Defect-regulated ni-zn o carbon nanotube electrochemical energy storage electrode and construction method thereof

Abstract

This invention discloses a defect-modified Ni-ZnO carbon nanotube electrochemical energy storage electrode and its construction method, belonging to the technical field of electrochemical energy storage materials and devices. Using polyacrylonitrile as the carbon source, nickel chloride hexahydrate and zinc chloride as metal precursors, 2-methylimidazole as a defect modifier, and acidified multi-walled carbon nanotubes as a conductive modifier, a composite precursor fiber membrane is prepared by electrospinning. This membrane is then pre-oxidized in air and subjected to segmented high-temperature carbonization with nitrogen to construct a defect-rich three-dimensional network structure. Finally, a self-supporting integrated energy storage electrode is obtained by impregnation with polytetrafluoroethylene emulsion and low-temperature heat treatment. The self-supporting structure of this invention eliminates the need for binders and conductive additives, effectively mitigating the volume expansion of the active material during charging and discharging. The process parameters of this invention are controllable and environmentally friendly. The resulting electrode exhibits a large specific surface area, high defect level, and excellent rate performance and cycle stability, making it widely applicable in supercapacitors and electrochemical energy storage devices.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage materials and devices, and more specifically, relates to a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode and its construction method. Background Technology

[0002] With the rapid development of the new energy industry, electrochemical energy storage devices are widely used in new energy storage, portable electronic devices, and smart grids due to their high energy conversion efficiency, long cycle life, and environmental friendliness. Electrode materials are a key component of electrochemical energy storage devices; their microstructure, conductivity, and the number of active sites directly determine the specific capacity, rate performance, and cycle stability of the energy storage device. Therefore, developing novel composite energy storage electrode materials that combine high specific capacity, high stability, and low cost has become an important research direction in this field. Among them, metal oxide-based composite materials have attracted widespread attention as energy storage electrode materials due to their high theoretical specific capacity and abundant redox activity.

[0003] Zinc oxide (ZnO) is a typical transition metal oxide energy storage material due to its advantages such as low cost, abundant resources, and good redox reversibility. However, ZnO has poor intrinsic conductivity, significant volume expansion and deformation during charge and discharge, low utilization of active sites, and is prone to electrode structure collapse and rapid capacity decay, limiting its standalone application in high-performance energy storage electrodes. To improve the energy storage performance of ZnO, modification methods such as metal doping, structural modification, and carbon-based composites are commonly used. Among these, nickel (Ni) doping can effectively control ZnO lattice defects, introduce vacancy defects, and improve electron conduction rate. At the same time, the nickel-based active component can provide additional energy storage active sites, thus playing a dual-function energy storage role.

[0004] Currently, although Ni-ZnO composite materials have shown potential in energy storage, they generally suffer from problems such as particle agglomeration, structural disorder, and high interfacial impedance. The methods for material modification and control are relatively simple, and the precision of defect control is insufficient, making it difficult to achieve both high specific capacity and long-term cycle stability at the same time.

[0005] Existing Ni-ZnO composite energy storage materials are mostly prepared using traditional methods such as impregnation, co-precipitation, or ball milling, resulting in powdered products. During electrode fabrication, polymeric binders and conductive additives must be added to coat the active material onto the surface of current collectors such as carbon paper. The use of binders presents several problems: firstly, binders can coat active particles and block surface active sites, increasing the interfacial contact resistance within the electrode and reducing ion diffusion and electron transport efficiency, leading to a decrease in electrode rate performance; secondly, during long-term charge-discharge cycles, polymeric binders are prone to swelling, aging, and peeling, causing active material detachment, damaging the electrode structure, and significantly shortening the electrode's lifespan. Furthermore, traditional carbon paper-based electrode structures are relatively rigid, with pore structures difficult to control as needed, and a single ion transport path, making them unsuitable for high-load, high-rate energy storage conditions.

[0006] Carbon nanotubes possess excellent electrical conductivity, mechanical stability, and a hollow porous structure, and are often used as carbonaceous modification materials to optimize metal oxide electrodes. They can effectively alleviate the volume expansion of metal oxides and construct continuous conductive networks. Electrospinning technology is a fabrication process that enables integrated self-supporting electrodes. It involves uniformly mixing a metal precursor with a polymer and then spinning the mixture. After high-temperature carbonization, a metal-carbon composite nanofiber membrane is obtained. This process allows for in-situ composite formation of carbon nanotubes and metal oxides.

[0007] Currently, although electrospinning technology has been applied to the preparation of various carbon-based energy storage electrodes, there are few reports on technical solutions for modifying Ni-ZnO with defect control strategies and compositing it with carbon nanotubes to construct an integrated self-supporting bifunctional energy storage electrode. The lack of mature and efficient construction processes restricts the large-scale application of such composite electrodes in the field of high-performance electrochemical energy storage. Summary of the Invention

[0008] To address the aforementioned problems in existing technologies, the technical problem to be solved by this invention is to provide a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode, which possesses high specific capacity, low impedance, high rate performance, and excellent cycle stability. Another technical problem to be solved by this invention is to provide a method for constructing the aforementioned defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode, with mild construction conditions and precisely controllable process parameters.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0010] A method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode includes the following steps:

[0011] 1) Dissolve polyacrylonitrile in N,N-dimethylformamide, add nickel salt, zinc salt, 2-methylimidazole and acid-modified multi-walled carbon nanotubes, stir evenly to obtain composite spinning solution;

[0012] 2) The composite spinning solution obtained in step 1) is electrospun to obtain a fiber membrane, which is then peeled off after vacuum drying to obtain the precursor fiber membrane.

[0013] 3) The precursor fiber membrane obtained in step 2) is heated to 270°C in air and kept at that temperature for pre-oxidation;

[0014] 4) The pre-oxidized fiber membrane was carbonized in a nitrogen atmosphere using a segmented gradient heating method to obtain a defect-rich Ni-ZnO@nitrogen-doped carbon nanofiber membrane.

[0015] 5) The fiber membrane obtained in step 4) is immersed in polytetrafluoroethylene emulsion for impregnation treatment, and then removed and cured by heat treatment to obtain a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode.

[0016] Preferably, in step 1), the nickel salt is nickel chloride hexahydrate and the zinc salt is zinc chloride.

[0017] Preferably, the mass ratio of nickel chloride hexahydrate to zinc chloride is 0.1~0.4:0.05~0.4.

[0018] Preferably, in step 1), the mass ratio of 2-methylimidazole, multi-walled carbon nanotubes and polyacrylonitrile is 1~1.5:0.05~0.15:1~1.5; and the mass-volume ratio of polyacrylonitrile to N,N-dimethylformamide is 1.2 g:10 mL.

[0019] Preferably, in step 2), the electrospinning voltage is 18 kV, the feed rate is 0.5 mL / h, the receiving distance is 18 cm, and the spinning time is 5 h.

[0020] Preferably, in step 3), the heating rate is 1℃ / min and the holding time is 90 min.

[0021] Preferably, in step 4), the segmented carbonization process is as follows: first, the temperature is increased to 500℃ at 3℃ / min and held for 30min, then the temperature is increased to 850~900℃ at 5℃ / min and held for 1~2h, and finally the temperature is decreased to 400℃ at 2℃ / min and cooled with the furnace.

[0022] Preferably, in step 5), the mass fraction of the polytetrafluoroethylene emulsion is 8%, and the soaking time is 8 min.

[0023] Preferably, in step 5), the heat treatment temperature is 280°C and the heat treatment time is 15 min.

[0024] A defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode is constructed using the method described above.

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

[0026] 1) This invention employs a Ni-doped 2-methylimidazolium defect control strategy to precisely introduce oxygen vacancy defects into the ZnO lattice, significantly increasing the number of electrochemical active sites and significantly improving the electrode specific capacitance and charge transport kinetics. The specific capacitance improvement is significant compared to traditional composite materials.

[0027] 2) This invention combines acidified carbon nanotubes with Ni-ZnO in situ to construct a three-dimensional through-conducting network, which effectively reduces charge transfer resistance and improves electrode rate performance; at the same time, the carbon nanotubes and carbon nanofiber skeleton synergistically constrain the volume expansion of the active material, preventing the electrode structure from collapsing during charging and discharging.

[0028] 3) This invention uses electrospinning combined with segmented carbonization to prepare an integrated self-supporting fiber membrane electrode, which eliminates the need to add polymer binders and conductive additives, thus avoiding the problems of binders covering active sites, increasing interfacial impedance, and long-term cyclic swelling and shedding, and greatly improving the long-cycle service life of the electrode.

[0029] 4) The construction process of this invention is mild, simple, green and pollution-free, with readily available raw materials and precisely controllable process parameters. Different component ratios, carbon nanotube doping amounts and carbonization temperatures can be flexibly optimized, making it suitable for large-scale industrial production applications. Attached Figure Description

[0030] Figure 1 This is a process flow diagram for constructing the defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode of the present invention.

[0031] Figure 2 The graph shows the comparison of specific capacitance between Examples 1-6 and Comparative Examples 1-5 at current densities of 1 A / g and 10 A / g. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is further described below with reference to specific embodiments. Unless otherwise specified, the technical means used in the following embodiments are all conventional means well known to those skilled in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0033] In the following examples, the polyacrylonitrile (PAN) used has a molecular weight of 150,000; the multi-walled carbon nanotubes (CNTs) have a diameter of 10-20 nm and are functionalized with concentrated nitric acid.

[0034] This application provides a method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode, the process flow diagram of which is shown below. Figure 1 As shown, polyacrylonitrile was used as the carbon source matrix, and nickel and zinc salt precursors were introduced. 2-methylimidazolium was used to achieve directional control of ZnO lattice defects. Acid-modified multi-walled carbon nanotubes were doped to construct a three-dimensional continuous conductive network. An integrated self-supporting precursor fiber membrane was prepared using electrospinning. Air pre-oxidation treatment stabilized the fiber microstructure and framework structure. Then, segmented high-temperature carbonization was performed under a nitrogen protective atmosphere to construct abundant oxygen vacancy defects in the Ni-ZnO lattice, simultaneously forming a conductive support framework where carbon nanofibers and carbon nanotubes intertwine. The carbonized fiber membrane was impregnated with polytetrafluoroethylene emulsion and modified with low-temperature heat treatment to improve the electrolyte wetting performance of the electrode surface and the overall structural stability.

[0035] Example 1

[0036] A method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode includes the following steps:

[0037] 1) Dissolve 1.2 g of polyacrylonitrile in 10 mL of N,N-dimethylformamide and stir at 50 °C for 12 h to prepare a PAN / DMF solution with a concentration of 12 wt%. Add 0.25 g of nickel chloride hexahydrate, 0.2 g of zinc chloride and 1.2 g of 2-methylimidazole to the PAN / DMF solution and stir magnetically at room temperature for 24 h to obtain a spinning solution. Disperse 0.1 g of acid-treated functionalized multi-walled carbon nanotubes in 5 mL of DMF by ultrasonication for 2 h, and then add them to the spinning solution and continue stirring for 12 h to obtain a composite spinning solution with uniformly dispersed CNTs.

[0038] 2) Transfer the composite spinning solution obtained in step 1) into a 5 mL syringe and perform electrospinning using a metal needle with an inner diameter of 0.6 mm. The process parameters are: spinning voltage 18 kV, feed rate 0.5 mL / h, receiving distance 18 cm, receiving substrate is a rotating drum covered with aluminum foil, rotation speed 300 rpm, and continuous spinning for 5 h. After that, the obtained nanofiber membrane is vacuum dried at 80℃ for 12 h and peeled off to obtain a white Ni-Zn / CNT / PAN precursor fiber membrane.

[0039] 3) Place the precursor fiber membrane obtained in step 2) in an air atmosphere, heat it to 270°C at a rate of 1°C / min, hold it at that temperature for 90 min for pre-oxidation, and then remove it after cooling it to room temperature in the furnace.

[0040] 4) The pre-oxidized fiber membrane obtained in step 3) is placed in a tube furnace and subjected to segmented carbonization under a nitrogen atmosphere: the temperature is increased to 500℃ at 3℃ / min and held for 30 min, then increased to 850℃ at 5℃ / min and held for 2 h, and finally cooled to 400℃ at 2℃ / min and cooled to room temperature with the furnace to obtain a defect-rich Ni-ZnO@nitrogen-doped carbon nanofiber membrane.

[0041] 5) Immerse the fiber membrane obtained in step 4) in 8% polytetrafluoroethylene emulsion for 8 min, remove it and heat-treat it at 280℃ for 15 min to obtain Ni-ZnO carbon nanotube electrochemical energy storage electrode.

[0042] Example 2

[0043] A method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode includes the following steps:

[0044] 1) Dissolve 1.2 g of polyacrylonitrile in 10 mL of N,N-dimethylformamide and stir at 50 °C for 12 h to prepare a PAN / DMF solution with a concentration of 12 wt%. Add 0.4 g of nickel chloride hexahydrate, 0.05 g of zinc chloride and 1.2 g of 2-methylimidazole to the PAN / DMF solution and stir magnetically at room temperature for 24 h to obtain a spinning solution. Disperse 0.1 g of acid-treated functionalized multi-walled carbon nanotubes in 5 mL of DMF by ultrasonication for 2 h, and then add them to the spinning solution and continue stirring for 12 h to obtain a composite spinning solution with uniformly dispersed CNTs.

[0045] 2) Transfer the composite spinning solution obtained in step 1) into a 5 mL syringe and perform electrospinning using a metal needle with an inner diameter of 0.6 mm. The process parameters are: spinning voltage 18 kV, feed rate 0.5 mL·h. -1 The receiving distance was 18 cm, the receiving substrate was a rotating drum covered with aluminum foil, the rotation speed was 300 rpm, and after continuous spinning for 5 h, the obtained nanofiber membrane was vacuum dried at 80℃ for 12 h, and the white Ni-Zn / CNT / PAN precursor fiber membrane was obtained by peeling.

[0046] 3) Place the precursor fiber membrane obtained in step 2) in an air atmosphere, heat it to 270°C at a rate of 1°C / min, hold it at that temperature for 90 min for pre-oxidation, and then remove it after cooling it to room temperature in the furnace.

[0047] 4) The pre-oxidized fiber membrane obtained in step 3) is placed in a tube furnace and subjected to segmented carbonization under a nitrogen atmosphere: the temperature is increased to 500℃ at 3℃ / min and held for 30 min, then increased to 850℃ at 5℃ / min and held for 2 h, and finally cooled to 400℃ at 2℃ / min and cooled to room temperature with the furnace to obtain a defect-rich Ni-ZnO@nitrogen-doped carbon nanofiber membrane.

[0048] 5) Immerse the fiber membrane obtained in step 4) in 8% polytetrafluoroethylene emulsion for 8 min, remove it and heat-treat it at 280℃ for 15 min to obtain Ni-ZnO carbon nanotube electrochemical energy storage electrode.

[0049] Example 3

[0050] A method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode includes the following steps:

[0051] 1) Dissolve 1.2 g of polyacrylonitrile in 10 mL of N,N-dimethylformamide and stir at 50 °C for 12 h to prepare a PAN / DMF solution with a concentration of 12 wt%. Add 0.1 g of nickel chloride hexahydrate, 0.4 g of zinc chloride and 1.2 g of 2-methylimidazole to the PAN / DMF solution and stir magnetically at room temperature for 24 h to obtain a spinning solution. Disperse 0.1 g of acid-treated functionalized multi-walled carbon nanotubes in 5 mL of DMF by ultrasonication for 2 h, and then add them to the spinning solution and continue stirring for 12 h to obtain a composite spinning solution with uniformly dispersed CNTs.

[0052] 2) Transfer the composite spinning solution obtained in step 1) into a 5 mL syringe and perform electrospinning using a metal needle with an inner diameter of 0.6 mm. The process parameters are: spinning voltage 18 kV, feed rate 0.5 mL / h, receiving distance 18 cm, receiving substrate is a rotating drum covered with aluminum foil, rotation speed 300 rpm, and continuous spinning for 5 h. After that, the obtained nanofiber membrane is vacuum dried at 80℃ for 12 h and peeled off to obtain a white Ni-Zn / CNT / PAN precursor fiber membrane.

[0053] 3) Place the precursor fiber membrane obtained in step 2) in an air atmosphere, heat it to 270°C at a rate of 1°C / min, hold it at that temperature for 90 min for pre-oxidation, and then remove it after cooling it to room temperature in the furnace.

[0054] 4) The pre-oxidized fiber membrane obtained in step 3) is placed in a tube furnace and subjected to segmented carbonization under a nitrogen atmosphere: the temperature is increased to 500℃ at 3℃ / min and held for 30 min, then increased to 850℃ at 5℃ / min and held for 2 h, and finally cooled to 400℃ at 2℃ / min and cooled to room temperature with the furnace to obtain a defect-rich Ni-ZnO@nitrogen-doped carbon nanofiber membrane.

[0055] 5) Immerse the fiber membrane obtained in step 4) in 8% polytetrafluoroethylene emulsion for 8 min, remove it and heat-treat it at 280℃ for 15 min to obtain Ni-ZnO carbon nanotube electrochemical energy storage electrode.

[0056] Example 4

[0057] A method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode includes the following steps:

[0058] 1) Dissolve 1.2 g of polyacrylonitrile in 10 mL of N,N-dimethylformamide and stir at 50 °C for 12 h to prepare a PAN / DMF solution with a concentration of 12 wt%. Add 0.25 g of nickel chloride hexahydrate, 0.2 g of zinc chloride and 1.2 g of 2-methylimidazole to the PAN / DMF solution and stir magnetically at room temperature for 24 h to obtain a spinning solution. Disperse 0.05 g of acid-treated functionalized multi-walled carbon nanotubes in 5 mL of DMF by ultrasonication for 2 h, and then add them to the spinning solution and continue stirring for 12 h to obtain a composite spinning solution with uniformly dispersed CNTs.

[0059] 2) Transfer the composite spinning solution obtained in step 1) into a 5 mL syringe and perform electrospinning using a metal needle with an inner diameter of 0.6 mm. The process parameters are: spinning voltage 18 kV, feed rate 0.5 mL·h. -1 The receiving distance was 18 cm, the receiving substrate was a rotating drum covered with aluminum foil, the rotation speed was 300 rpm, and after continuous spinning for 5 h, the obtained nanofiber membrane was vacuum dried at 80℃ for 12 h, and the white Ni-Zn / CNT / PAN precursor fiber membrane was obtained by peeling.

[0060] 3) Place the precursor fiber membrane obtained in step 2) in an air atmosphere, heat it to 270°C at a rate of 1°C / min, hold it at that temperature for 90 min for pre-oxidation, and then remove it after cooling it to room temperature in the furnace.

[0061] 4) The pre-oxidized fiber membrane obtained in step 3) is placed in a tube furnace and subjected to segmented carbonization under a nitrogen atmosphere: the temperature is increased to 500℃ at 3℃ / min and held for 30 min, then increased to 850℃ at 5℃ / min and held for 2 h, and finally cooled to 400℃ at 2℃ / min and cooled to room temperature with the furnace to obtain a defect-rich Ni-ZnO@nitrogen-doped carbon nanofiber membrane.

[0062] 5) Immerse the fiber membrane obtained in step 4) in 8% polytetrafluoroethylene emulsion for 8 min, remove it and heat-treat it at 280℃ for 15 min to obtain Ni-ZnO carbon nanotube electrochemical energy storage electrode.

[0063] Example 5

[0064] A method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode includes the following steps:

[0065] 1) Dissolve 1.2 g of polyacrylonitrile in 10 mL of N,N-dimethylformamide and stir at 50 °C for 12 h to prepare a PAN / DMF solution with a concentration of 12 wt%. Add 0.25 g of nickel chloride hexahydrate, 0.2 g of zinc chloride and 1.2 g of 2-methylimidazole to the PAN / DMF solution and stir magnetically at room temperature for 24 h to obtain a spinning solution. Disperse 0.15 g of acid-treated functionalized multi-walled carbon nanotubes in 5 mL of DMF by ultrasonication for 2 h, and then add them to the spinning solution and continue stirring for 12 h to obtain a composite spinning solution with uniformly dispersed CNTs.

[0066] 2) Transfer the composite spinning solution obtained in step 1) into a 5 mL syringe and perform electrospinning using a metal needle with an inner diameter of 0.6 mm. The process parameters are: spinning voltage 18 kV, feed rate 0.5 mL·h. -1 The receiving distance was 18 cm, the receiving substrate was a rotating drum covered with aluminum foil, the rotation speed was 300 rpm, and after continuous spinning for 5 h, the obtained nanofiber membrane was vacuum dried at 80℃ for 12 h, and the white Ni-Zn / CNT / PAN precursor fiber membrane was obtained by peeling.

[0067] 3) Place the precursor fiber membrane obtained in step 2) in an air atmosphere, heat it to 270°C at a rate of 1°C / min, hold it at that temperature for 90 min for pre-oxidation, and then remove it after cooling it to room temperature in the furnace.

[0068] 4) The pre-oxidized fiber membrane obtained in step 3) is placed in a tube furnace and subjected to segmented carbonization under a nitrogen atmosphere: the temperature is increased to 500℃ at 3℃ / min and held for 30 min, then increased to 850℃ at 5℃ / min and held for 2 h, and finally cooled to 400℃ at 2℃ / min and cooled to room temperature with the furnace to obtain a defect-rich Ni-ZnO@nitrogen-doped carbon nanofiber membrane.

[0069] 5) Immerse the fiber membrane obtained in step 4) in 8% polytetrafluoroethylene emulsion for 8 min, remove it and heat-treat it at 280℃ for 15 min to obtain Ni-ZnO carbon nanotube electrochemical energy storage electrode.

[0070] Example 6

[0071] A method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode includes the following steps:

[0072] 1) Dissolve 1.2 g of polyacrylonitrile in 10 mL of N,N-dimethylformamide and stir at 50 °C for 12 h to prepare a PAN / DMF solution with a concentration of 12 wt%. Add 0.25 g of nickel chloride hexahydrate, 0.2 g of zinc chloride and 1.2 g of 2-methylimidazole to the PAN / DMF solution and stir magnetically at room temperature for 24 h to obtain a spinning solution. Disperse 0.1 g of acid-treated functionalized multi-walled carbon nanotubes in 5 mL of DMF by ultrasonication for 2 h, and then add them to the spinning solution and continue stirring for 12 h to obtain a composite spinning solution with uniformly dispersed CNTs.

[0073] 2) Transfer the composite spinning solution obtained in step 1) into a 5 mL syringe and perform electrospinning using a metal needle with an inner diameter of 0.6 mm. The process parameters are: spinning voltage 18 kV, feed rate 0.5 mL·h. -1 The receiving distance was 18 cm, the receiving substrate was a rotating drum covered with aluminum foil, the rotation speed was 300 rpm, and after continuous spinning for 5 h, the obtained nanofiber membrane was vacuum dried at 80℃ for 12 h, and the white Ni-Zn / CNT / PAN precursor fiber membrane was obtained by peeling.

[0074] 3) Place the precursor fiber membrane obtained in step 2) in an air atmosphere, heat it to 270°C at a rate of 1°C / min, hold it at that temperature for 90 min for pre-oxidation, and then remove it after cooling it to room temperature in the furnace.

[0075] 4) The pre-oxidized fiber membrane obtained in step 3) is placed in a tube furnace and subjected to segmented carbonization under a nitrogen atmosphere: the temperature is increased to 500℃ at 3℃ / min and held for 30 min, then increased to 900℃ at 5℃ / min and held for 1 h, and finally cooled to 400℃ at 2℃ / min and cooled to room temperature with the furnace to obtain a defect-rich Ni-ZnO@nitrogen-doped carbon nanofiber membrane.

[0076] 5) Immerse the fiber membrane obtained in step 4) in 8% polytetrafluoroethylene emulsion for 8 min, remove it and heat-treat it at 280℃ for 15 min to obtain Ni-ZnO carbon nanotube electrochemical energy storage electrode.

[0077] Comparative Example 1

[0078] A method for constructing a Ni-ZnO carbon nanotube electrochemical energy storage electrode differs from Example 1 in that: in step 4), the segmented carbonization is further heated to 700℃ at a rate of 5℃ / min and held for 1 h. The remaining steps and process parameters are the same as in Example 1.

[0079] Comparative Example 2

[0080] A method for constructing a Ni-ZnO carbon nanotube electrochemical energy storage electrode includes the following steps:

[0081] 1) Dissolve 0.25 g of nickel chloride hexahydrate and 0.2 g of zinc chloride in deionized water, add 0.15 g of acid-treated functionalized multi-walled carbon nanotubes, ultrasonically disperse for 1 h, add 1.2 g of 2-methylimidazole, stir at room temperature for 24 h, centrifuge and wash, dry at 80 °C for 12 h, and then calcine at 450 °C for 2 h in air atmosphere to obtain composite material powder;

[0082] 2) Mix the powder obtained in step 1) with acetylene black and PVDF binder at a mass ratio of 8:1:1, add NMP (N-methylpyrrolidone) and grind into a slurry. Coat the slurry evenly onto the surface of the nickel foam at a coating amount of 1 mg / cm². 2 The conventional coated energy storage electrode was obtained by vacuum drying at 80℃ for 12 h.

[0083] Comparative Example 3

[0084] A method for constructing a defect-controlled Ni-ZnO electrochemical energy storage electrode differs from Example 1 in that: multi-walled carbon nanotubes are not added in step 1), while the remaining steps and process parameters are the same as in Example 1.

[0085] Comparative Example 4

[0086] A method for constructing a defect-controlled Ni-ZnO electrochemical energy storage electrode differs from Example 1 in that: 2-methylimidazole is not added in step 1), and 0.25 g of nickel chloride hexahydrate and 0.2 g of zinc chloride are directly added to the PAN / DMF solution. The remaining steps and process parameters are the same as in Example 1.

[0087] Comparative Example 5

[0088] A method for constructing a defect-controlled Ni-ZnO electrochemical energy storage electrode differs from Example 1 in that: in step 1), nickel chloride hexahydrate is not added, and 0.2g of zinc chloride and 1.2g of 2-methylimidazole are added to the PAN / DMF solution. The remaining steps and process parameters are the same as in Example 1.

[0089] The energy storage electrodes prepared in Examples 1-6 and Comparative Examples 1-5 were subjected to performance tests, and the test methods were as follows:

[0090] 1. Cyclic Voltammetry (CV) Test:

[0091] The tests were conducted using a CHI760E electrochemical workstation in a three-electrode system. The preparative electrode was used as the working electrode, the platinum sheet as the counter electrode, and Hg / HgO as the reference electrode. The electrolyte was a 6 mol / L KOH solution. The scanning voltage range was 0–0.55 V, and the scanning rate was 5–100 mV / s.

[0092] 2. Constant Current Charge-Discharge (GCD) Test

[0093] The current density was set to 1 and 10 A / g; the specific capacitance was calculated based on the discharge curve: C = IΔt / (mΔV), where: C is the specific capacitance (F / g); I is the discharge current (A); Δt is the discharge time (s); m is the mass of the active material (g); and ΔV is the discharge voltage window (V).

[0094] 3. Electrochemical Impedance (EIS) Test

[0095] The test frequency range is 0.01 Hz to 100 kHz; the AC disturbance amplitude is 5 mV; the charge transfer resistance (Rct) is calculated based on the Nyquist plot.

[0096] 4. Cyclic stability test

[0097] Perform 5000 charge-discharge cycles at a current density of 10 A / g; record the capacity retention.

[0098] 5. Defect Concentration Test

[0099] XPS was used to test the O 1s peak; the oxygen vacancy concentration was calculated based on the peak area ratio of oxygen vacancies; and Raman spectroscopy was used to measure the ID / IG value to evaluate the defect degree. The test results are shown in Tables 1 and 2. Figure 2 As shown.

[0100] Table 1. Structural performance test results of Examples 1-6 and Comparative Examples 1-5

[0101]

[0102] Table 2 Electrochemical performance test results of Examples 1-6 and Comparative Examples 1-5

[0103]

[0104] From Table 1-Table 2 and Figure 2 It is known that the defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode constructed in this invention has high specific capacity, low impedance, high rate performance and excellent cycle stability, and is suitable for high-performance supercapacitors and hybrid energy storage devices.

[0105] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode, characterized in that, Includes the following steps: 1) Dissolve polyacrylonitrile in N,N-dimethylformamide, add nickel salt, zinc salt, 2-methylimidazole and acid-modified multi-walled carbon nanotubes, stir evenly to obtain composite spinning solution; 2) The composite spinning solution obtained in step 1) is electrospun to obtain a fiber membrane, which is then peeled off after vacuum drying to obtain the precursor fiber membrane. 3) The precursor fiber membrane obtained in step 2) is heated to 270°C in air and kept at that temperature for pre-oxidation; 4) The pre-oxidized fiber membrane was carbonized in a nitrogen atmosphere using a segmented gradient heating method to obtain a defect-rich Ni-ZnO@nitrogen-doped carbon nanofiber membrane. 5) The fiber membrane obtained in step 4) is immersed in polytetrafluoroethylene emulsion for impregnation treatment, and then removed and cured by heat treatment to obtain a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode.

2. The method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode according to claim 1, characterized in that, In step 1), the nickel salt is nickel chloride hexahydrate and the zinc salt is zinc chloride.

3. The method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode according to claim 2, characterized in that, The mass ratio of nickel chloride hexahydrate to zinc chloride is 0.1~0.4:0.05~0.

4.

4. The method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode according to claim 1, characterized in that, In step 1), the mass ratio of 2-methylimidazole, multi-walled carbon nanotubes and polyacrylonitrile is 1~1.5:0.05~0.15:1~1.5; the mass-volume ratio of polyacrylonitrile to N,N-dimethylformamide is 1.2 g:10 mL.

5. The method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode according to claim 1, characterized in that, In step 2), the electrospinning voltage is 18 kV, the feed rate is 0.5 mL / h, the receiving distance is 18 cm, and the spinning time is 5 h.

6. The method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode according to claim 1, characterized in that, In step 3), the heating rate is 1℃ / min and the holding time is 90 min.

7. The method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode according to claim 1, characterized in that, In step 4), the segmented carbonization process is as follows: first, the temperature is increased to 500℃ at 3℃ / min and held for 30 min, then the temperature is increased to 850~900℃ at 5℃ / min and held for 1~2 h, and finally the temperature is decreased to 400℃ at 2℃ / min and cooled with the furnace.

8. The method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode according to claim 1, characterized in that, In step 5), the mass fraction of the polytetrafluoroethylene emulsion is 8%, and the soaking time is 8 min.

9. The method for constructing a defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode according to claim 1, characterized in that, In step 5), the heat treatment temperature is 280℃ and the heat treatment time is 15 min.

10. A defect-controlled Ni-ZnO carbon nanotube electrochemical energy storage electrode, characterized in that, It is constructed by the method described in any one of claims 1-9.

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