Preparation method of flexible electrode with ZnO-coated Ni-doped CoP acicular network structure

Abstract

The application discloses a preparation method of a ZnO-coated Ni-doped CoP needle-like network structure flexible electrode, specifically comprising the following steps: growing a NiCo-LDH precursor (CC / NiCo-LDH) on a carbon cloth through a solvothermal method, taking NaH2PO2.H2O as a phosphorus source, and then performing calcination and phosphorization treatment to obtain a needle-like network structure CC / Ni-CoP; and then depositing a ZnO ultrathin film on the CC / Ni-CoP through an atomic layer deposition technology (ALD), wherein the thickness of the deposited ZnO coating layer is 2-12 nm; and finally preparing a CC / Ni-CoP@ZnO flexible electrode. The application has the advantages of simple synthesis, easy operation, mild reaction conditions, and the like, and the obtained needle-like network structure CC / Ni-CoP@ZnO flexible electrode has super-high mass specific capacity, excellent rate performance and good cycle stability, and has a good application prospect in the field of flexible electrochemical energy storage.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology and relates to a method for preparing a flexible electrode with a ZnO-coated Ni-doped CoP needle-like network structure. Background Technology

[0002] With the rapid development of smart, flexible, portable, and wearable electronic products, there are increasing demands on flexible energy storage devices to achieve lightweight, thin, and flexible mechanical properties, while maintaining high energy density, power density, and cycle stability under prolonged continuous mechanical deformation (such as bending, twisting, and stretching). Supercapacitors, as a type of electrochemical energy storage device, are considered promising due to their advantages such as fast charging and discharging speeds, high power density, good cycle stability, low cost, and environmental friendliness. The key to developing flexible supercapacitors lies in the fabrication of flexible electrodes. Carbon cloth, with its excellent chemical stability, high conductivity, mechanical flexibility, and low cost, can be used as a flexible conductive substrate or current collector for the fabrication of flexible electrodes.

[0003] Transition metal phosphide (TMP) electrode materials have been extensively studied in supercapacitors in recent years, especially cobalt phosphide (CoP), partly because Co... 2+ The presence of covalent bonds enables charge storage and provides high capacity through Faraday reactions. Furthermore, the presence of Co metallic bonds provides free electrons, giving CoP high conductivity and improving its rate performance. However, the Faraday redox reaction during charge-discharge processes causes volume changes that can lead to structural pulverization and detachment, resulting in rapid capacity decay and low cycle stability. Additionally, CoP electrode materials still exhibit electrochemical reaction kinetic hysteresis, further degrading their rate performance.

[0004] Doping CoP with another metal ion allows the introduced heteroatoms to occupy lattice sites in Co, altering its charge state and generating more active sites. This also modulates the band gap, thereby improving the conductivity and electrochemical performance of CoP. This is considered an easily implemented and effective modification method. Furthermore, the uniform and controllable deposition of an oxide ultrathin film on the surface of metal-doped CoP using atomic layer deposition (ALD) technology can not only act as a buffer layer to suppress volume changes during long-cycle charge-discharge processes but also promote rapid electron and ion transfer and diffusion, thus improving the rate performance and cycle stability of metal-doped CoP. This is considered an effective strategy for preparing high-performance electrode materials. Summary of the Invention

[0005] The application aims to provide a preparation method of a ZnO-coated Ni-doped CoP acicular network structure flexible electrode.

[0006] The technical scheme adopted by the application is a preparation method of a ZnO-coated Ni-doped CoP acicular network structure flexible electrode, specifically, growing a Ni-doped CoP acicular network structure (CC / Ni-CoP) on carbon cloth, and then depositing a ZnO ultrathin film on the CC / Ni-CoP by ALD technology to prepare a CC / Ni-CoP@ZnO flexible electrode.

[0007] The application also has the characteristics that:

[0008] The preparation method of the ZnO-coated Ni-doped CoP acicular network structure flexible electrode is implemented according to the following steps:

[0009] Step 1: ultrasonic acidification treatment is performed on carbon cloth, and then ultrasonic cleaning is performed, and the carbon cloth (CC) after drying is obtained as a surface pretreated carbon cloth;

[0010] Step 2: ethanol is added to deionized water, and the mixture is stirred uniformly on a magnetic stirrer to obtain a mixed solution of ethanol and deionized water;

[0011] Step 3: a certain amount of Ni(NO3)2·6H2O, Co(NO3)2·6H2O and urea are sequentially added to the mixed solution to obtain a pink homogeneous solution;

[0012] Step 4: the pink homogeneous solution obtained in step 3 is poured into a polytetrafluoroethylene liner, and then the pretreated carbon cloth (CC) in step 1 is placed in the homogeneous solution, and the solution is sealed with a stainless steel hydrothermal kettle, and then solvent thermal reaction is performed in a forced air drying oven; after the reaction is completed, the reaction kettle is cooled to room temperature, and the CC / NiCo-LDH precursor is obtained, which is placed in deionized water for ultrasonic cleaning, and then washed with deionized water and ethanol several times, and finally dried in a vacuum drying oven;

[0013] Step 5: a certain amount of NaH2PO2·H2O powder is placed in a porcelain boat and placed in the gas inlet end of a double-temperature-zone control quartz tube furnace, and then the CC / NiCo-LDH precursor is placed in the porcelain boat and placed in the gas outlet end, a continuous argon gas flow is introduced, and the temperature is increased at a certain rate to a certain temperature for phosphating treatment; after the reaction is completed, the Ni-doped CoP (CC / Ni-CoP) is obtained;

[0014] Step 6: a ZnO ultrathin film is deposited on the CC / Ni-CoP prepared in step 5 by ALD technology.

[0015] wherein step 1 is specifically: 1 x 2 cm 2 The carbon cloth is subjected to ultrasonic acidification treatment with an aqueous HCl solution, and then subjected to ultrasonic cleaning with acetone, ethanol and deionized water respectively, to obtain a surface pretreated carbon cloth (CC) after drying;

[0016] wherein the molar concentration of the aqueous HCl solution is 3-5 mol / L; the ultrasonic acidification treatment time is 30-60 min; the ultrasonic cleaning time is 30-50 min; the drying temperature is 50-80 °C, and the drying time is 6-14 h;

[0017] wherein the volume ratio of ethanol to deionized water in step 2 is 1:4; the rotational speed of the magnetic stirrer is 250-450 r / min, and the stirring time is 10-15 min;

[0018] wherein in step 3, the molar ratio of Ni(NO3)2·6H2O to Co(NO3)2·6H2O is 1:5, and the molar ratio of the total amount of Ni(NO3)2·6H2O and Co(NO3)2·6H2O to urea is 3:4; the rotational speed of the magnetic stirrer is 350-550 r / min, and the stirring time is 150-180 min;

[0019] wherein in step 4, the solvothermal reaction temperature is 120 °C, and the reaction time is 5 h; the filling ratio of the mixed solution in the polytetrafluoroethylene liner is 50%; the ultrasonic cleaning time is 1-2 min; the deionized water and ethanol are rinsed 4-6 times respectively; the drying temperature is 50-70 °C, and the vacuum drying time is 10-16 h;

[0020] wherein in step 5, the ratio of the area of the carbon cloth (cm 2 ) to the mass of NaH2PO2·H2O powder (g) is 1:(1-3); the flow rate of the argon gas stream is 50-100 mL / min; the heating rate is 1-5 °C / min, the reaction temperature is 350 °C, and the reaction time is 3 h;

[0021] In step 6, diethyl zinc (Zn(C2H5)2) is selected as the precursor of Zn, H2O is used as the oxidant, and the deposition temperature is set. First, in a vacuum environment, the precursor pulse is maintained for a certain time, the Zn(C2H5)2 vapor is introduced into the reaction chamber, and the reaction is maintained for a certain time. Then, the inert carrier gas Ar is introduced at a certain flow rate and time to purge the chamber. Subsequently, the precursor pulse is maintained for a certain time, the H2O in the reaction chamber is oxidized and reduced with the Zn(C2H5)2 chemisorbed on the CC / Ni-CoP, and the reaction is maintained for a certain time. Finally, the inert carrier gas Ar is introduced at a certain flow rate and time to deposit a layer of ZnO on the CC / Ni-CoP. The process is repeated for several cycles until a ZnO coating layer with a certain thickness is obtained, and a CC / Ni-CoP@ZnO flexible electrode is obtained.

[0022] In step 6, the deposition temperature is 150℃, the precursor pulse duration is 0.02s, and the reaction time is 10s. The flow rate of the inert carrier gas Ar is 50mL / min, and the blowing-off time is 60s. The deposition rate of ZnO is 0.1nm / cycle, the thickness of the deposited ZnO layer is 0.1nm, the cycle number of deposition is 20-120 cycles, and the thickness of the deposited ZnO coating layer is 2-12nm.

[0023] The beneficial effects of the present application are:

[0024] The preparation method of the ZnO-coated Ni-doped CoP needle-like network structure flexible electrode of the present application uses Ni(NO3)2·6H2O as the nickel source, Co(NO3)2·6H2O as the cobalt source, and urea to provide an alkaline environment. First, a CC / NiCo-LDH precursor is prepared by a solvothermal method. Then, NaH2PO2·H2O is used as the phosphorus source to phosphorize the prepared CC / NiCo-LDH, obtaining a needle-like network structure CC / Ni-CoP. Finally, a certain thickness of ZnO ultra-thin film is deposited on the surface of the CC / Ni-CoP, obtaining a CC / Ni-CoP@ZnO flexible electrode.

[0025] Due to the carbon cloth has good stability, low cost, good conductivity and mechanical flexibility and the like, the carbon cloth can be used as a flexible conductive substrate, Ni-doped CoP (CC / Ni-CoP) active material is constructed in situ on the carbon cloth, the carbon cloth and the active material are tightly combined through chemical bonds, the carbon cloth can accelerate charge transmission, meanwhile, the doping of transition metal Ni heteroatoms can change the charge state of CoP, more active sites are generated, the conductivity of CoP is increased, the needle-shaped network structure formed can shorten the diffusion path of electrolyte ions, more reaction active sites are exposed, and the specific capacity and rate performance of the CC / Ni-CoP are effectively improved; in addition, since the atomic layer deposition technology can well preserve the morphology and structure of the CC / Ni-CoP, a layer of ZnO ultra-thin film is coated on the surface of the CC / Ni-CoP by using the atomic layer deposition technology, which not only can promote the diffusion of electrons and electrolyte ions at the electrode / electrolyte interface, but also can buffer the volume change and dissolution of the CC / Ni-CoP in the long cycle charging and discharging process, and the rate performance and cycle stability of the CC / Ni-CoP@ZnO flexible electrode are effectively improved.

[0026] The CC / Ni-CoP@ZnO flexible electrode synthesized in the application has super-high mass specific capacity, excellent rate performance and good cycle stability in an alkaline electrolyte, has the advantages of simple synthesis and easy operation, can provide innovative technical support and theoretical support for the development of flexible supercapacitors, and has important academic significance and application value. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Fig. 1 is a SEM image of the CC / Ni-CoP and CC / Ni-CoP@ZnO flexible electrode prepared in the application, wherein, a graph and a graph b are SEM images of the CC / Ni-CoP at different magnifications, and c graph is a SEM image of the CC / Ni-CoP@ZnO flexible electrode prepared in Example 2 of the application;

[0028] Figure 2 Fig. 2 is an electrochemical performance graph of the CC / Ni-CoP@ZnO flexible electrode prepared in the application, wherein, a graph is a cyclic voltammetry (CV) curve of the CC / Ni-CoP@ZnO flexible electrode prepared in Example 2 of the application at different scanning speeds, and b graph is a galvanostatic charge-discharge (GCD) curve of the CC / Ni-CoP@ZnO flexible electrode prepared in Example 2 of the application at different current densities;

[0029] Figure 3 Fig. 3 is an XRD diffraction spectrum of the CC / Ni-CoP and CC / Ni-CoP@ZnO flexible electrode prepared in the application, wherein, curve a is an XRD diffraction spectrum of the CC / Ni-CoP, and curves b-d are XRD diffraction spectra of the CC / Ni-CoP@ZnO flexible electrode prepared in Examples 1-3 of the application.

[0030] Figure 4 is a comparison chart of cyclic voltammetry curves of the CC / Ni-CoP and CC / Ni-CoP@ZnO flexible electrodes prepared by the present application at a scanning speed of 30 mV s -1 , wherein the dotted line graph a is a cyclic voltammetry curve of the CC / Ni-CoP at a scanning speed of 30 mV s -1 , and the dotted line graphs b-d are cyclic voltammetry curves of the CC / Ni-CoP@ZnO flexible electrodes prepared by the present application in Examples 1-3 at a scanning speed of 30 mV s -1 ;

[0031] Figure 5 is a comparison chart of constant current charge-discharge curves of the CC / Ni-CoP and CC / Ni-CoP@ZnO flexible electrodes prepared by the present application at a current density of 1 Ag -1 , wherein the dotted line graph a is a constant current charge-discharge curve of the CC / Ni-CoP at a current density of 1 Ag -1 , and the dotted line graphs b-d are constant current charge-discharge curves of the CC / Ni-CoP@ZnO flexible electrodes prepared by the present application in Examples 1-3 at a current density of 1 Ag -1 ;

[0032] Figure 6 is a chart of mass specific capacity curves of the CC / Ni-CoP and CC / Ni-CoP@ZnO flexible electrodes prepared by the present application at different current densities, wherein the dotted line graph a is a chart of mass specific capacity curves of the CC / Ni-CoP at different current densities, and the dotted line graphs b-d are charts of mass specific capacity curves of the CC / Ni-CoP@ZnO flexible electrodes prepared by the present application in Examples 1-3 at different current densities;

[0033] Figure 7 is a chart of cycle stability of the CC / Ni-CoP and CC / Ni-CoP@ZnO flexible electrodes prepared by the present application at a current density of 15 Ag -1 , wherein the dotted line graph a is a chart of cycle stability of the CC / Ni-CoP at a current density of 15 Ag -1 , and the dotted line graph b is a chart of cycle stability of the CC / Ni-CoP@ZnO flexible electrode prepared by the present application in Example 2 at a current density of 15 Ag -1 . DETAILED DESCRIPTION

[0034] The present application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] The application aims at the problem of low cobalt phosphide rate performance and cycle stability, and prepares a ZnO-coated Ni-doped CoP flexible electrode with a needle-shaped network structure; the needle-shaped network structure Ni-doped CoP (CC / Ni-CoP) is grown on carbon cloth, which can accelerate the electron transmission speed, provide more reaction active sites, shorten the diffusion path of electrolyte ions, and improve the specific capacity and rate performance of the flexible electrode; in addition, the deposition of a ZnO ultrathin film on the CC / Ni-CoP by ALD technology can further improve the rate performance and cycle stability of the CC / Ni-CoP flexible electrode; the prepared CC / Ni-CoP@ZnO flexible electrode has super-high mass specific capacity and excellent rate performance in an alkaline electrolyte, the cycle stability is improved, and the flexible electrode has good mechanical flexibility and can be applied to flexible supercapacitors.

[0036] Embodiment 1

[0037] A high-performance ZnO-coated Ni-doped CoP flexible electrode with a needle-shaped network structure is prepared by a solvothermal method, a low-temperature phosphating method and an ALD coating technology, wherein the number of cycles of cyclic deposition of ZnO on the CC / Ni-CoP is 40, and the thickness of the deposited ZnO coating layer is 4 nm;

[0038] A preparation method of a high-performance ZnO-coated Ni-doped CoP flexible electrode with a needle-shaped network structure, comprising the following steps:

[0039] Step 1: first, 1×2 cm 2 The carbon cloth is subjected to ultrasonic acidification treatment with a 3 mol / L HCl aqueous solution for 30 min, and then is subjected to ultrasonic cleaning with acetone, ethanol and deionized water for 30 min, respectively, and is dried in a drying box at 50℃ for 8 h to obtain a surface pretreated carbon cloth (CC);

[0040] Step 2: 5 mL of ethanol is added to 20 mL of deionized water, and the mixture is stirred at a speed of 250 r / min on a magnetic stirrer for 10 min to obtain a mixed solution of ethanol and deionized water;

[0041] Step 3: 0.5 mol of Ni(NO3)2·6H2O, 2.5 mol of Co(NO3)2·6H2O and 4.0 mol of urea are sequentially added to the above mixed solution, and the mixture is stirred at a speed of 350 r / min on a magnetic stirrer for 150 min to obtain a pink homogeneous solution;

[0042] Step 4: Pour the obtained pink homogeneous solution into a polytetrafluoroethylene (PTFE) liner, and then place the surface-pretreated carbon cloth (CC) obtained above into the homogeneous solution. The filling ratio of the mixed solution in the PTFE liner is 50%. Subsequently, seal the PTFE liner with a stainless steel hydrothermal reactor and carry out a solvothermal reaction in a forced-air drying oven at a reaction temperature of 120°C for 5 hours. After the reaction is completed and the reactor is cooled to room temperature, ultrasonically clean the obtained CC / NiCo-LDH precursor for 1 minute, and then wash it four times with deionized water and ethanol respectively to remove impurities remaining in the CC / NiCo-LDH precursor. Finally, dry it in a vacuum drying oven at 50°C for 10 hours to obtain the CC / NiCo-LDH precursor.

[0043] Step 5: Place 4g of NaH2PO2·H2O powder into a ceramic boat and position it at the inlet of a dual-temperature zone controlled quartz tube furnace. Then, place the CC / NiCo-LDH precursor into the ceramic boat and position it at the outlet. A continuous argon flow rate of 50mL / min is then introduced, with a heating rate of 2℃ / min, a reaction temperature of 350℃, and a reaction time of 3h. After the reaction is complete, allow the temperature of the dual-temperature zone controlled quartz tube furnace to drop to room temperature before removing the sample to obtain Ni-doped CoP (CC / Ni-CoP).

[0044] Step 6: Diethylzinc (Zn(C2H5)2) was selected as the Zn precursor, H2O was used as the oxidant, and the deposition temperature was set to 150℃. First, under vacuum, a precursor pulse was applied to introduce Zn(C2H5)2 vapor into the reaction chamber for 0.02 s, and the reaction time was 10 s to ensure complete reaction between the Zn(C2H5)2 precursor and the CC / Ni-CoP surface. Second, Ar inert carrier gas was introduced at a flow rate of 50 mL / min to purge the chamber for 60 s to remove unreacted Zn(C2H5)2 precursor or reaction byproducts. Subsequently, a precursor pulse was applied to introduce H2O into the reaction chamber for 0.02 s. The chemically adsorbed Zn(C2H5)2 on CC / Ni-CoP undergoes a redox reaction for 10 s. Finally, the chamber is purged with an inert Ar carrier gas at a flow rate of 50 mL / min for 60 s to remove byproducts and excess ethane molecules from the surface of CC / Ni-CoP, thus depositing a ZnO layer on CC / Ni-CoP. The ZnO deposition rate is 0.1 nm / cycle, the thickness of the deposited ZnO layer is 0.1 nm, and the number of deposition cycles is 40 cycles until a 4 nm thick ZnO coating layer is deposited on the CC / Ni-CoP surface, resulting in a CC / Ni-CoP@ZnO flexible electrode.

[0045] Example 2:

[0046] A high-performance ZnO-coated Ni-doped CoP needle-like network structure flexible electrode is prepared by a solvothermal method, a low-temperature phosphating method and an ALD coating technology, wherein the number of cycles of cyclic deposition of ZnO on the CC / Ni-CoP is 60 cycles, and the thickness of the deposited ZnO coating layer is 6nm;

[0047] A preparation method of a high-performance ZnO-coated Ni-doped CoP needle-like network structure flexible electrode, comprising the following steps:

[0048] Step 1: first, 1×2cm 2 The carbon cloth is subjected to ultrasonic acidification treatment with a 4mol / L HCl aqueous solution for 40min, and then is subjected to ultrasonic cleaning with acetone, ethanol and deionized water for 30min, respectively, and is dried in a 60℃ drying box for 10h to obtain a surface pretreated carbon cloth (CC);

[0049] Step 2: 5mL of ethanol is added to 20mL of deionized water, and the mixture is stirred on a magnetic stirrer at a speed of 300r / min for 15min to obtain a mixed solution of ethanol and deionized water;

[0050] Step 3: 0.5mol of Ni(NO3)2·6H2O, 2.5mol of Co(NO3)2·6H2O and 4.0mol of urea are sequentially added to the above mixed solution, and the mixture is stirred on a magnetic stirrer at a speed of 400r / min for 160min to obtain a pink homogeneous solution;

[0051] Step 4: the above obtained pink homogeneous solution is poured into a polytetrafluoroethylene liner, and then the above obtained surface pretreated carbon cloth (CC) is placed in the homogeneous solution, and the filling ratio of the mixed solution in the polytetrafluoroethylene liner is 50%; then the polytetrafluoroethylene liner is sealed with a stainless steel hydrothermal kettle, and a solvothermal reaction is carried out in a forced air drying oven, the reaction temperature is 120℃, and the reaction time is 5h; after the reaction is completed, the reaction kettle is cooled to room temperature, and then the obtained CC / NiCo-LDH precursor is ultrasonically cleaned for 1min, and then is washed with deionized water and ethanol for 5 times, respectively, to remove impurities remaining in the CC / NiCo-LDH precursor; finally, the CC / NiCo-LDH precursor is dried in a 60℃ vacuum drying oven for 12h to obtain the CC / NiCo-LDH precursor;

[0052] Step 5: 2 g of NaH2PO2·H2O powder was placed in a porcelain boat and placed in the gas inlet end of a double-zone controlled quartz tube furnace, and the CC / NiCo-LDH precursor was placed in a porcelain boat and placed in the gas outlet end, then a continuous argon gas flow with a flow rate of 60 mL / min was introduced, the heating rate was 5 ℃ / min, the reaction temperature was 350 ℃, and the reaction time was 3 h; after the reaction was completed, the sample was taken out after the temperature of the double-zone controlled quartz tube furnace was reduced to room temperature, to obtain Ni-doped CoP (CC / Ni-CoP);

[0053] Step 6: Diethylzinc (Zn(C2H5)2) was selected as the precursor of Zn, H2O was used as the oxidant, and the deposition temperature was set to 150 ℃. First, in a vacuum environment, the Zn(C2H5)2 vapor was introduced into the reaction chamber for 10 s with a precursor pulse of 0.02 s to allow the Zn(C2H5)2 precursor to fully react with the surface of the CC / Ni-CoP; secondly, an Ar gas inert carrier gas with a flow rate of 50 mL / min was introduced to purge the chamber for 60 s to remove unreacted Zn(C2H5)2 precursor or reaction byproducts. Subsequently, the H2O in the reaction chamber was allowed to undergo a redox reaction with the chemisorbed Zn(C2H5)2 on the CC / Ni-CoP with a precursor pulse of 0.02 s for 10 s; finally, an Ar gas inert carrier gas with a flow rate of 50 mL / min was introduced to purge the chamber for 60 s to blow the byproducts and excess ethane molecules on the CC / Ni-CoP away from its surface, thereby depositing a layer of ZnO on the CC / Ni-CoP. The deposition rate of ZnO was 0.1 nm / cycle, the thickness of the deposited ZnO layer was 0.1 nm, and the number of cycles of deposition was 60, until a 6 nm thick ZnO coating layer was deposited on the surface of the CC / Ni-CoP, to obtain a CC / Ni-CoP@ZnO flexible electrode;

[0054] Figure 1 Fig. 1 is a SEM image of the CC / Ni-CoP and the CC / Ni-CoP@ZnO flexible electrode prepared according to Example 2. As can be seen from Fig. 1a, the Ni-doped CoP nanoneedle array is uniformly and densely arranged on the conductive carbon fiber; as can be seen from Fig. 1b, the Ni-doped CoP nanoneedles are interconnected to form a three-dimensional network structure, exposing more reaction active sites. As can be seen from Fig. 1c, the CC / Ni-CoP@ZnO flexible electrode prepared according to Example 2 still retains the nanoneedle network structure, indicating that the ALD coating technology does not change the morphology of the Ni-doped CoP.

[0055] Figure 2is the electrochemical performance diagram of the CC / Ni-CoP@ZnO flexible electrode prepared according to the application of embodiment 2. As can be seen from the dotted line diagram a, with the increase of the scanning rate, the oxidation peak and the reduction peak move to higher and lower potentials respectively, which is mainly due to the increase of the diffusion resistance of the electrode and electrolyte interface; in addition, with the increase of the scanning rate, the integral area of the CV curve increases, but the shape of the CV curve does not change, indicating that the CC / Ni-CoP@ZnO flexible electrode has high reversibility; as can be seen from the dotted line diagram b, the GCD curve of the CC / Ni-CoP@ZnO flexible electrode is almost symmetrical, indicating that the reversibility of the electrode reaction is good.

[0056] Embodiment 3:

[0057] A high-performance ZnO-coated Ni-doped CoP acicular network structure flexible electrode is prepared by a solvothermal method, a low-temperature phosphating method and an ALD coating technology, wherein the number of cycles of cyclic deposition of ZnO on the CC / Ni-CoP is 80 cycles, and the thickness of the deposited ZnO coating layer is 8nm;

[0058] A preparation method of a high-performance ZnO-coated Ni-doped CoP acicular network structure flexible electrode, comprising the following steps:

[0059] Step 1: first, 1×2cm 2 The carbon cloth is subjected to ultrasonic acidification treatment with a 3mol / L HCl aqueous solution for 50min, and then is subjected to ultrasonic cleaning with acetone, ethanol and deionized water for 40min respectively, and is dried in a drying oven at 70℃ for 12h to obtain a surface pretreated carbon cloth (CC);

[0060] Step 2: 5mL of ethanol is added to 20mL of deionized water, and stirred on a magnetic stirrer at a speed of 400r / min for 15min to obtain a mixed solution of ethanol and deionized water;

[0061] Step 3: 0.5mol of Ni(NO3)2·6H2O, 2.5mol of Co(NO3)2·6H2O and 4.0mol of urea are sequentially added to the above mixed solution, and stirred on a magnetic stirrer at a speed of 450r / min for 180min to obtain a pink homogeneous solution;

[0062] Step 4: Pour the pink homogeneous solution obtained above into a polytetrafluoroethylene liner, then put the surface pretreated carbon cloth (CC) obtained above into the homogeneous solution, and the filling ratio of the mixed solution in the polytetrafluoroethylene liner is 50%; then seal the polytetrafluoroethylene liner with a stainless steel hydrothermal kettle, and carry out a solvothermal reaction in a forced air drying oven, the reaction temperature is 120°C, and the reaction time is 5h; after the reaction is completed, the CC / NiCo-LDH precursor obtained is ultrasonically cleaned for 2min, and then washed with deionized water and ethanol for 4 times respectively to remove the impurities remaining on the CC / NiCo-LDH precursor; finally, dry the CC / NiCo-LDH precursor in a vacuum drying oven at 70°C for 14h to obtain the CC / NiCo-LDH precursor;

[0063] Step 5: Put 2g of NaH2PO2·H2O powder into a porcelain boat and place it in the gas inlet end of a double-temperature zone controlled quartz tube furnace, and then put the CC / NiCo-LDH precursor into a porcelain boat and place it in the gas outlet end, then pass in a continuous argon gas flow with a flow rate of 80mL / min, the heating rate is 3°C / min, the reaction temperature is 350°C, and the reaction time is 3h; after the reaction is completed, the temperature of the double-temperature zone controlled quartz tube furnace is reduced to room temperature, and the sample is taken out to obtain Ni-doped CoP (CC / Ni-CoP);

[0064] Step 6: Diethyl zinc (Zn(C2H5)2) is selected as the precursor of Zn, H2O is used as the oxidant, and the deposition temperature is set to 150°C; first, in a vacuum environment, the Zn(C2H5)2 vapor is introduced into the reaction chamber for 10s with a precursor pulse of 0.02s to make the Zn(C2H5)2 precursor fully react with the surface of the CC / Ni-CoP; secondly, an Ar gas inert carrier gas with a flow rate of 50mL / min is introduced to purge the chamber for 60s to remove unreacted Zn(C2H5)2 precursor or reaction byproducts; then, the H2O in the reaction chamber is oxidized and reduced with the Zn(C2H5)2 chemisorbed on the CC / Ni-CoP with a precursor pulse of 0.02s for 10s; finally, an Ar gas inert carrier gas with a flow rate of 50mL / min is introduced to purge the chamber for 60s to blow the byproducts and excess ethane molecules on the CC / Ni-CoP away from its surface, thereby depositing a layer of ZnO on the CC / Ni-CoP; wherein the deposition rate of ZnO is 0.1nm / cycle, the thickness of the deposited ZnO layer is 0.1nm, and the cycle number of deposition is 80, until a ZnO coating layer with a thickness of 8nm is deposited on the surface of the CC / Ni-CoP, to obtain a CC / Ni-CoP@ZnO flexible electrode.

[0065] Figure 3are XRD diffraction patterns of CC / Ni-CoP prepared by the present application and CC / Ni-CoP@ZnO flexible electrodes prepared according to the examples. As can be seen from curve a, all diffraction peaks of CC / Ni-CoP except the characteristic diffraction peaks of carbon cloth (CC) are consistent with the standard card of CoP (JCPDS NO. 89-2598), and the peak position is offset to a large angle, which is mainly due to the fact that the atomic radius of doped Ni is smaller than that of Co atom, and Ni atoms occupy Co atom sites, resulting in a decrease in the interplanar spacing of CoP; as can be seen from curves b-d, the diffraction peaks of CC / Ni-CoP@ZnO flexible electrodes can detect the characteristic diffraction peaks of ZnO (JCPDS NO. 79-0205) coating layer in addition to the characteristic peaks of CoP (JCPDS NO. 89-2598), which indicates that ZnO is successfully coated on the surface of CC / Ni-CoP.

[0066] Figure 4 are cyclic voltammograms of CC / Ni-CoP prepared by the present application and CC / Ni-CoP@ZnO flexible electrodes prepared according to the examples at a scanning speed of 30 mV s -1 -1. As can be seen from the figure, CC / Ni-CoP prepared by the present application and CC / Ni-CoP@ZnO flexible electrodes prepared according to the examples both have obvious redox peaks, which are mainly due to the reversible redox reaction of Ni 2+ / Ni 3+ and Co 2 + / Co 3+ electron pairs. As can be seen from the figure, the dotted line graph c, i.e. CC / Ni-CoP@ZnO flexible electrode prepared according to Example 2 of the present application, has the largest cyclic voltammetry integral area and stronger peak current, which indicates that CC / Ni-CoP@ZnO flexible electrode with a 6 nm thick ZnO coating layer exhibits stronger electrochemical activity and greater energy storage capacity.

[0067] Figure 5 are constant current charge-discharge curves of CC / Ni-CoP prepared by the present application and CC / Ni-CoP@ZnO flexible electrodes prepared according to the examples at a current density of 1 A g -1 -1. As can be seen from the figure, the dotted line graph c, i.e. CC / Ni-CoP@ZnO flexible electrode prepared according to Example 2 of the present application, has a longer charge-discharge time, indicating that CC / Ni-CoP@ZnO flexible electrode prepared according to Example 2 has a higher specific capacity.

[0068] Figure 6is a plot of the mass specific capacity of the CC / Ni-CoP prepared according to the present application and the CC / Ni-CoP@ZnO flexible electrode prepared according to Example 2 at different current densities. As can be seen from the dotted line graph a, the capacity of the CC / Ni-CoP flexible electrode can be maintained at 76.8% of the initial specific capacity when the current density is increased from 1 A g -1 to 15 A g -1 As can be seen from the dotted line graph c, the capacity of the CC / Ni-CoP@ZnO flexible electrode prepared according to Example 2 can be maintained at 99.4% of the initial specific capacity when the current density is increased from 1 A g -1 to 15 A g -1 In addition, as can be seen from the graph, the CC / Ni-CoP@ZnO flexible electrode prepared according to Example 2 exhibits the highest mass specific capacity, which can be as high as 850 C g -1 at 1 A g -1 This indicates that the adoption of the ALD method to coat a 6 nm ultra-thin ZnO layer on the surface of the nano-needle network structure CC / Ni-CoP according to Example 2 can effectively improve the mass specific capacity and rate performance of the CC / Ni-CoP@ZnO flexible electrode.

[0069] Figure 7 is a plot of the cycle stability of the CC / Ni-CoP prepared according to the present application and the CC / Ni-CoP@ZnO flexible electrode prepared according to Example 2 at a current density of 15 A g -1 As can be seen from the dotted line graph a, the capacity of the CC / Ni-CoP flexible electrode can be maintained at 33% of the initial specific capacity after 5000 cycles; as can be seen from the dotted line graph b, the capacity of the CC / Ni-CoP@ZnO flexible electrode prepared according to Example 2 can be maintained at 52.66% of the initial specific capacity after 5000 cycles, which indicates that the CC / Ni-CoP@ZnO flexible electrode prepared according to Example 2 has relatively good cycle stability, which is mainly due to the fact that the ultra-thin ZnO coating layer can buffer the volume expansion of the nano-needle network structure CC / Ni-CoP during long-term charging and discharging, thereby improving the cycle stability.

Claims

1. A method for preparing a ZnO-coated Ni-doped CoP needle-like network structure flexible electrode, characterized in that, Specifically, a needle-like network structure of Ni-doped CoP is first grown on carbon cloth, i.e., CC / Ni-CoP is first prepared, and then ZnO ultrathin film is deposited on CC / Ni-CoP by ALD technology to prepare CC / Ni-CoP@ZnO flexible electrode. The specific steps are as follows: Step 1: The carbon cloth is subjected to ultrasonic acidification, followed by ultrasonic cleaning and drying to obtain surface-pretreated carbon cloth CC. Step 2: Add ethanol to deionized water and stir evenly on a magnetic stirrer to obtain a mixed solution of ethanol and deionized water; Step 3: Add a certain amount of Ni(NO3)2·6H2O, Co(NO3)2·6H2O and urea to the above mixed solution in sequence, and stir evenly on a magnetic stirrer to obtain a pink homogeneous solution; Step 4: Pour the pink homogeneous solution obtained in Step 3 into a polytetrafluoroethylene liner, then place the carbon cloth CC pretreated in Step 1 into the homogeneous solution, seal it with a stainless steel hydrothermal reactor, and carry out a solvothermal reaction in a forced-air drying oven; after the reaction is completed, cool the reactor to room temperature to obtain the CC / NiCo-LDH precursor, place it in deionized water for ultrasonic cleaning, then rinse it several times with deionized water and ethanol respectively, and finally dry it in a vacuum drying oven; Step 5: Place a certain amount of NaH2PO2·H2O powder into a ceramic boat and place it at the gas inlet end of a dual-temperature zone controlled quartz tube furnace. Then, place the CC / NiCo-LDH precursor into the ceramic boat and place it at the gas outlet end. Introduce a continuous argon flow and raise the temperature to a certain level at a certain heating rate for phosphating treatment. After the reaction is complete, Ni-doped CoP, i.e., CC / Ni-CoP, is obtained. Step 6: Deposit a ZnO ultrathin film on the CC / Ni-CoP prepared in step 5 using ALD technology; Step 1 specifically involves: dividing 1×2 cm 2 The carbon cloth was ultrasonically acidified with HCl aqueous solution, then ultrasonically cleaned with acetone, ethanol and deionized water respectively, and dried to obtain the surface-pretreated carbon cloth. The molar concentration of the HCl aqueous solution is 3~5 mol / L; the ultrasonic acidification treatment time is 30~60 min; the ultrasonic cleaning time is 30~50 min; the drying temperature is 50~80 ℃, and the drying time is 6~14 h; In step 3, the molar ratio of Ni(NO3)2·6H2O to Co(NO3)2·6H2O is 1:5, and the molar ratio of the total amount of Ni(NO3)2·6H2O and Co(NO3)2·6H2O to urea is 3:4; the rotation speed of the magnetic stirrer is 350~550 r / min, and the stirring time is 150~180 min; In step 4, the solvothermal reaction temperature is 120 °C and the reaction time is 5 h; the filling ratio of the mixed solution in the polytetrafluoroethylene liner is 50%; the ultrasonic cleaning time is 1~2 min; the solution is rinsed with deionized water and ethanol 4~6 times respectively; the drying temperature is 50~70 °C and the vacuum drying time is 10~16 h. In step 5, the carbon cloth area (cm²) 2 The mass ratio of NaH2PO2·H2O powder to NaH2PO2·H2O powder is 1:(1~3); the flow rate of argon gas is 50~100 mL / min; the heating rate is 1~5 ℃ / min; the reaction temperature is 350 ℃; and the reaction time is 3 h. Step 6 specifically involves: selecting diethylzinc (Zn(C2H5)2) as the Zn precursor, using H2O as the oxidant, and setting the deposition temperature. First, under vacuum, a precursor pulse is applied for a certain duration to allow Zn(C2H5)2 vapor to enter the reaction chamber and react for a certain time. Then, Ar inert carrier gas is introduced at a certain flow rate and for a certain time to purge the chamber. Subsequently, a precursor pulse is applied for a certain duration to allow the H2O in the reaction chamber to undergo a redox reaction with the chemically adsorbed Zn(C2H5)2 on the CC / Ni-CoP, allowing the reaction to proceed for a certain time. Finally, Ar inert carrier gas is introduced at a certain flow rate and for a certain time to deposit a ZnO layer on the CC / Ni-CoP. This process is repeated several times until a ZnO coating layer of a certain thickness is obtained, resulting in a CC / Ni-CoP@ZnO flexible electrode. In step 6, the deposition temperature is 150 °C, the precursor pulse duration is 0.02 s, and the reaction time is 10 s; the flow rate of the Ar inert carrier gas is 50 mL / min, and the blow-off time is 60 s; the deposition rate of ZnO is 0.1 nm / cycle, the thickness of the deposited ZnO layer is 0.1 nm, the number of cycle depositions is 20~120 cycles, and the thickness of the deposited ZnO coating layer is 2~12 nm.

2. The method for preparing a ZnO-coated Ni-doped CoP needle-like network structure flexible electrode according to claim 1, characterized in that, In step 2, the volume ratio of ethanol to deionized water is 1:4; the magnetic stirrer speed is 250~450 r / min, and the stirring time is 10~15 min.

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