A layered cobalt-manganese double hydroxide and its preparation method and application

Abstract

The present invention discloses a layered cobalt-manganese double metal hydroxide and its preparation method and application, which belongs to the technical field of positive electrode materials for aqueous zinc ion secondary batteries. x Mn y ‑LDH, the molar ratio of Co to Mn is 1:3. The preparation method is as follows: pre-treating carbon cloth; dissolving cobalt salt and manganese salt in a solvent to obtain an electroplating solution; placing the electroplating solution in an electrolytic cell, using the pre-treated carbon cloth as the working electrode, and using three electrodes to perform electrodeposition to obtain Co x Mn y -LDH. The present invention Co x Mn y ‑LDH is used as the cathode material of aqueous zinc ion secondary batteries to reduce Mn 2+ The oxidation deposition energy barrier is reduced to achieve a high loading of active material MnO2, and Mn 2+ Reversible dissolution / deposition reaction between MnO2 and H + / Zn 2+ The co-intercalation reaction enables the full battery to have a long charge and discharge cycle life and high rate capacity.

Description

Technical Field

[0001] The invention belongs to the technical field of positive electrode materials for aqueous zinc ion secondary batteries and relates to a layered cobalt-manganese double metal hydroxide and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries are widely used due to their high energy density and ideal charge-discharge cycle life. However, the organic electrolytes used in lithium-ion batteries pose flammable and explosive risks; the nickel, cobalt, and lithium resources used in the electrodes are scarce, and the battery packaging environment requires a low water and oxygen content, resulting in high manufacturing costs.

[0003] Aqueous zinc-ion batteries (AZIBs) are secondary batteries that utilize zinc ion migration. They utilize zinc foil as the negative electrode, a manganese-based material that undergoes redox reactions as the positive electrode, and an aqueous solution of zinc and manganese salts as the electrolyte. The zinc and manganese used in the positive and negative electrodes of AZIBs are abundant, and the packaging process requires no water or oxygen, enabling large-scale, low-cost manufacturing. They are suitable for energy storage in low- and mid-range electric vehicles, as well as large-scale static storage of renewable energy sources, such as intermittent clean energy sources like solar, wind, and tidal power.

[0004] Cathode materials are a crucial component of aqueous zinc-ion batteries and determine their overall performance. Among numerous cathode materials, manganese-based cathode materials have been extensively studied due to their low toxicity and abundant resources. However, existing manganese-based cathode materials still suffer from numerous issues, such as insufficient rate capacity, material dissolution during charge and discharge, and a significant decrease in charge and discharge cycle stability, thus limiting the practical application of aqueous zinc-ion batteries.

[0005] Based on this, the development of manganese-based positive electrode materials with high specific capacity and good charge-discharge cycle performance is the key to promoting the practical application of aqueous zinc-ion secondary batteries. Summary of the Invention

[0006] In order to solve the problems raised in the above background technology, the purpose of the present invention is to provide a layered cobalt-manganese double hydroxide and its preparation method and application. x Mn y -LDH) as a positive electrode material for aqueous zinc ion secondary batteries, reducing Mn 2+ The oxidation deposition energy barrier is reduced to achieve a high loading of active material MnO2, and Mn occurs during the charge and discharge process. 2+ Reversible dissolution / deposition reaction between MnO2 and H + / Zn 2+The co-intercalation reaction ultimately results in a full battery with a long charge and discharge cycle life and high rate capacity.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows: on the one hand, the present invention provides a layered cobalt-manganese double hydroxide, which is a two-dimensional layered material with cobalt-manganese hydroxide as the layer plate; the layered cobalt-manganese double hydroxide is denoted as Co x Mn y -LDH, the molar ratio of Co to Mn is 1:3.

[0008] In another aspect, the present invention provides a method for preparing the above-mentioned layered cobalt-manganese double hydroxide, comprising the following steps:

[0009] (1) pre-treating the carbon cloth to obtain pre-treated carbon cloth;

[0010] (2) dissolving cobalt salt and manganese salt in a solvent to obtain an electroplating solution;

[0011] (3) The electroplating solution obtained in step (2) is placed in an electrolytic cell, and the pretreated carbon cloth obtained in step (1) is used as a working electrode to prepare layered cobalt-manganese double hydroxide by electrodeposition using a three-electrode method.

[0012] Furthermore, step (1) is specifically as follows: placing the carbon cloth in a potassium permanganate aqueous solution, adjusting the pH to 1-2, then ultrasonically treating the cloth under heating conditions, and then washing the cloth until the pH is 7 to obtain a pretreated carbon cloth.

[0013] Furthermore, the concentration of the potassium permanganate aqueous solution is 0.1 mol / L to 0.5 mol / L;

[0014] The heating temperature is 60° C. to 80° C., and the ultrasonic treatment time is 30 min to 60 min.

[0015] Furthermore, the cobalt salt is selected from at least one of cobalt nitrate, cobalt sulfate, and cobalt chloride;

[0016] The manganese salt is selected from at least one of manganese sulfate, manganese nitrate, manganese chloride and manganese acetate.

[0017] Furthermore, step (3) is specifically as follows: placing the electroplating solution obtained in step (2) in an electrolytic cell, using the pretreated carbon cloth obtained in step (1) as a working electrode, a platinum sheet as a counter electrode, and a saturated calomel electrode as a reference electrode, and adopting a three-electrode method to perform electrodeposition under constant potential conditions to prepare layered cobalt manganese double hydroxide.

[0018] Furthermore, the constant potential is -1.2 V (vs. SCE) to -0.8 V (vs. SCE);

[0019] The temperature of the electrodeposition is 30° C. to 60° C., and the time of the electrodeposition is 5 min to 15 min.

[0020] On the other hand, the present invention provides a use of the above-mentioned layered cobalt-manganese double hydroxide or the layered cobalt-manganese double hydroxide prepared by any of the above-mentioned preparation methods in a zinc ion battery.

[0021] In another aspect, the present invention provides an aqueous zinc ion secondary battery positive electrode, comprising the layered cobalt manganese double hydroxide described above or the layered cobalt manganese double hydroxide prepared by any of the above preparation methods.

[0022] In another aspect, the present invention provides an aqueous zinc-ion secondary battery positive electrode, comprising a carbon cloth current collector and a positive electrode material electrochemically grown in situ on the carbon cloth current collector; the positive electrode material is the layered cobalt-manganese double hydroxide described above, or a layered cobalt-manganese double hydroxide prepared by any of the above-described preparation methods. The carbon cloth current collector is primarily used to support the layered cobalt-manganese double hydroxide and provide electrical conductivity, and is not particularly limited, as long as its physical morphology and conductivity are not altered by the electrochemical reaction.

[0023] In another aspect, the present invention provides an aqueous zinc ion secondary battery, comprising the above-mentioned aqueous zinc ion secondary battery positive electrode.

[0024] Furthermore, it also includes a negative electrode, a separator and an electrolyte, wherein the negative electrode is zinc foil; the electrolyte is a ZnSO4 aqueous solution with a molar concentration of 2 mol / L and a MnSO4 aqueous solution with a molar concentration of 0.1 mol / L; and the separator is a separator commonly used in zinc ion batteries.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The layered cobalt-manganese double hydroxide (Co x Mn y -LDH) has a layered structure and is used as a positive electrode material for zinc ion batteries. During the electrochemical reaction, it reduces the Mn 2+ The oxidation deposition energy barrier of Mn in the electrolyte 2+ More easily oxidized to MnO2 and deposited on Co x Mn y -LDH matrix, in the subsequent charge and discharge process, both Mn 2+ The reversible dissolution and deposition between MnO2 and the residual MnO2 occurs + / Zn 2+ Co-intercalation / deintercalation reaction. x Mny -LDH has both Mn 2+ The dissolution / deposition reaction of Co and the intercalation of MnO2 can significantly improve the rate capacity of the electrode; x Mn y -LDH stabilizes the two-dimensional layered structure and gives the electrode a long charge and discharge cycle life. The aqueous zinc ion secondary battery assembled with the layered cobalt manganese double metal hydroxide of the present invention is -1 The capacity retention rate reaches 98% after 1000 current density charge and discharge cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some of the embodiments described in this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0028] Figure 1 This is the SEM image of Co1Mn3-LDH prepared in Example 1 of the present invention, wherein Figure 1 b in Figure 1 A partial enlarged view of a in FIG;

[0029] Figure 2 This is a transmission electron microscope image of Co1Mn3-LDH prepared in Example 1 of the present invention, wherein Figure 2 a in the figure is a low-magnification transmission electron microscope image of Co1Mn3-LDH. Figure 2 b in the figure is the high-magnification transmission electron microscope image and selected area electron diffraction image of Co1Mn3-LDH. Figure 2 Figure c is a high-magnification transmission lattice fringe image of Co1Mn3-LDH;

[0030] Figure 3 This is the EDS element distribution diagram of Co1Mn3-LDH prepared in Example 1 of the present invention;

[0031] Figure 4 This is the XRD pattern of Co1Mn3-LDH prepared in Example 1 of the present invention;

[0032] Figure 5 This is the XPS graph of Co1Mn3-LDH prepared in Example 1 of the present invention, wherein Figure 5 a in the figure is the full XPS spectrum. Figure 5 b in the figure is the Co 2p spectrum. Figure 5 The c in the figure is the Mn 2p spectrum. Figure 5 The d in the figure is the O 1s spectrum;

[0033] Figure 6 1 is a cyclic voltammetry curve of the battery 1 of the present invention;

[0034] Figure 7 The battery 1 of the present invention is 0.2A g -1 Charge and discharge curves at current density;

[0035] Figure 8 is a rate capacity curve diagram of the battery 1 of the present invention;

[0036] Figure 9 1 is the electrochemical impedance diagram of the battery 1 of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0038] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0039] Unless otherwise specified, the technical / scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. Although this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this application.

[0040] The layered cobalt-manganese double hydroxide (Co x Mn y -LDH) is a two-dimensional nanosheet, which is used as the positive electrode material of zinc ion battery. During the charge and discharge process, Mn in the electrolyte 2+ Co x Mn y -LDH is the matrix and the oxidized deposit is MnO2. Therefore, the electrode performance is Co x Mn y -Comprehensive manifestation of LDH and MnO2.

[0041] The layered cobalt-manganese double hydroxide (Co x Mn y -LDH) as a cathode material for zinc-ion batteries, Co x Mn y-LDH has an electrochemically stable two-dimensional layered structure, and the nanosheet morphology increases the contact area between the electrode and the electrolyte, which is conducive to fully exerting the electrochemical properties.

[0042] The layered cobalt-manganese double hydroxide (Co x Mn y -LDH) is used as the positive electrode material of zinc ion batteries. During the electrochemical reaction, Mn in the electrolyte is converted to 2+ Oxidation deposition is MnO2, and in the subsequent charge and discharge process, Mn 2+ Reversible dissolution / deposition reaction between MnO2 and residual MnO2 + / Zn 2+ co-intercalation / deintercalation reaction.

[0043] The layered cobalt-manganese double hydroxide (Co x Mn y -LDH) as the positive electrode material of zinc ion battery, the coexistence of multiple electrochemical mechanisms improves the rate capacity of the electrode, and Co x Mn y The two-dimensional structure of LDH ensures the stability of the electrochemical reaction and gives the battery a long charge and discharge cycle life.

[0044] The layered cobalt-manganese double hydroxide (Co x Mn y -LDH) as a positive electrode material for zinc-ion batteries has high specific capacity and good charge-discharge cycle stability, which can provide the positive electrode with stable charge-discharge cycle performance. It can be used to prepare the positive electrode for aqueous zinc-ion secondary batteries.

[0045] The present application is further described below through examples.

[0046] Example 1

[0047] This embodiment provides a layered cobalt-manganese double hydroxide having a Co / Mn molar ratio of 1:3, and the preparation method is as follows:

[0048] (1) The carbon cloth was cut into discs with a diameter of 12 mm, placed in a 0.5 mol / L potassium permanganate aqueous solution, and diluted sulfuric acid was added to control the pH of the potassium permanganate aqueous solution to 1-2. The carbon cloth was placed in a constant temperature ultrasonic water bath at 60 °C for 30 min, and then washed with ethanol and deionized water to a pH of 7 to obtain the pretreated carbon cloth.

[0049] (2) Dissolve 68.6 mg (0.375 mmol) of Co(NO3)2 and 169.9 mg (1.125 mmol) of MnSO4 in 30 mL of deionized water to obtain an electroplating solution.

[0050] (3) The plating solution was transferred to a 50 mL electrolytic cell. The pretreated carbon cloth was used as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. In a constant temperature water bath at 30°C, at a constant potential of -1.0 V (vs. SCE), the electroplating system was electroplated for 10 min to prepare layered cobalt manganese double hydroxide. The substance obtained by electrodeposition using this three-electrode system was recorded as Co1Mn3-LDH. After preparation, the carbon cloth electrode loaded with Co1Mn3-LDH was thoroughly rinsed with deionized water and then dried in a 60°C oven for 12 h.

[0051] The Co1Mn3-LDH prepared in Example 1 was scanned by scanning electron microscopy. Figure 1 As shown. Figure 1 It can be seen that Co1Mn3-LDH grows tightly on the surface of carbon cloth fibers through electrodeposition without any gaps or shedding, which is beneficial to increase the active material loading per unit area and impart high capacity characteristics.

[0052] The Co1Mn3-LDH prepared in Example 1 was scanned by transmission electron microscopy. Figure 2 As shown. Figure 2 From a and b in the figure, we can see that Co1Mn3-LDH is a nanosheet structure. Figure 2 The inset in Figure b shows clear diffraction rings, indicating the polycrystalline nature of Co1Mn3-LDH. Figure 2 As can be seen from Figure c, the 0.45 nm interlayer spacing in the yellow rectangular area can be attributed to the (001) crystal plane of Mn(OH)2, and the 0.26 nm and 0.23 nm interlayer spacing in the blue rectangular area are attributed to the (009 / 012) and (015) crystal planes of Co1Mn3-LDH, respectively, thereby confirming the correct synthesis of Co1Mn3-LDH.

[0053] The Co1Mn3-LDH prepared in Example 1 was subjected to EDS elemental analysis. The results are as follows: Figure 3 As shown, from Figure 3 It can be seen that Mn, Co and O elements are evenly distributed, indicating that the substance is a uniform compound.

[0054] The Co1Mn3-LDH prepared in Example 1 was subjected to XRD test. The results are as follows: Figure 4 As shown, from Figure 4 It can be seen that the diffraction peaks at 12.2°, 34.4°, 37.9° and 59.6° correspond to the (003), (009 / 012), (015) and (110) crystal planes of Co1Mn3-LDH, respectively.

[0055] The Co1Mn3-LDH prepared in Example 1 was subjected to XPS test. Figure 5 As shown. Figure 5 As can be seen from a in the figure, the full spectrum shows the characteristic peaks of three elements: Co, Mn and O, indicating that Co, Mn and O elements exist in the material at the same time. Figure 5 As can be seen in b, the two groups of spin-orbit resolved peaks of Co 2p in Co1Mn3-LDH can be fitted as Co 2+ 、Co 3+ and satellite peaks, indicating that Co 2+ and Co 3+ Coexistence. Figure 5 As can be seen from the figure c, the two groups of spin-orbit resolved peaks of Mn 2p in Co1Mn3-LDH can be fitted as Mn 2+ 、Mn 3+ 、Mn 4+ and satellite peaks, indicating that Mn 2+ 、Mn 3+ and Mn 4+ Coexistence. Figure 5 As can be seen in Figure d, the O 1s spectra of Co1Mn3-LDH at 531.1 eV and 533.1 eV can be attributed to adsorbed water and M-OH (M = Mn, Co), respectively.

[0056] The Co1Mn3-LDH prepared in Example 1 was used as a positive electrode material in a zinc-ion battery. An aqueous zinc-ion secondary battery was assembled using a carbon cloth positive electrode loaded with Co1Mn3-LDH, a zinc foil negative electrode, and a glass fiber filter paper separator. The electrolytes were a 2 mol / L aqueous ZnSO4 solution and a 0.1 mol / L aqueous MnSO4 solution. The assembled full cell is designated as Cell 1.

[0057] The performance of battery 1 is tested, and the cyclic voltammetry curve of battery 1 is as follows: Figure 6 As shown, from Figure 6 It can be seen that in the test range of 0.8V to 1.9V, the oxidation peak of battery 1 is 1.6V, and the reduction peaks are 1.2V and 1.35V. Battery 1 at 0.2A g -1 The charge and discharge curve at current density is as follows Figure 7 As shown, from Figure 7 It can be seen that the charge and discharge range is between 0.8V and 1.9V, the discharge platform is maintained at 1.4V, and the specific capacity can reach 275mAh g -1 The rate capacity curve of battery 1 is as follows: Figure 8 As shown, from Figure 8 It can be seen that the current density is 0.2A g -1 , 0.5A g-1 、1A g -1 、2A g -1 、3A g -1 and 5A g -1 When the discharge capacity of battery 1 is 279 mAh g -1 , 204mAh g -1 , 161mAh g -1 , 132mAh g -1 , 119mAh g -1 and 109mAh g -1 The electrochemical impedance spectroscopy diagram of battery 1 is shown in Figure 2. Figure 9 As shown, from Figure 9 It can be seen that battery 1 exhibits good charge transfer impedance and mass transfer impedance.

[0058] Comparative Example 1

[0059] This comparative example provides a layered cobalt-manganese double hydroxide having a Co / Mn molar ratio of 5:1, and the preparation method is as follows:

[0060] (1) The carbon cloth was cut into discs with a diameter of 12 mm, placed in a 0.5 mol / L potassium permanganate aqueous solution, and diluted sulfuric acid was added to control the pH of the potassium permanganate aqueous solution to 1-2. The carbon cloth was placed in a constant temperature ultrasonic water bath at 60 °C for 30 min, and then washed with ethanol and deionized water to a pH of 7 to obtain the pretreated carbon cloth.

[0061] (2) Dissolve 228.6 mg (1.25 mmol) of Co(NO3)2 and 37.8 mg (0.25 mmol) of MnSO4 in 30 mL of deionized water to obtain an electroplating solution.

[0062] (3) The plating solution was transferred to a 50 mL electrolytic cell. The pretreated carbon cloth was used as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. In a constant temperature water bath at 30°C, at a constant potential of -1.0 V (vs. SCE), the electroplating system was electroplated for 10 min to prepare layered cobalt manganese double hydroxide. The material obtained by electrodeposition using this three-electrode system was recorded as Co5Mn1-LDH. After preparation, the carbon cloth electrode loaded with Co5Mn1-LDH was thoroughly rinsed with deionized water and then dried in a 60°C oven for 12 h.

[0063] Comparative Example 2

[0064] This comparative example provides a layered cobalt-manganese double hydroxide having a Co / Mn molar ratio of 4:1, and the preparation method is as follows:

[0065] (1) The carbon cloth was cut into discs with a diameter of 12 mm, placed in a 0.5 mol / L potassium permanganate aqueous solution, and diluted sulfuric acid was added to control the pH of the potassium permanganate aqueous solution to 1-2. The carbon cloth was placed in a constant temperature ultrasonic water bath at 60 °C for 30 min, and then washed with ethanol and deionized water to a pH of 7 to obtain the pretreated carbon cloth.

[0066] (2) Dissolve 219.5 mg (1.2 mmol) of Co(NO3)2 and 45.3 mg (0.3 mmol) of MnSO4 in 30 mL of deionized water to obtain an electroplating solution.

[0067] (3) The plating solution was transferred to a 50 mL electrolytic cell. The pretreated carbon cloth was used as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. In a constant temperature water bath at 30°C, at a constant potential of -1.0 V (vs. SCE), the electroplating system was electroplated for 10 min to prepare layered cobalt manganese double hydroxide. The substance obtained by electrodeposition using this three-electrode system was recorded as Co4Mn1-LDH. After preparation, the carbon cloth electrode loaded with Co4Mn1-LDH was thoroughly rinsed with deionized water and then dried in a 60°C oven for 12 h.

[0068] Comparative Example 3

[0069] This comparative example provides a layered cobalt-manganese double hydroxide having a Co / Mn molar ratio of 3:1, and the preparation method is as follows:

[0070] (1) The carbon cloth was cut into discs with a diameter of 12 mm, placed in a 0.5 mol / L potassium permanganate aqueous solution, and diluted sulfuric acid was added to control the pH of the potassium permanganate aqueous solution to 1-2. The carbon cloth was placed in a constant temperature ultrasonic water bath at 60 °C for 30 min, and then washed with ethanol and deionized water to a pH of 7 to obtain the pretreated carbon cloth.

[0071] (2) Dissolve 205.8 mg (1.125 mmol) of Co(NO3)2 and 56.6 mg (0.375 mmol) of MnSO4 in 30 mL of deionized water to obtain an electroplating solution.

[0072] (3) The plating solution was transferred to a 50 mL electrolytic cell. The pretreated carbon cloth was used as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. In a constant temperature water bath at 30°C, at a constant potential of -1.0 V (vs. SCE), the electroplating system was electroplated for 10 min to prepare layered cobalt manganese double hydroxide. The substance obtained by electrodeposition using this three-electrode system was recorded as Co3Mn1-LDH. After preparation, the carbon cloth electrode loaded with Co3Mn1-LDH was thoroughly rinsed with deionized water and then dried in a 60°C oven for 12 h.

[0073] Comparative Example 4

[0074] This comparative example provides a layered cobalt-manganese double hydroxide having a Co / Mn molar ratio of 2:1, and the preparation method is as follows:

[0075] (1) The carbon cloth was cut into discs with a diameter of 12 mm, placed in a 0.5 mol / L potassium permanganate aqueous solution, and diluted sulfuric acid was added to control the pH of the potassium permanganate aqueous solution to 1-2. The carbon cloth was placed in a constant temperature ultrasonic water bath at 60 °C for 30 min, and then washed with ethanol and deionized water to a pH of 7 to obtain the pretreated carbon cloth.

[0076] (2) Dissolve 182.9 mg (1 mmol) Co(NO3)2 and 75.5 mg (0.5 mmol) MnSO4 in 30 mL of deionized water to obtain an electroplating solution.

[0077] (3) The plating solution was transferred to a 50 mL electrolytic cell. The pretreated carbon cloth was used as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. In a constant temperature water bath at 30°C, at a constant potential of -1.0 V (vs. SCE), the electroplating system was electroplated for 10 min to prepare layered cobalt manganese double hydroxide. The substance obtained by electrodeposition using this three-electrode system was recorded as Co2Mn1-LDH. After preparation, the carbon cloth electrode loaded with Co2Mn1-LDH was thoroughly rinsed with deionized water and then dried in a 60°C oven for 12 h.

[0078] Comparative Example 5

[0079] This comparative example provides a layered cobalt-manganese double hydroxide having a Co / Mn molar ratio of 1:1, and the preparation method is as follows:

[0080] (1) The carbon cloth was cut into discs with a diameter of 12 mm, placed in a 0.5 mol / L potassium permanganate aqueous solution, and diluted sulfuric acid was added to control the pH of the potassium permanganate aqueous solution to 1-2. The carbon cloth was placed in a constant temperature ultrasonic water bath at 60 °C for 30 min, and then washed with ethanol and deionized water to a pH of 7 to obtain the pretreated carbon cloth.

[0081] (2) Dissolve 137.2 mg (0.75 mmol) of Co(NO3)2 and 113.3 mg (0.75 mmol) of MnSO4 in 30 mL of deionized water to obtain an electroplating solution.

[0082] (3) The plating solution was transferred to a 50 mL electrolytic cell. The pretreated carbon cloth was used as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. In a constant temperature water bath at 30°C, at a constant potential of -1.0 V (vs. SCE), the electroplating system was electroplated for 10 min to prepare layered cobalt manganese double hydroxide. The substance obtained by electrodeposition using this three-electrode system was recorded as Co1Mn1-LDH. After preparation, the carbon cloth electrode loaded with Co1Mn1-LDH was thoroughly rinsed with deionized water and then dried in a 60°C oven for 12 h.

[0083] Comparative Example 6

[0084] This comparative example provides a layered cobalt-manganese double hydroxide having a Co / Mn molar ratio of 1:2, and the preparation method is as follows:

[0085] (1) The carbon cloth was cut into discs with a diameter of 12 mm, placed in a 0.5 mol / L potassium permanganate aqueous solution, and diluted sulfuric acid was added to control the pH of the potassium permanganate aqueous solution to 1-2. The carbon cloth was placed in a constant temperature ultrasonic water bath at 60 °C for 30 min, and then washed with ethanol and deionized water to a pH of 7 to obtain the pretreated carbon cloth.

[0086] (2) Dissolve 91.5 mg (0.5 mmol) of Co(NO3)2 and 151.0 mg (1 mmol) of MnSO4 in 30 mL of deionized water to obtain an electroplating solution.

[0087] (3) The plating solution was transferred to a 50 mL electrolytic cell. The pretreated carbon cloth was used as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. In a constant temperature water bath at 30°C, at a constant potential of -1.0 V (vs. SCE), the electroplating system was electroplated for 10 min to prepare layered cobalt manganese double hydroxide. The substance obtained by electrodeposition using this three-electrode system was recorded as Co1Mn2-LDH. After preparation, the carbon cloth electrode loaded with Co1Mn2-LDH was thoroughly rinsed with deionized water and then dried in a 60°C oven for 12 h.

[0088] Comparative Example 7

[0089] This comparative example provides a layered cobalt-manganese double hydroxide having a Co / Mn molar ratio of 1:4, and the preparation method is as follows:

[0090] (1) The carbon cloth was cut into discs with a diameter of 12 mm, placed in a 0.5 mol / L potassium permanganate aqueous solution, and diluted sulfuric acid was added to control the pH of the potassium permanganate aqueous solution to 1-2. The carbon cloth was placed in a constant temperature ultrasonic water bath at 60 °C for 30 min, and then washed with ethanol and deionized water to a pH of 7 to obtain the pretreated carbon cloth.

[0091] (2) Dissolve 54.9 mg (0.3 mmol) of Co(NO3)2 and 181.2 mg (1.2 mol) of MnSO4 in 30 mL of deionized water to obtain an electroplating solution.

[0092] (3) The plating solution was transferred to a 50 mL electrolytic cell. The pretreated carbon cloth was used as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. In a constant temperature water bath at 30°C, at a constant potential of -1.0 V (vs. SCE), the electroplating system was electroplated for 10 min to prepare layered cobalt manganese double hydroxide. The material obtained by electrodeposition using this three-electrode system was recorded as Co1Mn4-LDH. After preparation, the carbon cloth electrode loaded with Co1Mn4-LDH was thoroughly rinsed with deionized water and then dried in a 60°C oven for 12 h.

[0093] Comparative Example 8

[0094] This comparative example provides a layered cobalt-manganese double hydroxide having a Co / Mn molar ratio of 1:5, and the preparation method is as follows:

[0095] (1) The carbon cloth was cut into discs with a diameter of 12 mm, placed in a 0.5 mol / L potassium permanganate aqueous solution, and diluted sulfuric acid was added to control the pH of the potassium permanganate aqueous solution to 1-2. The carbon cloth was placed in a constant temperature ultrasonic water bath at 60 °C for 30 min, and then washed with ethanol and deionized water to a pH of 7 to obtain the pretreated carbon cloth.

[0096] (2) Dissolve 45.7 mg (0.25 mmol) of Co(NO3)2 and 188.8 mg (1.25 mmol) of MnSO4 in 30 mL of deionized water to obtain an electroplating solution.

[0097] (3) The plating solution was transferred to a 50 mL electrolytic cell. The pretreated carbon cloth was used as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. In a constant temperature water bath at 30°C, at a constant potential of -1.0 V (vs. SCE), the electroplating system was electroplated for 10 min to prepare layered cobalt manganese double hydroxide. The material obtained by electrodeposition using this three-electrode system was recorded as Co1Mn5-LDH. After preparation, the carbon cloth electrode loaded with Co1Mn5-LDH was thoroughly rinsed with deionized water and then dried in a 60°C oven for 12 h.

[0098] Comparative Example 9

[0099] This comparative example provides a cobalt hydroxide positive electrode material, and the preparation method is as follows:

[0100] (1) The carbon cloth was cut into discs with a diameter of 12 mm, placed in a 0.5 mol / L potassium permanganate aqueous solution, and diluted sulfuric acid was added to control the pH of the potassium permanganate aqueous solution to 1-2. The carbon cloth was placed in a constant temperature ultrasonic water bath at 60 °C for 30 min, and then washed with ethanol and deionized water to a pH of 7 to obtain the pretreated carbon cloth.

[0101] (2) Dissolve 274.4 mg (1.5 mmol) of Co(NO3)2 in 30 mL of deionized water to obtain an electroplating solution.

[0102] (3) The plating solution was transferred to a 50 mL electrolytic cell. The pretreated carbon cloth was used as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. In a constant temperature water bath at 30°C, at a constant potential of -1.0 V (vs. SCE), the electroplating system was electroplated for 10 min to prepare a cobalt hydroxide positive electrode material. The substance obtained by electroplating using this three-electrode system is recorded as Co(OH)2. After preparation, the carbon cloth electrode loaded with Co(OH)2 was thoroughly cleaned with deionized water and then dried in a 60°C oven for 12 h.

[0103] Comparative Example 10

[0104] This comparative example provides a manganese hydroxide positive electrode material, and the preparation method is as follows:

[0105] (1) The carbon cloth was cut into discs with a diameter of 12 mm, placed in a 0.5 mol / L potassium permanganate aqueous solution, and diluted sulfuric acid was added to control the pH of the potassium permanganate aqueous solution to 1-2. The carbon cloth was placed in a constant temperature ultrasonic water bath at 60 °C for 30 min, and then washed with ethanol and deionized water to a pH of 7 to obtain the pretreated carbon cloth.

[0106] (2) Dissolve 226.5 mg (1.5 mmol) of MnSO4 in 30 mL of deionized water to obtain an electroplating solution.

[0107] (3) The plating solution was transferred to a 50 mL electrolytic cell. The pretreated carbon cloth was used as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. In a constant temperature water bath at 30°C, at a constant potential of -1.0 V (vs. SCE), the electroplating system was electroplated for 10 min to prepare the manganese hydroxide positive electrode material. The substance obtained by electrodeposition using this three-electrode system is recorded as Mn(OH)2. After preparation, the carbon cloth electrode loaded with Mn(OH)2 was thoroughly cleaned with deionized water and then dried in a 60°C oven for 12 h.

[0108] The materials prepared in Example 1 and Comparative Examples 1-10 were used as positive electrode materials in zinc-ion batteries. Aqueous zinc-ion secondary batteries were assembled using the aforementioned carbon cloth positive electrode loaded with electrodeposited material, zinc foil negative electrode, and glass fiber filter paper separator. The electrolytes consisted of a 2 mol / L aqueous ZnSO₄ solution and a 0.1 mol / L aqueous MnSO₄ solution. The assembled full batteries were designated Battery 1, Battery D1, Battery D2, Battery D3, Battery D4, Battery D5, Battery D6, Battery D7, Battery D8, Battery D9, and Battery D10.

[0109] The performance test of the aqueous zinc ion secondary battery was carried out, and the test results are shown in Table 1.

[0110] Table 1 Performance test data of aqueous zinc ion secondary batteries assembled with different cathode materials

[0111]

[0112] As shown in Table 1, the aqueous zinc ion secondary battery assembled with Co1Mn3-LDH prepared by the present invention has a high -1 The discharge specific capacity at the current density and the capacity retention rate after 1000 charge and discharge cycles are 132 mAh g -1 and 98%, both higher than batteries assembled with other positive electrodes.

[0113] Example 1 compares Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, Comparative Example 5, Comparative Example 6, Comparative Example 7 and Comparative Example 8, in which the ratios of Co and Mn are different, while Comparative Example 9 and Comparative Example 10 do not introduce Mn and Co respectively. The Mn / Co system can induce Mn in the electrolyte. 2+ Oxidation deposition is MnO2, and Mn occurs in subsequent charge and discharge cycles. 2+ Reversible dissolution / deposition of MnO2 and H + / Zn 2+ The co-intercalation / deintercalation reaction contributes to the charge and discharge capacity. The different Mn / Co ratios in Comparative Examples 1-8 will affect the Mn 2+ The oxidation deposition energy barrier cannot fully utilize the Mn in the electrolyte. 2+ , and more manganese-based by-products are produced, which affects the battery discharge capacity and charge-discharge cycle life. Co1Mn3-LDH can reduce Mn 2+ The oxidation deposition energy barrier promotes more Mn 2+ Oxidation deposition is MnO2, which is an active material and generates Mn 2+ Reversible dissolution / deposition of MnO2 and H + / Zn 2+ Co-intercalation / deintercalation reaction achieves good rate capacity and cycle performance.

[0114] In summary, the layered cobalt manganese double hydroxide (Co1Mn3-LDH) of the present invention is used as the positive electrode material of aqueous zinc ion secondary battery. During the full battery charging process, the Mn 2+ Oxidized to MnO2 and deposited on Co x Mn y -LDH surface, Mn 2+ The reversible dissolution / deposition reaction between MnO2 and the H2O2 can achieve the 2e transfer reaction, and the H2O2 of the residual MnO2 can also occur. + / Zn 2+ The co-intercalation / deintercalation reaction achieves the purpose of high rate capacity. x Mn y -LDH can reduce Mn 2+ The oxidation deposition energy barrier of MnO2 is reduced, which promotes the stable dissolution / deposition reaction of MnO2, thereby achieving stable charge and discharge cycles of the battery.

[0115] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of the present invention.

Claims

1. A positive electrode for an aqueous zinc ion secondary battery, characterized in that It includes a layered cobalt-manganese double metal hydroxide, which is a two-dimensional layered material with cobalt-manganese hydroxide as a layer plate; the layered cobalt-manganese double metal hydroxide is denoted as Co x Mn y -LDH, the molar ratio of Co to Mn is 1:

3.

2. The aqueous zinc ion secondary battery positive electrode according to claim 1, wherein The preparation method of the layered cobalt-manganese double hydroxide comprises the following steps: (1) pre-treating the carbon cloth to obtain pre-treated carbon cloth; (2) dissolving cobalt salt and manganese salt in a solvent to obtain an electroplating solution; (3) The electroplating solution obtained in step (2) is placed in an electrolytic cell, and the pretreated carbon cloth obtained in step (1) is used as a working electrode to prepare layered cobalt-manganese double hydroxide by electrodeposition using a three-electrode method.

3. The aqueous zinc ion secondary battery positive electrode according to claim 2, wherein Step (1) is specifically as follows: placing the carbon cloth in a potassium permanganate aqueous solution, adjusting the pH to 1-2, then ultrasonically treating it under heating conditions, and then washing it until the pH is 7 to obtain a pretreated carbon cloth.

4. The aqueous zinc ion secondary battery positive electrode according to claim 3, wherein The concentration of the potassium permanganate aqueous solution is 0.1 mol / L to 0.5 mol / L; The heating temperature is 60° C. to 80° C., and the ultrasonic treatment time is 30 min to 60 min.

5. The aqueous zinc ion secondary battery positive electrode according to claim 2, wherein The cobalt salt is selected from at least one of cobalt nitrate, cobalt sulfate, and cobalt chloride; The manganese salt is selected from at least one of manganese sulfate, manganese nitrate, manganese chloride and manganese acetate.

6. The aqueous zinc ion secondary battery positive electrode according to claim 2, characterized in that Step (3) is specifically as follows: placing the electroplating solution obtained in step (2) in an electrolytic cell, using the pretreated carbon cloth obtained in step (1) as a working electrode, a platinum sheet as a counter electrode, and a saturated calomel electrode as a reference electrode, and adopting a three-electrode method to perform electrodeposition under constant potential conditions to prepare layered cobalt-manganese double hydroxide.

7. The aqueous zinc ion secondary battery positive electrode according to claim 6, characterized in that The constant potential is -1.2V~-0.8V; The temperature of the electrodeposition is 30° C. to 60° C., and the time of the electrodeposition is 5 min to 15 min.

8. An aqueous zinc ion secondary battery, characterized in that The invention comprises the positive electrode of the aqueous zinc ion secondary battery according to any one of claims 1 to 7.

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