Our group investigates how we can improve current energy-related devices and develop the next generation of devices, as is essential for our technology-driven lives. We explore how the atomic arrangement (crystal structure) of materials influences their physical properties.
Using chemical methods to tune the crystal structure allows us to manipulate the physical properties of materials to improve their performance for specific applications - whether it is to provide more power, better performance, or produce materials with a lower environmental cost.
This research encompasses exploratory synthesis, crystal structure determination using synchrotron X-ray and neutron scattering, physical property measurements of components and in situ structure and property characterization of functional devices.
Sodium ion battery
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Energy storage has in recent times become a critical area of research due to the widespread adoption of portable electronic devices, increasing demand for electric vehicles, and the need to store energy from renewable energy sources which are beginning to reach cost parity with fossil fuels. Lithium-ion batteries (LIBs) already appear ubiquitously in a variety of electronic devices where they are favoured for their high energy density and dependable cycling characteristics. However, volatility in lithium sourcing and pricing presents the opportunity for the development of next-generation electrochemical systems such as sodium-ion battery (NIB) or potassium-ion battery (KIB) systems, or thin-film and solid-state batteries which will act as a foundation for the development of novel microelectronic devices. Research in our group encompasses not only synthesis and characterisation of new materials, but also the implementation these new electrode and electrolyte materials into functional electrochemical devices to evaluate their performance.
Positive electrode materials
The positive electrode provides the source of ions and represent the largest cost and energy limitations for lithium-ion batteries. A number of different
Here, new sodium-containing transition metal oxides, phosphates or sulfates will be synthesized and characterized to determine the relationship between crystal structure and battery performance.
Electrolytes
Safety is an important aspect of high power batteries. Using a solid-state electrolyte has significant advantages to the highly flammable liquid electrolytes that are commercially available. Unfortunately the ionic conductivities of solid-state compounds are generally lower than the liquid counterparts, especially under ambient conditions. At the other extreme, solid oxide fuels cells often operate at approximately 1000°C as the operating temperatures are essentially determined by the ionic conductivity of the electrolyte. In both examples, electrolyte ionic conductivity is a critical hurdle in preventing further development and use of these technologies. The ionic conductivity is directly related to the crystal structures adopted by the electrolytes and how they evolve with temperature. In this project lithium-ion and oxide-ion conducting materials will be synthesized and their ionic conductivities characterized.
Negative electrode materials
Negative electrodes are the least investigated component in a sodium-ion battery and the compounds used for lithium-ion batteries show poor performance in sodium-ion batteries. By developing new negative electrodes and understanding their limitations towards reversible sodium insertion/extraction we will be enable the next generation of devices.
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Understanding the relationship between crystal structure and electrochemical performance of electrodes in a battery allows us to propose and implement changes in the rational design of materials that maximize performance. We approach this problem by directly characterizing electrode structural evolution and correlating it simultaneously to battery electrochemistry, an in situ approach. The application of crystallographic techniques to the in situ data allows us to resolve new information about reaction mechanisms, phase transitions and structural stability of the active materials during device operation.
To carry out these experiments, higher energy diffraction instruments such as the high-intensity neutron powder diffractometer WOMBAT at ANSTO and the powder X-ray diffraction beamline at the Australian Synchrotron are utilised.
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The majority of materials expand during heating via thermal expansion and this process is responsible for billions of dollars per year in maintenance, re-manufacture and replacement costs due to wear and tear on both moving parts (e.g. in aircraft gas turbines), and components that are designed to be static (e.g. in optics, coatings, electronics). If a zero thermal expansion (ZTE) material can be made, a material that neither expands nor contracts upon heating, this could dramatically reduce industrial costs. In order to achieve this, the opposite extreme of materials are considered in this project - negative thermal expansion (NTE) is a property exhibited by a small group of materials predominantly due to transverse vibrations of atom groups or cooperative rotations of units (e.g. –CN- or WO6). These materials typically feature large crystallographic voids and cations with variable oxidation states. So why not use a battery as a synthesis tool? In this project we will controllably insert Li and Na into the voids of the NTE materials, via a battery, in order to tune the cooperative rotations to produce ZTE materials.