Browsing by Author "Almofleh, Atheel Awad"

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Synthesis, characterization, and application of redox active electrolytes for high performance flexible supercapacitors
(2021) Almofleh, Atheel Awad; بوزكورت، ايهان; سيفيك، ايميري
Over the recent years, there has been a significant advancement in the energy storage systems with improved energy storage capacity and cyclic stability. Amongst these systems, supercapacitors have outstanding characteristics that include fast charge/ discharge, long cycle life, environmental compatibility and high-power density. Many techniques for enhancing the performance of supercapacitors have been reliant on the materials to manage the storage mechanism exploits. They include pseudocapacitance and the EDL (Electrical Double Layer Capacitance). In these instances, an electrolyte is expected to be electrochemically inert to allow for the achievement of full potential capacity. The EDL capacitance is as a result of ionic and electronic separation at the interface of the electrolyte. Contrastingly, pseudocapacitance charges have been widely linked to the faradaic procedures (redox processes), which occurs at the surface of electrodes. According to Frackowiak [135] an electrolyte's surface total charge is correspondent to the surface area electrochemically available on the electrode. Consequently, only well-developed properties of materials, can offer effective performance as electrolyte on the devices. The production of novel electrolytes with high ionic conductivity and improved chemical and electrochemical stability for assembling supercapacitors is a challenge but it has both practical and scientific significance. It has been confirmed that application of redox electrolytes improves the capacity of charge storage within supercapacitors. However, this performance is noted by the consideration of redox electrolyte contribution, which can the increase in the charge capacity. The specific capacitance is enhanced by rise quick faradaic reactions of electrodes using redox mediator electrolytes. The combination of the capacitance of the SC with that provided by the redox reaction of the electrolyte will lead to an increase in overall capacitance. This concept is demonstrated by showing the effects of adding an electrochemically active compound, Co, to polymer-gel electrolyte (GlyP5) This work includes the construction of flexible supercapacitors using a new electrolyte comprising a biobased host material and H3PO4/Co as guest additives. The gel electrolytes were produced in various contents of H3PO4 and Co in the host materials to get a series of electrolytes to evaluate both EDL and redox contributions in assembled devices. The performances of the devices were examined by galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The specific capacitance (Cs) of the supercapacitor device comprising active carbon (AC) composite electrode and gel electrolytes were measured. The energy density, power density and cyclic robustness of the device were evaluated. Flexible supercapacitors were assembled by using carbon composite electrodes and the bio-electrolytes; GlyPCoX (X: 1, 3, 5, 10). The electrolyte, GlyP5Co5 was proposed as the optimum composition which contributes for both EDL formation as well as redox reaction at the interface during GCD processes. The specific capacitance of the as-assembled system is 349 Fg-1 after inserting Co which is more than two-fold enhancement compared to GlyP5. The supercapacitor has excellent cyclic stability with excellent capacitance retention of 15.000 cycles. Furthermore, a single supercapacitor has superior flexibility under bent and twist conditions without performance alteration. This novel system can deliver a high specific energy of 47 Wh kg-1 at the corresponding specific power of 420 W kg-1. This system may pave to environmental benign, low-cost and long-term application of supercapacitors in flexible electronics.
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