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Design and Fabrication of Flexible Fiber- Shaped Hybrid Micro- Supercapacitors Based on Carbon Nanostructures and Oxides, Sulfides and Phosphides of Some Transition Metals

Naderi, Leila | 2020

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53242 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Shahrokhian, Saeed
  7. Abstract:
  8. Miniaturization of electronic devices with portable, flexible and wearable characteristics created a great demand for high-performance microscale energy storage devices with lightweight and flexible properties. Among the energy storage devices, wire-shaped micro-supercapacitors have recently received tremendous attention due to their small size, lightweght, and high flexibility. In the first part, the porous dendritic Ni-Cu film was prepared on Cu wire substrate (CW) for fabrication of high- performance wire-type micro-supercapacitors (micro-SCs). The porous structure with dendritic morphology provides a high surface area, short ion diffusion pathway and low contact resistance between electroactive materials and metal wire electrode. The Ni(OH)2 electroactive material is then deposited on Ni−Cu/CW electrode. The fabricated Ni(OH)2/Ni−Cu/CW electrode exhibits excellent electrochemical performances with high areal (volumetric) specific capacitance of 12.2 F cm-2 (1220.89 F cm-3), respectively at a current density of 4 mA cm-2, and an excellent cycle stability (100% even after 3500 cycles). A novel fiber-shaped flexible asymmetric micro-supercapacitor (FSAMSCs) based on Ni(OH)2/Ni−Cu/CW as positive electrode and reduced graphene oxide/carbon fiber (RGO/CF) as the binder free negative electrode was assembled. This device can be operated reversibly in the voltage range of 0−1.6 V and exhibited a maximum energy (195 μWh cm-2, 15 mWh cm-3) and power (7643 μW cm-2, 588 mW cm-3) densities. In addition, the FSAMSCs also exhibits an excellent cycling stability with 95.7% capacitance retention after 5000 cycles and good mechanical stability, which is checked by bending of the whole device at various angles.In the second part, NiMoO4/Ni/CW nanorods are successfully fabricated thorough direct deposition of Ni film onto Cu wire as the conductive substrate, followed by growth of the NiMoO4 nanorods on Ni film coated Cu wire substrate by means a hydrothermal annealing process. The prepared 3D, porous electrode demonstrates extremely high areal specific capacitance of 12.03 F cm-2 at the current density of 4 mA cm-2 and retained capacitance of 8.23 F cm-2 at a much higher current density of 80 mA cm-2. The electrode, also, shows an excellent cycling stability with capacitance retention of 99.3% after 3000 cycles. The superior electrochemical performance can be attributed to the high area surface, low contact resistance between NiMoO4 nanorods and Cu wire current collector and presence of a 3D and porous structure provides many electroactive sites and sufficient open space for easy diffusion of the electrolyte ions during redox reactions. Benefiting from their structural features, a FSAMSCs based on NiMoO4/Ni film/Cu wire and RGO/CF is assembled. The fabricated fiber device presents a wide potential window between 0 and 1.7 V and exhibits high energy density of 202 mWh cm-2 (15.6 mWh cm-3) and power density of 13530 mWcm-2 (1040.73 mW cm-3). In addition, the asymmetric device exhibits an outstanding cycling stability (98.5% capacitance retention after 1000 consecutive cycles) and good mechanical stability. In the third part, FSAMSCs was prepared based on CoNi2S4/E-NiZnP film@CW electrode. The etched NiZnP (E-NiZnP) film was synthesized by directly deposition of NiZnP film on Cu wire, followed by a chemical etching process. Alkaline etching treatment provides a micro- and mesoporous structure with high surface area and facilitates the penetration of electrolyte ions into the electrode matrix. Then, CoNi2S4 nanosheets as electroactive material are electrochemically grown onto the E-NiZnP film@CW electrode under a constant potential. The synergistic effects contributed by various components inside the CoNi2S4/E-NiZnP@CW electrode deliver superior performances with a high specific capacitance of 8.9 F cm-2, and 889.68 F cm-3 at 4 mA cm-2, outstanding rate capability and long-term cycling stability (93.4% capacitance retention after 7000 cycles). Moreover, FSAMSCs is fabricated using CoNi2S4/E-NiZnP film @CW as the positive electrode and RGO/CF as the negative electrode. The fabricated device exhibits good mechanical stability with a maximum energy (108.4 μWh cm-2 and 8.34 mWh cm-3), and power densities (9280 μW cm-2 and 716.9 mW cm-3). In the fourth part, NiVS/NiCuP nanostructures were prepared on Cu wire for high performance micro-SCs applications. The 3D NiCuP dendritic film was firstly deposited on Cu wire through the electrodeposition method, which not only act as a scaffold for deposition of the electroactive materials (NiV-LDH and NiV-S), but also served as a micro-porous current collector, supplied extra capacitances. Then, NiV-LDH nanosheets grown on 3D NiCuP film were obtained using a hydrothermal method. The sulfidation of NiV-LDH is carried out through an ion-exchange reaction of OH– with S2– to obtain NiVS, which maintains an ultrathin and porous structure, improves the electrical conductivity and reduces the diffusion resistance of the electrode. The as-prepared c-NiVS/NiCuP/CW electrode exhibits outstanding specific capacitance (13.4 F cm-2, 1342.28 F cm-3 at a current density of 4 mA cm-2) compared with the pristine NiV-LDH and NiVS directly growing on Cu wire in the absence of 3D NiCuP film. For further evaluation, NiVS nanoparticles synthesis by electrochemical deposition on NiCuP @Cu wire substrate under constant potential. The prepared electrode exhibited high specific capacitance (8.08 F cm-2, and 808.36 F cm-3 at current density of 4 mA cm–2) relative to e–NiVS @CW electrode. Finally, a solid state FSAMSCs is fabricated using c-NiVS/NiCuP/CW as the positive electrode and RGO/CF as the negative electrode. The assembled FSAMSCs device has a maximum operational voltage of 1.8 V and presented a high energy density of 295 μWh cm-2 (22.7 mWh cm-3) at a power density of 4.3 mW cm-2 (330.7 mW cm-3) with an excellent cycling stability (91.5% of its initial specific capacitance after 3000 cycles) and good mechanical stability. In the last section, ternary binder-free nanocomposite of MnO2/PEDOT:PSS-rGO was prepared on carbon fiber substrate for application in high performance FSAMSCs. The synergistic effects of the different components in the fiber- shaped electrode deliver a high specific capacitance of 2.92 F cm-2 (194.25 F cm-3) at a current density of 5 mA cm-2, and a long cycle life with 95% capacitance retention after 5000 cycles in 1 M Na2SO4 electrolyte. A FSAMSCs based on the resulting hybrid electrode was assembled. The maximum energy density of 295 µWh cm-2 (19 mWh cm-3) and power density of 14100 µWcm-2 (930 mW cm-3) was achieved under an operating voltage window of 0- 2.0 V in solid- state Na2SO4-CMC electrolyte. Moreover, FSAMSCs was used in a super-concentrated water-in-salt electrolyte based on potassium acetate (27 m KOAC). Use of water-in-salt electrolyte enables the assembled asymmetric micro-device to be operated up to a cell voltage of 2.8 V, which exhibit higher energy density than activated micro-device in conventional dilute aqueous electrolyte and is promising for applications where energy density is critical
  9. Keywords:
  10. Transition Metal Oxides ; Carbon Fibers ; Carbon/Metal/Polymer Nanostructures ; Three Dimensional Porous Films ; Flexible Asymmetric Micro-Supercapacitor ; Fiber Shaped Electrode ; Metal Wire Current Collector ; Transition Metal Oxide/Sulfide/Phosphide ; Three Dimensional Porous Films

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