In-situ remediation method and application of manganese dioxide

Abstract

The invention discloses an in-situ repair method and application of a manganese dioxide electrode, and belongs to the technical field of energy storage. The in-situ repair method of the manganese dioxide electrode comprises the following steps: reacting a failed manganese dioxide electrode with manganese ions in an alkaline solution, and then carrying out in-situ oxidation treatment. According to the repairing method of the manganese dioxide electrode, the lost manganese material can be supplemented in situ, and meanwhile, a layered structure is constructed in situ, so that the invalid performance is recovered. The specific capacity of the electrode can be optimized and recovered to 584F / g by adjusting the concentration of manganese ions in a reaction solution and the reaction time, which is 1.6 times of the specific capacity of an unrepaired electrode, meanwhile, the specific capacity retention rate under the condition of 30A / g reaches 69%, and the electrode has excellent rate capability.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to an in-situ repair method and application of manganese dioxide. Background Art

[0002] Manganese dioxide is a very promising active electrode material, which has been applied to various electrochemical energy storage fields, including supercapacitors, zinc-ion batteries, zinc-air batteries, etc., due to its advantages such as high theoretical capacity, diversified crystal phases, and adjustable material micromorphology. However, due to the Jan-Taylor effect and the disproportionation reaction of trivalent manganese in the energy storage process, manganese dioxide is prone to loss of manganese active materials and structural collapse, which in turn shows insufficient cycle stability, limiting its practical application. In order to improve the application value of manganese dioxide electrodes, current research mainly focuses on improving their structural stability through material design strategies, including modified doping, interface coating and other means. These methods have achieved results, but are still quite far from practical application and commercial production. In particular, the urgent need to recycle a large number of failed manganese dioxide electrodes is difficult to meet. Therefore, it is of great significance to develop novel green methods to recycle and reuse failed manganese dioxide electrodes to achieve a circular economy. Summary of the invention

[0003] Based on this, in order to solve one of the above technical problems, the present invention provides an in-situ repair method and application of a manganese dioxide electrode, and the specific technical solution is as follows:

[0004] An in-situ repair method for a manganese dioxide electrode, the in-situ repair method comprising the following steps:

[0005] The failed manganese dioxide electrode is immersed in an alkaline solution, an inert gas is introduced, a manganese salt is added, and the solution is stirred under a sealed condition to obtain a manganese precursor electrode;

[0006] The manganese precursor electrode is subjected to in-situ oxidation treatment to obtain a repaired manganese dioxide electrode.

[0007] Furthermore, the alkaline solution is at least one of sodium hydroxide, potassium hydroxide and ammonia water.

[0008] Furthermore, the pH range of the alkaline solution is 8-11.

[0009] Furthermore, the inert gas is at least one of nitrogen and helium.

[0010] Furthermore, the manganese salt is at least one of manganese acetate, manganese sulfate, manganese nitrate and manganese chloride.

[0011] Furthermore, the manganese salt concentration ranges from 0.5 to 15 mmol / L.

[0012] Furthermore, the stirring process is carried out at a rotation speed of 20 r / min to 200 r / min and for a time of 0.5 h to 6 h.

[0013] Furthermore, the in-situ oxidation treatment adopts cyclic voltammetry or cyclic constant current charge and discharge method, and the cyclic voltammetry or cyclic constant current charge and discharge method is carried out in a three-electrode system, the manganese precursor electrode is the working electrode, the graphite electrode is the counter electrode, the silver chloride electrode is the reference electrode, and the lithium sulfate solution is the electrolyte.

[0014] Furthermore, the cyclic voltammetry scanning voltage interval is 0-1.2V, the scanning rate is between 1-100mV / s, and the number of cycles is 2-300 circles; the cyclic constant current charge-discharge method sets the lower limit of the voltage window to the interval of 0-1.2V, the current is 0.2-15mA, and the number of cycles is 2-300 circles.

[0015] In addition, the present invention also provides an application of an in-situ repair method for manganese dioxide electrolysis, and an application of the in-situ repair method in a supercapacitor.

[0016] Under alkaline conditions, divalent manganese ions can react with the failed manganese oxide and precipitate in situ. The precipitate is granular and evenly loaded on the surface of the failed manganese oxide, which can replenish the lost manganese material. Subsequently, in-situ oxidation treatment is performed, and the granular precipitate is oxidized to manganese dioxide and transformed into a layered structure of nanosheets. Due to the replenishment of manganese active materials and the in-situ construction of a unique structure, the electrochemical performance of the originally failed manganese dioxide electrode is restored.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The in-situ repair method of the manganese dioxide electrode of the present invention can replenish the lost manganese active material and construct a layered structure at the same time, and perform in-situ repair from two aspects of load capacity and structure; the load capacity can be regulated by the concentration of manganese salt in the reaction solution and the reaction time, and the layered structure can be regulated by electrochemical oxidation treatment. The repair method is simple and easy to operate, safe and pollution-free, and highly efficient. In addition, the formed layered structure is evenly distributed on the original manganese dioxide surface, which can provide more electrochemical energy storage sites. The in-situ repair method of the manganese dioxide electrode of the present invention can restore the capacitance of the failed manganese dioxide electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention can be further understood from the following description in conjunction with the accompanying drawings. The components in the figures are not necessarily drawn to scale, but the emphasis is placed on illustrating the principles of the embodiments. In different views, the same reference numerals designate corresponding parts.

[0020] Figure 1Schematic diagram of the surface scanning electron microscope of (a) the manganese precursor electrode and (b) the repaired manganese dioxide electron microscope obtained in Example 1 of the present invention;

[0021] Figure 2 Schematic diagram of the surface scanning electron microscope of (a) the manganese precursor electrode and (b) the repaired manganese dioxide electron microscope obtained in Example 2 of the present invention;

[0022] Figure 3 Schematic diagram of the surface scanning electron microscope of (a) the manganese precursor electrode and (b) the repaired manganese dioxide electron microscope obtained in Example 3 of the present invention;

[0023] Figure 4 This is a schematic diagram of a surface scanning electron microscope of a manganese dioxide electron microscope obtained in a comparative example of the present invention;

[0024] Figure 5 Surface Raman spectra of (a) a failed manganese dioxide electrode, (b) a manganese precursor electrode prepared in Example 1 of the present invention, and (c) a repaired manganese dioxide electrode;

[0025] Figure 6 (a) Cyclic voltammetry curve and (b) constant current charge-discharge curve of the manganese dioxide electron microscope repaired in Example 1 of the present invention;

[0026] Figure 7 (a) Cyclic voltammetry curve and (b) constant current charge-discharge curve of the electrode obtained in the comparative example of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with its embodiments. It should be understood that the specific implementation methods described herein are only used to explain the present invention and do not limit the protection scope of the present invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0029] In one embodiment of the present invention, an in-situ repair method for a manganese dioxide electrode comprises the following steps:

[0030] The failed manganese dioxide electrode is immersed in an alkaline solution, an inert gas is introduced, a manganese salt is added, and the solution is stirred under a sealed condition to obtain a manganese precursor electrode;

[0031] The manganese precursor electrode is subjected to in-situ oxidation treatment to obtain a repaired manganese dioxide electrode.

[0032] In one embodiment, the alkaline solution is at least one of sodium hydroxide, potassium hydroxide, and ammonia water.

[0033] In one embodiment, the pH range of the alkaline solution is 8-11.

[0034] In one embodiment, the inert gas is at least one of nitrogen and helium.

[0035] In one embodiment, the manganese salt is at least one of manganese acetate, manganese sulfate, manganese nitrate and manganese chloride.

[0036] In one embodiment, the manganese salt concentration range is 0.5-15 mmol / L.

[0037] In one embodiment, the stirring process has a rotation speed of 20 r / min to 200 r / min and a time of 0.5 h to 6 h.

[0038] In one embodiment, the in-situ oxidation treatment adopts cyclic voltammetry or cyclic constant current charge and discharge method, and the cyclic voltammetry or cyclic constant current charge and discharge method is carried out in a three-electrode system, the manganese precursor electrode is the working electrode, the graphite electrode is the counter electrode, the silver chloride electrode is the reference electrode, and the lithium sulfate solution is the electrolyte.

[0039] In one embodiment, the cyclic voltammetry scanning voltage interval is 0-1.2V, the scanning rate is between 1-100mV / s, and the number of cycles is 2-300 circles; the cyclic constant current charge-discharge method sets the lower limit of the voltage window to the interval of 0-1.2V, the current is 0.2-15mA, and the number of cycles is 2-300 circles.

[0040] In addition, the present invention also provides an application of an in-situ repair method for manganese dioxide electrolysis, and an application of the in-situ repair method in a supercapacitor.

[0041] The in-situ repair method of the manganese dioxide electrode of the present invention can replenish the lost manganese active material and construct a layered structure at the same time, so as to perform in-situ repair from two aspects of load amount and structure.

[0042] The embodiments of the present invention will be described in detail below with reference to specific examples.

[0043] Embodiment 1:

[0044] An in-situ repair method for a manganese dioxide electrode comprises the following steps:

[0045] A sodium hydroxide alkaline solution with a pH of 9 was prepared, and the failed manganese dioxide electrode was immersed in the alkaline solution, nitrogen was introduced for 5 minutes, 10 mmol / L manganese acetate was added, and the mixture was reacted for 4 hours at a stirring rate of 100 r / min under sealed conditions to obtain a manganese precursor electrode;

[0046] A manganese precursor electrode was used as the working electrode, a graphite electrode was used as the counter electrode, and a silver chloride electrode was used as the reference electrode. A 1 mol / L lithium sulfate solution was used as the electrolyte. In this three-electrode system, an electrochemical workstation was used and a cyclic constant current charge and discharge method was adopted. The voltage range was set to 0.1-1.2 V, the current was set to 1 mA, and the number of cycles was set to 10 to obtain a repaired manganese dioxide electrode.

[0047] Reference Figure 1 a, Figure 1 a is a surface scanning electron microscope image of the manganese precursor electrode of this embodiment. It can be seen from the image that granular precipitates are evenly distributed on the surface of the manganese precursor electrode obtained in this embodiment.

[0048] Reference Figure 1 b, Figure 1 b is a surface scanning electron microscope image of the manganese dioxide electrode repaired in this embodiment. It can be seen from the image that the granular precipitates on the surface of the manganese dioxide electrode repaired in this embodiment are transformed into a layered structure after electrochemical oxidation treatment.

[0049] Reference Figure 5 , Figure 5 The Raman spectra of the original failed manganese dioxide electrode, the manganese precursor electrode, and the repaired manganese dioxide electrode are compared. -1 The peak of 650cm is the characteristic peak of birnessite-type manganese dioxide. -1 The peak intensity at is relatively weak, indicating the deformation of the MnO6 octahedron; while the treated manganese precursor electrode shows a broad peak in the range of 580-650cm-1, with the highest intensity at 614cm-1. -1 This may be attributed to the precipitation of trivalent manganese oxide on the electrode surface; after electrochemical oxidation treatment, the repaired manganese dioxide electrode shows the characteristic peaks of birnessite-type manganese dioxide, indicating that the trivalent manganese oxide precipitate is oxidized into manganese dioxide.

[0050] The electrode obtained in this example was subjected to electrochemical testing: the manganese dioxide electrode restored in this example was used as the working electrode, the Pt sheet electrode was used as the counter electrode, and the Ag / AgCl electrode was used as the reference electrode. In a three-electrode system consisting of 0.5 mol / L sodium sulfate aqueous electrolyte, cyclic voltammetry curves at different scan rates and constant current charge-discharge curves at different current densities were tested. The test results are shown in FIG. Figure 6 shown.

[0051] Reference Figure 6 (a) is the cyclic voltammetry curve at different scan rates. It can be seen that the curves are rectangular and roughly symmetrical, and the area increases with the increase of the scan rate, indicating that the electrode has ideal capacitive characteristics and a reversible charge storage process occurs.

[0052] Reference Figure 6 (b) is the constant current charge and discharge curve under different current densities. It can be seen that the curve is straight and symmetrical, indicating that the reaction process is reversible.

[0053] By calculation, the specific capacity of the electrode is 584, 533, 478, 430, 370 and 333 F / g at 1, 2, 5, 10, 20 and 30 A / g, respectively. At a high current density of 30 A / g, the specific capacity is still maintained at 57%, indicating that the electrode has good rate performance.

[0054] comprehensive Figure 1 , Figure 5 , Figure 6 From the analysis, it can be seen that this embodiment successfully repairs the failed manganese dioxide electrode in situ and applies it to supercapacitors.

[0055] Embodiment 2:

[0056] A sodium hydroxide alkaline solution with a pH of 9 was prepared, and the failed manganese dioxide electrode was immersed in the alkaline solution, nitrogen was introduced for 5 minutes, 5 mmol / L manganese acetate was added, and the mixture was reacted for 4 hours at a stirring rate of 100 r / min under sealed conditions to obtain a manganese precursor electrode;

[0057] A manganese precursor electrode was used as the working electrode, a graphite electrode was used as the counter electrode, and a silver chloride electrode was used as the reference electrode. A 1 mol / L lithium sulfate solution was used as the electrolyte. In this three-electrode system, an electrochemical workstation was used and a cyclic constant current charge and discharge method was adopted. The voltage range was set to 0.1-1.2 V, the current was set to 1 mA, and the number of cycles was set to 5 to obtain a repaired manganese dioxide electrode.

[0058] Reference Figure 2 , Figure 2 (a) and (b) are surface scanning electron micrographs of the manganese precursor electrode and the repaired manganese dioxide electrode obtained in this example, respectively. Figure 2 It can be seen that the surface of the manganese precursor electrode obtained in this example is uniformly loaded with granular manganese precipitates, and after in-situ electrochemical oxidation treatment, the granular precipitates are transformed into a lamellar structure.

[0059] Embodiment 3:

[0060] A 1 mmol / L ammonia alkaline solution was prepared, and the failed manganese dioxide electrode was immersed in the alkaline solution, nitrogen was introduced for 5 minutes, 2 mmol / L manganese acetate was added, and the reaction was carried out at a stirring rate of 100 r / min for 5 hours under a sealed condition to obtain a manganese precursor electrode;

[0061] A manganese precursor electrode was used as a working electrode, a graphite electrode was used as a counter electrode, and a silver chloride electrode was used as a reference electrode. A 1 mol / L lithium sulfate solution was used as an electrolyte. In this three-electrode system, an electrochemical workstation was used and a cyclic constant current charge and discharge method was adopted. The voltage range was set to 0.1-1.2 V, the current was set to 2 mA, and the number of cycles was set to 10 to obtain a repaired manganese dioxide electrode.

[0062] Reference Figure 3 , Figure 3 (a) and (b) are surface scanning electron micrographs of the manganese precursor electrode and the repaired manganese dioxide electrode obtained in this example, respectively. Figure 3 It can be seen that the surface of the manganese precursor electrode obtained in this example is uniformly loaded with granular manganese precipitates, and after in-situ electrochemical oxidation treatment, the granular precipitates are transformed into a lamellar structure.

[0063] Comparative Example 1:

[0064] The electrode repairing method of Comparative Example 1 comprises the following steps:

[0065] The failed manganese dioxide electrode was immersed in deionized water, nitrogen was introduced for 5 minutes, 10 mmol / L manganese acetate was added, and the reaction was carried out at a stirring rate of 100 r / min for 4 hours under sealed conditions to obtain a manganese precursor electrode;

[0066] A manganese precursor electrode was used as the working electrode, a graphite electrode was used as the counter electrode, and a silver chloride electrode was used as the reference electrode. A 1 mol / L lithium sulfate solution was used as the electrolyte. In this three-electrode system, an electrochemical workstation was used and a cyclic constant current charge and discharge method was adopted. The voltage range was set to 0.1-1.2 V, the current was set to 1 mA, and the number of cycles was set to 10 to obtain a repaired manganese dioxide electrode.

[0067] Reference Figure 4 A comparative analysis of Figure 4 This is a surface scanning electron microscope image of the manganese precursor electrode obtained in Comparative Example 1. Figure 4 It can be seen that the manganese precursor electrode surface obtained in the reaction solution without adding alkali has no granular precipitate.

[0068] The electrode obtained in this comparative example was subjected to electrochemical testing in the same manner as in Example 1. The test results are shown in FIG. Figure 7 shown.

[0069] Figure 7 (a) Cyclic voltammetry curves at different scan rates; Figure 7 (b) is the constant current charge and discharge curve under different current densities. By calculation, under the conditions of 1, 2, 5, 10, 20 and 30 A / g, the electrode specific capacity is 359, 324, 294, 270, 242 and 226 F / g respectively. Compared with the electrode of Example 1, the electrode specific capacity of Comparative Example 1 is not improved.

[0070] The main electrochemical performance indicators that can be achieved by the electrodes prepared in the above Examples 1-3 and Comparative Examples are shown in Table 1.

[0071] Table 1: Electrochemical performance indicators

[0072]

[0073]

[0074] From the data in Table 1, it can be seen that the specific capacity of the electrodes prepared in Examples 1-3 under 1A / g conditions is significantly better than that of Comparative Example 1, and the specific capacity retention rate under 30A / g conditions is more than 65%, and the rate performance is good, indicating that under alkaline conditions, the failed manganese oxide electrode can be re-deposited on the electrode in the form of manganese oxide after additional manganese ions are added, so that the specific capacity performance is restored while maintaining good rate performance. Comparison of the data between Examples 1-3 shows that the concentration of manganese ions in the reaction solution and the reaction time will affect the load of the manganese oxide precipitate, resulting in different specific capacities. By adjusting the manganese ion concentration and the reaction time, the comprehensive performance of the electrode can be optimized.

[0075] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0076] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An in-situ repair method for a manganese dioxide electrode, characterized in that: The in-situ repair method comprises the following steps: The failed manganese dioxide electrode is immersed in an alkaline solution, an inert gas is introduced, a manganese salt is added, and the solution is stirred under a sealed condition to obtain a manganese precursor electrode; The manganese precursor electrode is subjected to in-situ oxidation treatment to obtain a repaired manganese dioxide electrode.

2. The in-situ repair method according to claim 1, characterized in that: The alkaline solution is at least one of sodium hydroxide, potassium hydroxide and ammonia water.

3. The in-situ repair method according to claim 1, characterized in that: The pH range of the alkaline solution is 8-11.

4. The in-situ repair method according to claim 1, characterized in that: The inert gas is at least one of nitrogen and helium.

5. The in-situ repair method according to claim 1, characterized in that: The manganese salt is at least one of manganese acetate, manganese sulfate, manganese nitrate and manganese chloride.

6. The in-situ repair method according to claim 1, characterized in that: The manganese salt concentration range is 0.5-15 mmol / L.

7. The in-situ repair method according to claim 1, characterized in that: The stirring process has a rotation speed of 20 r / min to 200 r / min and a time of 0.5 h to 6 h.

8. The in-situ repair method according to claim 1, characterized in that: The in-situ oxidation treatment adopts cyclic voltammetry or cyclic constant current charge and discharge method, and the cyclic voltammetry or cyclic constant current charge and discharge method is carried out in a three-electrode system, the manganese precursor electrode is the working electrode, the graphite electrode is the counter electrode, the silver chloride electrode is the reference electrode, and the lithium sulfate solution is the electrolyte.

9. The in-situ repair method according to claim 8, characterized in that: The cyclic voltammetry method has a scanning voltage interval of 0-1.2V, a scanning rate of 1-100mV / s, and a cycle number of 2-300 circles; the cyclic constant current charge-discharge method sets the voltage window lower limit to the interval of 0-1.2V, the current to 0.2-15mA, and the cycle number to 2-300 circles.

10. Application of an in-situ repair method for a manganese dioxide electrode, characterized in that: The application is the application of the in-situ repair method as described in any one of claims 1 to 9 in a supercapacitor.

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