Broccoli-shaped positive electrode material with ultrahigh specific capacitance and preparation method
The "brocco"-shaped Cl-NiMn LDH electrode material was prepared by solvothermal method, which solved the specific capacitance enhancement and nanosheet agglomeration of nickel-manganese bimetal hydroxide electrodes, and achieved high specific capacitance, low resistance and stable electrochemical performance, simplified the preparation process and reduced costs.
Patent Information
- Application Number
- CN202510664732.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-22
- Publication Date
- 2025-08-12
AI Technical Summary
In the prior art, the specific capacitance of the nickel-manganese bimetal hydroxide supercapacitor electrode is not significantly improved, the preparation steps are complicated, and the nanosheets are prone to agglomeration and have poor conductivity, which affects its performance as an electrode material for commercial applications.
The "brucco"-shaped Cl-NiMn LDH electrode material was prepared by solvothermal method. By introducing Cl-ion-replacement partial OH- to form chlorine-oxygen bonds, controlling the layer spacing, and forming a bridge on the main layer oxygen atoms, combining partial replacement of manganese elements and NH4+ to provide a weak acidic environment, inhibiting the growth of specific crystal surfaces, forming a nanoflower-like structure, increasing specific surface area and wettability.
The specific capacitance of the electrode material is significantly improved, the charge transfer resistance is reduced, the conductivity and stability is enhanced, the preparation process is simplified, the cost is reduced, and the electrode material with high specific capacitance and long cycle life is achieved.
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Figure CN120473339A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of electrochemical positive electrode material preparation, and specifically relates to a "broccoli"-shaped positive electrode material with ultra-high specific capacitance and a preparation method thereof. Background Art
[0002] Double hydroxides (LDHs) have a typical layered structure consisting of host layer cations (divalent or trivalent metal ions) and guest layer anions (OH - 、CO3 2- 、NO3 - Composed of materials such as 2D layers (e.g., ionic species, interlamellar spacing, and size and morphology), these materials, as typical two-dimensional layered materials, possess unique structural and design properties and are widely used in catalysis, energy, biosensors, adsorption, and pharmaceuticals, promising promising applications. In recent years, with the increasing demand for new energy sources, transition metal hydroxides have been extensively studied as electrode materials to improve the overall performance of energy storage devices.
[0003] For transition metal compound supercapacitor electrodes, nickel manganese double hydroxide has a high theoretical specific capacitance but has problems such as poor conductivity and easy agglomeration. To address the above problems, Liu et al. (reference Electrochimica Acta, 460 (2023), 142623) composited NiMn LDH with highly conductive silver nanowires to prepare NiMnLDH / Ag NWs capacitor electrodes with a specific capacitance of up to 1436.30 F / g at a current density of 2 A / g.
[0004] Cheng et al. (reference Electrochimica Acta, 429 (2022) 141039) prepared NiMn-LDH / Ni3S2 by sulfurizing NiMnLDH, which has a high energy density of 49Wh / kg.
[0005] However, the above methods all have the following problems: 1. The improvement in the specific capacitance of nickel-manganese materials is not obvious and the preparation steps are cumbersome, which limits the commercial application of nickel-manganese double hydroxide as supercapacitor electrodes; 2. Although the conductivity of NiMn LDH is improved, the agglomeration problem of the prepared NiMn LDH nanosheets has not been fundamentally solved.
[0006] Therefore, improving the conductivity and stability of nickel-manganese double hydroxide, solving the problem of nanosheet agglomeration, and fully exposing the redox reaction sites of active substances to prepare electrode materials with high specific capacity and long cycle life are current research hotspots. Summary of the Invention
[0007] In order to overcome the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a "broccoli"-shaped positive electrode material with ultra-high specific capacitance and a preparation method, which can effectively realize the regulation of the interlayer spacing of transition metal double hydroxides and the preparation of highly wettable "broccoli"-shaped electrode materials. The "broccoli"-shaped electrode material has the characteristics of large specific surface area, fully exposed active sites, good contact with the electrolyte, and low charge transfer resistance.
[0008] In order to achieve the above object, the technical solution adopted by the present invention is:
[0009] A method for preparing a "broccoli"-shaped positive electrode material with ultra-high specific capacitance comprises the following steps:
[0010] (1) Pretreatment of nickel foam (NF):
[0011] The nickel foam was placed in dilute hydrochloric acid to remove nickel oxide on the surface, and then ultrasonically washed with anhydrous ethanol and deionized water for several times, and dried for later use.
[0012] (2) Preparation of Cl-NiMn LDH / NF:
[0013] MnCl2·4H2O, Ni(NO3)2·6H2O, urea (CO(NH2)2), and NH4Cl were weighed separately and dissolved in a mixed solution of water and ethanol and stirred thoroughly to obtain a mixed solution; the mixed solution and the pretreated nickel foam were transferred to a high-pressure reactor for a solvothermal reaction. After cooling, the sample was taken out and washed several times with deionized water and ethanol and dried to obtain a "broccoli"-shaped positive electrode material with ultra-high specific capacitance.
[0014] Preferably, in step (1), the size of the nickel foam is 1.5-4 cm×1.5-4 cm×1 mm.
[0015] Preferably, in step (1), the dilute hydrochloric acid is obtained by diluting concentrated hydrochloric acid, with a volume ratio of V (concentrated hydrochloric acid): V (water) = 1:9; and the ultrasonic time is 10 to 30 minutes, which is used to remove oxides on the surface of the nickel foam.
[0016] Preferably, in step (1), the ethanol and deionized water are alternately washed 3 to 6 times, and the ultrasonic time for each time is 10 to 15 minutes to remove surface grease.
[0017] Preferably, in step (1), the pretreated nickel foam is dried at a temperature of 50 to 60° C. for 10 to 12 hours to remove residual moisture and ethanol.
[0018] Preferably, in step (2), the molar ratio of MnCl2·4H2O, Ni(NO3)2·6H2O, urea (CO(NH2)2), and NH4Cl is 1-4:1-6:2-8:4-6, serving as Mn source, Ni source, precipitant, and Cl source, respectively.
[0019] Preferably, in step (2), the volume ratio of deionized water to anhydrous ethanol in the water-alcohol mixed solution is 4:1 to 2:1.
[0020] Preferably, in step (2), the solvent thermal reaction temperature is 100-120° C., the holding time is 2-6 h, and “broccoli”-shaped Cl-NiMn LDH grows on the surface of the nickel foam.
[0021] Preferably, in step (2), the ethanol and deionized water are alternately washed 3 to 6 times, and the drying time is 10 to 12 hours.
[0022] A "broccoli"-shaped positive electrode material with ultra-high specific capacitance is in the form of "broccoli" growing on the surface of a nickel foam skeleton. It has a three-dimensional structure and good wettability with the electrolyte. The nanoflower balls on the surface are connected to the nanorods inside, and the nanorods are gathered in one plant and connected to the conductive current collector nickel foam base. The surface nanoflower redox reaction is constructed, and the nanorods serve as a three-dimensional structure for fast electron transfer bridges, realizing rapid charge transfer between surface redox energy storage and the conductive current collector base, greatly reducing the charge transfer resistance and improving the electrochemical performance of the NiMn LDH electrode material.
[0023] The "broccoli"-shaped positive electrode material with ultra-high specific capacitance is used for the positive electrode of supercapacitors, and the asymmetric supercapacitor device composed of the "broccoli"-shaped positive electrode material and the activated carbon negative electrode material can be used in new energy vehicles, rail transportation, smart wearables, electronic medical devices and other fields.
[0024] Beneficial effects of the present invention:
[0025] 1. The present invention introduces Cl - Replace part of OH - , and forms chlorine-oxygen bonds with the oxygen atoms in the main layer, playing a "bridging" role between the main layers, providing a fast transfer channel for the transmission and transfer of electrons between the main layers, and achieving a huge improvement in electrochemical performance.
[0026] 2. The present invention introduces manganese element to realize the preparation of double metal hydroxide electrode material, which has high valence and multivalence (2 + →3 + →4 + ) partially replaces the nickel atoms in the main layer (2 + →3 +) position, which can increase the charge storage by 2 times compared with nickel during the redox reaction, thereby significantly improving the specific capacitance; in addition, the introduction of high-valent elements to partially replace low-valent elements can not only stabilize the LDH layered structure through electrostatic action but also form positively charged hole carriers, further improving the conductivity, realizing the bimetallic synergistic effect, and improving the electrochemical performance.
[0027] 3. The present invention introduces chloride ions to guide the directional growth of nickel-manganese LDH along the (012) and (110) crystal planes, inhibiting the growth of the (018) and (006) crystal planes. The prepared Cl-NiMn LDH electrode with a "broccoli"-like morphology has a large specific surface area, and clusters of nanoflowers are composed of smaller nanorods. The nanoflowers on the surface greatly expose the redox active sites, thereby improving the specific capacitance of the electrode material. During the charge and discharge process, the Cl-NiMn LDH with a "broccoli"-like morphology maintains a stable structure under the action of electrostatics, and the abundant pores enable the electrolyte to be in more complete contact with the active sites, thereby realizing rapid electron transfer, greatly reducing the ion diffusion resistance, and exhibiting excellent electrochemical performance.
[0028] 4. The preparation method of the present invention is simple. A nickel-manganese double hydroxide electrode material with ultra-high specific capacitance can be prepared by a one-step solvent thermal method. At the same time, the raw materials required for the synthesis are low-cost and easy to obtain. The use of precious metal cobalt salts is avoided, reducing the preparation cost by 20-30%. The preparation method is mild and has a short cycle, avoiding the use of strong bases. The weakly acidic environment provided by the hydrolysis of ammonium ions reduces the overall OH in the solvent. - The content of Cl - Successfully replaced the OH groups between NiMn LDH layers - . BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 (a) and (b) are the cyclic voltammetry (CV) and constant current charge-discharge (GCD) curves of the Cl-NiMn LDH / NF prepared in Example 1 of the present invention, respectively.
[0030] Figure 2 This is a scanning diagram of the Cl-NiMn LDH / NF prepared in Example 1. DETAILED DESCRIPTION
[0031] The present invention will be described in further detail below with reference to the accompanying drawings.
[0032] Example 1
[0033] The preparation method of a "broccoli"-shaped supercapacitor positive electrode Cl-NiMn LDH / NF with ultra-high specific capacitance of this embodiment comprises the following specific steps:
[0034] (1) Prepare a dilute hydrochloric acid solution with a volume ratio of 9:1, place it in a 250 ml volumetric flask and ultrasonicate for 15 minutes.
[0035] (2) Place nickel foam trimmed to a size of 2 cm × 2 cm × 1 mm in a beaker, pour the above-mentioned dilute hydrochloric acid solution into it until the nickel foam is submerged, and ultrasonically clean it for 30 minutes.
[0036] (3) The nickel foam was cleaned alternately with anhydrous ethanol and deionized water for 4 times, with each ultrasonic cleaning time being 10 minutes. Finally, the nickel foam was transferred to an oven at 60°C, dried for 12 hours, and cooled for later use.
[0037] (4) Weigh 0.198 g of MnCl2·4H2O, 0.582 g of Ni(NO3)2·6H2O, 0.48 g of urea, and 0.214 g of NH4Cl into a 100 ml beaker, and add 25 ml of a water-alcohol mixture (V 水 :V 乙醇 =4:1), and magnetically stirred for 20 min to obtain a pink solution.
[0038] (5) The pink solution in step (4) was transferred to a polytetrafluoroethylene liner and a piece of nickel foam pretreated in step (3) was added. The solution was placed in a hydrothermal oven at 110°C for 4 h. After cooling to room temperature, the solution was rinsed alternately with deionized water and anhydrous ethanol for 3 times. The sample was placed in a 60°C forced air drying oven and dried for 12 h to obtain a Cl-NiMn LDH / NF electrode.
[0039] The positive electrode material prepared in Example 1 has a charge specific capacitance that is 4 times higher than that of NiMn LDH at a current density of 1 A / g, and a discharge specific capacitance that is 5 times higher.
[0040] like Figure 1 (a) and (b) show the GCD and CV curves of the Cl-NiMn LDH / NF electrode prepared in Example 1 at different current densities and scan rates, respectively. The GCD charge and discharge curves form an isosceles triangle, indicating good redox reversibility. The CV curve area increases with increasing scan rate, indicating that pseudocapacitance dominates the specific capacity of this electrode material.
[0041] like Figure 2 (a) is a scanning image of the NiMn LDH / NF electrode prepared in Comparative Example 1, which has a wrinkled morphology, a small specific surface area, and few exposed active sites. (b) is a scanning image of the Cl-NiMn LDH / NF electrode prepared in Example 1, which has a "broccoli-like" morphology. The nanospheres on the surface expose more active sites to participate in the redox reaction. The nanorods under the spheres are connected to the base nickel foam, providing a fast charge transfer path.
[0042] Experimental testing
[0043] Preparation of electrode sheets: The mass of the nickel foam before and after the reaction after drying is weighed and recorded as m0 and m1, and the mass difference is Δm, which is the active mass.
[0044] The Cl-NiMn LDH / NF prepared in step (5) was cut into 1 cm×2 cm×1 mm and maintained under a pressure of 10 MPa for 30 s to obtain a Cl-NiMn LDH / NF test electrode.
[0045] The electrochemical performance of the Cl-NiMn LDH / NF test electrode was tested in a three-electrode system, in which the Cl-NiMn LDH / NF test electrode was used as the working electrode, the platinum electrode was used as the counter electrode, and the Hg / HgO electrode was used as the reference electrode.
[0046] Example 2
[0047] (1) Prepare a dilute hydrochloric acid solution with a volume ratio of 9:1, place it in a 250 ml volumetric flask and ultrasonicate for 15 minutes.
[0048] (2) Place nickel foam trimmed to a size of 2 cm × 2 cm × 1 mm in a beaker, pour the above-mentioned dilute hydrochloric acid solution into it until the nickel foam is submerged, and ultrasonically clean it for 30 minutes.
[0049] (3) The nickel foam was cleaned four times with anhydrous ethanol and deionized water alternately, with each ultrasonic cleaning time being 10 min. Finally, the nickel foam was transferred to an oven at 50° C., dried for 12 h, and cooled for later use.
[0050] (4) Weigh 0.396g of MnCl2·4H2O, 1.163g of Ni(NO3)2·6H2O, 0.24g of urea, and 0.324g of NH4Cl into a 100ml beaker, and add 25ml of a water-alcohol mixture (V 水 :V 乙醇 =4:1), and magnetically stirred for 20 min to obtain a pink solution.
[0051] (5) The pink solution in step (4) was transferred to a polytetrafluoroethylene liner and a piece of nickel foam pretreated in step (3) was added. The solution was placed in a hydrothermal oven at 120°C for 6 h. After cooling to room temperature, the solution was rinsed alternately with deionized water and anhydrous ethanol for 3 times. The sample was placed in a 60°C forced air drying oven and dried for 10 h to obtain a Cl-NiMn LDH / NF electrode.
[0052] The Cl-NiMn LDH / NF electrode prepared in this embodiment has the characteristics of a "broccoli"-like morphology, a large number of exposed active sites, good wettability with the electrolyte, a short charge transfer path, and low internal resistance.
[0053] Comparative Example 1
[0054] This comparative example is a method for preparing a supercapacitor positive electrode NiMn LDH / NF of nickel manganese double hydroxide without chloride ion modification, and the specific steps are as follows:
[0055] (1) Weigh 0.198g of MnCl2·4H2O, 0.582g of Ni(NO3)2·6H2O, and 0.48g of urea into a 100ml beaker, and add 25ml of a water-alcohol mixture (V 水 :V 乙醇 =4:1), and magnetically stirred for 20 min to obtain a pink solution.
[0056] (2) The pink solution in step (1) was transferred to a polytetrafluoroethylene liner and a pretreated piece of nickel foam was added. The solution was placed in a hydrothermal oven at 110°C for 4 h. After cooling to room temperature, the solution was rinsed alternately with deionized water and anhydrous ethanol for 3 times. The sample was placed in a 60°C forced air drying oven and dried for 24 h to obtain a NiMn LDH / NF electrode.
[0057] The testing method of the material prepared in Comparative Example 1 is consistent with the testing steps (1)(2)(3) in Example 1.
[0058] Comparative Example 2
[0059] (1) Weigh 0.396g of MnCl2·4H2O, 1.163g of Ni(NO3)2·6H2O, and 0.24g of urea into a 100ml beaker, and add 25ml of a water-alcohol mixture (V 水 :V 乙醇 =4:1), and magnetically stirred for 20 min to obtain a pink solution.
[0060] (2) The pink solution in step (1) was transferred to a polytetrafluoroethylene liner and pretreated nickel foam was added. The solution was placed in a hydrothermal oven at 120°C for 6 h. After cooling to room temperature, the solution was rinsed alternately with deionized water and anhydrous ethanol for 3 times. The sample was placed in a 60°C forced air drying oven and dried for 12 h to obtain a NiMn LDH / NF electrode.
[0061] The present invention introduces Cl into the preparation process of nickel-manganese double hydroxide. - The intercalation forms a chlorine-oxygen bond, providing a "bridge" for interlayer electron transfer; the introduction of NH4 +A weakly acidic environment is provided to etch the nanosheets to form a nanoscale "broccoli"-like morphology, thereby increasing the specific surface area and wettability of the electrode material. The material is used as the working electrode in a three-electrode system test, and a constant current charge-discharge test is performed using 2M KOH as the electrolyte. The discharge specific capacitance is as high as 4656.59F / g at a voltage window of 0-0.5V and a current density of 1A / g. The nickel-manganese electrode material prepared by the one-step hydrothermal method of the present invention has an ultra-high specific capacity, and the preparation method is simple, the raw materials are cheap, and the reaction parameters are easy to control. The present invention provides a new idea and strategy for improving the specific capacity of supercapacitor electrode materials, and is expected to become an ideal supercapacitor positive electrode material with ultra-high energy density.
Claims
1. A method for preparing a "broccoli"-shaped positive electrode material with ultra-high specific capacitance, characterized in that: The following steps are included: Step (1), placing the nickel foam in dilute hydrochloric acid to remove nickel oxide on the surface, and finally ultrasonically washing it with anhydrous ethanol and deionized water for several times, and drying it for later use; Step (2): Weigh MnCl2·4H2O, Ni(NO3)2·6H2O, urea (CO(NH2)2), and NH4Cl respectively, dissolve them in a mixed solution of water and ethanol, and stir them thoroughly to obtain a mixed solution; transfer the mixed solution and the pretreated nickel foam into a high-pressure reactor for a solvothermal reaction; after cooling, take out the sample, wash it several times with deionized water and ethanol, and dry it to obtain a "broccoli"-shaped positive electrode material with ultra-high specific capacitance.
2. The method for preparing a "broccoli"-shaped positive electrode material with ultra-high specific capacitance according to claim 1, characterized in that: In step (1), the size of the nickel foam is 1.5-4 cm×1.5-4 cm×1 mm.
3. The method for preparing a "broccoli"-shaped positive electrode material with ultra-high specific capacitance according to claim 1, characterized in that: In step (1), the dilute hydrochloric acid is obtained by diluting concentrated hydrochloric acid, with a volume ratio of V (concentrated hydrochloric acid): V (water) = 1:9; and the ultrasonic time is 10 to 30 minutes.
4. The method for preparing a "broccoli"-shaped positive electrode material with ultra-high specific capacitance according to claim 1, characterized in that: In step (1), the ethanol and deionized water are alternately washed 3 to 6 times, and the ultrasonic time for each washing is 10 to 15 minutes.
5. The method for preparing a "broccoli"-shaped positive electrode material with ultra-high specific capacitance according to claim 1, characterized in that: In step (1), the pretreated nickel foam is dried at a temperature of 50 to 60° C. for 10 to 12 hours.
6. The method for preparing a "broccoli"-shaped positive electrode material with ultra-high specific capacitance according to claim 1, characterized in that: In step (2), the molar ratio of MnCl2·4H2O, Ni(NO3)2·6H2O, urea (CO(NH2)2), and NH4Cl is 1-4:1-6:2-8:4-6, which serve as Mn source, Ni source, precipitant, and Cl source, respectively.
7. The method for preparing a "broccoli"-shaped positive electrode material with ultra-high specific capacitance according to claim 1, characterized in that: In step (2), the volume ratio of deionized water to anhydrous ethanol in the water-alcohol mixed solution is 4:1 to 2:
1.
8. The method for preparing a "broccoli"-shaped positive electrode material with ultra-high specific capacitance according to claim 1, characterized in that: In step (2), the solvent thermal reaction temperature is 100-120° C., the holding time is 2-6 hours, and a “broccoli”-shaped Cl-NiMn LDH grows on the surface of the nickel foam; In step (2), the ethanol and deionized water are alternately washed 3 to 6 times, and the drying time is 10 to 12 hours.
9. A "broccoli"-shaped positive electrode material with ultra-high specific capacitance prepared by the method according to any one of claims 1 to 8, characterized in that: It appears as "broccoli" growing on the surface of the nickel foam skeleton, with a three-dimensional structure and good wettability with the electrolyte. The nanoflower balls on the surface are connected to the nanorods inside, and the nanorods are gathered in one plant and connected to the conductive current collector nickel foam base; the surface nanoflower redox reaction is constructed, and the three-dimensional structure of the nanorods serves as a fast electron transfer bridge, realizing the rapid charge transfer between the surface redox energy storage and the conductive current collector base, greatly reducing the charge transfer resistance and improving the electrochemical performance of the NiMn LDH electrode material.
10. Application of a "broccoli"-shaped positive electrode material with ultra-high specific capacitance prepared by the method according to any one of claims 1 to 8, characterized in that: The "broccoli"-shaped positive electrode material with ultra-high specific capacitance is used in the positive electrode of supercapacitors, and the asymmetric supercapacitor device composed of the "broccoli"-shaped positive electrode material and the activated carbon negative electrode material can be used in the fields of new energy vehicles, rail transportation, smart wearables, and electronic medical devices.