Dissertation defence (Chemistry): MSc Ashwini Jadhav
MSc Ashwini Jadhav defends the dissertation in Chemistry titled “Redox-Mediated Aqueous Electrolytes for Enhanced Performance of Titanium Carbide MXene Supercapacitors” at the University of Turku on 30 October 2026 at 12.00 (University of Turku, Natura, Lecture Room X, Turku).
Opponent: Professor Robert Dryfe (University of Manchester, United Kingdom)
Custos: Professor Carita Kvarnström (University of Turku)
Summary of the Doctoral Dissertation:
As electricity becomes more central to everyday life, we need ways to store it efficiently and deliver it when needed. Batteries are a familiar example, but they are not the only option. Supercapacitors are another category of energy-storage devices that can store and release energy quickly and withstand repeated use. However, the amount of energy they can store remains a limitation.
A typical supercapacitor consists of two electrodes and an electrolyte that work together to store and release energy. In this work, we used a layered two-dimensional material called MXene as the electrode material. The spaces between MXene layers allow ions from the electrolyte to enter and contribute to charge storage. Although MXenes are a promising electrode material, they can gradually deteriorate during use, especially in water-based electrolytes, reducing charge-storage capacity. This research investigates how changing the electrolyte can improve both the charge-storage ability and durability of MXene-based supercapacitors. We tested three water-based electrolytes with varying salt concentrations consisting of dilute sulfuric acid and highly concentrated sodium- and zinc-based electrolytes, each with a small amount of iodide salt added to them. The iodine-containing salts participate in reversible chemical reactions and interact differently with each electrolyte. The key finding in the thesis was that adding iodine-containing salts to the electrolyte solution improves both charge storage and the cycling stability of the supercapacitor.
The results showed that the electrolyte choice strongly affected overall charge storage and the supercapacitor's charge-discharge stability after repeated use. With the iodine-containing additive, the zinc-based electrolyte enabled 100,000 charge-discharge cycles while retaining 80% of the initial charge storage capacity. The supercapacitor with a sodium-based electrolyte could operate from minus 20 to plus 40 degrees Celsius while maintaining nearly 99% cycling stability. Measurements during operation also revealed how the electrode material and electrolyte interact during charging and discharging.
The research provides a basis for developing more durable water-based energy-storage devices. Using water as the main solvent offers a route to potentially reducing the fire risks associated with flammable organic solvents. Choosing a suitable combination of electrode material, salt concentration, and additives can increase stored charge while helping the device withstand repeated use. These findings move us toward energy-storage devices that last longer and use materials more efficiently.
