Nitrogen-doped neodymium sulfide and manganese sulfide / foamy copper composite electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of electrochemical materials, and particularly discloses a nitrogen-doped neodymium sulfide and manganese sulfide / foamy copper composite electrode material and a preparation method and application thereof. The nitrogen-doped neodymium sulfide and manganese sulfide composite material is coated on the foamy copper substrate in situ by adopting a one-step hydrothermal method, the electrochemical performance of the material is remarkably improved, the specific capacitance of a supercapacitor prepared by taking the nitrogen-doped neodymium sulfide and manganese sulfide composite material as a positive electrode material under the current density of 16A / g can reach 1122.7 F / g, the capacity retention rate after 50,000 cycles is 37.3%, and the capacity retention rate is 37.3%. The composite electrode material with excellent comprehensive performance is provided for a supercapacitor electrode, and the performance of a supercapacitor is expected to be remarkably improved, so that further development and wide application of the supercapacitor in the field of energy storage are promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical materials, and particularly relates to a nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material, a preparation method thereof, and an application thereof. Background Art

[0002] A supercapacitor, also known as an electrochemical capacitor, is a new type of energy storage element between traditional electrostatic capacitors and chemical power sources. Supercapacitors have many remarkable advantages, such as a large power density, enabling fast charging with a large current (0.3 - 30 s), rapid charge and discharge; a long cycle life, up to 100,000 times; and a wide operating temperature range (-40°C to +70°C). These characteristics make it show broad application prospects in many fields. The performance of the electrode material directly determines the overall performance of the supercapacitor. An ideal electrode material should have a large specific surface area to provide more charge storage sites; have high chemical stability and good cycling performance to ensure long-term use; have good wettability in the electrolyte, and at the same time have a small contact resistance with the electrolyte and the current collector, thereby reducing the electrochemical impedance.

[0003] Manganese sulfide (MnS) has a low cost, rich manganese reserves, and a high theoretical specific capacitance, and is a very promising electrode material. However, in practical applications, manganese sulfide still has some defects: due to the easy aggregation or accumulation of its nanoparticles, the available active specific surface area is greatly reduced, resulting in a decrease in the specific capacitance. At the same time, the conductivity of manganese sulfide is poor, and a volume expansion effect occurs during long-term charge and discharge processes, which easily causes the electrode material to powder, seriously affecting its cycling ability and rate performance. Therefore, it is necessary to develop a new type of manganese sulfide composite electrode material to solve the above problems existing in the existing supercapacitor electrode materials, improve the comprehensive performance of the supercapacitor, and meet the growing energy storage and application requirements. Summary of the Invention

[0004] Aiming at the problems that the existing manganese sulfide as an electrode material has poor conductivity, low specific capacitance, poor cycling performance and rate performance, which seriously limit its application in supercapacitors, the present invention provides a nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material, a preparation method thereof, and an application thereof.

[0005] To solve the above technical problems, the technical solution provided by the present invention is:

[0006] A nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material, comprising a copper foam matrix, and an N-doped neodymium sulfide and manganese sulfide composite material coated on the outside of the copper foam matrix.

[0007] Compared with the prior art, the composite electrode material provided by the present invention forms a core-shell structure by coating a composite of N-doped neodymium sulfide and manganese sulfide on a copper foam substrate; among them, the combination of nitrogen-doped neodymium sulfide and manganese sulfide constructs a unique electronic structure and active sites, and the defects and heteroatoms introduced by nitrogen doping significantly improve the conductivity and electrochemical activity of the material; the combination of neodymium sulfide and manganese sulfide improves the redox reaction kinetics through synergistic effects. In battery or supercapacitor applications, the charge-discharge efficiency and specific capacity can be greatly improved to meet the high-energy density energy storage requirements. At the same time, the composite electrode material presents a hierarchical pore structure, and the macropores of the copper foam, the mesopores of the sulfide and the micropores formed by nitrogen doping communicate with each other, greatly shortening the ion transport distance, accelerating the insertion and extraction of ions in the electrolyte, and significantly improving the performance of the electrode under high-rate charge-discharge conditions to meet the requirements of fast charge-discharge scenarios. In addition, a stable composite interface is formed between the nitrogen-doped neodymium sulfide and manganese sulfide on the copper foam matrix, which can significantly reduce the corrosion and oxidation of the electrolyte to the copper foam substrate, so that the electrode material can still maintain good chemical stability and structural integrity in different acid-base environments and high-temperature conditions, broadening the application range of the material.

[0008] The present invention also provides a preparation method of a nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material, comprising the following steps:

[0009] S1, adding a soluble neodymium salt, a soluble manganese salt and thiourea into a mixed solution of ethylene glycol and water to obtain a precursor solution;

[0010] S2, placing the precursor solution and the copper foam substrate in a hydrothermal reactor, reacting at 130°C to 180°C, washing and drying to obtain a nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material.

[0011] The present invention in-situ coats a composite of N-doped neodymium sulfide and manganese sulfide on a copper foam substrate by a hydrothermal method. The hydrothermal reaction is beneficial to precisely control the formation of the microstructure of the product to form a hierarchical pore structure. These hierarchical pore structures increase the specific surface area of the material and provide more active sites for ion transport and storage, thereby improving the electrochemical performance of the electrode material. At the same time, in-situ preparation enables nitrogen-doped neodymium sulfide and manganese sulfide to be uniformly and tightly coated on the surface of the copper foam substrate, which not only enhances the binding force between the active substance and the substrate, reduces the shedding of the active substance during charge and discharge, but also enables electrons to be efficiently transported between the substrate and the active substance, further improving the conductivity and stability of the electrode material.

[0012] The preparation method of the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material provided by the present invention has wide sources of raw materials and low prices, does not require complex equipment and cumbersome process steps, is easy to realize large-scale production, meets the dual requirements of industrial production for cost and output, and has high practical value.

[0013] Specifically, before the hydrothermal reaction, the copper foam substrate needs to be pretreated to remove impurities on the surface of the copper foam.

[0014] Furthermore, after cutting the copper foam into small pieces, the copper foam is ultrasonically treated in acetone and hydrochloric acid solution for 5 min to 10 min respectively, and then ultrasonically treated in deionized water for 10 min to 20 min to obtain a clean copper foam substrate.

[0015] As a specific embodiment of the present invention, the concentration of the above hydrochloric acid solution is 2.5M to 3.5M. The copper foam can be cut into a size of 5 cm * 1 cm * 1.5 mm.

[0016] Furthermore, the soluble neodymium salt is neodymium chloride, neodymium sulfate or neodymium nitrate.

[0017] Furthermore, the soluble manganese salt is manganese chloride, manganese sulfate or manganese nitrate.

[0018] It should be noted that the soluble neodymium salt and the soluble manganese salt are salts with the same anion. For example, if the soluble neodymium salt is neodymium chloride, the soluble manganese salt is preferably manganese chloride.

[0019] Furthermore, in the precursor solution, the concentration of the soluble neodymium salt is 0.6 mmol / L to 1.8 mmol / L, the concentration of the soluble manganese salt is 1.0 mmol / L to 2.1 mmol / L, and the concentration of thiourea is 2.8 mmol / L to 3.8 mmol / L.

[0020] Preferably, the volume ratio of ethylene glycol to water is 1:1.5 to 1:2.5.

[0021] Furthermore, in S2, the reaction time is 4 h to 8 h.

[0022] The preferred reaction concentration, temperature and time are beneficial to the formation of a complete crystal structure and an ideal microscopic morphology. At the same time, they are also beneficial to the formation of a good interfacial bond between the copper foam matrix and nitrogen-doped neodymium sulfide and manganese sulfide, forming a uniform coating layer, thereby improving the energy storage performance and chemical stability of the composite electrode material.

[0023] The present invention also provides a nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material, which is prepared by the preparation method of the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material described in any one of the above.

[0024] In the nitrogen-doped neodymium sulfide@manganese sulfide / carbon foam composite electrode material prepared by the above method, the co-doping of N atoms can increase the interlayer spacing of the neodymium sulfide and manganese sulfide active materials, increase the active sites for redox reactions, accelerate the migration of ions during the electrochemical reaction process, and thus improve the diffusion rate of reaction ions. Through the synergistic effect of the neodymium sulfide and manganese sulfide bimetallic materials, not only can the volume change of the active material during the electrochemical reaction process be inhibited, the cycle stability of the material be improved, but also the electronic energy band structure of the material can be adjusted, the charge transfer resistance can be reduced, and thus the electron transport during the reaction process can be promoted. In addition, the heterojunction at the interface of the bimetallic sulfide enables a stable SEI film to be formed at the interface of the bimetallic sulfide, reducing side reactions and the loss of active substances. Moreover, when the bimetallic sulfides are phase-combined, a three-dimensional conductive framework can be formed, reducing the internal resistance at the bimetallic interface, and thus accelerating the ion diffusion rate. In addition, the metal sulfide composite structure can enhance the mechanical strength of the material and the stability of the material through interfacial bonding.

[0025] The core-shell structure formed by coating can make full use of the good conductivity structure of carbon foam to provide a good electron transport channel for the nitrogen-doped neodymium sulfide@manganese sulfide active material; the presence of the three-dimensional network carbon foam can further slow down the volume expansion of the nitrogen-doped neodymium sulfide@manganese sulfide composite material during charge and discharge processes, which is beneficial to the further improvement of the energy storage performance of the electrode material and the enhancement of the cycle stability performance of the electrode material.

[0026] The present invention also provides a positive electrode, comprising the above-mentioned nitrogen-doped neodymium sulfide@manganese sulfide / carbon foam composite electrode material.

[0027] The present invention also provides a supercapacitor, comprising the above-mentioned positive electrode.

[0028] The nitrogen-doped neodymium sulfide@manganese sulfide / carbon foam composite electrode material prepared by the present invention has a high specific capacitance and cycle stability. Applying the above composite electrode material to a supercapacitor can obtain a supercapacitor with stable cycle performance and excellent specific capacitance. The specific capacitance can reach 1122.7 F / g at a current density of 16 A / g, and the capacity retention rate after 50,000 cycles can reach 37.3%, having high practical value and application and popularization value. Description of the Drawings

[0029] Figure 1 It is the XRD pattern of the nitrogen-doped neodymium sulfide@manganese sulfide / carbon foam composite electrode material prepared in Example 1 of the present invention;

[0030] Figure 2SEM images of the composite electrode materials prepared in Example 1 and Comparative Example 1 of the present invention at different magnifications; among them, (a)-(d) are N-Nd2S3 / FC prepared in Comparative Example 1, and (e)-(f) are N-Nd2S3@MnS / FC prepared in Example 1;

[0031] Figure 3 Cyclic voltammograms of the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode materials prepared in Examples 1-3 at a scan rate of 50 mV / s;

[0032] Figure 4 Galvanostatic charge-discharge curves of the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material prepared in Example 1 at different mass current densities;

[0033] Figure 5 Cyclic voltammograms of the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material prepared in Example 1 at different scan rates;

[0034] Figure 6 Cyclic retention rate diagram of the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material prepared in Example 1 at a current density of 30 A / g;

[0035] Figure 7 Four-probe test resistance diagram of the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material prepared in Example 1;

[0036] Figure 8 Cyclic voltammograms of the aqueous supercapacitor assembled with the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material prepared in Example 1 as the positive electrode at different scanning rates;

[0037] Figure 9 Galvanostatic charge-discharge curves of the aqueous supercapacitor assembled with the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material prepared in Example 1 as the positive electrode at different mass current densities;

[0038] Figure 10 Electrochemical impedance diagram of the aqueous supercapacitor assembled with the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material prepared in Example 1 as the positive electrode tested at a potential range of 10 mHz - 0.1 MHz and a perturbation voltage of 5 mV; the inset is the equivalent circuit diagram after fitting;

[0039] Figure 11 Ragone diagram of the aqueous supercapacitor assembled with the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material prepared in Example 1 as the positive electrode;

[0040] Figure 12The stability curve of an aqueous supercapacitor assembled with the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material prepared in Example 1 as the positive electrode. Detailed implementation manners

[0041] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] To better illustrate the present invention, further illustrative examples are given below through embodiments.

[0043] Example 1

[0044] A preparation method of a nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material:

[0045] Step 1: Cut commercial copper foam into rectangular strips of 1 cm×5 cm×1.5 mm, add them to acetone and 3 mol / L dilute hydrochloric acid solution respectively, ultrasonically treat for 8 min, then ultrasonically treat with deionized water for 15 min, and dry to obtain a copper foam matrix.

[0046] Step 2: Add neodymium chloride, manganese chloride and thiourea to a mixed solution of ethylene glycol and water with a volume ratio of 1:2 to obtain a precursor solution; the concentration of neodymium chloride in the precursor solution is 1.2 mmol / L, the concentration of manganese chloride is 1.8 mmol / L, and the concentration of thiourea is 3.2 mmol / L.

[0047] Step 3: Add the copper foam matrix and the above precursor solution to a high-pressure hydrothermal autoclave, react at 150 °C for 6 h. After the reaction is completed, take out the copper foam, thoroughly wash it with pure water, and dry it in an oven at 60 °C to obtain a nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material, denoted as N-Nd2S3@MnS / FC.

[0048] Example 2

[0049] A preparation method of a nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material:

[0050] Step 1: Cut commercial copper foam into rectangular strips of 1 cm×5 cm×1.5 mm, add them to acetone and 2.5 mol / L dilute hydrochloric acid solution respectively, ultrasonically treat for 5 min, then ultrasonically treat with deionized water for 20 min, and dry to obtain a copper foam matrix.

[0051] Step 2: Add neodymium chloride, manganese chloride and thiourea into a mixed solution of ethylene glycol and water with a volume ratio of 1:2 to obtain a precursor solution; the concentration of neodymium chloride in the precursor solution is 0.6 mmol / L, the concentration of manganese chloride is 1.8 mmol / L, and the concentration of thiourea is 3.2 mmol / L;

[0052] Step 3: Add the copper foam substrate and the above precursor solution into a high-pressure hydrothermal reactor, react at 130 °C for 8 h. After the reaction is completed, take out the copper foam, wash it thoroughly with pure water, and dry it in an oven at 60 °C to obtain a nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material, denoted as N-Nd2S3@MnS / FC.

[0053] Example 3

[0054] A preparation method of a nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material:

[0055] Step 1: Cut commercial copper foam into rectangular strips of 1 cm × 5 cm × 1.5 mm, add them into acetone and 3.5 mol / L dilute hydrochloric acid solution respectively, ultrasonically treat for 10 min, then ultrasonically treat with deionized water for 10 min, and dry to obtain a copper foam substrate;

[0056] Step 2: Add neodymium chloride, manganese chloride and thiourea into a mixed solution of ethylene glycol and water with a volume ratio of 1:2 to obtain a precursor solution; the concentration of neodymium chloride in the precursor solution is 1.8 mmol / L, the concentration of manganese chloride is 1.8 mmol / L, and the concentration of thiourea is 3.2 mmol / L;

[0057] Step 3: Add the copper foam substrate and the above precursor solution into a high-pressure hydrothermal reactor, react at 180 °C for 4 h. After the reaction is completed, take out the copper foam, wash it thoroughly with pure water, and dry it in an oven at 60 °C to obtain a nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material, denoted as N-Nd2S3@MnS / FC.

[0058] Comparative Example 1

[0059] This comparative example provides a preparation method of a nitrogen-doped manganese sulfide / copper foam composite electrode material:

[0060] Step 1: Cut commercial copper foam into rectangular strips of 1 cm × 5 cm × 1.5 mm, add them into acetone and ultrasonically treat for 20 min, then ultrasonically treat with 3 mol / L hydrochloric acid solution and deionized water for 15 min respectively, and dry to obtain a copper foam substrate;

[0061] Step 2: Add manganese chloride and thiourea into a mixed solution of ethylene glycol and water with a volume ratio of 1:2 to obtain a precursor solution; the concentration of manganese chloride in the precursor solution is 1.8 mmol / L, and the concentration of thiourea is 3.2 mmol / L;

[0062] Step 3: Add the copper foam substrate and the above precursor solution into a high-pressure hydrothermal reactor, react at 140 °C for 4 h. After the reaction is completed, take out the copper foam, wash it thoroughly with pure water, and dry it in an oven at 60 °C to obtain a nitrogen-doped manganese sulfide / copper foam composite electrode material, denoted as N-MnS / FC.

[0063] Figure 1 XRD pattern of N-Nd2S3@MnS / FC prepared in Example 1. As can be seen from the figure, the diffraction peaks at 43.3°, 50.4° and 74.1° belong to the (1 1 1), (2 0 0) and (2 2 0) crystal planes of Cu (PDF#04-0836), respectively. The diffraction peaks at 24.6°, 25.9°, 28.0°, 32.7°, 33.3°, 34.7°, 36.5°, 38.5°, 40.4°, 44.9°, 46.4°, 48.4°, 52.6°, 56.1°, 61.9°, 66.9°, 69.6°, 71.5°, 73.1° and 76.2° belong to the (2 1 0), (1 4 0), (0 3 1), (2 0 1), (24 0), (2 2 1), (0 5 1), (1 5 1), (2 4 1), (0 02), (3 3 1), (1 7 1), (1 4 2), (3 6 1), (3 3 21), (0 8 2), (2 10 1), (1 1 3), (0 12 0) and (2 2 3) crystal planes of Nd2S3 (PDF#45-0984), respectively. It is proved that the prepared electrode material is N-Nd2S3@MnS / FC composite electrode material.

[0064] Figure 2 SEM images of N-Nd2S3@MnS / FC prepared in Example 1 and N-MnS / FC prepared in Comparative Example 1 at different magnifications. Among them, (a)–(d) are SEM images of N-MnS / FC prepared in Comparative Example 1, and (e)–(f) are SEM images of N-Nd2S3@MnS / FC prepared in Example 1. By comparing (a)–(d) and (e)–(f), it can be seen that the microtopographies of the N-MnS / FC electrode material prepared in Comparative Example 1 and the N-Nd2S3@MnS / FC electrode material prepared in Example 1 are different. The structure of the N-Nd2S3@MnS / FC electrode material of the material in Example 1 is a coated core-shell structure.

[0065] Figure 3The cyclic voltammograms of the N-Nd2S3@MnS / FC composite electrode materials prepared in Example 1, Example 2, and Example 3 were obtained in a three-electrode system (the electrode to be tested as the positive electrode, the saturated calomel electrode as the reference electrode, and the platinum sheet as the negative electrode) in a 1M KOH electrolyte at a scan rate of 50 mV / s within the potential range of 0 to 0.6V. From the shape of the cyclic voltammogram similar to a rectangle, it can be seen that the N-Nd2S3@MnS / FC composite electrode materials prepared in Example 1, Example 2, and Example 3 have good capacitive performance. From the area enclosed by the cyclic voltammogram, it can be seen that: Example 1 > Example 2 > Example 3. Therefore, the specific capacitances of the three electrodes are arranged in descending order as follows: Example 1 > Example 2 > Example 3.

[0066] Figure 4 The galvanostatic charge-discharge curves of the N-Nd2S3@MnS / FC composite electrode material prepared in Example 1 were obtained in a three-electrode system (the electrode to be tested as the positive electrode, the saturated calomel electrode as the reference electrode, and the platinum sheet as the negative electrode) in a 1M KOH electrolyte at different current densities within the potential range of 0 to 0.6V. According to Figure 4 it can be calculated that the specific capacitances of the prepared electrode materials at current densities of 16 A / g, 17 A / g, 18 A / g, 19 A / g, 20 A / g, and 30 A / g are 1122.7 F / g, 1096.5 F / g, 1026.0 F / g, 1003.8 F / g, 986.7 F / g, and 830.0 F / g, respectively.

[0067] Figure 5 The cyclic voltammograms of the N-Nd2S3@MnS / FC composite electrode material prepared in Example 1 were obtained in a three-electrode system (the electrode to be tested as the positive electrode, the saturated calomel electrode as the reference electrode, and the platinum sheet as the negative electrode) in a 1M KOH electrolyte at different scan rates within the potential range of 0 to 0.6V. The area enclosed by the cyclic voltammogram at low scan rates is close to a rectangle, indicating good capacitive performance. As the scan rate increases, the shape of the curve deviates from a rectangle.

[0068] Figure 6Cyclic retention rate graph of the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material prepared in Example 1. Using the prepared nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material as the positive electrode, a saturated calomel electrode as the reference electrode, and a platinum sheet as the negative electrode, with 1M KOH solution as the electrolyte, the cyclic stability of the prepared electrode was tested at a voltage of 0 - 0.6V. The capacity retention rate of the prepared electrode can reach 102.0% after 5000 cycles; 87.2% after 10000 cycles; 96.2% after 15000 cycles; 86.4% after 20000 cycles; 76.1% after 25000 cycles; 67.0% after 30000 cycles; 55.7% after 35000 cycles; 48.5% after 40000 cycles; 43.1% after 45000 cycles; and the capacity retention rate after 50000 cycles is 37.3%, indicating that the core-shell structured nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material has good cyclic performance.

[0069] Figure 7 Four-probe test resistance graph of the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material prepared in Example 1. As can be seen from the figure, the resistance of the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material prepared in Example 1 is 0.94 mΩ.

[0070] Figure 8 An aqueous supercapacitor assembled with the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material prepared in Example 1 as the positive electrode and an N-doped NaCu2S2 material (the preparation method can be found in F. Tian et al. Journal of Energy Storage 115(2025)115960) as the negative electrode. Cyclic voltammetry (CV) curves of this aqueous supercapacitor at different scan rates in a 1M KOH electrolyte within a potential range of 0 - 1.8V. The specific capacitance of this aqueous supercapacitor at different current densities can be calculated based on the cyclic voltammetry curves. The calculation formula is as follows:

[0071]

[0072] In the formula, ∫idV represents the area enclosed by the cyclic voltammetry curve; v represents the scan rate, V / s; and ΔV represents the tested potential window, V.

[0073] The specific capacitances calculated at scanning speeds of 5 mV / s, 10 mV / s, 20 mV / s, 50 mV / s, 100 mV / s, 200 mV / s, and 500 mV / s are 136.0 F / g, 92.8 F / g, 78.3 F / g, 53.7 F / g, 35.1 F / g, 20.6 F / g, and 8.0 F / g, respectively.

[0074] Figure 9 The constant current charge-discharge curves of the assembled aqueous supercapacitor with the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material prepared in Example 1 as the positive electrode and the N-doped NaCu2S2 material (for the preparation method, see F. Tian et al. Journal of Energy Storage 115 (2025) 115960) as the negative electrode at different mass current densities; the specific capacitance C at different mass current densities is calculated according to the constant current charge-discharge curves. The calculation formula is as follows:

[0075] C = i m t / ΔV

[0076] where C represents the specific capacitance, with the unit of F·g -1 ; i m represents the current density, with the unit of A·g -1 ; t represents the discharge time, with the unit of s; ΔV represents the potential difference, with the unit of V.

[0077] At 2 A / g, 3 A / g, 4 A / g, and 5 A / g, the specific capacitance values of the device are 347.3 F / g, 191.5 F / g, 149.8 F / g, and 121.4 F / g, respectively.

[0078] Figure 10 The electrochemical impedance diagram of the assembled aqueous supercapacitor with the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material prepared in Example 1 as the positive electrode and the N-doped NaCu2S2 material (for the preparation method, see F. Tian et al. Journal of Energy Storage 115 (2025) 115960) as the negative electrode tested at a potential range of 10 mHz to 0.1 MHz with a 5 mV perturbation voltage. The inset is the equivalent circuit diagram after fitting. By using Z-view software to fit the total resistance of the electrolyte, charge transfer resistance, constant phase element (CPE-T, CPE-P), and Warburg (W R 、W T and W P) The resistance values are 5.68 Ω, 10.00 Ω, 0 Ω, 0.68 Ω, 111 Ω, 18.09 Ω, and 0.65 Ω respectively. The total resistance of the electrolyte of the assembled aqueous supercapacitor is relatively low. The small charge transfer resistance indicates that ions can achieve rapid charge transport during the electrochemical reaction, demonstrating that the supercapacitor device has good reaction kinetics.

[0079] Figure 11 Figure of Ragone for the aqueous supercapacitor assembled with the nitrogen-doped neodymium sulfide@manganese sulfide / carbon foam composite electrode material prepared in Example 1 as the positive electrode and the N-doped NaCu2S2 material (for the preparation method, see F. Tian et al. Journal of Energy Storage 115 (2025) 115960) as the negative electrode. From the figure, it can be calculated that the energy density of the device at a power density of 1800 W / kg is 156.3 Wh / kg.

[0080] The formula for calculating the energy density is as follows:

[0081]

[0082] Among them, E represents the energy density, with the unit of Ws / kg; C represents the specific capacitance, with the unit of F / kg; ΔV represents the potential difference, with the unit of V.

[0083] The formula for calculating the high power density is as follows:

[0084]

[0085] Among them, P represents the power density, with the unit of W / kg; E represents the energy density, with the unit of Ws / kg; Δt represents the time, with the unit of s.

[0086] Figure 12The cycling retention rate diagram of an aqueous supercapacitor assembled with the nitrogen-doped neodymium sulfide@manganese sulfide / carbon foam composite electrode material prepared in Example 1 as the positive electrode and the N-doped NaCu2S2 material (for the preparation method, see F. Tian et al. Journal of Energy Storage 115 (2025) 115960) as the negative electrode at a current density of 10 A / g. Using the prepared nitrogen-doped neodymium sulfide@manganese sulfide / carbon foam composite electrode material as the positive electrode and 1 M KOH solution as the electrolyte, the cycling stability of the prepared electrode was tested at a voltage of 0 - 0.6 V. The capacity retention rate of the prepared electrode reached 23.5% after 5000 cycles; 23.7% after 10000 cycles; 22.2% after 15000 cycles; 22.2% after 20000 cycles; 22.2% after 25000 cycles; and 23.7% after 30000 cycles, indicating that the core-shell structured nitrogen-doped neodymium sulfide@manganese sulfide / carbon foam composite electrode material has good cycling performance.

[0087] In summary, the present invention uses a one-step hydrothermal method to in-situ prepare a nitrogen-doped neodymium sulfide@manganese sulfide / carbon foam composite electrode material on a carbon foam substrate. Due to the nitrogen doping in neodymium sulfide and manganese sulfide and the good conductive network of carbon foam, the composite electrode material synergistically exhibits high electrochemical performance. Using it as the positive electrode material and the N-doped NaCu2S2 material (for the preparation method, see F. Tian et al. Journal of Energy Storage 115 (2025) 115960) as the negative electrode, the specific capacitance of the prepared aqueous asymmetric supercapacitor is 347.3 F / g (625.1 C / g) at a current density of 2.0 A / g, and the energy density is 156.3 Wh / kg at a power density of 1800 W / kg. This method provides a basis for optimizing the electrochemical performance of supercapacitor energy storage devices and improving their overall performance.

[0088] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, or improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A nitrogen-doped neodymium sulfide @ manganese sulfide / carbon foam composite electrode material, characterized in that, It includes a copper foam matrix, and an N-doped neodymium sulfide and manganese sulfide composite material coated on the outside of the copper foam matrix.

2. The preparation method of the nitrogen-doped neodymium sulfide @ manganese sulfide / carbon foam composite electrode material according to claim 1, characterized in that, It includes the following steps: S1. Add soluble neodymium salt, soluble manganese salt and thiourea into a mixed solution of ethylene glycol and water to obtain a precursor solution. S2. Place the precursor solution and the copper foam matrix in a hydrothermal autoclave, react at 130°C to 180°C, wash and dry to obtain a nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material.

3. The preparation method of the nitrogen-doped neodymium sulfide @ manganese sulfide / copper foam composite electrode material according to claim 2, characterized in that, The soluble neodymium salt is neodymium chloride, neodymium sulfate or neodymium nitrate; and / or The soluble manganese salt is manganese chloride, manganese sulfate or manganese nitrate.

4. The preparation method of the nitrogen-doped neodymium sulfide @ manganese sulfide / carbon foam composite electrode material according to claim 2 or 3, characterized in that, In the precursor solution, the concentration of the soluble neodymium salt is 0.6 mmol / L to 1.8 mmol / L, the concentration of the soluble manganese salt is 1.0 mmol / L to 2.1 mmol / L, and the concentration of thiourea is 2.8 mmol / L to 3.8 mmol / L.

5. The preparation method of the nitrogen-doped neodymium sulfide @ manganese sulfide / carbon foam composite electrode material according to claim 2, characterized in that, The volume ratio of the ethylene glycol to water is 1:1.5 to 1:2.

5.

6. The preparation method of the nitrogen-doped neodymium sulfide @ manganese sulfide / carbon foam composite electrode material according to claim 2, wherein, In S2, the reaction time is 4 h to 8 h.

7. The preparation method of the nitrogen-doped neodymium sulfide @ manganese sulfide / carbon foam composite electrode material according to claim 2, characterized in that, Before use, the copper foam undergoes the following pretreatment process: Ultrasonically treat the copper foam in acetone and hydrochloric acid solution for 5 min to 10 min respectively, and then ultrasonically treat it in deionized water for 10 min to 20 min.

8. A nitrogen-doped neodymium sulfide @ manganese sulfide / carbon foam composite electrode material, characterized in that, It is prepared by the preparation method of the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material according to any one of claims 2 to 7.

9. A positive electrode, characterized in that, It includes the nitrogen-doped neodymium sulfide@manganese sulfide / copper foam composite electrode material according to claim 8.

10. A supercapacitor, characterized in that, It includes the positive electrode according to claim 9.

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