Three-dimensional multilayer LDH / CS / PPy composite material and preparation method and application thereof

Abstract

The invention discloses a three-dimensional multi-layer LDH / CS / PPy composite material and a preparation method and application thereof.The composite material is of a multi-layer core-shell structure, a carbon sphere CS with the surface rich in functional groups serves as a structure guiding core, nickel-cobalt-aluminum layered double hydroxide NiCoAl-LDH is induced to grow in situ on the surface of the carbon sphere CS to form a uniformly-dispersed flower-shaped structure, and the composite material has the advantages that the structure of the structure guiding core is optimized; coating the surface of the composite material with a polypyrrole (PPy) conductive layer through an in-situ polymerization method to construct a three-dimensional conductive network; when the material is applied to assembly of asymmetric supercapacitors (LDH / CS / PPy / / AC), ultrahigh power density and energy density are achieved, a plurality of LEDs connected in parallel can be lightened, and the material can be used for constructing novel supercapacitors with high energy density, high power density and excellent cycling stability.

Description

Technical Field

[0001] This invention relates to a three-dimensional multilayer LDH / CS / PPy composite material, and also to a method for preparing the above-mentioned composite material and its application as an electrode material in the field of energy material preparation technology. Background Technology

[0002] Supercapacitors, as a novel electrochemical energy storage device, have shown broad application prospects in the field of energy storage due to their advantages such as high power density, rapid charge-discharge capability, and long cycle life. Their core energy storage mechanism includes double-layer adsorption on the electrode surface and redox reactions occurring in the active materials. Therefore, the performance of the electrode materials directly determines the energy storage efficiency, stability, and economy of the supercapacitor system.

[0003] Layered bimetallic hydroxides (LDHs), as typical anionic layered materials, possess a unique interlayer structure that enables efficient charge storage through ion exchange or redox reactions. Theoretically, they are ideal electrode materials for supercapacitors. However, their practical applications are limited by two major bottlenecks: first, the strong van der Waals forces between LDH layers easily lead to stacking and aggregation, preventing the active sites from being fully exposed; second, their poor conductivity results in low electron transport efficiency, making it difficult to meet practical requirements for energy storage performance and cycle stability. Therefore, how to overcome the performance limitations of LDH-based materials through structural design and compositional control has become an urgent problem to be solved in the field of supercapacitors. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a three-dimensional multilayer LDH / CS / PPy composite material, as well as a method for preparing the above composite material and its application as an electrode material in the field of energy material preparation technology.

[0005] Technical solution: The three-dimensional multilayer LDH / CS / PPy composite material of the present invention has a multilayer core-shell structure. The carbon spheres CS with functional groups on the surface serve as the structure guiding core, inducing the in-situ growth of nickel cobalt aluminum layered bimetallic hydroxide NiCoAl-LDH on its surface to form a uniformly dispersed flower-like structure. A polypyrrole PPy conductive layer is coated on the surface of the composite material by in-situ polymerization to construct a three-dimensional conductive network.

[0006] The preparation method of the above-mentioned three-dimensional multilayer LDH / CS / PPy composite material includes the following steps:

[0007] (1) Citric acid and urea are dissolved in deionized water and stirred to form a homogeneous solution. A hydrothermal reaction is carried out. After the reaction is completed, the product is purified by dialysis. After centrifugation and drying, nano-carbon spheres with functional groups on the surface are obtained.

[0008] (2) Nickel salt, cobalt salt, aluminum salt and ammonium fluoride are mixed and dissolved to form a metal salt solution; urea is dissolved to prepare a precipitant solution; the two solutions are mixed and subjected to hydrothermal reaction, and the reaction product is washed and dried to obtain nickel cobalt aluminum layered bimetallic hydroxide NiCoAl-LDH;

[0009] (3) Add the carbon ball material produced in step (1) to the metal salt solution of the product NiCoAl-LDH in step (2), and after being fully dispersed, mix with urea solution. Through hydrothermal reaction, the layered bimetallic hydroxide grows in situ on the surface of the carbon ball to obtain an LDH / CS composite material in which the carbon ball and the layered bimetallic hydroxide are tightly bonded.

[0010] (4) The composite material obtained in step (3) is uniformly dispersed in an aqueous solution, pyrrole monomer and surfactant are added, and after sufficient dispersion, an initiator solution prepared by oxidant and hydrochloric acid is added to carry out in-situ chemical oxidation polymerization reaction. After the reaction is completed, the product is washed and dried to obtain the three-dimensional multilayer LDH / CS / PPy composite material.

[0011] In step (1), the mass ratio of citric acid to urea is 7:5~7, the reaction vessel is heated at 160-180℃ for 4-5 hours, and the supernatant is taken and dried during the dialysis process.

[0012] In step (2), the mass ratio of nickel salt, cobalt salt, aluminum salt, ammonium fluoride and urea is 1~2:2~3:1.5:16:19.2; the urea solution is quickly poured into the metal salt solution, and the hydrothermal reaction is heated at 110-120℃ for 5-6 hours.

[0013] In step (3), the mass-to-volume ratio of carbon spheres, NiCoAl-LDH, and urea solution is 1-5:16.3:38.4. The concentration of CS is 1-5 mg / mL. -1 The hydrothermal reaction is carried out at 110-120℃ for 5-6 hours. (The point values ​​need to be appropriately expanded to range values.)

[0014] In step (4), the mass-volume ratio of LDH / CS composite material, pyrrole monomer, oxidant and hydrochloric acid is 1:0.15~3.5:0.9:8.5; the surfactant is hexadecyltrimethylammonium bromide and the oxidant is ammonium persulfate.

[0015] The aforementioned three-dimensional multilayer LDH / CS / PPy composite material can be used as an electrode material in the field of energy material preparation technology.

[0016] The prepared LDH / CS / PPy composite electrode material is used as the anode material of a high-performance supercapacitor, and an asymmetric supercapacitor is assembled with LDH / CS / PPy as the positive electrode and AC as the negative electrode.

[0017] Invention Principle: The three-dimensional multilayer LDH / CS / PPy composite material of this invention uses carbon spheres as a structure guiding agent to load flower-shaped LDH, and then uses PPy to construct a conductive network, forming a three-dimensional multilayer core-shell structured LDH-based composite electrode material (LDH / CS / PPy). This material is used as the anode of a supercapacitor, and its energy storage performance is systematically studied.

[0018] Specifically, carbon spheres (CS) play a crucial role as structure-directing agents in supercapacitor electrode materials. On one hand, their regular spherical structure provides a uniform substrate for LDH growth, effectively suppressing the stacking and agglomeration of LDH layers caused by strong van der Waals forces through steric hindrance. This allows LDH to be dispersed and loaded onto the carbon sphere surface in a flower-like morphology, significantly increasing the number of exposed electrochemical active sites. On the other hand, the abundant hydroxyl and carboxyl functional groups on the carbon sphere surface enhance interfacial interactions with LDH, improving compatibility and providing efficient channels for charge transfer. Furthermore, carbon's excellent chemical stability and conductivity not only maintain the structural integrity of the composite material but also act as a "bridge" for electron transport, helping to improve the overall conductivity of the electrode. This multi-effect mechanism of "structure guidance-dispersed loading-charge conduction" makes carbon spheres a core component for solving the problem of insufficient LDH active sites.

[0019] Meanwhile, polypyrrole (PPy), as a typical conjugated conductive polymer, possesses excellent conductivity, environmental stability, and ease of preparation. The pyrrole rings and nitrogen atoms in its molecular structure can form specific interactions with electrolyte ions through electrostatic forces and ion exchange, providing abundant active sites for charge storage. The introduction of the PPy conductive layer enhances the interfacial charge transfer rate and improves the ion storage capacity of the composite material. The introduction of the conductive polymer can further compensate for the insufficient conductivity of LDH. PPy can not only form a continuous three-dimensional conductive network through in-situ polymerization and coat the surface of the LDH / CS composite material, significantly reducing the charge transfer resistance of the electrode, but also accelerate the electron transport efficiency within the material.

[0020] The aforementioned materials, carbon spheres, LDH, and PPy, synergistically construct a unique three-dimensional multi-layered core-shell structure. In this system, carbon spheres, acting as a structure-directing agent and conductive framework, guide the growth of LDH into a highly dispersed flower-like nanostructure through their regular spherical template and steric hindrance effect, effectively inhibiting its stacking and aggregation, and greatly increasing the exposure of electrochemical active sites. Simultaneously, the functional groups on the surface of the carbon spheres enhance interfacial bonding, and their excellent conductivity provides a preliminary bridge for charge transfer. PPy, through in-situ polymerization, forms a complete and continuous conductive coating layer on the LDH / CS surface, not only constructing a three-dimensional high-speed electron transport network penetrating the electrode and significantly reducing charge transfer resistance, but also contributing additional pseudocapacitance through reversible redox reactions by its active groups, compensating for the insufficient intrinsic conductivity of LDH. The resulting multi-layered structure of "CS core-LDH intermediate layer-PPy shell" further integrates hierarchical pores and hydrophilic interfaces, achieving a significant expansion of ion transport channels and a deep fusion of electron-ion dual continuous transport pathways. This synergistic design resulted in a composite material with an increased number of active sites (ECSA = 5.45 mF cm⁻¹). -2 ), electronic conductivity (R) ct =2.57 Ω), ion diffusion efficiency (D OH- =5.8×10⁻¹⁴ cm² s⁻¹) and structural stability have been comprehensively improved, thus endowing it with comprehensive energy storage characteristics of high specific capacitance, excellent rate performance and long cycle life.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The three-dimensional multilayer LDH / CS / PPy composite material of the present invention has the following advantages in 1 A g -1 At current density, the specific capacitance of the electrode can reach 1789 F g⁻¹, with excellent rate performance. It can also maintain 92% of its initial capacity after cyclic charge and discharge tests, showing excellent energy storage performance and stability. (2) It is used to assemble asymmetric supercapacitors (LDH / CS / PPy / / AC) with ultra-high power density and energy density. It can light up multiple parallel LEDs and can be used to build a new type of supercapacitor with high energy density, high power density and excellent cycle stability. Attached Figure Description

[0022] Figure 1 The XRD pattern of the prepared sample;

[0023] Figure 2 The SEM spectra of the prepared samples are shown, where (a) is CS, (b) is LDH, (c) is LDH / CS, and (d) is LDH / CS / PPy.

[0024] Figure 3The CV plot (a) and GCD plot (b) of the prepared sample are shown.

[0025] Figure 4 Electrochemical impedance spectroscopy for LDH, LDH / PPy, LDH / CS, and LDH / CS / PPy electrodes;

[0026] Figure 5 GCD diagram of the assembled supercapacitor (a) and schematic diagram of the device lighting up LEDs (b). Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to the embodiments. The test materials used in the embodiments can all be purchased through conventional means.

[0028] Example 1

[0029] The preparation method of the three-dimensional multilayer LDH / CS / PPy composite material of the present invention includes the following steps:

[0030] (1) Preparation of CS: 0.42 g citric acid and 0.36 g urea were dispersed in 30 mL of water and stirred for 2 hours. The mixed solution was transferred to a reactor and reacted at 180 °C for 5 hours. The resulting solution was dialyzed in deionized water for 3 days. The liquid in the dialysis bag was then centrifuged at 12,000 rpm for 20 minutes to obtain the supernatant and dried.

[0031] (2) Preparation of NiCoAl-LDH: 1 mmol of Ni(NO3)2‧6H2O, 3 mmol of Co(NO3)2‧6H2O, 1.5 mmol of Al(NO3)3‧9H2O, and 16 mmol of NH4F were dispersed in 30 mL of water and stirred for 10 minutes to form solution A. 19.2 mmol of urea was dispersed in 30 mL of water and stirred for 10 minutes to form solution B. Solution B was mixed with solution A and stirred for 10 minutes. The mixed solution was transferred to an 80 mL reactor and reacted at 120 °C for 5 hours.

[0032] (3) Preparation of LDH / CS: 1 mmol of Ni(NO3)2‧6H2O, 3 mmol of Co(NO3)2‧6H2O, 1.5 mmol of Al(NO3)3‧9H2O, 16 mmol of NH4F, and 1 mg / mL of CS were dispersed in 30 mL of water and stirred for 10 minutes to form solution A. 19.2 mmol of urea was dispersed in 30 mL of water and stirred for 10 minutes to form solution B. Solution B was mixed with solution A and stirred for 10 minutes. The mixed solution was reacted at 120°C in an 80 mL reactor for 5 hours.

[0033] (4) Preparation of LDH / CS / PPy: Dissolve 0.5 g LDH / CS in 100 mL of water and stir for 30 minutes. Add 0.075 mL of pyridine and 0.125 g of hexadecyltrimethylammonium bromide (CTAB) to the above solution and stir for 30 minutes. Dissolve 0.435 g of ammonium persulfate in 4.28 mL of 5 mol / L hydrochloric acid solution and slowly add it to the above solution. Stir the mixed solution for 12 hours. After washing with water and centrifuging, the three-dimensional multilayer LDH / CS / PPy composite material of the present invention is obtained, denoted as LDH / CS / PPy.

[0034] The structural properties of the obtained nanomaterials were characterized by X-ray diffraction (XRD), and the results are as follows: Figure 1 As shown. The diffraction peak of CS at a diffraction angle of 25.1° corresponds to the (002) peak of amorphous carbon. The XRD pattern of LDH shows a series of diffraction peaks corresponding to the (003), (006), (012), (018), (110), and (113) crystal planes (JCPDS No. 15-0087). The diffraction peaks of LDH / CS correspond to the diffraction peaks of LDH and the diffraction peak of CS at a diffraction angle of 25.1°. The diffraction peaks of LDH / CS / PPy are basically the same as those of LDH / CS, which is due to the amorphous nature of polypyrrole (PPy), proving the successful synthesis of the material.

[0035] Figure 2 SEM images of the prepared samples; Figure 2 In the image, a is the SEM image of CS, b is the SEM image of LDH, c is the SEM image of LDH / CS, and d is the SEM image of LDH / CS / PPy; for example... Figure 2 As shown in Figure a, CS is a smooth sphere with a diameter of 318 nanometers. Figure 2 As shown in Figure b, LDH is a regular thin sheet with a thickness of 5-6 nanometers. Figure 2 In the CS layer, after loading LDH, a uniformly arranged nanosheet layer grows on the surface, which effectively prevents LDH stacking. The diameter of LDH / CS is 395 nm. Polypyrrole (PPy) has strong conductivity, which effectively solves the problem of low conductivity of LDH. After loading PPy, as... Figure 2 As shown in Figure d, the morphology of LDH / CS / PPy transforms into a core-shell structure with irregularly shaped flakes on the surface. The diameter of LDH / CS is 450 nanometers.

[0036] Example 2

[0037] The three-dimensional multilayer LDH / CS / PPy composite material of the present invention, compared with Example 1, has the CS concentration changed to 2 mg / mL. -1 It is denoted as LDH / CS-2 / PPy.

[0038] Example 3

[0039] The three-dimensional multilayer LDH / CS / PPy composite material of the present invention, compared with Example 1, has the CS concentration changed to 3 mg / mL. -1 It is denoted as LDH / CS-3 / PPy.

[0040] Example 4

[0041] The three-dimensional multilayer LDH / CS / PPy composite material of the present invention, compared with Example 1, has the CS concentration changed to 4 mg / mL. -1 It is denoted as LDH / CS-4 / PPy.

[0042] Example 5

[0043] The three-dimensional multilayer LDH / CS / PPy composite material of the present invention, compared with Example 1, has the CS concentration changed to 5 mg / mL. -1 It is denoted as LDH / CS-5 / PPy.

[0044] Comparative Example 1

[0045] LDH / CS-x with different CS addition amounts were prepared. Compared with Example 1, steps 1-3 were performed, and the concentration of CS in step 3 was adjusted to 1 mg / mL. -1 2 mg mL -1 3 mg mL -1 4 mg mL -1 and 5mg mL -1 The corresponding products are denoted as LDH / CS-1, LDH / CS-2, LDH / CS-3, LDH / CS-4, and LDH / CS-5.

[0046] like Figure 3 The figure shows the CV curves of the materials prepared in the examples and comparative examples. It can be seen that the concentration of CS is 3 mg / mL. -1 The time-discharge performance is the best. Furthermore, the GCD curve shows that LDHs / CS-3 has the longest discharge time, and capacitance calculations reveal that LDHs / CS-3 exhibits the best performance at a current density of 1 A g. -1 The specific capacitance is 1782 F g -1 The capacitor of LDH / CS-5 is 751 F g. -1 Furthermore, LDH at a current density of 1 A g -1 The specific capacitance is 528 F g -1 The results showed that the electrochemical performance of the electrode material was improved after the introduction of CS due to the improvement of LDH stacking.

[0047] LDH / CS / PPy-x with different PPy addition amounts were prepared. Compared with Example 3, steps 1 to 4 were performed. The volume of pyridine in step 4 was adjusted to 0.1 mL, 0.125 mL, 0.15 mL and 0.175 mL, respectively. The corresponding products were denoted as LDH / CS / PPy-2, LDH / CS / PPy-3, LDH / CS / PPy-4 and LDH / CS / PPy-5.

[0048] Different LDH / CS / PPy-x electrodes were tested using CV and GCD methods. The results showed that the LDH / CS / PPy-3 electrode exhibited the optimal specific capacitance of 2212 F g when the pyridine volume was 0.125 mL. -1 And compared to the capacitance of LDHs / CS (1782 F g) -1 The performance of LDH / CS / PPy was significantly improved after the introduction of PPy to form a conductive network. To verify this, electrochemical impedance spectroscopy was performed on the LDH, LDH / PPy, LDH / CS, and LDH / CS / PPy electrodes. Figure 4 As shown, the charge transfer resistance of LDH / CS / PPy is 2.57 Ω, which is significantly better than that of LDH (3.38 Ω), LDH / CS (4.28 Ω) and LDH / PPy (6.54 Ω), indicating that it has excellent conductivity.

[0049] Verify the application of the three-dimensional multilayer LDH / CS / PPy composite material of this invention as an electrode material in the field of energy material preparation technology:

[0050] Electrochemical performance was evaluated using a CHI660e electrochemical workstation (purchased from Shanghai Chenhua Instrument Co., Ltd.). In a three-electrode system, an LDH / CS / PPy composite material was used as the working electrode, an Hg / HgO electrode as the reference electrode, and a platinum sheet as the counter electrode. The capacitance performance of the electrode materials was evaluated within a voltage range of 0-0.5 V. The capacitance formula of the electrode materials was then used: C s The specific capacitance is calculated using It / mΔt. An asymmetric supercapacitor is assembled using LDH / CS / PPy as the positive electrode, filter paper soaked in 3 M KOH electrolyte as the diaphragm, and AC as the negative electrode. The performance of the device is evaluated in a two-electrode system.

[0051] Figure 5 The figure shows the GCD curve of the assembled device. As can be seen from the figure, the assembled supercapacitor operates at a current density of 1 A g. -1 In this case, the specific capacitance of the device is 357 F g. -1Furthermore, it was able to successfully light up multiple LEDs, demonstrating the practical application performance of the LDH / CS / PPy electrode material.

Claims

1. A three-dimensional multilayer LDH / CS / PPy composite material, characterized in that, The composite material has a multi-layer core-shell structure. Carbon spheres CS with functional groups on the surface serve as the structural guiding core, inducing the in-situ growth of nickel cobalt aluminum layered bimetallic hydroxide NiCoAl-LDH on its surface to form a uniformly dispersed flower-like structure. A polypyrrole PPy conductive layer is coated on the surface of the composite material by in-situ polymerization to construct a three-dimensional conductive network.

2. A method for preparing the three-dimensional multilayer LDH / CS / PPy composite material according to claim 1, characterized in that, Includes the following steps: (1) Citric acid and urea are dissolved in deionized water and stirred to form a homogeneous solution. A hydrothermal reaction is carried out. After the reaction is completed, the product is purified by dialysis. After centrifugation and drying, nano-carbon spheres with functional groups on the surface are obtained. (2) Nickel salt, cobalt salt, aluminum salt and ammonium fluoride are mixed and dissolved to form a metal salt solution; Urea was dissolved to prepare a precipitant solution; the two solutions were mixed and subjected to a hydrothermal reaction. The reaction product was washed and dried to obtain nickel-cobalt-aluminum layered bimetallic hydroxide NiCoAl-LDH. (3) Add the carbon ball material produced in step (1) to the metal salt solution of the product NiCoAl-LDH in step (2), and after being fully dispersed, mix with urea solution. Through hydrothermal reaction, the layered bimetallic hydroxide grows in situ on the surface of the carbon ball to obtain an LDH / CS composite material in which the carbon ball and the layered bimetallic hydroxide are tightly bonded. (4) The composite material obtained in step (3) is uniformly dispersed in an aqueous solution, pyrrole monomer and surfactant are added, and after sufficient dispersion, an initiator solution prepared by oxidant and hydrochloric acid is added to carry out in-situ chemical oxidation polymerization reaction. After the reaction is completed, the product is washed and dried to obtain the three-dimensional multilayer LDH / CS / PPy composite material.

3. The preparation method according to claim 2, characterized in that, In step (1), the mass ratio of citric acid to urea is 7:5~7, the reaction vessel is heated at 160-180℃ for 4-5 hours, and the supernatant is taken and dried during the dialysis process.

4. The preparation method according to claim 2, characterized in that, In step (2), the molar ratio of nickel salt, cobalt salt, aluminum salt, ammonium fluoride and urea is 1~2:2~3:1.5:16:19.

2.

5. The preparation method according to claim 2, characterized in that, In step (2), the urea solution is quickly poured into the metal salt solution, and the hydrothermal reaction is carried out at 110-120℃ for 5-6 hours.

6. The preparation method according to claim 2, characterized in that, In step (3), the mass-volume ratio of carbon sphere material, NiCoAl-LDH, and urea solution is 1~5:16.3:38.

4.

7. The preparation method according to claim 2, characterized in that, In step (3), the concentration of CS is 1~5 mg / mL. -1 The hydrothermal reaction is carried out at 110-120℃ for 5-6 hours.

8. The preparation method according to claim 2, characterized in that, In step (4), the mass-volume ratio of LDH / CS composite material, pyrrole monomer, oxidant and hydrochloric acid is 1:0.15~3.5:0.9:8.5; the surfactant is hexadecyltrimethylammonium bromide and the oxidant is ammonium persulfate.

9. The application of the three-dimensional multilayer LDH / CS / PPy composite material as described in claim 1 as an electrode material in the field of energy material preparation technology.

10. The application according to claim 9, characterized in that, The prepared LDH / CS / PPy composite electrode material is used as the anode material of a high-performance supercapacitor. An asymmetric supercapacitor is assembled with LDH / CS / PPy as the positive electrode and AC as the negative electrode.

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