The scientific objective of this research program was to determine the feasibility of
manufacturing an ionic liquid-based supercapacitor that could operate at temperatures up to
220 °C. A secondary objective was to determine the compatibility of ionic liquids with other
cell components (e.g. current collectors) at high temperature and, if required, consider means
of mitigating any problems.
The industrial motivation for the present work was to develop a supercapacitor capable of
working in the harsh environment of deep offshore boreholes. If successful, this technology
would allow down-hole telemetry under conditions of mechanical vibration and high
temperature. The obstacles, however, were many. All supercapacitor components had to be
stable against thermal decomposition up to T ≥ 220 °C. Volatile components had to be
eliminated. If possible, the finished device should be able to withstand voltages greater than 4
V, in order to maximise the amount of stored energy. The internal resistance should be as low
as possible. Side reactions, particularly faradaic reactions, should be eliminated or
suppressed. All liquid components should be gelled to minimise leakage in the event of cell
damage. Finally, any emergent problems should be identified. [Continues.]
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.