Composite electrode material and preparation method thereof, and zinc ion capacitor

Abstract

The application belongs to the technical field of electrochemical energy storage, and discloses a composite electrode material, a preparation method thereof and a zinc ion capacitor. The composite electrode material comprises a carrier and MoS2 loaded on the carrier, wherein the carrier is a nitrogen-doped porous carbon material, and the porous carbon material comprises micropores and mesopores; the MoS2 has a nanosheet layer structure, and the number of layers of the nanosheet layer is 2-6. The application uses the porous carbon material as the carrier, loads the few-layer MoS2 nanosheet on the surface and pores of the porous carbon material, and performs nitrogen doping on the carbon material, thereby improving the stability of the material while improving the conductivity of the material. The zinc ion capacitor with the composite electrode material as the negative electrode has a specific capacity of 48 F / g at a current density of 1 A / g, a capacity retention rate of > 85% at a high current density of 10 A / g, and a capacity retention rate of > 90% after 40000 cycles at a current density of 1 A / g.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, specifically relating to a composite electrode material and its preparation method, and a zinc ion capacitor. Background Technology

[0002] As the global energy structure accelerates its transition towards cleaner and renewable energy, the demand for efficient, safe, and low-cost large-scale energy storage technologies is becoming increasingly urgent. Electrochemical energy storage systems, represented by lithium-ion batteries (LIBs), have achieved great success over the past few decades and are widely used in portable electronic devices and electric vehicles. However, the limited availability of lithium resources, their uneven geographical distribution, the environmental costs of mining, and the inherent flammability and explosiveness of their organic electrolytes severely limit their application prospects in grid-scale large-scale energy storage.

[0003] Aqueous zinc-ion batteries (ZIBs) are considered one of the most promising candidates for large-scale energy storage technology due to their unique advantages. The zinc metal anode possesses a high theoretical specific capacity (820 mAh / g). - ¹) The relatively low redox potential (-0.76V vs. standard hydrogen electrode), good compatibility with aqueous electrolytes, and the advantages of abundant resources, low cost, and environmental friendliness have made ZIBs a hot topic for next-generation energy storage technologies. Nevertheless, the commercialization of ZIBs still faces a series of key challenges. On the cathode side, developing a host material that combines high capacity, long cycle life, and fast reaction kinetics is the core bottleneck. Traditional transition metal oxides or Prussian blue cathodes are prone to structural collapse, dissolution, or side reactions during cycling, leading to rapid capacity decay. On the anode side, the uncontrolled growth of zinc dendrites can puncture the separator and cause short circuits, while accompanying side reactions such as hydrogen evolution and corrosion also reduce coulombic efficiency and cycle stability.

[0004] Therefore, there is an urgent need to develop a new composite electrode material to overcome the technical problems of poor intrinsic conductivity and insufficient cycle stability caused by volume expansion in current electrode materials, so as to improve the electrochemical performance of zinc ion capacitors. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a composite electrode material and its preparation method, as well as a zinc-ion capacitor. This composite electrode material exhibits good conductivity, rate performance, and cycle stability.

[0006] To address the aforementioned technical problems, a first aspect of the present invention provides a composite electrode material comprising a carrier and MoS2 loaded on the carrier, wherein the carrier is a nitrogen-doped porous carbon material, and the pores of the porous carbon material include micropores and mesopores; the MoS2 has a nanosheet structure, and the number of nanosheet layers is 2-6.

[0007] Specifically, MoS2, as a typical layered transition metal sulfide, has an interlayer spacing of 0.659 nm, which can provide diffusion channels for zinc ions and has a high theoretical capacity, but its intrinsic conductivity is poor (10). -5 The practical applications of porous carbon materials are limited by their high conductivity (S / cm) and volume expansion (>200%). While porous carbon materials possess excellent conductivity and a well-developed pore structure, making them ideal conductive frameworks, their capacity is relatively low when used alone as electrodes due to reliance on the electric double layer for energy storage. Directly combining MoS2 with porous carbon materials can improve conductivity, but challenges remain, such as the difficulty in precisely controlling the MoS2 loading (too high a loading can lead to agglomeration and pore blockage, while too low a loading results in insufficient active material), weak interfacial bonding, and the tendency for MoS2 to detach during cycling. To address these issues, this invention uses porous carbon materials with micropores and mesopores as a carrier to provide a three-dimensional conductive network and porous support. Few-layer MoS2 nanosheets are loaded onto the surface and pores of the porous carbon material, while nitrogen doping of the carbon material forms Mo-OC and Mo-NC bonds to enhance the interfacial bonding between MoS2 and the porous carbon material. This improves both the conductivity and the rate performance and stability of the material.

[0008] In some embodiments of the present invention, the pore size of the nitrogen-doped porous carbon material is 1-4 nm.

[0009] The nitrogen-doped porous carbon material of the present invention includes micropores (<2nm) and mesopores (2-4nm), which can construct a fast ion transport channel, and the oxygen-containing functional groups on the surface can form anchoring points with the Mo precursor to ensure uniform loading of MoS2.

[0010] In some embodiments of the present invention, the specific surface area of ​​the composite electrode material is 1000-1200 m². 2 / g. The high specific surface area provides a sufficient active interface for electrochemical reactions.

[0011] In some embodiments of the present invention, the raw materials for preparing the composite electrode material include a molybdenum source, a sulfur source, a nitrogen source, and a carbon source.

[0012] In some embodiments of the present invention, the carbon source is selected from at least one of YP80F activated carbon, YP50F activated carbon, coconut shell activated carbon, and carbon aerogel; preferably YP80F activated carbon.

[0013] In some embodiments of the present invention, the molybdenum source is selected from at least one of ammonium molybdate, sodium molybdate, ammonium molybdate, molybdenum chloride, molybdic acid, and hydrates of the above substances; preferably ammonium molybdate tetrahydrate, whose reactivity with sulfur sources (such as thioacetamide) is easier to control, which is beneficial for the formation of few-layer MoS2.

[0014] In some embodiments of the present invention, the sulfur source is selected from at least one of thioacetamide, thiourea, sodium thiosulfate, sulfur powder, and carbon disulfide; preferably thioacetamide, which has a moderate hydrothermal decomposition rate and can avoid the aggregation of MoS2 due to excessively rapid nucleation.

[0015] In some embodiments of the present invention, the nitrogen source is selected from at least one of urea, ammonia, and melamine; preferably urea, which can complete nitrogen doping in one step during hydrothermal process without additional high-temperature calcination, and the decomposition products have no residual toxicity.

[0016] In some embodiments of the present invention, the molar ratio of the molybdenum source to the sulfur source is 1:(2-6); the preferred molar ratio is 1:(3-5). This range ensures complete sulfidation of MoS2, avoids the formation of the MoO3 impurity phase, and prevents the accumulation of byproducts (such as polysulfides) caused by excessive sulfur source.

[0017] In some embodiments of the present invention, the molar ratio of the molybdenum source to the nitrogen source is 1:(2-10); the preferred molar ratio is 1:(4-8). This range can optimize the nitrogen doping amount of the carbon substrate, providing sufficient active sites while avoiding carbon structure collapse caused by excessive doping.

[0018] In some embodiments of the present invention, the loading amount of MoS2 on the support is 10-35 wt%, that is, the mass ratio of MoS2 to the support is (10-35):100; the preferred loading amount is 10-20 wt%.

[0019] In some embodiments of the present invention, the mass ratio of MoS2 to carbon source is 1:9 to 5:9; the preferred mass ratio is 1:9 to 1:3. This range balances the active material loading and ion diffusion efficiency. If the loading is too low, the capacity contribution will be insufficient; if the loading is too high, MoS2 will easily stack and block the pores, resulting in a decrease in rate performance.

[0020] A second aspect of the present invention provides a method for preparing the composite electrode material described in the first aspect of the present invention, comprising the following steps: The raw material components are mixed and subjected to a hydrothermal reaction to obtain the composite electrode material.

[0021] In some embodiments of the present invention, the hydrothermal reaction is carried out at a temperature of 180-220°C for 12-24 hours.

[0022] In some embodiments of the present invention, the steps of washing and drying are further included after the hydrothermal reaction.

[0023] In some embodiments of the present invention, the washing is performed by washing with deionized water 3-5 times.

[0024] In some embodiments of the present invention, the drying is performed at a temperature of 60-80°C for 1-3 hours.

[0025] In some embodiments of the present invention, the method for preparing the composite electrode material includes the following steps: Molybdenum source, sulfur source, carbon source and nitrogen source are dispersed in deionized water and stirred at 600-800 r / min for 20-40 min to obtain a precursor solution; then the precursor solution is subjected to a hydrothermal reaction, and after the solid is separated, it is washed and dried to obtain the composite electrode material.

[0026] A third aspect of the present invention provides a negative electrode comprising the composite electrode material described in the first aspect of the present invention.

[0027] A fourth aspect of the present invention provides a zinc-ion capacitor including the negative electrode described in the third aspect of the present invention.

[0028] In some embodiments of the present invention, the zinc ion capacitor further includes a positive electrode and an electrolyte, wherein the positive electrode is YP80F activated carbon and the electrolyte is an aqueous solution of ZnI2.

[0029] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages: (1) The present invention uses porous carbon material with micropores and mesopores as a carrier to provide a three-dimensional conductive network and porous support; and loads few-layer MoS2 nanosheets on the surface and pores of the porous carbon material, while nitrogen doping of the carbon material to form Mo-OC and Mo-NC bonds to enhance the interfacial bonding between MoS2 and the porous carbon material. This improves the conductivity of the material, and effectively enhances the rate performance and stability of the material.

[0030] (2) The zinc ion capacitor with the composite electrode material of the present invention as the negative electrode can achieve a specific capacitance of 48 F / g at a current density of 1 A / g, a capacity retention rate of >85% at a high current density of 10 A / g, and a capacity retention rate of >90% after 40,000 cycles at a current density of 1 A / g.

[0031] (3) The composite electrode material of the present invention is prepared by hydrothermal method, which is mild and does not require high-temperature calcination. The raw material cost is low and it is suitable for large-scale production. Attached Figure Description

[0032] Figure 1 The image shows the XRD pattern of the composite electrode material prepared in Example 1. Figure 2 SEM and EDS images of the composite electrode material prepared in Example 1; Figure 3TEM, HRTEM, and SEAD images of the composite electrode material prepared in Example 1; Figure 4 N2 adsorption / desorption isotherms and pore size distribution diagrams of the composite electrode materials prepared in Comparative Example 1 and Example 1; Figure 5 CV diagrams of zinc-ion capacitors prepared in Comparative Example 1 and Examples 1-5; Figure 6 Rate performance graphs of zinc-ion capacitors prepared in Comparative Example 1 and Examples 1-5; Figure 7 EIS plots of zinc-ion capacitors prepared in Comparative Example 1 and Examples 1-5; Figure 8 Cycle life diagrams of zinc-ion capacitors prepared in Comparative Example 1 and Examples 1-5. Detailed Implementation

[0033] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.

[0034] The raw materials used in the following examples and comparative examples are as follows: YP80F activated carbon: KELOD Company, specific surface area 1800m² / g; Ammonium molybdate tetrahydrate: Sinopharm Chemical Reagent Co., Ltd., purity 99%; Thioacetamide: Sinopharm Chemical Reagent Co., Ltd., purity 99%; Urea: Sinopharm Chemical Reagent Co., Ltd., purity 99%.

[0035] Example 1 A method for preparing a composite electrode material includes the following steps: (1) Weigh out 0.9g of YP80F activated carbon, 0.3534g of ammonium molybdate tetrahydrate, 0.336g of thioacetamide, and 1.2g of urea, add them to 30mL of deionized water, and stir magnetically at 650r / min for 30min to obtain the precursor solution; (2) The precursor solution obtained in step (1) was transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave and subjected to hydrothermal reaction at 200 °C for 20 hours. The reaction product was then filtered, washed three times with deionized water, and dried at 65 °C for 2 hours to obtain the composite electrode material of this embodiment, denoted as MoS2@YP80F(3x).

[0036] A method for preparing a zinc-ion capacitor includes the following steps: 1) The composite electrode material prepared above is mixed with conductive carbon black C45 and polytetrafluoroethylene (PTFE) in a mass ratio of 90:5:5. Isopropanol is added and stirred until it forms a ball. After grinding, it is rolled into a carbon film with a thickness of 120μm and cut into round pieces with a diameter of 12mm using a cutting machine. 2) Using the disc obtained in step 1) as the negative electrode, the pure YP80F electrode as the positive electrode, and a 1mol / L ZnI2 aqueous solution as the electrolyte, the zinc ion capacitor of this embodiment is prepared by encapsulating it with a CR2032 button cell shell and pressing it with a hydraulic sealing machine at 5MPa for 10s.

[0037] Example 2 A method for preparing a composite electrode material includes the following steps: (1) Weigh out 0.9g of YP80F activated carbon, 0.1178g of ammonium molybdate tetrahydrate, 0.112g of thioacetamide, and 0.4g of urea respectively, add them to 30mL of deionized water, and stir magnetically at 650r / min for 30min to obtain the precursor solution; (2) The precursor solution obtained in step (1) was transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave and subjected to hydrothermal reaction at 200 °C for 20 hours. The reaction product was then filtered, washed three times with deionized water, and dried at 65 °C for 2 hours to obtain the composite electrode material of this embodiment, denoted as MoS2@YP80F(1x).

[0038] The preparation method of the zinc ion capacitor is the same as that in Example 1.

[0039] Example 3 A method for preparing a composite electrode material includes the following steps: (1) Weigh out 0.9g of YP80F activated carbon, 0.2356g of ammonium molybdate tetrahydrate, 0.224g of thioacetamide, and 0.8g of urea respectively, add them to 30mL of deionized water, and stir magnetically at 650r / min for 30min to obtain the precursor solution; (2) The precursor solution obtained in step (1) was transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave and subjected to hydrothermal reaction at 200 °C for 20 hours. The reaction product was then filtered, washed three times with deionized water, and dried at 65 °C for 2 hours to obtain the composite electrode material of this embodiment, denoted as MoS2@YP80F(2x).

[0040] The preparation method of the zinc ion capacitor is the same as that in Example 1.

[0041] Example 4 A method for preparing a composite electrode material includes the following steps: (1) Weigh out 0.9g of YP80F activated carbon, 0.4712g of ammonium molybdate tetrahydrate, 0.448g of thioacetamide, and 1.6g of urea, add them to 30mL of deionized water, and stir magnetically at 650r / min for 30min to obtain the precursor solution. (2) The precursor solution obtained in step (1) was transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave and subjected to hydrothermal reaction at 200 °C for 20 hours. The reaction product was then filtered, washed three times with deionized water, and dried at 65 °C for 2 hours to obtain the composite electrode material of this embodiment, denoted as MoS2@YP80F(4x).

[0042] The preparation method of the zinc ion capacitor is the same as that in Example 1.

[0043] Example 5 A method for preparing a composite electrode material includes the following steps: (1) Weigh out 0.9g of YP80F activated carbon, 0.589g of ammonium molybdate tetrahydrate, 0.56g of thioacetamide, and 2.0g of urea, add them to 30mL of deionized water, and stir magnetically at 650r / min for 30min to obtain the precursor solution; (2) The precursor solution obtained in step (1) was transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave and subjected to hydrothermal reaction at 200 °C for 20 hours. The reaction product was then filtered, washed three times with deionized water, and dried at 65 °C for 2 hours to obtain the composite electrode material of this embodiment, denoted as MoS2@YP80F(5x).

[0044] The preparation method of the zinc ion capacitor is the same as that in Example 1.

[0045] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that YP80F activated carbon was used as the negative electrode, denoted as YP80F.

[0046] Structural characterization and performance testing 1. Structural Characterization Figure 1 The image shows the XRD (X-ray diffraction) pattern of the composite electrode material prepared in Example 1. The horizontal axis 2Theta represents the diffraction angle 2θ, and the vertical axis Intensity represents the intensity of the diffraction peak. Figure 1 It can be seen that obvious diffraction peaks appeared at 2θ of approximately 14.1°, 33.4°, and 59.3°. These peaks correspond to the (002), (100), and (110) crystal planes of hexagonal MoS2 (space group P63 / mmc), respectively, which are highly consistent with the characteristic diffraction peak positions of MoS2. This confirms that a well-crystallized molybdenum disulfide phase was successfully synthesized in situ on the YP80F activated carbon substrate. Among them, the diffraction peak corresponding to the (002) crystal plane has a relatively high intensity and is relatively sharp, indicating that the synthesized MoS2 has a certain preferred orientation along the c-axis and the grain size is relatively complete. In addition, a broad and diffuse diffraction pattern can be observed near approximately 25° and 44°, which is attributed to the amorphous carbon structure characteristics of the YP80F activated carbon matrix. It is noteworthy that no obvious diffraction peaks of molybdenum oxides (such as MoO2 or MoO3) or other impurities were detected in the entire XRD pattern. This indicates that under hydrothermal synthesis conditions, the precursor ammonium molybdate tetrahydrate and thioacetamide reacted completely, mainly producing pure-phase MoS2, and the carbon substrate maintained its amorphous structure.

[0047] Figure 2 The images shown are SEM (scanning electron microscope) and EDS (energy-dispersive X-ray spectroscopy) images of the composite electrode material prepared in Example 1. Figure 2 (a) and (b) in the figure show typical SEM images of the composite electrode material at low and high magnification, respectively. Figure 2 Image (b) is a magnified view of the surface region to the right of the dashed line in image (a). From the low-magnification image, it can be observed that YP80F activated carbon exhibits a rich, interconnected macroscopic porous framework structure with a relatively rough surface. In the high-magnification image, it can be clearly seen that a large number of lamellar or flower-like nanostructures are uniformly attached to the surface and pore edges of the carbon framework. These nanosheets typically have lateral dimensions between tens and hundreds of nanometers and are relatively thin; they are MoS2 nanosheets grown in situ using a hydrothermal method. The tight bonding between these MoS2 nanosheets and the porous carbon matrix facilitates the construction of an efficient electronic conduction network and provides numerous electrochemically active interfaces. To verify the distribution of Mo and S elements on the carbon substrate, [further details are needed]. Figure 2 EDS elemental surface scan analysis was performed on region (b) in the image, and the results are as follows: Figure 2 As shown in (c)-(g), the distribution maps of Mo and S elements clearly show that the signal intensity distribution regions of these two elements highly overlap and are consistent with... Figure 2The lamellar morphology regions in (b) match well, directly demonstrating that these nanosheets are indeed MoS2. Simultaneously, carbon (C) is uniformly distributed throughout the field of view, forming a continuous network corresponding to the YP80F carbon substrate. O and N elements also show a degree of uniform distribution. O may originate from oxygen-containing functional groups on the carbon substrate surface, trace amounts of adsorption from the air, or precursor decomposition products, while N mainly originates from doping into the carbon framework after urea decomposition or residual nitrogen-containing groups. This coexistence and interwoven distribution of Mo, S, C, O, and N elements confirms that MoS2 forms a tight composite with the carbon matrix.

[0048] Figure 3 TEM (transmission electron microscopy), HRTEM (high-resolution transmission electron microscopy), and SEAD (selected area electron diffraction) images of the composite electrode material prepared in Example 1. Figure 3 The TEM image in (a) visually demonstrates the overall morphology of MoS2 nanosheets attached to a relatively light-contrast carbon substrate. The nanosheets are translucent with clear edge wrinkles, further confirming that they have a small number of layers. Figure 3 The HRTEM images in (b) and (c) provide information at the atomic scale. Figure 3 In (b), clear lattice fringes can be observed, and the interplanar spacing is measured to be approximately 0.659 nm, which perfectly matches the (002) interplanar spacing of hexagonal MoS2, further confirming the crystal structure of the synthesized MoS2. Figure 3 In (c), the stacking of the MoS2 layered structure can even be distinguished, measuring approximately 4-6 atomic layers, which is characteristic of few-layer MoS2. This facilitates rapid ion insertion / extraction between layers. SAED analysis results of the selected region are as follows: Figure 3 As shown in (d), the SAED pattern exhibits a series of concentric polycrystalline diffraction rings, rather than single-crystal diffraction spots. This polycrystalline diffraction ring characteristic indicates the presence of a large number of MoS2 microcrystals with different orientations within the micro-area irradiated by the electron beam. This is consistent with the SEM observations of MoS2 grown randomly on a carbon substrate, and also demonstrates that MoS2 in the composite material has good polycrystalline properties.

[0049] Figure 4 The N2 adsorption / desorption isotherms (a) and pore size distribution (b) of the composite electrode materials prepared in Comparative Example 1 and Example 1 are shown below. Figure 4As shown in (a), the isotherm of pure YP80F exhibits typical Type IV isotherm characteristics with a distinct H4 type hysteresis loop, a common feature of carbon materials with slit-like mesopores. Its adsorption capacity increases rapidly at lower relative pressures (P / P0), indicating abundant micropores; the hysteresis loop appearing in the middle of the relative pressure range confirms the presence of mesopores. After loading MoS2, the isotherm of MoS2@YP80F still maintains Type IV characteristics, but the shape and position of the hysteresis loop change, and the total adsorbed quantity decreases. This indicates that the introduction of MoS2 partially occupies the original pore space of the carbon substrate, particularly some micropores and smaller mesopores may be blocked or covered by MoS2 nanosheets, leading to a decrease in specific surface area. However, the continued presence of the hysteresis loop indicates that the mesoporous framework of the material is maintained. Calculations using the BET model show that the specific surface area of ​​pure YP80F is as high as 1800 m² / g, while that of MoS2@YP80F decreases to 1200 m² / g, a change consistent with the above analysis. Although the specific surface area is somewhat sacrificed, the value of 1200 m² / g is still very considerable, providing sufficient active interfaces for electrochemical reactions.

[0050] Figure 4 Figure (b) shows the pore size distribution curves calculated from the desorption branch using the BJH method. It can be seen that pure YP80F has a wide pore size distribution range, mainly concentrated in the 1-4 nm micropore / small mesopore region, with a noticeable peak at approximately 3.8 nm. The pore size distribution curve of MoS2@YP80F shifts towards slightly larger pore sizes overall, with a weakened peak intensity in the 1-4 nm region, while the peak near approximately 4 nm becomes more prominent, and the average pore size increases slightly. A possible explanation for this phenomenon is that MoS2 preferentially grows at smaller micropore inlets or on the inner surface of pores, thus "smoothing" part of the micropore structure, causing the detectable pore size distribution to concentrate in a larger mesopore range. This evolution of pore structure has two sides: on the one hand, the reduction in micropores will result in a loss of some double-layer capacitance contribution; on the other hand, the relative increase in the proportion of mesopores is more favorable for electrolyte ions (such as Zn²⁺). + I - The rapid transport of ions reduces diffusion resistance, making it more advantageous for battery applications requiring rapid charge and discharge. Overall, the MoS2@YP80F composite material inherits the advantages of YP80F's high specific surface area and porosity. Simultaneously, the composite structure of MoS2 modulates its pore structure, forming a hierarchical porous structure that combines high ion accessibility surface area with suitable ion transport channels. This lays the structural foundation for its excellent electrochemical performance.

[0051] 2. Electrochemical performance (1) Ratio performance Figure 5 In the figures (a)-(f), the CV curves of the zinc-ion capacitors prepared in Comparative Example 1 and Examples 1-5 are shown respectively. Compared with the standard rectangular CV curve of a pure YP80F symmetrical capacitor, the CV curves of the composite anode devices incorporating MoS2 all exhibit a "bulging rectangular" shape. This conclusively proves that the introduction of MoS2 successfully introduces a significant Faraday pseudocapacitive contribution to the device, transforming the energy storage mechanism from purely physical adsorption (electric double layer) to a capacitor-cell hybrid. This "bulging" directly translates into a significant increase in the area enclosed by the CV curve, meaning that the total specific capacity (C) and energy density (E) of the device are greatly improved. Meanwhile, as the MoS2 loading increases from 1x to 5x, the current response and the area enclosed by the curve first increase and then decrease. Figure 5 In (c), the device fabricated from the 3x sample (Example 1) exhibited the highest instantaneous current and largest area under the curve, indicating that at this loading level, the utilization of the active material (MoS2) was highest, providing peak pseudocapacitance. However, the optimal loading level involves a balance between capacity and rate performance (performance retention at high scan rates). Figure 5 In (c), the rectangular shape is best preserved under high-speed scanning (10 mV / s), indicating optimal ion and electron transport dynamics and minimal polarization. Figure 5 The devices in (e) and (f) exhibit more pronounced curve distortion at high scan rates, indicating that excessive MoS2 loading may have caused negative effects.

[0052] Figure 6 The rate performance diagrams for the zinc-ion capacitors prepared in Comparative Example 1 and Examples 1-5 are provided by... Figure 6 It can be seen that in 1Ag -1 At the given current density, the MoS2@YP80F / / YP80F zinc ion capacitances of different MoS2 loadings (1x to 5x) in Examples 1-5 are as follows: the specific capacitance of the 1x sample (Example 3) is approximately 48 F g. - ¹, exhibiting optimal loading capacity. The specific capacitance of the 2x sample (Example 2) is approximately 44 F g. - ¹. The specific capacitance of the 3x sample (Example 1) is approximately 41 F g. - ¹. The specific capacitance of the 4x sample (Example 4) is approximately 37 F g. - ¹. The specific capacitance of the 5x sample (Example 5) is approximately 33 F g. - ¹. The pure carbon symmetric device YP80F has the lowest specific capacitance (Comparative Example 1), estimated to be 18 F g under the same conditions based on the curve trend. - ¹. That is, the composite electrode material with a 1x loading exhibits the best performance, reaching 1A g. -¹ It provides the highest specific capacity (48 F g) - ¹), which is about 2.7 times that of pure carbon devices.

[0053] (2) Electrical conductivity Figure 7 The EIS spectra of the zinc-ion capacitors prepared in Comparative Example 1 and Examples 1-5 clearly show that as the MoS2 loading increases from 1x to 5x, the internal resistance of the device systematically deteriorates, revealing the root cause of the performance degradation. The increasing semicircle diameter in the high-frequency region directly quantifies the charge transfer resistance (Ro). ct The increase in the resistance of the electron transport path (Warburg impedance) indicates that, although MoS2 itself is an active material, excessive loading makes electron transfer between MoS2 particles or from MoS2 to the conductive carbon substrate (YP80F) more difficult. Deterioration of the conductive network: Excessive, poorly conductive MoS2 partially covers or isolates the highly conductive YP80F carbon network, increasing the tortuosity and resistance of the electron transport path. Although the number of contact points between MoS2 and YP80F, and between MoS2 particles, increases, the contact quality may decrease due to stacking, introducing more interfacial resistance. Severely impeded bulk ion diffusion: The slope in the low-frequency region changes from steep (nearly 90°) to gentle, a clear signal of a significant increase in ion diffusion resistance (Warburg impedance). This indicates that zinc ions (Zn²⁺) are significantly hindered. + The transport within the electrode material becomes increasingly slower. The fundamental reasons are: pore blockage and channel narrowing: excessive MoS2 nanosheets block the abundant mesopores and macropores of YP80F itself, while excessive stacking also forms a dense, tortuous nanolayered structure, severely hindering the bulk diffusion of electrolyte ions. The effective diffusion path is lengthened: ions need to bypass or pass through these stacked MoS2 sheets to reach the active site, increasing the path length and naturally slowing down the kinetics. EIS kinetic data explain the performance trends observed in the CV and GCD plots: for the 1x sample, the minimum R... ct Its low diffusion resistance enables efficient charge storage and release at all current densities. Therefore, in GCD testing, it exhibits minimal IR drop and optimal rate performance (high capacity retention at high currents). For 3x and 4x samples, R... ctThe diffusion resistance is moderately increased. They gain more active sites (MoS2) at an acceptable kinetic cost, thus achieving the highest absolute capacity (longest GCD discharge time) at low to medium current densities. For the 5x sample, the huge kinetic resistance becomes a bottleneck. Even with the highest total amount of active material, most cannot be effectively utilized during rapid charge and discharge, leading to a sharp capacity decay and the largest IR drop in high-rate GCD tests. This is corroborated by the curve distortion in CV: in the CV plot, the curves of highly loaded samples (such as 4x and 5x) distort from rectangular to elliptical at high scan rates, directly reflecting that their ion diffusion rate cannot keep up with the rapid voltage change (i.e., excessive Warburg impedance), which is completely consistent with the EIS conclusions. Figure 7 The 1x loading represents the "kinetically optimal solution." It maximizes the high conductivity and porosity of the YP80F carbon framework, ensuring extreme electron / ion transport rates, making it ideal for ultra-high power applications. The 3x and 4x loadings represent the "capacity-kinetic balance solution." This is within the acceptable range of kinetic performance degradation (R0). ct (And diffusion resistance did not deteriorate significantly), maximizing the loading and utilization of active material, thus achieving the best balance between energy density and power density, making it a comprehensive and preferred option that balances high energy and high power. Loadings of 5x and above, however, fall into the "overloading trap." The newly added active material, due to severe kinetic limitations, cannot contribute to the effective capacity and instead becomes a "dead weight" hindering transmission, leading to a decline in various performance indicators.

[0054] (3) Cyclic stability Figure 8The electrochemical stability test results of YP80F (Comparative Example 1) and composite materials with different loadings (Examples 1-5, i.e., 1x-5x) are visually demonstrated after 40,000 cycles at a current density of 1 A / g. Regarding capacitance retention, all samples exhibited extremely long cycle lives; the capacity not only did not decay but also showed a stepwise activation growth trend with each cycle. Specifically, the final capacitance retention of YP80F was 105.6%, while all composite material samples showed significant improvements. The retention rates of the 1x, 2x, 3x, 4x, and 5x samples reached 117.5%, 101.3%, 108.6%, 113.6%, and 116.7%, respectively. This fully demonstrates the excellent structural stability and continuously exposed new active sites of the composite materials during long-term cycling. Meanwhile, observation of coulombic efficiency reveals that both the YP80F and the 1x-5x composite materials maintain an extremely stable coulombic efficiency close to 100% throughout the entire 40,000 cycles, with the curves almost completely overlapping. This indicates that the battery exhibits extremely high charge transfer efficiency and extremely low reversibility loss during charge and discharge. In summary, this chart strongly confirms the reliability of the prepared zinc-ion capacitor under extremely long cycling conditions, especially the excellent electrochemical performance of the composite material system, which achieves a capacity retention rate exceeding 90% (actually greater than 100%) and the absence of side reactions.

[0055] For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.

Claims

1. A composite electrode material, characterized in that, The invention includes a support and MoS2 loaded on the support, wherein the support is a nitrogen-doped porous carbon material, and the pores of the porous carbon material include micropores and mesopores; the MoS2 has a nanosheet structure, and the number of nanosheets is 2-6 layers.

2. The composite electrode material according to claim 1, characterized in that, The nitrogen-doped porous carbon material has a pore size of 1-4 nm.

3. The composite electrode material according to claim 1 or 2, characterized in that, The specific surface area of ​​the composite electrode material is 1000-1200 m². 2 / g.

4. The composite electrode material according to claim 1, characterized in that, Its raw materials include molybdenum source, sulfur source, nitrogen source and carbon source; The carbon source is selected from at least one of YP80F activated carbon, YP50F activated carbon, coconut shell activated carbon, and carbon aerogel; The molybdenum source is selected from at least one of ammonium molybdate, sodium molybdate, ammonium molybdate, molybdenum chloride, molybdic acid, and hydrates of the above substances; The sulfur source is selected from at least one of thioacetamide, thiourea, sodium thiosulfate, sulfur powder, and carbon disulfide; The nitrogen source is selected from at least one of urea, ammonia, and melamine.

5. The composite electrode material according to claim 4, characterized in that, The molar ratio of the molybdenum source to the sulfur source is 1:(2-6); and / or the molar ratio of the molybdenum source to the nitrogen source is 1:(2-10).

6. The composite electrode material according to claim 5, characterized in that, The loading of MoS2 on the support is 10-35 wt%.

7. A method for preparing the composite electrode material according to any one of claims 1-6, characterized in that, Includes the following steps: The raw material components are mixed and subjected to a hydrothermal reaction to obtain the composite electrode material.

8. The method for preparing the composite electrode material according to claim 7, characterized in that, The hydrothermal reaction is carried out at a temperature of 180-220℃ for 12-24 hours.

9. A negative electrode, characterized in that, Includes the composite electrode material described in any one of claims 1-6.

10. A zinc-ion capacitor, characterized in that, Includes the negative electrode as described in claim 9.

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