Advanced materials for lithium batteries and electrochemical capacitors
thesisposted on 10.07.2014, 13:56 authored by Nooshin L. Haj Hassan
This thesis describes research carried out in the area of materials electrochemistry. The general goal was to develop and test advanced materials that might improve the performance of real-world electrochemical systems. Particular systems of interest were lithium thionyl chloride batteries, lithium sulphur batteries, and carbon-based electrochemical capacitors. Developments are reported in all three cases. Materials electrochemistry is an interdisciplinary field that investigates the relationship between the structure, properties, processing and electrochemical performance of novel materials. These may be electrodes, solutions, or combinations of both. Besides conventional electrochemical measurements, materials electrochemistry also includes elements of process development and engineering. In the present work, much effort was expended on the formulation, mixing, extrusion and curing of particulate carbon electrodes. In particular, numerous large-scale screening programs were carried out to examine the effects of multiple independent variables on battery performance. Although this required much effort to set up, the payoff was that it allowed improved processing parameters, and materials of advanced performance to be determined with a high level of confidence. Considerable effort was also expended on the development of apparatus for handling air-sensitive battery solvents, such as thionyl chloride. Amongst the achievements of the present work are: (i) the successful reformulation of the manufacturing solvent for commercial lithium battery electrodes, to halve the quantity of isopropyl alcohol used. In the future this will allow the manufacturing process to continue within UKIEU regulations. (ii) The improvement of the mechanical strength and electrochemical capacity of thick-film carbon electrodes by adding conducting carbon fibre. (iii) The development of an easy-to-implement test that accurately predicts the performance of lithium thionyl chloride battery electrodes. (iv) The development of a novel electrolyte solution for lithium sulphur batteries (using a sulfolane/ethylene carbonate mixture). (v) The discovery that this solution can be gelled with PVDF, and finally (vi) the discovery that some carbon blacks out-perform activated carbon in thick-film electrodes for electrochemical capacitors.