Preparation method and application of montmorillonite composite electrode material loaded on basis of manganese-cobalt oxide

Abstract

The invention discloses a preparation method and application of a manganese-cobalt oxide loaded montmorillonite composite electrode material (HSMnCo), cobalt-manganese bimetal oxide is loaded between layered structures of montmorillonite through a hydrothermal method and high-temperature calcination, and the HSMnCo with a unique multi-fold and multi-layer coralline structure is obtained. Montmorillonite (MON) is used as a natural mineral, has good environmental compatibility, and meets the modern green and environment-friendly development requirements. And the optimized electrode material has excellent performance in the application of asymmetric supercapacitors and zinc ion supercapacitors, and a new way is provided for the development of green energy storage devices with high cost performance.

Description

Technical Field

[0001] The present invention relates to the field of electrode materials, and specifically relates to a preparation method and application of a montmorillonite composite electrode material based on manganese cobalt oxide loading. Background Art

[0002] With the continuous growth of global energy demand and the increasingly severe environmental problems, the development of new efficient and environmentally friendly energy storage technologies has become the current research focus. As an energy storage device between traditional capacitors and batteries, supercapacitors exhibit broad application prospects in fields such as electric vehicles, smart grids, and portable electronic devices due to their high power density (up to 10 kW / kg), fast charge and discharge ability (completed in seconds), and ultra-long cycle life (>100,000 times). However, limited by the energy storage mechanism, the energy density of traditional supercapacitors (usually <10 Wh / kg) is much lower than that of lithium-ion batteries (100 - 265 Wh / kg). Existing supercapacitor electrode materials still have problems such as low specific surface area, insufficient electron transfer efficiency, and poor cycle stability, which limit the further improvement of their energy density and severely restrict their large-scale commercial applications.

[0003] As the core component of supercapacitors, the performance of electrode materials directly determines the energy storage characteristics of the devices. Currently, supercapacitor electrode materials are mainly divided into three categories: carbon-based materials (electric double-layer capacitors), metal oxides / conductive polymers (pseudocapacitive materials), and their composites. Among them, carbon materials such as activated carbon and graphene have high specific surface area and excellent cycle stability, but their specific capacitance is relatively low (usually <200 F / g); while transition metal oxides such as RuO2 and MnO2 can provide high specific capacitance (up to 1000 F / g), but they face problems such as high cost or poor conductivity. Therefore, developing new electrode materials with both high specific capacitance, excellent rate performance, and long cycle life has become the key to breaking through the performance bottleneck of supercapacitors.

[0004] Montmorillonite (MON) is a layered silicate mineral with high specific surface area, excellent ion exchange ability, and structural stability. It can provide abundant active sites for electrode materials, and MON contains exchangeable cations between layers. These characteristics endow it with unique advantages in the field of electrochemical energy storage: 1) The layered structure can provide a fast channel for ion transport; 2) The high specific surface area is beneficial to increasing the electrode / electrolyte contact interface; 3) The excellent chemical and thermal stability can ensure the long-term cycle performance of the electrode.

[0005] However, the electrochemical activity of single montmorillonite material is limited and difficult to meet the requirements of high-performance supercapacitors. Therefore, how to improve the electrochemical performance of montmorillonite by compounding with other functional materials has become a current research hotspot.

[0006] Manganese-cobalt bimetallic oxides can significantly enhance the pseudocapacitance characteristics of electrode materials due to their multiple redox states and synergistic effects. Manganese exists in multiple oxidation states (such as Mn 2+ , Mn 3+ , Mn 4+ ). During the electrode reaction process, these manganese ions with different valence states can achieve charge storage through rapid redox reactions, generating pseudocapacitance. Cobalt, on the other hand, has good electrical conductivity, which can optimize the electron transport path of the electrode material and reduce the charge transfer resistance.

[0007] Based on this, the present invention attempts to compound manganese-cobalt bimetallic oxides with montmorillonite to design a high-performance supercapacitor electrode material. Summary of the Invention

[0008] The object of the present invention is to provide a preparation method of a montmorillonite composite electrode material based on manganese-cobalt oxide loading. By means of hydrothermal method and high-temperature calcination, cobalt-manganese bimetallic oxides are loaded between the layered structures of montmorillonite, obtaining a montmorillonite composite electrode material with a coral-like structure having multiple folds. This unique structure endows it with a large specific surface area (200 - 250 m 2 / g) and an optimized pore size distribution (5 - 10 nm), providing abundant active sites for charge storage.

[0009] The present invention also aims to provide the application of the above-mentioned montmorillonite composite electrode material based on manganese-cobalt oxide loading as a supercapacitor device.

[0010] To achieve the above object, the solution of the present invention is as follows: A preparation method of a montmorillonite composite electrode material based on manganese-cobalt oxide loading, comprising the following steps: Step 1, Pretreatment of montmorillonite: First, disperse 3 - 5 g of montmorillonite in 150 mL of an acidic solution with a concentration of 1.5 - 2 mol / L, stir for 4 - 6 hours, and then perform ultrasonic treatment for 30 minutes to remove impurities (such as Ca 2+ , Mg 2+ and other impurity ions) between the layers of montmorillonite, and introduce -Si-OH active sites on the surface of the silicon-oxygen tetrahedron through proton exchange, thereby activating the surface of montmorillonite; Step 2, Hydrothermal reaction: Then transfer the pretreated montmorillonite to a reaction kettle and carry out a hydrothermal reaction at 160 - 200 °C for 10 - 12 hours to promote the expansion of the layer spacing of montmorillonite under a high-temperature and high-pressure environment; Step 3, High-temperature calcination: Then transfer the montmorillonite that has undergone the hydrothermal reaction to a tubular furnace and calcine it at 800 - 900 °C for 2 - 3 hours, so that part of the montmorillonite is dehydroxylated to form a -Si-O-Si- network structure, and finally activated montmorillonite (HS) is obtained; Step 4: Prepare the precursor solution: Then dissolve 2 mmol of ammonium salt, 2 mmol of divalent manganese salt, and 2 - 6 mmol of divalent cobalt salt in 120 - 150 mL of deionized water, and control the Mn 2+ / Co 2+ molar ratio to be 1:1 - 1:3 to obtain the precursor solution; Step 5: Loading of manganese - cobalt metal oxides: Then add 0.2 g of HS to 120 - 150 mL of the precursor solution and stir for 4 - 6 hours, so that the Mn 2+ / Co 2+ in the precursor solution undergoes ion exchange with the interlayer Si 4+ of montmorillonite. Subsequently, carry out hydrothermal reaction at 160 - 180 °C for 10 - 12 hours, centrifuge to collect the product, wash it 2 - 3 times with ethanol and deionized water, and finally dry it at 50 - 70 °C for 12 - 24 hours to obtain the montmorillonite - based composite electrode material loaded with manganese - cobalt oxides, denoted as HSMnCo; In Step 4, the ammonium salt is NH4Cl or NH4NO3, the divalent manganese salt is manganese acetate tetrahydrate (Mn(Ac)2·4H2O) or manganese nitrate tetrahydrate (Mn(NO3)2·4H2O), and the divalent cobalt salt is cobalt acetate tetrahydrate (Co(Ac)2·4H2O) or cobalt nitrate tetrahydrate (Co(NO3)2·4H2O).

[0011] In Step 1, the acidic solution is HCl solution, HNO3 solution, or H2SO3 solution.

[0012] The specific surface area of the montmorillonite - based composite electrode material loaded with manganese - cobalt oxides is 200 - 250 m 2 / g, and the pore size is 5 - 10 nm.

[0013] The application of a montmorillonite - based composite electrode material loaded with manganese - cobalt oxides as a supercapacitor electrode material is to assemble an asymmetric supercapacitor with HSMnCo as the positive electrode, activated carbon as the negative electrode, and KOH as the electrolyte.

[0014] At a current density of 0.5 - 10 A / g, the energy density of the asymmetric supercapacitor is ≥25 Wh / kg, the power density is ≥270 W / kg, and the capacity retention rate is ≥80% after 5000 cycles.

[0015] The invention discloses an application of a montmorillonite composite electrode material loaded with manganese cobalt oxide as a supercapacitor electrode material, wherein HSMnCo is used as a positive electrode, zinc foil is used as a negative electrode, and Zn(CF3SO3)2 is used as an electrolyte to assemble a zinc ion supercapacitor.

[0016] At a current density of 0.5-10 A / g, the energy density of the zinc ion supercapacitor is ≥25 Wh / kg, the power density is ≥350 W / kg, and the capacity retention rate is ≥90% after 5000 cycles.

[0017] After adopting the above technical scheme, the present invention provides a method for preparing a montmorillonite composite electrode material based on manganese-cobalt oxide loading, wherein the cobalt-manganese bimetallic oxide is loaded between the layered structures of montmorillonite by a hydrothermal method and high-temperature calcination. Since MON has a high ion exchange capacity, the exchangeable cation Si between the layers 4+ Can be combined with Mn 2+ 、Co 2+ An exchange reaction occurs, and Mn 2+ 、Co 2+ There is a synergistic and competitive effect between the two. The cobalt manganese oxide grown in situ on the surface of MON will restrict the movement and agglomeration of montmorillonite flakes, making it maintain a relatively loose structure. At the same time, the growth of cobalt manganese oxide will fill the gaps between MON flakes, further changing the pore structure and macroscopic morphology of montmorillonite, thereby obtaining a montmorillonite composite electrode material with a multi-fold coral-like structure.

[0018] The present invention provides a method for preparing a montmorillonite composite electrode material based on manganese-cobalt oxide loading and its application, which has the following beneficial effects: 1. Innovation in material design: The first composite structure of "montmorillonite skeleton-bimetallic active center" has both high conductivity and abundant redox sites. 2+ / Co 2+ ratio and hydrothermal reaction conditions to obtain optimal electrochemical performance; 2. High specific capacitance: The assembled asymmetric supercapacitor HSMnCo / / AC has a specific capacitance of up to 259 F / g at a current density of 0.5 A / g, thanks to the synergistic effect of the manganese-cobalt bimetallic, which optimizes the electron transmission path, promotes the redox reaction, and increases the charge storage capacity; 3. Excellent cycle stability: After 5000 cycles, the capacity retention rate of the HSMnCo supercapacitor is still 84.2%. Its multi-folded coral-like structure can effectively buffer the structural stress during charge and discharge processes, reduce the structural damage of the electrode material, and thus ensure good cycle stability. When the zinc-ion supercapacitor is cycled 5000 times, due to the good reversibility of the insertion and extraction reactions of zinc ions in the electrode material, the cycle life of the zinc-ion supercapacitor is further extended. Therefore, the capacitance retention rate of the HSMnCo zinc-ion supercapacitor is 94.7%, higher than that of the HSMnCo supercapacitor (84.2%); 4. High energy density and power density: The assembled asymmetric supercapacitor (HSMnCo / / AC) achieved a relatively high energy density (43.53 Wh / kg) and power density (279.83 W / kg) in 6M KOH electrolyte. In the zinc-ion supercapacitor, the energy density and power density are further improved. When the power density is 374.78 W / kg, the energy density reaches 177.50 Wh / kg; 5. Structural advantages: The multi-folded coral-like structure of the composite electrode material increases the specific surface area and porosity, optimizes the ion diffusion path, and the charge transfer resistance (Rct) is as low as 3.58 Ω; 6. Resource utilization and cost advantages: The present invention uses montmorillonite, a mineral with rich reserves and low cost, as the substrate, realizes the high-value utilization of resources such as silicate, reduces the manufacturing cost of the electrode material, and meets the requirements of sustainable development; 7. Broad application prospects: It is applicable to traditional supercapacitors and emerging zinc-ion energy storage devices. The raw material cost is 98% lower than that of commercial RuO2, with significant economic benefits. Brief Description of the Drawings

[0019] Figure 1 is a schematic diagram of the preparation process of HSMnCo; Figure 2 are electron micrographs of the prepared HSMn, HSCo, and HSMnCo, where (a) is the SEM image of HSMn, (b) is the SEM image of HSCo, (c) is the SEM image of HSMnCo, (d) is the TEM image of HSMnCo, and (e) and (f) are the lattice analyses of the TEM image in (d); Figure 3 are characterization diagrams of the prepared HSMn, HSCo, and HSMnCo materials, where (a) is the XRD diagram, (b) is the XPS full spectrum; (c) is the Co2p fine spectrum; (d) is the Mn2p fine spectrum; (e) is the O1s fine spectrum; (f) is the nitrogen adsorption-desorption isotherm and specific surface area of HSMn, HSCo, and HSMnCo; Figure 4 Charge and discharge performance diagrams of a three-electrode supercapacitor assembled by HS, HSMn, HSCo, and HSMnCo, where (a) and (b) are the CV curve and the GCD curve, respectively; Figure 5 Charge and discharge performance diagrams of the HSMnCo / / AC supercapacitor, where (a)–(b) are the CV curve and the GCD curve of the HSMnCo / / AC supercapacitor, respectively; (c) is the performance diagram of the HSMnCo / / AC supercapacitor for 5000 long cycles at a current density of 5 A / g; Figure 6 Charge and discharge performance and cycle stability performance diagrams of a zinc-ion supercapacitor, where (a) and (b) are the CV curve and the GCD curve of the HSMnCo zinc-ion supercapacitor, respectively; (c) is the comparison of power density and energy density of different materials; (d) is the performance diagram of the HSMnCo zinc-ion supercapacitor for 5000 long cycles at a current density of 5 A / g; (e) is the SEM comparison diagram of the HSMnCo material before and after long cycles. Specific implementation manners

[0020] To further explain the technical solution of the present invention, the present invention will be elaborated in detail through specific embodiments below.

[0021] I. Preparation of montmorillonite composite electrode material Example 1 A preparation method of a montmorillonite composite electrode material based on manganese cobalt oxide loading, as Figure 1 shown, includes the following steps: Step 1. Pretreatment of montmorillonite: First, disperse 3 g of montmorillonite in 150 mL of 1.5 mol / L HCl solution, stir for 4 hours, and then perform ultrasonic treatment for 30 minutes to remove impurities (such as Ca 2+ , Mg 2+ and other impurity ions) between the montmorillonite layers, and introduce -Si-OH active sites on the surface of the silicon oxygen tetrahedron through proton exchange, thereby activating the surface of the montmorillonite; Step 2. Hydrothermal reaction: Then transfer the pretreated montmorillonite to a reaction kettle with a polytetrafluoroethylene liner of 200 mL, and carry out a hydrothermal reaction at 160 °C for 10 hours to promote the expansion of the layer spacing of the montmorillonite under a high-temperature and high-pressure environment; Step 3. High-temperature calcination: Then transfer the montmorillonite that has undergone the hydrothermal reaction to a tubular furnace and calcine it at 800 °C for 2 hours to cause partial dehydroxylation of the montmorillonite to form a -Si-O-Si- network structure, and finally obtain activated montmorillonite (HS); Step 4: Prepare the precursor solution: Then dissolve 2 mmol of NH4Cl, 2 mmol of Mn(Ac)2·4H2O, and 4 mmol of Co(Ac)2·4H2O in 150 mL of deionized water, and control the Mn 2+ / Co 2+ molar ratio to be 1:2 to obtain the precursor solution; Step 5: Loading of manganese-cobalt metal oxide: Then add 0.2 g of HS to 150 mL of the precursor solution and stir for 5 hours to enable the Mn 2+ / Co 2+ in the precursor solution to undergo ion exchange with the interlayer Si 4+ of montmorillonite, and then carry out a hydrothermal reaction at 180 °C for 12 hours. Centrifuge to collect the product, wash it 3 times with ethanol and deionized water, and finally dry it at 60 °C for 12 hours to obtain the montmorillonite composite electrode material based on manganese-cobalt oxide loading, denoted as HSMnCo.

[0022] Example 2 A preparation method of a montmorillonite composite electrode material based on manganese-cobalt oxide loading, comprising the following steps: Step 1: Pretreatment of montmorillonite: First, disperse 5 g of montmorillonite in 150 mL of 2.0 mol / L HNO3 solution, stir for 6 hours, and then ultrasonically treat for 30 minutes to remove the impurities (such as Ca 2+ , Mg 2+ and other impurity ions) in the interlayer of montmorillonite, and introduce -Si-OH active sites on the surface of the silicon-oxygen tetrahedron through proton exchange, thereby activating the surface of montmorillonite; Step 2: Hydrothermal reaction: Then transfer the pretreated montmorillonite to a reaction kettle with a polytetrafluoroethylene inner liner of 200 mL and carry out a hydrothermal reaction at 200 °C for 12 hours to promote the expansion of the layer spacing of montmorillonite under high temperature and high pressure; Step 3: High-temperature calcination: Then transfer the montmorillonite that has undergone the hydrothermal reaction to a tubular furnace and calcine it at 900 °C for 3 hours to cause partial dehydroxylation of montmorillonite to form a -Si-O-Si- network structure, and finally obtain activated montmorillonite (HS); Step 4: Prepare the precursor solution: Then dissolve 2 mmol of NH4NO3, 2 mmol of Mn(NO3)2·4H2O, and 6 mmol of Co(NO3)2·4H2O in 150 mL of deionized water, and control the Mn 2+ / Co 2+ molar ratio to be 1:3 to obtain the precursor solution; Step 5: Loading of manganese-cobalt metal oxide Then, 0.2 g of HS was added to 120 mL of the precursor solution and stirred for 6 hours, so that Mn 2+ / Co 2+ in the precursor solution underwent ion exchange with the interlayer Si 4+ of montmorillonite. Subsequently, a hydrothermal reaction was carried out at 160 °C for 10 hours. The product was collected by centrifugation, washed 3 times with ethanol and deionized water, and finally dried at 50 °C for 24 hours to obtain the montmorillonite composite electrode material loaded with manganese-cobalt oxide, denoted as HSMnCo.

[0023] Comparative Example 1 A preparation method of a montmorillonite composite electrode material loaded with manganese oxide, comprising the following steps: Step 1: Pretreatment of montmorillonite First, 3 g of montmorillonite was dispersed in 150 mL of 1.5 mol / L HCl solution, stirred for 4 hours and then ultrasonically treated for 30 minutes to remove impurities (such as Ca 2+ , Mg 2+ and other impurity ions) in the interlayer of montmorillonite, and -Si-OH active sites were introduced on the surface of the silicon-oxygen tetrahedron through proton exchange, thereby activating the surface of montmorillonite; Step 2: Hydrothermal reaction Then, the pretreated montmorillonite was transferred to a reaction kettle with a polytetrafluoroethylene inner lining of 200 mL, and a hydrothermal reaction was carried out at 160 °C for 10 hours to expand the interlayer spacing of montmorillonite under high temperature and high pressure environment; Step 3: High-temperature calcination Then, the montmorillonite that had undergone the hydrothermal reaction was transferred to a tubular furnace and calcined at 800 °C for 2 hours, so that montmorillonite partially dehydroxylated to form a -Si-O-Si- network structure, and finally activated montmorillonite (HS) was obtained; Step 4: Preparation of precursor solution Then, 2 mmol of NH4Cl and 2 mmol of Mn(Ac)2·4H2O were dissolved in 150 mL of deionized water to obtain the precursor solution; Step 5: Loading of manganese oxide Then, 0.2 g of HS was added to 150 mL of the precursor solution and stirred for 5 hours. Subsequently, a hydrothermal reaction was carried out at 180 °C for 12 hours. The product was collected by centrifugation, washed 3 times with ethanol and deionized water, and finally dried at 60 °C for 12 hours to obtain the montmorillonite composite electrode material loaded with manganese oxide, denoted as HSMn.

[0024] Comparative Example 2 A preparation method of a montmorillonite composite electrode material supported by cobalt oxide, as Figure 1 shown, includes the following steps: Step 1. Pretreatment of montmorillonite: First, disperse 3 g of montmorillonite in 150 mL of 1.5 mol / L HCl solution, stir for 4 hours, and then ultrasonically treat for 30 minutes to remove impurities (such as Ca 2+ , Mg 2+ and other impurity ions) between the montmorillonite layers, and introduce -Si-OH active sites on the surface of the silicon-oxygen tetrahedron through proton exchange, thereby activating the surface of montmorillonite; Step 2. Hydrothermal reaction: Then transfer the pretreated montmorillonite to a reaction kettle with a polytetrafluoroethylene inner lining of 200 mL, and carry out a hydrothermal reaction at 160 °C for 10 hours to promote the expansion of the layer spacing of montmorillonite under a high-temperature and high-pressure environment; Step 3. High-temperature calcination: Then transfer the montmorillonite after the hydrothermal reaction to a tubular furnace and calcine at 800 °C for 2 hours, so that montmorillonite is partially dehydroxylated to form a -Si-O-Si- network structure, and finally activated montmorillonite (HS) is obtained; Step 4. Preparation of precursor solution: Then dissolve 2 mmol of NH4Cl and 4 mmol of Co(Ac)2·4H2O in 150 mL of deionized water to obtain a precursor solution; Step 5. Loading of manganese-cobalt metal oxide: Then add 0.2 g of HS to 150 mL of the precursor solution, stir for 5 hours, then carry out a hydrothermal reaction at 180 °C for 12 hours, centrifuge to collect the product, wash it 3 times with ethanol and deionized water, and finally dry it at 60 °C for 12 hours to obtain the montmorillonite composite electrode material supported by cobalt oxide, denoted as HSCo.

[0025] II. Characterization of montmorillonite electrode material 1. SEM and TEM characterization Figure 2 The electron micrographs of HSMn, HSCo, and HSMnCo are shown. When Mn 2+ , Co 2+ ions are added simultaneously, there are competitive and synergistic effects during the adsorption process of the two metal ions on the HS surface, resulting in a transformation of the material structure. The bulk stacking structures of HSMn and HSCo disappear, replaced by a multi-folded and multi-layered coral structure. Moreover, the TEM image of HSMnCo is consistent with the SEM characterization. By analyzing and calculating the lattice spacing of 0.213 nm (220), it can be confirmed that the obtained material is manganese-cobalt oxide (CoMn2O4).

[0026] 2. XRD and XPS Characterization As Figure 3 shown in (a) - (e) therein, the XRD and XPS results confirmed the existence of elements such as Mn, Co, and Si in the HSMnCo sample, analyzed that the main component of HSMnCo was CoMn2O4, and further indicated the successful synthesis of the bimetallic oxide in - situ grown on silicate in HSMnCo.

[0027] 3. Specific Surface Area Figure 3 (f) therein shows the N2 adsorption - desorption isotherms of three materials, HSMn, HSCo, and HSMnCo. It can be seen that these three materials are all H Ⅳ - type isotherms with obvious hysteresis loops. The calculated specific surface area of HSMnCo (212 m 2 / g) is much higher than those of HSMn and HSCo (57 m 2 / g and 108 m 2 / g respectively). A large specific surface area can effectively increase the active sites, thereby improving the performance of HSMnCo.

[0028] III. Application of Montmorillonite Electrode Materials Application Example 1 First, mix the HSMnCo, acetylene black, and PTFE prepared in Example 1 in a ratio of 8:1:1, press them into a thin film and load it on nickel foam as the working electrode. Then, using 6 M KOH as the electrolyte, select a graphite rod as the counter - electrode, and select Hg / HgO as the reference electrode to assemble a three - electrode supercapacitor.

[0029] Assemble the HS material, HSMn prepared in Comparative Example 1, and HSCo material prepared in Comparative Example 2 into the corresponding three - electrode supercapacitors using the above method respectively.

[0030] The performance test results of the three - electrode supercapacitors are as Figure 4 shown. In the CV curve at a scan rate of 5 mV / s, the closed area of the CV curve of the HSMnCo supercapacitor is significantly larger than those of the other three materials. And at a current density of 0.5 A / g, the specific capacitance of the HSMnCo supercapacitor is 1235 F / g, which is much larger than the specific capacitances of the HS (110 F / g), HSMn (392.4 F / g), and HSCo (653 F / g) supercapacitors.

[0031] Application Example 2 First, mix the HSMnCo, acetylene black, and PTFE prepared in Example 1 in a ratio of 8:1:1, press them into a thin film and load it on nickel foam as the positive electrode. Then, using 6 M KOH as the electrolyte and activated carbon as the negative electrode, assemble an asymmetric supercapacitor (HSMnCo / / AC) and test the two-electrode system. The test results are as Figure 5 shown. At a current density of 0.5 - 10 A / g, the specific capacitance of the HSMnCo / / AC system is 259 - 110 F / g. When the power density is 279.83 W / kg, the energy density reaches 43.53 Wh / kg (calculated from formulas (1), (2), and (3)). At a current density of 5 A / g, the capacitance retention rate reaches 84.2% after 5000 cycles.

[0032] Application Example 3 Using the HSMnCo prepared in Example 2 as the positive electrode, zinc foil as the negative electrode, and 2 M Zn(CF3SO3)2 as the electrolyte, assemble a zinc-ion supercapacitor.

[0033] Perform CV tests, GCD tests, and cyclic stability tests on the zinc-ion supercapacitor. The test results are as Figure 6 shown. At a scan rate of 5 - 100 mV, the CV curve shows no obvious deformation, and the voltage window of the GCD curve can reach 0 - 1.5 V. At current densities of 0.5, 1, 2, 3, 5, and 10 A / g, the specific capacitances of the zinc-ion supercapacitor are 568, 535, 494, 450, 400, and 340 F / g respectively, and the rate performance is 59.8%. At a current density of 5 A / g, the capacitance retention rate is 94.7% after 5000 cycles, and when the power density is 374.78 W / kg, the energy density reaches 177.50 Wh / kg (calculated from formulas (1), (2), and (3)).

[0034] C m =I·Δt / m·ΔV Formula (1) E = C m ·ΔV 2 / 7.2 Formula (2) P = 3600E / Δt Formula (3) where C m (F / g) is the specific capacitance, I(A) is the current, Δt(s) is the discharge time, ΔV(V) is the voltage range, m(g) is the mass of the active material, E(Wh / kg) is the energy density, and P(W / kg) is the power density.

[0035] Through material characterization and electrochemical tests, the present invention reveals the internal mechanism of the excellent performance of HSMnCo: 1. Manganese-cobalt synergistic effect: Electronic structure regulation: The d electrons of Co 2+ hybridize with the eg orbitals of Mn 3+ to form a continuous electron transport channel, reducing the charge transfer resistance (Rct) to 3.58 Ω; Redox enhancement: Mn 3+ + Co 3+ Mn 4+ + Co 2+ The coupled reaction provides an additional pseudocapacitance contribution, increasing the total capacity by about 40%; 2. Structure stability mechanism: Montmorillonite skeleton buffers volume change: SEM after 5000 cycles (as Figure 6 shown) shows that the coral-like structure remains intact without obvious cracks.

[0036] 3. Strong interfacial bonding: XPS detects the presence of Mn-O-Si (531.2 eV) and Co-O-Si (530.8 eV) bonds in HSMnCo, ensuring that the active material does not fall off.

[0037] 4. Ion transport optimization: Hierarchical pores shorten the diffusion path: EIS test shows that the impedance is only 12.5 Ω, indicating a significant increase in the ion diffusion rate; Surface capacitance contribution: At a scan rate of 50 mV / s, the capacitance control contribution reaches 19%, higher than that of traditional bulk materials (usually <10%).

[0038] 5. Interlayer confinement effect: The interlayer confinement effect controls the lattice size of the formed CoMn2O4 within 0.1 - 0.3 nm (as Figure 2 shown).

[0039] The above embodiments and diagrams do not limit the product form and style of the present invention. Any appropriate changes or modifications made by those of ordinary skill in the relevant technical field should be regarded as not departing from the patent scope of the present invention.

Claims

1. A preparation method of a montmorillonite composite electrode material loaded with manganese cobalt oxide, characterized in that: It includes the following steps: Step 1. Pretreatment of montmorillonite: First, disperse 3 - 5 g of montmorillonite in 150 mL of an acidic solution with a concentration of 1.5 - 2 mol / L, stir for 4 - 6 hours, and then perform ultrasonic treatment for 30 minutes to remove impurities between the montmorillonite layers and activate the surface of the montmorillonite; Step 2. Hydrothermal reaction: Then transfer the pretreated montmorillonite to a reaction kettle and carry out a hydrothermal reaction at 160 - 200 °C for 10 - 12 hours to promote the expansion of the layer spacing of the montmorillonite under a high - temperature and high - pressure environment; Step 3. High - temperature calcination: Then transfer the montmorillonite that has undergone the hydrothermal reaction to a tubular furnace and calcine it at 800 - 900 °C for 2 - 3 hours to obtain activated montmorillonite, denoted as HS; Step 4. Preparation of the precursor solution: Then, 2 mmol of ammonium salt, 2 mmol of divalent manganese salt, and 2 - 6 mmol of divalent cobalt salt are dissolved in 120 - 150 mL of deionized water, and the Mn 2+ / Co 2+ molar ratio is controlled to be 1:1 - 1:3 to obtain a precursor solution; Step 5. Loading of manganese - cobalt metal oxide: Then add 0.2 g of HS to 120 - 150 mL of the precursor solution, stir for 4 - 6 hours, then carry out a hydrothermal reaction at 160 - 180 °C for 10 - 12 hours, centrifuge to collect the product, wash it 2 - 3 times with ethanol and deionized water, and finally dry it at 50 - 70 °C for 12 - 24 hours to obtain the montmorillonite composite electrode material loaded with manganese - cobalt oxide, denoted as HSMnCo; In Step 4, the ammonium salt is NH4Cl or NH4NO3, the divalent manganese salt is Mn(Ac)2·4H2O or Mn(NO3)2·4H2O, and the divalent cobalt salt is Co(Ac)2·4H2O or Co(NO3)2·4H2O.

2. The preparation method of a montmorillonite composite electrode material based on manganese cobalt oxide loading according to claim 1, characterized in that: In Step 1, the acidic solution is HCl solution, HNO3 solution or H2SO3 solution.

3. The preparation method of a montmorillonite composite electrode material based on manganese cobalt oxide loading according to claim 1, characterized in that: The specific surface area of the montmorillonite composite electrode material based on manganese cobalt oxide loading is 200~250 m 2 / g, and the pore size is 5~10 nm.

4. Application of a montmorillonite composite electrode material based on manganese cobalt oxide loading as described in claim 1, characterized in that: An asymmetric supercapacitor is assembled with HSMnCo as the positive electrode, activated carbon as the negative electrode, and KOH as the electrolyte.

5. The application of a montmorillonite composite electrode material based on manganese cobalt oxide loading according to claim 4, wherein: At a current density of 0.5 - 10 A / g, the energy density of the asymmetric supercapacitor is ≥25 Wh / kg, the power density is ≥270 W / kg, and the capacity retention rate is ≥80% after 5000 cycles.

6. Application of a montmorillonite composite electrode material based on manganese cobalt oxide loading as described in claim 1, characterized in that: A zinc - ion supercapacitor is assembled with HSMnCo as the positive electrode, zinc foil as the negative electrode, and Zn(CF3SO3)2 as the electrolyte.

7. The application of a montmorillonite composite electrode material based on manganese cobalt oxide loading according to claim 6, characterized in that: At a current density of 0.5 - 10 A / g, the energy density of the zinc - ion supercapacitor is ≥25 Wh / kg, the power density is ≥350 W / kg, and the capacity retention rate is ≥90% after 5000 cycles.

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