2 - Renewable cathode materials dependent on conjugated polymer composite systems

Abstract

Capacity retention and stable interfaces are prime issues of cathode active materials. Conventional cathode materials exhibit lower reversible capacity and poor cyclability, which are primarily due to large volume variation, irreversible phase transitions, and degradations during cycling process. Conjugated conducting polymer and its composite expand their functionalities to sustain cycle life and redox activity of electrolyte. Charge storage devices are composed of anode, electrolyte, and counter electrode (cathode) to be functional over normal environmental condition. The chain of continuous charge transmission required tuning of work functions at the interfaces of layered design. The cathode plays a vital role to reduce the oxidized electrolyte through minimizing potential barrier at the electrolyte/cathode interface. The conjugated polymer is consisted of planar surface enriched with high electron density. The highest occupied molecular orbital and lowest occupied molecular orbital are tailored through polymer backbone or chemical side chain. The electron donating or electron rich polar groups either with ring or chain of polymer exhibited interaction center for electrolyte. The transport diffusion length was reduced for effective charge transport. Low redox potentials create a driving force to diffuse the electrolyte ion and low activation energy of chain reorients its surface to be recycled. The unique conductive properties can be tuned by preparing composite with common conjugated carbonaceous materials. Energy density and cycle life can be improved by using composite cathode materials. Interfacial property can be improved to reduce recombination loss that leads to enhance photovoltaic performance. The barriers to hole injection by the electrolyte can be improved. The cathode works as ionic as well as electronic conductor. Conjugated surface synchronizes electroactivity of cathode active content via continuous electron transfer into polymer chain. The electrode discharge capacity is expressed as a function of cycle number and varies with C-rates. Porosity decides rate capability of electrode. The porous nanoarchitecture improves diffusion kinetics of redox-active ions to facilitate higher flux of electrolyte percolation through microspores. The redox-active functional groups provide the active sites on conjugated surface for the redox reaction. Capacity retention can be improved by enhancing electrical conductivity of cathode active component.