CdS-NiCo-LDH composite material and preparation method and application thereof

Abstract

The invention relates to the technical field of composite materials, in particular to a CdS-NiCo-LDH composite material and a preparation method and application thereof. According to the preparation method disclosed by the invention, NiCo-LDH is firstly obtained through hydrothermal reaction, and then CdS nanodots are introduced into NiCo-LDH interlayers through electrochemical reaction and in-situ vulcanization, so that the interlayer spacing is increased, and OH <-> transportation is facilitated; due to the construction of the CdS nanodots, the conductivity of the CdS nanodots is improved, electron migration of the CdS nanodots is facilitated, and electrochemical reaction active sites are increased. Meanwhile, the in-situ synthesis method not only avoids the adverse effect of secondary growth, but also reduces the volume expansion of NiCo-LDH in the oxidation-reduction reaction process.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and in particular to a CdS-NiCo-LDH composite material and a preparation method and application thereof. Background Art

[0002] The non-renewable nature of fossil energy and increasingly serious environmental concerns have prompted increasing interest in sustainable energy conversion and storage technologies. Supercapacitors, due to their long cycle life and high output power, are widely used in applications requiring high power output. However, their relatively limited energy density is a key obstacle to large-scale commercial application. To overcome this technological bottleneck, the development of advanced electrode materials with efficient electron / ion transport capabilities has become a research priority.

[0003] Layered double hydroxides (LDHs), a special class of layered materials, consist of several positively charged layers with anions that balance the charge. They have attracted considerable attention in the field of supercapacitors due to their readily variable composition, easily tunable structure, and ease of functionalization through composites with other materials. Despite their promising properties, LDHs face two significant limitations in energy storage: poor conductivity and a limited number of active sites. Summary of the Invention

[0004] Based on this, the present invention provides a CdS-NiCo-LDH composite material and a preparation method and application thereof, which at least solves one problem in the prior art.

[0005] In a first aspect, the present invention provides a method for preparing a CdS-NiCo-LDH composite material, comprising the following steps: Mixing a soluble nickel salt, a soluble cobalt salt, ammonium fluoride and water to obtain a solution A; Mix urea and water to obtain solution B; Mix the above solution A and solution B to obtain solution C; The carrier and the above-mentioned C solution were placed in a reactor and subjected to a hydrothermal reaction at 90°C-160°C to obtain a carrier loaded with NiCo-LDH; The NiCo-LDH-loaded carrier is used as an electrode and placed in a soluble cadmium salt solution. A voltage is applied to the electrode to form a Cd 2+ -NiCo-LDH; The above Cd 2+ -NiCo-LDH was immersed in a sulfide solution to obtain a CdS-NiCo-LDH composite material.

[0006] In the present invention, NiCo-LDH is first obtained by hydrothermal reaction, and then CdS nanodots are introduced into the NiCo-LDH interlayer through electrochemical reaction and in-situ sulfurization to increase the interlayer spacing, which is beneficial to OH - The construction of CdS nanodots improves its conductivity, facilitates electron migration, and increases the number of active sites for electrochemical reactions. At the same time, the in-situ synthesis method not only avoids the adverse effects of secondary growth but also reduces the volume expansion of NiCo-LDH during the redox reaction.

[0007] In some optional embodiments, the soluble nickel salt is nickel acetate, nickel nitrate, nickel chloride, or nickel sulfate, and the soluble cobalt salt is cobalt acetate, cobalt nitrate, cobalt chloride, or cobalt sulfate. Preferably, the soluble nickel salt is nickel chloride, and the soluble cobalt salt is cobalt chloride.

[0008] In some optional embodiments, the molar ratio of the soluble cobalt salt, the soluble nickel salt, ammonium fluoride, and urea is 1:(3-6):(12-16):(19-30). Preferably, the molar ratio of the soluble cobalt salt, the soluble nickel salt, ammonium fluoride, and urea is 1:3:12:19.2.

[0009] In some optional embodiments, the carrier is nickel foam, carbon cloth or graphite plate.

[0010] In some optional embodiments, the hydrothermal reaction is carried out at 120°C.

[0011] In some optional embodiments, the soluble cadmium salt solution is cadmium acetate solution, cadmium nitrate solution, cadmium chloride solution or cadmium sulfate solution. Preferably, the soluble cadmium salt solution is cadmium chloride solution.

[0012] In some optional embodiments, the concentration of the soluble cadmium salt solution is 0.1-1.5 M. Preferably, the concentration of the soluble cadmium salt solution is 0.5M.

[0013] In some optional embodiments, the above-mentioned applied voltage refers to a voltage range of 0-1V at 20mV s -1 Preferably, the above-mentioned applied voltage refers to a voltage range of 0-1V at 20mV s -1 The scanning speed cycles 8 times.

[0014] In some optional embodiments, the sulfide solution is a sodium sulfide solution or a potassium sulfide solution. Preferably, the sulfide solution is a sodium sulfide solution.

[0015] In some optional embodiments, the concentration of the sulfide solution is 0.3-0.5M.

[0016] In some optional embodiments, the temperature of the sulfide solution is 0-20° C. Preferably, the temperature of the sulfide solution is 5° C.

[0017] In a second aspect, the present invention provides a CdS-NiCo-LDH composite material, which is obtained by the above-mentioned preparation method of the CdS-NiCo-LDH composite material.

[0018] In a third aspect, the present invention provides application of the above-mentioned CdS-NiCo-LDH composite material in a supercapacitor.

[0019] In a fourth aspect, the present invention provides a supercapacitor comprising the above-mentioned CdS-NiCo-LDH composite material.

[0020] Due to the adoption of the above technical solution, the embodiments of the present invention have at least the following beneficial effects: CdS nanodots are introduced into NiCo-LDH for the first time, so that the high conductivity of sulfide and the fast ion transport rate of LDH are synergistically combined to give the CdS-NiCo-LDH composite material excellent performance; when the CdS-NiCo-LDH composite material is used as an electrode, its -1 It can show 2637 F g at a current density of -1 specific capacitance performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a graph showing the changes in electrode specific capacitance of 0.1M-8-CdS-NiCo-LDH, 0.3M-8-CdS-NiCo-LDH, 0.5M-8-CdS-NiCo-LDH, 1M-8-CdS-NiCo-LDH, and 1.5M-8-CdS-NiCo-LDH at different current densities in an embodiment of the present invention.

[0022] Figure 2 This is a graph showing the changes in electrode specific capacitance of 0.5M-2-CdS-NiCo-LDH, 0.5M-4-CdS-NiCo-LDH, 0.5M-8-CdS-NiCo-LDH, 0.5M-12-CdS-NiCo-LDH, and 0.5M-16-CdS-NiCo-LDH at different current densities in an embodiment of the present invention.

[0023] Figure 3 NiCo-LDH, Cd 2+ -XRD patterns of NiCo-LDH and 0.5M-8-CdS-NiCo-LDH.

[0024] Figure 4 for Figure 3 A partial enlarged view of .

[0025] Figure 5 NiCo-LDH, Cd 2+ -XPS characteristic diagrams of NiCo-LDH and 0.5M-8-CdS-NiCo-LDH.

[0026] Figure 6 These are the SEM images and HR-TEM images of NiCo-LDH and 0.5M-8-CdS-NiCo-LDH in the examples of the present invention.

[0027] Figure 7 These are the EDS images of NiCo-LDH and 0.5M-8-CdS-NiCo-LDH in the examples of the present invention.

[0028] Figure 8 1 is a cyclic voltammogram of NiCo-LDH and 0.5M-8-CdS-NiCo-LDH in an embodiment of the present invention.

[0029] Figure 9 1 is the Nyquist plot of NiCo-LDH and 0.5M-8-CdS-NiCo-LDH in the embodiment of the present invention.

[0030] Figure 10 Graph showing changes in electrode specific capacitance of NiCo-LDH and 0.5M-8-CdS-NiCo-LDH at different current densities in an embodiment of the present invention.

[0031] Figure 11 This is a graph showing the cycling performance of the electrodes of NiCo-LDH and 0.5M-8-CdS-NiCo-LDH at 5000 cycles in an embodiment of the present invention.

[0032] Figure 12 Graphs of capacitance-current (IDL) of NiCo-LDH and 0.5M-8-CdS-NiCo-LDH at different scan rates at 0.3 V in an embodiment of the present invention are shown.

[0033] Figure 13 The NiCo-LDH and 0.5M-8-CdS-NiCo-LDH loadings in the present invention are 1 mg cm -2 Tafel diagram of the time.

[0034] Figure 14 Schematic diagram of the structure of the supercapacitor in an embodiment of the present invention.

[0035] Figure 15 The results are shown in Figure 2. The 0.5M-8-CdS-NiCo-LDH and AC electrode in the embodiment of the present invention are shown in Figure 2. -1 CV curve of the electrode.

[0036] Figure 16 The CdS-NiCo-LDH / / AC in the embodiment of the present invention is 10-100 mV s -1 CV curves at different scan rates within the same range.

[0037] Figure 17 Graph showing the specific capacitance of CdS-NiCo-LDH / / AC at different current densities in an embodiment of the present invention.

[0038] Figure 18 This is a diagram of the optimal energy density of CdS-NiCo-LDH / / AC at different power densities in an embodiment of the present invention.

[0039] Figure 19 This is a device cycle performance diagram of CdS-NiCo-LDH / / AC at 3500 cycles in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The following is a clear and complete description of the concept of the present invention and the technical effects produced, so as to fully explain the purpose, scheme and effects of the present invention.

[0041] Example 1 The CdS-NiCo-LDH composite was prepared by the following steps: (1) Preparation of NiCo-LDH NiCl2•6H2O (0.45 mmol), CoCl3•6H2O (0.15 mmol), and NH4F (1.8 mmol) were dissolved in 30 mL of deionized water and stirred at room temperature for 10 minutes to obtain solution A. Urea (2.88 mmol) was then dissolved in 30 mL of deionized water and stirred at room temperature for 10 minutes to obtain solution B. Solution A and solution B were then mixed and stirred for 10 minutes to obtain solution C. Solution C was transferred to a 100 mL reactor and a piece of nickel foam (1×3 cm) was placed in the reactor. 2 ) was placed therein, reacted at 120 °C for 5 h, and the product was collected and dried at 60 °C for 12 h to obtain NiCo-LDH supported by nickel foam.

[0042] (2) Cd 2+ Preparation of NiCo-LDH The electrochemical reaction of Cd was carried out in a three-electrode electrochemical system using a DH7000D electrochemical workstation with nickel foam loaded with NiCo-LDH as the working electrode, Hg / HgO electrode as the reference electrode, and platinum mesh electrode as the counter electrode. 2+ The cadmium source was selected as 0.1M CdCl2 solution. The voltage range was 0-1V with a speed of 20mV s -1The scanning speed was cycled for 8 cycles, and the product was washed with deionized water and dried in a vacuum drying oven at 60 ° C for 12 hours to obtain nickel foam supported Cd 2+ -NiCo-LDH.

[0043] (3) Preparation of CdS-NiCo-LDH Add Na2S·9H2O (1 g) to 40 mL of deionized water and stir for 10 minutes to obtain a sodium sulfide solution. 2+ -NiCo-LDH was immersed in sodium sulfide solution for 1 hour. The resulting product was washed with ethanol and dried in a vacuum drying oven at 60°C for 12 hours to obtain a CdS-NiCo-LDH composite material.

[0044] In this embodiment, the concentration of the CdCl2 solution is 0.1 M, the number of cycles is 8, and the final product CdS-NiCo-LDH composite material is labeled 0.1M-8-CdS-NiCo-LDH.

[0045] Example 2 This example is basically the same as Example 1, except that the concentration of the CdCl2 solution is replaced with 0.3M, and the final product CdS-NiCo-LDH composite material is labeled 0.3M-8-CdS-NiCo-LDH.

[0046] Example 3 This example is basically the same as Example 1, except that the concentration of the CdCl2 solution is replaced with 0.5M, and the final product CdS-NiCo-LDH composite material is labeled 0.5M-8-CdS-NiCo-LDH.

[0047] Example 4 This example is basically the same as Example 1, except that the concentration of the CdCl2 solution is replaced with 1M, and the final product CdS-NiCo-LDH composite material is labeled 1M-8-CdS-NiCo-LDH.

[0048] Example 5 This example is basically the same as Example 1, except that the concentration of the CdCl2 solution is replaced with 1.5 M, and the final product CdS-NiCo-LDH composite material is labeled 1.5 M-8-CdS-NiCo-LDH.

[0049] Example 6 This example is basically the same as Example 1, except that the concentration of the CdCl2 solution is replaced with 0.5 M, the number of cycles is replaced with 2, and the final product CdS-NiCo-LDH composite material is labeled 0.5 M-2-CdS-NiCo-LDH.

[0050] Example 7 This example is basically the same as Example 1, except that the concentration of the CdCl2 solution is replaced with 0.5 M, the number of cycles is replaced with 4, and the final product CdS-NiCo-LDH composite material is labeled 0.5 M-4-CdS-NiCo-LDH.

[0051] Example 8 This example is basically the same as Example 1, except that the concentration of the CdCl2 solution is replaced with 0.5 M, the number of cycles is replaced with 12, and the final product CdS-NiCo-LDH composite material is labeled 0.5M-12-CdS-NiCo-LDH.

[0052] Example 9 This example is basically the same as Example 1, except that the concentration of the CdCl2 solution is replaced with 0.5 M, the number of cycles is replaced with 16, and the final product CdS-NiCo-LDH composite material is labeled 0.5M-16-CdS-NiCo-LDH.

[0053] The electrochemical properties of 0.1M-8-CdS-NiCo-LDH, 0.3M-8-CdS-NiCo-LDH, 0.5M-8-CdS-NiCo-LDH, 1M-8-CdS-NiCo-LDH, and 1.5M-8-CdS-NiCo-LDH were tested. The results are as follows: Figure 1 It can be seen that when the concentration of CdCl2 solution is 0.5M, the specific capacitance of CdS-NiCo-LDH composite material is the largest.

[0054] The electrochemical properties of 0.5M-2-CdS-NiCo-LDH, 0.5M-4-CdS-NiCo-LDH, 0.5M-8-CdS-NiCo-LDH, 0.5M-12-CdS-NiCo-LDH and 0.5M-16-CdS-NiCo-LDH were tested. Figure 2 As shown. It can be seen that the larger the CdS content, the better. Although CdS nanodots can act as OH - However, too much CdS will destroy the integrity of the LDH lattice, thus affecting the performance of the material.

[0055] The NiCo-LDH, Cd 2+ -NiCo-LDH, 0.5M-8-CdS-NiCo-LDH crystal structure, the scanning speed is 6 ° / min, the scanning angle is 10 ° -80 °. Figure 3As shown, the peak numbers between samples are basically consistent, indicating that the material preparation process did not significantly change the substance. Based on the comparison with the PDF-89-460 card, it is obvious that the main component of this material is NiCo-LDH. After in-situ sulfurization, the formation of CdS nanodots further expands the interlayer distance, which can be seen from the shift of the characteristic peak to a smaller angle ( Figure 4 ). The widened interlayer distance is beneficial to the OH - Ions shuttle between the brucite layers to achieve high-rate performance.

[0056] The X-ray photoelectron spectroscopy (XPS) was used to observe the NiCo-LDH and Cd 2+ -NiCo-LDH, 0.5M-8-CdS-NiCo-LDH element valence, composition and electronic structure changes, the results are as follows Figure 5 After fitting the Ni 2P, Co 2P and O1s of the XPS test data, it can be found that 0.5M-8-CdS-NiCo-LDH, Cd 2+ -NiCo-LDH and NiCo-LDH show great similarity, which indicates that the original structure and properties of NiCo-LDH have not been significantly damaged during the material preparation process, which is consistent with the XRD test results. 2+ After low-temperature sulfurization of 0.5M-8-CdS-NiCo-LDH, the diffraction peak of 0.5M-8-CdS-NiCo-LDH shifts toward the direction of lower electron binding energy, which indicates that Cd 2+ The O 1s peak shifted to a lower binding energy after CdS was inserted into NiCo-LDH, indicating that the electron density around the O atoms increased.

[0057] The microstructure and elemental distribution of NiCo-LDH and 0.5M-8-CdS-NiCo-LDH were analyzed using scanning electron microscopy (Nova NaNoSEM450), transmission electron microscopy (FEI Talos F200X), and high-resolution electron microscopy (HRTEM). The surface states of NiCo-LDH and 0.5M-8-CdS-NiCo-LDH were analyzed using XPS (Axis Ultra DLD).

[0058] Figure 6 Figures a and b are SEM images of NiCo-LDH. It can be seen that dense nanosheets grow on the typical rod-like structure. This structure is the growth scaffold of NiCoLDH, which can effectively prevent agglomeration, promote the effective transmission of ions / electrons, and reduce stress concentration during charging and discharging. Figure 6Figures d and e are scanning electron microscope images of 0.5M-8-CdS-NiCo-LDH. It can be seen that the nanostructure of 0.5M-8-CdS-NiCo-LDH has not changed compared to NiCoLDH, which indicates that the introduction of CdS nanodots has not destroyed the morphology of NiCo-LDH. However, the difference between NiCo-LDH and 0.5M-8-CdS-NiCo-LDH is still clearly visible. The surface of NiCo-LDH is smooth, while the surface of 0.5M-8-CdS-NiCo-LDH is rough. The particles existing in the interstitial space on the surface of NiCo-LDH are CdS nanoparticles. Their introduction increases the conductivity and expands the interlayer spacing, which is beneficial to the improvement of related electrochemical performance. Figure 6 c in the figure is the HR-TEM image of NiCo-LDH. Figure 6 Figure f is an HR-TEM image of 0.5M-8-CdS-NiCo-LDH. It can be seen that the interlayer spacing of NiCo-LDH is 0.216nm, while the interlayer spacing of 0.5M-8-CdS-NiCo-LDH is 0.232nm. The introduction of CdS nanodots successfully improved the conductivity and increased the interlayer spacing.

[0059] Figure 7 g and h in the figure are energy dispersive X-ray spectroscopy (EDS) images of NiCo-LDH. Figure 7 Figures i, j, k, and l are energy dispersive X-ray spectroscopy (EDS) images of 0.5M-8-CdS-NiCo-LDH. It can be seen that the Ni, Co, S, and Cd elements are evenly distributed within the LDH.

[0060] The electrochemical performance of the electrode was evaluated on a DH7000D electrochemical workstation using 0.5M-8-CdS-NiCo-LDH as the working electrode, a carbon rod as the counter electrode, and Hg / HgO as the reference electrode in 1M KOH electrolyte (pH = 14). The specific capacitance was calculated using the following equation: Cs=(I·Δt) / (m·ΔV), Where I is the discharge current (A), Δt is the discharge time (s), ΔV is the potential range (V), and m is the mass of active material used (g).

[0061] For comparison, the electrochemical performance contribution of the NiCo-LDH sample was also measured and calculated.

[0062] First, cyclic voltammetry tests were performed on the samples at the same scan rate to explore the effect of interlayer nanodots on the current and capacitance responses, such as Figure 8 As shown, at 10mV s -1In this case, it is obvious that the cyclic voltammetry curve of 0.5M-8-CdS-NiCo-LDH is much larger than that of NiCo-LDH.

[0063] The cyclic voltammetry curves corresponding to different scan rates in the same potential window (0-0.8V) were tested, such as Figure 9 As shown in the figure, it can be seen that as the scan rate increases, the range of the cyclic voltammetry curve becomes larger, but the contour still shows the same shape, which shows its good rate performance. Electrochemical impedance spectroscopy (EIS) diagram is used to study the charge transfer ability and OH - Ion diffusion. After analysis, it can be determined that the impedance of 0.5M-8-CdS-NiCo-LDH is lower than that of NiCo-LDH. This is because the introduction of interlayer CdS nanodots leads to lower ion / electron transport limitations.

[0064] The capacitance performance of 0.5M-8-CdS-NiCo-LDH can be calculated in detail through the constant current charge-discharge (GCD) curve and compared with that of NiCo-LDH electrode material. Figure 10 As shown, at 1A g -1 At a current density of 2637 F g -1 ) is the specific capacitance of NiCo-LDH (765 F g -1 ) is 3.44 times that of NiCo-LDH. With the increase of current density, the specific capacitance of the sample also decreases, but the capacitance retention rate of 0.5M-8-CdS-NiCo-LDH (75%) is still better than that of NiCo-LDH (58%).

[0065] like Figure 11 As shown, 0.5M-8-CdS-NiCo-LDH at 10 A g −1 It also exhibits high cycling activity, with a capacity retention of 80.9% after 5000 cycles, which is significantly higher than the 40% capacity retention of NiCo-LDH under the same test conditions.

[0066] like Figure 12 As shown, 0.5M-8-CdS-NiCo-LDH exhibits a higher electrochemical active area than NiCo-LDH, further demonstrating the important contribution of CdS modification and intercalation to improving the efficiency of LDHs supercapacitors.

[0067] like Figure 13 As shown, the Tafel slope of 0.5M-8-CdS-NiCo-LDH (56 mV Dec -1 ) is much lower than the Tafel slope of NiCo-LDH (478 mV Dec -1), which in turn explains the enhanced redox kinetics. This is due to the fact that the interlayer NDs increase the activity of the inert inner surface of LDH, reduce the overpotential, and accelerate the redox process.

[0068] A hybrid supercapacitor is constructed using NiCo-LDH (positive electrode material), AC (negative electrode material, activated carbon), and 1M KOH (electrolyte), expressed as NiCo-LDH / / AC; wherein the mass loading ratio of NiCo-LDH to AC is matched to 1:9. Figure 14 As shown in Figure 1, a hybrid supercapacitor is constructed using 0.5M-8-CdS-NiCo-LDH (positive electrode material), AC (negative electrode material, activated carbon), and 1M KOH (electrolyte), expressed as CdS-NiCo-LDH / / AC; where the mass loading ratio of 0.5M-8-CdS-NiCo-LDH to AC is matched to 1:9. The energy density (E) and power density (P) of the device are calculated using the following integral formula: E=(I / m)∫V(t)dt P=E / Δt Where I is the discharge current (A), m is the total mass of the positive and negative electrode materials (g), ∫V(t)dt is the area under the constant current discharge curve (V·s-1), and Δt is the discharge time (s).

[0069] like Figure 15 As shown in Figure 2, 0.5M-8-CdS-NiCo-LDH and AC electrodes have a stable and compatible voltage window, proving the feasibility of the assembly. -1 Under stable operating voltage conditions, the negative electrode exhibits a potential window of (-1 V to 0 V), and the positive electrode exhibits a potential window of (0 V to 0.5 V), indicating that the operating voltage of the assembled device can be set to 1.5 V. The mass loading ratio of the positive and negative electrodes can be calculated as 0.11 according to the relevant formula.

[0070] Figure 16 It shows that CdS-NiCo-LDH / / AC has a high conductivity at 10-100 mV s -1 Figure 5 CV curves at different scan rates within a wide range. The formation of a redox peak (0–1.5 V) demonstrates that the device effectively combines the advantages of the Faradaic mechanism and EDLC behavior.

[0071] At the same time, if Figure 17 As shown in Figure 2, with the increase of scan rate, the shape of the CV curve changes little in the same voltage window, which indicates that the device (CdS-NiCo-LDH / / AC) has good electrochemical reversibility. The specific capacitance of the device decreases with the increase of current density. At 1 A g -1 When the specific capacitance is 85 F g -1; and in 5A g -1 When the specific capacitance is 60 Fg -1 When the current density increases fivefold, the capacitance retention of CdS-NiCo-LDH / / AC is 70%.

[0072] like Figure 18 As shown, at a power density of 1605 W kg -1 The optimal energy density of the device is 53.23 Whkg -1 Even if the power density increases to 39.04 kW kg -1 , and can also maintain 28.18 Wh kg -1 .

[0073] By 10 Ag -1 The stability of the electrode material was studied by 3500 charge / discharge cycles under Figure 19 The device sample still retained 63% of its initial capacity after 3500 cycles.

[0074] The above description is merely a preferred embodiment of the present invention. The present invention is not limited to the above-described embodiments. Any method that achieves the technical effects of the present invention by the same or equivalent means shall fall within the scope of protection of the present invention. Within the scope of protection of the present invention, various modifications and variations of the technical solutions and / or implementation methods are possible.

Claims

1. A method for preparing a CdS-NiCo-LDH composite material, characterized in that: The following steps are involved: Mixing a soluble nickel salt, a soluble cobalt salt, ammonium fluoride and water to obtain a solution A; Mix urea and water to obtain solution B; Mixing the solution A and the solution B to obtain a solution C; Placing the support and the C solution in a reactor, and performing a hydrothermal reaction at 90° C.-160° C. to obtain a support loaded with NiCo-LDH; The carrier loaded with NiCo-LDH is used as an electrode, placed in a soluble cadmium salt solution, and a voltage is applied to the electrode to form Cd 2+ -NiCo-LDH; The Cd 2+ -NiCo-LDH was immersed in a sulfide solution to obtain a CdS-NiCo-LDH composite material.

2. The method according to claim 1, characterized in that The soluble nickel salt is nickel acetate, nickel nitrate, nickel chloride or nickel sulfate, and the soluble cobalt salt is cobalt acetate, cobalt nitrate, cobalt chloride or cobalt sulfate.

3. The method according to claim 1, characterized in that The molar ratio of the soluble cobalt salt, the soluble nickel salt, ammonium fluoride and urea is 1:(3-6):(12-16):(19-30).

4. The method according to claim 1, wherein The soluble cadmium salt solution is cadmium acetate solution, cadmium nitrate solution, cadmium chloride solution or cadmium sulfate solution.

5. The method according to claim 1, characterized in that The concentration of the soluble cadmium salt solution is 0.1-1.5M.

6. The method according to claim 1, characterized in that The applied voltage is 20 mV s in the voltage range of 0-1 V. -1 The scanning speed cycles 2-16 circles.

7. The method according to claim 1, characterized in that The sulfide solution is a sodium sulfide solution or a potassium sulfide solution; the concentration of the sulfide solution is 0.3-0.5M.

8. A CdS-NiCo-LDH composite material, characterized in that: The composite material is obtained by the preparation method of the CdS-NiCo-LDH composite material according to any one of claims 1 to 7. 9 . Use of the CdS-NiCo-LDH composite material according to claim 8 in a supercapacitor.

10. A supercapacitor, characterized in that: The invention comprises the CdS-NiCo-LDH composite material according to claim 8.

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