CN114540837A - Electrolytic manganese dioxide crystal form conversion process - Google Patents
Electrolytic manganese dioxide crystal form conversion process Download PDFInfo
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- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 title claims abstract description 181
- 239000013078 crystal Substances 0.000 title claims abstract description 44
- 238000000034 method Methods 0.000 title claims abstract description 36
- 230000008569 process Effects 0.000 title claims abstract description 31
- 238000006243 chemical reaction Methods 0.000 title claims abstract description 26
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 49
- 239000003792 electrolyte Substances 0.000 claims abstract description 43
- 239000002245 particle Substances 0.000 claims abstract description 11
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 claims abstract description 10
- 239000000126 substance Substances 0.000 claims abstract description 8
- SQQMAOCOWKFBNP-UHFFFAOYSA-L manganese(II) sulfate Chemical compound [Mn+2].[O-]S([O-])(=O)=O SQQMAOCOWKFBNP-UHFFFAOYSA-L 0.000 claims abstract description 6
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims abstract description 5
- 239000012535 impurity Substances 0.000 claims abstract description 5
- 238000002386 leaching Methods 0.000 claims abstract description 5
- 229940099596 manganese sulfate Drugs 0.000 claims abstract description 5
- 235000007079 manganese sulphate Nutrition 0.000 claims abstract description 5
- 239000011702 manganese sulphate Substances 0.000 claims abstract description 5
- NIFIFKQPDTWWGU-UHFFFAOYSA-N pyrite Chemical compound [Fe+2].[S-][S-] NIFIFKQPDTWWGU-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910052683 pyrite Inorganic materials 0.000 claims abstract description 5
- 239000011028 pyrite Substances 0.000 claims abstract description 5
- 238000001914 filtration Methods 0.000 claims abstract description 4
- 238000005868 electrolysis reaction Methods 0.000 claims description 33
- WAEMQWOKJMHJLA-UHFFFAOYSA-N Manganese(2+) Chemical compound [Mn+2] WAEMQWOKJMHJLA-UHFFFAOYSA-N 0.000 claims description 16
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 7
- 239000011572 manganese Substances 0.000 claims description 7
- 229910000978 Pb alloy Inorganic materials 0.000 claims description 3
- 229910045601 alloy Inorganic materials 0.000 claims description 2
- 239000000956 alloy Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 2
- 230000010355 oscillation Effects 0.000 description 19
- 230000000694 effects Effects 0.000 description 17
- 239000000243 solution Substances 0.000 description 14
- 238000005265 energy consumption Methods 0.000 description 11
- 229910006287 γ-MnO2 Inorganic materials 0.000 description 8
- 230000008021 deposition Effects 0.000 description 6
- 229910002059 quaternary alloy Inorganic materials 0.000 description 6
- 230000007423 decrease Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 230000010287 polarization Effects 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 229910000914 Mn alloy Inorganic materials 0.000 description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- XLYOFNOQVPJJNP-ZSJDYOACSA-N heavy water Substances [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 description 3
- MECMQNITHCOSAF-UHFFFAOYSA-N manganese titanium Chemical compound [Ti].[Mn] MECMQNITHCOSAF-UHFFFAOYSA-N 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 230000000737 periodic effect Effects 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 239000010936 titanium Substances 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- 229910052684 Cerium Inorganic materials 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000008151 electrolyte solution Substances 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910052746 lanthanum Inorganic materials 0.000 description 2
- 229910000357 manganese(II) sulfate Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- MINVSWONZWKMDC-UHFFFAOYSA-L mercuriooxysulfonyloxymercury Chemical compound [Hg+].[Hg+].[O-]S([O-])(=O)=O MINVSWONZWKMDC-UHFFFAOYSA-L 0.000 description 2
- 229910000371 mercury(I) sulfate Inorganic materials 0.000 description 2
- 238000013508 migration Methods 0.000 description 2
- 230000005012 migration Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000002860 competitive effect Effects 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 239000012634 fragment Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000001027 hydrothermal synthesis Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 229910001437 manganese ion Inorganic materials 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/21—Manganese oxides
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/50—Processes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
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- Organic Chemistry (AREA)
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Abstract
The invention relates to the technical field of battery materials, and discloses an electrolytic manganese dioxide crystal form conversion process, which comprises the following steps: preparing a leaching solution, namely reacting manganese oxide ore with pyrite under the conditions of preset acidity and preset temperature; preparing electrolyte, adding lime water into the leachate, and adjusting the pH value; removing impurities, and filtering and purifying the prepared electrolyte; respectively adjusting current density, temperature, sulfuric acid concentration and voltage parameters of an electrolytic cell containing a manganese sulfate electrolyte to obtain electrolytic manganese dioxide with different transformed crystal forms; wherein the electrolyte contains electrolytic manganese dioxide suspended particles or chemical manganese dioxide. Through the steps, the crystal form stability and the discharge performance of the manganese dioxide and the quality of the electrolytic manganese dioxide product can be effectively improved.
Description
Technical Field
The invention relates to the technical field of battery materials, in particular to a conversion process for electrolytic manganese dioxide.
Background
Electrolytic manganese dioxide has the advantages of high chemical purity, crystal type (' gamma type), reasonable solid phase surface property, good anode forming property and the like, and is a main raw material of the current high-performance chemical battery.
At present, the preparation method of electrolytic manganese dioxide mainly comprises MnSO4-H2SO4The electrolytic manganese dioxide prepared by the electrolytic method of the system is high in impurity content, so that the electrolytic manganese dioxide is low in purity, and the quality of the electrolytic manganese dioxide generated by the electrolytic process still has some defects: (1) the traditional physical and chemical theory is difficult to guide the growth and control of electrolytic manganese dioxide, so that the crystal form stability of the electrolytic manganese dioxide is poor; (2) the equipment for producing electrolytic manganese dioxide has fallen behind, resulting in electrolytic manganese dioxide being a high energy consuming industry.
Disclosure of Invention
The invention mainly aims to provide a process for converting the crystal form of electrolytic manganese dioxide, and aims to solve the technical problems of poor crystal form stability, low discharge performance and poor quality of electrolytic manganese dioxide products of electrolytic manganese dioxide.
In order to achieve the above object, the present invention provides an electrolytic manganese dioxide crystal form conversion process, which comprises the following steps:
preparing a leaching solution, namely reacting manganese oxide ore with pyrite under the conditions of preset acidity and preset temperature;
preparing electrolyte, adding lime water into the leachate, and adjusting the pH value;
removing impurities, and filtering and purifying the prepared electrolyte;
respectively adjusting current density, temperature, sulfuric acid concentration and voltage parameters of an electrolytic cell containing a manganese sulfate electrolyte to obtain directionally-converted crystal electrolytic manganese dioxide;
wherein the electrolyte contains electrolytic manganese dioxide or chemical manganese dioxide suspended particles.
Optionally, the current density is from 80A/m2Increased to 640A/m2。
Optionally, the temperature is increased from 35 ℃ to 95 ℃.
Optionally, the sulfuric acid concentration is increased from 0M to 1.5M.
Optionally, the voltage parameter is kept constant during electrolysis.
Optionally, a rare earth element is added to the electrolyte.
Optionally, the electrolytic manganese dioxide is post-treated, the post-treatment comprising a heat treatment.
The invention also provides an electrolytic manganese dioxide crystal form conversion process, which comprises the following steps:
the obtained Mn-containing alloy contains 60g/L Mn2+0.5M sulfuric acid electrolyte;
respectively adjusting current density, temperature, sulfuric acid concentration and voltage parameters of the electrolyte to obtain directionally-converted crystal electrolytic manganese dioxide;
wherein the anode of the electrolytic cell is Pb alloy.
In the technical scheme provided by the invention, the electrolytic manganese dioxide crystal form conversion process comprises the steps of preparing a leaching solution, and reacting manganese oxide ore and pyrite under the conditions of preset acidity and preset temperature; preparing electrolyte, adding lime water into the electrolyte, and adjusting the pH value; then the electrolyte is filtered, purified and decontaminated. Further, current density, temperature, sulfuric acid concentration and voltage parameters of the electrolytic cell containing the electrolyte are respectively adjusted to obtain the directionally-converted crystal form electrolytic manganese dioxide, wherein the electrolyte contains electrolytic manganese dioxide or chemical suspended particles.
Drawings
One or more embodiments are illustrated in drawings corresponding to, and not limiting to, the embodiments, in which elements having the same reference number designation may be represented as similar elements, unless specifically noted, the drawings in the figures are not to scale.
FIG. 1 is a schematic flow diagram of an electrolytic manganese dioxide crystal form conversion process of the present invention;
FIG. 2 is the electrical efficiency/energy consumption versus time for different current densities according to the present invention;
FIG. 3 shows the electrolysis of MnO at different currents according to the present invention2XRD pattern of (a);
FIG. 4 is a graph of electrical efficiency/energy consumption versus time at different temperatures according to the present invention;
FIG. 5 shows the electrolysis of MnO at different temperatures according to the present invention2XRD pattern of (a);
FIG. 6 is a graph of electrical efficiency/energy consumption versus time for the present invention;
FIG. 7 is an XRD pattern of electrolytic MnO2 at different sulfuric acid concentrations according to the present invention;
FIG. 8 is a graph of the effect of different voltages on EMD crystal forms of the present invention;
FIG. 9 is a diagram of the EMD crystal patterns under different conditions according to the present invention;
FIG. 10 is a graph of the effect of rare earth element addition on EMD crystal form of the present invention;
FIG. 11 is a graph showing the effect of different heat treatment conditions on the EMD crystal form of the present invention;
Detailed Description
In order to facilitate an understanding of the invention, the invention is described in more detail below with reference to the accompanying drawings and specific examples. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Furthermore, the technical features mentioned in the different embodiments of the invention described below can be combined with each other as long as they do not conflict with each other.
The invention provides an electrolytic manganese dioxide crystal form conversion process, as shown in figure 1, which comprises the following steps:
s1, preparing a leaching solution, and reacting manganese oxide ore with pyrite under the conditions of preset acidity and preset temperature;
s2, preparing electrolyte, adding lime water into the leachate, and adjusting the pH value;
s3, removing impurities, and filtering and purifying the prepared electrolyte;
s4, respectively adjusting current density, temperature, sulfuric acid concentration and voltage parameters of an electrolytic cell containing a manganese sulfate electrolyte to obtain electrolytic manganese dioxide with different transformed crystal forms;
wherein the electrolyte contains electrolytic manganese dioxide or chemical manganese dioxide suspended particles; the post-treatment includes heat treatment.
In MnSO4-H2SO4-H2In an O electrolysis system, the total reaction is as follows:
MnSO4+2H2O＝MnO2+H2SO4+H2↑
the reactions that may occur at the anode are:
Mn2++2H20＝MnO2+4H++2e- Eθ＝1.23V (1)
Mn2+＝Mn3++e- Eθ＝1.51V (2)
Mn2++4H2O＝MnO4-+8H++5e- Eθ＝1.51V (3)
MnO2+2H2O＝MnO4-+4H++3e- Eθ＝1.695V (4)
2H2O＝O2+4H++4e- Eθ＝1.229V (5)
from the standard electrode potential, the anode is mainly the competitive reaction of (1) and (5), and the electrolyte is adjustedThe main reaction on the anode is reaction (1), and the hydrogen evolution reaction on the cathode is as follows: 2H++2e-＝H2↑
MnO2Has various crystal forms including alpha, beta, gamma, etc., and the MnO2 for industrial electrolysis is generally gamma-MnO2。
In this example, the effect of current density on electrolytic manganese dioxide is as follows:
current efficiency
Energy consumption
Wherein, W: energy consumption/KW h-1*t-1(ii) a V is the cell voltage/V; η: current efficiency/%; 1.622: MnO2Electrochemical equivalent/g A-1h-1Electrical efficiency/energy consumption-time at different current densities, as shown in figure 2, the greater the current density available, the greater the total current through the cell. The greater the voltage drop due to the resistance of the cell, the greater the degree of polarization of the electrodes. In addition to the main reactions, oxygen evolution side reactions also follow, leading to cell voltage increases, electrolysis consumption increases, and current efficiency decreases. The current density is kept at 160A/m in terms of current efficiency and energy consumption2Preferably, the plant is generally 60 to 80 A.m2Lower current density. However, the low current density results in a lower single cell yield, limiting the annual yield of EMD (electrolytic manganese dioxide).
The MnO obtained under different current levels was tested2A crystalline form of (a). As shown in FIG. 3, it can be seen that MnO was synthesized under all current conditions2All contain gamma-MnO2. MnO Synthesis with increasing Current2The crystal form is not changed and the peak intensity is gradually reduced because of MnO being too large in current2Fast nucleation rate, large amount of MnO2The grains have less time to grow.
Effect of current density on EMD morphology: the current density is from 80A/m2Increased to 640A/m2Current densityThe lower degree is 80A/m2The EMD formed is small fragments in the form of sheets, MnO increases with the current density2The deposition was progressively tighter until a massive solid was obtained.
In this example, the effect of temperature on EMD (manganese dioxide) is as follows:
current efficiency
Energy consumption
Wherein, W: energy consumption/KW h-1*t-1(ii) a V is cell voltage/V; eta: current efficiency/%; 1.622: MnO2Electrochemical equivalent/g A-1h-1The electrical efficiency/energy consumption-time diagram at different temperatures is shown in fig. 4. The temperature is increased from 35 ℃ to 95 ℃, the cell voltage is reduced, the current efficiency is improved, and the energy consumption is reduced. In electrolytic EMD, Mn near the anode proceeds with the progress of electrolysis2+Tends to be deficient and must be replenished by mass transfer processes to enable electrolysis to continue. In general electrolytic process, mass transfer is simultaneously completed due to ion migration, convection and diffusion processes, but when the manganese sulfate solution is electrolyzed, manganese dioxide is deposited at the anode due to the action of electric field force, but Mn is added2+Rather than migrating to the anode, ion migration does not favor mass transfer processes but is counterproductive. Therefore, the convection and diffusion must be strong enough to convert Mn to Mn2+To the anode region. The temperature of the electrolyte is improved, solution convection is facilitated, the diffusion process is accelerated, concentration polarization is reduced, the conductivity of the solution is enhanced, and the voltage of the cell is reduced. On the other hand, as the temperature increases, the anodic electrochemical polarization decreases resulting in a decrease in the anodic potential and a concomitant decrease in the cell voltage. The electrolysis process can be carried out at a lower potential, reducing oxygen evolution and Mn formation2+And the like. Therefore, to obtain a higher current efficiency, the temperature is controlled at 90 ℃ or higher, at 160A/m2The current efficiency of more than 97% can be achieved at the current density of (2). The crystal forms of the products are all gamma-MnO2And conforms to the standard card JCPDS NO. 14-0644.
The MnO obtained at different temperatures (35 ℃ -95 ℃) was tested2A crystalline form of (a). As shown in FIG. 5, it can be seen that MnO2 synthesized at each temperature has a similar crystalline form, all being γ -MnO2(JCPDS No.42-1317) the peak intensity gradually increased with increasing temperature, since MnO was hindered by oxygen evolution side reactions at low temperatures2And (4) nucleating and growing. Higher temperature, higher peak intensity, MnO2The higher the crystallinity.
The temperature is increased from 35 ℃ to 95 ℃, and the EMD is changed from a compact lamellar structure to a surface loose porous structure.
In this example, the effect of sulfuric acid concentration on EMD is as follows:
current efficiency
Energy consumption
Wherein, W: energy consumption/KW h-1*t-1(ii) a V is the cell voltage/V; eta: current efficiency/%; 1.622: MnO2Electrochemical equivalent/g A-1h-1The electrical efficiency/energy consumption-time diagram at different temperatures is shown in fig. 6. With the increase of the sulfuric acid concentration, the cell voltage and the electrical efficiency show a tendency of decreasing first and then increasing. The reduction is due to the addition of sulfuric acid which increases the conductivity of the solution while H+The increase in concentration reduces the cathode polarization.
The MnO obtained at different sulfuric acid concentrations was tested2A crystalline form of (a). As shown in FIG. 7, it can be seen that MnO was synthesized2All have gamma-MnO2Peak of (2). The XRD peak intensity slightly increased with increasing sulfuric acid concentration.
The crystalline forms of MnO2 obtained at different acid concentrations (concentration of H2SO4 from 0M to 1.5M) were tested. It can be seen that the MnO2 synthesized at each acid concentration has a similar appearance, all being γ -MnO2(JCPDS No.42-1317) and the EMD gradually changes from a loose bulk on the surface to a flat dense bulk solid as the temperature increases.
In this example, the effect of constant voltage electrolysis on EMD, as shown in FIGS. 8 and 9, MnO2 was γ -MnO2 under different voltage conditions of constant voltage electrolysis. According to the previous literature research, temperature and acidity influence the crystal form of the electrolytic product in electrolytic manganese dioxide, so that the electrolyte temperature is increased to 95 ℃, the sulfuric acid concentration is 1M, and a weaker alpha-MnO 2 peak appears in the electrolytic product.
In this example, the effect of the rare earth elements on the electrolytic MnO2 product is as follows:
rare earth elements La and Ce are added into the electrolyte, as shown in figure 10, corresponding to gamma-MnO2The characteristic peak (JCPDS No.14-0644) shows that the crystal form of the electrolytic manganese dioxide is gamma-MnO2And the crystal form of the manganese dioxide is not changed after the rare earth element is added. The rare earth addition amount is small, and La and Ce peaks do not appear.
In this example, CMD or EMD was added to the electrolyte mainly because the addition of suspended particles reduced the microscopic current density on the surface of the electrolytic product. Because part of the suspended particles play the role of crystal nuclei in the process of electric crystallization in the electrolytic process. The addition of some suspended particles in the electrolyte has the advantages that the reaction of separating out manganese dioxide in the electrolysis process is not only carried out on the surface of the anode, but also carried out on the surface of the suspended particles adsorbed on the anode, which is equivalent to increase the surface area of the anode, and the current density in the electrolysis process can be reduced under the condition of certain electrolysis current density. The SBP method not only breaks through the limit of single-bath yield of the traditional process, but also can greatly improve the production capacity of the electrolytic bath under the condition of higher current density.
Further, the types of suspended electrolytic particles were compared: CMD prepared by hydrothermal method and EMD prepared by electrolytic method, and it is found that the crystal form of manganese dioxide can not be changed after adding suspended manganese dioxide into electrolyte, and the crystal form is still gamma-MnO2。
In this example, the effect of heat treatment of the EMD product on the crystalline form of electrolytic MnO2 is as follows:
MnSO4-H2SO4the method for preparing manganese dioxide by high-temperature electrolysis of a system is taken as the mainstream method for producing EMD in all countries at present, the current efficiency can reach more than 97 percent, and the electrolysis product obtained under the electrolysis condition is generally gamma-MnO2The morphology thereof is alsoThe structure is a lamellar block structure, and the electric efficiency can be improved to a certain extent by increasing the temperature or adding suspended particles.
In this example, the effect of different heat treatment conditions on the EMD crystal form is shown in fig. 11. The effect of adjusting the electrochemical performance of the EMD product by improving the physicochemical properties of the EMD product through adjusting the electrolysis parameters is limited, so that more research is now focused on post-treatment modification (such as doping, heat treatment, etc.) of the electrolytic EMD product to obtain good battery charge and discharge performance.
The invention also provides an electrolytic manganese dioxide crystal form conversion process, which comprises the following steps:
preparing electrolyte containing 60g/L of Mn2+ and 0.5M sulfuric acid;
respectively adjusting current density, temperature, sulfuric acid concentration and voltage parameters of the electrolyte to obtain directionally-converted crystal electrolytic manganese dioxide;
wherein the anode of the electrolytic cell is Pb alloy.
In the present embodiment, the electrode: anode: a Pb-based electrode; cathode: a copper plate; reference: a mercurous sulfate electrode; electrolyte solution: 60g/L Mn2+0.5M sulfuric acid.
Electrolytic MnO2The electrolyte of (A) is MnSO4And H2SO4，H2SO4Is added mainly to increase the conductivity of the solution and to reduce the cell voltage.
In the present embodiment, the influence of the current density is as follows:
in the electrolysis of MnO2When Pb-based electrolysis (quaternary alloy) is used as an anode, no electrochemical oscillation phenomenon is detected when the current is less than 0.01A, and the manganese dioxide is completely deposited on the polar plate in the electrolysis process and does not drop into the solution due to the small current, so that the electrolyte is still in a clear state. Electrochemical oscillation is detected when the current is greater than 0.01A, and MnO is present as the current increases2MnO formation rate of anode formation is accelerated2Gradually fall to the bottom of the tank. The initial voltage is maintained between 1.8V and 2.2V, and the potential-time curve shows a certain periodicity, so that the influence of the current magnitude on the amplitude and the frequency of the potential-time curve is examined.
When Pb-based electrolysis (quaternary alloy) is used as an anode in electrolytic manganese dioxide, the frequency of electrochemical oscillation is firstly reduced and then increased along with the increase of current density, and when the current is 0.3A, the frequency is the minimum; the frequency of the electrochemical oscillation increases gradually with increasing current density.
In this embodiment, the influence of the voltage is as follows:
in MnSO4-H2SO4The periodic current oscillation can be detected under different voltages (1.5V-8.0V) by an electrolytic system. In the electrolysis of MnO2When Pb-based electrolysis (quaternary alloy) is used as an anode, the amplitude of electrochemical oscillation is increased and then reduced along with the increase of voltage, and when the voltage is 3, the amplitude is 0.045A at most; the frequency of the electrochemical oscillation increases with increasing voltage and then remains constant. When MnO is electrolyzed2The MnO cannot be changed by increasing the voltage continuously after the voltage reaches a certain level2The deposition rate.
In the present embodiment, the influence of temperature: the low-temperature region generates potential oscillation, the amplitude is not greatly influenced by temperature rise, the oscillation period is obviously reduced, and the oscillation disappears when the temperature is higher than 35 ℃.
In this embodiment, H+Influence of concentration: electrolytic MnO2The solution conductivity can be improved by adding sulfuric acid into the electrolyte, H+The concentration is increased, and the induction period of the generated potential oscillation is obviously prolonged.
When Pb-based electrolysis (quaternary alloy) is used as the anode in the electrolysis of MnO2, H+Lower concentration, amplitude of potential-time curve with C (H)+) Is increased when H is increased+The amplitude remains unchanged after the concentration is increased to 0.5M; the frequency of the potential-time curve increases first with increasing voltage.
In this example, Mn2+The effect of concentration is as follows:
preparing electrolyte into different Mn2+The concentration of (1) is (80g/L, 60g/L, 40g/L, 20g/L, 10g/L, 5 g/L) respectively2SO4The concentration was kept constant at 0.5M (conductivity in the system was maintained). The quaternary alloy electrode is added into Mn2+Electrolyzing the electrolyte with the concentration of 80g/L to generate current oscillationAnd (4) stabilizing, and measuring a current-time curve according to a method that the concentration is gradually decreased. When the system has current oscillation, as long as Mn is present in the electrolyte2+All of which are capable of sustaining current oscillation, and Mn2+The concentration has little effect on the oscillation amplitude and has a significant effect on the oscillation frequency.
In the electrolysis of MnO2When Pb-based electrolysis (quaternary alloy) is used as the anode, a layer of MnO is deposited on the surface of the electrode2After, Mn2+The concentration has little effect on the amplitude of the potential-time curve, but the frequency of the potential-time curve is a function of Mn2+The concentration decreases and increases.
In this example, the effect of the rare earth element additive: adding Ce (SO) into the electrolyte4)2Then, the constant-current potential oscillation amplitude and frequency have almost no influence.
In this embodiment, the influence of the plate: the anode plate for industrially electrolyzing manganese dioxide is a titanium-manganese alloy electrode, and the cathode plate is a red copper electrode. The manganese dioxide electrode on different electrode plates can generate different electrode potentials, and the manganese dioxide electrode can affect the manganese ion intermediate state and electrochemical oscillation.
And (3) testing conditions are as follows:
an electrode: anode: a titanium manganese alloy electrode; cathode: a copper plate; reference: a mercurous sulfate electrode;
electrolyte solution: 60g/L Mn2+0.5M sulfuric acid; constant voltage electrolysis at normal temperature (20 ℃) is carried out, and the voltage is increased from 3V to 10V. Little MnO is left on the titanium plate when the titanium-manganese alloy is used as the anode in the electrolysis of MnO22Deposition of MnO2Slower deposition kinetics and increased current and voltage to MnO2The deposition influence is small.
In the electrolysis of MnO2When the titanium plate is used as the anode plate for electrolysis, the phenomena of periodic current oscillation and periodic potential oscillation do not occur. Because the experiments are all normal temperature (20 ℃), manganese dioxide is hardly deposited on the titanium plate, and a manganese dioxide layer is not formed, which is consistent with the influence of temperature on EMD deposition in the research experiment of the process parameters of electrolytic manganese dioxide, and the low temperature is not beneficial to the EMD deposition.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; within the idea of the invention, also technical features in the above embodiments or in different embodiments may be combined, steps may be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. The electrolytic manganese dioxide crystal form conversion process is characterized by comprising the following steps of:
preparing a leaching solution, namely reacting manganese oxide ore with pyrite under the conditions of preset acidity and preset temperature;
preparing electrolyte, adding lime water into the leachate, and adjusting the pH value;
removing impurities, and filtering and purifying the prepared electrolyte;
respectively adjusting current density, temperature, sulfuric acid concentration and voltage parameters of an electrolytic cell containing a manganese sulfate electrolyte to obtain directionally-converted crystal electrolytic manganese dioxide;
wherein the electrolyte contains electrolytic manganese dioxide or chemical manganese dioxide suspended particles.
2. Electrolytic manganese dioxide crystal form conversion process according to claim 1, characterized in that the current density is from 80A/m2Increased to 640A/m2。
3. Electrolytic manganese dioxide crystal form conversion process according to claim 1, characterized in that the temperature is increased from 35 ℃ to 95 ℃.
4. Electrolytic manganese dioxide crystal form conversion process according to claim 1, characterized in that the sulfuric acid concentration is increased from 0M to 1.5M.
5. The electrolytic manganese dioxide crystal form conversion process according to claim 1, wherein the voltage parameter is kept constant during electrolysis.
6. The electrolytic manganese dioxide crystal form conversion process according to claim 1, wherein a rare earth element is added to the electrolyte.
7. The electrolytic manganese dioxide crystal form conversion process according to claim 1, wherein the electrolytic manganese dioxide is subjected to a post-treatment, the post-treatment comprising a heat treatment.
8. The electrolytic manganese dioxide crystal form conversion process is characterized by comprising the following steps of:
the obtained Mn-containing alloy contains 60g/L Mn2+0.5M sulfuric acid electrolyte;
respectively adjusting current density, temperature, sulfuric acid concentration and voltage parameters of the electrolyte to obtain directionally-converted crystal electrolytic manganese dioxide;
wherein the anode of the electrolytic cell is Pb alloy.
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