Battery-grade single-crystal manganous-manganic oxide and preparation method thereof

Abstract

The invention relates to the technical field of preparation of manganous-manganic oxide, and particularly discloses battery-grade single-crystal manganous-manganic oxide and a preparation method thereof.The Mn3O4 is a spheroidic tetragonal-phase single crystal, the manganese content is larger than or equal to 75%, the average particle size is 2-8 micrometers, the D50 deviation is smaller than or equal to 3%, the impurity content is extremely low (Fe, Si, Ni and Co are smaller than or equal to 3 ppm respectively, Na < + > and K < + > are smaller than or equal to 1 ppm respectively, and Cl <-> is smaller than or equal to 5 ppm), and the Mn3O4 is a battery-grade single-crystal manganous-manganic oxide. The preparation method comprises the following steps: adopting an agar hydrogel film containing fluorine ions as an ion transmission template, stabilizing ion transmission through a three-chamber groove structure, controlling the transmission rate of Mn < 2 + > and Al < 3 + > to be 0.08-0.3 mol / (L.h), reacting with oxygen under the conditions that the temperature is 90-150 DEG C and the pH value is 7.5-9.0, and combining with multi-stage post-treatment to obtain a high-purity single crystal product. The appearance of the single crystal is irregular, the particle size distribution is wide, and the uniformity is poor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of preparation of trimanganese tetraoxide, and specifically discloses a battery-grade single-crystal trimanganese tetraoxide and a preparation method thereof. BACKGROUND

[0002] As a key precursor of lithium ion battery cathode materials, the single-crystal form of trimanganese tetraoxide has no grain boundary resistance and excellent structural stability, and thus becomes a core raw material for high-capacity and long-cycle batteries. In the existing preparation technology, electrolytic manganese oxide method is widely used because raw materials are easy to obtain, but the following core problems exist.

[0003] 1. The diffusion rate of divalent manganese ions (Mn 2+ ) is uneven in the oxidation reaction, leading to disordered crystal nucleation and easy formation of agglomerates or irregular polyhedrons;

[0004] 2. The crystal face orientation is difficult to control in the single-crystal growth process, and the morphology consistency is poor (such as spindle-shaped and flaky mixed);

[0005] 3. Oxygen vacancies and lattice distortions are easily generated in the crystal, affecting the lithium ion migration efficiency;

[0006] 4. The particle size distribution is wide (D50 deviation is usually > 15%), which cannot meet the strict requirements of power batteries on the uniformity of raw materials.

[0007] Although ion exchange membrane technology can regulate ion transmission, traditional organic membranes have problems such as poor flexibility and insufficient ion selectivity; surfactant-assisted crystallization can improve the morphology, but the directional growth mechanism is not clear; element doping can optimize the crystal structure, but the synergistic effect of multiple elements is not well studied. Therefore, developing a synergistic technology system integrating ion transmission regulation, directional growth induction and multiple element doping is the key to preparing battery-grade single-crystal Mn3O4 with high performance. SUMMARY

[0008] The present application aims to solve the problems of irregular morphology, wide particle size distribution and insufficient structural stability of battery-grade single-crystal Mn3O4 in the prior art, and provides a preparation method based on ion transmission control of agar hydrogel template, directional induction of sodium dodecylbenzenesulfonate (SDBS) and synergistic doping of aluminum and fluorine ions, to realize precise regulation of the morphology, particle size and performance of single-crystal Mn3O4.

[0009] To achieve the above-mentioned purpose, the basic scheme of the present application provides a battery-grade single-crystal trimanganese tetraoxide, wherein the manganese content in the trimanganese tetraoxide is ≥75%, the average particle size is 2-8 μm, the particle size distribution D50 deviation is ≤3%, the content of Fe, Si, Ni and Co is ≤3 ppm respectively, the content of Na + , K +each content ≤1 ppm, Cl- content ≤5 ppm, the trimanganese tetraoxide is spherical tetragonal phase single crystal.

[0010] Further, the battery grade trimanganese tetraoxide single crystal preparation method comprises the following steps:

[0011] 1) preparing an electrolytic manganese-based solution containing Mn 2+ and Al 3+ ;

[0012] 2) preparing an agar hydrogel membrane containing fluoride ions as an ion transmission template;

[0013] 3) setting a three-chamber tank structure comprising a raw material chamber, a buffer chamber and a reaction chamber, and separating the raw material chamber, the buffer chamber and the reaction chamber by the agar hydrogel membrane;

[0014] 4) adding sodium dodecyl benzene sulfonate into the reaction chamber, and controlling the transmission rate of Mn 2+ and Al 3+ through the agar hydrogel membrane to be 0.08-0.3 mol / (L·h), and reacting with oxygen at 90-150℃ and pH 7.5-9.0;

[0015] 5) obtaining the battery grade trimanganese tetraoxide single crystal through post-processing.

[0016] Further, the step 1 of preparing the electrolytic manganese-based solution containing Mn 2+ and Al 3+ comprises:

[0017] a. adding electrolytic manganese pieces into a dilute sulfuric acid solution (concentration 1.0-3.0 mol / L), controlling the liquid-solid ratio to be 8-12:1 (v / w), and stirring at 40-60℃ until completely dissolved, and the stirring rate is 200-400 rpm;

[0018] b. adding 0.01-0.05 mol / L aluminum sulfate (Al2(SO4)3) as an aluminum source into the above solution, and continuing to stir for 30-60 min;

[0019] c. removing Fe 3+ , Ni 2+ , Co 2 + heavy metal impurities through ceramic fiber membrane microfiltration and chelating resin column adsorption (flow rate 1-3 BV / h) in sequence, to obtain a mixed base solution containing Mn 2+ (1.5-4.0 mol / L) and Al 3+ (0.005-0.02 mol / L); 3 + , Ni 2+ , Co 2+each content ≤0.5ppm.

[0020] Further, the agar and water mass ratio of the agar hydrogel film in step 2 is 1:20-1:50, containing 0.5-2.0wt% sodium fluoride, the thickness is 0.3-1.0mm, and the ion exchange capacity is 0.8-1.5mmol / g.

[0021] Further, the concentration of sodium dodecyl benzene sulfonate in step 4 is 0.02-0.1g / L, the oxygen flow is 1.0-3.0L / min, and the reaction time is 4-10h.

[0022] Further, the chelating resin in step 2 is an aminophosphonic acid type resin, and the column height-diameter ratio is 8-12:1, and the adsorption temperature is 25-40℃.

[0023] Further, the raw material chamber is used to store the mixed base solution prepared in step 1, and the buffer chamber stores a 0.1-0.5mol / L sulfuric acid solution;

[0024] Further, the post-treatment includes:

[0025] a. centrifugal separation: centrifugal separation of the reaction chamber base solution at a speed of 8000-12000rpm for 10-20min, and collecting the bottom solid particles;

[0026] b. multi-stage washing:

[0027] ① first ultrasonic washing with deionized water for 3-4 times, and centrifuging at 8000rpm for 10min after each washing;

[0028] ② then washing with anhydrous ethanol for 2 times, and centrifuging at 8000rpm for 10min after each washing;

[0029] c. vacuum drying: placing the washed solid in a vacuum drying oven, drying at a vacuum degree of ≤-0.09MPa and a temperature of 100-140℃ for 8-16h;

[0030] d. gradient calcination: placing the dried powder in an atmosphere furnace, passing high-purity nitrogen gas for protection, heating at a rate of 5-10℃ / min to 300-500℃, and keeping the temperature for 2-4h, and then naturally cooling to room temperature.

[0031] The principle and effect of the basic scheme are:

[0032] 1. Breakthrough in morphology and particle size uniformity

[0033] The agar hydrogel template precisely regulates Mn 2+Transmission rate (0.08-0.3 mol / (L·h)), combined with the selective adsorption of SDBS on the (112) crystal plane, induces the growth of single crystals along a specific direction, achieving a high consistency of spherical morphology, and reducing the particle size distribution D50 deviation from the prior art by >15% to ≤3%.

[0034] 2. Significant improvement in structural stability

[0035] Aluminum ions (Al 3+ ) replace Mn 3+ in the lattice to form a stable solid solution, and fluorine ions (F-) fill oxygen vacancies, both of which synergistically improve the integrity of the crystal structure by more than 40%, and the capacity retention rate is increased by 15%-20% after 500 charge-discharge cycles.

[0036] 3. Strong controllability of the process

[0037] By adjusting the agar hydrogel concentration and pressure difference, the ion transmission rate can be accurately controlled, and the particle size can be precisely regulated by combining online particle size monitoring, which is suitable for industrial large-scale production.

[0038] 4. Extremely low impurity content

[0039] The agar hydrogel has a retention rate of >99.5% for impurity ions such as Fe 3+ , Si 4+ , etc., and combined with a multi-stage washing process, the total impurity content of the product is ≤10 ppm, meeting the ultra-high purity requirements of the positive electrode material of the power battery. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0041] Figure 1 The overall schematic diagram of a battery-grade single-crystal trimanganese tetraoxide and its preparation method according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0042] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following will describe the specific embodiments, structures, features and effects according to the present application in detail with reference to the drawings and preferred embodiments.

[0043] A battery-grade single-crystal trimanganese tetraoxide and its preparation method, embodiment 1 is shown in the figure:

[0044] 1. Raw material preparation

[0045] Electrolytic manganese metal flake: purity≥99.95%(Mn content≥99.95%, Fe≤0.01%, Si≤0.005%), size 50mm x 30mm x 2mm flake, soaked in 10% dilute hydrochloric acid for 5min to remove surface oxide layer before use, washed with deionized water to neutral, vacuum dried for standby;

[0046] Dilute sulfuric acid: diluted to 2.0mol / L with deionized water (conductivity≤1μS / cm), ice bath temperature control (≤30℃) was used during dilution to avoid local overheating;

[0047] Aluminum sulfate: prepared into 0.03mol / L aqueous solution, filtered through 0.22μm polyether sulfone membrane before use;

[0048] Amino phosphonic acid type chelating resin: type D418, particle size 0.3-1.2mm, activated with 4% hydrochloric acid for 2h and eluted with 4% sodium hydroxide for 2h before use, washed with deionized water to neutral pH;

[0049] Sodium fluoride;

[0050] Agar: biological reagent grade (freezing point 36-38℃);

[0051] Sodium dodecylbenzenesulfonate: prepared into 0.1g / L stock solution, prepared and used immediately;

[0052] Oxygen: impurities removed by 0.01μm precision filter;

[0053] High-purity nitrogen: oxygen content≤1ppm.

[0054] 2. Preparation of electrolytic manganese-based solution (equipment: 5L double-layer glass reaction kettle with mechanical stirring, temperature control system)

[0055] a. 3L of 2.0mol / L dilute sulfuric acid was added to the reaction kettle, stirring was started (300rpm), and 300g of pretreated electrolytic manganese metal flake (liquid-solid ratio 10:1 v / w) was slowly added, the temperature was raised to 50℃, and stirring was continued for 4h until the manganese flake was completely dissolved (sample detection showed no solid residue, and the solution was clear);

[0056] b. The temperature was maintained at 50℃ and the stirring speed was 300rpm, 100mL of 0.03mol / L aluminum sulfate solution was added to the reaction kettle at a uniform speed (dropping rate 5mL / min), and after the addition was completed, stirring was continued for 45min to form a uniform mixture;

[0057] c. The mixed solution was first micro-filtered through a 0.22 pm ceramic fiber membrane (operating pressure 0.2 MPa, flow rate 1 L / min) to remove suspended impurities, and then passed into an amino phosphonic acid type chelating resin column (column specifications Φ 50 mm x 500 mm, height-diameter ratio 10:1, resin loading 1 L) at a flow rate of 2 BV / h (2 L / h) and a column temperature of 30 °C. After adsorption treatment, the sample was detected: Fe 3+ = 0.2 ppm, Ni 2 += 0.1 ppm, Co 2+ = 0.1 ppm, obtaining a mixed base solution containing 3.0 mol / L Mn 2+ , 0.01 mol / L Al 3+ , which was stored in a 5 L sealed polyethylene storage tank under nitrogen protection to prevent oxidation.

[0058] 3. Agar hydrogel membrane preparation (equipment: constant temperature drying oven, stainless steel mold)

[0059] a. 10 g of agar and 300 g of deionized water (mass ratio 1 :30) were weighed into a 250 mL beaker and heated to 95 °C with stirring until the agar was completely dissolved (stirring rate 150 rpm, dissolution time 20 min);

[0060] b. 3 g of sodium fluoride (1.0 wt%, relative to the total mass of the solution) was added to the agar solution, and stirring was continued for 10 min until the sodium fluoride was completely dissolved, forming a uniform membrane solution;

[0061] c. The membrane solution was poured into a stainless steel mold (specifications 200 mm x 100 mm x 0.5 mm), and left to stand at room temperature for 30 min for preliminary coagulation, then placed in a constant temperature drying oven at 40 °C for 2 h. After removal from the oven, the mold was peeled off to obtain an agar hydrogel membrane with a thickness of 0.5 mm. Sample detection: ion exchange capacity 1.2 mmol / g (potentiometric titration method), fluoride ion elution ≤0.01 mg / L (ion chromatography method).

[0062] 4. Three-compartment tank reaction (equipment: custom three-compartment reaction tank, material 316L stainless steel, single compartment volume 2 L; internal temperature control system, gas flow meter, pH online monitor)

[0063] a. Assemble the three-compartment tank: install the agar hydrogel membranes prepared in step 3 between the raw material compartment and the buffer compartment, and between the buffer compartment and the reaction compartment, seal to ensure no liquid leakage; the raw material compartment is maintained by stirring to ensure uniform composition of the base solution, continuously providing Mn 2+ and Al 3+ sources for the system; the buffer compartment is used to eliminate the direct concentration difference impact between the raw material compartment and the reaction compartment, stabilize the ion transport driving force, and further trap trace impurities that are not completely filtered by the agar hydrogel membrane.

[0064] b. Add 2L of mixed base liquid to the raw material chamber and turn on magnetic stirring (200rpm) to maintain the homogeneity of the components; add 2L of 0.3mol / L sulfuric acid solution to the buffer chamber; add 1.9L of deionized water to the reaction chamber, turn on stirring (150rpm), and add 100mL of 0.05g / L sodium dodecylbenzenesulfonate solution (final concentration 0.05g / L).

[0065] c. Turn on the temperature control system and raise the temperature of the reaction chamber to 120℃. Add 0.1mol / L sodium hydroxide solution dropwise through the pH online monitor to adjust the pH to 8.0 and maintain it. Turn on the oxygen valve and control the oxygen flow rate to 2.0L / min through the gas flow meter to introduce oxygen into the reaction chamber (the aeration head is placed at the bottom of the tank with an orifice diameter of 0.5mm).

[0066] d. During the reaction process, the concentration of Mn in the reaction chamber was monitored in real time using an inductively coupled plasma optical emission spectrometer (ICP-OES). 2+ Concentration and ion transport rate calculation: Samples were taken every 30 minutes for the first 2 hours, and every hour thereafter. Mn concentration was maintained by adjusting the stirring speed in the feed chamber (180-220 rpm). 2+ And Al 3+ The transport rate was stabilized at 0.2 mol / (L·h), and the total reaction time was 6 h.

[0067] 5. Post-processing (equipment includes: high-speed centrifuge, ultrasonic cleaner, vacuum drying oven, and programmed temperature atmosphere furnace)

[0068] a. Centrifugation: Transfer the mixture from the reaction chamber to a 500mL centrifuge tube, place it in a high-speed centrifuge (model GL-21M), set the speed to 10000rpm and the time to 15min. After centrifugation, discard the supernatant and collect the black solid particles at the bottom (wet basis moisture content of about 60%).

[0069] b. Multi-stage washing:

[0070] ① Ultrasonic washing with deionized water: Transfer the solid particles to a 250mL beaker, add 100mL of deionized water (conductivity 0.5μS / cm), place in an ultrasonic cleaner (model KQ-300VDE), set power to 250W, temperature to 40℃, sonicate for 15min, then centrifuge at 8000rpm for 10min, discard the supernatant; repeat this operation 4 times, and test the supernatant after the last wash: Na + =0.3ppm, K + =0.2ppm, Cl- =1.5ppm;

[0071] ② Washing with anhydrous ethanol: Add 100 mL of anhydrous ethanol (99.95% purity) to the solid, stir for 10 min, centrifuge at 8000 rpm for 10 min, and discard the supernatant; repeat this operation twice to remove residual water;

[0072] c. Vacuum drying: The washed solid was transferred to a ceramic tray and placed in a vacuum drying oven (Model DZF-6050) at a vacuum degree of -0.095 MPa and a temperature of 120°C for 12 h. The volatile components were discharged every 4 h. The water content of the dried powder was ≤0.1%;

[0073] d. Gradient calcination: The dried powder was transferred to a corundum crucible (loading capacity 200 g) and placed in a programmed temperature atmosphere furnace (Model GSL-1700X). High-purity nitrogen gas was introduced to replace the air in the furnace for 30 min. Then the temperature was raised to 400°C at a rate of 8°C / min, and the temperature was maintained for 3 h (the oxygen content in the furnace was detected every 1 h during the holding period to ensure that it was ≤10 ppm). After the holding period ended, the heating was turned off, and the nitrogen gas was continued to be introduced until the furnace temperature dropped to room temperature. The powder was removed.

[0074] 6. Product testing and performance verification

[0075] Physicochemical indicators: X-ray fluorescence spectrometer (XRF) detection: Mn content 75.8%, Fe = 2.1 ppm, Si = 2.3 ppm, Ni = 1.8 ppm, Co = 1.5 ppm; ion chromatograph detection: Na+ = 0.6 ppm, K - = 0.5 ppm, Cl- = 3.2 ppm; Laser particle size analyzer (Model Mastersizer 3000) detection: average particle size 5 μm, D10 = 3.8 μm, D50 = 5.0 μm, D90 = 6.2 μm, D50 deviation 2.2%; X-ray diffractometer (XRD) detection: the characteristic peaks completely matched the standard card of tetragonal Mn3O4 (JCPDS No. 24-0734), no impurity peaks, and the grain size was 25 nm (calculated by the Scherrer formula); scanning electron microscope (SEM) observation: the particles were spherical, the surface was smooth, there was no agglomeration, and the particle size was uniform.

[0076] Electrochemical performance verification: The product was mixed with Li2CO3 in a stoichiometric ratio, 5% carbon black and 3% PVDF were added, NMP was used as the solvent, and a positive electrode slurry was prepared. The slurry was coated on an aluminum foil (areal density 15 mg / cm 2 ), and a metal lithium negative electrode, Celgard 2400 separator, and 1 mol / L LiPF6 / EC+DMC (1:1) electrolyte were assembled into a button cell (CR2032);

[0077] Blue cell test system detection: the first discharge capacity was 128 mAh / g at 0.1C rate, and the capacity retention rate was 92% after 500 cycles at 1C rate, which was better than that of the commercially available polycrystalline trimanganese tetroxide (the capacity retention rate was 85% after 500 cycles).

[0078] Example 2

[0079] 1. Raw material adjustment

[0080] Dilute sulfuric acid concentration 1.5 mol / L, electrolytic manganese piece dosage 240 g (liquid-solid ratio 8:1 v / w);

[0081] Aluminum sulfate concentration 0.02 mol / L, dropwise addition amount 80 mL;

[0082] Chelating resin column specification Φ40 mm x 320 mm (height-diameter ratio 8:1), flow rate 1.5 BV / h, column temperature 25℃;

[0083] Agar to water mass ratio 1:25, sodium fluoride addition amount 0.8 wt%, film thickness 0.4 mm;

[0084] Sodium dodecyl benzene sulfonate final concentration 0.04 g / L, oxygen flow rate 1.5 L / min, reaction temperature 100℃, pH 7.8.

[0085] 2. Key operation differences

[0086] Electrolytic manganese base liquid preparation: stirring rate 250 rpm, aluminum sulfate dropwise addition rate 4 mL / min, stirring time 30 min; Chelation detection: Fe 3- = 0.3 ppm, Ni 2- = 0.2 ppm, Co 2- = 0.2 ppm, Mn 2- concentration 2.0 mol / L, Al 3+ concentration 0.008 mol / L;

[0087] Agar hydrogel film: drying temperature 38℃, drying time 1.5 h, ion exchange capacity 1.0 mmol / g;

[0088] Three-compartment tank reaction: ion transport rate control 0.15 mol / (L·h), reaction time 8 h, pH adjustment using 0.05 mol / L sodium hydroxide solution, dropwise addition rate 3 mL / min;

[0089] Post-treatment: centrifugal speed 9000 rpm, time 18 min; ultrasonic washing power 220 W, temperature 35℃, washing 3 times; vacuum drying temperature 110℃, time 14 h; gradient calcination heating rate 6℃ / min, final temperature 350℃, holding for 4 h.

[0090] 3. Product test results

[0091] Physicochemical indexes: Mn content 75.2%, average particle size 3um (D10=2.5um, D50=3.0um, D90=3.5um, D50 deviation 2.8%); impurity content: Fe=2.5ppm, Si=2.8ppm, Ni=2.0ppm, Co=1.8ppm, Na + =0.8ppm, K + =0.7ppm, Cl- =4.0ppm; XRD verification is pure tetragonal phase single crystal, SEM shows that the particles are spherical and have good dispersibility;

[0092] Electrochemical performance: 0.1C initial discharge capacity 125mAh / g, 1C cycle 500 times capacity retention rate 90%, meeting the requirements of high-performance lithium ion battery positive electrode material.

[0093] The application has the following advantages:

[0094] Three-chamber buffer ion transmission system

[0095] Traditional method: direct reaction → ion concentration fluctuation leads to twin crystal growth

[0096] The application: raw material chamber → buffer chamber (H2SO4 solution) → reaction chamber → transmission rate is stable within ±5%

[0097] Fluorinated agar membrane bifunctional design

[0098] Template function: F — and Mn 2+ form [MnF6] 4- ligand → induce tetragonal phase nucleation

[0099] Impurity removal function: SO4 2- group adsorbs residual Ca 2+ / Mg 2+ → reduce impurities by more than 30%

[0100] Gradient dechlorination process

[0101] Water washing removes surface Cl- + ethanol dehydration prevents agglomeration + low-temperature calcination removes lattice Cl- → Cl- residual ≤5ppm, solving the problems of irregular morphology, wide particle size distribution and insufficient structural stability of battery-grade single crystal Mn3O4 in the prior art.

[0102] The above merely describes the preferred embodiments of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed with the preferred embodiments as above, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, as long as the changes or modifications do not deviate from the technical solution of the present application. Any modification, change, equivalent change and modification of the above embodiments made according to the technical essence of the present application still belong to the scope of the technical solution of the present application.

Claims

1. A battery-grade single-crystal manganese tetroxide, characterized in that, The manganese tetroxide contains ≥75% manganese, with an average particle size of 2-8 μm and a particle size distribution D50 deviation ≤3%; the contents of Fe, Si, Ni, and Co are each ≤3 ppm, and Na... + K + Each of the following contents is ≤1ppm, and the Cl- content is ≤5ppm. The manganese tetroxide is a near-spherical tetragonal single crystal.

2. A method for preparing battery-grade single-crystal manganese tetroxide, characterized in that, Includes the following steps: 1) Preparation of Mn-containing 2+ And Al 3+ Electrolytic manganese-based solution; 2) Prepare fluoride-containing agar hydrogel membranes as ion transport templates; 3) A three-chamber tank structure including a raw material chamber, a buffer chamber, and a reaction chamber is set up, and the raw material chamber, the buffer chamber, and the reaction chamber are separated by an agar hydrogel membrane; 4) Add sodium dodecylbenzenesulfonate to the reaction chamber to control Mn 2+ And Al 3+ The transport rate through the agar hydrogel membrane is 0.08-0.3 mol / (L·h), and it reacts with oxygen under conditions of 90-150℃ and pH 7.5-9.

0. 5) Battery-grade single-crystal manganese tetroxide is obtained through post-processing.

3. The method for preparing battery-grade single-crystal manganese tetroxide according to claim 2, characterized in that, In step 1, Mn-containing preparations are made 2+ And Al 3+ Electrolytic manganese-based solutions include: a: Add electrolytic manganese metal sheets to dilute sulfuric acid solution (concentration 1.0-3.0 mol / L), control the liquid-solid ratio at 8-12:1 (v / w), and stir at 40-60℃ until completely dissolved at a stirring speed of 200-400 rpm; b: Add 0.01-0.05 mol / L aluminum sulfate (Al2(SO4)3) to the above solution as an aluminum source, and continue stirring for 30-60 min; c: Fe is removed by sequentially passing the material through a ceramic fiber membrane microfiltration and chelating resin column adsorption (flow rate 1-3 BV / h). 3+ Ni 2 +、Co 2+ Metallic impurities, yielding Mn-containing 2+ (1.5-4.0 mol / L) and Al 3+ A mixed base solution of (0.005-0.02 mol / L), in which Fe 3- Ni 2+ Co 2+ Each content is ≤0.5ppm.

4. The method for preparing battery-grade single-crystal manganese tetroxide according to claim 2, characterized in that, In step 2, the agar hydrogel membrane has an agar-to-water mass ratio of 1:20-1:50, contains 0.5-2.0 wt% sodium fluoride, has a thickness of 0.3-1.0 mm, and an ion exchange capacity of 0.8-1.5 mmol / g.

5. The method for preparing battery-grade single-crystal manganese tetroxide according to claim 2, characterized in that, In step 4, the concentration of sodium dodecylbenzenesulfonate is 0.02-0.1 g / L, the oxygen flow rate is 1.0-3.0 L / min, and the reaction time is 4-10 h.

6. The method for preparing battery-grade single-crystal manganese tetroxide according to claim 2, characterized in that, In step 2, the chelating resin is an aminophosphonic acid type resin with a column height-to-diameter ratio of 8-12:1 and an adsorption temperature of 25-40℃.

7. The method for preparing battery-grade single-crystal manganese tetroxide according to claim 2, characterized in that, The raw material chamber is used to store the mixed base liquid prepared in step 1, and the buffer chamber stores a sulfuric acid solution of 0.1 to 0.5 mol / L.

8. The method for preparing battery-grade single-crystal manganese tetroxide according to claim 2, characterized in that, The post-processing includes: a. Centrifugal separation: Centrifuge the base liquid in the reaction chamber at 8000-12000 rpm for 10-20 min and collect the solid particles at the bottom; b. Multi-stage washing: ① First, ultrasonically wash with deionized water 3-4 times, centrifuging for 10 minutes after each wash; ② Wash twice with anhydrous ethanol, centrifuging for 10 minutes after each wash; c. Vacuum drying: Place the washed solid in a vacuum drying oven and dry it for 8 to 16 hours at a vacuum degree ≤ -0.09 MPa and a temperature of 100-140℃. d. Gradient calcination: Place the dried powder in an atmosphere furnace, introduce high-purity nitrogen for protection, heat to 300-500℃ at a rate of 5-10℃ / min, hold for 2-4 hours, and then cool naturally to room temperature.

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