Method for producing electrolytic manganese dioxide for battery with improved discharge performance

Abstract

The application relates to the technical field of manganese dioxide production, and discloses a production method of electrolytic manganese dioxide for batteries with improved discharging performance, which comprises a raw material processing procedure, an electrolysis processing procedure and a finished product processing procedure. The production method of electrolytic manganese dioxide for batteries with improved discharging performance reduces harmful impurities in the electrolyte to an extremely low level (Fe<=1 ppm, heavy metal<=0.1 ppm) through multistage chemical impurity removal and precision filtration, avoids the catalytic decomposition and self-discharge phenomenon caused by impurity elements in the discharging process from the source, and significantly improves the storage performance and discharging capacity of the battery; pulse current is used to replace the traditional direct current electrolysis, combined with ultrasonic assistance and electrochemical oscillation, so that the deposited manganese dioxide crystals are more compact and have fewer defects, which is helpful to form nanorod or fibrous structures, and increases the specific surface area and electrochemical active sites of the material.

Description

Technical Field

[0001] This invention relates to the field of manganese dioxide production technology, specifically to a method for producing electrolytic manganese dioxide for batteries with improved discharge performance. Background Technology

[0002] Electrolytic manganese dioxide (EMD) is widely used as the positive electrode active material in high-performance chemical batteries, especially lithium-manganese batteries and alkaline manganese batteries, due to its advantages such as high chemical purity, good crystal form (mainly γ-type), reasonable solid-phase surface properties, and good cathode forming characteristics. With the increasing demands on battery performance from IoT devices, digital products, and new energy vehicles, the market is placing higher requirements on the discharge capacity, high-rate discharge performance, and low-temperature discharge performance of EMD.

[0003] Currently, the entire production process of electrolytic manganese dioxide typically includes three main stages: electrolyte preparation, electrolysis, and finished product processing. In existing production technologies, during the raw material processing stage, traditional leaching purification processes are used to remove impurities (such as K⁺, Na⁺, Fe⁺) from the electrolyte. 2+ The control of impurities (such as heavy metals) is not precise enough, and residual impurities can cause side reactions during discharge, reducing battery capacity and storage performance; conventional purification processes have limited efficiency in removing impurities such as calcium and magnesium, making it difficult to meet the purity requirements of raw materials for high-performance batteries.

[0004] Traditional electrolysis processes employ a constant current and temperature mode, resulting in a single crystal form (mostly γ-type). Furthermore, internal stress and twinning defects are easily generated during crystal growth, affecting the migration rate of protons / lithium ions. While low current densities (60-80 A / m²) produce better quality, they result in lower per-cell output, limiting the annual production capacity of electrolytic manganese dioxide.

[0005] Therefore, there is an urgent need for a method to produce electrolytic manganese dioxide for batteries that improves discharge performance, in order to solve the problem of insufficient manganese dioxide purity leading to reduced battery discharge performance. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention provides a method for producing electrolytic manganese dioxide for batteries that improves discharge performance. This method has the advantage of increasing the purity of manganese dioxide and solves the problem of reduced battery discharge performance caused by insufficient manganese dioxide purity.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for producing electrolytic manganese dioxide for batteries with improved discharge performance, comprising the following steps:

[0010] (a) Raw material processing procedures, including:

[0011] (1) Reduction roasting: Mix pyrolusite powder and reducing agent at a mass ratio of 100:(8-15) and roast at 600-850℃ for 2-4 hours;

[0012] (2) Acid leaching reaction: The roasted clinker is leached with 15-25% sulfuric acid solution at 80-95℃ for 3-6 hours, and the final pH is controlled to be 3.0-4.0;

[0013] (3) Multi-stage deep purification: iron removal by oxidation, heavy metal removal by sulfidation, calcium and magnesium removal by fluorination, and precision filtration are performed in sequence;

[0014] (4) Temperature and concentration adjustment: Adjust Mn 2+ Concentration up to 37-50 g / L, H2SO4 concentration up to 30-41 g / L, temperature up to 92-98℃;

[0015] (ii) Electrolytic machining process, including:

[0016] (5) Electrolyte pretreatment: Control suspended particles, adjust MnSO4 concentration to 130-135 g / L, and H2SO4 concentration to 30-32 g / L;

[0017] (6) Pulse current electrolysis: pulse current density 40-80 A / m², pulse frequency 500-2000 Hz, pulse duty cycle 30%-70%, electrolysis temperature 92-98℃, electrolysis time 5-10 days;

[0018] (7) Ultrasonic-assisted electrolysis: Apply ultrasonic waves at a frequency of 20-40 kHz and a power density of 0.1-0.5 W / cm².

[0019] (8) In-situ doping: Add a doping modification solution containing at least one element among titanium, vanadium, bismuth and lithium to the anode area, with a total concentration of doping elements of 5-20 g / L and a dropping rate of 0.5-5 mL / (min·m²) anode;

[0020] (9) Stripping and collection: When the thickness of the sediment layer reaches 3-8 mm, stripping is performed to obtain crude electrolytic manganese dioxide;

[0021] (iii) Finished product processing steps, including:

[0022] (10) Coarse crushing: crush to a particle size ≤ 5 mm;

[0023] (11) Multi-stage countercurrent rinsing: Use hot water at 50-90℃ for multi-stage rinsing, including hot water washing for acid, weak alkali rinsing, strong alkali rinsing, and hot water washing for alkali;

[0024] (12) Neutralization and desulfurization: Add an alkaline neutralizing agent to adjust the pH to 6.5-7.5 and react for 1-2 hours;

[0025] (13) Oxidation treatment: Optional addition of oxidizing agent to eliminate reducing impurities;

[0026] (14) Phase control heat treatment: first stage: drying at 150-250℃ for 2-4 hours; second stage: holding at 300-400℃ for 4-8 hours; third stage: tempering at 200-250℃ for 2-3 hours (optional).

[0027] (15) Fine grinding and classification: Grind to a median particle size of 3-25 μm and pass through a 325 mesh sieve;

[0028] (16) Iron removal: Multi-stage iron removal using electromagnetic iron separator;

[0029] (17) Metered packaging: Packaging under vacuum or inert gas protection.

[0030] Preferably, the reducing agent in step (1) is pulverized coal or pyrite; when using pyrite, the roasting temperature is 600-700℃.

[0031] Preferably, in step (3), the oxidation to remove iron uses manganese dioxide ore powder or hydrogen peroxide as the oxidant, the reaction temperature is 80-90℃, and the amount of oxidant used is 1.08 times the theoretical amount; the sulfidation to remove heavy metals uses barium sulfide or SDD as the sulfiding agent, the amount added is 2g / L, the reaction temperature is 60℃, and the reaction time is 60min.

[0032] Preferably, the frequency of the pulse current in step (6) is 1000Hz and the current density is 50 A / m².

[0033] Preferably, in the doping modification liquid described in step (8), the doping of bismuth can suppress the disproportionation reaction and stabilize the crystal lattice.

[0034] Preferably, the multi-stage countercurrent rinsing in step (11) includes: washing with hot water at 85-90℃ until the sulfuric acid content is less than 0.5g / L, rinsing with weak alkali at 50-54℃ for 5-8 hours, and rinsing with strong alkali at 50-60℃ until pH 7.0.

[0035] Preferably, in step (14), the second heat treatment temperature is 380°C and the time is 6-8 hours.

[0036] Preferably, the electrolytic manganese dioxide has a mixed crystal form in which γ phase and β phase coexist, and the crystal lattice is uniformly doped with at least one element selected from titanium, vanadium, bismuth and lithium, with Fe content ≤100μg / g and water content <3%.

[0037] Compared with the prior art, the present invention provides a method for producing electrolytic manganese dioxide for batteries with improved discharge performance, which has the following beneficial effects:

[0038] 1. The battery electrolytic manganese dioxide production method that improves discharge performance reduces harmful impurities in the electrolyte to extremely low levels (Fe≤1ppm, heavy metals≤0.1ppm) through multi-stage chemical impurity removal and precision filtration. This avoids catalytic decomposition and self-discharge phenomena caused by impurity elements during discharge, significantly improving the battery's storage performance and discharge capacity.

[0039] 2. The battery electrolytic manganese dioxide production method that improves discharge performance uses pulsed current instead of traditional DC electrolysis, combined with ultrasonic assistance and electrochemical oscillation, to make the deposited manganese dioxide crystals more compact and less defective, which helps to form nanorod-like or fibrous structures, increasing the specific surface area and electrochemical active sites of the material. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the manganese dioxide electrolytic processing flow structure of the present invention;

[0041] Figure 2 This is a schematic diagram of the raw material processing steps of the present invention;

[0042] Figure 3 This is a schematic diagram of the electrolytic processing procedure of the present invention;

[0043] Figure 4 This is a schematic diagram of the structural flow of the finished product processing steps of the present invention. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Please see Figure 1-4 A method for producing electrolytic manganese dioxide for batteries with improved discharge performance includes the following steps:

[0046] (a) Raw material processing procedures, including:

[0047] (1) Reduction roasting: Mix pyrolusite powder and reducing agent at a mass ratio of 100:(8-15) and roast at 600-850℃ for 2-4 hours;

[0048] The reducing agent in step (1) is pulverized coal or pyrite; when using pyrite, the roasting temperature is 600-700℃.

[0049] (2) Acid leaching reaction: The roasted clinker is leached with 15-25% sulfuric acid solution at 80-95℃ for 3-6 hours, and the final pH is controlled to be 3.0-4.0;

[0050] (3) Multi-stage deep purification: iron removal by oxidation, heavy metal removal by sulfidation, calcium and magnesium removal by fluorination, and precision filtration are performed in sequence;

[0051] In step (3), the oxidation to remove iron uses manganese dioxide ore powder or hydrogen peroxide as the oxidant, the reaction temperature is 80-90℃, and the amount of oxidant used is 1.08 times the theoretical amount; the sulfidation to remove heavy metals uses barium sulfide or SDD as the sulfiding agent, the amount added is 2g / L, the reaction temperature is 60℃, and the reaction time is 60min.

[0052] (4) Temperature and concentration adjustment: Adjust Mn 2+ Concentration up to 37-50 g / L, H2SO4 concentration up to 30-41 g / L, temperature up to 92-98℃;

[0053] (ii) Electrolytic machining process, including:

[0054] (5) Electrolyte pretreatment: Control suspended particles, adjust MnSO4 concentration to 130-135 g / L, and H2SO4 concentration to 30-32 g / L;

[0055] (6) Pulse current electrolysis: pulse current density 40-80 A / m², pulse frequency 500-2000 Hz, pulse duty cycle 30%-70%, electrolysis temperature 92-98℃, electrolysis time 5-10 days;

[0056] The frequency of the pulse current in step (6) is 1000Hz and the current density is 50 A / m².

[0057] (7) Ultrasonic-assisted electrolysis: Apply ultrasonic waves at a frequency of 20-40 kHz and a power density of 0.1-0.5 W / cm².

[0058] (8) In-situ doping: Add a doping modification solution containing at least one element among titanium, vanadium, bismuth and lithium to the anode area, with a total concentration of doping elements of 5-20 g / L and a dropping rate of 0.5-5 mL / (min·m²) anode;

[0059] In the doping modification liquid described in step (8), the doping of bismuth can suppress the disproportionation reaction and stabilize the crystal lattice;

[0060] (9) Stripping and collection: When the thickness of the sediment layer reaches 3-8 mm, stripping is performed to obtain crude electrolytic manganese dioxide;

[0061] (iii) Finished product processing steps, including:

[0062] (10) Coarse crushing: crush to a particle size ≤ 5 mm;

[0063] (11) Multi-stage countercurrent rinsing: Use hot water at 50-90℃ for multi-stage rinsing, including hot water washing for acid, weak alkali rinsing, strong alkali rinsing, and hot water washing for alkali;

[0064] The multi-stage countercurrent rinsing in step (11) includes: washing with hot water at 85-90℃ until the sulfuric acid content is less than 0.5g / L, rinsing with weak alkali at 50-54℃ for 5-8 hours, and rinsing with strong alkali at 50-60℃ until pH 7.0;

[0065] (12) Neutralization and desulfurization: Add an alkaline neutralizing agent to adjust the pH to 6.5-7.5 and react for 1-2 hours;

[0066] (13) Oxidation treatment: Optional addition of oxidizing agent to eliminate reducing impurities;

[0067] (14) Phase control heat treatment: first stage: drying at 150-250℃ for 2-4 hours; second stage: holding at 300-400℃ for 4-8 hours; third stage: tempering at 200-250℃ for 2-3 hours (optional).

[0068] Step (14) The second stage of heat treatment is at a temperature of 380℃ for 6-8 hours;

[0069] (15) Fine grinding and classification: Grind to a median particle size of 3-25 μm and pass through a 325 mesh sieve;

[0070] (16) Iron removal: Multi-stage iron removal using electromagnetic iron separator;

[0071] (17) Metered packaging: Packaging under vacuum or inert gas protection.

[0072] The electrolytic manganese dioxide has a mixed crystal form in which γ phase and β phase coexist, and the crystal lattice is uniformly doped with at least one element selected from titanium, vanadium, bismuth and lithium, with Fe content ≤100μg / g and water content <3%.

[0073] (a) Raw material processing:

[0074] (1) Take 1000 kg of pyrolusite (Mn grade 42%), mix it with 120 kg of pyrite, and roast it in a rotary kiln at 650°C for 3 hours;

[0075] (2) After the roasted clinker is cooled, 5000L of 18% sulfuric acid solution is added and leached at 90℃ for 4 hours. The final pH is controlled at 3.5. The crude manganese sulfate solution is obtained by pressure filtration.

[0076] (3) Add soft manganese ore powder to the crude liquid for neutralization and iron removal, add barium sulfide to remove heavy metals, add sodium fluoride to remove calcium and magnesium, and then filter precisely to obtain pure manganese sulfate electrolyte; after testing, Fe=2.3ppm, total heavy metals<1ppm, Ca+Mg=5.8ppm;

[0077] (4) Adjust the electrolyte Mn 2+ The concentration is 45 g / L, and the temperature is controlled at 95℃, ready for electrolysis.

[0078] (ii) Electrolytic machining:

[0079] (5) The electrolyte is fed into the electrolytic cell, using a titanium anode and a copper cathode. The pulse power supply is turned on and the parameters are set as follows: average current density 60A / m², pulse duty cycle 50%, pulse frequency 1000Hz, and electrolyte circulation flow rate 1.0m³ / h·cell.

[0080] (6) During the electrolysis process, a doped modified solution (a mixed solution of tetrabutyl titanate and lithium acetate, with a total Ti+Li concentration of 12 g / L) is continuously added to the anode area at a dropping rate of 2 mL / min·m² anode;

[0081] (7) After 15 days of electrolysis, the thickness of the anode deposit layer reaches 6 mm. The anode plate is removed, and the manganese dioxide deposit layer is peeled off to obtain approximately 620 kg of crude product.

[0082] (III) Finished Product Processing:

[0083] (8) Crush the coarse product to ≤3mm, rinse it three times with 60℃ hot water in a countercurrent manner until the pH of the wash water is 5.2;

[0084] (9) Transfer the rinsed material to a neutralization tank, add ammonia to adjust the pH to 7.0, and stir for 1.5 hours;

[0085] (10) After neutralization, the material is dehydrated and sent to a dynamic rotary kiln. It is first dried at 200℃ for 3 hours, and then heated to 350℃ and kept at that temperature for 6 hours (oxygen-rich atmosphere, oxygen concentration 25%). The rotary kiln speed is 2 rpm.

[0086] (11) After the material is cooled in the furnace, it is pulverized by airflow, passed through a 325-mesh sieve, removed by electromagnetic iron removal, and vacuum packaged to obtain approximately 550 kg of finished electrolytic manganese dioxide.

[0087] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for producing electrolytic manganese dioxide for batteries with improved discharge performance, characterized in that, Includes the following steps: (a) Raw material processing procedures, including: (1) Reduction roasting: Mix pyrolusite powder and reducing agent at a mass ratio of 100:(8-15) and roast at 600-850℃ for 2-4 hours; (2) Acid leaching reaction: The roasted clinker is leached with 15-25% sulfuric acid solution at 80-95℃ for 3-6 hours, and the final pH is controlled to be 3.0-4.0; (3) Multi-stage deep purification: iron removal by oxidation, heavy metal removal by sulfidation, calcium and magnesium removal by fluorination, and precision filtration are performed in sequence; (4) Temperature and concentration adjustment: Adjust Mn 2+ Concentration up to 37-50 g / L, H2SO4 concentration up to 30-41 g / L, temperature up to 92-98℃; (ii) Electrolytic machining process, including: (5) Electrolyte pretreatment: Control suspended particles, adjust MnSO4 concentration to 130-135 g / L, and H2SO4 concentration to 30-32 g / L; (6) Pulse current electrolysis: pulse current density 40-80 A / m², pulse frequency 500-2000 Hz, pulse duty cycle 30%-70%, electrolysis temperature 92-98℃, electrolysis time 5-10 days; (7) Ultrasonic-assisted electrolysis: Apply ultrasonic waves at a frequency of 20-40 kHz and a power density of 0.1-0.5 W / cm². (8) In-situ doping: Add a doping modification solution containing at least one element among titanium, vanadium, bismuth and lithium to the anode area, with a total concentration of doping elements of 5-20 g / L and a dropping rate of 0.5-5 mL / (min·m²) anode; (9) Stripping and collection: When the sediment layer is 3-8 mm thick, stripping is performed to obtain crude electrolytic manganese dioxide; (iii) Finished product processing steps, including: (10) Coarse crushing: crush to a particle size ≤ 5 mm; (11) Multi-stage countercurrent rinsing: Use hot water at 50-90℃ for multi-stage rinsing, including hot water washing for acid, weak alkali rinsing, strong alkali rinsing, and hot water washing for alkali; (12) Neutralization and desulfurization: Add an alkaline neutralizing agent to adjust the pH to 6.5-7.5 and react for 1-2 hours; (13) Oxidation treatment: Optional addition of oxidizing agent to eliminate reducing impurities; (14) Phase control heat treatment: first stage: drying at 150-250℃ for 2-4 hours; second stage: holding at 300-400℃ for 4-8 hours; third stage: tempering at 200-250℃ for 2-3 hours (optional). (15) Fine grinding and classification: Grind to a median particle size of 3-25 μm and pass through a 325 mesh sieve; (16) Iron removal: Multi-stage iron removal using electromagnetic iron separator; (17) Metered packaging: Packaging under vacuum or inert gas protection.

2. The method for producing electrolytic manganese dioxide for batteries with improved discharge performance according to claim 1, characterized in that: The reducing agent in step (1) is pulverized coal or pyrite; when using pyrite, the roasting temperature is 600-700℃.

3. The method for producing electrolytic manganese dioxide for batteries with improved discharge performance according to claim 1, characterized in that: In step (3), the oxidation to remove iron uses manganese dioxide ore powder or hydrogen peroxide as the oxidant, the reaction temperature is 80-90℃, and the amount of oxidant used is 1.08 times the theoretical amount; the sulfidation to remove heavy metals uses barium sulfide or SDD as the sulfiding agent, the amount added is 2g / L, the reaction temperature is 60℃, and the reaction time is 60min.

4. The method for producing electrolytic manganese dioxide for batteries with improved discharge performance according to claim 1, characterized in that: The frequency of the pulse current in step (6) is 1000Hz and the current density is 50 A / m².

5. The method for producing electrolytic manganese dioxide for batteries with improved discharge performance according to claim 1, characterized in that: In the doping modification liquid described in step (8), the doping of bismuth can suppress the disproportionation reaction and stabilize the crystal lattice.

6. The method for producing electrolytic manganese dioxide for batteries with improved discharge performance according to claim 1, characterized in that: Step (11) involves multi-stage countercurrent rinsing, which includes: washing with hot water at 85-90℃ until the sulfuric acid content is less than 0.5g / L, rinsing with weak alkali at 50-54℃ for 5-8 hours, and rinsing with strong alkali at 50-60℃ until the pH is 7.

0.

7. The method for producing electrolytic manganese dioxide for batteries with improved discharge performance according to claim 1, characterized in that: Step (14) The second heat treatment temperature is 380℃ and the time is 6-8 hours.

8. The method for producing electrolytic manganese dioxide for batteries with improved discharge performance according to claim 1, characterized in that: The electrolytic manganese dioxide has a mixed crystal form in which γ phase and β phase coexist, and the crystal lattice is uniformly doped with at least one element selected from titanium, vanadium, bismuth and lithium, with Fe content ≤100μg / g and water content <3%.

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