition ratio: Ni:Mn=45:55, target D50=2.8μm.

[0032] The process was carried out according to the steps described above, with the basic conditions the same as in Example 1. The difference from Example 1 was that the raw materials were adjusted to a Ni:Mn molar ratio of 45:55; in step 1, the pH was 12.10, and the pH was stabilized for 5 hours; in step 2, the pH was suddenly increased to 12.6 (an increase of 0.5) and maintained for 0.5 hours; in step 3, the pH was gradually decreased from 12.6 to 11.4 (at a rate of 0.08 pH / h, with a total duration of approximately 15 hours), with an initial oxidation degree of 5% and a subsequent oxidation degree of 10%. Nitrogen was switched when it was estimated that 10 hours were needed to reach the target D50 = 2.8 μm; the target D50 = 2.8 μm.

[0033] Testing showed that the manganese-rich precursor prepared in Example 2 had a particle size D50 of 2.82 μm and a specific surface area of ​​26.64 m². 2 / g, tap density is 1.62g / cm³ 3 The morphological characterization image is shown in the SEM image. Figure 2a and Figure 2b The images show a dense core and a densely packed primary particle. The manganese-rich precursor core is densely packed and has a flaky morphology, while the finished primary particles are densely packed in a thin flake shape.

[0034] Example 3 Composition ratio: Ni:Mn=25:75, adjust pH surge rate, target D50=3.2μm.

[0035] The process was carried out according to the steps described above, with the basic conditions the same as in Example 1. The difference from Example 1 was that the nickel-manganese ratio was adjusted to Ni:Mn=25:75; in step 1, the pH was 11.8, the rotation speed was 700 r / min, and the pH was stabilized for 4 h; in step 2, the pH increased by 0.4 (from 11.8 to 12.2) and was maintained for 1.5 h; in step 3, the pH gradually decreased from 12.2 to 11.0 (at a rate of 0.10 pH / h). Since the oxidation requirement of the high-Mn system was higher, the oxidation degree was 10% in the first stage and 20% in the second stage. Nitrogen gas was switched when it was 10 h away from the target D50=3.2 μm; the target D50=3.2 μm.

[0036] Testing showed that the manganese-rich precursor prepared in Example 3 had a particle size D50 of 3.15 μm and a specific surface area of ​​18.42 m². 2 / g, tap density is 1.69g / cm³ 3 The morphological characterization image is shown in the SEM image. Figure 3a and Figure 3b The images show a dense core and a densely packed primary particle. It can be seen that after adjusting the initial oxidation degree according to the manganese content, the manganese-rich precursor core is densely packed in a fine plate shape. Due to the relatively high manganese content, the primary particles of the finished product are thicker than those of Example 1 and Example 2 after restoring nitrogen protection, and they also exhibit a dense packing.

[0037] Example 4 Composition ratio: low Ni, high Mn, Ni:Co:Mn = 1:1:4, target D50 = 3.5μm.

[0038] The process was carried out according to the steps described above, with the basic conditions the same as in Example 1. The difference from Example 1 was that: the nickel-manganese ratio was adjusted to Ni:Co:Mn=1:1:4, and the mixed salt concentration was 1.8 mol / L; in step 1, the pH was 12.2, the rotation speed was 850 r / min, and the pH was stabilized for 6 h; in step 2, the pH suddenly increased to 12.7 (increase of 0.5) and was maintained for 2 h; in step 3, the pH gradually decreased from 12.7 to 11.0 (rate of 0.12 pH / h), with an oxidation degree of 8% in the first stage and 15% in the second stage; nitrogen was switched when 12 h was still needed to reach the target D50=3.5 μm; the target D50=3.5 μm.

[0039] Testing showed that the manganese-rich precursor prepared in Example 4 had a particle size D50 of 3.47 μm and a specific surface area of ​​15.12 m². 2 / g, tap density is 1.75g / cm³ 3 The morphological characterization image is shown in the SEM image. Figure 4a and Figure 4b The images show a dense core and a densely packed primary particle, respectively. It can be seen that the manganese-rich precursor core is densely packed in small plates, while the finished primary particles are densely packed.

[0040] Comparative Example 1 Scenario setting: pH surge step without step 2.

[0041] After nucleation stabilization in step 1, the process directly proceeds to step 3, the ultra-long slope segmented oxidation shell growth period, omitting the pH surge-induced dense core formation period in step 2; all other conditions are identical to those in Example 1. This comparative example is used to verify the crucial role of the settings in step 2 in the formation of a dense core and ultra-high TD.

[0042] Testing showed that the manganese-rich precursor prepared in Comparative Example 1 had a particle size D50 of 2.65 μm and a specific surface area of ​​38.23 m². 2 / g, tap density is 1.35g / cm³ 3 The morphological characterization image is shown in the SEM image. Figure 5a and Figure 5b The precursor core and the finished secondary particles are shown separately. SEM and physicochemical indicators show that, by omitting the pH surge process, the core did not form a dense packing, resulting in the final manganese-rich precursor secondary particles having larger openings on the surface and significantly lower tap density than the sample prepared in Example 1.

[0043] Comparative Example 2 Scenario setup: Constant pH throughout, no slope strategy.

[0044] In step 3, the pH was kept constant (without slow reduction), and the remaining staged oxidation strategy and final N2 protection were the same as in Example 1; all other conditions were identical to those in Example 1. This Comparative Example 2 was used to verify the effect of an ultra-long pH slope on particle size uniformity and TD.

[0045] Testing showed that the manganese-rich precursor prepared in Comparative Example 2 had a particle size D50 of 2.55 μm and a specific surface area of ​​34.03 m². 2 / g, tap density is 1.48g / cm³ 3 The morphological characterization image is shown in the SEM image. Figure 6a and Figure 6b The images show the secondary particles of the manganese-rich precursor product and their sphericity at low magnification. SEM and physicochemical indicators show that the secondary particles without a pH slope exhibit increased sphericity and poorer sphericity, ultimately affecting the tap density of the finished product, which is lower than that of the sample prepared in Example 1. Furthermore, the material is prone to powder formation after sintering.

[0046] Comparative Example 3 Scenario setting: Standard hydroxide process baseline.

[0047] No hydrogen peroxide was used throughout the process, and no sudden pH increase was performed. The pH was kept constant at 11.5. Growth was regulated by oxygen. All other conditions (temperature, rotation speed, and salt solution composition) were the same as in Example 1. The process was stopped when D50 reached 2.5 μm. This Comparative Example 3 can represent the existing conventional hydroxide coprecipitation process.

[0048] Testing showed that the manganese-rich precursor prepared in Comparative Example 3 had a particle size D50 of 2.52 μm and a specific surface area of ​​40.23 m². 2 / g, tap density is 1.28g / cm³ 3 The morphological characterization image is shown in the SEM image. Figure 7a and Figure 7b The images show the secondary particles of the precursor product and their sphericity at low magnification. Physicochemical indicators show that while the primary particles have a large specific surface area, their tap density is significantly lower than that of the sample prepared in Example 1. SEM microscopy reveals that although the primary particles have a uniform morphology, they have large openings, severe agglomeration, and are mostly spherical, resulting in poor sphericity.

[0049] The three-stage pH program control combined with segmented hydrogen peroxide controlled oxidation process of the present invention does not require organic complexing agents, has low equipment modification costs, allows for precise measurement of hydrogen peroxide and simple waste liquid treatment, and all raw materials are common industrial products, making it suitable for large-scale industrial production and of significant industrialization and promotion value.

Claims

1. A high-tapping, small-particle manganese-rich precursor, characterized in that: It includes a core and an outer shell. The core region consists of tightly packed, thin plates, which is called a primary particle dense packing structure. The outer shell region consists of tightly packed, thin plates, and the uniformly packed, thin plates form spherical or near-spherical secondary particles.

2. The ultra-high tapped small particle manganese-rich precursor according to claim 1, characterized in that: The chemical formula of the manganese-rich precursor is Ni a Mn b (OH)2, where a+b=1, 0.20≤a≤0.50, 0.50≤b≤0.80; Alternatively, the general chemical formula of the manganese-rich precursor is NixCoyMnzMw(OH)2, where x+y+z=1, 0.15≤x≤0.50, 0≤y≤0.20, 0.50≤z≤0.80, 0≤w≤0.10, and M is selected from at least one of Ti, Mg, Al, W, Mo, Nb, Zr, Y, P, B, F, Cl, and Br.

3. The ultra-high tapped small particle manganese-rich precursor according to claim 1, characterized in that: The particle size distribution of the manganese-rich precursor satisfies: (D90-D10) / D50≤0.65; The particle size D50 of the manganese-rich precursor satisfies: 2μm≤D50≤4μm; The tap density TD of the manganese-rich precursor satisfies: TD ≥ 1.5 g / cm³; The specific surface area (BET) of the manganese-rich precursor satisfies: 15 m² / g ≤ BET ≤ 40 m² / g.

4. A method for preparing ultra-high tapped small-particle manganese-rich precursors, characterized in that, Follow these steps: Step 1: Nucleation stabilization period, preparation of the reaction system; Step 2: During the pH surge and dense core formation period, a core structure is prepared, forming a primary particle core structure with fine, densely packed lamellar structures; Step 3: The ultra-long slope segmented oxidation shell growth period completes the morphological growth of the shell, and produces a manganese-rich precursor with ultra-high tap density small particles.

5. The method for preparing the ultra-high tapped small-particle manganese-rich precursor according to claim 4, characterized in that, In step 1, the specific process is as follows: 1.1) Prepare a mixed salt solution of nickel-manganese or nickel-cobalt-manganese using metal salts, and simultaneously prepare the bottom liquid of the reaction vessel; 1.2) The mixed salt solution, complexing agent and precipitant are added to the bottom liquid of the reaction vessel at the same time. Under the protection of an inert atmosphere, co-precipitation and nucleation are carried out at a pH of 11.5 to 12.

5. The mixture is stirred continuously until the particle size D50 drops to the minimum value. The reaction is then stabilized for 3 to 6 hours to obtain the reaction system.

6. The method for preparing the ultra-high tapped small particle manganese-rich precursor according to claim 5, characterized in that, In step 1.1), the nickel salt is selected from at least one of nickel sulfate, nickel chloride, and nickel nitrate; The manganese salt is selected from at least one of manganese sulfate, manganese chloride, and manganese nitrate. The cobalt salt is selected from at least one of cobalt sulfate, cobalt chloride, and cobalt nitrate; The molar ratio of nickel, manganese and / or cobalt salts in the mixed salt solution is adjusted according to the precursor chemical formula, and the total concentration of the mixed salt solution is 0.5–2.5 mol / L.

7. The method for preparing ultra-high tapped small-particle manganese-rich precursor according to claim 5, characterized in that, In step 1.1), the base solution is a mixed solution of deionized water and sodium hydroxide, with a pH of 11.5 to 12.5; the base solution occupies 50% to 70% of the effective volume of the reactor.

8. The method for preparing ultra-high tapped small-particle manganese-rich precursor according to claim 5, characterized in that, In step 1.2), an inorganic complexing agent is selected, and the ammonia concentration is 0.01–0.30 mol / L; The precipitant is selected from sodium hydroxide solution and / or potassium hydroxide solution, with a solution concentration of 5-15 mol / L; The stirring speed during the nucleation stage was 600–900 r / min, and the temperature was 40–70℃; the stabilization time after D50 dropped to its minimum value was 3–6 h.

9. The method for preparing the ultra-high tapped small-particle manganese-rich precursor according to claim 4, characterized in that, Step 2, the specific process is as follows: Continue processing in the reactor of step 1, rapidly increasing the pH of the reaction system by 0.3 to 0.8 units within 0.5 to 1.0 h, maintaining the reaction for 0.15 to 2 h, forming a primary particle core structure with fine, densely packed, plate-like particles.

10. The method for preparing the ultra-high tapped small-particle manganese-rich precursor according to claim 4, characterized in that, Step 3, the specific process is as follows: 3.1) Slowly decrease the pH at a rate of 0.05 to 0.20 pH units / h, while simultaneously introducing hydrogen peroxide and gradually increasing the hydrogen peroxide feed rate to form a gradient distribution of oxidation degree that gradually increases from the inside to the outside. 3.2) Reduce the stirring speed according to the growth particle size stage. The stirring speed range during the shell growth period is 400-600 r / min. Stop the hydrogen peroxide feeding 8-12 hours before the end of the reaction and switch to pure nitrogen protection until the end of the reaction to stabilize the final morphology. Stop feeding when D50 reaches the target particle size of 2-4 μm to obtain a manganese-rich precursor with ultra-high tap density small particles.

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