This talk will be divided into four parts, highlighting the central role crystallography has played in my research.
First, our work exploring new oxides for low and zero thermal expansion materials will be highlighted. My team have found extremely thermally stable materials, materials with effectively a zero coefficient of thermal expansion from 4-1400 K. Undertaking variable temperature neutron diffraction (NPD) experiments on this material was terrifying – the NPD patterns did not change and my team was worried about what it could mean? Furthermore, undertaking flat-plate variable temperature X-ray diffraction (XRD) experiments proved very problematic as the sample stage expands and contracts more than our materials! We have developed a range of different compositions and now are exploring the pressure-based response of these low thermal expansion materials - do they show low/zero coefficients of thermal expansion at different pressures?
Second, our work on understanding battery materials and devices will be showcased. A large proportion of the function of batteries arises from the electrodes, and these are in turn mediated by the atomic-scale perturbations during an electrochemical process (e.g., battery use). My team uses a combination of techniques, ex situ, in situ and operando to understand how atomic scale evolution impacts performance. In particular, the operando work results in an atomic level “video” of device function which can be directly correlated to performance parameters such as energy density, lifetime (or degradation), rate capability and safety. Examples using operando neutron and synchrotron powder diffraction to probe lithium- and sodium-ion battery materials and ex situ solid-state NMR to probe lithium-sulfur battery materials will be discussed.
Third, our work in developing a new solid-state synthetic method will be described. This method is enabled by crystallographic insight and the ability to follow reactions in situ. This method involves “reacting” a material as an electrode in a battery, extracting it out and then performing thermal treatments on the electrode. This leads to the generation of news phases and in some cases modification of the physical properties of certain compositions. The talk will highlight the rich parameter space available for my team in this endeavour.
Finally, I will discuss the notion of sustainability in battery materials and processes – how green can we make the batteries of the future? Can we design battery materials to be completely sustainable? Various examples will be given in this space which will hopefully encourage further ideas and research in this space.