CN110648861B

CN110648861B - A method for in situ growth of braided porous NiCo2O4 nanosheets

Info

Publication number: CN110648861B
Application number: CN201910867049.XA
Authority: CN
Inventors: 刘沛静; 辛福恩
Original assignee: Shaanxi University of Technology
Current assignee: Shaanxi University of Technology
Priority date: 2019-09-12
Filing date: 2019-09-12
Publication date: 2021-10-15
Anticipated expiration: 2039-09-12
Also published as: CN110648861A

Abstract

The invention discloses a method for in-situ growth of braided porous NiCo ₂ O ₄ nanosheets. First, a layer of "fuzzy" pores with anisotropic structure is uniformly grown on a nickel foam substrate through a low temperature oil bath, and then combined with a high temperature By hydrothermal method, anisotropic NiCo ₂ O ₄ nanowires are deposited and grown in these channels, and finally, under the environment of high temperature and high pressure, the nanowires are intertwined to form an in-situ self-woven structure. This self-made "mat"-like structure not only has the characteristics of nanosheets, but also provides a large number of active sites for the growth of active materials. Improving the stability of the electrode material structure can improve the service life of the material and broaden the application of the electrode material in the field of energy storage. The invention has the advantages of simple process, short production period and easy control, and provides a new idea for the research in the field of pseudocapacitor material structure design.

Description

In-situ growth of braided porous channel NiCo2O4Method of nanosheet

Technical Field

The invention belongs to the technical field of super capacitors, and particularly relates to an in-situ grown braided porous NiCo₂O₄A method of nanoplatelets.

Background

In recent years, transition metal oxides have been widely studied as electrode materials for the preparation of high energy density pseudocapacitive supercapacitors. This is because the transition metal oxide has multiple valence states of the element, which can provide a higher specific capacitance (Csp) than the conductive polymer. Wherein, NiCo is used₂O₄Is most commonly used because of spinel nickel cobalt ore (NiCo)₂O₄) Has high theoretical capacitance (1370F g 1), environment-friendly property, better electronic conductivity and high electrochemical activity (Ni)²⁺/Ni³⁺And Co²⁺/Co³⁺Redox couple), etc.

As part of a full supercapacitor device, the electrode material is considered to be a key component affecting the electrochemical performance of the supercapacitor. Therefore, in terms of improving the performance of the pseudo capacitor, the structural design of the electrode material is an effective means for improving the capacitive performance of the device. With respect to the structural morphology of the material, the electrode material having a hierarchical/porous structure can increase the specific surface area, improve the contact area between the electrode and the electrolyte, shorten the diffusion path of electrolyte ions, and enhance the structural stability. Three-dimensional (3D) structures may exhibit better cycling performance compared to one-dimensional (1D) and two-dimensional (2D) structures, as 3D features are advantageous to accommodate structural changes and efficient ion and electron diffusion.

NiCo with the shapes of nano thin slices, nano particles, nano needles, nano flowers, nano wires, nano rods and the like prepared by the predecessors before research₂O₄There are no 3D structures, but they are fundamentally assembled into 3D nanoflowers by 2D nanosheets only, or into 3D echinoid structures by 1D nanowires. No studies have been reported on a binder-free electrode material having characteristics such as an excellent conductivity of a 1D structure, a growth site having a rich 2D structure, and a spatial structure having an excellent 3D structure.

Disclosure of Invention

The invention aims to provide an in-situ grown braided porous channel NiCo₂O₄A method of nanoplatelets.

Aiming at the purposes, the technical scheme adopted by the invention comprises the following steps:

1. at normal temperature, ultrasonically dipping a foamed nickel substrate in 1-3 mol/L acetone aqueous solution for 20-40 minutes, and then ultrasonically dipping in 5-10% hydrochloric acid for 20-40 minutes; and after soaking, repeatedly cleaning the foamed nickel substrate to be neutral by using absolute ethyl alcohol and deionized water, and drying the cleaned foamed nickel substrate in vacuum at the temperature of 80-100 ℃.

2. Soaking the foamed nickel substrate subjected to vacuum drying in the step 1 in a pretreatment solution, and heating and reacting for 30-120 minutes at 80-110 ℃, wherein the pretreatment solution contains 0.3-0.5 mmol/L of Ni (NO)₃)₂、0.5～1 mmol/L Co(NO₃)₂、1.0～1.5mmol/L NH₄NO₃And a 1-5% volume concentration aqueous solution of dimethyl sulfoxide; and after the reaction is finished, repeatedly ultrasonically cleaning the foamed nickel substrate by using deionized water and absolute ethyl alcohol, and drying to obtain the pretreated foamed nickel substrate.

3. After the pretreatment of the step 2Immersing the foamed nickel substrate in a solution containing 0.5-1 mmol/L Co (NO)₃)₂、0.3～0.5 mmol/L NiCl₂0.2-0.4 mmol/L hexadecyl trimethyl ammonium bromide and 1-1.5 mmol/L urea, carrying out hydrothermal reaction at 80-110 ℃ for 5-8 hours, and ultrasonically cleaning with absolute ethyl alcohol and deionized water after the reaction is finished, and drying.

4. Annealing the foamed nickel substrate obtained in the step 3 at 250-400 ℃ for 1-4 hours in an air atmosphere to obtain braided porous NiCo₂O₄Nanosheets.

In the step 1, at normal temperature, preferably, the foamed nickel substrate is ultrasonically immersed in 2mol/L acetone aqueous solution for 30 minutes, and then ultrasonically immersed in hydrochloric acid with the mass concentration of 7-8% for 30 minutes, wherein the ultrasonic power is 100W.

In the step 2, preferably, the foamed nickel substrate dried in vacuum in the step 1 is soaked in the pretreatment solution, and is heated and reacted for 60 to 90 minutes at 90 to 100 ℃.

In the step 2, the pretreatment solution preferably contains 0.35 to 0.40mmol/L of Ni (NO)₃)₂、0.7～0.8 mmol/L Co(NO₃)₂、1.12～1.13mmol/L NH₄NO₃And 2-3% volume concentration dimethyl sulfoxide aqueous solution.

In the step 3, preferably, the foamed nickel substrate pretreated in the step 2 is immersed in a solution containing 0.7 to 0.8mmol/L Co (NO)₃)₂、0.35～0.40mmol/L NiCl₂0.3 to 0.4mmol/L hexadecyl trimethyl ammonium bromide and 1.3 to 1.5mol/L urea, and carrying out hydrothermal reaction at 90 to 100 ℃ for 6 to 7 hours.

In the step 4, the acicular nickel-cobalt bimetal hydroxide foamed nickel substrate grown in the step 3 is preferably annealed for 2-3 hours at 300-320 ℃ in an air atmosphere, and the temperature rise rate of the annealing is 1-5 ℃/min.

The invention has the following beneficial effects:

1. NiCo grown in situ according to the invention₂O₄The use of no adhesive is beneficial to improving the conductivity of the electrode material, and meanwhile, the generation of 'dead volume' capacitance is reduced, and the energy storage device is easy to process.

2. The invention relates to a self-woven mat-shaped structure NiCo through in-situ growth₂O₄The nano-sheets not only have the characteristics of nano-wires, but also have the characteristics of nano-sheets, provide a large number of active sites for the growth of active materials, and simultaneously, the nano-sheets are made of NiCo₂O₄The nanowires are formed in a linear arrangement, and a large number of gaps exist between the wires, so that a transmission path is shortened for the transmission of ions in the electrolyte. Moreover, the mat-shaped structure formed by interweaving the nano sheets can effectively relieve the volume expansion problem of the electrode material in the charging and discharging process, remarkably improve the structural stability of the electrode material, prolong the service life of the material and widen the application of the electrode material in the field of energy storage.

3. The invention prepares NiCo with common characteristics of one-dimensional nano-wire, two-dimensional nano-sheet and three-dimensional self-weaving structure for the first time₂O₄The method has the advantages of simple process, short production period and easy control, and provides a new idea for the research in the field of pseudocapacitance material structure design.

Drawings

FIG. 1 is a scanning electron micrograph of a foamed nickel substrate after pretreatment in example 1 (wherein (b) is a partial enlarged view of (a)).

FIG. 2 shows a woven porous NiCo channel obtained in example 1₂O₄Scanning electron micrographs of the nanoplatelets (where (b) is a partial magnified view of (a)).

FIG. 3 shows a woven porous NiCo channel obtained in example 1₂O₄X-ray diffraction pattern of the nanoplatelets.

FIG. 4 shows a braided porous channel NiCo obtained in example 1₂O₄Cycling stability curve of the nanoplatelets.

Detailed Description

The present invention will be described in further detail with reference to the following drawings and examples, but the scope of the present invention is not limited to the following examples.

Example 1

1. Cutting the foamed nickel into square sheets with the specification of 1cm multiplied by 0.25cm, then placing the cut foamed nickel in 2mol/L acetone water solution for ultrasonic immersion for 30min at normal temperature, and then placing the foamed nickel in hydrochloric acid with the mass concentration of 7% for immersion for 30min, wherein the ultrasonic power is 100W; after the impregnation, the foam nickel is repeatedly cleaned to be neutral by using absolute ethyl alcohol and deionized water, and the cleaned foam nickel is dried for 1 hour in a vacuum drying oven at the temperature of 90 ℃.

2. Soaking the foamed nickel dried in the step 1 in 20mL of pretreatment solution containing 0.375mmol/L Ni (NO)₃)₂、0.75mmol/L Co(NO₃)₂、1.125mmol/L NH₄NO₃And heating the aqueous solution of dimethyl sulfoxide with the volume concentration of 2.5% in an oil bath at 90 ℃ for reaction for 60min, repeatedly ultrasonically cleaning the sample for several times by using deionized water and absolute ethyl alcohol after the reaction is finished, and drying the sample in an oven at 60 ℃ for 2h to obtain the pretreated foamed nickel.

3. Immersing the foamed nickel substrate pretreated in the step 2 in 20mL of solution containing 0.75mmol/L Co (NO)₃)₂、 0.375mol/L NiCl₂The preparation method comprises the following steps of standing in a reaction kettle with a polytetrafluoroethylene lining and an aqueous solution of 0.3mol/L hexadecyl trimethyl ammonium bromide and 1.35mol/L urea under a closed condition at 100 ℃ for hydrothermal reaction for 6 hours, washing the reaction product with absolute ethyl alcohol and deionized water in a 40W ultrasonic cleaner for 5min each time after the reaction is finished, repeatedly washing the reaction product for 3 times, and drying the reaction product in an oven at 80 ℃ for 3 hours at constant temperature.

4. Putting the sample obtained in the step 3 into a tube furnace, heating to 300 ℃ at the speed of 1 ℃/min in the air atmosphere, preserving heat for 2h, carrying out high-temperature annealing treatment on the sample, taking out the sample, cleaning the sample for 5min each time in a 40W ultrasonic cleaning instrument by using deionized water and absolute ethyl alcohol after the sample is recovered to the room temperature, repeatedly cleaning the sample for 3 times, then putting the cleaned sample into an oven at the temperature of 80 ℃ and drying the cleaned sample for 3h to obtain the braided porous NiCo with porous channels₂O₄Nanosheets.

For the braided porous NiCo channel obtained above₂O₄SEM representation is carried out on the nanosheets, and the results are shown in the figures 1-2. As can be seen from FIG. 1, a Ni-Co precursor with a villous three-dimensional porous structure is uniformly grown on the surface of the foamed nickel, and FIG. 2 is compared with the sample surface of FIG. 1 and uniformly distributedThe nickel cobalt oxide with a sheet structure is further clearly observed from the enlargement of fig. 2(b), the nano sheets are composed of orderly arranged nano rods (needles), and due to the three-dimensional porous channel structure grown on the surface of the pretreated nickel foam, the nucleation and growth angles of the combined product have anisotropic characteristics under the reaction conditions of high pressure and high temperature, so that the nano needle-shaped nickel cobalt oxide is generated and is interwoven with each other to form a porous channel structure similar to a woven mat shape. The pore size of 50-200 nm can be estimated from the partial enlarged view and belongs to the ultra-large pore. In order to confirm the phase of the sample, XRD characterization was performed, and the results are shown in fig. 3. As can be seen from FIG. 3, four characteristic diffraction peaks, with NiCo, appear at 31 °, 36.5 °, 59.3 ° and 65.1 ° 2 θ₂O₄The characteristic peaks of (JCPDS: 87-0712) are consistent, and the rest three characteristic diffraction peaks of 44.5 degrees, 51.8 degrees and 76.4 degrees are consistent with the foam nickel. The electrochemical cycling stability was further tested and the results are shown in figure 4. As shown in fig. 4, at 3A g^-1At a current density of 85%, the initial capacity retention of the sample was 85%, compared to the literature (Electrochimica Acta,2013,106: 226-234; Rsc Advances,2015,5:33146-33154), the braided porous channel NiCo₂O₄The chemical structure is stable. The research shows that the structure can obviously improve the stability of the material and the service life of the material, and broadens the application of the material in the field of energy storage.

Example 2

1. This step is the same as step 1 of example 1.

2. Soaking the foamed nickel dried in the step 1 in 20mL of pretreatment solution containing 0.375mmol/L Ni (NO)₃)₂、0.75mmol/L Co(NO₃)₂、1.125mmol/L NH₄NO₃And heating the aqueous solution of dimethyl sulfoxide with the volume concentration of 2.5% in an oil bath at 100 ℃ for 30min for reaction, repeatedly ultrasonically cleaning the sample for several times by using deionized water and absolute ethyl alcohol after the reaction is finished, and drying the sample in an oven at 60 ℃ for 2h to obtain the pretreated foamed nickel.

3. Pretreating step 2The treated foam nickel substrate is soaked in 20mL of solution containing 0.75mmol/L Co (NO)₃)₂、 0.375mol/L NiCl₂The preparation method comprises the following steps of standing in a reaction kettle with a polytetrafluoroethylene lining and an aqueous solution of 0.3mol/L hexadecyl trimethyl ammonium bromide and 1.35mol/L urea under a closed condition at 100 ℃ for hydrothermal reaction for 8 hours, washing the reaction product with absolute ethyl alcohol and deionized water in a 40W ultrasonic cleaner for 5min each time after the reaction is finished, repeatedly washing the reaction product for 3 times, and drying the reaction product in an oven at 80 ℃ for 3 hours at constant temperature.

4. The procedure was the same as that of example 1, step 4, to obtain a braided porous NiCo channel₂O₄Nanosheets.

Example 3

1. This step is the same as step 1 of example 1.

2. Soaking the foamed nickel dried in the step 1 in 20mL of pretreatment solution containing 0.375mmol/L Ni (NO)₃)₂、0.75mmol/L Co(NO₃)₂、1.125mmol/L NH₄NO₃And heating the aqueous solution of dimethyl sulfoxide with the volume concentration of 2.5% in an oil bath at 100 ℃ for 90min for reaction, repeatedly ultrasonically cleaning the sample for several times by using deionized water and absolute ethyl alcohol after the reaction is finished, and drying the sample in an oven at 60 ℃ for 2h to obtain the pretreated foamed nickel.

3. Immersing the foamed nickel substrate pretreated in the step 2 in 20mL of solution containing 0.75mmol/L Co (NO)₃)₂、 0.375mol/L NiCl₂The preparation method comprises the following steps of standing in a reaction kettle with a polytetrafluoroethylene lining and an aqueous solution of 0.3mol/L hexadecyl trimethyl ammonium bromide and 1.35mol/L urea under a closed condition at 100 ℃ for hydrothermal reaction for 5 hours, washing with absolute ethyl alcohol and deionized water in a 40W ultrasonic cleaning instrument for 5 minutes each time after the reaction is finished, repeatedly washing for 3 times, and drying in an oven at 80 ℃ for 3 hours at constant temperature.

Claims

1. A method for in-situ growth of braided porous NiCo ₂ O ₄ nanosheets, characterized in that the method consists of the following steps:

(1) Under normal temperature, ultrasonically soak the nickel foam substrate in 1-3mol/L acetone aqueous solution for 20-40 minutes, and then ultrasonically soak it in hydrochloric acid with a mass concentration of 5%-10% for 20-40 minutes; after soaking Repeatedly wash the nickel foam substrate with absolute ethanol and deionized water until neutral, and vacuum dry the cleaned nickel foam substrate at 80-100 °C;

(2) Immerse the foamed nickel substrate after vacuum drying in step (1) in a pretreatment solution, and heat and react at 80 to 110° C. for 30 to 120 minutes, wherein the pretreatment solution contains 0.3 to 0.5 mmol/L Ni(NO ₃ ) ₂ , 0.5-1 mmol/L Co(NO ₃ ) ₂ , 1.0-1.5 mmol/L NH ₄ NO ₃ , aqueous solution of 1-5% dimethyl sulfoxide; The nickel foam substrate was repeatedly ultrasonically cleaned with ionized water and anhydrous ethanol, and dried to obtain the pretreated nickel foam substrate;

(3) Immerse the nickel foam substrate pretreated in step (2) in a solution containing 0.5-1 mmol/L Co(NO ₃ ) ₂ , 0.3-0.5 mmol/L NiCl ₂ , and 0.2-0.4 mmol/L hexadecyl trioxide In the aqueous solution of methyl ammonium bromide and 1～1.5mmol/L urea, hydrothermally react at 80～110 ℃ for 5～8 hours, after the reaction, ultrasonically clean with absolute ethanol and deionized water, and dry;

(4) annealing the nickel foam substrate obtained in step (3) at 250-400° C. for 1-4 hours in an air atmosphere to obtain woven porous NiCo ₂ O ₄ nanosheets.

2. The method for in-situ growth of braided porous NiCo ₂ O ₄ nanosheets according to claim 1, characterized in that: in step (1), under normal temperature, the foamed nickel substrate is first placed in a 2mol/L acetone aqueous solution Ultrasonic immersion for 30 minutes, then ultrasonic immersion in hydrochloric acid with a mass concentration of 7% to 8% for 30 minutes, and the ultrasonic power is 100W.

3. The method for in-situ growth of braided porous NiCo ₂ O ₄ nanosheets according to claim 1, wherein in step (2), the foamed nickel substrate after vacuum drying in step (1) is soaked in a pre- In the treatment liquid, the reaction is heated at 90 to 100° C. for 60 to 90 minutes.

4. The method for in-situ growth of braided porous NiCo ₂ O ₄ nanosheets according to claim 1 or 3, characterized in that: in step (2), the pretreatment solution contains 0.35-0.40 mmol/ An aqueous solution of L Ni(NO ₃ ) ₂ , 0.7-0.8 mmol/L Co(NO ₃ ) ₂ , 1.12-1.13 mmol/L NH ₄ NO ₃ , and 2%-3% dimethyl sulfoxide by volume.

5 . The method for in-situ growth of braided porous NiCo ₂ O ₄ nanosheets according to claim 1 , wherein in step (3), the pretreated foamed nickel substrate in step (2) is dipped in a In the aqueous solution of 0.7～0.8mmol/L Co(NO ₃ ) ₂ , 0.35～0.40mmol/L NiCl ₂ , 0.3～0.4mmol/L hexadecyltrimethylammonium bromide, 1.3～1.5mol/L urea, 90～100℃ hydrothermal reaction for 6～7 hours.

6 . The method for in-situ growth of braided porous NiCo ₂ O ₄ nanosheets according to claim 1 , wherein in step (4), the needle-shaped nickel-cobalt double metal hydroxide grown in step (3) is hydrated. 7 . The foamed nickel substrate was annealed at 300-320 °C for 2-3 hours in an air atmosphere.

7 . The method for in-situ growth of braided porous NiCo ₂ O ₄ nanosheets according to claim 1 or 6, characterized in that: in step (4), the heating rate of annealing is 1～5°C /min.