Layered cobalt-manganese double-metal hydroxide as well as preparation method and application thereof

Abstract

The invention discloses a layered cobalt-manganese double-metal hydroxide as well as a preparation method and application thereof, and belongs to the technical field of an aqueous zinc ion secondary battery positive electrode material. The layered cobalt-manganese double-metal hydroxide is marked as CoxMny-LDH, and the molar ratio of Co to Mn is 1: 3. The preparation method comprises the following steps: pretreating the carbon cloth; cobalt salt and manganese salt are dissolved in a solvent to obtain electroplating liquid; the electroplating solution is placed in an electrolytic tank, pretreated carbon cloth serves as a working electrode, and three electrodes are adopted for electrodeposition to prepare CoxMny-LDH. The CoxMny-LDH serves as a positive electrode material of the aqueous zinc ion secondary battery, the oxidation deposition energy barrier of Mn < 2 + > is reduced in the electrochemical reaction process, the high loading capacity of an active substance MnO2 is achieved, the reversible dissolution / deposition reaction between Mn < 2 + > and MnO2 is generated, the H < + > / Zn < 2 + > co-intercalation reaction is generated on undissolved MnO2, and the whole battery has the long charging and discharging cycle life and the high rate capacity.

Description

Technical Field

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

[0002] Lithium-ion batteries have been widely used due to their high energy density and ideal charge-discharge cycle life. However, the organic electrolytes used in lithium-ion batteries have potential hazards of flammability and explosion; the nickel, cobalt, and lithium resources used in electrode materials are scarce, and the battery packaging environment requires low water and oxygen content, so the final manufacturing cost is relatively high.

[0003] Aqueous Zinc-ion Batteries (AZIBs) are secondary batteries in which zinc ions migrate. Among them, a zinc foil serves as the negative electrode, and a manganese-based material that can undergo redox reactions can be selected as the positive electrode, and an aqueous solution of zinc salt and manganese salt serves as the electrolyte. The zinc and manganese resources used in the positive and negative electrodes of aqueous zinc-ion batteries are abundant, and there is no requirement for water and oxygen during the packaging process, so large-scale low-cost manufacturing can be achieved. It can be applied to energy storage for mid- to low-end electric vehicles, or large-scale static energy storage of renewable energy, such as intermittent clean energy storage like solar energy, wind energy, and tidal energy.

[0004] As an important part of aqueous zinc-ion batteries, the cathode material determines the overall performance of the battery. Among many cathode materials, manganese-based cathode materials have been widely studied due to their low toxicity and rich resources. However, there are still many problems with existing manganese-based cathode materials. For example, the rate capacity cannot meet the requirements, and material dissolution occurs during the charge-discharge process, resulting in a significant decrease in the charge-discharge cycle stability, thus limiting the practical application of aqueous zinc-ion batteries.

[0005] Based on this, developing a manganese-based cathode material 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 art, the purpose of the present invention is to provide a layered cobalt-manganese double metal hydroxide, a preparation method thereof, and an application thereof. The layered cobalt-manganese double metal hydroxide (Co x Mn y -LDH) of the present invention, as a cathode material for aqueous zinc-ion secondary batteries, reduces the oxidation deposition energy barrier of Mn 2+ during the electrochemical reaction process, realizes a high loading amount of the active substance MnO2, and a reversible dissolution / deposition reaction occurs between Mn 2+ and MnO2 during the charge-discharge process, and the undissolved MnO2 undergoes H + / Zn 2+The co-intercalation reaction results in the full battery having a long charge-discharge cycle life and high rate capacity.

[0007] 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 metal hydroxide, which is a two-dimensional layered material with a cobalt-manganese hydroxide as the layer board; the layered cobalt-manganese double metal hydroxide is denoted as Co x Mn y -LDH, and the molar ratio of Co to Mn is 1:3.

[0008] On the other hand, the present invention provides a method for preparing the above-mentioned layered cobalt-manganese double metal hydroxide, comprising the following steps:

[0009] (1) Pretreat the carbon cloth to obtain the pretreated carbon cloth;

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

[0011] (3) Place the electroplating solution obtained in step (2) in an electrolytic cell, use the pretreated carbon cloth obtained in step (1) as the working electrode, and prepare the layered cobalt-manganese double metal hydroxide by electro-deposition in a three-electrode manner.

[0012] Further, step (1) is specifically: Place the carbon cloth in an aqueous potassium permanganate solution, adjust the pH to 1-2, then perform ultrasonic treatment under heating conditions, and then wash until the pH is 7 to obtain the pretreated carbon cloth.

[0013] Further, the concentration of the aqueous potassium permanganate 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] Further, 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] Further, step (3) is specifically: Place the electroplating solution obtained in step (2) in an electrolytic cell, use the pretreated carbon cloth obtained in step (1) as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, and perform electro-deposition in a three-electrode manner under a constant potential condition to prepare the layered cobalt-manganese double metal hydroxide.

[0018] Further, the constant potential is -1.2V (vs. SCE) to -0.8V (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 an application of the above-mentioned layered cobalt-manganese bimetallic hydroxide or the layered cobalt-manganese bimetallic hydroxide prepared by any of the above-mentioned preparation methods in a zinc-ion battery.

[0021] On another aspect, the present invention provides a positive electrode for an aqueous zinc-ion secondary battery, including the above-mentioned layered cobalt-manganese bimetallic hydroxide or the layered cobalt-manganese bimetallic hydroxide prepared by any of the above-mentioned preparation methods.

[0022] On another aspect, the present invention provides a positive electrode for an aqueous zinc-ion secondary battery, including 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 above-mentioned layered cobalt-manganese bimetallic hydroxide or the layered cobalt-manganese bimetallic hydroxide prepared by any of the above-mentioned preparation methods. Among them, the carbon cloth current collector is mainly used to load the layered cobalt-manganese bimetallic hydroxide and provide conductivity, and there is no particular limitation as long as its physical morphology and conductivity do not change due to the electrochemical reaction.

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

[0024] Furthermore, it further includes a negative electrode, a separator, and an electrolyte. The negative electrode is a zinc foil; the electrolyte is an aqueous solution of ZnSO4 with a molar concentration of 2 mol / L and an aqueous solution of MnSO4 with a molar concentration of 0.1 mol / L; 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 bimetallic hydroxide (Co x Mn y -LDH) of the present invention has a layered structure. As a positive electrode material for a zinc-ion battery during the electrochemical reaction process, it reduces the oxidation deposition energy barrier of Mn 2+ , promotes Mn in the electrolyte 2+ to be more easily oxidized to MnO2 and deposited on the Co x Mn y -LDH matrix. During the subsequent charge and discharge process, both the reversible dissolution and deposition between Mn 2+ and MnO2 occur, and the co-insertion / extraction reaction of H + / Zn 2+ of the residual MnO2 also occurs. Co x Mny - The dissolution / deposition reaction of Mn exists in LDH, and there is also the intercalation of MnO2, so the rate capacity of the electrode can be significantly improved; Co 2+ - The stable two-dimensional layered structure of Mn x Mn y -LDH endows the electrode with a long cycle life during charge and discharge. The aqueous zinc-ion secondary battery assembled with the layered cobalt-manganese bimetallic hydroxide of the present invention has a capacity retention rate of 98% after 1000 charge and discharge cycles at a current density of 2 A g -1 . Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 It is the SEM image of Co1Mn3-LDH prepared in Example 1 of the present invention, where Figure 1 b in Figure 1 is the partial enlarged view of a in

[0029] Figure 2 It is the transmission electron microscope image of Co1Mn3-LDH prepared in Example 1 of the present invention, where Figure 2 a in Figure 2 is the low-magnification morphology transmission electron microscope image of Co1Mn3-LDH, Figure 2 b in

[0030] Figure 3 is the high-magnification transmission electron microscope image and selected area electron diffraction pattern of Co1Mn3-LDH,

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

[0032] Figure 5 is the XPS pattern of Co1Mn3-LDH prepared in Example 1 of the present invention, where Figure 5 a in Figure 5 is the full XPS spectrum, Figure 5 b in Figure 5 is the Co 2p energy spectrum,

[0033] Figure 6 This is the cyclic voltammogram of Battery 1 of the present invention;

[0034] Figure 7 This is the charge-discharge curve of Battery 1 of the present invention at a current density of 0.2 A g -1 ;

[0035] Figure 8 This is the rate capacity curve of Battery 1 of the present invention;

[0036] Figure 9 This is the electrochemical impedance diagram of Battery 1 of the present invention. Detailed implementation manners

[0037] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0038] Those skilled in the art should understand that in the following description of the embodiments of the present application, the sequence numbers do not imply the order of execution, and some or all of the steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to 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 of ordinary skill in the art to which the present application belongs. Although the present application only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present application.

[0040] The layered cobalt-manganese bimetallic hydroxide (Co x Mn y -LDH) of the present invention is a two-dimensional nanosheet. As the cathode material of the zinc-ion battery, during the charge-discharge process, Mn in the electrolyte 2+ is oxidized and deposited as MnO2 with Co x Mn y -LDH as the matrix. Therefore, the electrode performance is the comprehensive manifestation of Co x Mn y -LDH and MnO2.

[0041] The layered cobalt-manganese bimetallic hydroxide (Co x Mn y -LDH) of the present invention is used as the cathode material of the zinc-ion battery. 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] In the present invention, layered cobalt-manganese bimetallic hydroxide (Co x Mn y -LDH) is used as the cathode material for zinc-ion batteries. During the electrochemical reaction process, Mn in the electrolyte is 2+ oxidatively deposited into MnO2. During subsequent charge and discharge processes, a reversible dissolution / deposition reaction occurs between Mn 2+ and MnO2. At the same time, there is also a co-insertion / extraction reaction of H + / Zn 2+ in the residual MnO2.

[0043] In the present invention, layered cobalt-manganese bimetallic hydroxide (Co x Mn y -LDH) is used as the cathode material for zinc-ion batteries. The coexistence of multiple electrochemical mechanisms improves the rate capacity of the electrode, and the two-dimensional structure of Co x Mn y -LDH ensures the stability of the electrochemical reaction and endows the battery with a long charge-discharge cycle life.

[0044] In the present invention, layered cobalt-manganese bimetallic hydroxide (Co x Mn y -LDH) is used as the cathode material for zinc-ion batteries. It has a high specific capacity and good charge-discharge cycle stability, and can endow the cathode with stable charge-discharge cycle performance. It can be used to prepare the cathode of an aqueous zinc-ion secondary battery for an aqueous zinc-ion secondary battery.

[0045] The following further illustrates the present application through examples.

[0046] Example 1

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

[0048] (1) Cut the carbon cloth into circular pieces with a diameter of 12 mm, place them in a 0.5 mol / L aqueous potassium permanganate solution, add dilute sulfuric acid to control the pH of the aqueous potassium permanganate solution to 1-2, and place them in a 60°C constant-temperature ultrasonic water bath for 30 min. Then, wash them with ethanol and deionized water respectively until the pH is 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) Transfer the electroplating solution into a 50 mL electrolytic cell. Using the pretreated carbon cloth as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, in a constant temperature water bath at 30 °C, under a constant potential of -1.0 V (vs. SCE), the electroplating system was electro-deposited for 10 min to prepare layered cobalt-manganese double metal hydroxide. The substance obtained by electro-deposition using this three-electrode system was denoted as Co1Mn3-LDH. After preparation, the carbon cloth electrode loaded with Co1Mn3-LDH was thoroughly cleaned with deionized water and then dried in an oven at 60 °C for 12 h.

[0051] The Co1Mn3-LDH prepared in Example 1 was scanned by scanning electron microscopy, and the results are as Figure 1 shown. From Figure 1 it can be seen that Co1Mn3-LDH grew tightly on the surface of the carbon cloth fibers by electro-deposition method, and there were no vacancies and exfoliations, which was beneficial to increasing the loading amount of active substances per unit area and endowing high-capacity characteristics.

[0052] The Co1Mn3-LDH prepared in Example 1 was scanned by transmission electron microscopy, and the results are as Figure 2 shown. From Figure 2 a and b in Figure 2 it can be seen that Co1Mn3-LDH has a nanosheet structure. From Figure 2 the inset b in

[0053] it can be seen that clear diffraction rings indicate the polycrystalline nature of Co1Mn3-LDH. From Figure 3 c in Figure 3 it can be seen that the 0.45 nm layer 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 layer spacings in the blue rectangular area are respectively attributed to the (009 / 012) and (015) crystal planes of Co1Mn3-LDH, thus determining the correct synthesis of Co1Mn3-LDH.

[0054] The Co1Mn3-LDH prepared in Example 1 was tested by XRD, and the results are as Figure 4 shown. From Figure 4 it can be seen that the diffraction peaks appearing 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 testing, and the results are as follows Figure 5 shown. As can be seen from Figure 5 a in Figure 5 , the full spectrum shows the characteristic peaks of three elements, Co, Mn, and O, indicating the coexistence of Co, Mn, and O elements in the material. As can be seen from Figure 5 b, the two spin-orbit resolved peaks of Co 2p in Co1Mn3-LDH can be fitted to Co 2+ , Co 3+ and satellite peaks, indicating the coexistence of Co 2+ and Co 3+ in Co1Mn3-LDH. As can be seen from Figure 5 c, the two spin-orbit resolved peaks of Mn 2p in Co1Mn3-LDH can be fitted to Mn 2+ , Mn 3+ , Mn 4+ and satellite peaks, indicating the coexistence of Mn 2+ , Mn 3+ and Mn 4+ in Co1Mn3-LDH. As can be seen from Figure 5 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 the cathode material of a zinc-ion battery in a zinc-ion battery: a water-based zinc-ion secondary battery was assembled with a carbon cloth cathode loaded with Co1Mn3-LDH, a zinc foil anode, and a glass fiber filter paper separator, and the electrolyte was an aqueous solution of 2 mol / L ZnSO4 and an aqueous solution of 0.1 mol / L MnSO4. The assembled full cell was denoted as Cell 1.

[0057] The performance of Cell 1 was tested. The cyclic voltammogram of Cell 1 is as shown in Figure 6 . As can be seen from Figure 6 , in the test range of 0.8 V to 1.9 V, the oxidation peak of Cell 1 is 1.6 V, and the reduction peaks are 1.2 V and 1.35 V. The charge-discharge curve of Cell 1 at a current density of 0.2 A g -1 is as shown in Figure 7 . As can be seen from Figure 7 , the charge-discharge range is between 0.8 V and 1.9 V, the discharge plateau is maintained at 1.4 V, and the specific capacity can reach 275 mAh g -1 . The rate capacity curve of Cell 1 is as shown in Figure 8 . As can be seen from Figure 8 , when the current density is 0.2 A g -1 , 0.5 A g-1 、1 Ag -1 、2 Ag -1 、3 Ag -1 and 5 Ag -1 When discharging, the specific discharge capacities of Battery 1 are 279 mAh / g -1 、204 mAh / g -1 、161 mAh / g -1 、132 mAh / g -1 、119 mAh / g -1 and 109 mAh / g -1 respectively. The electrochemical impedance spectra of Battery 1 are shown as Figure 9 shown. It can be seen from Figure 9 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 bimetallic hydroxide with a Co / Mn molar ratio of 5:1, and the preparation method is as follows:

[0060] (1) Cut the carbon cloth into circular pieces with a diameter of 12 mm, place them in an aqueous solution of potassium permanganate with a concentration of 0.5 mol / L, add dilute sulfuric acid to control the pH of the potassium permanganate aqueous solution to 1-2, and place it in a constant temperature ultrasonic water bath at 60 °C for 30 min. Then wash it with ethanol and deionized water respectively until the pH is 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) Transfer the electroplating solution to a 50 mL electrolytic cell. Use the pretreated carbon cloth as the working electrode, a 10 mm×10 mm×0.2 mm platinum sheet as the counter electrode, and a saturated calomel electrode 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 is electrodeposited for 10 min to prepare a layered cobalt-manganese bimetallic hydroxide. The substance obtained by electrodeposition using this three-electrode system is denoted as Co5Mn1-LDH. After preparation, wash the carbon cloth electrode loaded with Co5Mn1-LDH thoroughly with deionized water, and then dry it in an oven at 60 °C for 12 h.

[0063] Comparative Example 2

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

[0065] (1) Cut the carbon cloth into circular pieces with a diameter of 12 mm, place them in an aqueous solution of potassium permanganate with a concentration of 0.5 mol / L, add dilute sulfuric acid to control the pH of the potassium permanganate aqueous solution to 1-2, and place it in a constant temperature ultrasonic water bath at 60 °C for 30 min. Then, wash it with ethanol and deionized water until the pH is 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) Transfer the electroplating solution to a 50 mL electrolytic cell. Use the pretreated carbon cloth as the working electrode, a 10 mm×10 mm×0.2 mm platinum sheet as the counter electrode, and a saturated calomel electrode 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 is electrodeposited for 10 min to prepare a layered cobalt-manganese bimetallic hydroxide. The substance obtained by electrodeposition using this three-electrode system is denoted as Co4Mn1-LDH. After preparation, thoroughly wash the carbon cloth electrode loaded with Co4Mn1-LDH with deionized water, and then dry it in an oven at 60 °C for 12 h.

[0068] Comparative Example 3

[0069] This comparative example provides a layered cobalt-manganese bimetallic hydroxide with a Co / Mn molar ratio of 3:1. The preparation method is as follows:

[0070] (1) Cut the carbon cloth into circular pieces with a diameter of 12 mm, place them in an aqueous solution of potassium permanganate with a concentration of 0.5 mol / L, add dilute sulfuric acid to control the pH of the potassium permanganate aqueous solution to 1-2, and place it in a constant temperature ultrasonic water bath at 60 °C for 30 min. Then, wash it with ethanol and deionized water until the pH is 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) Transfer the electroplating solution into a 50 mL electrolytic cell. Using the pretreated carbon cloth as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet as the counter electrode, and a saturated calomel electrode 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 performs electrodeposition for 10 min to prepare layered cobalt-manganese double metal hydroxide. The substance obtained by electrodeposition using this three-electrode system is denoted as Co3Mn1-LDH. After preparation, the carbon cloth electrode loaded with Co3Mn1-LDH is thoroughly cleaned with deionized water, and then dried in an oven at 60 °C for 12 h.

[0073] Comparative Example 4

[0074] This comparative example provides layered cobalt-manganese double metal hydroxide with a Co / Mn molar ratio of 2:1. The preparation method is as follows:

[0075] (1) Cut the carbon cloth into circular pieces with a diameter of 12 mm, place them in an aqueous solution of 0.5 mol / L potassium permanganate, add dilute sulfuric acid to control the pH of the potassium permanganate aqueous solution to 1 - 2, and place it in a constant temperature ultrasonic water bath at 60 °C for 30 min. Then, wash it with ethanol and deionized water respectively until the pH is 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 the electroplating solution.

[0077] (3) Transfer the electroplating solution into a 50 mL electrolytic cell. Using the pretreated carbon cloth as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet as the counter electrode, and a saturated calomel electrode 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 performs electrodeposition for 10 min to prepare layered cobalt-manganese double metal hydroxide. The substance obtained by electrodeposition using this three-electrode system is denoted as Co2Mn1-LDH. After preparation, the carbon cloth electrode loaded with Co2Mn1-LDH is thoroughly cleaned with deionized water, and then dried in an oven at 60 °C for 12 h.

[0078] Comparative Example 5

[0079] This comparative example provides layered cobalt-manganese double metal hydroxide with a Co / Mn molar ratio of 1:1. The preparation method is as follows:

[0080] (1) Cut the carbon cloth into circular pieces with a diameter of 12 mm, place them in an aqueous solution of potassium permanganate with a concentration of 0.5 mol / L, add dilute sulfuric acid to control the pH of the potassium permanganate aqueous solution to 1-2, and place it in a constant temperature ultrasonic water bath at 60 °C for 30 min. Then, wash it with ethanol and deionized water respectively until the pH is 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) Transfer the electroplating solution to a 50 mL electrolytic cell. Use the pretreated carbon cloth as the working electrode, a 10 mm×10 mm×0.2 mm platinum sheet as the counter electrode, and a saturated calomel electrode 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 is electro-deposited for 10 min to prepare a layered cobalt-manganese double metal hydroxide. The substance obtained by electro-deposition using this three-electrode system is denoted as Co1Mn1-LDH. After preparation, thoroughly wash the carbon cloth electrode loaded with Co1Mn1-LDH with deionized water, and then dry it in an oven at 60 °C for 12 h.

[0083] Comparative Example 6

[0084] This comparative example provides a layered cobalt-manganese double metal hydroxide with a Co / Mn molar ratio of 1:2. The preparation method is as follows:

[0085] (1) Cut the carbon cloth into circular pieces with a diameter of 12 mm, place them in an aqueous solution of potassium permanganate with a concentration of 0.5 mol / L, add dilute sulfuric acid to control the pH of the potassium permanganate aqueous solution to 1-2, and place it in a constant temperature ultrasonic water bath at 60 °C for 30 min. Then, wash it with ethanol and deionized water respectively until the pH is 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) Transfer the electroplating solution into a 50 mL electrolytic cell. Using the pretreated carbon cloth as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, in a constant temperature water bath at 30 °C, under a constant potential of -1.0 V (vs. SCE), the electroplating system performs electrodeposition for 10 min to prepare layered cobalt-manganese bimetallic hydroxide. The substance obtained by electrodeposition using this three-electrode system is denoted as Co1Mn2-LDH. After preparation, the carbon cloth electrode loaded with Co1Mn2-LDH is thoroughly cleaned with deionized water and then dried in an oven at 60 °C for 12 h.

[0088] Comparative Example 7

[0089] This comparative example provides layered cobalt-manganese bimetallic hydroxide with a Co / Mn molar ratio of 1:4. The preparation method is as follows:

[0090] (1) Cut the carbon cloth into circular pieces with a diameter of 12 mm, place them in an aqueous solution of 0.5 mol / L potassium permanganate, add dilute sulfuric acid to control the pH of the potassium permanganate aqueous solution to 1 - 2, and place it in a constant temperature ultrasonic water bath at 60 °C for 30 min. Then, wash it with ethanol and deionized water respectively until the pH is 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 mmol) of MnSO4 in 30 mL of deionized water to obtain the electroplating solution.

[0092] (3) Transfer the electroplating solution into a 50 mL electrolytic cell. Using the pretreated carbon cloth as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, in a constant temperature water bath at 30 °C, under a constant potential of -1.0 V (vs. SCE), the electroplating system performs electrodeposition for 10 min to prepare layered cobalt-manganese bimetallic hydroxide. The substance obtained by electrodeposition using this three-electrode system is denoted as Co1Mn4-LDH. After preparation, the carbon cloth electrode loaded with Co1Mn4-LDH is thoroughly cleaned with deionized water and then dried in an oven at 60 °C for 12 h.

[0093] Comparative Example 8

[0094] This comparative example provides layered cobalt-manganese bimetallic hydroxide with a Co / Mn molar ratio of 1:5. The preparation method is as follows:

[0095] (1)Cut the carbon cloth into circular pieces with a diameter of 12 mm, place them in an aqueous solution of potassium permanganate with a concentration of 0.5 mol / L, add dilute sulfuric acid to control the pH of the potassium permanganate aqueous solution to 1 - 2, and place it in a constant-temperature ultrasonic water bath at 60 °C for 30 min. Then, wash it with ethanol and deionized water respectively until the pH is 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)Transfer the electroplating solution to a 50 mL electrolytic cell. Use the pretreated carbon cloth as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet as the counter electrode, and a saturated calomel electrode 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 is electro-deposited for 10 min to prepare a layered cobalt-manganese double metal hydroxide. The substance obtained by electro-deposition using this three-electrode system is denoted as Co1Mn5-LDH. After preparation, thoroughly wash the carbon cloth electrode loaded with Co1Mn5-LDH with deionized water, and then dry it in an oven at 60 °C for 12 h.

[0098] Comparative Example 9

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

[0100] (1)Cut the carbon cloth into circular pieces with a diameter of 12 mm, place them in an aqueous solution of potassium permanganate with a concentration of 0.5 mol / L, add dilute sulfuric acid to control the pH of the potassium permanganate aqueous solution to 1 - 2, and place it in a constant-temperature ultrasonic water bath at 60 °C for 30 min. Then, wash it with ethanol and deionized water respectively until the pH is 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)Transfer the electroplating solution to a 50 mL electrolytic cell. Use the pretreated carbon cloth as the working electrode, a 10 mm × 10 mm × 0.2 mm platinum sheet as the counter electrode, and a saturated calomel electrode 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 is electro-deposited for 10 min to prepare a cobalt hydroxide cathode material. The substance obtained by electro-deposition using this three-electrode system is denoted as Co(OH)2. After preparation, thoroughly wash the carbon cloth electrode loaded with Co(OH)2 with deionized water, and then dry it in an oven at 60 °C for 12 h.

[0103] Comparative Example 10

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

[0105] (1) Cut the carbon cloth into circular pieces with a diameter of 12 mm, place them in an aqueous solution of potassium permanganate with a concentration of 0.5 mol / L, add dilute sulfuric acid to control the pH of the potassium permanganate aqueous solution to 1-2, and place it in a constant-temperature ultrasonic water bath at 60 °C for 30 min. Then, wash it with ethanol and deionized water until the pH is 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) Transfer the electroplating solution to a 50 mL electrolytic cell. Using the pretreated carbon cloth as the working electrode, a 10 mm×10 mm×0.2 mm platinum sheet as the counter electrode, and a saturated calomel electrode 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 is electro-deposited for 10 min to prepare a manganese hydroxide cathode material. The substance obtained by electro-deposition using this three-electrode system is denoted as Mn(OH)2. After preparation, the carbon cloth electrode loaded with Mn(OH)2 is thoroughly washed with deionized water, and then dried in an oven at 60 °C for 12 h.

[0108] The materials prepared in Example 1 and Comparative Examples 1-10 are used as the cathode materials of zinc-ion batteries in zinc-ion batteries: respectively assemble the above-mentioned carbon cloth cathodes loaded with electro-deposited substances, zinc foil anodes, and glass fiber filter paper diaphragms into aqueous zinc-ion secondary batteries, and the electrolyte is an aqueous solution of 2 mol / L ZnSO4 and an aqueous solution of 0.1 mol / L MnSO4. The assembled full cells are denoted as Cell 1 and Cells D1, D2, D3, D4, D5, D6, D7, D8, D9, D10.

[0109] Perform performance tests on the above-mentioned aqueous zinc-ion secondary batteries, 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] As can be seen from Table 1, the aqueous zinc-ion secondary battery assembled with Co1Mn3-LDH prepared in the present invention has a discharge specific capacity at a current density of 2 A g -1 and a capacity retention rate after 1000 charge-discharge cycles of 132 mAh g -1 and 98%, respectively, both higher than those of the batteries assembled with other cathodes.

[0112] Example 1 was compared with Comparative Examples 1 to 8, in which the ratios of Co and Mn were different, while in Comparative Examples 9 and 10, Mn and Co were not introduced respectively. The Mn / Co system can induce the oxidative deposition of Mn in the electrolyte to MnO2, and the reversible dissolution / deposition between Mn and MnO2 and the co-insertion / de-insertion reaction of residual MnO2 with H / Zn occur during subsequent charge-discharge cycles, thereby contributing to the charge-discharge capacity. The different Mn / Co ratios in Comparative Examples 1-8 will affect the oxidative deposition energy barrier of Mn, unable to fully utilize Mn in the electrolyte, and resulting in the generation of more manganese-based by-products, which affect the battery discharge capacity and charge-discharge cycle life. Co1Mn3-LDH can reduce the oxidative deposition energy barrier of Mn, promote the oxidative deposition of more Mn in the electrolyte to MnO2, and MnO2, as an active material, undergoes the reversible dissolution / deposition between Mn and MnO2 and the co-insertion / de-insertion reaction of residual MnO2 with H / Zn during the charge-discharge process, achieving the purpose of good rate capacity and cycle performance. 2+ oxidatively deposits to MnO2, and during subsequent charge-discharge cycles, Mn 2+ undergoes reversible dissolution / deposition with MnO2 and the H + / Zn 2+ co-insertion / de-insertion reaction, thus contributing to the charge-discharge capacity. The different Mn / Co ratios in Comparative Examples 1-8 will affect the oxidative deposition energy barrier of Mn, unable to fully utilize Mn in the electrolyte 2+ , and resulting in the generation of more manganese-based by-products, which affect the battery discharge capacity and charge-discharge cycle life. Co1Mn3-LDH can reduce the oxidative deposition energy barrier of Mn 2+ , promote the oxidative deposition of more Mn in the electrolyte 2+ to MnO2, and MnO2, as an active material, undergoes the reversible dissolution / deposition between Mn 2+ and MnO2 and the H 2+ / Zn + co-insertion / de-insertion reaction of residual MnO2, achieving the purpose of good rate capacity and cycle performance. 2+

[0113] In summary, as the cathode material of the aqueous zinc-ion secondary battery, the layered cobalt-manganese double metal hydroxide (Co1Mn3-LDH) of the present invention oxidizes Mn in the electrolyte to MnO2 and deposits it on the surface of Co 2+ Mn x -LDH during the full battery charging process. During subsequent charge-discharge processes, the reversible dissolution / deposition reaction between Mn y and MnO2 occurs, realizing a 2e transfer reaction, and the co-insertion / de-insertion reaction of residual MnO2 with H 2+ / Zn + also occurs, achieving the purpose of high rate capacity. Co 2+ Mn x -LDH can reduce the oxidative deposition energy barrier of Mn y , promote the stable progress of the dissolution / deposition reaction of MnO2, and thus realize the stable charge-discharge cycle of the battery. 2+

[0114] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the inventive concept, several modifications and improvements can be made, and these all belong to the protection scope of the present invention.

Claims

1. A layered cobalt-manganese bimetallic hydroxide, characterized in that, The layered cobalt-manganese double metal hydroxide is a two-dimensional layered material with cobalt-manganese hydroxide as the layer board; the layered cobalt-manganese double metal hydroxide is denoted as Co x Mn y -LDH, and the molar ratio of Co to Mn is 1:

3.

2. The preparation method of the layered cobalt-manganese bimetallic hydroxide according to claim 1, characterized in that, It includes the following steps: (1) Pretreat the carbon cloth to obtain the pretreated carbon cloth; (2) Dissolve cobalt salt and manganese salt in a solvent to obtain an electroplating solution; (3) Place the electroplating solution obtained in step (2) in an electrolytic cell, use the pretreated carbon cloth obtained in step (1) as the working electrode, and prepare layered cobalt-manganese bimetallic hydroxide by electro-deposition in a three-electrode manner.

3. The preparation method according to claim 2, characterized in that, Step (1) is specifically: Place the carbon cloth in an aqueous potassium permanganate solution, adjust the pH to 1-2, then perform ultrasonic treatment under heating conditions, and then wash until the pH is 7 to obtain the pretreated carbon cloth.

4. The preparation method according to claim 3, characterized in that, The concentration of the aqueous potassium permanganate solution is 0.1 mol / L - 0.5 mol / L; The heating temperature is 60°C - 80°C, and the ultrasonic treatment time is 30 min - 60 min.

5. The preparation method 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 preparation method according to claim 2, characterized in that, Step (3) is specifically: Place the electroplating solution obtained in step (2) in an electrolytic cell, use the pretreated carbon cloth obtained in step (1) as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode, and prepare layered cobalt-manganese bimetallic hydroxide by electro-deposition under a constant potential condition in a three-electrode manner.

7. According to the preparation method described in claim 6, wherein the constant potential is -1.2V (vs.SCE) - -0.8V (vs.SCE); The electro-deposition temperature is 30°C - 60°C, and the electro-deposition time is 5 min - 15 min.

8. Application of the layered cobalt-manganese bimetallic hydroxide described in claim 1 or the layered cobalt-manganese bimetallic hydroxide prepared by the preparation method described in any one of claims 2-7 in a zinc ion battery.

9. A positive electrode of an aqueous zinc-ion secondary battery, characterized in that, It includes the layered cobalt-manganese bimetallic hydroxide described in claim 1 or the layered cobalt-manganese bimetallic hydroxide prepared by the preparation method described in any one of claims 2-7.

10. An aqueous zinc ion secondary battery, characterized in that: It includes the positive electrode of the aqueous zinc ion secondary battery described in claim 9.

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