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Abstract
The need to develop new energy-related devices such as batteries and capacitors, for energy
storage, or solar cells, for energy generation, are essential in our lives. We will need to improve
the performance of these devices at a lower environmental and financial cost in order to enable
the transition to a sustainable energy society. The work presented in this thesis pertains to using
in situ characterisation methods in order to gain a better understanding of the chemical
reactions and crystal structure changes which occur within energy storage devices during their
operation in order to improve the performance of existing devices and also develop new highperformance materials and next generation devices. Studies were carried out primarily using
synchrotron X-ray scattering or neutron scattering to gain a comprehensive understanding of
the relationship between materials properties and device performance.
The first part of the thesis focuses on studies of lithium-ion batteries containing
commercially relevant positive electrode materials. Three studies have been carried out which
each make use of neutron diffraction to extract information about different factors which
influence cell performance: cycling history, current density and electrode composition
respectively.
The second part discusses the study of more novel electrochemical systems, including a
photoelectrochemical cell, solid-state battery and sodium-ion battery systems. The
performance and structure-electrochemistry relationships in these systems can be complex and
are not yet well understood, and these studies provide a more fundamental understanding of
how diffraction can be used to elucidate the reaction mechanisms in previously unexplored
electrochemical energy storage devices.