Mo-Fe co-doped MnO2 / Ag-CNTs composite electrode and preparation method and application thereof

Abstract

The invention belongs to the technical field of preparation of new energy materials and supercapacitors, and particularly relates to a Mo-Fe co-doped MnO2 / Ag-CNTs composite electrode and a preparation method and application thereof. The method comprises the following steps: firstly, preparing an activated carbon cloth substrate, a deposition solution A and a deposition solution B; then the deposition solution A and the deposition solution B are mixed to obtain a Mo-Fe-MnO2 deposition solution, and an Ag-CNTs deposition solution is prepared; and finally, electro-deposition is alternately carried out in the Mo-Fe-MnO2 deposition solution and the Ag-CNTs deposition solution, and the Ag-CNTs / Mo-Fe-MnO2 / Ag-CNTs composite material is obtained. The preparation process provided by the invention is simple and controllable, and the large-scale preparation of the high-performance composite electrode is easy. The electrode is unique in structure and excellent in performance, and a flexible solid-state PSCSC device assembled by the electrode has high energy storage density and efficient mechanical energy self-charging capacity and shows huge application potential in the field of self-powered wearable / implantable microelectronics.

Description

Technical Field

[0001] This application belongs to the field of new energy materials and supercapacitor preparation technology, specifically relating to a Mo-Fe co-doped MnO2 / Ag-CNTs composite electrode, its preparation method and application. Background Technology

[0002] The rapid development of flexible wearable / implantable electronic devices has created an urgent need for miniaturized, high-energy-density, and sustainable power supply systems. Flexible solid-state supercapacitors are considered ideal micro-energy storage devices due to their high power density, fast charging and discharging, long cycle life, and safety and reliability. However, the energy density of existing supercapacitors still needs improvement, and their reliance on external power sources for periodic charging limits their application in continuous power supply scenarios.

[0003] Integrating energy harvesting (such as the piezoelectric effect) with energy storage into a single device to construct a piezoelectric self-charging supercapacitor (PSCSC) is an effective way to achieve spontaneous collection and storage of mechanical energy. In PSCSCs, the performance of the cathode material directly determines the energy storage capacity and overall efficiency of the device. Manganese dioxide (MnO2) is a highly promising cathode material due to its high theoretical specific capacitance, environmental friendliness, and low cost. However, MnO2 has low intrinsic conductivity, resulting in low utilization of active sites and slow ion transport kinetics under high active material loading, leading to an actual specific capacitance far lower than the theoretical value, which severely restricts its application in high-performance PSCSCs.

[0004] Therefore, how to achieve uniform and tight composite of active materials and conductive networks at the nanoscale under high loading through a simple and controllable process, avoiding interfacial resistance, and maximizing the electrochemical active area and ion transport efficiency of the material, remains a technical challenge in this field. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies, specifically overcoming the defects of poor conductivity, slow ion transport, and low specific capacitance of MnO2-based electrode materials under high loading. This invention provides a Mo-Fe co-doped MnO2 / Ag-CNTs composite electrode, its preparation method, and its applications. The specific technical solution adopted is as follows: In a first aspect, the present invention provides a method for preparing a Mo-Fe co-doped MnO2 / Ag-CNTs composite electrode, comprising the following steps: The carbon cloth was activated by acid treatment in concentrated nitric acid to obtain an activated carbon cloth substrate. MnC4H6O4·4H2O, Na2SO4 and (NH4)2Fe(SO4)2·6H2O were dissolved in water to obtain sediment A; Na2MoO4·2H2O was dissolved in H2SO4 solution to obtain sediment solution B; The deposition solution A and deposition solution B are mixed to obtain a Mo-Fe-MnO2 deposition solution; The dispersant TNWDIS, carbon nanotubes, potassium carbonate and potassium iodide were dissolved in water in sequence to obtain a black suspension; Silver nitrate was added to the black suspension under light-protected conditions until it was completely dissolved to obtain an Ag-CNTs deposition solution. A three-electrode system was adopted, with the carbon cloth substrate as the working electrode. Under constant current conditions, electrodeposition was carried out alternately in the Mo-Fe-MnO2 deposition solution and the Ag-CNTs deposition solution to obtain the Mo-Fe co-doped MnO2 / Ag-CNTs composite electrode.

[0006] As a further preferred embodiment, the atomic ratio of Mn, Mo and Fe in the Mo-Fe-MnO2 deposition solution is 210:30:1-5.

[0007] As a further preferred embodiment, the atomic ratio of Mn, Mo and Fe in the Mo-Fe-MnO2 deposition solution is 210:30:2.

[0008] This invention introduces beneficial structural defects (such as Mn) by using appropriate amounts of Fe doping. 3+ The addition of oxygen vacancies optimizes the electronic structure and ion transport path, reduces charge transfer impedance, and thus improves redox reaction kinetics; however, excessive doping causes severe lattice distortion and may generate impurity phases, which hinders ion transport and reduces active sites, resulting in poor energy storage performance.

[0009] As a further preferred embodiment, the mass ratio of the carbon dispersant TNWDIS to the nanotubes is 0.3-1.2:1; The concentration ratio of iodine ions to silver ions in the Ag-CNTs deposition solution is 200-500:1.

[0010] As a further preferred embodiment, the specific process of alternating electrodeposition in the Mo-Fe-MnO2 deposition solution and the Ag-CNTs deposition solution is as follows: Using a carbon cloth substrate as the working electrode, a saturated calomel electrode as the reference electrode, and a carbon rod as the counter electrode, the electrode was alternately deposited anoly in a Mo-Fe-MnO2 deposition solution for 8 min-15 min and cathodically in the Ag-CNTs deposition solution for 1 min-3 min. The number of anodic depositions is 3-6 times, and the number of cathodic depositions is 2-5 times.

[0011] As a further preferred embodiment, the current density during electrodeposition is 1-3 mA / cm². 2 The deposition temperature is 60℃-80℃.

[0012] Secondly, the present invention provides a Mo-Fe co-doped MnO2 / Ag-CNTs composite electrode, which is prepared by the preparation method described above.

[0013] The electrode provided by the present invention is uniformly composited with Mo and Fe co-doped α-MnO2 and Ag-CNTs conductive network, forming a flower-like nanostructure. Mo, Fe, Mn, Ag, C and O elements are uniformly distributed in the thickness direction of the electrode, forming a homogeneous composite film without internal interfaces.

[0014] Thirdly, the present invention provides a flexible solid-state piezoelectric self-charging asymmetric supercapacitor, comprising a positive electrode, a negative electrode, a gel electrolyte located between the positive and negative electrodes, and a flexible encapsulation layer; The positive electrode is the aforementioned Mo-Fe co-doped MnO2 / Ag-CNTs composite electrode.

[0015] As a further preferred embodiment, the negative electrode is activated carbon cloth; the gel electrolyte is sodium carboxymethyl cellulose / sodium sulfate gel doped with BaTiO3 particles.

[0016] Fourthly, the present invention provides the application of the above-mentioned flexible solid-state piezoelectric self-charging asymmetric supercapacitor in wearable electronic devices, implantable medical devices, or self-powered microsystems.

[0017] The beneficial effects of this invention are as follows: (1) The preparation process provided by the present invention is simple and controllable. The cyclic electrodeposition method is carried out under mild conditions. The process is simple, has good repeatability, and is easy to prepare high-performance composite electrodes on a large scale.

[0018] (2) This invention achieves a uniform and compact composite of Mo and Fe co-doped MnO2 and Ag-CNTs conductive networks at the nanoscale through a cyclic electrodeposition strategy, forming a homogeneous structure without internal interfaces. This structure maximizes the conductive contact interface and provides a highly efficient electron / ion transport channel.

[0019] (3) The composite electrode prepared by this invention has a unique structure and excellent performance, at 3.6 mg / cm 2Under high loads, it exhibits extremely high specific capacitance (up to 401.2 F / g at a current density of 0.25 A / g) and excellent rate performance (specific capacitance still reaches 222.5 F / g at a high current density of 20 A / g). In addition, the electrode provided by this invention has excellent cycle stability, which is mainly due to the uniform stress distribution and stable conductive network brought about by the homogeneous composite structure. After 18,000 charge-discharge cycles, the composite electrode retains a capacitance of up to 98.6%, demonstrating an ultra-long cycle life.

[0020] (4) The composite electrode provided by this invention is a flexible solid-state asymmetric supercapacitor assembled with a positive electrode, which achieves a high efficiency of 58.8 μWh / cm² at a working voltage of 2.2 V. 2 The area energy density (power density 27.5 mW / cm²) 2 It outperforms most reported MnO2-based devices.

[0021] (5) The PSCSC device with integrated BaTiO3 piezoelectric electrolyte provided by the present invention can achieve a self-charging voltage of up to 457 mV under an external force of about 20 N, demonstrating its practical application capability of converting environmental mechanical energy into electrical energy and storing it. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The X-ray diffraction patterns of various electrode materials prepared in Example 1 and Comparative Examples 1-4 of this invention are shown.

[0024] Figure 2 The images shown are scanning electron microscope (SEM) images of the surface and cross-section of the Mo-Fe-MnO2 / Ag-CNTs composite electrode prepared in Example 1 of this invention, along with the corresponding energy dispersive spectral lines. In the images, (a) shows the flower-like morphology of the composite electrode surface, (b) shows the cross-sectional morphology, and (c) shows the cross-sectional energy dispersive spectral lines.

[0025] Figure 3 The image shown is a high-resolution transmission electron micrograph of the Mo-Fe-MnO2 / Ag-CNTs composite electrode prepared in Example 1 of this invention.

[0026] Figure 4The figure shows the electrochemical performance of the Mo-Fe-MnO2 / Ag-CNTs composite electrode prepared in Example 1 of the present invention in 0.5 mol / L Na2SO4 electrolyte; where (a) is the cyclic voltammetry curve, (b) is the constant current charge-discharge curve, (c) is the Nyquist plot, (d) is the specific capacitance, (e) is the long-cycle stability, and (f) is the Nyquist plot before and after cycling.

[0027] Figure 5 The figure shown is a comparison of the mass-to-capacitance ratio of Examples 1-3 and Comparative Examples 1-8.

[0028] Figure 6 The figure shows the electrochemical performance of the Mo-Fe-MnO2 / Ag-CNTs / / AC asymmetric supercapacitor device assembled in Example 5 of the present invention; where (a) is the cyclic voltammetry curve, (b) is the constant current charge-discharge curve, (c) is the areal specific capacitance, (d) is the Ragone plot, (e) is the long-cycle stability, and (f) is the Nyquist comparison plot before and after cycling.

[0029] Figure 7 The diagram shows the self-charging performance of the piezoelectric self-charging supercapacitor assembled in Embodiment 5 of the present invention; wherein, (a) is the self-charging voltage curve under different pressures (approximately 5-20 N), (b) is the curve of self-charging to 457 mV under approximately 20 N pressure and then discharging at a constant current of 1 mA, and (c) is the stability curve of five consecutive self-charging-discharging cycles under approximately 5 N pressure. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] Example 1 A method for preparing a Mo-Fe co-doped MnO2 / Ag-CNTs composite electrode, specifically comprising the following steps: S1. Substrate pretreatment: A piece of carbon cloth (1 cm × 2 cm) was placed in concentrated nitric acid and heated at 100°C for 4 hours. After removal, it was ultrasonically cleaned in 0.5 mol / L H2SO4 solution, deionized water and ethanol for 30 minutes each, and then dried to obtain activated carbon cloth (AC) substrate.

[0032] S2. Prepare the sedimentation solution, the specific process is as follows: (1) Fe-doped MnO2 deposition solution A: 5.14689 g MnC4H6O4·4H2O, 7.102 g Na2SO4 and 0.07843 g (NH4)2Fe(SO4)2·6H2O were added sequentially and dissolved in 300 mL of deionized water.

[0033] (2) Molybdenum source solution B: Dissolve 0.72585 g Na2MoO4·2H2O in 10 mL of 0.5 mol / L H2SO4 solution and sonicate at room temperature for 2 minutes until completely dissolved.

[0034] (3) Mix Fe-doped MnO2 deposition solution A with molybdenum source solution B and sonicate at room temperature for 2 minutes to make it uniform. Finally, add deionized water to make up to 1000 mL to obtain the final Mo-Fe-MnO2 deposition solution (where the atomic ratio of Mn, Mo and Fe is 210:30:2).

[0035] (4) Ag-CNTs deposition solution: a. Add 100 mL of deionized water to a 250 mL beaker A, then add 0.15 g of dispersant (TNWDIS) and stir magnetically (300 rpm) for 10 minutes at room temperature until completely dissolved. Then add 0.25 g of carbon nanotubes (CNTs), first manually pre-stir with a glass rod to initially wet them, and then sonicate at room temperature for 20 minutes to completely disperse them, thus obtaining a primary dispersion of black carbon nanotubes. b. Add 200 mL of deionized water to another 500 mL beaker B, then add 1.0 g of potassium carbonate (K2CO3) and 25.0 g of potassium iodide (KI) in sequence, and stir until completely dissolved to obtain a clear alkaline iodide solution; c. Transfer all the primary dispersion of black carbon nanotubes prepared in beaker A to beaker B. Wash beaker A several times with 50 mL of deionized water and pour the washing solution into beaker B to ensure complete transfer of carbon nanotubes. Then sonicate for 10 minutes to mix the system thoroughly and evenly to obtain a uniform black suspension.

[0036] d. Wrap beaker B with aluminum foil and slowly add 0.10 g of silver nitrate (AgNO3) to beaker B under light-protected conditions. Sonicate to dissolve for 5 minutes, ensuring that the solution remains uniformly black throughout the process without any yellow turbidity or precipitation. After dissolution, transfer all the liquid in beaker B to a 500 mL brown volumetric flask, add deionized water to bring the volume to 500 mL, and continue stirring for 30 minutes under light-protected conditions to finally obtain the Ag-CNTs composite deposition solution.

[0037] S3. Cyclic Electrodeposition: A three-electrode system was used, with an AC substrate as the working electrode, a saturated calomel electrode (SCE) as the reference electrode, and a carbon rod as the counter electrode. Electrodeposition was carried out in a 70°C constant-temperature water bath with magnetic stirring at 125 rpm at a rate of 2 mA / cm². 2 Electrodeposition is performed using a constant current density. The deposition process is as follows: (i) Anodic deposition in Mo-Fe-MnO2 deposition solution for 13 minutes.

[0038] (ii) Cathodic deposition in Ag-CNTs deposition solution for 2 minutes.

[0039] Steps (i) and (ii) were repeated alternately; the final electrodeposition sequence consisted of four Mo-Fe-MnO2 depositions and three Ag-CNT depositions. After deposition, the electrode was rinsed with deionized water and dried to obtain a Mo-Fe-MnO2 / Ag-CNTs composite electrode loaded on an AC substrate; the loading of active material (Mo-Fe-MnO2 / Ag-CNTs) was approximately 3.6 mg / cm³. 2 .

[0040] Example 2 A method for preparing a Mo-Fe co-doped MnO2 / Ag-CNTs composite electrode, specifically comprising the following steps: S1. Substrate pretreatment: Same as in Example 1.

[0041] S2. Prepare the sedimentation solution, the specific process is as follows: (1) Fe co-doped MnO2 deposition solution A: 5.14689 g MnC4H6O4·4H2O, 7.102 g Na2SO4 and 0.03922 g (NH4)2Fe(SO4)2·6H2O were added sequentially and dissolved in 300 mL of deionized water.

[0042] (2) Molybdenum source solution B: Dissolve 0.72585 g Na2MoO4·2H2O in 10 mL of 0.5 mol / L H2SO4 solution and sonicate at room temperature for 2 min until completely dissolved.

[0043] (3) Mix the Fe-doped MnO2 deposition solution A with the molybdenum source solution and sonicate at room temperature for 2 min to make it uniform. Finally, add deionized water to make up to 1000 mL to obtain the final Mo-Fe-MnO2 deposition solution (where the atomic ratio of Mn, Mo and Fe is 210:30:4).

[0044] (4) Ag-CNTs deposition solution: Same as in Example 1.

[0045] S3, Cyclic electrodeposition: Same as Example 1.

[0046] Example 3 A method for preparing a Mo-Fe co-doped MnO2 / Ag-CNTs composite electrode, specifically comprising the following steps: S1. Substrate pretreatment: Same as in Example 1.

[0047] S2. Prepare the sedimentation solution, as in Example 1.

[0048] S3. Cyclic Electrodeposition: A three-electrode system was used, with an AC substrate as the working electrode, a saturated calomel electrode (SCE) as the reference electrode, and a carbon rod as the counter electrode. Electrodeposition was carried out in a 70°C constant-temperature water bath with magnetic stirring at 125 rpm at a rate of 2 mA / cm². 2 Electrodeposition is performed using a constant current density. The deposition process is as follows: (i) Anodic deposition in Mo-Fe-MnO2 deposition solution for 10 minutes.

[0049] (ii) Cathodic deposition in Ag-CNTs deposition solution for 1 minute.

[0050] Steps (i) and (ii) were repeated alternately; the final electrodeposition sequence consisted of 6 Mo-Fe-MnO2 depositions and 5 Ag-CNTs depositions. After deposition, the electrode was rinsed with deionized water and dried to obtain a Mo-Fe-MnO2 / Ag-CNTs composite electrode loaded on an AC substrate.

[0051] Comparative Example 1 A method for preparing a pure MnO2 electrode is described, the preparation process of which is similar to that of Example 1. The difference is that in step S2, the deposition solution does not contain Mo source, Fe source, AgNO3, or CNTs, but only MnC4H6O4·4H2O and Na2SO4. Specifically, 5.14689 g of MnC4H6O4·4H2O and 7.102 g of Na2SO4 are dissolved in 300 mL of deionized water to obtain the MnO2 deposition solution. A three-electrode system is used, with an AC substrate as the working electrode, an SCE as the reference electrode, and a carbon rod as the counter electrode.

[0052] Under constant temperature water bath of 70℃ and magnetic stirring at 125 rpm, at a speed of 2 mA / cm 2 A constant current density was used for anodic deposition in the MnO2 deposition solution for 80 minutes. After deposition, the electrode was rinsed with deionized water and dried to obtain a pure MnO2 electrode loaded on an AC substrate.

[0053] Comparative Example 2 A method for preparing a Mo-Fe-MnO2 electrode is similar to that in Example 1, except that in step S2, an Ag-CNTs deposition solution is not prepared, and the entire deposition process is carried out only in the Mo-Fe-MnO2 deposition solution for anodic deposition, while the other processes are the same.

[0054] Comparative Example 3 A method for preparing a Mo-Fe-MnO2 / Ag electrode is described. The specific preparation process is similar to that in Example 1, except that CNTs are not added to the Ag-CNTs deposition solution in step S2. All other processes are the same.

[0055] Comparative Example 4 A method for preparing a Mo-Fe-MnO2 / CNTs electrode is described. The specific preparation process is similar to that in Example 1, except that AgNO3 is not added to the Ag-CNTs deposition solution in step S2. All other processes are the same.

[0056] Comparative Example 5 A method for preparing a Mo-MnO2 / Ag-CNTs electrode is described. The specific preparation process is similar to that in Example 1, except that no Fe source is added to the Fe-doped MnO2 deposition solution in step S2. All other processes are the same.

[0057] Comparative Example 6 A method for preparing a Mo-Co-MnO2 / Ag-CNTs electrode is similar to that in Example 1, except that in step S2, 0.03922 g of (NH4)2Fe(SO4)2·6H2O is replaced with 0.29103 g of Co(NO3)2·6H2O in the Fe-doped MnO2 deposition solution, while the other processes are the same.

[0058] Comparative Example 7 A method for preparing a Ni-V-MnO2 / Ag-CNTs electrode is similar to that in Example 1, except that the deposition solution is prepared in S2 (without preparing Fe-doped MnO2 deposition solution A and molybdenum source solution B, the Ni-V-MnO2 deposition solution is prepared directly). The specific process is as follows: Take 500 mL of deionized water in a beaker, add 0.4739 g of NaVO3·2H2O, stir until dissolved, and slowly add 0.5 mol / L H2SO4 dropwise under stirring until the pH of the solution drops to between 3.5 and 4.0; then add 5.14689 g of MnC4H6O4·4H2O, 7.102 g of Na2SO4, and 0.2908 g of Ni(NO3)2·6H2O in sequence, adding the next salt only after each salt has completely dissolved. After complete dissolution, transfer the solution to 1000 mL of water. The volumetric flask was diluted to the mark with deionized water and shaken well to obtain the Ni-V-MnO2 precipitation solution. All other processes were the same.

[0059] Comparative Example 8 A method for preparing a Mo-Fe co-doped MnO2 / Ag-CNTs composite electrode, specifically comprising the following steps: S1. Substrate pretreatment: Same as in Example 1.

[0060] S2. Prepare the sedimentation solution, the specific process is as follows: (1) Fe co-doped MnO2 deposition solution A: 5.14689 g MnC4H6O4·4H2O, 7.102 g Na2SO4 and 0.03922 g (NH4)2Fe(SO4)2·6H2O were added sequentially and dissolved in 300 mL of deionized water.

[0061] (2) Molybdenum source solution B: Dissolve 0.72585 g Na2MoO4·2H2O in 10 mL of 0.5 mol / L H2SO4 solution and sonicate at room temperature for 2 min until completely dissolved.

[0062] (3) Mix the Fe-doped MnO2 deposition solution A with the molybdenum source solution and sonicate at room temperature for 2 min to make it uniform. Finally, add deionized water to make up to 1000 mL to obtain the final Mo-Fe-MnO2 deposition solution (where the atomic ratio of Mn, Mo and Fe is 210:30:10).

[0063] (4) Ag-CNTs deposition solution: Same as in Example 1.

[0064] S3, Cyclic electrodeposition: Same as Example 1.

[0065] Example 4 The preparation of gel piezoelectric electrolytes specifically includes the following steps: 0.5 g of sodium carboxymethyl cellulose (CMC) was added to 20 mL of a 1 mol / L Na₂SO₄ aqueous solution. The solution was heated in a 90 °C water bath and magnetically stirred continuously at a rate of 500-800 rpm until the CMC was completely dissolved, forming a uniform and transparent gel. After cooling to room temperature, 0.25 g of BaTiO₃ nanoparticles were added to the gel under continuous stirring. After stirring until homogeneous, a CMC / Na₂SO₄-BaTiO₃ gel piezoelectric electrolyte was obtained.

[0066] Example 5 Assembly of flexible solid-state asymmetric supercapacitors The Mo-Fe-MnO2 / Ag-CNTs electrode prepared in Example 1 was used as the positive electrode, and another piece of AC cloth of the same size was used as the negative electrode. Both electrodes were immersed in the gel piezoelectric electrolyte prepared in Example 4 to ensure complete wetting, and then stacked together. The stacked assembly was encapsulated with polyimide tape, and slight pressure was applied to remove excess air bubbles. After standing for 12 hours to allow the gel electrolyte to completely solidify, a flexible solid-state Mo-Fe-MnO2 / Ag-CNTs / / AC ASC device (denoted as PSCSC) was obtained.

[0067] The materials prepared in Examples 1-3, Example 5, and Comparative Examples 1-8 were characterized and their performance was measured (among which, the composite electrode prepared in Example 1 was subjected to SEM and TEM tests, Examples 1 and Comparative Examples 1-5 were subjected to XRD tests, and Examples 1-3, 5, and Comparative Examples 1-8 were subjected to electrochemical performance tests). The specific testing procedures are as follows: (1) The phase analysis of the prepared electrode materials was performed using a D8ADVANCE-A25 X-ray diffractometer. The target material was Cu, the scanning speed was 5° / min, and the scanning range was 20°-80°.

[0068] The results are shown in Figure 1 , Figure 1 Specifically, the XRD spectra of pure MnO2, Mo-Fe-MnO2, Mo-Fe-MnO2 / Ag, Mo-Fe-MnO2 / CNTs and Mo-Fe-MnO2 / Ag-CNTs show that all prepared materials are in the α-MnO2 phase, and no new phase is generated. Furthermore, the (400) crystal plane diffraction peak of MnO2 is slightly shifted to the right, confirming that Mo and Fe are successfully incorporated into the MnO2 lattice.

[0069] (2) The surface and cross-sectional morphology of the electrode were observed and analyzed using a scanning electron microscope.

[0070] The result is as follows Figure 2 and Figure 3 , Figure 2The images shown are scanning electron microscope (SEM) images of the surface and cross-section of the Mo-Fe-MnO2 / Ag-CNTs composite electrode prepared in Example 1 of this invention, along with the corresponding energy dispersive spectral lines. (a) shows the flower-like morphology of the composite electrode surface, (b) shows the cross-sectional morphology, and (c) shows the cross-sectional energy dispersive spectral lines. It can be seen that the Mn, Fe, Mo, Ag, and C components are uniformly composited along the electrode thickness direction, without any delamination interfaces.

[0071] Figure 3 The image shown is a high-resolution transmission electron micrograph of the Mo-Fe-MnO2 / Ag-CNTs composite electrode prepared in Example 1 of the present invention, which confirms that carbon nanotubes are composited into MnO2.

[0072] (3) The electrochemical performance tests of the electrodes were all conducted using a standard three-electrode system on the Shanghai Chenhua (CHI660E) electrochemical workstation. The prepared electrode was used as the working electrode, the saturated calomel electrode as the reference electrode, and the platinum electrode as the auxiliary electrode. The test solution was 0.5 mol / L Na2SO4 solution, and the working temperature was 25 ℃.

[0073] 1) The frequency range of the electrode AC impedance test is 0.01 - 100000 Hz, and the amplitude signal is 10 mV.

[0074] 2) The potential window for electrode cyclic voltammetry testing is 0 - 0.8 V, and the scan rate is 5 - 300 mV / s.

[0075] 3) The current densities for the electrode constant current charge-discharge (GCD) test were 0.25, 1, 2, 5, 10, and 20 A / g, with a potential window of 0 - 0.8 V. The mass specific capacitance of the electrode can be calculated using the following formula based on the GCD curve.

[0076] in, C (F / g) is the specific capacitance of the electrode. I (A / g) represents the charge / discharge current density. ΔU (V) represents the potential window of the electrode. m (g) represents the loading of the electrode active material. Δt (s) represents the discharge time.

[0077] 4) Electrode cycle stability testing was achieved by performing multiple GCD tests with a current density of 5 A / g, a potential window of 0 - 0.8 V, and 18,000 cycles.

[0078] (4) The electrochemical performance of the assembled supercapacitor device was tested using a Shanghai Chenhua (CHI660E) electrochemical workstation. The positive electrode of the device was connected to the working electrode, and the negative electrode of the device was connected to both the reference electrode and the auxiliary electrode. The test temperature was 25 °C.

[0079] 1) The frequency range for AC impedance testing of the device is 0.01 - 100000 Hz, and the amplitude signal is 10 mV.

[0080] 2) The potential window for cyclic voltammetry testing of the device is 0 - 2.2 V, and the scan rate is 5 - 100 mV / s.

[0081] 3) The current densities for GCD testing of the devices were 1.5, 2.5, 5, 10, and 25 mA / cm². 2 The process is performed under the following conditions, with a potential window of 0-2.2 V. The areal capacitance of the device can be calculated using the GCD curve.

[0082] 4) The current density for device cycle stability testing is 10 mA / cm². 2 The potential window is 0 - 2.2 V, and the number of cycles is 15,000.

[0083] 5) Device energy density ( E ) and power density ( P The value can be calculated using the following formula.

[0084] in, E (μmWh cm) -2 ) represents the energy density of the device. C (mF cm) -2 ( ) represents the areal capacitance of the device under different current densities. U (V) represents the potential window of the device. P (mW cm) -2 ) represents the power density of the device. Δt (s) represents the discharge time of the device at different current densities.

[0085] Table 1. Comparison of mass-to-capacitance ratio between the examples and comparative examples, in F / g The results are shown in Figures 4-7 And Table 1, Figure 4The figure shows the electrochemical performance of the Mo-Fe-MnO2 / Ag-CNTs composite electrode prepared in Example 1 of this invention in 0.5 mol / L Na2SO4 electrolyte; it can be seen that the cyclic voltammetry curves at different scan rates are all highly symmetrical. Figure 4 a) No obvious redox peaks appeared, indicating that the capacitance contribution of the composite electrode is the double-layer capacitance, and it has good reversibility; the constant current charge-discharge curves at different current densities did not show obvious voltage drops ( Figure 4 (b) indicates that the composite electrode possesses excellent specific capacitance and high transmission rate; Figure 4 The Nyquist plot of c shows its extremely low charge transfer resistance, exhibiting excellent conductivity; the composite electrode achieves a specific capacitance of 401.2 F / g at a current density of 0.25 A / g, and still maintains 222.5 F / g at a high current density of 20 A / g. Figure 4 d), excellent rate performance; after 18,000 cycles, the capacitance retention rate is still as high as 98.6% ( Figure 4 e), after cycling, the charge transfer resistance did not increase significantly ( Figure 4 f), demonstrating excellent stability.

[0086] Figure 5 The graphs show a comparison of the specific capacitance of Examples 1-3 and Comparative Examples 1-8. It can be seen that the introduction of metal ions such as Mo, Fe, Co, Ni, and V, as well as Ag or CNTs, can effectively improve the specific capacitance of the MnO2 electrode. The improvement effect of the examples is significantly better than that of the comparative examples. In particular, Example 1 still has a high specific capacitance at a high current density of 20 A / g.

[0087] Figure 6 The electrochemical performance diagrams of the Mo-Fe-MnO2 / Ag-CNTs / / AC asymmetric supercapacitor assembled in this invention are shown. The cyclic voltammetry curves of the assembled Mo-Fe-MnO2 / Ag-CNTs / / AC ASC device at different scan rates are all highly symmetrical. Figure 6 a), and the operating potential window is as high as 2.2 V; the constant current charge-discharge curves under different current densities do not show obvious voltage drop ( Figure 6 b) indicates that the device has a high transmission rate and excellent area-to-capacitance ratio. Figure 6 c) Figure 6 The display shows that the device achieved 93.9 μWh / cm². 2 High energy density (1.65 mW / cm³) 2 ) and 27.5 mW / cm 2 High power density (58.8 μWh / cm³) 2 After 15,000 cycles, the capacitance retention rate reached 98.7%. Figure 6e), the charge transfer resistance does not change much after cycling ( Figure 6 f), exhibiting excellent cycle stability.

[0088] Figure 7 The diagram shows the self-charging performance of the piezoelectric self-charging supercapacitor assembled in this invention. (a) shows the self-charging voltage curves under different pressures (approximately 5-20 N), (b) shows the curve of self-charging to 457 mV at approximately 20 N pressure followed by constant current discharge at 1 mA, and (c) shows the stability curve after five consecutive self-charge-discharge cycles at approximately 5 N pressure. It can be seen that under external pressure, the BaTiO3 piezoelectric electrolyte generates a piezoelectric potential, driving ion migration and redox reactions at the electrodes, thus achieving self-charging. At approximately 20 N pressure, the device's self-charging voltage can reach 457 mV (…). Figure 7 ab). This voltage can release energy through constant current discharge ( Figure 7 b). The device exhibits good stability during multiple self-charge-discharge cycles. Figure 7 c).

[0089] In summary, this invention successfully fabricates a high-performance electrode composed of Mo and Fe co-doped MnO2 and Ag-CNTs through an innovative cyclic electrodeposition strategy. This electrode exhibits a unique structure and superior performance. Flexible solid-state PSCSC devices assembled with this electrode possess both high energy storage density and efficient mechanical energy self-charging capability, demonstrating significant application potential in the field of self-powered wearable / implantable microelectronics.

[0090] The embodiments of this application have been described above with reference to the accompanying drawings. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the core ideas of this application. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A Mo-Fe co-doped MnO 2 / The method for preparing Ag-CNTs composite electrodes is characterized by, Includes the following steps: The carbon cloth was activated by acid treatment in concentrated nitric acid to obtain an activated carbon cloth substrate. MnC4H6O4·4H2O, Na2SO4 and (NH4)2Fe(SO4)2·6H2O were dissolved in water to obtain sediment A; Na2MoO4·2H2O was dissolved in H2SO4 solution to obtain sediment solution B; The deposition solution A and deposition solution B are mixed to obtain a Mo-Fe-MnO2 deposition solution; The dispersant TNWDIS, carbon nanotubes, potassium carbonate and potassium iodide were dissolved in water in sequence to obtain a black suspension; Silver nitrate was added to the black suspension under light-protected conditions until it was completely dissolved to obtain an Ag-CNTs deposition solution. A three-electrode system was adopted, with the carbon cloth substrate as the working electrode. Under constant current conditions, electrodeposition was carried out alternately in the Mo-Fe-MnO2 deposition solution and the Ag-CNTs deposition solution to obtain the Mo-Fe co-doped MnO2 / Ag-CNTs composite electrode.

2. The preparation method according to claim 1, characterized in that, The atomic ratio of Mn, Mo and Fe in the Mo-Fe-MnO2 deposition solution is 210:30:1-5.

3. The preparation method according to claim 2, characterized in that, The atomic ratio of Mn, Mo and Fe in the Mo-Fe-MnO2 deposition solution is 210:30:

2.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the carbon dispersant TNWDIS to the nanotubes is 0.3-1.2:1; The concentration ratio of iodine ions to silver ions in the Ag-CNTs deposition solution is 200-500:

1.

5. The preparation method according to claim 1, characterized in that, The specific process of alternating electrodeposition in the Mo-Fe-MnO2 deposition solution and the Ag-CNTs deposition solution is as follows: Using a carbon cloth substrate as the working electrode, a saturated calomel electrode as the reference electrode, and a carbon rod as the counter electrode, the electrode was alternately deposited anoly in a Mo-Fe-MnO2 deposition solution for 8 min-15 min and cathodically in the Ag-CNTs deposition solution for 1 min-3 min. The number of anodic depositions is 3-6 times, and the number of cathodic depositions is 2-5 times.

6. The preparation method according to claim 5, characterized in that, The current density during electrodeposition is 1-3 mA / cm². 2 The deposition temperature is 60℃-80℃.

7. A Mo-Fe co-doped MnO2 / Ag-CNTs composite electrode, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. A flexible solid-state piezoelectric self-charging asymmetric supercapacitor, characterized in that, Includes a positive electrode, a negative electrode, a gel electrolyte located between the positive and negative electrodes, and a flexible encapsulation layer; The positive electrode is the Mo-Fe co-doped MnO2 / Ag-CNTs composite electrode according to claim 7.

9. The flexible solid-state piezoelectric self-charging asymmetric supercapacitor according to claim 8, characterized in that, The negative electrode is activated carbon cloth; the gel electrolyte is sodium carboxymethyl cellulose / sodium sulfate gel doped with BaTiO3 particles; The flexible encapsulation layer is polyurethane, polyethylene terephthalate, or polyimide.

10. The application of the flexible solid-state piezoelectric self-charging asymmetric supercapacitor according to any one of claims 8-9 in wearable electronic devices, implantable medical devices, or self-powered microsystems.

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