Abstract
Depleting fossil fuel and increase in per capita energy demand pushes us to find better ways to manage and utilise the energy [1]. As a result, research into supercapacitors (SCs) has generated considerable interest due to their high-power density, fast charging/discharging rate, and high safety [2]. Yet, the energy output of standard aqueous SCs, notably electric double-layer capacitors, often falls short of meeting the needs of electronic devices. To address this challenge, hybrid supercapacitors were developed by merging high-energy density battery-type electrodes with high-power SCs electrodes. Considering the dynamics, performance, and safety factors, zinc ion-based devices have gained substantial attention due to the suitable redox potential of -0.76 V vs. the standard hydrogen electrode and an impressive theoretical capacity of 820 mAh g-1 (5855 mAh cm-3) for the zinc electrode [3]. So far, several carbon-based cathode materials have been extensively investigated for improving the energy density of zinc-ion capacitors (ZICs). However, the energy density achieved is not satisfactory compared to lithium-ion batteries due to low capacity and poor kinetics. So, efficient electrode materials that maximise cathodes' ability to store more zinc ions are required. In this aspect, biowaste-derived activated carbon (AC) and composite cathodes like pseudocapacitive organic molecules incorporated with carbon can be used for ZICs due to their easy structural design, controllable synthesis and environmental benignancy [4]. Activated carbon-based cathodes stores charge at the electrode/electrolyte interface, whereas the composite cathode not only stores charge at this interface but also provides added pseudo capacitance through rapid, reversible redox reactions from organic components, leading to significantly increased capacity and energy density.
This research colloquium will focus on bio-waste derived AC, composite (AC/redox-moieties) electrode materials, and electrolyte modifications to boost energy density and minimize self-discharge in ZICs. Additionally, machine learning methods such as random forest (RF) and multilayer perceptron neural network (MPNN) are implemented to predict capacitance and the associated physical parameters affecting capacitance. Also, the solid-state ZICs have been developed at the pouch cell level and their device performance are addressed at different working temperatures (-10 ℃ to 80 ℃).
References
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[2] A. Gonzalez, E. Goikolea, J.A. Barrena, R. Mysyk, Review on supercapacitors: Technologies and materials, Renew. Sustain. Energy Rev. 58 (2016) 1189–1206.
[3] A.A. Mohamad, Zn/gelled 6 M KOH/O2 zinc–air battery, J. Power Sources. 159 (2006) 752–757.
[4] S. Lee, G. Kwon, K. Ku, K. Yoon, S. Jung, H. Lim, K. Kang, Recent progress in organic electrodes for Li and Na rechargeable batteries, Adv. Mater. 30 (2018) 1704682.