Conductive and redox-active metallopolymers towards high-performance supercapacitor electrodes

Abstract

Supercapacitors are a new emerging category of electrochemical energy storage technologies which exhibit balanced performances and bridge the energy and power gap between the batteries and conventional capacitors. Compared to the traditional supercapacitor electrode materials based on the non-metallic conductive polymers and the other low-conductivity metal-organic compounds, the conductive metallopolymers with redox-active metallic moieties could exhibit better capacitive performances. Since the potentials of such promising supercapacitor electrode materials are barely explored, research works in this thesis were aimed at developing high-performance supercapacitor electrode materials based on redox­active conductive metallopolymers, as well as studying the relationship between the molecular structures and the electrochemical energy storage performances. In Chapter 1, the backgrounds of energy storage technologies and the mechanisms of energy storage in supercapacitors will be briefly discussed, and possible advantages as well as design principles of conductive metallopolymers will be introduced. In Chapter 2, a ferrocene-based conductive metallopolymer was studied in comparison with the non-metallic conductive metallopolymer that shared a similar structure, and our findings showed that the introduction of the ferrocenyl moieties as additional redox sites could be beneficial to the capacitive performances. In Chapter 3, two ferrocenyl-functionalized triphenylamine-based conductive metallopolymers, with and without the hexyl groups, were designed and prepared. Electrochemical studies on them revealed that the hexyl groups in one metallopolymer should have great effects on the high rate capability. In Chapter 4, supercapacitor electrodes and devices based on one metal-free porphyrin-based conductive polymer and four metalloporphyrin-based conductive metallopolymers were prepared. Comparison on their various electrochemical properties as well as energy storage performances showed that different central atoms in the porphyrin rings had different effects on the charge storage kinetics. In the research works above, some as-fabricated all-solid-state supercapacitor devices showed superior performances such as high areal capacitances and good cycling stability. Several supercapacitor devices based on the metallopolymer-based electrode materials mentioned above were able to act as flexible and portable power sources in designed circuits.